polymers

Article Durability and Electrical Conductivity of Carbon Fiber Cloth/Ethylene Propylene Diene Monomer Rubber Composite for Active Deicing and Snow Melting

Shuanye Han , Haibin Wei *, Leilei Han and Qinglin Li College of Transportation, Jilin University, Changchun 130025, China; [email protected] (S.H.); [email protected] (L.H.); [email protected] (Q.L.) * Correspondence: [email protected]



Received: 8 November 2019; Accepted: 6 December 2019; Published: 10 December 2019


Abstract: To reduce the impact of road ice and snow disaster, it is necessary to adopt low energy consumption and efficient active deicing and snow melting methods. In this article, three functional components are combined into a conductive ethylene propylene diene monomer (EPDM) rubber composite material with good interface bonding. Among them, the mechanical and electrical properties of the composite material are enhanced by using carbon fiber cloth as a heating layer. EPDM rubber plays a mainly protective role. Further, aluminum silicate fiber cloth is used as a thermal insulation layer. The mechanical properties of EPDM rubber composites reinforced by carbon fiber cloth and the thermal behaviors of the composite material in high and low temperature environments were studied. The heat generation and heat transfer effect of the composite were analyzed by electrothermal tests. The results show that the conductive EPDM rubber composite material has good temperature durability, outstanding mechanical stability, and excellent heat production capacity. The feasibility of the material for road active deicing and snow melting is verified. It is a kind of electric heating deicing material with broad application prospects.

Keywords: thermal behavior; multifunctional composites; mechanical properties; electrothermal properties; active deicing and snow melting; temperature durability

1. Introduction In most parts of the world, road ice and snow problems occur in winter, and various methods are adopted for snow melting and deicing, but the results are unsatisfactory. Every year, a large number of traffic accidents are caused by snow and ice disasters. At present, artificial and mechanical salt spraying are the main measures to protect against road icing. Various salt chemicals such as NaCl, MgCl2 [1] and potassium acetate [2] are used on the road. The method of salt spraying can melt snow and ice at the beginning of use. However, most of the salts used contain chloride ions, which have serious corrosive effects on steel [3] and concrete [4,5] in road infrastructure. Simultaneously, salt chemicals have a serious impact on the ecological environment around the road and groundwater [6–8]. In view of the problems of chemical deicing, to achieve the purpose of rapid and effective road deicing and snow melting that will not affect the ecological environment around the road, scholars have developed active snow and ice removal technologies. Existing active deicing and snow melting technologies mainly include the conductive asphalt mixture method, heat pipe method, geothermal energy deicing method, and the electric heating method. The conductive asphalt mixture method mainly adds conductive fillers such as steel fiber [9], steel slag [10], graphite and carbon fiber [11,12] to the asphalt mixture. In this way, the purpose

Polymers 2019, 11, 2051; doi:10.3390/polym11122051 www.mdpi.com/journal/polymers Polymers 2019, 11, 2051 2 of 17 of reducing the electric resistance of the asphalt mixture is achieved. Then, the conductive asphalt concrete is heated by electric current or infrared heating [13,14], thereby realizing active deicing of the road. However, the mechanical properties of asphalt mixtures decrease due to the addition of conductive fillers. In addition, the electrical resistance value of the asphalt mixture with conductive filler is greater than that of conductive filler, resulting in low thermal efficiency. A faster heating rate can only be achieved when the input power is relatively large. This method takes a long time to achieve road snow melting and deicing, resulting in serious energy waste and a high cost of use. Heat pipe technology realizes the active snow melting and deicing of the road by embedding pipes in the road structure and introducing a heat flow into the pipes. Chen et al. [15] conducted a snowmelt test after laying heat pipes on the airport runway. The results proved that the heat pipe technology can achieve snow melting and deicing, which provided certain support for the actual construction design. Liu et al. [16] studied the effects of various factors such as wind speed, heating power, and buried spacing on the melting of electric heating tubes. However, pipeline laying had a certain impact on the structural layer of the road. There were high requirements for heat flow control and road construction during use. Geothermal energy is a clean energy source. Han et al. [17,18] controlled the geothermal heat pump system and the thermoelectric system to study the use of geothermal heat to achieve snow melting and the deicing of roads. Due to the limitation of geothermal energy and the low efficiency of thermoelectric conversion, it was impossible to melt snow in real time. Because the above active deicing methods have some defects, they have not been widely used. Conductive composite materials have developed rapidly in recent years, so the application of conductive composite materials on roads is considered. Active road deicing and snow removal can be realized by power on. In order to achieve efficient and fast road deicing and snow melting, the effective reduction of resistance value has been proven to be one of the key ways to improve electrical heating performance [19,20]. Carbon series materials have good electrical conductivity. Therefore, Chu et al. applied materials with excellent conductivity such as carbon nanotubes [21] and graphene-paper [22,23] to deicing applications. The effect of actual deicing is obvious, but materials such as carbon nanotubes and graphene are expensive. Currently, coverage of the large areas occupied by roads is not easy to achieve. In comparison, carbon fiber cloth is a material that has developed rapidly in recent years. The cost of carbon fiber cloth has been greatly reduced due to the improvement of carbon fiber preparation technology. Since carbon fiber cloth has the characteristics of low resistance and good durability, it has been studied in the preparation of electrodes [24] and in 3D printing heating materials [25]. Furthermore, the mechanical strength of carbon fiber cloth is high. It has been widely used in the mechanical properties of reinforced composite materials [26] and the reinforcement of bridges [27]. In view of the excellent mechanical and electrothermal properties of carbon fiber cloth, Lim et al. [28–31] added carbon fiber cloth directly to the concrete, and then heated concrete by electricity. The heat production rate of the carbon fiber cloth and the effect of ambient temperature on heat production efficiency were investigated. The results showed that the carbon fiber cloth can quickly heat up when the input power is small, and achieve the purpose of rapid deicing and snow melting. Previous studies proved that carbon fiber cloth has broad application prospects in road deicing and snow removal. However, the protection of carbon fiber cloth and the durability of carbon fiber cloth composite material were not considered. In this paper, a conductive ethylene propylene diene monomer (EPDM) rubber composite material with a three-layer structure was prepared using carbon fiber cloth as heat producing layer and sandwiched between a heat conducting layer of EPDM rubber and heat insulating layer of aluminum silicate fiber cloth. The effects of carbon fiber cloth on the mechanical and electrical properties of EPDM rubber were investigated. Combined with the environment in which the composite material was used on the road, the thermal behaviors of the composite material under a high temperature 60 ◦C environment and the durability of the material after cycling at 20 C and normal temperature were − ◦ analyzed. The heat generation uniformity and heat production effect of the composite material were studied. The results showed that the conductive composite material based on carbon fiber cloth has Polymers 2019, 11, 2051 3 of 17 the characteristics of high efficiency, reliability, durability, high mechanical strength and low cost in deicing and snow melting. It is a potential electric heating deicing material in many fields.

