Study Of Bamboo Based Container Flooring Centrifugal Dipping Process

Container flooring as a typical special plywood,because it is the main component of the weight of the cargo carried in the container,it is required to have the safety and necessary service life and must have a greater physical strength.Therefore,the vast majority of container flooring are made of tropical broad-leaf hardwood,need to consume a lot of high quality timber.With the vigorous development of modern transport industry,China has become the first base of container flooring production.But China is a country where forest resources are scarce,and the contradiction between timber supply and demand is outstanding.The most urgent thing is to find a material to replace the apitong and other tropical broad-leaved hardwood.China is the most abundant of bamboo resources in the world,bamboo area and volume and production ranks first in the world.Compared with other plants,bamboo has a short growth cycle,fast germination,high strength,good toughness and other characteristics.As long as rational use of bamboo,it can be used to produce bamboo-wood composite container flooring,it can ease the contradiction between high quality timber supply and demand and tropical rain forest ecological deterioration and other issues.At present,bamboo-based container flooring is the most important form of bamboo-wood composite container flooring.In the production process,bamboo need to be dried before dipping,and need to dried again after dipping,resulting in high energy consumption and low production efficiency.In addition,the existing dipping process,it take a long time to dip,and resin uneven distribution,resin film thickness is varies.Therefore,we need to further improve the production process of bamboo based container flooring to improve the quality of the flooring and meet the national energy-saving emission reduction requirements.This paper studies a new process of bamboo dipping in the process of bamboo based container flooring production:centrifugal dipping process,which includes centrifugal dipping and filter.The centrifugal dipping and filter technology of bamboo were studied by orthogonal test and response surface test to explore the superior process parameters,and analyze the mechanism of centrifugal dipping.In addition,the drying process of bamboo after centrifugal filter was discussed in detail,and the optimum drying process was optimized.The results of the previous experimental study show that after centrifugal dipping and filter,resin liquid distribution is more uniform,dipping time is shortened;easy to control the content of resin adhesive used,and the adhesive is fully effective use,improving the use of adhesives;the drying time is shortened and the drying rate is improved.Not only effectively shorten the production time,but also reduce the production costs,which is consistent with the development trend of today's enterprises.At the same time,use various characterization methods to analysis the wetting properties of bamboo surfaces,the distribution characteristics of phenol-formaldehyde adhesive resin,the change of bamboo composition and the microcrystalline structure of bamboo fiber.Contact angle Analyzer(DSA30)to measure the wetting properties of bamboo surfaces;scanning electron microscopy(SEM)to observe the microstructure of bamboo fiber;X-ray diffraction(XRD)to analysis the microcrystalline structure and relative crystallinity of bamboo fiber;fourier transform infrared spectroscopy(FTIR)was used to analyze the composition of bamboo.The main conclusions of this paper are as follows:(1)Through the variance analysis and the range analysis of the orthogonal test results,the main factors affecting the phenol-formaldehyde adhesive resin content of the centrifugal dipping process were:glue concentration>dipping time>speed.The influence of the concentration of glue on the centrifugal dipping resin content was significant,and the effect of dipping time and speed on the centrifugal dipping resin content was not significant.The optimum technological parameters:speed is 200·min-1,dipping time is 4min,glue concentration is 40%.(2)Response surface test results show that X1,X2,X3 and X32 had a significant effect on the resin content of bamboo centrifugal filter,and X1X2,X1X3,X2X3,X12,X22 had no significant effect on the resin content of bamboo centrifugal filter.Considering the influence of all aspects,the influence of each factor on the resin content of bamboo centrifugal filter was in the order of X3>X2>X1,that is,glue concentration>filtering time>speed.By analyzing the binary regression model,providing an optimal process parameters for centrifugal filter:speed is 100r·min-1,centrifugal time is lmin,glue concentration is 40%,and based on the response surface test,the predicted value of the phenol-formaldehyde adhesive resin content was 16.19%.