Effect of Processing Conditions on Process‐Induced Degradation of Poly(Lactic Acid) During Single‐Screw Extrusion

• Published in: Journal of applied polymer science 2025-01
• Main Authors: Velghe, Ineke, Buffel, Bart, Vandeginste, Veerle, Thielemans, Wim, Desplentere, Frederik
• Format: Article
• Language: English
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.56698

The aim of this study is to investigate the effect of processing conditions on the degradation of poly(lactic acid) (PLA) during single‐screw extrusion. A 2 5 full factorial design of experiments was used to systematically screen significant main and interaction effects caused by five processing conditions: the moisture content in the granules (dried–undried), processing temperature (190°C–230°C), length of the compression zone of the screw (6D–11D), diameter of the capillary die (2–4 mm), and screw rotation speed (20–40 rpm). The effect of 32 extrusion combinations on the molecular weight of PLA (102,850 Da) was statistically analyzed. The molecular weight after processing varied between 100,750 and 66,500 Da and was determined by four main effects and three interaction effects. A high moisture content had the largest effect (−17,846 Da), followed by a high processing temperature of 230°C (−7260 Da), a small die diameter of 2 mm (−1849 Da) and a low screw rotation speed of 20 rpm (−4730 Da). Aside from main effects, the importance of studying interaction effects was emphasized, since the moisture content influenced degradation caused by temperature (−4019 Da), screw speed (4621 Da), and die geometry (1993 Da).