Study On Structure And Properties Of PC/AES Blends Compatibilized By Styrene-maleic Anhydride Copolymers

Polycarbonate/Acrylonitrile-ethylene-propylene-diene-styrene(PC/AES) blends are widely used as high-performance thermoplastics with good flow properties, excellent mechanical properties and high weather resistance. However, the defect that PC/AES blends exhibit rapid phase coarsening at an elevated temperature restricts its application. Efforts have been made to overcome the limitation of PC/AES blends by addition compatibilizer to it. Blends of PC/AES were reactive compatibilized by styrene-maleic anhydride copolymers(SMA). The changes in phase morphology and interfacial characteristics of the blends as a function of maleic anhydride content of SMA and the concentration of compatibilizer have been systematic studied.The occurrence of reaction between the terminal hydroxyl groups of PC and the maleic anhydride(MA) of compatibilizer was confirmed by Fourier Transform Infrared(FTIR) spectroscopy. Differential scanning calorimeter(DSC) thermograms showed that the gaps between two glass transition temperatures corresponding to the constituent polymers decreased with increasing SMA content. A glass transition temperature(Tg) with an intermediate value between Tg(AES) and Tg(PC) was found on DSC curves of PC/AES blends compatibilized with SMA contains high levels of maleic anhydride. Furthermore, when added appropriate amount of such SMA, the blend had only one Tg, meaning that the blend became more compatible. But SMA concentration exceeds optimum level, evidence for less partial compatibility was found. The reasons that account for this unusual phenomenon are discussed. Small Angle X-ray Scattering(SAXS) test results indicated that the thickness of the interface layer changed with the variation of the compatibilizer concentration. The compatibilizer concentration for the minimum of blend interface layer’s thickness was exactly the same as it was when compatibilized PC/AES blend exhibited optimal compatibility in DSC test. The observed morphological changes were consistent well with the DSC and SAXS test results. Due to SMA with higher MA functional group content needs more hydroxyl terminated groups to fully react with it. Thus, at the same compatibilizer level, the addition of SMA with higher MA functional group content leads to more chain interactions on interface layer than SMA with lower MA functional group ones. A new mechanism of interfacial structural development was proposed to explain unusual phenomena of SMA compatibilized PC/AES blends. Annealing experiments results confirm that SMA acts as a compatibilizer and as should be minimizes coalescence of the AES domains. This might be due to the in situ formed compatibilizer affects the AES domains interface mobility and thereby hinders the AES coalescence and stabilizes the dispersions to the fine morphology during processing.