The Influence of Curing Temperature on Micro-aggregation Structure and Adhesion Properties of Segmented Polyurethanes

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  • セグメント化ポリウレタンのミクロ凝集構造と接着特性への硬化温度の影響

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Abstract

Segmented polyurethanes (SPUs) were synthesized from 4,4-diphenylmethane diisocyanate (MDI)、1,4-butanediol (BD) and poly(oxytetramethylene)glycol(PTMG) to study the effect of curing temperature on the micro aggregation structure and adhesion properties of the SPUs. PTMG was reacted with MDI, then the prepolymer was chain-extended with BD. It was cured at 50,75,100 and 125 oC to obtain four　kinds　of　the　SPUs, coded　as　SPU-50,SPU-75,SPU-100　and　SPU-125. Their　structure　and　properties　were　characterized　by　swelling, polarized　optical　microscopy　(POM), differential　scanning calorimetry　(DSC),T-peel　testing　and　contact　angle　measurement. When　the　curing　temperature　was increased, the　hard　segment　(HS)　was　aggregated　to　form　the　physical　crosslinkage, resulting　in　relatively　high　melting　temperature　of　HS　(Tm,H)and glass transition temperature (Tg) but low adhesive strength and surface free energy. In addition, the melting point of soft segment (Tm,s) was increased and then disappeared at the high curing temperature. Interestingly, the SPUs cured above 100 oC possessed extremely high Tm,H than that of the SPUs cured at other curing temperatures. The surface free energy of polar component (γsp) and adhesive strength of the SPUs cured above 100 oC had decreased. These results revealed that the polar hard segment component was slightly existed at the top surface of the SPUs.Thus,the adhesive strength was strongly dependent on existed hard segment at the top of SPUs surface.Furthermore,cohesive failure was observed in all SPUs. The result was contributed that the interaction between SPUs adhesive and aluminum substrate with high polar ity was stronger than the intra molecular interaction of SPUs adhesive.

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