Differential thermal analysis of the cocrystal peak in linear–high pressure polyethylene blends

A DTA study of over 60 linear–high pressure polyethylene blends is reported. From this study a preliminary phase diagram for this type of system is derived; however, the main emphasis is on the nature of the cocrystal peak. The results appear to indicate that there are two classes of cocrystals in linear–high pressure polyethylene blends with the linear component being responsible for the division of the blends into two groups. The property of the linear component which is responsible for this division is related to the crystallite size of the pure linear crystal. While the division of the blends into two groups is primarily dependent on the linear component, the magnitude of the cocrystal peak height is dependent on the high pressure polyethylene component. Low melt index and low branching of the high pressure polyethylene favor large cocrystal formation. Indeed, resins containing 30 methyls per 1000 carbons do not possess a cocrystal peak.