T. Li et al., BLOCK-COPOLYMERS AS COMPATIBILIZERS FOR BLENDS OF LINEAR LOW-DENSITY POLYETHYLENE AND POLYSTYRENE, Journal of polymer science. Part B, Polymer physics, 33(4), 1995, pp. 667-683
Compatibilization of blends of linear low-density polyethylene (LLDPE)
and polystyrene (PS) with block copolymers of styrene (S) and butadie
ne (B) or hydrogenated butadiene (EB) has been studied. The morphology
of the LLDPE/PS (50/50) composition typically with 5% copolymer was c
haracterized primarily by scanning electron microscopy (SEM). The SEB
and SEBS copolymers were effective in reducing the PS domain size, whi
le the SB and SBS copolymers were less effective. The noncrystalline c
opolymers lowered the tensile modulus of the blend by as much as 50%.
Modulus calculations based on a core-shell. model, with the rubbery co
polymer coating the PS particle, predicted that 50% of the rubbery SEB
S copolymer was located at the interface compared to only 5-15% of the
SB and SBS copolymers. The modulus of blends compatibilized with crys
talline, nonrubbery SEB and SEBS copolymers approached Hashin's upper
modulus bound. An interconnected interface model was proposed in which
the blocks selectively penetrated the LLDPE and PS phases to provide
good adhesion and improved stress and strain transfer between the phas
es. (C) 1995 John Wiley & Sons, Inc.