| Summary: | 碩士 === 逢甲大學 === 化學工程學系 === 107 === In this study, polyacrylate copolymer (PAc) and polyurethane (PU) were prepared by slightly higher solid content (30 wt%) solution polymerization separately, and then polyacrylate grafted polyurethane (PUA) was synthesized by chemical grafting. The formula contains different proportions of polyacrylate and polyurethane in weight ratio (3/7, 5/5, 7/3).
The properties of PU and PAc can complement each other in some respects in polyacrylate grafted polyurethanes. The presence of the PU segment causes a significant increase in the viscosity of the graft copolymer. It has the best elongation at break when the weight ratio of the two is 1:1.
The molecular weight of each segment and the grafted product were measured by gel permeation chromatography (GPC) to determine that the final product was a polyacrylate grafted polyurethane.
Determined by thermogravimetric analyzer (TGA), it is found that the initial thermal stability is poor when the PU content is high, and there is crosslinking reaction in PU in the later stage, so that the thermal stability of PU is higher than that of PAc at higher temperatures. After grafting, the thermal stability of PUA is mostly between the two, and only PUA37 has better thermal stability at between 300-430 °C.
It is known by differential scanning calorimeter (DSC) that the glass transition temperature (Tg) of the polyurethane soft segment is increased by about 10 ° C after grafting, and the melting point (melt temperature, Tm) of the polyurethane is closer to the glass transition temperature (Tg) of polyacrylates. When the acrylic content is higher, the Tg of the grafted PUA is higher than that of the half blocked PU, and the Tm is lower.
According to an UV-visible analysis, the overall transparency of the PUA is very good and the values are close to 100% mostly.
The dynamic mechanical properties were analyzed by Rheometrics dynamic analyzer (RDA), and the Tg of the PU segment at low temperature was analyzed, but the PU melting behavior significantly interfered with the Tg of the polyacrylate, causing the Tg peak shape to be distorted.
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