The major uncertainty of methods such as DSC is that some knowledge of the values of a given property (e.g.,density or heat of fusion) of the 100% crystalline polymer must be assumed. Furthermore it is usually assumed that this property varies linearly with both the degree of crys-tallinity and the copolymer composition. This is invalidwhere co-crystallization occurs [228]. “The borderline of copolymer composition between isomorphism and latticedefects is ambiguous.” [229].