ASA resin

ASA resin is a terpolymer formed by graft polymerization of acrylonitrile and styrene onto acryl rubber, and it is opaque. By adjusting the composition of acrylonitrile, acryl rubber, and styrene and the grafting ratio, a resin having high impact strength and excellent fluidity in molding can be prepared. 

In comparison to ABS resin, ASA resin has somewhat greater specific gravity, somewhat less tensile strength, and somewhat greater elongation. The other properties of ASA are comparable to those of ABS. 

For weatherability it has been reported that after outdoor exposure of ASA resin, there is extremely little deterioration of the mechanical properties such as impact and elongation, and there is substantially no change in appearance. ASA resin can endure the conditions of outdoor use for a long time in comparison to the general-purpose resin. 

ASA resin has been sold as the flame-retardant grade and finer glass-reinforced grade, which can be used in broad applications. ASAresin has seen use in substantially the same application fields as ABS resin, and particularly has been developed mainly for the outdoor product which demands the weatherability  

Fields related to electricity switch case, housing (washing machine, refrigerator, ventilator, pump, room cooler, etc.), fluorescent lamp, mercury lamp cover, antenna cover, door horn, metacover 

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The most widely utilized method to improve the appearance properties of an ASA resin, is to blend the ASA resin with a second resin, which can supplement the weak properties of former resin. 

Blends of polycarbonate with other styrenic resins are relatively new and therefore their current market volume is low. They have been developed primarily to upgrade the performance of such styrenic resins as styrenic-maleic anhydride (SMA), styrene-methyl methacrylate (S-MMA), acrylic-sty-rene-acylonitrile (ASA) resins primarily for impact strength and to some extent for DTUL improvement (Tables 15.7, 15.8 and 15.23). These blends uniquely combine high notched Izod impact strengths (ranging from 500 J/m to > 1000 J/m) with better UV resistance or weatherability than ABS. 

ASA resins are available in natural, off-white, and a broad range of standard and custom-matched colors. ASA resins can be compounded with other polymers to make alloys and compounds that benefit from ASA s weather resistance. 

Figure 2.41 Tensile stress vs. strain for Styrolution Luran S 757 R—general purpose molding grade ASA resin.

Figure 2.44 Stress vs. strain in compression for SABIC Innovative Plastics Geloy CR7520—high impact automotive ASA resin.

Figure 2.45 Shear modulus vs. temperature for Styrolution Luran ASA resins.

Figure 2.46 Flexural modulus vs. temperature for SABIC Innovative Plastics Geloy ASA resins.

The primary rationale for developing the ASA/polyamide blends is to combine the high UV resistance of ASA resins with high heat and solvent resistance properties of the common semicrystalline polyamides such as PA6. The compatibUization of the ASA/PA6 blends uses the same technical approach as for the ABS/PA6 blends, viz., the use of a maleic anhydride-modified (copol5mierized) SAN copolymer as a polyamide-reactive compatibilizer as discussed before under the ABS/PA blends... 

ASA resins are available for blow molding, extrusion, and injection molding. ASA resins are also blended with polycarbonate, polyvinyl chloride, and acrylonitrile ethylene styrene for specific property enhancements. The main suppliers are BASF (Luran and Centrex), BP Chemicals (Barex), Bayer (Centrex), LG Chemical (LI and LE polymers), and GE (Geloy). 

The representative resin includes ASA resin using acryl rubber instead of butadiene rubber and AES resin using EPDM rubber. Those resins are for use outdoors without postprocessing such as painting and metal plating and have been reported to have comparable properties, moldability, and weatherability. 

Therefore, at present the demand for ASA as the weatherable resin is great all over the world. Moreover, recently ultraweatherable ASA resins having heat resistance and surface properties, processabihty and weatherabihty are being developed. 

ASA resin exhibits somewhat low impact strength and significantly deteriorated staining properties compared to ABS resin. Therefore, ASA resin has limited use. However, the product has far superior weatherability while maintaining the advantages of ABS resins, as they are recently developed by multilayer structure technology. 

In the 1980 s GE acquired worldwide rights to Stauffer s ASA resins, which were one of the most weather resistant polymers available, and on their base developed Geloy resin family. COMPOSITION... 

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