2. Materials and Methods

2.1. Materials Carbon fiber cloth used in this study was purchased from Shanghai Yuezi Industrial Co., LTD (Shanghai, China). The carbon fiber cloth is woven from 12 K carbon fiber precursors, with a carbon content of more than 98%, a thickness of 0.167 mm and a density of 300 g/cm3. Because of the good electrical conductivity of carbon fiber cloth, it was used as an electrical heating layer. Ethylene propylene diene monomer (EPDM) rubber (Sanhe Great Wall Rubber Co., LTD., Sanhe, China) with a density of 0.90 g/cm3 was used as a protective and bonding material for carbon fiber cloth. To transfer heat rapidly, graphite (Tianjin Dengke Chemical Co., LTD., Tianjin, China) with high thermal conductivity was added to EPDM rubber. The carbon content of graphite is more than 99.93% and the particle diameter is 6.5 µm. The addition of carbon black with a particle size of 40 nm and auxiliary materials (Kaiyin Chemical Co., LTD., Kaiyin, China) such as vulcanizing agent dicumyl peroxide to EPDM rubber improve the mechanical properties and durability of the composite material. The obtained thermally conductive EPDM rubber composite material was used as a heat transfer layer. The heat insulation layer was composed of aluminum silicate fiber cloth (Dacheng North Sealing Products Factory, Dacheng, China) with a low thermal conductivity of 0.035 W/(m K) and EPDM rubber. Finally, · the three-layer structure was vulcanized at high temperature and high pressure to obtain a conductive EPDM rubber composite material.

2.2. Preparations of Conductive EPDM Rubber Composite Material The conductive EPDM rubber composite material is composed of a heat transfer layer, a heat generating layer and a heat insulating layer from top to bottom. First, a thermally conductive rubber compound was prepared. EPDM rubber, graphite, carbon black and vulcanizing agent were mixed at a weight ratio of 10:4:4:0.2, and placed in an open mill (Qingdao Shunfu Rubber Machinery Manufacturing Co., LTD., Qingdao, China) at room temperature. Mixed for 30 min to distribute the fillers evenly in the rubber. To simplify the process, the obtained rubber compound was used as a binder for the carbon fiber cloth and the heat insulating layer aluminum silicate fiber cloth. Second, the mixture was left at room temperature for 30 min while the press vulcanizer was preheated and two kinds of fiber cloth and steel molds were prepared. Then, an aluminum silicate fiber cloth, a rubber compound, a carbon fiber cloth, and a rubber compound were placed in this order from bottom to top in the steel mold. The steel mold was placed in the press vulcanizing machine which provided a high temperature and high pressure environment of 170 ◦C and 10 MPa. Finally, the conductive EPDM rubber composite material was obtained by vulcanization for about 10 min. The density of conductive EPDM composites is 1.25 g/cm3. The electrothermal sample size was 1000 500 6.5 mm3. Mechanical test specimens × × were prepared according to the corresponding test requirements. The sample preparation process is shown in Figure1. Polymers 2019, 11, x FOR PEER REVIEW 4 of 17 Polymers 2019, 11, 2051 4 of 17

Figure 1. Sample preparation process.

2.3. Measurements Figure 1. Sample preparation process.

2.3. MeasurementsIn order to determine the feasibility of conductive EPDM rubber composite material for road deicing and long-term use in roads, mechanical properties, and electrothermal properties of the compositeIn order material to determine were measured. the feasibility of conductive EPDM rubber composite material for road deicing and long-term use in roads, mechanical properties, and electrothermal properties of the 2.3.1.composite Mechanical material Properties were measured. Tests The influence of carbon fiber cloth on mechanical properties (tensile strength, tear strength and 2.3.1. Mechanical Properties Tests compressive strength) of EPDM rubber composite material was determined by an electronic universal testingThe machine influence (Metis of carbon Test Machine fiber cloth Factory, on mechanical Tianjin, China). properties The (tensile effects ofstrength, carbon tear fiber strength cloth on and the mechanicalcompressive properties strength) of EPDM of EPDM rubber rubber composite composite material material were determined was determined by mechanical by an experiments. electronic Theuniversal mechanical testing propertiesmachine (Metis of the Test composite Machine were Factory, measured Tianjin, according China). toThe the effects methods of carbon [32–34 fiber] for measuringcloth on the the mechanical mechanical properties of of hot EPDM vulcanized rubber rubber composite composite material material. were The determined tensile tests by weremechanical performed experiments. using dumbbell-shaped The mechanical tensileproperties test specimens,of the composite and the were test measured area of the according sample was to 20the methods5 6.5 mm [323–.34 The] for non-experimental measuring the zonemechanical of the sample properties was clampedof hot vulcanized in the chuck rubber of the composite electronic × × universalmaterial. The testing tensile machine, tests were and performed the moving using speed dumbbell was adjusted-shaped to tensile 50 mm test/min. specimens The sample, and andthe test the post-testarea of the sample sample are was shown 20 in× Figure5 × 6.52 mm. The³. tearThe testsnon- wereexperimental carried out zone using of trouserthe sample samples, was theclamped moving in speedthe chuck of the of chuck the electronic was 100 universal mm/min, testing and the machine, size of the and tear the test moving sample speed was was100 adjusted15 6.5 mmto 503. × × Themm/min. samples The used sample for and the the compression post-test sample tests were are shown circular in samples Figure 2. of TheΦ 29 tear 6.5tests mm were. The carried samples out × wereusing compressedtrouser samples at a, speedthe moving of 10 mmspeed/min. of the This chuck test was was 100 cycled mm/min four,times, and theand size the ofresult the tear of test the fourthsample compression was 100 ×15 test× 6.5 was mm recorded.³. The samples The thicknessused for the of allcompression the tested samplestests were was circular 6.5 mm, samplesand the of force-displacementΦ 29 × 6.5 mm. The curvessamples during were compressed the mechanical at a testsspeed were of 10 obtained mm/min. by This the test electronic was cycled universal four testingtimes, and machine. the result of the fourth compression test was recorded. The thickness of all the tested samples was 6.5 mm, and the force-displacement curves during the mechanical tests were obtained by the electronic universal testing machine.

