Comprehensive Performance Analysis Of Pet Netting And Its Application In Liftable Cages

In fishery production activities,fishing gear is a general term for various tools directly used to catch and harvest economic animals in the waters,and the country roughly divides fishing gear into 12 types,and net fishing gear plays an important role in it.Cut nets or nets mounted on fishing gear are called net jackets or fishing nets.The material types and technology of fishing nets are directly related to the safety design of net fishing gear,and the research and development,inspection and application of various new fishing net materials are issues that scientific researchers continue to study.Due to the increase in the world’s demand for aquatic products,the fishing of wild fish can no longer meet human needs,and cage aquatic product farming has become an important part of fishery production.Deep sea aquaculture is an important part of aquatic aquaculture,China’s development compared with foreign countries still have a certain gap,need scientific researchers to study it more in-depth,and net clothing is a key part of the deep sea aquaculture cage,in the past cage application commonly used netting clothing is PE(polyethylene)netting clothing,UHWMPE(ultra-high molecular weight polyethylene netting clothing),metal netting clothing,etc.,among them,polyethylene netting density is small,rich raw materials,low price,strong corrosion resistance and other advantages have been widely used,However,its disadvantage is that when used in deep seas,the power is not reliable and easy to be torn by large marine organisms,so researchers are also looking for ways to enhance its performance;Ultra-high molecular weight polyethylene netting has high strength and good performance,but its unit price is very high,for some aquaculture companies,it is not cost-effective to use this kind of netting in a large area,and the above two kinds of netting clothing are flexible,in the process of cage culture,it will be deformed by the impact of the waves,reduce the cage volume ratio,thereby affecting the growth of organisms in the breeding area;For metal netting,the netting is strong and not easy to deform,but its disadvantage is that the weight of the netting is large,it is not convenient to install and replace the netting,and the metal is in the seawater environment for a long time,once the surface coating falls off,the metal is in direct contact with seawater,and it is easy to be corroded by seawater,which may lead to damage to the cage and potential safety hazards;Therefore,scientific researchers are also continuing to find new netwear materials to replace or improve these commonly used deep-sea cages,and develop deep-sea aquaculture cages.PET material is a kind of polymer general name,in recent years with its excellent chemical properties gradually used in the field of fishery,fishing net made of this material,high strength,small deformation,corrosion resistance,aging resistance;Its smooth surface makes it more difficult for fouling to grow on it,which can prevent fouling to a certain extent,and this smooth surface and the hexagonal structure of the mesh jacket make the mesh clothing less stressed in seawater.Taking PET material as the starting point,this paper mainly explores the changes of its mechanical properties under various environmental conditions,and obtains that the strength loss rate of PET monofilament under normal temperature lighting conditions is extremely small,and the strength retention rate after 2000 h is more than 90%.Through the seawater immersion test,it can be obtained that three months of seawater immersion has almost no effect on the fracture strength of PET mesh.Through the wear test of PET monofilament,it is known that the wear resistance of PET monofilament is not good,so if this material is used in the fishery production process,direct friction between the material and other obstacles should be avoided as much as possible;Through the mesh aging test,under the combined action of light,heating and water bath conditions,the strong loss rate of this mesh material decreases rapidly,so when using monofilament and mesh made of this material,attention should be paid to its use conditions;Four PET mesh with different specifications and ultra-high molecular weight polyethylene mesh of the same specification were placed in the sea area of Wenzhou,and eight kinds of mesh clothing were sampled and analyzed every other month,and the antifouling effect of PET mesh and ultra-high molecular weight polyethylene mesh of the same specification was compared and verified from three different angles.The analysis results show that due to the smooth surface of PET mesh,it is difficult for fouling organisms to attach to it,and the number of fouled organisms on PET mesh is less than that of ultra-high molecular weight polyethylene mesh of the same specification in the stage of rapid growth of fouling organisms.And because the growth of fouled organisms in winter is relatively slow,and the underwater undercurrent is more rapid,the fouled organisms on the PET net can be quickly washed down by the current,so the anti-fouling effect of PET net clothing is relatively good,which is more suitable for the field of fishery.A liftable cage is designed,the hydrodynamic experiment is carried out in the moving sink,the water flow velocity of the sink is used as the only independent variable,the force of the cage increases with the increase of the water flow speed,and the increase trend conforms to the change of the exponential function,but the force growth curve is analyzed,and the force growth rate of ultra-high molecular weight polyethylene mesh of diamond mesh is significantly faster than that of PET mesh of hexagonal mesh;When the height of the cage body is used as the only independent variable,when the water flow speed is small,the cage body is located at a deeper sea surface and is subjected to greater force.When the wind and waves are large,the force of the cage placed in the shallower part of the sea surface is greater than the force placed in the shallower part of the sea surface;As the only independent variable,it can be obtained that when the angle between the cage facing surface and the water velocity is 90°,the force of the cage is the smallest,and when the angle is 45°,the overall force is the largest.When the mesh material is used as the only independent variable;Three specifications of PET mesh and three specifications of ultra-high molecular weight polyethylene mesh were analyzed,and the ratio of mesh line area and the force ratio of mesh clothing were compared,and the force of PET mesh was small.In this paper,the properties of PET materials as net clothing are analyzed and tested,which provides certain theoretical and technical support for the fishery field of PET materials.