In situ copolymerization and compatibilization of polyester and polystyrene blends. II. Thermally and chemically induced reaction and mechanical properties

The basic studies of in situ compatibilization process between polystyrene (PS) and polybutylene terephthalate (PBT) are carried out by adding various functionalized polystyrenes with mono, di, tetra hydroxy functions. The te nsile mechanical properties of these in situ compatibilized blends are inve stigated. It is important to control the thermal degradation of PET during the high temperature processing in order to generate the reaction between t he functionalized polystyrene and PET and result in the improvement in thei r mechanical properties. However, the excess degradation deteriorates the t ensile properties of the in situ copolymerized and compatibilized polymer b lends. It is found that the usage of Titanium butoxide (TNBT) was effective to promote the thermal degradation of PET and the copolymerization of PET with the functionalized polystyrenes. On the other hand, Triphenyl phosphit e (TPP) was used to prevent the excess thermal degradation and induce the p ossible end capping reaction of PET. The addition of 5% PS-FLC (tetra funct ionalized polystyrene) in PS/PBT 10/90 blend at 270 degreesC with 1% TPP ex hibits the best improvement in the elongation at break among the mono-, di- and tetra-functionalized polystyrenes. The increase of amount of the funct ionalized polystyrenes into the PS/PBT blends decreased the elongation to b reak, the yield strength, and the energy to break. More functional groups i n the functionalized polystyrenes are more effective in promoting in situ c ompatibilization. Furthermore, the one-step mixing in which all the ingredi ents were blended together for 10 min has better elongation to break than t he two steps mixing. The detailed characterization of rheological, morpholo gical and mechanical properties of various blends of functionalized PS/PBT and PS/PBT with different functionalized polystyrenes and the additives are described. (C) 2001 Elsevier Science Ltd. All rights reserved.