Polymers 2019, 11, 2051 5 of 17 Polymers 2019, 11, x FOR PEER REVIEW 5 of 17

Figure 2. Tensile test specimens and post-test specimens. Figure 2. Tensile test specimens and post-test specimens. 2.3.2. High Temperature Durability Tests 2.3.2. High Temperature Durability Tests Since the conductive EPDM rubber composite material was used in roads, durability studies were conductedSince t basedhe conductive on the most EPDM unfavorable rubber composite conditions ofmaterial road temperature. was used in According roads, durability to data from studies the werenational conducted meteorological based on information the most centerunfavorable of China, conditions the highest of road temperaturetemperature. in According summer is to around data from60 C, the and national the average meteorological temperature ininformation winter is around center of20 China,C in Northeast the highest China. road Temperature temperature has in a ◦ − ◦ summergreat impact is around on the 60 durability °C , and the and average service temperature life of the material. in winter Therefore, is around the −20 samples °C in N wereortheast placed China. in a Temperatureblast oven (Sanshui has a Scientific great impact Instrument on the Co., durability LTD., Tianjin, and service China). life The of highthe material. temperature Therefore, aging tests the samples were placed in a blast oven (Sanshui Scientific Instrument Co., LTD., Tianjin, China). The were carried out at a high temperature of 60 ◦C for 24, 48, 72, 96, and 120 h. The changes of tensile highstrength, temperature tear strength, aging andtests compressive were carried strength out at a ofhigh the temperature material at diofff erent60 °C timesfor 24, were 48, 72, measured. 96, and Three120 h. parallel The changes tests were of tensile performed strength, for each tear test strength and test, and errors compressive were indicated strength by errorof the bars. material at different times were measured. Three parallel tests were performed for each test and test errors were indicated2.3.3. Low by Temperature error bars. Cycle Tests The samples were placed in a refrigerator at 20 C for low temperature cycle tests. After 2.3.3. Low Temperature Cycle Tests − ◦ 24 h of freezing, the samples were taken out and thawed at room temperature of 26 ◦C for 24 h, and thisThe wassamples repeated were 20 placed times. in Part a refrigerator of the samples at −20 were °C for taken low out temperature for mechanical cycletests tests. every After 5 24 cycles. h of Thefreezing, tensile the, tear samples and compressive were taken out properties and thawed of the at conductive room temperature EPDM rubber of 26 °C composite for 24 h, material and this afterwas repeatedlow temperature 20 times. cyclic Part of treatment the samples were were evaluated taken byout the for electronic mechanical universal tests every testing 5 cycles. machine. The tensile, tear and compressive properties of the conductive EPDM rubber composite material after low temperature2.3.4. Heat Production cyclic treatment Uniformity were Testsevaluated by the electronic universal testing machine. As shown in Figure3b, copper electrodes (Figure3a) with the size of 500 10 1.5 mm3 and the × × 2.3.4.carbon Heat fiber Production cloth are fixed Uniformity using clips.Tests The addition of the copper electrodes can effectively reduce the contactAs shown resistance in Figure and 3b, achieve copper a elec uniformtrodes distribution (Figure 3a) of with voltage. the size In orderof 500 to × test10 × the1.5 uniformmm³ and heat the productioncarbon fiber of cloth carbon are fiberfixed cloth using in clips. circuit. The As addition shown in of Figure the copper3c, the electrodes temperature can sensorseffectively (Changsha reduce theSanzhi contact Electronic resistance Technology and achieve Co., a uniform LTD., Changsha, distribution China) of voltage. 1, 2 and In order 3 were to placed test the in uniform the middle, heat productionthe middle of thecarbon edge fiber and cloth the cornerin circuit. portion As shown of the in sample, Figure respectively.3c, the temperature The temperature sensors (Changsha changes Sanzhiof the three Electronic temperature Technology sensors Co., were LTD., measured. Changsha The, China) connection 1, 2 and of 3the were circuit placed is shownin the middle, in Figure the4. Themiddle power of the supply edge wasand convertedthe corner from portion AC of 220 the V sample, to low voltage respectively. by means The of temperature a transformer, changes and the of thesample three size temperature used in the sensors tests was were 1000 measured.500 6.5The mm connection3. Electrothermal of the circuit tests is were shown carried in Figure out at 4. room The × × powertemperature supply without was converted thermal insulation from AC measures 220 V to and low the voltage effects byof wind. means By of inputting a transformer, different and power, the samplethe change size ofused temperature in the tests with was the 1000 time × 500 of electrification× 6.5 mm³. Electrothermal is recorded. Thereby,tests were the carried uniformity out at ofroom the temperatureconductive EPDM without rubber thermal composite insulation material measures was determined. and the effects of wind. By inputting different power, the change of temperature with the time of electrification is recorded. Thereby, the uniformity of the conductive EPDM rubber composite material was determined.

Polymers 2019,, 11,, 2051x FOR PEER REVIEW 6 of 17 Polymers 2019, 11, x FOR PEER REVIEW 6 of 17

Figure 3. (a) Copper electrodes; (b) installation position of copper electrode; (c) distribution position Figure 3. (a) CopperCopper electrodes;electrodes; ( b(b) installation) installation position position of of copper copper electrode; electrode; (c) 1,2(c) anddistribution 3 are temperature position of temperature sensors. ofsensors temperature and their sensors. distribution positions.

Figure 4. CircCircuituit connection and electrical components. Figure 4. Circuit connection and electrical components. 2.3.5. Resistance Stability and Thermal Efficiency Tests 2.3.5. Resistance Stability and Thermal Efficiency Tests 2.3.5. Resistance Stability and Thermal Efficiency Tests Through electrothermal tests, the change of current and voltage in the circuit is measured. Through electrothermal tests, the change of current and voltage in the circuit is measured. The The resistanceThrough electrothermalvalue of the composite tests, the material change of after current multiple and inputvoltage of diinff theerent circuit power is measured. was calculated The resistance value of the composite material after multiple input of different power was calculated to resistanceto analyze value the resistance of the composite stability material of the composite after multiple material. input Temperature of different power sensors was were calculated placed onto analyze the resistance stability of the composite material. Temperature sensors were placed on the analyzethe upper the and resistance lower layers stability of the of materialthe composite to measure material. the changeTemperature rate of sensors temperature were afterplaced inputting on the upper and lower layers of the material to measure the change rate of temperature after inputting upperdifferent and power. lower Thus, layers the of thermalthe material efficiency to measure of the composite the change and rate the of function temperature of thermal after insulationinputting different power. Thus, the thermal efficiency of the composite and the function of thermal insulation differentlayer were power. analyzed. Thus, the thermal efficiency of the composite and the function of thermal insulation layer were analyzed. layer were analyzed. 3. Results and Discussion 3. Results and Discussion 3. Results and Discussion 3.1. Effect of Carbon Fiber Cloth on Mechanical Properties of EPDM Rubber Composite 3.1. Effect of Carbon Fiber Cloth on Mechanical Properties of EPDM Rubber Composite 3.1. EffectFigure of 5C combinesarbon Fiber two Cloth typical on Mechanical force-displacement Properties of curves EPDM of R EPDMubber Composite rubber composite materials Figure 5 combines two typical force-displacement curves of EPDM rubber composite materials withFigure and without 5 combines carbon two fiber typical cloth inforce one-displac coordinateement system. curves As of shown EPDM in rubber Figure composite5, the EPDM materials rubber with and without carbon fiber cloth in one coordinate system. As shown in Figure 5, the EPDM rubber withcomposite and without materials carbon have fiber typically cloth threein one stages coordinate of elasticity, system. yield, As shown and strain in Figure hardening 5, the EPDM in the processrubber composite materials have typically three stages of elasticity, yield, and strain hardening in the process compositeof stretching. materials Further, have the typically influence three of carbonstages of fiber elasticity, cloth on yield the, and three strain stages hardening is different. in the After process the of stretching. Further, the influence of carbon fiber cloth on the three stages is different. After the of stretching. Further, the influence of carbon fiber cloth on the three stages is different. After the addition of the carbon fiber cloth, the corresponding maximum value of the composite material in addition of the carbon fiber cloth, the corresponding maximum value of the composite material in the elastic phase increases. According to the formula: the elastic phase increases. According to the formula:

Polymers 2019, 11, x FOR PEER REVIEW 7 of 17

퐹푚 푇푆 = (1) 푊푑 where TS is the tensile strength (MPa), Fm is the maximum force recorded (N), W is the width of the test area (mm), and d is the thickness of the test area (mm). The Fm increases after the carbon fiber cloth is added, so the tensile strength is remarkably improved. However, carbon fiber cloth breaks when the tensile force reaches the maximum value, so the force falls quickly and it has less influence in subsequent stages. After that, the conductive EPDM rubber composite material shows a yielding phenomenon. The yield force of the composite material with carbon fiber cloth is slightly higher than the composite material without carbon fiber cloth. In Polymers 11 the strain2019 hardening, , 2051 stage, the carbon fiber cloth in the composite material breaks. Therefore,7 ofthe 17 composite material with carbon fiber cloth overlaps with the tensile curve of the composite material withoutaddition carbon of the carbon fiber cloth. fiber cloth,According the corresponding to Figure 6, maximumthe change value trend of of the the composite two tear materialtest curves in the is similar,elastic phase but the increases. maximum According values of to the the tear formula: process force are different. The tearing force value of the added carbon fiber cloth is larger than that of the composite material without the carbon fiber cloth. F Because the tear sample size is the same, it canTS be= concludedm that the addition of carbon fiber cloth(1) can increase the tear strength of the composite material.Wd According to Table 1, it can be concluded that the addition of carbon fiber cloth increases the tensile strength of the composite by 78.3% and where TS is the tensile strength (MPa), Fm is the maximum force recorded (N), W is the width of the thetest tear area streng (mm),th and by d23.1%, is the but thickness the addition of the testof carbon area (mm). fiber cloth increases the compressive strength of the EPDM rubber composite by only 0.5%.

