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237

A Study on the Weldability of Reinforced en)

Hiroshi KIMURA*, Takuzi YAMAGUCHI*, Masaki IMAcHl**, Masakazu TSUBOKAWA*, Giichi KAWASHIMA*, Shingo HAMAGUCHI*

(Received March 17. 1972)

In this paper we describe of the adhesive propertes between and polyethylene or, in other words, of the weldability including combination of glass fiber base material and resin.

INTRODUCTION As a neW method of molding of fiber glass reinforced polyethylene (FRPE), we have made an impregnation sheet by combining glass fiber base material in the form of mat (E glass fiber made by Nittobo Co., Ltd.) and resin made into film beforehand (high pressure polyethylene made by Sumitomo Chemical Co., Ltd.). We wish to present here the properties and weldability of such impregnation sheet obtained through a series of experiments. There have been many reports on fiber glass 1l2 3 reinforced thermoplastics (FRTP) ; e. g. FRV ) with polyvinylchloride, Stampglas ) and AZDEL A-I004) by Owens-Corning Fiberglas Corp. (OCF) and GRTL Corp. res­ pectively with polypropylene, and AZDEL A-200') by GRTL Corp. with AS resin.

EXPERIMENTAL RESULTS AND CONSIDERATION

6 As we had reported previously on ultrasonic welding ), we have this time used heating plate welding method. Fiber glass reinforced polyethylene has been made by impregnation sheet method with hot press, and possibility of welding by heating plate has been explored. In an experiment like this, it is essential that the glass fiber base material has been satisfactorily impregnated with resin and that the adhesion between these two is strong. The impregnation sheet we have used in the experiments had 30% in the ratio of glass fiber content, registered approximately 5 times as much of the tensile strength of the resin base material and showed comparatively good con­ dition of impregnation in microscopic examination. Now, in welding of fiber glass reinforced polyethylene, it is necessary that the glass fiber diffuses mutually on both sides of welding part, and that the resin is deposited sufficiently and induces fully the glass fiber which has diffused mutually. From Fig. 1, which shows the result ef

* Dep. of Eng. ** Textile Research Institute 238 experiment concerning relationship between lap le­ 7 ngth and welding strength, it is appreciated that the ~6 welding strength of 0.25 mm. thick FRPE with 3 mm. 1. 1 1 E -- lap length almost reaches the strength of fiber glass -.21 5 :~r~i=4=1--~ reinforced polyethylene sheet. However, since the mutual diffusion of glass fiber and deposition of resin including the glass fiber cannot be accompli­ ~r shed successfully at both ends of the lap, it has

become apparent that no perfect welding can be ~ r-Welding pressure :0.5 kg/mnL expected within about 1 mm. from both ends of the Welding temp. :137 ·C I I I I lap. Fig. 2 shows the welding conditions with rela­ 2 3 4 5 6 tion to welding temperature, welding pressure, ratio Lap length (mm) of glass fiber content, welding joint strength and Fig. 1 Relation between welding welding joint efficiency. Comparing these experim­ lap length and tensile str­ ents, we have ascertained that the welding condition ength for the fiberglass shown under Fig. 2 (b) has produced excellent wel­ reinforced polyethylene (0.25mm sheet). ding strength and almost 100 % in welding joint efficiency irrespective of the ratio of glass fiber content, which 100 % in welding joint efficiency is equivalent to that of the base material itself. Incidentally, when the welding pressure is increased, comparatively gibber welding strength is obtained at lower range of welding temperature, and the higher the welding temperature be, the welding strength becomes less. This phenomenon is attributable to the fact that the resin starts viscous flow under excessive welding pressure, thence welding cannot be performed under the condition of the glass fiber being included sufficiently with the resin as mentioned above. Microscopic examinations have been carried out on com­ positness of test pieces prepared by the impregnation sheet method, a new method of molding of fiber glass reinforced polyethylene, as well as on deposit mechanism in welding experiments using such test pieces. Photo. 1 shows microscopic structure of composit materials made by impregnation sheet method, while photographs (b) and (c) give microphotographs of the materials which have been caused strain of 0.5 % and 1.0% respectively by applying tension laterally at the speed of 10 mm/min. From these photographs, the glass are seen to have been moved slightly with the flow of inclusion resin following overall flow, and this means that the adhesion of glass fiber to resin is satisfactory. Photo. 2 shows process of tension test of fiber glass reinforced polyethylene until breakdown, and composite condition of glass fiber and resin can be observed macroscopically. Namely, under strain of 1.8 %. necking phenomenon is clearly seen, and at the place where strain reaches 2.5 %, void hole can be seen and rupture is initiated. The glass fiber base material and the inclusion resin are breaking away at this point, and the strength in this neighborhood can be deemed to be the limit of adhesion of the glass fiber and the resin. Furthermore, under strain of 4 %, as shown in photograph (c), propagation of breaking-down becomes more vehement, and when strain reaches 5 % the fiber glass reinforced 239

7~-~1 ~--~1 ---1~-~1 ~1 --~-- 7r--~1 ~1 --~1 ---1~-~1 ~1 --~1--~

6 "E Glass content :30wt.'I, "E 6 Glass content :30wt.'I. 100 100 ~5 " ------T~-i---f=y=j=--- ~5 "------r~t~l-t-t=---

