ASA Blends

Blends of ASA with many of the common thermoplastic materials are state of the art. The properties of the finished products depend to a large extent on the polymer compatibility often induced by the use of reactive polymers. Only a few of these blends have reached a significant commercial status. The largest blend products in this area are ASA-PC blends followed by ASA-PBT and ASA-PC-PMMA blends. Combinations of ASA with high-Tg matrix polymers are also frequently found in commercial products. 

Although polycarbonate is an engineering thermoplastic material which provides high toughness, flexibility and thermal stability, it suffers from certain limitations due to poor chemical resistance and low flow characteristics in injection moulding. These shortcomings can be circumvented by blending PC 

The improved flowability of ASA-PC blends was addressed by Yu [68], by suggesting the use of a three-stage impact modifier, consisting of an acrylate core that is covered by a first shell of crosslinked PSAN and a further shell comprised of linear PSAN. These blends, while retaining the impact properties of the material, exhibit an improved flowability by a factor of 3. 

Another option in improving the flowability of these blends is the use of a branched polycarbonate. Brandstetter et al. [69] found that a dianhydride branched polycarbonate combined with ASA can be injection moulded at temperatures 5-10 K lower than similar blends based on linear polycarbonates. 

Increased toughness and colourability over conventional ASA-PC blends can be attained by using a two-stage grafted n-butyl acrylate core [70]. In the first grafting step pure styrene is added followed by a styrene-acrylonitrile 

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H.F. Giles, Jr. and W.R. Schlich, Polyetherimide-ASA blends, US Patent 5 070 142, assigned to General Electric Company (Pittsfield, Mass.), December 3,1991. 

To improve the notched impact strength and to prevent hydrolysis induced embrittlement of PBT, PBT-styrenic blends have been thoroughly investigated. In comparison with ASA-PC, blends of ASA and PBT generally have to be compa-tibilized in order to yield acceptable mechanical properties. In the case of glass fibre reinforced PBT-ASA blends, an added and important bonus is reduced warpage properties on injection moulding in comparison with reinforced PBT. 

An ASA-PBT with improved hydrolysis resistance and reduced warp was reported for a resin composition containing a difunctional epoxy compound such as bis(3,4-epoxycyclohexylmethyl) adipate [81]. To increase the heat distortion temperature of a PBT-ASA blend by 10-20°C, the addition of talc at a... 

In order to make parts by means of the PFM technology, the co-extruded film is thermoformed and then backmoulded with a compatible thermoplastic. Alternatives for the backmoulding material include, for example, ABS (without or with glass fibre reinforcement) and glass fibre reinforced PBT ASA blends. 

The most important commercial blends of BPA-PC are poly(acrylonitrile-butadiene-styrene) (PC/ABS) and polybutylene terephthalate (PC/PBT) or polyethylene terephthalate (PET). Commercial grades of PC/ABS include CYCOLOY (GE), Bayblend (Bayer), and PULSE (Dow). PC/ABS blends exhibit improved flow and processability and enhanced low-temperature impact strength in comparison to PC (Fig. 3). These blends are widely used in applications requiring enhanced impact resistance, such as interior automotive parts and computer and electronics applications such as computer housings and cell phones. Non-halogenated flame-retardant PC/ABS blends are widely available. Poly(acrylic-styrene-acrylonitrile) (PC/ ASA) blends (GELOY , GE Luran , BASF) provide improved weatherability for outdoor applications such as exterior automotive parts, but exhibit reduced impact performance at low temperatures in comparison to PC/ABS. PC/PBT or PET blends (XENOY , GE Makroblend , Bayer) provide enhanced chemical resistance and weatherability for applications such as lawn and garden equipment and automotive bumpers and fasdas. 

A PC/ASA blend is used on exterior parts such as the cowl vent grilles, trim, front grilles, head lamp bezels, pillars, license plate brackets and window surrounds. The prime advantage of this weatherable alloy is the elimination of painting, which reduces process solvent emissions. 

Bayer and BASF have developed a PC/ASA blend where ASA is the rubber variant of ABS in which the polybutadiene phase is completely replaced by a polyacrylate rubber. Compared to PC/ABS alloys, the PC/ASA blend has greater resistance to weathering, which permits outdoor applications and an extra heat stability that reduces the risk of yellowing in processing. BASFs alloy, Terblend S, is recommended for outdoor applications as it has six times the UV resistance of PC/ABS and an even higher resistance when pigmented. 

Figure 4.155 Tensile strength vs. temperature for BASF Ultradur S4090—low warpage PBT/ASA blend polyester alloy/ blend resins.

Figure 4.157 Dielectric constant vs. frequency at 23°C for BASF Ultradur S4090 G4—low warpage PBT/ASA blend, 20% glass fiber polyester alloy/blend resin.

Liu et al. (2011a) prepared compatibilized PBT-ASA blends by addition of epoxy resin coupling agent. Blends were characterized by mechanical properties and morphology (TEM and FESEM). 

Hence, ASA and ASA blends are primarily used in the automotive/ transportation, recreational and agricultural vehicle parts requiring long outdoor... 

Ultrablend S PBT/SAN, ABS, or ASA blends, with up to 30 wt% glass fiber BASF Plastics... 

The weathering stabilities of polycarbonate, ABS and/or ASA blends are comparable to those of their blend partners, i.e., polycarbonate and ABS and/or ASA follow their specific reaction mechanisms [665],... 

PVC/ABS has also been used for weather-resistant profile capstocks. A useful grade is Blendex 131 (35 percent PB), which is also suitable for footware, film, and sheet. Dark-colored capstock often uses acrylate-styrene-acrylonitrile (ASA) blends with PVC. Somewhat better heat distortion characteristies are typieal. A common grade is Amsan 587 (Chemtura), which is also available as a ground powder (587s). Another is Geloy 1226 (GE Polymerland). 

PVC /ABS and PVC/ASA blends are widely available from custom compounders and polymer suppliers, including Novatec, A. Schulman, Solvay, ComAlloy, Shuman, PolyOne, Denka, AlphaGary, Georgia Gulf, and Sparteeh. This is particularly useful if they must contain conductive carbon black, for example, to aid electrodeposition of metallic coatings. An example is Royalite R63 (Sparteeh). 

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