A study of mechanical properties and molecular motions at low temperature of novel polyolefin materials

In this study, mechanical properties and molecular motion at low temperature of novel polyolefin materials with cyclohexane moiety in the chemical structure synthesized by Takeuchi et al., Poly-alilcyclohexane (PACH-3), Poly-pentenylcyclohexane (PPCH-5), Poly-heptenylcyclohexane (PHCH-7) and Poly-undecenylcyclohexane (PUCH-11), were investigated 1),2) . From DSC results, the melting temperature of the samples decreased with an increase of the alkyl-chain length though, the enthalpy of heat of fusion of them increased with the alkyl-chain length. From DMA result, the α relaxation peak can be observed clearly and the temperature decreased with the alkyl-chain length. The β relaxation peak can also be observed at around -50 o C, and the peak intensity decreased with the alkyl-chain length. Moreover, the γ relaxation can be observed clearly around -100 o C, and the strength of the δ relaxation of PPCH-5 was the largest among these samples. From three-point-bending test result from -150 o C to RT, PACH-3 with the shortest alkyl-chain length had the highest modulus at - 150 o C, but its modulus decreased most gradually with temperature and its modulus became the highest at room temperature. On the other hand, from Anharmonic estimation result, Grüneisen constant of PACH-5 in -150~-100 o C was the smallest in these samples. This result was consistent with the strength of the γ relaxation, indicating that an association between its anharmonicity and the molecular relaxation exits and PPCH-5 can be expected to have better mechanical properties at low temperatures because it has suitable cooperation size for a molecular motion which consists of cycro-ring and a certain alkyl-chain length. © 2019 The Society of Materials Science, Japan.