ABSTRACT
Although different polymeric film market segments have different performance requirements, the properties of the films depend upon the molecular architecture, microstructure, molecular orientation and crystallinity, developed according to the chosen processing tools and conditions. Therefore, knowledge of developed microstructure is of great scientific and technological interest. In this study, it was studied the correlation between molecular orientation, crystallinity and water vapor and oxygen permeability properties of biaxially oriented linear low-density polyethylene (LLDPE) films obtained by planar extrusion and stretched by different stretch rations. The molecular orientation study revealed morphological structure changing of chains in the crystalline fraction of the films submitted to higher degrees of stretching. Results of degree of crystallinity of LLDPE films evidenced a tendency to increase crystallinity with increasing orientation of the polymer chains, due to stretching. Results of barrier properties showed the increase of the degree of stretching has a moderate effect on the decrease of permeability to oxygen and water vapor of the LLDPE films, and that this behavior is related to the degree of stretching and crystallinity of the films.
Keywords:
Linear low-density polyethylene; Molecular orientation; Permeability; Crystallinity