Figure 5. ForceForce-displacement-displacement curves (left) (left) and and Stress Stress-strain-strain curves of tensile tests (right) (right)..

The Fm increases after the carbon fiber cloth is added, so the tensile strength is remarkably improved. However, carbon fiber cloth breaks when the tensile force reaches the maximum value, so the force falls quickly and it has less influence in subsequent stages. After that, the conductive EPDM rubber composite material shows a yielding phenomenon. The yield force of the composite material with carbon fiber cloth is slightly higher than the composite material without carbon fiber cloth. In the strain hardening stage, the carbon fiber cloth in the composite material breaks. Therefore, the composite material with carbon fiber cloth overlaps with the tensile curve of the composite material without carbon fiber cloth. According to Figure6, the change trend of the two tear test curves is similar, but the maximum values of the tear process force are different. The tearing force value of the added carbon fiber cloth is larger than that of the composite material without the carbon fiber cloth. Because the tear sample size is the same, it can be concluded that the addition of carbon fiber cloth can increase the tear strength of the composite material. According to Table1, it can be concluded that the addition of carbon fiber cloth increases the tensile strength of the composite by 78.3% and the tear strength by 23.1%, but the addition of carbon fiber cloth increases the compressive strength of the EPDM rubber composite by only 0.5%.

Table 1. Effect of carbon fiber cloth on mechanical properties of composite material.

Tensile Tear Compressive Figure 6. Force-displacemeStrength/(MPa)nt curves ofStrength tear tests./(KN /m) Strength/(MPa) Without Carbon Experiment 3.70 3.52 3.63 13.43 13.57 13.26 3.87 3.84 3.84 Fiber Cloth Average Standard ± 3.61 0.075 13.42 0.127 3.85 0.014 Deviation ± ± ± Existing Carbon Experiment 6.30 6.58 6.44 17.04 16.61 15.91 3.88 3.85 3.89 Fiber Cloth Average Standard ± 6.44 0.114 16.52 0.466 3.87 0.017 Deviation ± ± ± Polymers 2019, 11, x FOR PEER REVIEW 7 of 17

퐹푚 푇푆 = (1) 푊푑 where TS is the tensile strength (MPa), Fm is the maximum force recorded (N), W is the width of the test area (mm), and d is the thickness of the test area (mm). The Fm increases after the carbon fiber cloth is added, so the tensile strength is remarkably improved. However, carbon fiber cloth breaks when the tensile force reaches the maximum value, so the force falls quickly and it has less influence in subsequent stages. After that, the conductive EPDM rubber composite material shows a yielding phenomenon. The yield force of the composite material with carbon fiber cloth is slightly higher than the composite material without carbon fiber cloth. In the strain hardening stage, the carbon fiber cloth in the composite material breaks. Therefore, the composite material with carbon fiber cloth overlaps with the tensile curve of the composite material without carbon fiber cloth. According to Figure 6, the change trend of the two tear test curves is similar, but the maximum values of the tear process force are different. The tearing force value of the added carbon fiber cloth is larger than that of the composite material without the carbon fiber cloth. Because the tear sample size is the same, it can be concluded that the addition of carbon fiber cloth can increase the tear strength of the composite material. According to Table 1, it can be concluded that the addition of carbon fiber cloth increases the tensile strength of the composite by 78.3% and the tear strength by 23.1%, but the addition of carbon fiber cloth increases the compressive strength of the EPDM rubber composite by only 0.5%.

Polymers 2019, 11, 2051 8 of 17 Figure 5. Force-displacement curves (left) and Stress-strain curves of tensile tests (right).

Figure 6. Force-displacement curves of tear tests. Figure 6. Force-displacement curves of tear tests.

Since the mechanical strength of the carbon fiber cloth in the fiber direction is high, the tensile strength and the tear strength of the composite material are relatively large. However, the compression tests were perpendicular to the plane in which the carbon fiber cloth was laid, and the fibers were only subjected to the compressive force during the compression process. And the thickness of carbon fiber cloth is only 0.167 mm. As a result, the compressive strength of the composite material was mainly provided by the EPDM rubber. The carbon fiber cloth had substantially no effect on the compressive strength of the EPDM rubber composite material. In summary, the addition of carbon fiber cloth has greatly improved the tensile strength and tear strength of the conductive EPDM composite material. The application of the conductive EPDM rubber composite material on the road is guaranteed.

3.2. Durability of Conductive EPDM Rubber Composite Material at 60 ◦C It can be clearly seen from Figure7 that after the high temperature treatment, the maximum value of the force during the stretching process increases, thus the tensile strength of the composite material increases. However, the yield point of the composite treated at 48 h is lower than that of the composite material without high temperature treatment. The strain hardening stage is also lower than that of untreated samples. Figure8 is the e ffect of high temperature duration on the tensile strength of the composite material. Curve fitting was performed on the data obtained from the tensile tests, and the exponential function was obtained by fitting:

x y = 2.596e− 42.364 + 9.279 (2) − where x is the heating time (h) and y is the tensile strength (MPa). The correlation coefficient is 0.9858. According to the characteristics of the exponential function, the mechanical properties of the material under long-term high temperature environment can be predicted appropriately. Further, the tensile strength of the composite material tends to stabilize gradually. With respect to Table2 and Figure9, the tensile strength, tear strength and compressive strength of the composite material are significantly improved after high temperature treatment for 72 h, which increase by 38.04%, 8.78%, and 33.85%, respectively. The tensile strength, tear strength and compressive strength after 120 h high temperature treatment increase by 2.70%, 0.11% and 1.95%, respectively, compared with 72 h. The mechanical properties do not change substantially, and tend to be stable. Polymers 2019, 11, x FOR PEER REVIEW 9 of 17 Polymers 2019, 11, 2051 9 of 17 Polymers 2019, 11, x FOR PEER REVIEW 9 of 17

Figure 7. Effect of high temperature on tensile curves of conductive ethylene propylene diene Figure 7. Effect of high temperature on tensile curves of conductive ethylene propylene diene monomer Figuremonomer 7. Effect(EPDM) of rubber high temperature composite. on tensile curves of conductive ethylene propylene diene (EPDM) rubber composite. monomer (EPDM) rubber composite.

Figure 8. Effect of high temperature duration on tensile strength of conductive EPDM rubber composite Figure 8. Effect of high temperature duration on tensile strength of conductive EPDM rubber and curve fitting. Figurecomposite 8. Effect and curve of high fitting. temperature duration on tensile strength of conductive EPDM rubber compositeTable and2. curveEffect fitting. of high temperature heating time on mechanical properties of material.

