Two biodegradable polymers (polylactic acid (PLA) and polybutylene succinate (PBS)) were mixed with ultraviolet absorbers and hindered amine light stabilizers to improve the durability of this composite fiber outdoors. Filament was obtained from this composite material under the optimum conditions by using melt spinning to investigate the effects of spinning temperature, spinneret rotation speed and take-up roller speed in the fiber spinning process on the quality characteristics of newly spun threads. The response surface method was used to build a regression model for different quality characteristics. Moreover, multi-objective particle swarm optimization was applied to optimize the model of these quality characteristics and parameter limits. According to experimental validation, the composite material of PLA/PBS was better than the composite material of PLA/polycaprolactone. The denier of the composite fiber obtained under the optimized conditions was 40.07 d, with an increase of 5.3% compared to the denier before optimization. The fiber strength after optimization was 1.69 (g/d), with an increase of 42%. The breaking elongation was 176.04% and increased 27% after optimization. The prediction error rate of an optimum regression model showed that the model has good reproducibility.

This study aims to develop dyeable modified polypropylene (PP) granules with disperse dye. The optimal dyeable modified PP granule process used polyester as a mixed copolymer. The purpose was to overcome the excessive difference between the polyester material melting point and PP melting point. The development of a low-melting modified co-polybutylene adipate terephthalate (Co-PBAT) was the key point. After the low-melting modified Co-PBAT was presented, PP and a PP grafting maleic anhydride compatibilizer were made into a composite by dual-screw mixing process. The disperse dye dyeability was reached by the molecular behavior of the Co-PBAT chain segment. The prepared material was applied to explore the thermal properties of modified ester pellets and the functional group was verified by Fourier infrared spectroscopy. In this study, the Taguchi method and principal component analysis were used to optimize the process parameter design of two quality characteristics; namely, the color strength and the polymer melt flow index (MFI). According to the results, the multi-quality optimization of the ester pellets consisted of a modified Co-PBAT melting point of 170°C, the modified Co-PBAT content of 9 wt%, the compatibilizer content of 3 wt%, and the mixing temperature of 205°C. The MFI of the regular PP polymer was 28.1 g/10 min, the color strength was 100 K/S. For the optimal process, the MFI of the PP/Co-PBAT dyeable granules was 37.88 g/10 min, and the color strength was 121.31 K/S. It could be observed that the developed polymer had good circulating workability and color strength.