ABSTRACT
Biodegradable biopolymers such as polylactic acid and polybutylene succinate are sustainable alternatives to traditional petroleum-based plastics. However, the factors affecting their degradation must be characterized in detail to enable successful utilization. Here we compared the extruder dwell time at three different melt-spinning scales and its influence on the degradation of both polymers. The melt temperature was the same for all three processes, but the shear stress and dwell time were key differences, with the latter being the easiest to measure. Accelerated degradation tests, including quick weathering and disintegration, were used to evaluate the influence of dwell time on the structural, mechanical, and thermal properties of the resulting fibers. We found that longer dwell times accelerated degradation. Quick weathering by UV pre-exposure before the disintegration trial, however, had a more significant effect than dwell time, indicating that degradation studies with virgin material in a laboratory-scale setting only show the theoretical behavior of a product in the laboratory. A weathered fiber from an industrial-scale spinning line more accurately predicts the behavior of a product placed on the market before ending up in the environment. This highlights the importance of optimizing process parameters such as the dwell time to adapt the degradability of biopolymers for specific applications and environmental requirements. By gaining a deeper insight into the relationship between manufacturing processes and fiber degradability, products can be adapted to meet suitable performance criteria for different applications.
ABSTRACT
Manufacturers of technical polymers must increasingly consider the degradability of their products due to the growing public interest in topics such as greenhouse gas emissions and microplastic pollution. Biobased polymers are part of the solution, but they are still more expensive and less well characterized than conventional petrochemical polymers. Therefore, few biobased polymers with technical applications have reached the market. Polylactic acid (PLA) is the most widely-used industrial thermoplastic biopolymer and is mainly found in the areas of packaging and single-use products. It is classed as biodegradable but only breaks down efficiently above the glass transition temperature of ~60 °C, so it persists in the environment. Some commercially available biobased polymers can break down under normal environmental conditions, including polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT) and thermoplastic starch (TPS), but they are used far less than PLA. This article compares polypropylene, a petrochemical polymer and benchmark for technical applications, with the commercially available biobased polymers PBS, PBAT and TPS, all of which are home-compostable. The comparison considers processing (using the same spinning equipment to generate comparable data) and utilization. Draw ratios ranged from 29 to 83, with take-up speeds from 450 to 1000 m/min. PP achieved benchmark tenacities over 50 cN/tex with these settings, while PBS and PBAT achieved over 10cN/tex. By comparing the performance of biopolymers to petrochemical polymers in the same melt-spinning setting, it is easier to decide which polymer to use in a particular application. This study shows the possibility that home-compostable biopolymers are suitable for products with lower mechanical properties. Only spinning the materials on the same machine with the same settings produces comparable data. This research, therefore, fills the niche and provides comparable data. To our knowledge, this report is the first direct comparison of polypropylene and biobased polymers in the same spinning process with the same parameter settings.