Structure evolution during film blowing: An experimental study using in-situ small angle X-ray scattering

• Unique in-situ SAXS study during film blowing of a series of LLDPE performed.
• Effect of processing conditions and material on morphological features investigated.
• BUR influences crystallinity and lamellar thickness evolution, TUR orientation.
• Crystallinity increases of 50% above frost line due to secondary crystallization.
• Validation of the on-line study using ex-situ WAXD/SAXS.

The on-line morphological development during film blowing of 2 different linear low density polyethylenes (LLDPEs) and a blend of LLDPE with low density polyethylene (LDPE) has been investigated, for the first time, using synchrotron Small Angle X-ray Scattering (SAXS). The processing conditions, blow-up ratio and take-up ratio, have been varied and the resulting lamellar thickness, linear crystallinity and orientation evolution in machine direction is obtained from a detailed analysis of SAXS data. Ex-situ SAXS and wide angle X-ray Diffraction (WAXD) confirmed the effect of molecular structure and composition on structure evolution observed in the on-line experiments. The results obtained provide a valuable set of data for the understanding of the film blowing process and can be used to extend and improve numerical model.

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