Study On Synthesis And Phase-change Characteristic Of PTT And PTT-PEG Block Copolymer

Poly(trimethylene terephthalate) is a new kind of polyester, which will be widely used in textile,engineering plastics,films etc. for its special structure and outstanding physical and chemical properties. Because of the exist of three phenylenes which lying in macromolecular chain will generate"The Effect of odd carbon", and lead to different performances from PET and PBT. Thus the PTT fiber can not only have the rigidity of PET and the flexible of PBT synchronously, but also doubles the virtues of PET and PA such as high resilience, easier process and dye etc. Polyethylene glycol(PEG) itself is a kind of phase change material with high enthalpy and low thermal hysteresis. It is often used to synthesis novel phase change materials as working groups. In this paper, poly trimethylene terephthalate(PTT) with various molecular weights,poly trimehtylene terephthalate-poly ethylene glycol(PTT-PEG) block copolymers were prepared by the direct esterification and polycondensation.FTIR, DSC, TG, 1HNMR were used to study the structural characteristics,phase-change behavior, heat storage characteristics and phase change mechanism of the novel solid-solid phase change heat storage copolymer which features PEG-based soft segment and PTT-based hard segments.The influent factors on synthesis process of PTT were discussed. The optimized process conditions of a direct esterification way were: charge ratio of 1:1.6, catalyst amount: 3.68×10-4mol/mol PTA, polycondensation temperature: 265℃. PTT-PEG block copolymers with varied PEG molecular and different contents were synthesized by copolymerization. The phase-change properties in the normal temperature were scanned by DSC. The result showed that the copolymers have gained increasing phase-change properties after the molecular weight of PEG which was used in the copolymerization exceeded one particular numerical value. The phase-change enthalpy of copolymers had an increasing aftermath with the increasing of PEG contents, but it was proved that the volume heat would decrease when the initial charge ratio of PEG/PTA exceeded 40%. By FTIR and 1HNMR, it was proved that the macromolecular chain was polyblock sealed by hard segment. The content of PEG segments depended on the ratio of PEG/PTA which was added to the system from the beginning. We can control the phase-change characteristic of PTT-PEG block copolymers by changing the molecular of PEG and the ratio of PEG/PTA. When its phase-change characteristic is asked to perform under normal temperatures, we can set the charge ratio of PEG/PTA as 40%, including 60%PEG6000 and 40%PEG4000.The results showed that the PTT-PEG copolymers have good thermal properties: appropriate transition temperature, good thermal stability, and no liquid leakage in the phase-change process. The heat storage mechanism is indeed the transition process of the soft segment of PEG from crystalline state to amorphous.