Aggregation Structure and Mechanical Properties of Polyurethane Elastomers with Poly(oxytetramethylene)Glycol with Side Methyl Groups

摘要

In this study,the poly(oxytetramethylene)glycol(PTMG)with methyl and dimethyl side groups was introduced as a polymer glycol for the preparation of polyurethane elastomers(PUEs).The PTMG with methyl side groups(PTG-L)was synthesized by random polymerization of tetrahydrofuran(THF)and 3-methyl THF.The another PTMG with dimethyl side groups(PTG-X)was prepared by a reaction of oligo-PTMG with neopenthyl glycoli.The effect of methyl groups on aggregation structure and mechanical properties was investigated using differential scanning calorimetry(DSC),measurement of dynamic viscoelastic properties,tensile test and wide angle X-ray diffraction(WAXD).PTMG,PTG-X and PTG-L with molecular weight of 2000 were employed for the preparation of the PUEs.The PUEs were prepared with polymer glycols,4,4'-diphenylmethane diisocyanate(MDI)and 1,4-butanediol(BD)by a prepolymer method.DSC measurement showed that DELTAT_g(=T_g of original polymer glycol-T_g of soft segment in the PUEs)and melting point of hard segment domain increased and decreased with an increasing methyl group content,respectively.These results suggest that micro-phase separation of the PUEs was getting weaker with an increase in methyl group content.Young's modulus and tensile strength of the PTG-X and PTG-L based PUEs decreased with an increasing methyl group concentration.In contrast,strain at break exhibited opposite trend.These results clearly indicate that the increasing methyl group concentration made the PUEs be flexible and soften.WAXD measurement during elongation process revealed that the PTMG based PUEs,PTG-L and PTG-X based PUEs with ca.10 mol% of methyl side groups showed the elongation-induced crystallization but the PTG-L and PTG-X based PUEs with ca.20 mol% of methyl side groups didn't.It was revealed from these results that the introduction of methyl groups to PTMG is quite valuable for the preparation of the PUEs with various mechanical properties.