Imerys Minerals in Polyamide 6
Talc, Mica and Wollastonite IMERYS MINERAL SOLUTIONS Minerals in Polyamide 6
Performance additives are commonly used in the Consistent color coding is used in all graphs for formulation of polyamides and other engineering ease of comparison, with green, blue, red, and black, thermoplastics to provide reinforcement, improve respectively representing GF, talc, wollastonite, and rheology or contribute to other mechanical properties. mica products. The main performance indicators are measured and presented using both ASTM and Chopped glass fiber and mineral additives are among ISO standards, where lighter and darker shades of the most common reinforcing additives used in color, respectively show ASTM and ISO test results. polyamide formulations. The purpose of this technical Differences observed in values of each property bulletin is to compare the effect of glass fiber (GF) and measured by ASTM and ISO tests are due to differences three IMERYS minerals (talc, mica, and wollastonite) in specimen size, rate of measurements and other on rheology, appearance, and mechanical properties of specifics of each test as shown on the graphs. Polyamide 6 (PA6). If different specimen types (e.g. double gated vs. single Additive performance comparison has been conducted gated specimens) or test conditions (e.g. flow vs. cross- at 30 wt% loading for minerals and 20 and 30 wt% flow directions, angle of gloss measurement, etc.) are loading for GF. Two typical wollastonite, mica, and talc compared, dark and light bars are used to differentiate grades are compared in graphical presentation of the the results. results, one representing the highest aspect ratio (HAR) form of each mineral and the other representing the lower aspect ratio (LAR) form.
A list of IMERYS products representing each category of minerals featured in this bulletin is provided in Table 1, with the first product listed under each category being the actual mineral shown in the graphical results. RECOMMENDED MINERAL PRODUCTS FOR DIFFERENT CATEGORIES OF MINERALS STUDIED
HAR HAR® 3G 84L / HAR® 3G 77L, Talc Products HAR® T84 / HAR® T77, HAR® W92 / HAR® H92
Microcrystalline Crys-talc® 7C Talc
Talc HAR Nyglos® 4W-10012, Wollastonite Nyglos® 8-10012 Nyglos® 12-10012, Aspect 4012 / Aspect 3012 M15 Wollastocoat
LAR 10 Wollastocoat, Wollastonite 400 Wollastocoat M1250 Wollastocoat Mica M400 Wollastocoat
HAR Suzorite 150 PO Mica Suzorite 250-L PO E7542 PO
Fine Suzorite 350 PO Mica Suzorite 325-G PO Wollastonite STIFFNESS (FLEXURAL/TENSILE FLEXURAL/TENSILE STRENGTH MODULUS) When it comes to strength performance, GF offers a clear A desired performance of reinforcing additives in advantage over minerals since the performance of minerals Polyamide 6 is their effect on increasing material tested at 30% loading was weaker than that even for 20% stiffness, i.e. flexural or tensile modulus. While glass GF loading. fiber (GF) is the typical standard for reinforcing PA6, 300 our results show that HAR Suzorite mica and HAR talc 257 249 closely match GF performance. The performance of other 250 200 200 200 talc, mica and wollastonite products also falls within the 170 150 performance of 20 and 30 wt% GF filled PA6, with only 150 154 138 137 135 131 124 128 128 137 126 low aspect ratio (LAR) wollastonite being less performing 100
than 20% GF. (MPa) Strength Flexural 50
0 30% GF 20% GF HAR Talc Talc Microcrystalline HAR Wollastonite LAR Wollastonite Mica HAR Suzorite Mica Suzorite Fine 10000 ASTM D790: Light bars – Rate = 1.27 mm/min 9000 ISO 178: Dark bars – Rate = 2.00 mm/min 8467 8291
8000 7648 7887 7504 7484 7331
6921 However, for double-gated specimens with weldline the 6729
7000 6587 6388 6337 performance of wollastonite is approaching that of GF. 5846 6000 5724
5000 Flexural Modulus (MPa) Flexural 4252 3983 4000 160 154 30% GF 20% GF HAR Talc HAR Wollastonite LAR Wollastonite Mica HAR Suzorite Mica Suzorite Fine Microcrystalline Talc Microcrystalline
3000 140 130
ASTM D790: Light bars – Rate = 1.27 mm/min 120 94 ISO 178: Dark bars – Rate = 2.00 mm/min 100 91 86 85 82 82 81 80 78 80 77 60
Above measurements are done on single-gated injection 38 Tensile Strength (MPa) Strength Tensile 40 30 25 molded specimens with no weldline. However, many parts 21 20
made with PA6 compounds do have weldlines due to the 0 30% GF 20% GF HAR Talc Talc Microcrystalline HAR Wollastonite LAR Wollastonite Mica HAR Suzorite Mica Suzorite Fine Single-gated (no Weldline) – Dark bars size and complexity of the parts. Most mould designs Double-gated (with Weldline) – Light bars are also based on the worst case scenario, which is the ASTM D638: Rate = 0.51 mm/min performance results with weldlines.
