Acrylonitrile butadiene styrene impact strength

Acrylonitrile-butadiene-styrene Impact strength, processability. HDT... 

Polycarbonate is blended with a number of polymers including PET, PBT, acrylonitrile-butadiene-styrene terpolymer (ABS) rubber, and styrene-maleic anhydride (SMA) copolymer. The blends have lower costs compared to polycarbonate and, in addition, show some property improvement. PET and PBT impart better chemical resistance and processability, ABS imparts improved processability, and SMA imparts better retention of properties on aging at high temperature. Poly(phenylene oxide) blended with high-impact polystyrene (HIPS) (polybutadiene-gra/f-polystyrene) has improved toughness and processability. The impact strength of polyamides is improved by blending with an ethylene copolymer or ABS rubber. 

Acrylonitrile-Butadiene-Styrene (ABS) Copolymers. This basic three-monomer system can be tailored to yield resins with a variety of properties. Acrylonitrile contributes heat resistance, high strength, and chemical resistance. Butadiene contributes impact strength, toughness, and retention of low-temperature properties. Styrene contributes gloss, processibility, and rigidity. ABS polymers are composed of discrete polybutadiene particles grafted with the styrene-acrylonitrile copolymer these are dispersed in the continuous matrix of the copolymer. 

Acrylonitrile-Butadiene-Styrene ABS) is sometimes a terpolymer of three monomers, but in most cases a blend of two copolymers. ABS has an excellent impact strength and a relatively high softening temperature (about 110 °C). Its stiffness is only marginally lower than that of PS. It finds large-scale applications in the automotive industry, in toys, telephones, TV-housings, etc. 

We have just discussed several methods for improving the mechanical properties of polymers. In addition to these techniques, one could think about synthesizing copolymers of styrene and less brittle monomer(s). Actually, we have already seen that this approach has been used with considerable success (see Chapter 5 and Table 5-2). Styrene-acrylonitrile (SAN) copolymers and acrylonitrile-butadiene-styrene (ABS) terpolymers have excellent impact strength. Although sometimes copolymerization is a viable option, oftentimes a completely different approach is called for. Let s see how. 

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. 

HIPS) is produced commercially by the emulsion polymerization of styrene monomer containing dispersed particles of polybutadiene or styrene-butadiene (SBR) latex. The resulting product consists of a glassy polystyrene matrix in which small domains of polybutadiene are dispersed. The impact strength of HIPS depends on the size, concentration, and distribution of the polybutadiene particles. It is influenced by the stereochemistry of polybutadiene, with low vinyl contents and 36% d5-l,4-polybutadiene providing optimal properties. Copolymers of styrene and maleic anhydride exhibit improved heat distortion temperature, while its copolymer with acrylonitrile, SAN — typically 76% styrene, 24% acrylonitrile — shows enhanced strength and chemical resistance. The improvement in the properties of polystyrene in the form of acrylonitrile-butadiene-styrene terpolymer (ABS) is discussed in Section VILA. 

Impact modifiers are added primarily to PVC, polyethylene, polypropylene, polyamides and polyesters. They absorb the energy generated by impact and dissipate it in a non-destructive way. Impact modifiers are physically rubbery and semi-compatible with the polymer. The mechanism of absorbing impact in polymers is not fuUy understood, but these additives increase the tensile strength of the material. The impact modifiers most commonly used include acrylonitrile-butadiene-styrene (ABS) polymers, acrylics and ethylene-vinyl acetate (Carraher, 2000). ABS generates opacity or stress-whitening when used as... 

Fig. 7.1 Photodegradation of an acrylonitrile/butadiene/ styrene (ABS) copolymer at 30 °C. Plot of the impact strength I s. the simulated natural exposure time (xenon-arc radiation, 0.55 W m at 340 nm). Adapted from Davis et al. [45] with permission from Elsevier.

Styrene-acrylonitrile copolymers are produced commercially for use as structural plastics. The typical acrylonitrile content in such resins is between 20-30%. These materials have better solvent and oil resistance than polystyrene and a higher softening point. In addition, they exhibit better resistance to cracking and crazing and an enhanced impact strength. Although the acrylonitrile copolymers have enhanced properties over polystyrene, they are still inadequate for many applications. Acrylonitrile-butadiene-styrene polymers, known as ABS resins, were therefore developed. 

PTT/ABS Acrylonitrile-butadiene-styrene (ABS) is associated with good processability, dimensional stability, and high impact strength at lower temperatures. (Xue et al., 2007)... 

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