Low temperature endotherm in multiblock terpoly(ester-b-ether-b-amide) thermoplastic elastomers

The phenomenon of the occurrence of a middle-temperature thermal effect in crystallizable multiblock thermoplastic elastomers, the so-called annealing endotherm has not yet been univocally explained, hence, it was subjected t o DSC analysis. The formation of this endotherm in response to the time and temperature of conditioning (stabilization) of the sample has bene followe d. The investigation have been per formed for a specific polymer system, po ly(tetramethylene terephthalate)- block-poly(oxytetramethylene)-block-polyl aurolactam (PBT-b-TPMO-b-PA12)-(n). The specific property of this elastomer is the solubility or a partial solubility of one of the components (PBT bl ock) in the two remaining ones being mutually insoluble. The occurrence of the tow different amorphous phases (PBT and PA12) in this elastomer wit gla ss transition temperatures T-g >20 degreesC is also possible. This specific system permits to observe an interesting phenomenon, since at the points d etermining the middle-temperatures of the glass transition temperatures of the elastomer, the two small endotherms are shaping; after proper stabilisa tion they are approaching each other, and as a result of this process they would form one extreme. This extreme comprises the thermal effect of the di spersion of the mesomorphic aggregates being the intermediate form between the amorphous state and the crystalline state. The mesomorphic aggregates c onstitute the additional network points of the physical polymer network of the elastomer.