Study On The Synthesis And Properthties Of Block And Graft Polyurethanes Containing Polys Ytrene As Hard Segement

As we all know,common polystyrene is rigid with higher Tg and cheap.In this paper,a series of block and graft polyurethane(PU)s were prepared from dihydroxy-terminal polystyrene(HO-PS-OH)and styrene-2-hydroxyethyl methylacrylate copolymer(PS-co-HEMA).These block and graft PUs showed good mechanical properties.The major contents and important achievements in this paper are described as follows:1?HO-PS-OH was successfully prepared from a sample radical polymerization of styrene with 4,4'-azobis(4-cyano-1-pentanol)(ACP)as initiator,which was used as as hard segments of synthetic block polymers.With considering the possible disproportionation on termination in polymerization,it is reasonable to use solution polymerization,because bulk polymerization leads to high viscosity.Toluene is good solvent of polystyrene with low transfer reaction.End groups of HO-PS-OH analyzed by NMR and the functionality of HO-PS-OH was calculated as 1.80.GPC curves of HO-PS-OHs were all single peak.Mn was 10760g/mol,Mw was 19045 g/mol,PDI was 1.77 and Tg was 89.2 ?.HO-PS-OH showed good reactivity because of an increase of Mn from 11060g/mol to 33267g/mol after reaction with 4,4'-methylenediphenyldiisocyanate(MDI).2?In this study,a series of novel PS-b-PU segmented PUs were prepared from polycondensation of HO-PS-OH,poly(1,4-butylene adipate)(PBA)and MDI.FT-IR and 1HNMR characterization confirmed the chemical structure.GPC data exhibited that an Mn was between 27925g/mol and 43225g/mol,an Mw between 57690 g/mol and 100541 g/mol.Differential scanning calorimetry(DSC)indicated that the Tg of soft phase is between-43.29? and-45.80?,Tg of hard phase is between 92.56?and 98.08?.Thermogravimetric analysis(TGA)indicated that initial decomposition temperature at over 235.0?.DMA test showed there were two peaks in storage modulus-temperature curves and mechanical loss factor-temperature curves.SEM showed the morphology of fracture characteristics were changed from fragile to ductile as PS content increases.Tensile testing indicated ultimate tensile strength up to 34.57MPa and ultimate elongation at break up to 835.94%.3.PS-b-PUs are thermoplastic polymers,however,several styrene-2-hydroxyethyl methylacrylate copolymers(PS-co-HEMAs)were first synthesized in bulk copolymer and a series of crosslinking PS-co-HEMA/PU foams were prepared by the addition of HO-PBA-OH and MDI.Characterization of PS-co-HEMAs were made with FT-IR and 1HNMR spectroscopy,which confirmed the chemical structure.GPC data exhibited that an Mn was 21619g/mol,an Mw was 44231g/mol,PDI was 2.05.DSC data showed that Tg was 95.64?.Characterization of PS-co-HEMA/PUs were also made.There is no signal of Tg and crystallization in DSC test.However,evidence of good compatibility in PS/PU phase was found in DMA characterization.It says broad peak of mechanical loss.The Tg of soft segment increases from-20?to 15 ? which indicated good compatibility.TGA analysis showed that initial thermal degradation temperature was between 274 ? and 283 ?,which indicated good thermal stability of crosslinking PS-co-HEMA/PUs.SEM showed there was a tendency of microphase separation in PS-co-HEMA/PUs.Tensile test showed that(PS-co-HEMA)35/PU had the best comprehensive mechanical properties,with a tensile strength of 15.00MPa and a breaking elongation of 98.57%.