A Study On The Preparation Technology And Mechanism Of Hybrid Pennisetum Straw Fiberboard In Guizhou Province

Residuals from crops such as straw are considered as promising natural cleaning materials and can be used to make straw based panels.Hybrid Pennisetum is a kind of perennial grass,which is widely planted in Guizhou.Its annual output reaches more than 1 million tons.Hybrid Pennisetum has the advantages of short growth cycle and can overcome extreme growing environment.The high added value of hybrid Pennisetum straw has not been fully exploited.It is very important to develop efficient utilization methods for the straw of hybrid Pennisetum.Hybrid Pennisetum straw has a high cellulose content,which makes it a great potential as a kind of ecofriendly material.This paper mainly explores the mechanism and the best process in the manufacturing process of the fiberboards,which provides a theoretical basis for the recycling of the discarded straw of the plant.The main research results of this paper are as follows:(1)Fiberboards were prepared by hot pressing process.The size of the raw material was about 1-2cm,and the solid content of the modified urea formaldehyde resin adhesive was about 50-60%.The effects of pressing temperature,sizing amount,pressing time and density on the mechanical properties of medium-density-fiberboards were investigated.The parameters of best process were as follows:the sizing amount was 10%,the density was 650kg·m-3,the hot pressing temperature was 195℃,and the pressing time was 7.5min.The static bending strength is 12.33MPa,the nail holding force is 1313N,the elastic modulus is 2573MPa,the water absorption rate is about 76.5%,the thickness expansion rate is about 20%,and the formaldehyde emission is at E0 level.All the indexes of the fiberboards were in full compliance with the national standards.(2)The influence of pressing temperature on the microstructure and physicochemical properties of fiberboards were discussed,and the heat transfer mechanism and influencing factors during the hot-pressing process were also studied.The bidirectional effect of hot-pressing temperature on the mechanical properties of the fiberboards was confirmed.When the pressing temperature was lower than 195℃,the mechanical properties of the fiberboards were enhanced by heating,while when the temperature was higher than 195℃,the mechanical properties of the fiberboards were weakened.On the one hand,the increase of hot-pressing temperature can promote the solidification of the modified urea formaldehyde resin in the fiberboards,and on the other hand,it can promote the thermal degradation of cellulose,hemicellulose and lignin in the fiberboards,too.