HIGH PERFORMANCE HAR TALCS IN PLASTICS

HIGH PERFORMANCE HAR TALCS IN PLASTICS Superior flexural modulus enabling downgauging Excellent dimensional stability Good stiffness/impact balance

Figure 1. Lamellarity of HAR s versus conventional s d50 laser - d50 Sedigraph *I.L = d50 Sedigraph INTRODUCTION Current trends in the automotive industry are towards increasingly highperformance products, particularly in the realm of weight reduction and zero-gap design. Because conventional jet milling technologies, also known as micronisation technologies, have reached their full potential for both grinding and delaminating, Imerys has developed a range of high aspect ratio HAR s to meet the demands of automakers. Produced using an innovative, patented delaminating process (1), HAR s have a higher aspect ratio than other conventionally micronised grades. They provide improved mechanical properties when compounded in polypropylene versus conventional s or fillers, without impairing the ductility of the moulded parts. HAR s are supplied in microsphere densified form and have excellent flow properties for easy handling and high compounding throughput. Lamellarity index (*IL) 15 14 13 12 Delaminating process 11 10 9 8 7 6 5 4 Jet milling 3 2 1 0 0 5 10 15 20 25 30 35 40 45 Specific surface (BET, Ar) (m 2 /g) PERFORMANCE IN POLYPROPYLENE HAR and a reference were compounded using a twin-screw co-rotating extruder and then introduced in the polypropylene melt via a sidefeeder so as to obtain optimum performance (see HAR processing recommendations). All properties related to the aspect ratio were improved with HAR : flexural modulus (up by 20%), CLTE (down by 20%), shrinkage (down by 8%). Moreover, the stiffness/impact balance remains excellent. Figure 2 summarises the results and illustrates the benefits that can be obtained with HAR s. Figure 2. HAR performance at 20% in PP copolymer CLTE (10-6.K -1 ) 80 89 3190 2700 5.9 6.2 Izod impact (kj/m 2 ) 23 C 24 0.95 1.03 69 37 Charpy impact (kj/m 2 ) - 20 C Shrinkage (%) 73 Very fine HAR HDT ( C) (1) Patent reference: Lamellar filler process for the treatment of polymers, PCT, WO 98/45374 N.B.: Best values are towards the exterior of the axes. One graduation is two standard deviations.

CLTE (10-6.K -1 ) Mechanical properties Very fine HAR 2700 3190 CLTE (10-6.K -1 ) 89 80 Shrinkage (%) 1.03 0.95 HDT ( C) 69 73 Izod impact strength at 23 C (kj/ m 2 ) Unnotched Charpy impact strength at -20 C (kj/m 2 ) 5.9 6.2 37 24 Tests show that HAR is the best option for automotive parts such as zero-gap bumpers. In a formulation using 90% PP copolymer (reactor grade, MFR = 10) and 10%, HAR s demonstrated 15% lower CLTE levels compared to very fine s. 160 140 120 100 80 60 40 Figure 3. CLTE performance of HAR versus several grades (10% loading in copolymer) Neat PP Coarse Table 1. Fine Very fine HAR HAR TALC FOR LIGHTWEIGHTING One solution for reducing the weight and density of plastics parts is to use HAR to replace more conventional fillers. In the example below, we replaced 20% of a very fine 7µm top-cut in a TPO formulation (high flow PP copolymer blended with 10% of an ethylene-octene elastomer) with 15% HAR. Due to its superior lamellarity, the TPO reinforced with 15% HAR presented the same stiffness as the TPO reinforced with 20% of a 7µm top-cut. Moreover, reducing the mineral content led to a significant improvement in impact strength as measured by izod at room and cold temperatures (Figure 4). Yield strength (MPa) Density Figure 4. Outstanding balance of properties with HAR reinforced TPO Performance in high MFR PP copo/elastomer 20% 7µm top-cut 15% HAR 2270 0.99 21.4 2215 21.2 8.2 1.04 55 56 3.2 9.1 Izod 23 C (kj/m 2 ) 3.8 Izod -20 C (kj/m 2 ) HDT ( C) HAR s enable car manufacturers to meet weight reduction and zero gap targets. In this test, we achieved a 5% reduction in part density with a 25% reduction in loading whilst maintaining and even improving the overall stiffness/impact balance of the part. Figure 5. Part density reduction of 5% with HAR 15% HAR 20% 7µm top-cut 0.96 0.98 1 1.02 1.04 Compound density

