Improving foamability and foam stability of poly(ethylene terephthalate) through chemical modification with styrene maleic anhydride

Abstract

AbstractThis study aimed to enhance the melt strength, foamability, and microstructural properties of poly(ethylene terephthalate) (PET) foam by addition of styrene maleic anhydride (SMA) as a chain extender. The addition of SMA to the polymer increased the complex viscosity by 375%. The calculated dissipation factor for chain‐extended‐PET (CE‐PET) samples demonstrated a rise in polymer viscous behavior with increasing SMA content. The CE‐PET was more elastic than pure PET. Smaller oval‐shaped cells were produced with lower amounts of foaming agent/SMA, whereas higher ratios resulted in larger spree‐shaped cells. The reaction of SMA anhydrides with the end functional groups of the PET chains increased the chain length significantly followed by more entanglement. This behavior prevented cell growth during the foaming process. The confrontation between the physical and chemical forces among the PET chains and the gas pressure created by the foaming agent was the main mechanism of cell growth in the polymer matrix. This variation caused a 30% reduction in foam density. Statistical analysis revealed that CE‐PET foams with the largest cell size and lowest density were achieved with foaming agent amounts between 0.9 and 1.4 wt.% and SMA amounts between 4.7 and 7.3 wt.%.