The Research Of Accelerated Biodegradation Behavior Of PLA Nonwovens Under Simulated Natural Environment Condition

As nonwovens are widely used in China, the waste will become a problem we have to face, the traditional waste disposition caused serious pollution. Developing and producing biodegradable nonwovens used in some related areas is an effective way to solve the waste pollution. Polylactic acid(PLA) which has good compatibility and biodegradability is an ideal nonwoven materials, it can be used to replace some polyolefin and polyester materials. Degradation of PLA is well recognized, but its degradation in the natural environment is affected by different microbial colonies, and it takes a long period to evaluate the degradation, so it is difficult to get the evaluation results quickly. In addition, consider the mechanism and cost of PLA, it tends to blend with other degradable or non-degradable polymer, and there are less research thesises on these materials.In this paper, we put PLA, PLA/PHB and PLA/PET nonwovens into the natural soil condition and accelerated biodegradation system, and studied their physical and chemical properties before and after biodegradation. And also, we studied their degradation behaviors and mechanism.1. After the rapid evaluation of PLA, PLA/PHB and PLA/PET nonwovens biodegradability using soil extractable solution, we found the results were consistent with the biodegradation in natural environment, so the soil extractable solution can be used to evaluate PLA and its blends biodegradability.2. In the research of PLA and its blends biodegradability using soil extractable solution, we found the accelerated biodegradation of PLA nonwovens had two stages, the first stage occured within 3 days, the properties decreased apparently. In the second stage, the properties had no obivious change. The degradation mechanism of PLA nonwovens was that microorganisms attacked the PLA molecular chain ends, decomposited in the form of component units, it was the overall degradation process rather than gradual erosion from the outside to the inside.3. In the research of PLA and its blends biodegradability using soil extractable solution, we found the degradation mechanism of PLA / PHB nonwoven was that the PLA component kept its degradation mechanism, and PHB component followed the degradation mechanism of enzymatic hydrolysis, which meaned the ester bond of main chain was cut off. It was heterogeneous degradation, followed the gradual erosion from the surface to the interior. PHB could accelerate PLA degradation under certain condition. The degradation mechanism of PLA / PET nonwovens was that the PLA componetnt kept its degradation mechanism, while the PET component can not be degraded.4. The II generation bacterial suspension showed the better degradability than the I and III generation. We selected the II generation bacteria with concentration of 0.5%(v / v), the drum volume of 80 ml / min, the solid-liquid ratio of 1:40 at the conditions, and found that 80 days later, The degradation rate of PLA nonwovens reached 48.37%. The degradation cycle of PLA in the natural environment is very long, however, the degradation efficiency can be significantly improved through culturing targeted microbial colonies. Combined with other biodegradation indicators, a convenient and relatively objective method can be established for materials’ biodegradability evaluation.5. Aliphatic polyester can be degraded by a considerable number of microorganisms under the local soil in Guangzhou. PLA, PLA / PHB nonwovens can be degraded under the soil conditions of Guangzhou University Town, however, PET can not be degraded under the same soil condition.