| This paper systematically studied the effects of hydrothermal pretreatment,Compression process and heat-treated on the chemical properties,physico-mechanical properties and the color of compressed Cryptomeria fortune Hooibrenk wood.The main findings are as follows:1.Hydrothermal pretreatment has a great influence on the mechanical strength of compressed Cryptomeria fortune Hooibrenk wood.The MOE and MOR,compressive strength increased 23%and 21%,15%by the first 4h of hydrothermal treatment.Then its strength has a more substantial decline and gradually stabilized.Hydrothermal pretreatment has little effect on the recovery rate of compressed wood,with the increase of treatment time,the recovery rate gradually decreased,to 10h cumulative decline of 5.94%.2.The holding time has a certain influence on the mechanical strength index of compressed wood.When the holding time is less than 40min,the mechanical strength indexes of compressed wood are increased less than 6%.When the holding time is more than 40min,the indexes are greatly reduced.The effect of holding time on the recovery rate of compressed wood is not significant.With the prolonging of packing time,the recovery rate is gradually reduced,When the holding time is 50min,the response rate decreases by 3.02%.3.The compression ratio has a great influence on the mechanical strength indexes of compressed wood.With the increase of the compression ratio,the mechanical properties of the mechanical properties increased significantly,but the compression rate was 60%,the mechanical strength of the increase was significantly decreased.At then the MOE and MOP,compressive strength were 93.34Mpa,11708 Mpa,43.72 Mpa.The rate of compression has a certain effect on the recovery rate of compressed wood.With the increase of compression rate,the recovery rate of compressed wood is decreasing as a whole.When the compression ratio is 60%,the recovery rate of compressed wood is 83.48%,and the cumulative decrease is 10.89%.4.The mechanical properties and the response rate of the compressed wood were greatly affected by heat treatment.With the increase of heat treatment temperature,the flexural strength and compressive strength of compressed wood tend to decrease as a whole,and the decrease is increasing.When the heat treatment temperature is higher than 180℃,the flexural strength and compressive strength will decrease by more than 15%and 13%,and the strength decreases to 42.45%and 33.27%respectively at 220℃.The flexural modulus of the compressed wood decreases with the increase of the heat treatment temperature,and decreases at 25℃ at 220℃,and decreases by 43.62%compared with the control group.With the increase of heat treatment temperature,the recovery rate of compressed wood decreased rapidly.When the heat treatment temperature exceeded 180℃,the recovery rate decreased by more than 10%.When the heat treatment temperature is 200℃,the decrease is 37.46%.The recovery rate is only 5.99%when the heat treatment temperature is 220℃.5.After compression processing,its brown cellulose content decreased by 1.46%,lignin content increased by 0.25%.With the increase of heat treatment temperature,the content of cellulose was decreased,and when the heat treatment temperature was higher than 160℃,the decrease of brown cellulose content began to increase.Lignin content increased.The increase in temperature levels was 0.04%,0.56%,0.93%and 1.15%,respectively.The content of 1%NaOH extract of Cryptomeria chinensis was increased by 1.17%.On the whole,the 1%NaOH extract content increased with the increase of temperature,the increment was not obvious.The 1%NaOH extract content increased by 1%at 140℃ compared to 140℃.6.After heat treatment,the color of the compressed wood gradually deepened,from light brown to reddish brown to red brown,and finally become dark brown slightly red.With the increase of heat treatment temperature,L*,b*,a*and(?)L*,(?)a*and(?)b*decrease,and △E*increases.When the heat treatment temperature is higher than 160℃,the brightness index decreases obviously,the level decreases more than 12%,and the brightness index decreases by 27.10%at 220℃.The decrease of the yard value in the treatment temperature was 3.03%,8.35%,7.68%and 11.14%respectively.The chromaticity index decreased by 6.41%,10.35%,14.61%and 17.15%respectively.Heat treatment temperature exceeds 200 ℃,the color increase is extremely obvious. |
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