This book provides a necessary bridge between the values ​​of engineering end-use parameters of polyethylene resins and their scientific molecular and structural characteristics. The main goal is to translate such common parameters, such as the melt index of a resin or the dart impact strength of a film sample, into the universal language of polymer science. After this translation is completed, many facets of the resin properties become transparent and easily explainable. The second edition is brought up to date with coverage of new types of catalysts and polymerization processes, and a new section on PE recycling. The chapter on melt indexes is modified and simplified, that on stress cracking has a significant update, and a new chapter on the nature of LLDPE extractables is added.