Irgafos 168

Isotactic polypropylene (iPP) ISPLEN PP080G2M was purchased from Repsol (Madrid, Spain) with a melt flow index of 20 g/10 min at 230 °C and a density of 0.905 g/cm³, being a low viscosity degree suitable for injection molding process. Ethylene–octene copolymer (POE) Engage 8137, with melt flow index (MFI) of 13 g/10 min at 190 °C and a density of 0.864 g/cm³ was purchased from Dow, Midland, USA. This degree was chosen by its easy processability. The used blowing agent was Hydrocerol BIH 40 provided by Clariant. An endothermic blowing agent, it is based on sodium bicarbonate and citric acid. Antioxidants Irgafos 168 (from Ciba, Basel, Switzerland) in a proportion of 0.08 wt.% and Irganox 1010 (from Ciba, Basel, Switzerland) in a proportion of 0.02 wt.% were added to the formulations to prevent thermal oxidation of the polymer during blending.

Dimethyl terephthalate (DMT), 1,4-butanediol (BDO), catalysts tetrabutyl titanate (TBT) and magnesium acetate (MgAc₂) were purchased from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China). CHDM was purchased from Aladdin Reagent Co. Ltd. (Shanghai, China); it was the mixture of 69% trans and 31% cis, and PTMG with an average molar weight of 1000 g mol⁻¹ was supplied by BASF (Shanghai, China). The antioxidants (Irganox 1010 and Irgafos 168) were supplied by Ciba (Basel, Switzerland). All of these chemical materials were dried under vacuum at 80 °C for 24 h to a constant mass before use.