Extrusion & Post
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PBAT Low Melt Strength, Unstable Blown Film
Problem Phenomenon
During PBAT film blowing, the bubble shakes, breaks holes, and thickness fluctuates; the bubble is hard to stabilize and the yield is low.
Cause Analysis
PBAT tensile strength is only 18MPa and melt strength is low; the bubble easily breaks when subjected to uneven traction and air ring cooling during inflation; insufficient melt strength prevents the bubble from maintaining a stable geometry.
Solution
①Add chain extenders (epoxy-functionalized ADR, toluene diisocyanate) to increase molecular weight and melt strength; ②Blend PLA to increase strength; ③Control melt flow index ≤15g/10min; ④Optimize air ring cooling uniformity.
Key Takeaway
PBAT's low melt strength is the core bottleneck of the film blowing process; chain extender modification is the standard countermeasure; melt index 15g/10min is the flowability upper limit for the blowing process.
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