Studies Of Graft Polymerization Of Maleic Anhydride And Isoprene Onto Polyhydroxyalkanoates By ～(60)C_Oγ Of Radiation

This paper focuses on an effective way to improve the thermostability ofpoly-β-hydroxybutyrate (PHB) and its copolymer poly-3-hydroxybutyrate-co-3-po-lyhydroxyvalerate (PHBV). Maleic anhydride (MA) is grafted onto PHB and PHBVby ⁶⁰Co γ of radiation. Further studies are ongoing by using ⁶⁰Co γ of radiation inducegraft polymerization of isoprene onto PHB.The spectra of both ¹HNMR and ¹³CNMR were investigated following theradiation-induced polymerization. The results are consistent with successful graftingof the MA monomer onto the PHB. The results observed through TGA demonstratethat thermostability has been measurably improved with the introduction of MAgroups. The decomposition temperature of PHB-g-MA(Xg=0.52%) is 36 ℃ higherthan ordinary PHB, while the PHBV-g-MA(Xg=0.85%) is 70 ℃ higher than PHBV.Moreover, the DSC results show that both the melting temperature and thecrystallization temperature have been decreased. From the XRD experiment it isapparent that the crystalline degree of the grafted PHB has been decreased and itshydrophilic property has been notably improved.Different radiation conditions have greatly influenced the behaviors of thegrafted samples. With the increase of MA monomer concentration, graft degree,molecular weight and decomposition temperature have been increased slightly. Theincreasing radiation dose leads to significant decrease of the molecular weight. Theintroduction of MA group has apparently hindered the degree of the radiationdegradation. With the increase of radiation dose rate, both graft degree and molecularweight have been improved. Further studies are ongoing by adding Cu(NO₃)₂ to the radiation reaction systemof the induced polymerization of isoprene grafted onto PHB. The results show boththermostability and mechanical property have dramatically improved. Thermostabilityof grafted samples produced from the reaction system without Cu(NO₃)₂ has notapparently improved. On the contrary, it has improved significantly after addingCu(NO₃)₂ to the radiation reaction system, with the decrease of graft degree. Afteradding Cu(NO₃)₂ to reaction system, mechanical properties of both PHB-g-PIP100Cuand PHB-g-PIP19Cu have greatly improved. Tensile strength and toughness haveimproved slightly, while the Flexural strength and modulus have increased.