Study Of Preparation And Property Of Irradiation Modified Poly (Lactic Acid)

Poly (lactic acid) (PLA) is a kind of novel biodegradable thermoplastic resin. This work introduce electrical beam to linear PLA, including both Poly(L-lactic acid) (PLLA) and Poly(D, L-lactic acid), (PDLLA), causing chain grafting and chain scission at the same time, and thus leading to long branching structure with preferable property of melt elasticity or cross-linked resin with higher heat stability. Relation between the structure and properties of modified material was studied. As well as a series of optimized radiation processing technique parameter have been given out. Major achievements have been listed as follows:1. Balance between chain grafting and chain scission of PLA under various radiation dosage was studied. It turned out that chain scission is in the predominance when pure PLA was exposed under electron beam. Cross-linked PLA with more than 80% of gel fraction was prepared with a little gradient of Polyfunctional Monomer (PFM). The use of different sorts of PFM, different content, and different dose affect the cross linking efficiency drastically. Glass transition was tested. It turned out T_g has increased over 10℃caused by the network structure. 2. Long chain branched PLA was prepared with a little gradient of Bifunctional Monomer (BFM). The use of different sorts of BFM, different content, and different dose affect the branching reaction efficiency drastically. Dynamic shear rheological tests results show that PLA with long-branch structure has preferable property of melt elasticity, which is indicated by a higher G' (elastic shear modulus) value and lower tan 8 (loss angle tangent value). Melt strength increased with increasing Bifunctional Monomer (BFM) content, or radiation dose. It means this modification is totally controllable.