Ryoko Nakano

Thermal process-dependence of the mechanical properties and inner structures of pre-consumer recycled polypropylene

Recycled plastics are considered to have less-desirable mechanical properties and durability than virgin materials, and this is usually thought to be due to chemical degradation. However, we recently found that pre-consumer polypropylene (Pre-RPP) was not chemically degraded and had almost the same molecular properties as virgin polypropylene (VPP). In this study, we subjected recycled pre-consumer polypropylene to various thermal treatments and found that we could obtain properties similar to those of virgin polypropylene. We also investigated the fracture surfaces by SEM. The results showed that the mechanical properties were closely related to the inner structure, and if we can control the inner structure of Pre-RPP we may be able to improve its mechanical properties and durability so that they are almost the same as those of VPP.

Modification of polyethylene using side-chain crystalline block copolymer and evaluation of hydrophilicity

AbstractWe synthesized side-chain crystalline block copolymer that exhibit an adsorptive interaction with polyethylene (PE) using a monomer with a long alkane side chain and a hydrophilic monomer. By coating PE with a dilute solution of these block copolymers, the PE surface can easily be endowed with hydrophilicity in a uniform manner. This method does not require a special experimental apparatus or reagents and is more viable than conventional methods in terms of energy efficiency and cost, which means it has a lower environmental impact. Based on the measured contact angle on the modified PE surface, we also evaluated the effects of copolymer concentration in the coating solution and the degree of polymerization in the functional region of the copolymer. The results suggest that the hydrophilicity of the PE surface can be controlled by adjusting these parameters.We synthesized side-chain crystalline block copolymer that exhibit an adsorptive interaction with polyethylene (PE) using a monomer with a long alkane side chain and a hydrophilic monomer. By coating PE with a dilute solution of these block copolymers, the PE surface can easily be endowed with hydrophilicity in a uniform manner. This method does not require a special experimental apparatus or reagents and is more viable than conventional methods in terms of energy efficiency and cost, which means it has a lower environmental impact. Based on the measured contact angle on the modified PE surface, we also evaluated the effects of copolymer concentration in the coating solution and the degree of polymerization in the functional region of the copolymer. The results suggest that the hydrophilicity of the PE surface can be controlled by adjusting these parameters.