Effect Of Warm Pressing Process On Properties And Color Of Wood Flour Compacts

With the development of economy,forest products have penetrated into all aspects of our lives,but a large amount of forestry residues are produced at the same time in the production and processing of wood products,and the proportion of these residue accounts for about 40%of commercial and non-commercial timber.The effective use of forestry residues not only helps reduce the dependence on wood,but also increases the added value of forest products.This article is based on the application of forestry residues.The warm compaction technology is used to make poplar powder into a material without adhesive.Single factor experiments and orthogonal experiments were carried out.Through multiple regression analysis and neural network methods,the influence of process parameters on the mechanical properties and surface color of poplar powder compacts was discussed during the forming process,and the mathematical model between the process parameters and the mechanical properties and surface colors of the compacts were built.These can provide a reference for improving the product quality.Research of this study indicates as follows:(1)The influence of process parameters on the mechanical properties of compacts was discussed.The effect of forming temperature on mechanical properties is higher than that of forming pressure and holding time.The influence of the increase of the forming process on the static bending strength tended to increase initially and then decrease,and the maximum appeared at a certain position in the middle.However,the influence of increasing forming technology on the surface hardness tended to continue to increase.180℃ is the critical temperature at which the performance of the compact changes significantly.(2)The effect of process parameters on the surface color of the compact was discussed.The effect of forming temperature on mechanical properties was higher than the forming pressure and holding time.In the process of warm compaction,as the process conditions increase,the surface color of the compact gradually became darker.The color brightness value in the surface of the compact decreased with the increase of process conditions.The red-green product value showed a parabolic change trend.The effect of forming temperature and other process parameters on the yellow-blue product value was slightly different.And there was an increasing trend in the overall color.(3)Through multiple regression analysis and BP neural network,mathematical models between the mechanical properties,surface color and process parameters of the green compact were established respectively.In general,it was found that the R of the BP neural network model was relatively higher than the multiple regression model,The average error value of the neural network model was relatively lower than that of the multiple regression model,especially when predicting the red-green product value,but when predicting the lightness value and the overall color difference,the multiple regression model and the BP neural network model had better prediction effects.,And the R of both models is greater than 0.9,the average error value is less than 10%.(4)Infrared analysis results showed that hemicellulose,cellulose and lignin were greatly affected by process parameters during the warm compaction process,especially the forming temperature.Hemicellulose and cellulose degraded to generate a large number of colored substances,which makes the surface color of the green compact darker.The side chain of lignin also degraded,resulting in a large number of chromogenic and color-assisting groups,resulting in a change in the surface color of the green compact.