High modulus polyethylene fibres, both melt and gel-spun, contain the same
longitudinal density deficient regions, revealed by permanganic etching, as
were found in specimens of the same fibres after treatment by the Leeds hi
gh temperature compaction process. For these materials a new model of fibre
structure is proposed, which develops as a consequence of nucleation on an
extended network of entangled molecules permeating the fibres. Subsequent
growth into spaces between the network will encounter stresses due to the c
ontraction on crystallization leading to distributed density deficient regi
ons of high free volume. Each of the four commercial PE fibres examined dif
fers from the others in its characteristic outline and the details of its i
nternal substructure. The structure of commercial polypropylene fibres is a
lso compared. (C) 1999 Kluwer Academic Publishers.