Study On The Hydrolysis Resistance Method Of Pla Fiber (materials) Abstract

The exploration and application of degradable polymer have become one of the most effective solutions for petroleum-based plastic waste problem. Current, poly(lactic acid)(PLA)have many merits such as excellent biodegradability, processability, simple manufacture flow and have become the main product studied among degradable polymers. This paper is to study how to solve easily degradable problem of polylactic acid. Polylactic acid products in will be easily degraded, which greatly limits the application of polylactic acid materials. In this thesis, internal and external structural adjustments aiming to slow degradation of the polylactic acid were approached.As to polylactic acid in the internal structure adjustment, we have studied the film in a suitable solvent preparation with the addition of neutral buffer salt to slow the degradation of polylactic acid. During degradation, the carboxyl or lactic acid resulted from the degradation of polylactic acid act as the catalyst. Through the buffer salts added, polylactic acid material can be controled in neutrol pH region in some extent. This paper added 3%-5% buffer salt of pH of 7.0 which is the mixture of Na2HPO4 and KH2PO4.We finded that in 95℃water bath and 50℃environment degradation experiment, the neutral buffer salts added polylactic acid material could maintain a significant higher strength. By SEM, WXRD and viscosity-average molecular weight analysis of buffer additions, the data showed that the addition of neutral buffer salt really slowed the degradation of poly-lactic acid. The results suggested that addition of the buffer salt did not change the crystallinity of polylactic acid..As to the polylactic acid in the external structure adjustment, we had studied the effect of water and oil repellent finishing of polylactic acid on the degradation performance. During the experiment, we explored a method which evaluate the water and oil repellent grade of finished materials, and water droplet contact angle with water was also as a method to evaluate the water and oil repellent performance. The optimized finishing conditions was curing at 150℃for 3min. Via the evaluating of fiber tensile strength, elongation at break, viscosity-average molecular weight and SEM of the fiber with and without water and oil repellent finish, it is no doubt that water and oil repellent finish can greatly delay the degradation of PLA fibers.The data in this thesis suggest that either through the internal buffer of polylactic acid or polylactic acid fiber to water and oil repellent finishing, could have significant effect on the delay of water hydrolysis degradation of polylactic acid based material.