(3)The orthogonal test results showed that the affects of the moisture content and the volatile content placement order based on the size of the factors were:drying temperature>drying time>resin content.The effect of drying temperature on the moisture content of bamboo was significant,and the effect of drying time and resin content on the moisture content of bamboo was not significant.The effects of drying time,drying temperature and resin content on the volatile content of the phenol-formaldehyde adhesive resin after drying were not significant.Comprehensively analysis the effects of drying process on the moisture content of bamboo and the volatile content of resin,a set of preferred drying process parameters:drying time is 120min,drying temperature is 75?,resin content is 14%.(4)Resin adhesive can well wet bamboo,with the prolongation of time,the contact angle between resin and bamboo was smaller,and reached a stable state at 125s.Therefore,it can be concluded that as time increases,the content of resin which into the bamboo was getting less and less,and finally reached the saturation state.(5)By observing the scanning electron microscopy found that the parenchyma was thin or elliptic,the pore size was about 10?40?m,the cell cavity was large and clean,the cell wall was thinner,the cell number was large and closely arranged,the cell gap was obvious visible.On vertical section,it can be seen closely arranged,the length of the parenchyma cells,the cell cavity was almost rectangular shape,the length of cell about 50?300?m,the cell wall distribute some irregular small holes.After the centrifugal dipping,on the bamboo cross section,it can be seen a large number of phenol-formaldehyde adhesive resin evenly distributed closely in the basic tissue parenchyma cell cavity,and almost completely filled with resin.On the longitudinal section,it can be seen a large number of resin adhesive effectively adhere to the bamboo surface,but the resin in the bamboo surface produced a different degree of accumulation phenomenon,resulting the film thickness was uneven and the distribution of resin was uneven,there was a clear crack phenomenon,and the crack was large.After the centrifugal filter,resin adhesive on the cross section of the bamboo pulp circulate around the inner wall of the cell cavity,or close to the side of the cell cavity;under centrifugal force,resin was broken and the resin fluid was flattened on the inner wall of the cell cavity,it was seen that the resin fluid enters into the cell wall of the parenchyma cells through the pits in the inner cell wall and flows into the cell gap so that the distribution of resin adhesive in the bamboo was more dispersed In addition,the phenol-formaldehyde adhesive resin content was relatively reduced,because a part of the excess resin was filtered and Recycled.Based on the above analysis,it can be seen that the dipping effect of bamboo after centrifugal dipping and filter was obviously improved.(6)Compared with the non-dipped bamboo,the results show that after centrifugal dipping and filter of the cellulose microcrystalline layer spacing slightly changed,but the bamboo fibers maintained the main structure of the original cellulose crystals.The relative intensities of the diffraction peaks of cellulose in the samples before and after centrifugal dipping and filter have changed to some extent.After calculating the relative crystallinity of each sample,it was found that the relative crystallinity of the bamboo cellulose after the centrifugal dipping was slightly improved,and the relative crystallization of the bamboo cellulose after the centrifugal filter was decreased to a certain extent,but the change range was very small.This is mainly due to changes in the content of resin adhesive caused.(7)By analyzing the fourier transform infrared spectroscopy(FTIR)spectra of the samples,it was found that the absorption band at 1736.66cm-1,1633.00cm-1,1512.95cm-1,1458.95cm-1,1423.75cm-1 was the bamboo fiber and lignin C-H surface bending vibration,aromatic skeleton vibration;wave number at 1379.39cm-1,1334.56cm-1,1246.81cm-1,1160.50cm-1,1047.20cm-1 and other absorption zone with the main corresponding of the bamboo cellulose and hemicellulose C-O stretching vibration,C-H in-plane bending vibration,acetyl oxygen bond stretching vibration.In the bamboo fingerprints,compared with the non-dipped bamboo,there was no significant change in the series of characteristic peaks of the dipping bamboo.Indicating that the basic structure of cellulose after dipping and filter did not change significantly.(8)Through the stability test,it can be seen that the physical and mechanical properties of bamboo based container flooring by centrifugal dipping,filter and drying bamboo with eucalyptus composite were all meet the requirements of the relevant national standard.The results show that the optimum centrifugal dipping process,the centrifugal filter technology and the drying process have a good stability and availability,setting parameters with some reference value,and it can be used for direct the actual production.