Acrylonitrile-butadiene-styrene photooxidation

During weathering, phenolic antioxidants are photooxidized into hydroperoxycy-clohexadienones, such as 59 (Pospisil, 1993 Pospisil, 1980). The presence of peroxidic moieties in 57 and 59 renders them thermolabile at temperatures exceeding 100 °C and photolysable under solar UV radiation. Both processes account for homolysis of the peroxidic moieties. As a result, the oxidative degradation of the polymeric matrix is accelerated by formed free-radical fragments (tests were performed with atactic polypropylene and acrylonitrile-butadiene-styrene terpolymer (ABS) (PospiSil, 1981 PospiSil, 1980). Low-molecular-weight products of homolysis, such as 60 to 63 are formed in low amounts. 

After the examination of the PS photooxidation mechanism, a comparison of the photochemical behavior of PS with that of some of its copolymers and blends is reported in this chapter. The copolymers studied include styrene-stat-acrylo-nitrile (SAN) and acrylonitrile-butadiene-styrene (ABS). The blends studied are AES (acrylonitrile-EPDM-styrene) (EPDM = ethylene-propylene-diene-monomer) and a blend of poly(vinyl methyl ether) (PVME) and PS (PVME-PS). The components of the copolymers are chemically bonded. In the case of the blends, PS and one or more polymers are mixed. The copolymers or the blends can be homogeneous (miscible components) or phase separated. The potential interactions occurring during the photodegradation of the various components may be different if they are chemically bonded or not, homogeneously dispersed or spatially separated. Another important aspect is the nature, the proportions and the behavior towards the photooxidation of the components added to PS. How will a component which is less or more photodegradable than PS influence the degradation of the copolymer or the blend We show in this chapter how the... 

The rubber-modified aromatic polymeric materials, for example, high-impact polystyrene (HIPS) and acrylonitrile-butadiene-styrene (ABS) are the least stable because of the rapid photooxidation of the rubber component, which sensitizes the polymer to further oxidation. Diene-based rubbers are also susceptible to degradation by ozone, which causes chain scission of the main-chain... 

Evaluation of IR spectra of acrylonitrile-butadiene-styrene (ABS) after UV irradiation shows that rubber double bands at 965 cm and 910 cm (Fig. 3.65), attributed to poly(trans-l,4-butadiene) and poly(l,2-butadiene), respectively, decrease with exposure time (Fig. 3.66) in a first order reaction, together with the carbon-carbon double stretching band at 3450 cm in addition, a saturated carbonyl band (centred at 1725 cm ) forms (Fig. 3.65) by a first order process (Fig. 3.67). During the initial stages of the photooxidation, bands at 1665, 1685 and 1699 cm due to a- and ) -unsaturated carbonyl groups, develop [1113,1936]. 

Several studies of the spatial resolution of oxidation processes in HAS stabilized polymer appeared since the pioneering paper [25] and deal with events in PP [26 - 28] or commercial poly(acrylonitrile-co-butadiene-co-styrene) (ABS) copolymer plaques with thickness from 2 to 6 mm [27, 29], We preferred for our experiments plaques of 6 mm thickness providing more detailed information on the spatial distribution of nitroxides in both thermal and photooxidative stress situations [28],... 

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