The adoption of biodegradable plastics faces an often-underestimated processing bottleneck: insufficient melt strength. PLA, for example, tends to neck and tear under extensional flow, causing unstable bubbles in film blowing, coalescing cells in foaming and sagging parisons in extrusion — limiting product forms and production efficiency.

Melt strength reflects a melt's resistance to deformation under extensional flow, closely related to molecular weight, molecular weight distribution and long-chain branching. Linear thermoplastic polyesters with low or broad molecular weight lack strain hardening under extension, resulting in weak melt strength.

Chain extenders offer a direct and effective route: chain extension raises molecular weight and introduces branching, enhancing strain hardening and markedly improving forming stability in film blowing, foaming and casting. Chain extension also repairs processing-induced degradation, helping materials retain usable performance over multiple processing cycles.

In practice, the dosage, reaction temperature and residence time must match the processing equipment. Insufficient reaction limits improvement; excessive reaction risks gel spots that affect film appearance and mechanical uniformity. Confirming the process window from laboratory trials to industrial commissioning is standard practice in biodegradable material modification projects.

For biodegradable product manufacturers, incorporating chain extension into the formulation system is a cost-effective way to widen product forms and improve processing efficiency without significantly increasing cost.