Preparation And Degradation Properties Of PLA/PBAT Films

Extension of the biodegradable materials is regard as the most fundamental and most effective way to solve the white pollution, but their degradation periods can't be controlled is a hinder in this progress. Studying the degradation mechanism of the biodegradable materials in depth can provide some theoretical support for controlling its degradation period scientifically, is meaningful to promote the development of biodegradable materials.Two biodegradable materials-polylactic acid(PLA) and poly(butyleneadipate-coterephthalate)(PBAT) were choosen as the major materials. They were melt blended with ethylene n-butyl acrylate-glycidyl methacrylate terpolymer(EBA-GMA), ethylene methyl acrylate-glycidyl methacrylate terpolymer(EMA-GMA) and benzoyl peroxide(BPO) separately, and the rheological properties, the molecular weight and the polydispersity index, the dynamic thermo mechanical properties, the microstructures and the mechanical properties of the PLA/PBAT blends with different compatilizers were studied by Happ torque rheometer, gel permeation chromatograph(GPC), dynamic thermal mechanical analyzer(DMA), scanning electron microscope(SEM) and tensile testing machine at first. The results manifested that the dynamic thermal mechanical properties, the molecular weight and the mechanical properties of the PLA/PBAT blends enhanced with the addition of EBA-GMA, EMA-GMA and BPO. Among the three compatilizers chosen in this paper, BPO was the best one for PLA/PBAT blends. After studying some properties of the PLA/PBAT/BPO blends with different content of PLA, PLA/PBAT/ BPO=55/45/1, PLA/PBAT/BPO =45/55/1 and PLA/PBAT/BPO=35/65/1 were choosen as three formulas for the following blow molding.Secondly, the hydrolysis properties of the PLA/PBAT/BPO films were researched through the lye accelerated degradation experiment. By analysing the weight loss of the films as well as the p H of the degradation solutions, it could be see that the degradation rates of the PLA/PBAT films were accelerated with increasing the content of PLA. The films which contain 55 phr of PLA had the fast degradation rate, after they had been immersed in the 0.01 mol/L Na OH solution for 28 days, their weight can reached 40.87%. The detection results of the Fourier transform infared spectromotry(FT-IR), DMA, Differential scanning calorimetry(DSC), Polarized Optical Microscopy(POM), GPC and Ultraviolet-visible spectrophotometer manifested that: the essence of the PLA/PBAT films' hydrolysis was the breaken of the ester bond, hydrolysis could make the storage modulus, Tg and the Mw of the films diminished, meanwhile increased their degree of crystallinity, crystal ability and transparency.Thirdly, the photooxidation behavior of the PLA/PBAT/BPO films has also been studied through a UV accelerated ageing test in this paper. The results of GPC and Ultraviolet-visible spectrophotometer indicated that with decreasing the content of PLA in the PLA/PBAT blends their ability of UV-absorption and the photooxidation rates raised. The films which contained 35 phr PLA had the fastest photooxidation rate, after being irradiated for 192 hours their Mw declined to 17% that of the films before irradiation. Photooxidation could weaken some properties of the PLA/PBAT films, like the Mw, the storage modulus, the content of CH-, the mechanical properties and the transparency, while increased their degree of crystallinity, crystal ability, content of C=O and-OH, Tg as well as content of gel. However, the photooxidation had not obvious influnce on the weight loss of PLA/PBAT films. Based on the observation of the PLA/PBAT films' Mw, weight loss and transparency before and after irradiation, we found that the PLA/PBAT films became more yellow with the content of chromophore increased, and the photooxidation rate got faster at the same time. Because of the exist of benzene, the molecular chain can disrupt through Norrish reaction in PBAT, so the photooxidation mechanism of PLA/PBAT film is very complex.