Heating Time/h 0 24 48 72 96 120 Tensile Strength/(MPa) 6.44 7.91 8.44 8.89 9.07 9.13 Tear Strength/(KN/m) 16.52 17.04 17.62 17.97 17.99 17.99 Compressive Strength/(MPa) 3.84 4.61 4.85 5.14 5.22 5.24

Polymers 2019, 11, 2051 10 of 17 Polymers 2019, 11, x FOR PEER REVIEW 10 of 17

Figure 9. ThThee effect effect of high high temperature on ( a) tear strength; (b) compressive strength. After 120 h of continuous high temperature treatment, the mechanical properties of the conductive Table 2. Effect of high temperature heating time on mechanical properties of material. EPDM rubber composite material have been improved. The reason why the composite material was greatly improvedHeating before Time/h 72 h was that no secondary0 high24 temperature48 vulcanization72 96 was performed120 during theTensile preparation Strength/(MPa) of the samples. The6.44 residual 7.91 vulcanizing 8.44 agent 8.89 and other9.07 materials 9.13 in the compositeTear did not Strength/(KN/m) react adequately [35]. The16.52 reaction rate17.04 of the17.62 residual material17.97 was17.99 accelerated 17.99 in a 60 ◦C environment,Compressive resulting Strength/(MPa) in a rapid increase3.84in mechanical4.61 properties.4.85 5.14 But the5.22 breaking 5.24 strength of the composite material decreased. After 72 h, the residual material was substantially completely reacted.After The 120 subsequent h of continuous high temperature high temperature treatment treatment, had little e theffect mechanical on the mechanical properties properties of the ofconductive conductive EPDM EPDM rubber rubber composite composite material material. have Because been impro the heatingved. The temperature reason why is the relatively composite low andmaterial the high was temperaturegreatly improved aging before resistance 72 h of was EPDM that rubberno secondary is good high [36], theretemperature is no phenomenon vulcanization in whichwas performed the performance during of the the preparation rubber composite of the materialsamples.is The degraded. residual It vulcanizing is less likely agentthat special and other high temperaturesmaterials in the will composite occur on roads, did no andt react the durationadequately will [35 not]. beThe long. reaction It is proven rate of that the conductiveresidual material EPDM rubberwas accelerated composite in material a 60 °C hasenvironment, good durability resulting and in can a berapid used increase in road in for mechanical a long time. properties. But the breaking strength of the composite material decreased. After 72 h, the residual material was 3.3.substantially Mechanical completely Properties Afterreacted. Low The Temperature subsequent Cycling high temperature treatment had little effect on the mechanicalAccording properties to Figure of 10 , conductive as the number EPDM of low rubber temperature composite cycles material. increases, Because the tensile the strength, heating teartemperatur strength,e is and relatively compressive low and strength the high curves temperature of the conductive aging resistance EPDM of rubberEPDM compositerubber is good material [36], changethere is little,no phenomenon and there is noin which significant the performance downward or of upward the rubber trend. composite The test datamaterial in Table is degraded.3 show that It theis less tensile likely strength, that special the tear high strength temperatures and the will compressive occur on roads, strength and fluctuatethe duration around will thenot averagebe long. ofIt 6.42is prove MPa,n that 16.51 conductive KN/m and EPDM 3.70 MPa, rubber respectively. compositeCompared material has with good the durability mean values, and thecan fluctuationbe used in valuesroad for are a long 0.47%, time. 0.61% and 3.78%, respectively. The range of curve fluctuations is between the test error bars of the parallel tests. The small fluctuations can prove that the mechanical properties of the composite3.3. Mechanical material Properties are relatively After Low stable, Temperature and there Cycling is no large performance degradation phenomenon withAccording multiple low to Figure temperature 10, as the cycles. number The of test low data temperature and curve cycles show increases, that the the composite tensile strength, material hastear goodstrength low-temperature, and compressive durability, strength and curves the mechanical of the conductive properties EPDM do not rubber change composite greatly withmaterial the increasechange little, of the and number there of is lowno significant temperature downward cycles times. or upward This proves trend. that The the test conductive data in EPDMTable 3 rubber show compositethat the tensile material strength, has good the tear low strength temperature and the durability compressive and can strength be used fluctuate for a long around time t inhe theaverage road environmentof 6.42 MPa, 16.51 with KN/m a large and temperature 3.70 MPa, di respectively.fference. Compared with the mean values, the fluctuation values are 0.47%, 0.61% and 3.78%, respectively. The range of curve fluctuations is between the test error bars of the parallel tests. The small fluctuations can prove that the mechanical properties of the composite material are relatively stable, and there is no large performance degradation phenomenon with multiple low temperature cycles. The test data and curve show that the composite material has good low-temperature durability, and the mechanical properties do not change greatly with the increase of the number of low temperature cycles times. This proves that the conductive EPDM rubber composite material has good low temperature durability and can be used for a long time in the road environment with a large temperature difference. Polymers 2019, 11, 2051 11 of 17 Polymers 2019, 11, x FOR PEER REVIEW 11 of 17

Figure 10. Effect of low temperature cycle times on (a) tensile strength; (b) tear strength; (c) compressive Figure 10. Effect of low temperature cycle times on (a) tensile strength; (b) tear strength; (c) strength of conductive EPDM rubber composite. compressive strength of conductive EPDM rubber composite. Table 3. Effect of low temperature cycling on mechanical properties of the material. Table 3. Effect of low temperature cycling on mechanical properties of the material. Number of Cryogenic Cycles 0 5 10 15 20 NumberTensile of Strength Cryogenic/(MPa) Cycles 6.440 6.435 6.3910 6.3715 6.45 20 TensileTear Strength Strength/(MPa)/(KN/m) 16.526.44 16.486.43 16.356.39 16.616.37 16.59 6.45 CompressiveTear Strength/(KN/m) Strength/(MPa) 3.8416.52 3.6016.48 3.8216.35 3.5216.61 3.73 16.59 Compressive Strength/(MPa) 3.84 3.60 3.82 3.52 3.73 3.4. Heat Production Uniformity of Conductive EPDM Rubber Composite Material 3.4. Heat Production Uniformity of Conductive EPDM Rubber Composite Material Conductive EPDM rubber composite material is designed to quickly solve road ice and snow disasters.Conductive The heat EPDM generation rubber uniformity, composite resistancematerial is stability, designed and to heat quickly generation solve road effects ice of and diff snowerent inputdisasters. power The need heat togeneration be analyzed uniformity, before theresistance actual snowstability, melting and heat test. generation In this way, effects it is possibleof different to ensureinput power the safe need and to effi becient analyzed operation before of the the conductive actual snow EPDM melting rubber test. composite In this way, material it is inpossible the road. to ensureFigure the 11safe shows and efficient the temperature operation change of the of conductive the upper layer EPDM of the rubber sample composite at different material input powerin the forroad. the temperature sensors at three locations. Meanwhile, a control temperature sensor was placed at roomFigure temperature 11 shows to determine the temperature the variation change of roomof the temperature. upper layer Due of the to sampleinstrumental at different errors ininput the temperaturepower for the sensors, temperature there aresensors differences at three in locations. the initial Meanwhile, temperatures a ofcontrol the three temperature temperature sensor sensors. was Asplaced can beat seenroom in temperature Figure 11, the to threedetermine temperature the variation sensors of have room the temperature. same rising Due speed, to andinstrum the threeental curveserrors arein the parallel. temperature According sensors, to Table there4, after are 30 differences min of energization, in the initial the threetemperatures temperature of the sensors three showtemperature that the sensors. temperature As can changes be seen in in the Figure upper 11, layer the ofthree the temperature sample are consistent. sensors have There the is same no change rising inspeed, room and temperature, the three curves so the riseare ofparallel. the sample According temperature to Table is entirely4, after 30 due min to theof energization, heat generated the by three the conductivetemperature EPDM sensors rubber show composite that the material temperature after energization. changes in The the temperature upper layerchange of the values sample at the are threeconsistent. locations There after is no multiple change tests in room are the temperature, same, indicating so the that rise theof the heat sample production temperature of the conductive is entirely due to the heat generated by the conductive EPDM rubber composite material after energization. The temperature change values at the three locations after multiple tests are the same, indicating that the

Polymers 20192019,, 1111,, 2051x FOR PEER REVIEW 12 of 17

heat production of the conductive EPDM rubber composite material is uniform. This ensures that the EPDMmaterials rubber produce composite consistent material heat isthroughout uniform. Thisthe road, ensures and that can the achieve materials comprehensive produce consistent deicing heatand throughoutsnow melting. the road, and can achieve comprehensive deicing and snow melting.

