Structure Characterization And Technology Improvement For The Biaxially Oriented Polypropylene

The biaxially oriented polypropylene (BOPP) film had a good performance and was widely applied in many industrial areas, such as foodstuff, medicine, chemical, tobacco and so on. As known, the process performance of BOPP resin and its film quality mainly depended on its morphological structure. However, the BOPP resin produced by Yangtze petrochemical Co. could not be well used to manufacture the film because its quality was not as good as the abroad ones.Based from analysis of the morphological structure in this work, the resin produced by Yangtze Co. and abroad one were characterized by the methods of temperature degree classification, Gel permeation chromatogaphy and Differential scanning calorimetry to determine their isotacticities and section distributions, molecular distribution, melting behavior and isothermal crystallization rates. The results showed that the essential difference was the abroad BOPP resin had much broad molecular weight distribution with short isotacticity section than our resin.The equipment was then improved, and a practical technology was also suggested. The monomer of ethylene was added in the first reactor to form the copolymer, and hydrogen was added to the following three reactors. As results, the morphological structure of the product was close to that of the abroad with suitable molecular weight distribution, isotacticity and section distribution. The melting behavior, dynamic rheology and mechanical properties of the product were as good as those of the products from abroad. The further application by our customers demonstrated that our resin had much more stable processing property, and the BOPP film qualities were obviously improved.