| With the application of synthetic fiber materials in fishing gear,the threat of micro-plastic pollution and"ghost fishing"to marine ecological resources is becoming increasingly serious.In order to protect the marine ecological environment,it is particularly important to create biodegradable materials suitable for fishing gear with high ghost fishing frequency.Therefore,the development of environmentally friendly materials with low price,excellent comprehensive performance and controllable degradation performance will be the focus and difficulty of future research on fishing gear materials.The research and development of degradable materials and their application in domestic and foreign fisheries can help the high-quality development of modern fisheries in China.Polyadipic acid/butylene terephthalate(PBAT)is a new type of fully biodegradable aliphatic aromatic copolyester with good thermoplasticity and biodegradability.It is the most industrialized and widely used biodegradable material in the research of biodegradable materials.However,due to the presence of aromatic polybutylene terephthalate(PBT)segments in the molecular chain,the degradation rate is relatively slow,the crystallinity is low,the viscosity is high,the adhesion phenomenon is easy to occur,and the price is relatively expensive.The above factors limit the market development and application of PBAT.Natural polymer materials,such as cellulose,starch and chitin,are abundant in nature,widely sourced and renewable,and can be used as biodegradable materials.Among them,starch has a wide range of sources,low cost and other advantages.It can be completely biodegradable to carbon dioxide and water,and has excellent biodegradability.It is considered as a natural renewable material for environmental protection.In recent years,the research work on biodegradable materials for fishing at home and abroad has become increasingly mature and perfect,which is expected to solve the problem of"ghost fishing".As a common passive fishing gear.Crab cages are easy to lose,and are one of the fishing gear types that cause the highest frequency of"ghost fishing".The serious impact on the marine environment and economic losses caused by this are immeasurable.Therefore,it is of great significance to try to use biodegradable materials in the production of crab cages.In this paper,PBAT monofilament and PBAT/starch composite monofilament were prepared by melt spinning with PBAT and starch as the main raw materials.On the basis of the comparative study of the thermal,mechanical and dynamic mechanical properties of the two monofilaments,the effects of different seawater temperature and p H conditions on the degradation properties of the two monofilaments were discussed;In addition,through the sea fishing experiment and"ghost fishing"simulation experiment,the differences in fishing efficiency of conventional polyethylene crab cage,PBAT crab cage and PBAT/starch crab cage,as well as the ability of three crab cages to solve"ghost fishing",were compared.The results are as follows:(1)Biodegradable PBAT monofilament and PBAT/starch composite monofilament were prepared by melt spinning.The composition,surface morphology,thermal properties,mechanical properties and dynamic mechanical properties of PBAT monofilament were studied to explore the effect of starch addition on PBAT monofilament.The results showed that with the addition of starch,the composite monofilament T_m introduced into starch moved to low temperature,the crystallization melting peak widened,the crystallinity reduced,and the glass transition temperature of the PBAT/starch system reduced,indicating that starch had a significant impact on the flexibility of the molecular chain of the PBAT/starch composite system.When the temperature is lower than 50℃,the E’of PBAT/starch composite fiber is significantly lower than that of PBAT fiber,and the rigidity is significantly lower;The loss factor is improved.The addition of starch reduced the breaking strength of PBAT monofilament by 54.40%and increased the breaking elongation by 33.65%.The strength retention rate of PBAT/starch composite monofilament nodules is much higher than that of PBAT monofilament.Through Fourier transform infrared spectroscopy(FTIR)analysis,it was found that the two components in PBAT/starch composite monofilament only combined with each other through external force,without chemical reaction.In addition,under the same friction conditions,the retention rate of PBAT/starch composite monofilament is higher than that of PBAT monofilament,indicating that the wear resistance of PBAT degradable monofilament has been improved to a certain extent after adding starch.Although PBAT/starch composite monofilament is inferior to PBAT monofilament in breaking strength,it has potential advantages in toughness,nodule strength retention and wear resistance.Therefore,it is necessary to conduct more in-depth research on improving the overall performance of PBAT/starch composite monofilament.(2)The thermodynamic,mechanical properties,degradation weight loss,infrared spectrum and microstructure changes of PBAT fiber and PBAT/starch composite monofilament degraded for 5months in different artificial seawater degradation environments were compared and analyzed through laboratory simulated degradation experiments.The results showed that the addition of starch made the T_m of PBAT composite monofilament move to low temperature,and the crystallization melting peak became wider,indicating that the introduction of starch reduced the degree of crystal perfection;In terms of mechanical properties,the breaking strength of monofilament decreased to a certain extent,but the nodule strength retention rate increased from 63.86%to 97.56%;The positions of the infrared absorption peaks of the two monofilament initial samples are generally consistent with those of the characteristic peaks of pure PBAT and pure starch reported in previous studies.In addition,the effects of seawater temperature and p H on the seawater degradation performance of the two fibers were also studied.After the addition of starch,the degradation performance of monofilament was significantly improved,the average weight loss rate increased to 4.92%,the surface erosion increased,and the holes and cracks deepened;However,with the increase of temperature and p H value in the degradation environment,the degradation rate of monofilament is accelerated.According to the weight loss rate and degradation kinetics equation of degradation time in different degradation environments,the degradation coefficient increases from 0.157 in the neutral state at 20℃to 0.359 in the alkaline state at 50℃.This experiment systematically studied the seawater degradation performance of starch-based PBAT composite fiber,which can provide reference for the development and application of new degradable materials for fishing.(3)The fishing efficiency of conventional polyethylene crab cage,PBAT crab cage and PBAT/starch crab cage was studied by using single factor analysis of variance(ANOVA)through marine fishing experiment and"ghost fishing"simulation,and the catch was counted;At the same time,in order to simulate the ability of three kinds of crab cages to solve the"ghost fishing"problem,the degradation process of the mesh in the sea water was combined with the escape rate of Portunus trituberculatus,and the damage and mortality of Portunus trituberculatus during the escape experiment were observed.The results showed that the catch was mainly composed of Portunus trituberculatus,Portunus erythrostellatus and Charybdis japonica.The results showed that there was no significant difference in the fishing efficiency of the three crab cages in the experiment,indicating that the fishing efficiency was not easily affected by the tested crab cage net coat species;The average fishing efficiency of polyethylene crab cage in the control group was 0.11kg/h,the average fishing efficiency of 1-PBAT degradation crab cage in the experimental group was 0.096kg/h,and the average fishing efficiency of 1-PBAT/starch degradation crab cage in the experimental group was 0.13kg/h;In addition,after three months of seawater degradation,the weight loss rates of polyethylene mesh,PBAT mesh and PBAT/starch mesh were 6.6%,17.27%and 21.34%respectively;Polyethylene mesh is free of wear,while PBAT mesh is slightly worn,and PBAT/starch mesh is severely damaged;There is a significant difference in escape rate between polyethylene crab cage,PBAT crab cage and PBAT/starch crab cage.The escape rate of Portunus sinensis in degradable crab cage is significantly higher than that in polyethylene crab cage,but there is no significant difference between the two degradable crab cages.No dead individuals were found in the crab cage,but Portunus trituberculatus had different degrees of limb damage.The research shows that the fishing efficiency between the degradable crab cage and the conventional crab cage is equivalent,and in the simulated"ghost fishing"experiment based on the escape rate,it can be seen that the degradable crab cage has a certain ability to solve the"ghost fishing"problem. |
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