HAR 3G, A NEW, IMPROVED GENERATION OF HAR TALCS Imerys has recently launched a new, improved HAR range, HAR 3G, to improve even further the performance of -reinforced compounds. This optimised HAR 3G process ensures a product with a better top-cut control. Figure 6. Comparison of HAR T84 and new HAR 3G 84L particle size distribution (sedigraph data) Total energy (-20 C) Figure 7. HAR 3G 84L confers improved impact resistance 24 19 15 10 5 Steamic 00SF Falling weight impact HAR T84 HAR 3G 84L Cumulative mass (%) 100 75 50 25 0 0.1 1.0 10.0 100.0 Equivalent spherical diameter (µm) New HAR 3G 84L and HAR 3G 77L s provide superior stiffness/impact balance in polymer compounds. In TPO for example, whilst stiffness and dimensional stability are maintained, Charpy impact performance is improved by 10% as demonstrated in Table 2 and Figure 7. This is particularly relevant for automotive, domestic appliance and packaging applications. Table 2. Evaluation of HAR 3G 84L in PP compounds Unit Steamic 00S F HAR 3G 84L HAR T84 HAR T84 HAR 3G 84L Flexural modulus MPa 2510 2955 2965 5100 4600 4100 3600 3100 2600 2100 1600 HAR TALC VERSUS SHORT GLASS FIBRE IN POLYPROPYLENE HAR particles are exceptionally lamellar and, unlike short glass fibre (SGF), their aspect ratio is not impaired during the extrusion process. As a result, the stiffness and toughness properties of HAR reinforced composites are close to those of SGF. Due to its superior performance, HAR is opening up new horizons for usage as an alternative to SGF in applications where market specifications are less stringent about stiffness. No bonding additives are required for processing. 40µm top-cut Figure 8. Polypropylene homopolymer 10µm top-cut HAR T84 SGF 60 50 40 30 20 10 0 Charpy unnotched 23 C (kj/m²) Charpy impact unnotched @-20 C kj/m 2 64 30 33 Flexural modulus with 20% Flexural modulus with 30% Impact with 20% Impact with 30% Izod impact notched @23 C kj/m 2 7 5.5 6 HDT A C 58 62 61.5 Shrinkage % 0.75 0.6 0.6 CLTE 10-6/ C 105 90 90 Falling weight impact-total energy @-20 C Falling weight impact-peak force @-20 C J 24 11 16 N 2390 2280 2470 5500 5000 4500 4000 3500 3000 2500 2000 1500 40µm top-cut Figure 9. Polypropylene copolymer 10µm top-cut HAR T84 SGF 80 70 60 50 40 30 20 10 0 Charpy unnotched 23 C (kj/m²)

Compared to needle-like SGF, the positioning and homogenous dispersion of HAR particles within the polymer matrix provide a better isotropic effect and dimensional stability. Material filling flow Figure 11. Cut direction of test samples CLTE (10-6.K -1 ) 170 160 150 140 130 120 110 100 90 80 70 60 Whatever the flow direction of the injected part, tests showed a very good surface appearance and regular CLTE performance. Figure 10. Better dimensional stability with HAR GOOD parallel perpendicular POOR 5% 10% 15% 20% 5% 10% 15% 20% 5% 10% 15% 20% PP/ 40µm top-cut PP/HAR PP/mineral fibre 90 perpendicullar to flow 45 to flow Figure 12. illustrates flexural modulus on the plaques measured in the three directions. When measured parallel to flow, the flexural modulus of the HAR reinforced PA is 15% higher than the glass-fibre reinforced PA. Compared to average values, the HAR formulation demonstrates 65% superior stiffness. ISOTROPY OF HAR TALC REINFORCED PLASTICS 6500 Figure 12. Average flexural modulus of reinforced PA6 Injection-moulded bars, or dumbbells, are commonly used to characterise neat and reinforced thermoplastics. In reinforced composites, acicular fibres are highly oriented. Since the load is usually applied on samples in the fibre direction, resulting data are generally optimum. However, in most finished parts, the mineral particles used to reinforce the composite are more or less oriented, depending on part design and flow pattern. 6000 5500 5000 4500 5440 6170 6000 5965 5690 +66% stiffness for HAR T84 over glass fibre To build a /glass fibre comparison which reflects the performance of these finished parts, we produced injection-moulded plaques made from HAR and glass-fibre reinforced polyamide (PA) compounds. We then cut out samples in three directions: parallel to flow (0 ), perpendicular to flow (90 ), and in an intermediate direction (45 ). This is illustrated in Figure 11. 4000 3500 3000 2500 2820 3050 3590 2000 PA 6 + 30% GF PA 6 + 30% HAR T84 *Formula used by part designers : Mean 1-1-2 =(Value 0 + Value 90 +2*Value 45 )/4 Flow direction 90 to flow 45 to flow Mean 1-1-2

