Study On The Effect Of Pulp Molded Microstructure On Product Performance

Pulp molded products are made from recycled resources such as waste paper,straw,and residual wood materials.It has a three-dimensional structure through vacuum filtration and hot-pressing drying.The product can lower the usage of wood and oil resources because it can be recycled and reused numerous times.Moreover,it is degradable after use,making it the best green packaging alternative to plastic.However,current research on pulp molded products has been mostly focused on the influence of macroscopic structural parameters on its performance,while lacking in-depth studies on microstructural formation mechanisms,microstructures,and their effects on mechanical properties.Therefore,this paper aimed at exploring the correlation between the microstructure characteristics of fibers and the mechanical properties of products from both micro and macro perspectives:(1)The microstructure and mechanical action mechanisms of pulp molded materials were analyzed,and the microstructural properties were tested.The molecular structure and effects of the main chemical components of the pulp molded material were analyzed.Microscopic mechanical interactions between fibers,including hydrogen bonds,van der Waals forces,capillary forces,electrostatic interactions,mechanical interlocking,and molecular diffusion,were summarized.And the reasons and mechanisms for these forces were explored.Microstructural properties such as fiber morphology,composition,specific surface area,molecular structure,and crystallinity were tested,which are helpful for understanding the micro mechanical mechanism of pulp molded products.(2)Based on the spring-mass model,a beam fiber network was established to analyze the effects of material microstructure and properties on the mechanical properties of network materials.The results showed that the bonding strength and fiber failure strength were positively correlated with the maximum force,elongation and the tensile index of the network.And the increase of these factors made the network tend to toughness failure.For fiber stiffness,the maximum force and the tensile index of the network increased within a certain range as the stiffness increased.But when the stiffness was too high,local concentrated damage and brittle failure may occur,resulting in a decrease of the maximum force.The increase of fiber size and stiffness can improve the maximum force and the tensile index but decrease the elongation,as they are factors that resist network deformation,making the entire network tend to brittle failure.Among these factors,the bonding strength between fibers has the most significant impact on the resistance against tensile index.(3)The microstructure of flat products under different conditions was tested and analyzed,and its macroscopic mechanical properties were measured.The experimental and simulation results were compared.The effects of refining conditions,grammage,and pulp type on micro-mechanical properties such as fiber bonding strength and fiber characteristics,as well as macroscopic mechanical properties were explored.Experiments under different preparation conditions had shown that the highest tensile index,zero-span tensile index,and Z-direction bonding strength were obtained when wood-sugarcane pulp were mixed at a ratio of 1:1 and refined for 14 min,reaching 72.13 N m/g,104.26 N m/g,and 218.45 k Pa,respectively.This was attributed to the high bonding strength of sugarcane pulp and its good compatibility with high-strength wood pulp,which improved the material properties.The results showed that the proportion of short fiber pulp had the main influence on various properties,and the bonding strength had a higher impact on paper properties.And the performance change trend obtained through hybrid simulation using fiber networks in the article is consistent with the experiment.Further statistical analysis of all data showed that the relative coefficient between the Z-direction tensile strength and tensile index was 0.700,which was higher than the fiber strength index of 0.336.This demonstrated that the paper’s tensile strength was more influenced by fiber bonding strength,which was consistent with the simulation results,verifying the reliability of the model.(4)The effect of different microstructural characteristics on the mechanical properties of three-dimensional pulp molded products was disgusted,and the simulation analysis was performed.Firstly,the forming process parameters of pulp molded products were analyzed,with an optimal refining time of 30 min,optimal forming parameters of a hot-pressing pressure of 6 MPa,hot-pressing temperature of 160℃,and holding time of 2 s.Three different fiber raw materials with different microstructural properties of wood pulp,sugarcane pulp,and a mixture of wood-sugarcane pulp(1:1)were prepared under optimal process conditions.The mixed raw material had the highest tensile index,stiffness,fracture resistance index,static compression limit load,and yield strength,with values of 26.53 N m/g,472.32m N,2.58 k Pa·m~2/g,492.03 N,and 2.08 MPa,respectively.The compression buckling deformation of the three different raw materials for fiber molding was simulated based on their material properties.Under the same deformation conditions,the mixed wood-sugarcane pulp product had the strongest bearing capacity and stable structure.This was because the mixed raw material combined the high bonding strength of sugarcane fibers with the high strength of wood fibers,which improved the strength performance of the product.