P. Ghosh et al., REACTIVE MELT PROCESSING OF POLYETHYLENE - EFFECT OF PEROXIDE ACTION ON POLYMER STRUCTURE, MELT RHEOLOGY AND RELAXATION BEHAVIOR, Polymer, 38(25), 1997, pp. 6175-6180
Reactive melt processing of polyethylene (PE) was accomplished at 170
degrees C under the influence of two different doses (0.75 and 1.25 mm
ol per 100 g PE) of dicumyl peroxide (DCP). The effect of peroxide act
ion on melt rheology of PE at 160, 180 and 190 degrees C was studied b
y a constant shear rate plate and cone viscometer. Peroxide action led
to establishment of a mild degree of crosslinkages in PE and hence to
enhancement of its melt viscosity, the effect being higher for use of
a higher DCP dose. The melts of PE and modified PE showed pseudoplast
ic flow behaviour. The pseudoplastic character, however was less prono
unced at higher rates of shear and at a relatively low temperature. Us
e of a low dose of DCP (0.75 mmol per 100 g PE) modified the polymer m
arginally, causing little or only marginal changes in relaxation time
and shear modulus, while a higher DCP dose (1.25 mmol per 100 g PE) in
corporated significant changes in the polymer structure due to establi
shment of more than a critical degree of peroxide induced crosslinkage
s, thereby causing a substantial enhancement in the shear modulus and
a drop in relaxation time. Odd effects of temperature on viscoelastic
character are also interpreted on the basis of total dissolution of re
sidual crystalline orientations in PE melts at greater than or equal t
o 170 degrees C. (C) 1997 Elsevier Science Ltd.