Figure 11. Different input power (a) 80 W/m2;(b) 160 W/m2;(c)320 W/m2, the temperature of the three positionsFigure 11. with Different the power-on input power time. (a) 80 W/m²; (b) 160 W/m²; (c)320 W/m², the temperature of the three positions with the power-on time. Table 4. Upper layer temperature of the sample after 30 min of energization. Table 4. Upper layer temperature of the sample after 30 min of energization. Input Power/(W/m2) 80 160 320 InputTemperature Power/(W/m²) Sensor 1 280 3 1 2160 3 1 2320 3 Temperature Sensor 1 2 3 1 2 3 1 2 3 Initial Temperature/◦C 23.2 22.7 23.0 23.5 24.2 24.0 22.5 23.5 23.7 InitialPower Temperature/ on for 30 min/°C◦C 26.023.2 25.522.7 25.823.0 27.723.5 28.424.2 28.224.0 28.722.5 29.723.5 29.923.7 PowerDiff onerence for 30 Value min//◦C°C 26.02.8 25.5 2.8 2.825.8 4.227.7 4.228.4 4.228.2 6.228.7 6.229.7 6.229.9 Difference Value/°C 2.8 2.8 2.8 4.2 4.2 4.2 6.2 6.2 6.2 3.5. Electric Resistance Stability 3.5. Electric Resistance Stability According to Figure 12 and Table5, it can be concluded that the conductive EPDM rubber compositeAccording material to Figure has good 12 electric and Table resistance 5, it can stability be concluded at different that input the conductivepower. During EPDM the 30rubber min ofcomposite power-on, materia the electricl has good resistance electric fluctuates resistance only stability in a small at different range. input Since power. the area During of the samplethe 30 min for electrothermalof power-on, the test electric is larger resistance than that fluctuates of other active only snowmeltin a small deicingrange. Since studies the [ 21area,29 ],of the the size sample effect for of theelectrothermal composite intest practical is larger applications than that of can other be eactiveffectively snowmelt reduced. deicing When studies the input [21, power29], the is size 80 W effect/m2, 160of the W /compositem2 and 320 in W practical/m2, the correspondingapplications can average be effectively values ofreduced. the resistance When arethe 0.60inputΩ ,power 0.61 Ω isand 80 0.61W/m²,Ω, 16 respectively.0 W/m² and The 320 fluctuations W/m², the corresponding are 2.9%, 2.4% average and 1.1%, values respectively, of the resistance compared are with 0.60 the Ω, average. 0.61 Ω and 0.61 Ω, respectively. The fluctuations are 2.9%, 2.4% and 1.1%, respectively, compared with the average.

Polymers 2019, 11, 2051 13 of 17 Polymers 2019, 11, x FOR PEER REVIEW 13 of 17

Figure 12. The variation of resistance with power-on time at different input power. Figure 12. The variation of resistance with power-on time at different input power. Table 5. Resistance change with energization time at different input power. Table 5. Resistance change with energization time at different input power. Time/min 0 5 10 15 20 25 30 Time/min 0 5 10 15 20 25 30 Input 80W/m2 0.618 0.607 0.596 0.593 0.591 0.596 0.602 Resistance InputInput 160W 8/m0W2 /m²0.628 0.618 0.609 0.607 0.607 0.596 0.609 0.593 0.612 0.591 0.615 0.596 0.614 0.602 Value/Ω Resistance Value/ΩInput Input 320W 16/m0W2 /m²0.617 0.628 0.609 0.609 0.613 0.607 0.608 0.609 0.607 0.612 0.604 0.615 0.610 0.614 Input 320W/m² 0.617 0.609 0.613 0.608 0.607 0.604 0.610 Since the sample is directly connected to the alternating current, there is a certain voltage Since the sample is directly connected to the alternating current, there is a certain voltage fluctuation. As a result, the corresponding voltage value and the current value have small fluctuations. fluctuation. As a result, the corresponding voltage value and the current value have small But the electric resistance is about 0.61 Ω, which has little effect on the heat generation stability of the fluctuations. But the electric resistance is about 0.61 Ω, which has little effect on the heat generation circuit. According to the results of the resistance stability tests, it can be proven that the conductive stability of the circuit. According to the results of the resistance stability tests, it can be proven that EPDM rubber composite material has excellent resistance stability and it can ensure the stable heat the conductive EPDM rubber composite material has excellent resistance stability and it can ensure generation during use. the stable heat generation during use. 3.6. Joule Heating Performance of Conductive EPDM Rubber Composite Material 3.6. Joule Heating Performance of Conductive EPDM Rubber Composite Material It can be seen from Figure 13 that the joule heating performance of the conductive EPDM rubber compositeIt can materialbe seen fr isom di ffFigureerent after13 that inputting the joule di heatingfferent power.performance The temperature of the conductive rises faster EPDM when rubber the inputcomposite power material is larger. is different And there after is inputting no change different at room power. temperature. The temperature As can be rises seen faster from when Table the6, wheninput thepowerinput is powerlarger. isAnd 80 W there/m2, 160is no W change/m2 and at 320 room W/m temperature.2, the corresponding As can b temperaturee seen from rise Table rates 6, when the input power is 80 W/m², 160 W/m² and 320 W/m², the corresponding temperature rise rates are 5.6 ◦C/h, 8.4 ◦C/h and 12.4 ◦C/h, respectively. Compared with other active deicing methods [10,37,38], theare input 5.6 °C power/h, 8.4 is °C/h lower and and 12.4 the temperature °C/h, respectively. rises faster. Compared It shows with that other the conductive active deicing EPDM methods rubber composite[10,37,38], materialthe input can power more is e fflowerectively and realize the temperature road deicing rises and snowfaster. removal. It shows Due that to the the conductive low input power,EPDM therubbe conductiver composite EPDM material rubber can composite more effectively material isrealize more environmentallyroad deicing and friendly snow removal. as an electric Due heatingto the low material, input andpower, has the a better conductive effect on EPDM road deicingrubber composite and snow melting.material is more environmentally friendlyAccording as an electric to Table heating6, due tomaterial, the presence and has of thea better thermal effect insulation on road layer, deicing the and temperature snow melting. rise rate of the composite surface varies greatly. When the input power is larger, the difference in temperature rise rate between the upper and lower layers is larger. The input power is 80 W/m2, 160 W/m2 and 2 320 W/m , and the temperature increase rate is about 3.6 ◦C/h, 5.2 ◦C/h and 7 ◦C/h, respectively. It shows that the thermal insulation layer of conductive EPDM rubber composite material has a good effect. The structural layer design proposed in this study has a good effect. The heat insulation layer can effectively block the downward transfer of heat, so that the heat can be transferred to the upper layer more, and the temperature of the upper layer rises faster. The transfer of heat has a certain directionality, which is beneficial to achieve rapid road deicing and snow melting.

