Study On The One-Step Continuous Molding And Performance Of Micro Irrigation Tape With Porous Structure Based On Extensional Rheology

Due to per capita water resources in our country continue to decline,micro-irrigation technology plays a vital role in improving water resource utilization,increasing agricultural production and income,and ensuring national food security.Although our country has made some progress in the development of water-saving irrigation devices,there are still defects such as complex manufacturing process,low molding efficiency,and difficulty in maintenance and recycling.In response to this problem,based on the team's self-developed eccentric rotor extruder dominated by the volumetric extension flow field,this article adopts the extrusion foaming blow molding method to prepared a new Low-density polyethylene(LDPE)-based and fully biodegradable polylactic acid(PLA)-based porous media micro-irrigation tape successfully,which continuous molding in a short thermomechanical process.The microstructure,hydraulic performance and other key properties were studied deeply.The main tasks as follows:First,the conveying characteristics and principles of the eccentric rotor extruder are analyzed.Based on the plastic extrusion characteristics dominated by volumetric extensional rheology,LDPE-based foam materials were prepared.In order to improve the cell structure,nano-carbon black(CB),LDPE2520 D,polystyrene(PS),dicumyl peroxide(DCP)crosslinking agent and other different material formulations were added into the matrix,which induces the inhomogeneity of the melt for extrusion foaming.Then the influence of compounding,blending and cross-linking on the structure and performance of polymer foam materials was explored.The results show that e Extrusion and foaming of multi-phase and multi-component materials in a volumetric extension flow field achieves good mixing and dispersion,significantly reducing cell size,increasing cell density and porosity,thereby improving cell structure and significantly improving foam performance..Secondly,using the biaxially stretched hole breaking mechanism in the foaming blow molding process extruded by eccentric rotor extruder to construct the porous multi-channel microscopic morphology inside the micro-filled tape,which can manufacture the porous microfilled tape with different porosity and open porosity,Its comprehensive performance and opening mechanism was well studied.Experiments show that either stretching or inflation can break the foam well,and the synergy of them can achieve higher hole breaking efficiency and more uniform openings;excessive stretch ratio and inflation ratio are both will reduce the porosity and open porosity;when the stretching ratio is 2.0 and the expansion ratio is 1.2,the porosity and open porosity reach the highest value;adding a compatible or incompatible second phase,crosslinking or nanocomposite can effectively improve the porosity and opening rate of the micro-irrigation tape,but the opening efficiency and mechanism of different material systems are different.Next,the hydraulic properties of the molded LDPE-based porous micro-irrigation tape,as well as the relationship between stretch ratio and inflation ratio,foam microstructure and hydraulic performance were well investigated.Besides,the seepage characteristics of the micro-irrigation tape was further analyzed.The results show that the relationship between pressure and flow rate of the porous micro-irrigation zone accords with the exponential relationship,and the fluidity index x is between 0.9 and 2.0.Small flow irrigation can be achieved at very low pressure,with good hydraulic performance and a large flow adjustment range;The higher the open porosity,the greater the fluidity index x and the permeability K,and the higher the permeation uniformity;the coordinated hole breaking of stretching and inflation can improve the open porosity uniformity and reduce the fluidity index of the porous medium micro-irrigation zone;Appropriate opening rate and irrigation pressure can improve irrigation uniformity.Finally,using the contentious extrusion foaming blow molding process proposed in this article,a fully biodegradable PLA/ Polybutylene succinate(PBS)/organic montmorillonite(OMMT)nanocomposite and its porous micro-irrigation tape were prepared.studied its mechanical properties,microstructure,hydraulic properties and other comprehensive properties,and explored the influence of PBS and OMMT on the structure and performance of materials.Comprehensive properties such as mechanical properties,microstructure,and hydraulic properties are also studied,and the influence of PBS and OMMT on the structure and properties of materials were explored.Experiments show that PBS forms in-situ sub-micron fibers,which is beneficial to the strengthening and toughening of materials;OMMT achieves good dispersion,intercalation and peeling in the tensile flow field,and is mainly distributed in PBS and on the PBS/PLA interface and the rest distributed in the PLA in the exfoliated state,greatly increasing the cell density and porosity,and reducing the cell size and apparent density.Its hydraulic performance is similar to that of LDPE-based porous micro-irrigation tape.There is an exponential relationship between pressure and flow,and the flow index x is between 0.9 and 1.7.The porous micro-irrigation tape prepared in this article has the advantages of short processing thermal history,simple forming process,low manufacturing cost,good seepage characteristics and large flow adjustment range,etc.It can realize adaptive micro-flow energysaving irrigation,which is great for promoting porous micro-irrigation tape.It has very important practical significance to promote the development of water-saving irrigation equipment and methods in China.