| Natural fiber is a kind of widely exists in the nature of renewable resources,is one of the biggest organic matter of nature reserves.With the shortage of energy and environmental pollution intensifies,the development and utilization of natural fiber is becoming a hot spot of research.Nano-cellulose has high strength,high modulus,high crystallinity,excellent photo electromagnetic properties and good biocompatibility,so in electronic devices,biological medical material,reinforced composites have great potential for application.At present,Preparation of nano-cellulose by chemical method is widely used,however,the process is complex,the efficiency is low,the acid pollution is serious.The high energy consumption of mechanical method limits the development of nano-cellulose industry.This experiment is aimed at using subcritical ethanol water and subcritical ethanol to pretreat wood pulp fibers and combine the mechanical ball to prepare nano-cellulose.In this study,the effect of subcritical ethanol/water pretreatment process on the properties of bleached broadleaf pulp cellulose was investigated by a high temperature and high pressure reactor.The morphological characteristics,chemical structure and crystallinity of the wood pulp cellulose obtained from different pretreatment temperature,time and volume ratio of alcohol to water.Cellulose were analyzed by SEM,FI-TR and XRD.The results showed that as the pretreatment temperature was 180 ?,the time was 180 min and the volume ratio of alcohol to water was 7:3.The yield of purified pulp was 93.30%,while the purification yield of cellulose was 87.79%,which was 8.43% higher than that of raw material.SEM showed that the surface of the cellulose was wrinkled and exposed to a large number of microfibrils,while XRD showed that the crystallinity of the cellulose reached 71.64%,and about 22.15% higher than the raw material.Subcritical ethanol ultra-low acid pretreatment bleached broadleaf pulp cellulose combined with mechanical method to prepare nanofiberillated cellulose.As the pretreatment temperature increased,the rate of purified pulp decreased gradually,from 89.18% to 50.17%;Cellulose purification rate increased,from 84.57% to 89.78%.As the pretreatment time was extended,the rate of purified pulp decreased gradually,from 63.33% to 50.17%;The cellulose purification rate increased from 85.36% to 89.78%.The analysis of XRD found that the cellulose structure wasnot damaged.As the pretreatment increases with temperature,the crystallization index decreased after the first increase.The particle size of the NFC was gradually reduced,SEM showed that the diameter was between 20 nm and 50 nm,particle size was 500 nm to 1000 nm and the particle size was distributed uniformly;140 ? pretreatment,with the extension of pretreatment time,the particle size was basically maintained at about 600 nm,SEM showed that the pretreatment time 180 min,NFC was the most uniform particle distribution.The ball mill time was prolonged,it will produce the reunion phenomenon,the particle size increased slightly,the particle size was500 nm to 600 nm.TG/DTG test and analysis,found that bleached broadleaf pulp cellulose of subcritical low acid pretreatment and NFC thermal stability were worse than the raw material,NFC thermal stability was better than broadleaf pulp cellulose after pretreatment.Subcritical ultra-low acid pretreatment with bleached broadleaf pulp cellulose combine mechanical method to produce NFC.NFC possess enhance effect on PVA film,and with the increment of adding,the tensile strength increased firstly and then decreased.The transparency showed a downward trend.The SEM characterization of reinforced PVA films was also found that nanofiberillated cellulose was distributed evenly in film. |
PDF Full Text Request