Shigehiko Abe

LLDPE/LDPE blends. I. Rheological, thermal, and mechanical properties

Structure and mechanical properties were studied for the binary blends of a linear low density polyethylene (LLDPE) (ethylene-1-hexene copolymer; density = 900 kg m−3) with narrow short chain branching distribution and a low density polyethylene (LDPE) which is characterized by the long chain branches. It was found by the rheological measurements that the LLDPE and the LDPE are miscible in the molten state. The steady-state rheological properties of the blends can be predicted using oscillatory shear moduli. Furthermore, the crystallization temperature of LDPE is higher than that of the LLDPE and is found to act as a nucleating agent for the crystallization of the LLDPE. Consequently, the melting temperature, degree of crystallinity, and hardness of the blend increase rapidly with increases in the LDPE content in the blend, even though the amount of the LDPE in the blend is small.

Study on the foaming of crosslinked polyethylene

The processing of crosslinked polyethylene foam, which has a closed-cell structure, has been investigated. In this study, two types of linear low-density polyethylene (LL) produced by a metallocene catalyst were crosslinked by dicumyl peroxide (DCP). The expansion ratio of the foams decreases with increasing the DCP content, which is due to the enhancement of the elastic modulus. Moreover, the crystallization temperature Tc of the foams is also responsible for the expansion ratio. After expansion, the crosslinked foam with lower Tc shrinks to a great degree prior to the crystallization, which is attributed to the volume reduction of the gas in the cells. As a result, the expansion ratio decreases. The degree of shrinkage decreases with increasing the Tc, because immediate crystallization prevents the shrinkage.

LLDPE/LDPE blends. II. Viscoelastic properties in solid state

The effect of a small addition of a low density polyethylene into a linear low density polyethylene (ethylene-1-hexene copolymer; density = 900 kg m−3) on the linear and nonlinear viscoelastic properties in the solid state were studied. It was found that the addition of the low density polyethylene leads to a well-organized crystalline structure. Consequently, the location of α relaxation process is shifted to higher temperature or longer time. Furthermore, the mechanical nonlinearity of the blend is found to be more prominent than that of the pure linear low density polyethylene.