Abstract
Herein, acrylonitrile-styrene-acrylate copolymer (ASA) particles with different microstructure were synthesized by emulsion polymerization and then used for toughening poly(styrene-co-acrylonitrile) (SAN) resin. The structure of ASA particles was confirmed by FTIR. TEM results demonstrated that the particles with different morphologies of multilobe shape, complete core-shell and dumbbell shape were obtained depending on the cross-linker amount. It was found that the toughening efficiency reached the highest when the ASA particles had complete core-shell structure and the shell composition was close to that of the SAN matrix. It was ascribed to the fact that the complete shell layer and similar shell composition provided sufficient interfacial adhesion and transferred stress to induce larger matrix deformation, so that the notched impact strength increased accordingly. Moreover, the notched impact strength of SAN/ASA blend was improved without significantly sacrificing tensile strength when adding 30 wt% ASA particles with the size of around 400 nm. SEM results of the impact-fractured surfaces revealed that irregular fluctuation and numerous microvoids occurred. It was deduced that the toughening mechanism was attributed to the crazings and cavitation of particles. Therefore, this study paved a way of toughening the resin by adjusting the microstructure of the particles including morphology, composition, and size.
Highlights
Poly(styrene-co-acrylonitrile) (SAN) is one of the most important thermoplastic materials fabricated by copolymerization of styrene (St) and acrylonitrile (AN), which has high rigidity, chemical and solvent resistance, and excellent processing properties [1,2,3]
The microstructure of acrylonitrile-styrene-acrylate copolymer (ASA) particles discussed in this part consisted of two aspects: one was the morphology and the other was shell composition
ASA particles with different morphologies and various shell compositions were prepared via seeded emulsion polymerization
Summary
Poly(styrene-co-acrylonitrile) (SAN) is one of the most important thermoplastic materials fabricated by copolymerization of styrene (St) and acrylonitrile (AN), which has high rigidity, chemical and solvent resistance, and excellent processing properties [1,2,3]. Chlorinated polyethylene (CPE) elastomer, which was an impact modifier for brittle materials, was melted with SAN resin, but it did not cause a drastic increase in impact strength or elongation at break because of the immiscibility between the two components [6]. CPE is prone to decompose at the processing temperature of SAN resin. Modified ethylene–propylene–diene terpolymer prepared by solution polymerization was introduced to toughen SAN resin [7, 8], a mass of solvent was used here, and the product conversion rate was low [9]. It was generally accepted that adding acrylonitrilebutadiene-styrene copolymer (ABS) was a successful and efficient way to toughen SAN resin [10, 11]. The double bonds (C=C) in polybutadiene (PB) rubbery core of ABS particles are prone to deterioration and cross-linking due to oxygen, ultraviolet (UV), and other severe environmental circumstances, which results in poor aging resistance, weatherability, and antidiscoloration [12, 13]
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