A similar trend is observed for tensile modulus and dimensional stability, which are enhanced and significantly less anisotropic with HAR. The performance of the glass fibre-reinforced PA is superior in terms of heat and impact resistance, as well as tensile strength. It is therefore up to the formulator and the designer to define specifications which match the material and the application. HAR PRODUCT RANGE Table 3. Flexural modulus at 23 C (MPa) Figure 13. Influence of processing conditions on HAR 2600 2550 2500 900 rpm 2450 1200 rpm 600 rpm 2400 300 rpm 2350 2300 1200 rpm 1200 rpm 2250 600 rpm 600 rpm900 rpm 2200 2150 2100 30 35 40 45 50 55 60 65 70 75 80 Unnotched Charpy impact strength at -30 C (kj/m 2 ) Y, Whiteness D50 sedigraph (µm) D50 laser (µm) Very fine + side feeder HAR + side feeder HAR + main feeder HAR T77 ; HAR 3G 77L HAR T84 ; HAR 3G 84L 77 2.2 10.5 83 2.2 10.5 HAR W92 90 2.2 10.5 HAR s are supplied in densified form (tapped density from 0.6 to 0.8g/cm 3 ) for easy and less costly handling, conveying and feeding. PROCESSING RECOMMENDATIONS Certain precautions have to be taken when compounding HAR s as the exceptional lamellarity of their particles makes them fragile. The use of a side-feeder to introduce the HAR directly into the PP melt is the best method. If HAR is fed into the main hopper with the PP pellets it is micro-milled which lowers mechanical properties such as stiffness, HDT and CLTE. The figure below illustrates the results obtained using different feed sequences on a twin-screw co-rotating extruder. The content in the PP copolymer formulation is 12%. A very fine is used as a reference. The feed sequence has a significant impact on the final results: When fed downstream directly into the PP melt via the side-feeder, HAR demonstrates high stiffness performance compared to the very fine reference : a 12% flexural modulus increase, without impairing impact strength. Redispersion in the polymer matrix is excellent; When HAR is fed upstream with the PP pellets, the flexural modulus is lowered. The decrease is about 200 MPa, i.e. more than 10%. The feed sequence also alters the impact strength which could be due to poorer dispersion; dry friction can create small agglomerates which are difficult to detect using optical microscopy, but which could be sufficient to create weak zones in the composite.

FOR OPTIMAL PERFORMANCE, HAR TALC SHOULD BE INTRODUCED IN THE PP MELT VIA A SIDE-FEEDER For more detailed results, see Guidelines for the processing of High Aspect Ratio (HAR ) filled polypropylene compounds. EXPERIMENTAL DATA Performance in PP General study PP copolymer ExxonMobil 704 PP copolymer 80% Talc content Stabilisation Irganox 1010 Irgafos 168 Calcium stearate CLTE study PP copolymer Sabic P108MF10, MFI (230 C/2.16kg) = 10g/10 min. Processing recommendations: PP copolymer Sabic P108MF10. 20% PP copolymer 90% Talc content Stabilisation Irganox 1010 Irgafos 168 Calcium stearate 10% PP copolymer 88% Talc content Stabilisation Table 4. Table 5. Table 6. Irganox 1010 Irgafos 168 Calcium stearate 12% Processing: The s are compounded using a Coperion Werner & Pfleiderer ZSK 40 Megacompounder twin-screw co-rotating extruder (0 = 40mm, L/D = 48, 300 to 1200 rpm). Standard screw design is used for compounding fillers in PP. Both s are introduced in the PP melt via a sidefeeder so as to obtain optimum performance. Injection moulding was performed on an Arburg press 75T using standard parameters for filled compounds and a mould temperature maintained at 40 C. Mechanical properties: Specimens were tested at Imerys Performance Additives laboratory in Toulouse, France, in accordance with: - Flexural modulus: ISO 178 - CLTE: internal method - Shrinkage: internal method - HDT: ISO 75 A - Notched Charpy impact strength at 23 C (kj m 2 ): ISO 179 1e A - Notched Charpy impact strength at 20 C (kj m 2 ): ISO 179 1e A - Izod impact strength at 23 C: ISO 180 Short glass fibre study Materials used Commercial grades: - PP copolymer: ExxonMobil PPU 0009F - PP homopolymer: ExxonMobil PPU0180F - Short glass fibre: EC 13-968 OCV - Imerys 40µm top-cut - Imerys 10µm top-cut - Imerys HAR T84 - Imerys HAR 3G 84L - Hostanox 03 (): Clariant - Hostanox SE10 (): Clariant - Exxelor P01020: Exxon Mobil (1%) Compounding Twin-screw extruder: Coperion Mega Compounder ZSK 26 Injection moulding press: Billion 140 tonnes Mechanical properties Conditioning before tests: ISO 291 Specimens tested at Imerys Performance Additives laboratory in Toulouse, France, in compliance with: - Flexural modulus ISO 178 - Unnotched Charpy impact ISO 179 - CLTE internal method

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