Gammino Michele, Gioia Claudio, Maio Andrea, Scaffaro Roberto, Lo Re Giada
Department of Engineering, University of Palermo, Viale delle Scienze, Ed. 6, 90128 Palermo, Italy.
Department of Physics, University of Trento, via Sommarive 14, Povo, 38123 Trento, Italy.
ACS Appl Polym Mater. 2024 May 13;6(10):5866-5877. doi: 10.1021/acsapm.4c00514. eCollection 2024 May 24.
Biosourced and biodegradable polyesters like poly(butylene succinate--butylene adipate) (PBSA) are gaining traction as promising alternatives to oil-based thermoplastics for single-use applications. However, the mechanical and rheological properties of PBSA are affected by its thermomechanical sensitivity during its melt processing, also hindering PBSA mechanical recycling. Traditional reactive melt processing (RP) methods use chemical additives to counteract these drawbacks, compromising sustainability. This study proposes a green reactive method during melt compounding for PBSA based on a comprehensive understanding of its thermomechanical degradative behavior. Under the hypothesis that controlled degradative paths during melt processing can promote branching/recombination reactions without the addition of chemical additives, we aim to enhance PBSA rheological and mechanical performance. An in-depth investigation of the in-line rheological behavior of PBSA was conducted using an internal batch mixer, exploring parameters such as temperature, screw rotation speed, and residence time. Their influence on PBSA chain scissions, branching/recombination, and cross-linking reactions were evaluated to identify optimal conditions for effective RP. Results demonstrate that specific processing conditions, for example, twelve minutes processing time, 200 °C temperature, and 60 rpm screw rotation speed, promote the formation of the long chain branched structure in PBSA. These structural changes resulted in a notable enhancement of the reacted PBSA rheological and mechanical properties, exhibiting a 23% increase in elastic modulus, a 50% increase in yield strength, and an 80% increase in tensile strength. The RP strategy also improved PBSA mechanical recycling, thus making it a potential replacement for low-density polyethylene (LDPE). Ultimately, this study showcases how finely controlling the thermomechanical degradation during reactive melt processing can improve the material's properties, enabling reliable mechanical recycling, which can serve as a green approach for other biodegradable polymers.
聚（丁二酸丁二醇酯-己二酸丁二醇酯）（PBSA）等生物基可生物降解聚酯作为一次性应用中油基热塑性塑料的有前途的替代品正越来越受到关注。然而，PBSA的机械和流变性能在其熔融加工过程中会受到热机械敏感性的影响，这也阻碍了PBSA的机械回收。传统的反应性熔融加工（RP）方法使用化学添加剂来抵消这些缺点，从而损害了可持续性。本研究基于对PBSA热机械降解行为的全面理解，提出了一种在熔融共混过程中对PBSA进行绿色反应性加工的方法。在不添加化学添加剂的情况下，通过控制熔融加工过程中的降解路径可以促进支化/重组反应这一假设下，我们旨在提高PBSA的流变和机械性能。使用内部间歇式混合器对PBSA的在线流变行为进行了深入研究，探索了温度、螺杆转速和停留时间等参数。评估了它们对PBSA断链、支化/重组和交联反应的影响，以确定有效RP的最佳条件。结果表明，特定的加工条件，例如12分钟的加工时间、200°C的温度和60 rpm的螺杆转速，可促进PBSA中长链支化结构的形成。这些结构变化导致反应后的PBSA流变和机械性能显著提高，弹性模量提高了23%，屈服强度提高了50%，拉伸强度提高了80%。RP策略还改善了PBSA的机械回收性能，从而使其成为低密度聚乙烯（LDPE）的潜在替代品。最终，本研究展示了如何在反应性熔融加工过程中精细控制热机械降解，从而改善材料性能，实现可靠的机械回收，这可以作为其他可生物降解聚合物的绿色方法。
