Preparation And Properties Of Aromatic Hyperbranched Polyesters And Its Blends With PTT

Hyperbranched polymers(HBP)have three-dimensional spherical or near spherical structures and a large number of functional groups on their surfaces,which are easily form great interactions with other materials.Poly trimethylene terephthalate(PTT)is a linear thermoplastic aromatic polyester.In this paper,the HBP having similar chemical structure with linear PTT was prepared and blended with PTT to prepare PTT/HBP blends.The interactions between PTT and HBP were studied.PTT has a large number of proton receptors(carbonyl—C=O)and HBP has a large number of proton donors(e.p.the hydrogen atoms on the COCH₃)at the end of HBP.By changing of the composition and flexibility of HBP,different HBP were used to be blended with PTT.The affect of the HBP's content and flexibility on the properties of blends were studied.First,a series of hydroxyl-terminated aromatic HBP made of monomers of TMT as B₃and Diols(EDO,PDO,BDO,HDO,etc)as A₂ were prepared by the"stepwise decreased-temperature polycondensation"method.The results suggest that HBP can be prepared with moderate molecular weight at a higher reaction rate.This method can improve not only the reacton extent of B functional group but also the conversion of the monomer.Terminal hydroxy of HBP was modified by acetic anhydride and HBP's thermal stability was greatly improved.Second,HBP/PTT blends were characterized for the hydrogen bonds,melt point,crystallinity,dynamic mechanics performance,dnamic rheological properties and solution crystallization morphology.The results showed that(1)the number of hydrogen bonds increase with the increasing addition of HBP;(2)when terminal chains are the same,it decreases with the increasing of HBP skeleton flexibility;(3)when the A2 unit is the same,with the growth of the length of A2 chain,terminal chain conformation increases.As a result,the content of hydrogen bonds decrease firstly and then increase.For the compatible blends,the potential energy contribution of hydrogen bonding to the PTT segments was calculated.The results showed that the interaction of HBP-EDO-AN/PTT was stronger than that of HBP-PDO-AN/PTT.The contribution of hydrogen bonding to the chemical potential of PTT segments from the former is larger than that fromed in the latter.The complex viscosity of the series of HBP-PDO-AN/PTT is higher than that of pure PTT,while the complex viscosity of the series of HBP-PEO-AN/PTT relies is lower.The complex viscosity of HBP with different flexibility is relatively complicated,mainly controlled by the length of terminal diol chain.