ASTM tensile tests allow for preparing standard Weldines are unavoidable in the production specimens using either a single injection molding gate of many plastic parts. Superior stiffness along that creates no weldline or a double-gated design that with similar strength performance to chopped results in a weldline in the center of the part. Tensile glass fiber make the HAR NYGLOS wollastonite modulus test results for specimens with weldline (light products the reinforcing additives of choice for bars below) show a clear advantage for all mica and talc parts with weldlines. products, plus the HAR wollastonite compared to GF. The tensile modulus without a weldline follows a similar trend to flexural modulus. TENSILE ELONGATION
Wollastonite products also show the highest elongation
12000 at break in tensile tests for specimens with or without weldlines. 10000 9211 SEM analyses of the failed specimens show relatively 8564 8548 8477 8269 8032 7903 7863
8000 7672
7379 better alignment or intimate mixing of wollastonite 7045 6563 6357 additives (both HAR and LAR) across the weldline, while 6000 5248 Tensile Modulus (MPa) Tensile glass fiber (GF) tends to align itself parallel to weldline, 4697 4634 causing weak interlayer bonding. Similar to GF, mica and
4000 30% GF 20% GF HAR Talc Talc Microcrystalline HAR Wollastonite LAR Wollastonite Mica HAR Suzorite Mica Suzorite Fine talc platelets also align parallel to weldline causing a Single-gated (no Weldline) – Dark bars Double-gated (with Weldline) – Light bars relatively weak point at the weldline. ASTM D638: Rate = 0.51 mm/min 9 NOTCHED IZOD IMPACT
8 7.7 7.3 7 Similar to strength, GF also provides a clear advantage 6
5.3 in notched Izod impact performance as Izod impact 5 performance increases at higher GF loading. Among 4.2 4 4.1 minerals, the surface modified wollastonite products
3 2.5 1.8 2.0 1.9 1.8 2.1 1.7
Tensile Elongation, (%) Elongation, Tensile 2 provided the best Izod impact performance comparable to 0.6
1 0.4 0.4 0.5 that of 20% GF filled formulations.
0 30% GF 20% GF HAR Talc Talc Microcrystalline HAR Wollastonite LAR Wollastonite Mica HAR Suzorite Mica Suzorite Fine Single-gated (no Weldline) – Dark bars Double-gated (with Weldline) – Light bars 140 ASTM D638: Rate = 0.51mm/min
120 115.3 105.0 100
80 68.2
ADDITIVE ORIENTATION 64.7 59.0 61.5 59.0
60 56.3 45.2 42.1 35.8 31.9 32.8 32.1 40 29.5
No Weldline At Weldline 28.4 Notched Izod Impact, (J/m) Notched Impact, Izod 20
0 30% GF 20% GF HAR Talc Talc Microcrystalline HAR Wollastonite LAR Wollastonite Mica HAR Suzorite Mica Suzorite Fine
ASTM D256 at 23°C – Dark bars ISO 180 at 23°C – Light bars GLASS FIBER 200 μm
Among minerals, the surface treated HAR wollastonite provides the best balance of polymer properties in PA6, while HAR mica and talc provide the best stiffness. HAR NYGLOS® 20 μm
RHEOLOGY IMPROVEMENT Glass fiber filled PA6 is known to have melt flow limitations, which makes it hard to injection mold. Spiral LAR NYGLOS® 20 μm flow injection molding shows that using minerals could significantly improve spiral mold flow length compared to GF, with HAR wollastonite, microcrystalline (LAR) and HAR talc products giving the best performance. HEAT DEFLECTION TEMPERATURE HDT tests show slightly weaker performance for minerals compared to GF, while still significant enhancement 500 454 in HDT was obtained with HAR wollastonite being the 452 450
best performer, followed closely by HAR mica and talc 426 407 products. 404 400 395 368 356 350 Spiral Mold Flow Length, mm Length, Mold Flow Spiral
250 300 30% GF 20% GF HAR Talc Talc Microcrystalline HAR Wollastonite LAR Wollastonite Mica HAR Suzorite Mica Suzorite Fine
ASTM D256 at 23°C – Light bars 230
218 ISO 180 at 23°C – Dark bars 212 211 209 207 210 206 205 195 190 HAR wollastonite, microcrystalline talc, and HAR talc significantly improve the rheology of 170
Heat deflection Temp. (HDT), ˚C (HDT), Temp. Heat deflection PA6 formulations compared to chopped glass
