Study On Aging Behavor Of PBAT/PLA Degradable Mulch

Polymer-type degradable mulch has become an alternative to traditional mulch due to its excellent degradability,excellent mechanical properties and processing performance.In order to accelerate the popularization of degradable mulch in actual agricultural production,and solve the problems of aging and early cracking in applications,it is urgent to study the aging behavor of polymer degradable materials.In this study,field experiment and indoor accelerated aging experiment are used to study the changes in molecular structure and properties under the influence of ultraviolet light,temperature and humidity.A method for predicting the service life of degradable mulch in field through laboratory accelerated aging experiment is established.1.THD:Place 10 sample films in the constant temperature and humidity chamber,set the condition to 60?for 8 hours under no UV-light condition,and then to maintain constant temperature at 50?and humidity at 90%in a dark environment for 4 hours,take one piece of sample at 9 o'clock every day;UVD:Place 20 sample films in an ultraviolet aging box,set the condition to be under ultraviolet light at 60?for 8 hours,and then condensation in a dark environment at 50?for 4 hours,take two pieces of sample at 9 o'clock every day;CED:PBAT/PLA mulch was laid on the experimental garlic field which was provided sufficient water and fertilizer for garlic growth.The samples were taken on the 18th of each month.The samples obtained in the three experiments were washed and dried for structural and performance tests.2.THD showed that:soxhlet extraction cross-linking degree test showd that the cross-linking degree is 0;in the thermogravimetric test?TG?,T_10%is only reduced from358.1?to 352.6?at 10 days;in the DSC test,the change range of T_m-PBAT is from 114.2?to 112.1?;in the mechanical property tensile test,the change trend of the two index parameters of elongation at break?EB?and tensile strength?TS?is 800%-750%and 35MPa-32 MPa;the optical transmittance data in optical performance only decreased by 0.5%.THD experiment showed that temperature and humidity did not cause PBAT crosslinking and chain scission,and did not significantly affect the aging performance of PBAT/PLA film in a short period of time.UVD showed that:the crosslinking degree data continued to increase from 0%to 46%;in the thermogravimetric test?TG?,T_10%continued to decrease from358.1?to 322.1?at 10 days;in the DSC test,the variation range of T_m-PBAT is114.2?-97.5?;in the GPC test,the continuous increase range of the dispersion index PDI is2.06-2.84.UVD experiment showed that under UV-light environment,PBAT/PLA film aging is cross-linked at the initial stage,and then chain scission and crystal phase reorganization occur.Due to further cross-linking and chain scission,the crystal structure was eventually destroyed,resulting in embrittlement of the degradable film.3.The data comparison of CED and UVD showd that:in the GPC test,the PDI of the PBAT/PLA film in UVD for 10 days was very close to the PDI in CED for 4 months?2.84-2.82?;In SEM,microscopic photos observed many relatively large corrosion holes in the cross-section of the sample in 10 days of UVD and 4 months of CED;the tensile test of mechanical properties found there is a very obvious correspondence in elongation at break and tensile strength between 10 days in the UVD experiment and 4 months in the CED experiment?128%-131%;7.63 MPa-8.16 MPa?;in the optical performance,in10 days of UVD and 4 months of CED,transmittance and haze parameters reach approximately the same degree?85.3%,48.5%?;in the polarized light microscope?POM?,the photo of the crystal morphology change also reflects this correspondence.The experimental results showed that the change of the structure,morphology and main performance of PBAT/PLA degradable mulch film in the indoor ultraviolet accelerated aging experiment for 10 days can reflected the true aging situation of the outdoor field cultivation environment for 4 months.Therefore,a method for predicting the service life of PBAT/PLA mulch in field through accelerated experiment in the laboratory was established.