( 75 ~ ~4 ~ ~4 1-- ;r 75 t 3 / 15wl'/, G' ~ ~ 3 J 15we/, G' i 2 ------;fli~t=l=f=t~-- 5°11~~~ i 2 : -- -- ¥frt~f-~-f-f~ ~ 5°11~~ ~ ~ 1 I-- ,f Plate thickness : 025 mm 25 50 .§ ~ 1 ~ Plate thickness : 0.25mm 25 50 .§ Welding pressure: 0.30kg/mrrl 25 ..., Welding pressure 0.45kg/mrrl 25 ..., 0L-___9~0-L_11 LO~ __~ __L_~ I ___L __ ~L 0 0 0~~1~90~I _l~10~ __-L __ ~ IL-~I __~ I __~L 0 0 80 100 120 140 160 180 200 80 100 120 140 160 180 200 Heating plate temp. ('e) Heating plate temp. (DC) I :.:;.00 137 eo 120 152 166 180 80 lQ9. 1.?9 . 137 152 166 180 Weld zone- temp. ('C) "' Weld zone temp. ('C) (a) (b)

7 I I I I I

...... 6 Glass content :30wt.'I, · 6 Glass content : 30 wt~/, "E "E i: - ~ - -- yFF-~f=l=t~~- 100 ':: 75 t !:"------fJt=+~1~~I~-- >- >- ~ 3 ~ 1! I L 15wt~/. _ ~ ~ 50 100 :g 50 100 :Q 2 ~- --_WH=t~Y=r=I:c-- i 75 ~ t: f~tft1---t=t=l~?~- 75~ ~ 25 50 .~ ~ 25 50:£ Plate thickness : 0.25 mm 0 1 I- Plate thickness : 0.25 mm o Weld ing pressure : 0.60kg/mrrl 25 ..., Welding pressure :0.75kgjmn1 25 ..., ______0L-~~90~1 ~1~10~~I __L- __L-~ I __~~~L 0 0 0L-~_9~0~I _l~10~L-I L-I ~I ~I ~I J~ o o 80 100 120 140 160 180 200 80 100 120 140 160 180 200 Heating plate temp' ('C) Heating plate temp. ('C) ! ! I ! , I I ! , 80 100 120 137 152 166 180 80 100 120 137 152 166 180 Weld zone temp. ('C) Weld zone temp. (DC) (c) (d) Fig. 2 Welding conditions for the fiberghss r einforced polyethylene (Heating tool welding m ethod).

Tensile----­ direction Tensile direction (a) (b) (c)

Base material Tensile strain: 0 . 5% Tensile strain: 1.0%

Fiberglass content: 3 0 % Tensile speed: 10 rmn/ min Tensile speed: 10 mrn/ min

Photo. 1 Microscopic structure of com;;>osit materials m ade by impregnatbn she~:.t. polyethylene breaks down almost entirely. Photo. 3 is a microphotograph of boundary zone of deposit of fiber glass reinforced polyethylene sheet, from which it is clearly 240

(a) (b) (c) (d)

Tensile strain : l . 8 % Tensile strain : 2.5% Tensile strain:4 . 0 % Tensile strain: 5 .0 % Ph:)t o. 2 Process of tensi)n t est of fiber glass r cinfJrCcd polyethylen e u ntil br e3kd :)wn.

(a ) (b)

Microscop e of 7 0 d irect ma gnifications Mic r o s cope o f 28 d ire ct magni f i cations Phot o. 3 Microph:)t :)graph of boundary zon e of deposit e of fiberglass reinforced polyethylen e sheet. (T ensile strain 2.0 %) seen that the glass fiber is considerably diffused mutually. It is also observed from this photograph that the surface resin has been subjected to viscous flow considerably on ac'Cqunt of the surface at the weld of impregnation sheet being heated by direct contact of heating plate and, therefore, that the ratio of glass fiber content has be­ come greater. With welding test piece, no initiation of rupture is observed under strain of 2 %.

CONCLUSION

The following summary can be made from the results of the present experiments. It is interesting to note that fiber glass reinforced polyethylene has excellent physical properties and economic advantage of polyethylene, plus strength and heat resisting properties. However, the adhesive properties which are dependent upon polarity peculiar to polyethylene bring out problems and this is why the industrialization of polyethylene is somewhat fallen behind. In this report, we have treated of adhesive properties between fiber giass and polyethylene or, in other words, of weldability 241 including combination of glass fiber base material and resin. From this report, you may find that the composit material of polyethylene of bigger strength can be obtained through the impregnation sheet method in which glass fiber base material of mat form is combined with resin, and that the result of welding can be as excellentas the itself.

ACKNOWLEDGMENTS

The authors would like to express sincere thanks to Nittobo Co. Ltd. for preparing to base materials. Part of this work was presented at the Annual Meeting of the Japan Welding Society, Tokyo, April 1972.

REFERENCES

1) H. Hani, H. Hiraga, "Fiber Glass Reinforced PVC", 23rd SPI, 2-B (1968). 2) T. Ishimatsu, K. Hirao, S. Uemura, "Press Forming Reinforced PVD Sheet", 25th. SPI, 6-B (1870). 3) J. A. Keown, "Fiberglass/plastic Design Guide", 26th. SPI, 16-E (1971). 4) R. L. Van Boskirk, "Carbide/pPG Introduce RTP Sheet for Metalworking", Modern , 45 (6), 116 (Feb. 1968). 5) "Union Carbide, PPG Develop Stamable Thermoplastic". Autoproducts, (Mar. 1968). 6) Hiroshi KIMURA, Takuzi YAMAGUCHI, Masaki IMACHI, Masakazu TSUBOKAWA, Giichi KAWASHIMA, Eiji WATANABE, "A Study on the Weld ability of Fiberglass Reinforced Poly­ ethylene", Memoirs of the Faculty of Fukui University, Vol. 19, No.2, 127 (1971).