150 30% GF 20% GF HAR Talc Talc Microcrystalline HAR Wollastonite LAR Wollastonite Mica HAR Suzorite Mica Suzorite Fine fibre. ISO 75 at 0.45 MPa Edgewise, 100mm Span DIMENSIONAL STABILITY AND ISOTROPY The anisotropy of GF expands beyond dimensional Improving dimensional stability as in reduced mold stability into mechanical properties. Flexural modulus shrinkage and CLTE (Coefficient of Linear Thermal and strength measurements conducted on standard Expansion) is a desirable performance for minerals and ISO plaques show significantly weaker performance in GF in polyamide formulations. This study shows that cross-flow direction for GF, while talc and mica products HAR talc followed by microcrystalline talc and HAR mica provide Isotropy and the best stiffness and strength produce the best dimensional stability (lowest shrinkage performance balance in both directions. and CLTE) in both mold flow and cross flow directions, while GF followed by HAR wollastonite provide comparable performance only in the flow direction, with
cross-flow direction being significantly weaker. 10000 8542
8000 7697 7103 7069 7028 6428 6152 5931 5897 5538 1.0 6000 4862 4883 0.84 4517 4076 0.82 0.8 3955 0.73 4000 Flexural Modulus, MPa Modulus, Flexural 3097
0.6 0.60 30% GF 20% GF HAR Talc Talc Microcrystalline HAR Wollastonite LAR Wollastonite Mica HAR Suzorite Mica Suzorite Fine
0.46 2000 0.44 0.41 0.37 0.36 0.57 0.4 0.35 0.34 0.31 Flow Direction – Dark bars 0.27 Mold Shrinkage, % Mold Shrinkage, 0.25 0.24 Cross Flow Direction – Light bars 0.2 ASTM D790: Rate = 0.51mm/min
0.0 30% GF 20% GF HAR Talc Talc Microcrystalline HAR Wollastonite LAR Wollastonite Mica HAR Suzorite Mica Suzorite Fine
Flow Direction – Dark bars Cross Flow Direction – Light bars Internal Method / Measurement Fixture 300
250 255
200 181 159 158
100 137 150 132 127 128 125 124 124 120 118 117 84 100 114 111 80 74 73 Flexural Strength, MPa Strength, Flexural 70 50 °C 63 -5 60 61.1 58 60 56 53.8 30% GF 20% GF Talc Microcrystalline HAR Wollastonite LAR Wollastonite Mica HAR Suzorite Mica Suzorite Fine 0 HAR Talc 51 47 47 45 CLTE, 10 CLTE, 42
41 Flow Direction – Dark bars 40 Cross Flow Direction – Light bars ASTM D790: Rate = 0.51mm/min
20 30% GF 20% GF HAR Talc Talc Microcrystalline HAR Wollastonite LAR Wollastonite Mica HAR Suzorite Mica Suzorite Fine
Flow Direction – Dark bars Cross Flow Direction – Light bars Internal Method / Measurement Fixture (23°C - 70 °C)
Industrial parts are designed based on the weakest mechanical properties of materials/ The difference in dimensional stability in flow and cross- formulations, so isotrophy or strong flow directions cause dimensional anisotropy that results performance in cross-flow direction are in warpage of injection molded parts, which is especially desirable for many parts. Talc and mica provide evident in thinner and larger parts. Acicular additives such the best isotrophy and optimum balance of as GF and wollastonite cause anisotropy due to their one properties in two dimensions. dimensional aspect ratio, while talc and mica products are isotropic in two dimensions. POLYAMIDE NUCLEATION APPEARANCE As a semicrystalline polymer, the performance Minerals are naturally occurring, so their color and and properties of PA6 are affected by its degree of appearance vary even within the same type of mineral. crystallization. Differential Scanning Calorimetry In general, among the minerals tested, wollastonite offers (DSC) analyses conducted on mineral and glass fiber the highest brightness/ whiteness followed by talc that filled PA6 formulations show that their crystallization could be white to off-white, and mica that comes in off- temperature varies with the type of additives used. Both white to brown colors, but has a special glitter and shine. microcrystalline and HAR talc increase the crystallization The gloss performance, however, appears to vary with temperature of PA6 by 15-17°C compared to GF at 30 the type of mineral. Wollastonite filled PA6 formulations wt% loading, while mica and wollastonite gave only created higher gloss values than GF-filled PA6, while talc 1-2°C increase compared to GF. produced the lowest gloss and mica gave rather similar gloss to GF.
