Effect of Foaming Temperature on Microstructure, Mechanical Properties and Flame Spread Rate in PET–PEN Copolymer

Polymer foams are expanding their applications into functional materials. Partial foam structure has been fabricated in polyethylene terephthalate–polyethylene naphthalate (PET–PEN) copolymer by solid state foaming. Through SEM image analyses, a potential to fabricate gradient structures with micropores and unfoamed skin layers identified. The post-foaming temperature Tf tune the pore size distribution. Radial distribution of micromechanical properties, indentation hardness elastic modulus were measured for partial values around 0.12 GPa 2.0 GPa, respectively, outer foamed region. Foaming affects glass transition Tg, coefficient thermal expansion flame spreading rate. For range ≤ 60°C, coefficients T > Tg about 0.5 m/m°C (steep group, SEG). When is above 80 °C, they 0.02 (mild MEG). burning rate SEG 2.8 times higher than that MEG.