Influence of Polyethylene-g-polystyrene on the Mechanical Properties and Foaming Behavior of Linear Low Density Polyethylene/Polystyrene Blends

Polyethylene-g-polystyrene(PE-g-PS) copolymers, which were synthesized by the combination of ring-opening metathesis polymerization(ROMP), hydrogenation and atom transfer radical polymerization(ATRP) method, were utilized to compatibilize linear low density polyethylene/polystyrene(LLDPE/PS) blends. Using the LLDPE/PS blend in mass ratio of 70:30 as example, the effect of introduction of PE-g-PS on the mechanical properties was investigated. Compared to binary blends, elongation at break, tensile strength and yield strength are improved when the PE-g-PS is introduced. Utilizing PE-g-PS0.34k(the subscript 0.34k represents a relative molecular mass of PS is 340) and PE-g-PS1.59k as compatibilizers, the influence of PS branch length on foaming behavior of LLDPE/PS blends was investigated in a batch foaming process with supercritical carbon dioxide as physical foaming agent. Compared to the case containing PE-g-PS0.34k, the cellular structure of the foamed blends becomes much more uniform and no large gap appeares with the addition of PE-g-PS1.59k. When the foaming temperature is lowered to 80 ℃, confined effect of LLDPE solid around exists, much more uniform cellular structure also appears as PE-g-PS1.59k is introduced.