210 207.0 100.6 204.9 102.8 100.5 99.6 100 98.0 97.7 95.9 94.0 200 93.1 92.5 90.9 90.6 89.1 85.2 84.4 192.1 192.5 191.9 191.3
189.7 80 190 188.7 68.9 Gloss, % Gloss,
Crystallization Temperature (Tc), °C (Tc), Temperature Crystallization 60 30% GF 20% GF Talc Microcrystalline HAR Wollastonite LAR Wollastonite Mica HAR Suzorite Mica Suzorite Fine 180 HAR Talc
Tc for Neat PA6 = 188°C 30% GF 20% GF Talc Microcrystalline HAR Wollastonite LAR Wollastonite HAR Talc 40 Mica HAR Suzorite Mica Suzorite Fine
85° Gloss – Dark bars Further studies show that the effect of talc on 60° Gloss – Light bars crystallization temperature starts at loading levels below 0.5 wt%. The effect is observed even when talc is used in combination with other additives such as glass fiber or CONCLUSIONS AND PRODUCT RECOMMENDATION other minerals. Performance evaluation of wollastonite, talc, and mica in PA6 shows specific attributes to each mineral, which could be utilized based on the required performance or specifications of each application/part. 210 199.7 199.6 197.7
200 197.6 192.8
191.6 - Wollastonite provides the best balance of 191.4 190.9
190 188.0 properties for parts that are designed with
Wollastonite weldline, and whose performance and Crystallization Temperature, °C Temperature, Crystallization properties are sensitive to weldline. We Neat PA6 180 Talc Microcrystalline Talc Macrocrystalline HAR Mica Suzorite Fine recommend HAR wollastonite products such 3.0% Additive Loading – Dark bars © 0.5% Additive Loading – Light bars as NYGLOS 4W-10012 to replace GF in these applications.
Talc can be used by itself, with GF, or with - Talc and mica provide the best balance of other minerals to nucleate polyamides and properties for parts that require similar significantly increase their crystallization performance in two dimensions as they temperature to speed up industrial processes, provide isotropic mechanical properties e.g. to reduce injection molding cycle time. and dimensional stability. We recommend HAR® talc and fine Suzorite mica for these applications. Testing: - Talc has a unique efficacy to nucleate PA6 - Flexural properties: ASTM D790 (at 0.05 in/min and 2 and increase its crystallization temperature. in span) and ISO 178 (at 2 mm/min and 64 mm span) We recommend using microcrystalline - Tensile properties: ASTM D638 (at 0.2 in/min speed) talc by itself or in combination with GF or and ISO 527 (Type 1A) at 5 mm/min other minerals to increase crystallization - Notched Izod Impact: ASTM D256 and ISO 180 at 23°C temperature and reduce industrial processing times. - HDT: ISO-75 at 0.45 MPa in edgewise orientation and 100 mm span - Talc and mica offer the best performance - Shrinkage: internal method using 60x60 mm injection for improving isotropy and cross-flow molded plaques and a specially designed measurement mechanical performance. We recommend fixture using talc and mica in combination with GF - Crystallization temperature: or other fiber ASTM D3418-15 – heating/cooling/heating cycle reinforcement to improve isotropy. at 20C/min using DSC-25 TA instruments - HAR mica provides the highest stiffness - Coefficient of Linear Thermal Expansion (CLTE): reinforcement that competes with chopped in-house fixture and method (23-70°C) GF, so it is recommended for applications - Ash content: internal method using microwave ash oven requiring enhanced stiffness. - Density: Mettler Toledo MS semi-micro balance and density kit - Moisture: Computrac Vapor Pro Moisture Analysis EXPERIMENTAL PROCEDURE - Color (CIE L* a* b*): Konika Minolta Chroma Meter/ Material used: Colorimeter CR-400 - PA6: Ultramide B27E (BASF) - Gloss: Gardner micro-Tri-gloss meter - Glass Fiber: EC10-675, 4mm (Johns Manville) - IMERYS Talc, Mica, and Wollastonite as listed in the text - SEM: Hitachi S4300
Compounding: - Berstorff ZE 25A x 46D UTXi twin-screw extruder COMPOSITIONAL ACCURACY D= 25 mm, L/D=46, 250 rpm, 15 kg/hr To verify the accuracy of composition and quality of - GF and mica feed-port: molded specimens obtained in the compounding and downstream side-feeder at Barrel Zone 5 injection molding process, the density of specimens were - HAR Talc and wollastonite feed-port: compared with the theoretical formulation density. side-feeder at Barrel Zone 3 - Other fine talc feed-port: extruder throat 1.45 - Drying PA6 to < 0.4% moisture
1.40 1.383 1.382 1.383 1.379
Injection Molding: 1.377 1.377 1.376 1.376 1.376 1.375 1.375 1.367 - Arburg Allrounder 370E 600-170 IM press 1.355 1.35 1.346 - Drying the compound to < 0.2% moisture 02/19 Density, g/cc Density, - ISO and ASTM standard specimen molds 1.30 1.270 - Spiral-flow mold 1.271
1.25 30% GF 20% GF HAR Talc Talc Microcrystalline HAR Wollastonite LAR Wollastonite Mica HAR Suzorite Mica Suzorite Fine
Measured – Dark bars Theoretical – Light bars
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