Polymers 2019, 11, 2051 14 of 17 Polymers 2019, 11, x FOR PEER REVIEW 14 of 17

Figure 13. Temperature changes with energization time under different input power. Figure 13. Temperature changes with energization time under different input power. Table 6. Temperature rise rate under different input power. Table 6. Temperature rise rate under different input power. Heat Flux Density/(W/m2) 80 160 320 Heat Flux Density/(W/m²) 80 160 320 Upper layer 5.6 8.4 12.4 Temperature Rise Rate/( C/h) Upper layer 5.6 8.4 12.4 Temperature Rise Rate/(°C◦ /h) Lower layerLower layer 2.0 3.22.0 5.43.2 5.4

4. ConclusionsAccording to Table 6, due to the presence of the thermal insulation layer, the temperature rise rate of the composite surface varies greatly. When the input power is larger, the difference in In this paper, carbon fiber cloth is sandwiched in ethylene propylene diene monomer (EPDM) temperature rise rate between the upper and lower layers is larger. The input power is 80 W/m², 160 rubber composite to obtain a conductive EPDM rubber composite material. It has been verified by W/m² and 320 W/m², and the temperature increase rate is about 3.6 °C/h, 5.2 °C/h and 7 °C/h, experiments that the conductive EPDM rubber composite material has excellent durability and heat respectively. It shows that the thermal insulation layer of conductive EPDM rubber composite production efficiency as a road active deicing and snow melting material. This study resulted in the material has a good effect. The structural layer design proposed in this study has a good effect. The following conclusions: heat insulation layer can effectively block the downward transfer of heat, so that the heat can be (1) The addition of the carbon fiber cloth not only makes EPDM rubber have good electrical transferred to the upper layer more, and the temperature of the upper layer rises faster. The transfer conductivity, but also effectively improves the mechanical properties of the EPDM rubber. The addition of heat has a certain directionality, which is beneficial to achieve rapid road deicing and snow of carbon fiber cloth increases the tensile strength by 78.3% and the tear strength by 23.1%. There is melting. no substantial influence on the compressive strength. The addition of carbon fiber cloth ensures the mechanical4. Conclusions properties of conductive EPDM rubber composite material in road use. (2) Conductive EPDM rubber composite material has excellent high temperature durability. After 72 h highIn this temperature paper, carbon treatment, fiber cloth the tensileis sandwiched strength, in tear ethylene strength propylene and compressive diene monomer strength (EPDM) of the conductiverubber composite EPDM to rubber obtain composite a conductive material EPDM increases rubber bycomposite 38.04%, 8.78%,material. and It 33.85%,has been respectively. verified by Afterexperiments subsequent that highthe conductive temperature EPDM treatment, rubber thecomposite mechanical material properties has excellent of the compositesdurability and tend heat to beproduction stable. The efficiency test results as a road show active that thedeicing composite and snow material meltin doesg material. not exhibit This study any degradation resulted in the of mechanicalfollowing conclusions: propertiesat high temperature and has good high temperature durability. This ensures long-term(1) The use addition of the composite of the carbon material fiber in cloth high temperaturenot only makes environment. EPDM rubber have good electrical conductivity(3) Conductive, but also EPDM effectively rubber composite improves materialthe mechanical has low properties temperature of stability. the EPDM After rubber. 20 cycles The ofaddition low temperature of carbon fiber cycling, cloth the increases mechanical the tensile properties strength of the by composite78.3% and materialthe tear strength show only by minor23.1%. fluctuationsThere is no andsubstantial no significant influence increase on the or decrease. compressive This strength. proves that The the addition composite of materialcarbon fiber can meet cloth theensures requirements the mechanical of long-term properties use under of conductive low temperature EPDM rubber circulation. composite material in road use. (4)(2) Through Conductive the EPDM heat production rubber composite uniformity material tests, has a large excellent area of high conductive temperature EPDM durability. rubber compositeAfter 72 h materialhigh temperature was electrified, treatment, and the the tensile temperature strength, variation tear strength of the and sample compressive was consistent. strength of the conductive EPDM rubber composite material increases by 38.04%, 8.78%, and 33.85%, respectively. After subsequent high temperature treatment, the mechanical properties of the

Polymers 2019, 11, 2051 15 of 17

This proves that the composite material can produce heat uniformly. The feasibility of achieving effective uniform deicing and snow melting is verified. (5) The composite material developed in this paper has good electrical resistance stability and do not change with heating time and different input power. The material has a low resistance value and achieves rapid temperature rise at low input power. Owing to the presence of the insulation layer, the directional transmission of heat is achieved. This provides an experimental basis for the efficient and environmentally friendly road deicing and snow melting. Subsequent experiments and theoretical studies on the actual deicing and snow melting will be carried out. In summary, the mechanical and electrothermal tests prove the feasibility and long-term performance of conductive EPDM rubber composite material. At the same time, due to the use of low-cost materials, conductive EPDM rubber composite material can be widely used in snow melting and deicing in road and other fields. The conductive EPDM rubber composite material has broad application prospects.

Author Contributions: Conceptualization, S.H. and H.W.; Data curation, S.H. and L.H.; Formal analysis, Q.L.; Funding acquisition, H.W.; Investigation, L.H.; Methodology, S.H., L.H. and Q.L.; Project administration, H.W.; Resources, Q.L.; Supervision, H.W.; Writing—original draft, S.H. Funding: This research was supported by the National Natural Science Foundation of China [grant number 51578263]. Conflicts of Interest: The authors declare no conflict of interest.

References

1. Menzies, T.R. Overview of national research council study on the comparative costs of using rock salt and cma for highway deicing. Resour. Conserv. Recycl. 1992, 7, 43–50. [CrossRef] 2. French, H.; van der Zee, S.; Leijnse, A. Transport and degradation of propyleneglycol and potassium acetate in the unsaturated zone. J. Contam. Hydrol. 2001, 49, 23–48. [CrossRef] 3. Poursaee, A.; Laurent, A.; Hansson, C.M. Corrosion of steel bars in opc mortar exposed to nacl, mgcl2 and cacl2: Macro-and micro-cell corrosion perspective. Cem. Concr. Res. 2010, 40, 426–430. [CrossRef] 4. Pruckner, F.; Gjørv, O.E. Effect of cacl2 and nacl additions on concrete corrosivity. Cem. Concr. Res. 2004, 34, 1209–1217. [CrossRef] 5. Laffray, X.; Alaoui-Sehmer, L.; Bourioug, M.; Bourgeade, P.; Alaoui-Sosse, B.; Aleya, L. Effects of sodium chloride salinity on ecophysiological and biochemical parameters of oak seedlings (Quercus robur L.) from use of de-icing salts for winter road maintenance. Environ. Monitor. Assess. 2018, 190, 266. [CrossRef] 6. Zýval, V.; Kˇrenová, Z.; Raus, M.; Štrupl, V.; Zýval, V., Jr.; Zývalová, J. Effects of deicing salt in protected areas: Water quality monitoring in the river basin with the occurrence of a rare pearl mussel. Inz. Miner. 2018, 19, 99–102. 7. Rivett, M.O.; Cuthbert, M.O.; Gamble, R.; Connon, L.E.; Pearson, A.; Shepley, M.G.; Davis, J. Highway deicing salt dynamic runoff to surface water and subsequent infiltration to groundwater during severe uk winters. Sci. Total Environ. 2016, 565, 324–338. [CrossRef] 8. Marques, J.E.; Marques, J.M.; Carvalho, A.; Carreira, P.M.; Moura, R.; Mansilha, C. Groundwater resources in a mediterranean mountainous region: Environmental impact of road de-icing. Sustain. Water Res. Manag. 2017, 5, 305–317. [CrossRef] 9. Gao, J.; Guo, H.; Wang, X.; Wang, P.; Wei, Y.; Wang, Z.; Huang, Y.; Yang, B. Microwave deicing for asphalt mixture containing steel wool fibers. J. Clean. Prod. 2019, 206, 1110–1122. [CrossRef] 10. Li, C.; Wu, S.; Chen, Z.; Tao, G.; Xiao, Y. Enhanced heat release and self-healing properties of steel slag filler based asphalt materials under microwave irradiation. Constr. Build. Mater. 2018, 193, 32–41. [CrossRef] 11. Vo, H.V.; Park, D.-W.; Seo, W.-J.; Yoo, B.-S. Evaluation of asphalt mixture modified with graphite and carbon fibers for winter adaptation: Thermal conductivity improvement. J. Mater. Civ. Eng. 2017, 29, 04016176. [CrossRef] 12. Notani, M.A.; Arabzadeh, A.; Ceylan, H.; Kim, S.; Gopalakrishnan, K. Effect of carbon-fiber properties on volumetrics and ohmic heating of electrically conductive asphalt concrete. J. Mater. Civ. Eng. 2019, 31, 04019200. [CrossRef] Polymers 2019, 11, 2051 16 of 17

