Study On ACR Toughening PLA And Its Stability In Hydrolysis Degradation

In recent years,the poly?lactic acid??PLA?have extensively been studied and become a popular topic in material sciences,due to the advantages of biodegradability,excellent mechanical properties,strong processability and environmental protection.It has become good material to replace petroleum based plastics.However,the bad ability of toughness and the hydrolysis of PLA were present some problems in applications.In particular,the hydrolytic degradation during storage,transportation and use were result in the decrease of the mechanical properties of PLA products.Therefore,it is necessary to toughen and hydrolyze the PLA.Hence,the improvement of toughness and hydrolysis resistsnce performance of PLA has an important.In this paper,PLA is toughened with acrylate toughening agent?ACR?.On this basis,the PLA is subjected to hydrolysis modification by synergistic addition of a chain extender.The effects of polycarbodiimide?PCDI?and 1,4-butanediol diglycidyl ether?BDE?as chain extenders on the properties of PLA/ACR blends were investigated.The experimental research results are as follows:1.The addition of chain extender improves the toughness of the material,and reduces the MFR value and carboxyl terminal content.The optimal addition amount of PCDI and BDE chain extender was 1.8 wt%and 1.0 wt%,respectively.The results showed that the impact strength was increased to 133.87 J/m,the elongation at break improved to 67.52%,the MFR value reached to 6.8 g/10min,and the content of terminal carboxyl group decreased to 10.31 mol/t of the PCDI 1.8.The impact strength was reached 219.8 J/m at the content of 1.0 wt%BDE,the MFR value reached to 8.0 g/10min,and the carboxyl terminal residue reached to 33.01 mol/t and elongation at break was increased to 63.57%,respectively.2.The results of hydrolytic degradation test showed that the A10,PCDI 1.8 and BDE1.0 samples for complete degradation time was 896 days,1533 days and 1228 days,respectively.The decreasing rate of tensile strength was 34.55%,19.69%and 28.01%after 60 days of hydrolysis,respectively.Compared with the A10 sample,the PCDI 1.8 and BDE 1.0 samples took longer to completely degrade,the tensile strength decreased,and the hydrolysis resistance improved.3.The study on the thermal properties of the samples after hydrolysis found that the T_cc of PCDI 1.8 samples changed little with the time of hydrolysis degradation.It was shown that less affected by hydrolysis erosion;The T_g of BDE 1.0 decreased to 52.62°C.The hydrolysis environment increased the crystallinity of the samples,and the T_g,T_cc and X_c values of the samples first increased and then decreased with the extension of the hydrolysis time.4.Trace the residual content of carboxyl terminus of the sample after hydrolysis.The content of terminal carboxyl group in A10,PCDI 1.8 and BDE 1.0 samples were increased to 27.45 mol/t,15.14 mol/t and 13.44 mol/t in 60 days after hydrolysis,respectively.PCDI1.8 and BDE 1.0 samples showed a smaller ration in the end group residual content and consistently lower than that of A10.The results showed that chain-extender inhibited hydrolysis degradation.