Study On The Structure And Performance Of MMT Modified Fishery Degradable Materials

Fishing nets made of non-degradable synthetic fibers cannot be degraded naturally in seawater.The resulting"white pollution"and"ghost fishing"problems have seriously threatened the marine ecological environment.In order to protect the marine ecological environment and reduce the"white pollution"and"ghost fishing"hazards caused by abandoned non-degradable fishing nets,The research and development of environmentally friendly and degradable fishery materials has become one of the major issues in the sustainable development of modern fisheries in my country.Degradable materials for fishing are being developed and tested in the fishery field,and some research and application results have been achieved.Montmorillonite(MMT)is one of the typical layered silicate minerals.A small amount(3%to 5%)of MMT can be added to the polymer to obtain a composite material with good performance.Nano modification is an effective method to change the structure and functional properties of degradable materials.In this paper,PLA is used as the raw material to study the fishing efficiency of the gill net woven by PLA fibers;in order to improve its fishing efficiency and optimize the performance of nanocomposite degradable fishing materials,surface-modified nano-montmorillonite(MMT)is used as the modification additive,and PLA/PBAT/MMT composite fibers are prepared by melt spinning.In addition,more easily degradable and cheaper starch(STR)is used as the main raw material,and MMT is used as the modification additive,and STR/HDPE/MMT nanocomposite fibers were prepared by melt spinning.The effects of MMT on the thermal properties,mechanical properties,dynamic mechanical properties and biodegradability of two composite fibers was studied.The results are as follows:(1)PLA fiber was prepared by melt-spinning method,we assessed the physical performance of monofilaments made from a biodegradable resin,polylactic acid(PLA),in the laboratory and compared and analyzed the fishing efficiency of gill nets made of PLA monofilaments and conventional PA monofilaments in sea trials conducted on Langya Island from September to October 2019.Results showed that the biodegradable PLA gill net captured 75%less Portunus trituberculatus but 90%more Pneumatophorus japonicus than the PA gill net.The total amount of catch by PLA gill net was slightly lower than that by PA gill net,and the fishing efficiency of PA gill net was approximately 60%higher than that of PLA gill net.Moreover,mechanical tensile tests showed that the mesh breaking strength of the two gill nets was both significantly reduced after the fishing operation.In addition,PLA meshes were more vulnerable to damage than traditional PA gill net due to the poor toughness and lack of elasticity and flexibility of PLA monofilaments.At the same time,the microscope picture showed that the damage of PA gill net appeared in the middle of the mesh,and PLA gill net appeared in the knotted.Furthermore,the breaking strength of PLA monofilaments was significantly lower than PA,so PA gill net meshes were more easily to be broken.Although PLA gill net is not as efficient as PA gill net in terms of fishing performance,it exhibits a potential advantage in reducing ghost fishing and plastic pollution in the ocean,so the usage of PLA gill net can be extended with so improvement on strength performance.(2)PLA/PBAT/MMT composite fibers were prepared by melt-spinning method,and the effect of MMT on the thermal properties,mechanical properties,dynamic mechanical properties and biodegradability properties of the PLA/PBAT/MMT composite fibers was studied.The results showed that after the introduction of MMT,the PLA melting temperature of the composite fiber did not change significantly,indicating that the introduction of MMT did not affect the PLA aggregate structure.However,with the increase of the MMT content,the melting temperature of the composite fiber PBAT significantly shifted to lower temperatures.The storage modulus of the composite fiber decreased,and the addition of MMT had no effect on the glass transition temperature(T_g)of PLA.Obviously,but the mechanical loss factor of the composite material decreases with the increase of MMT content.The breaking load and knot breaking load of the composite fiber decreased significantly,and first increased and then decreased with the increase of the MMT content.When the MMT content was 1.0%,the load of the composite fiber was the highest,the breaking load was 13.0 N,and the knot breaking load was 11.6 N.After 6 months of seawater degradation,the weight loss rate of composite fibers first increased and then decreased with the increase of MMT content.When the MMT content was 0.5%,the weight loss rate was 11%.After 4 months of soil degradation,the weight loss rate of composite fibers increased with the increase in MMT content.The increase in MMT content decreases.When the MMT content is 0.2%,the maximum weight loss rate is7%;the breaking load of the composite fiber after degradation shows a downward trend,the infrared spectrum absorption peak intensity is significantly reduced,the bond length becomes shorter,and the fiber is some substances are degraded.Therefore,the presence of layered MMT nanomaterials promotes the degradation of composite fibers.(3)Using starch as the main raw material,STR/HDPE/MMT nanocomposite fibers was prepared by melt-spinning method.The effect of MMT on the thermal properties,mechanical properties,dynamic mechanical properties and biodegradability properties of STR/HDPE/MMT nanocomposite fibers was studied.The results showed that the T_mof the nanocomposite fibers moved to low temperature and its processing performance was improved by introducing MMT,while the crystallinity of the nanocomposite fibers increased,and the breaking strength decreased.In addition,the addition of MMT significantly reduced the glassy storage modulus and internal loss of polyethylene,but had little effect on the starch phase.After 4 months of seawater degradation,compared with that of STR/HDPE fibers,the weight loss rates of STR/HDPE/MMT nanocomposite fibers increased by about 5%,and the fiber diameter decreased by 5%.After seawater degradation and soil degradation,the weight loss rate of STR/HDPE/MMT composite fiber is significantly higher than that of STR/HDPE fiber,and the surface of the fiber also decomposes significantly.This indicated that MMT also accelerated the degradation process of STR/HDPE fibers.This paper systematically studied the structure and properties of the MMT modified starch-based nanocomposite fibers,which can provide a reference for the development and application of the fishery degradable materials.