13. Koenig, G.G.; Ryerson, C.C. An investigation of infrared deicing through experimentation. Cold Reg. Sci. Technol. 2011, 65, 79–87. [CrossRef] 14. Arabzadeh, A.; Ceylan, H.; Kim, S.; Sassani, A.; Gopalakrishnan, K.; Mina, M. Electrically-conductive asphalt mastic: Temperature dependence and heating efficiency. Mater. Des. 2018, 157, 303–313. [CrossRef] 15. Chen, F.; Su, X.; Ye, Q.; Fu, J. Experimental investigation of concrete runway snow melting utilizing heat pipe technology. Sci. World J. 2018, 2018, 4343167. [CrossRef][PubMed] 16. Liu, K.; Huang, S.; Xie, H.; Wang, F. Multi-objective optimization of the design and operation for snow-melting pavement with electric heating pipes. Appl. Ther. Eng. 2017, 122, 359–367. [CrossRef] 17. Han, C.; Wu, G.; Yu, X.B. Performance analyses of geothermal and geothermoelectric pavement snow melting system. J. Energy Eng. 2018, 144, 04018067. [CrossRef] 18. Liu, H.; Maghoul, P.; Bahari, A.; Kavgic, M. Feasibility study of snow melting system for bridge decks using geothermal energy piles integrated with heat pump in canada. Renew. Energy 2019, 136, 1266–1280. [CrossRef] 19. Zhang, Q.; Xu, X.; Li, H.; Xiong, G.; Hu, H.; Fisher, T.S. Mechanically robust honeycomb graphene aerogel multifunctional polymer composites. Carbon 2015, 93, 659–670. [CrossRef] 20. Ge, J.; Shi, L.A.; Wang, Y.C.; Zhao, H.Y.; Yao, H.B.; Zhu, Y.B.; Zhang, Y.; Zhu, H.W.; Wu, H.A.; Yu, S.H. Joule-heated graphene-wrapped sponge enables fast clean-up of viscous crude-oil spill. Nat. Nanotechnol. 2017, 12, 434–440. [CrossRef] 21. Chu, H.; Zhang, Z.; Liu, Y.; Leng, J. Self-heating fiber reinforced polymer composite using meso/macropore carbon nanotube paper and its application in deicing. Carbon 2014, 66, 154–163. [CrossRef] 22. Zhang, Q.; Yu, Y.; Chen, W.; Chen, T.; Zhou, Y.; Li, H. Outdoor experiment of flexible sandwiched graphite-pet sheets based self-snow-thawing pavement. Cold Reg. Sci. Technol. 2016, 122, 10–17. [CrossRef] 23. Zhang, Q.; Yu, Y.; Yang, K.; Zhang, B.; Zhao, K.; Xiong, G.; Zhang, X. Mechanically robust and electrically conductive graphene-paper/glass-fibers/epoxy composites for stimuli-responsive sensors and joule heating deicers. Carbon 2017, 124, 296–307. [CrossRef] 24. Yang, L.; Zhou, W.; Jia, J.; Xiong, T.; Zhou, K.; Feng, C.; Zhou, J.; Tang, Z.; Chen, S. Nickel nanoparticles partially embedded into carbon fiber cloth via metal-mediated pitting process as flexible and efficient electrodes for hydrogen evolution reactions. Carbon 2017, 122, 710–717. [CrossRef] 25. Yao, Y.; Fu, K.K.; Yan, C.; Dai, J.; Chen, Y.; Wang, Y.; Zhang, B.; Hitz, E.; Hu, L. Three-dimensional printable high-temperature and high-rate heaters. ACS Nano 2016, 10, 5272–5279. [CrossRef] 26. Kim, S.Y.; Baek, S.J.; Youn, J.R. New hybrid method for simultaneous improvement of tensile and impact properties of carbon fiber reinforced composites. Carbon 2011, 49, 5329–5338. [CrossRef] 27. Goldfeld, Y.; Ben-Aarosh, S.; Rabinovitch, O.; Quadflieg, T.; Gries, T. Integrated self-monitoring of carbon based textile reinforced concrete beams under repeated loading in the un-cracked region. Carbon 2016, 98, 238–249. [CrossRef] 28. Lim, C.; Park, K.; Lee, J.; Lee, B. Fundamental study for development of an anti-icing pavement system using carbon-fiber sheet. Int. J. Highw. Eng. 2016, 18, 59–65. [CrossRef] 29. Mohammed, A.G.; Ozgur, G.; Sevkat, E. Electrical resistance heating for deicing and snow melting applications: Experimental study. Cold Reg. Sci. Technol. 2019, 160, 128–138. [CrossRef] 30. Yang, J.; Zhu, X.; Li, L.; Ling, H.; Zhou, P.; Cheng, Z.; Su, A.; Du, Y. Prefabricated flexible conductive composite overlay for active deicing and snow melting. J. Mater. Civ. Eng. 2018, 30, 04018283. [CrossRef] 31. Yang, T.; Yang, Z.J.; Singla, M.; Song, G.; Li, Q. Experimental study on carbon fiber tape–based deicing technology. J. Cold Reg. Eng. 2011, 26, 55–70. [CrossRef] 32. Standardization Administration of China. Rubber, Vulcanized or Thermoplastic-Determination of Tensile Stress-Strain Properties, 528-2009; General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China: Beijing, China, 2009. 33. Standardization Administration of China. Rubber, Vulcanized or Thermoplastic-Determination of Tear Strength (Trouser, Angle and Crescent Test Pieces) 529-2008; General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China: Beijing, China, 2008. 34. Standardization Administration of China. Rubber, Vulcanized or Thermoplastic Determination of Compression Stress-Strain Properties, 7757-2009; Inspection and Quarantine of the People’s Republic of China: Beijing, China, 2009. Polymers 2019, 11, 2051 17 of 17

35. Posadas, P.; Fernández-Torres, A.; Chamorro, C.; Mora-Barrantes, I.; Rodríguez, A.; González, L.; Valentín, J.L. Study on peroxide vulcanization thermodynamics of ethylene–vinyl acetate copolymer rubber using 2,2,6,6,-tetramethylpiperidinyloxyl nitroxide. Polym. Int. 2013, 62, 909–918. [CrossRef] 36. Sharma, B.K.; Chowdhury, S.R.; Mahanwar, P.A.; Sarma, K.S.S. Structure-property relationship in terms of dynamic mechanical properties of high energy radiation treated industrially important thermoplastic elastomer blend. Adv. Mater. Phys. Chem. 2015, 5, 383–398. [CrossRef] 37. Sun, Y.; Wu, S.; Liu, Q.; Hu, J.; Yuan, Y.; Ye, Q. Snow and ice melting properties of self-healing asphalt mixtures with induction heating and microwave heating. Appl. Therm. Eng. 2018, 129, 871–883. [CrossRef] 38. Sassani, A.; Arabzadeh, A.; Ceylan, H.; Kim, S.; Sadati, S.M.S.; Gopalakrishnan, K.; Taylor, P.C.; Abdualla, H. Carbon fiber-based electrically conductive concrete for salt-free deicing of pavements. J. Clean. Prod. 2018, 203, 799–809. [CrossRef]

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).