Preparation And Properties Of Coir-based Composites

Coir fiber is a rich and renewable biomass resource.Except for a small amount of coir fibers,which is used to produce low value-added products,a large amount of coir fibers is discarded,causing environmental pollution and resources waste.This article would find new ways to utilize coir fibers by chemical treatments.In this paper,the coir fibers(CF)was liquefied by microwave-assisted heating.The effects of liquefaction temperature,time,catalyst dosage and coir palm dosage on the liquefaction rate were discussed.The liquefaction under optimal liquefaction conditions was characterized by infiltration gel chromatography and infrared spectroscopy.The coir liquefaction product(CL)was blended with polyvinyl alcohol(PVA)to prepare a composite film with excellent properties.The properties of the composite membrane were tested and characterized by infrared,thermogravimetric and scanning electron microscopy.In order to make full use of coir fiber,a higher value-added product was prepared,and coir was subjected to alkali boiling and bleaching to extract coir cellulose,and cellulose nanofibrils(CNF)was prepared by TEMPO oxidation modification and sonication.Finally,nanofibrillated cellulose was added to the composite film of copra liquefaction and polyvinyl alcohol to study its effect on the composite.The experiment has the following conclusions:Liquefaction single factor experiments showed that excessive catalyst,higher temperature and longer liquefaction time would cause the liquefaction rate to decrease.The proper amount of glycerol could reduce the activity of liquefaction agent and increase the liquefaction rate,which would lead to liquefaction reaction.The decrease in activity was not conducive to the progress of liquefaction.The optimum liquefaction conditions were:liquefaction time was 20 min,catalyst dosage was 3 wt%,Gl mass fraction in liquefaction agent was 20%,temperature was 160?,the liquid to solid ratio is 10:2,and liquefaction rate was 80.8%.The weight average molecular weight of the liquefied product under optimal liquefaction conditions was 7341,and the hydroxyl value was 263 mgKOH/g.In the CL/PVA composite membrane,CL and PVA were mainly connected by hydrogen bonds.The SEM images showed that with the increase in the amount added of CL,the micelle structure appeared in the cross section,which was beneficial to the elongation of the composite film.An increase in the amount of CL added was advantageous for the elongation at break,and excessive CL caused a decrease in tensile strength,and a tensile strength of the composite film of 10 wt%was at most 56.7 MPa.Thermogravimetric and photometric tests showed that the CL/PVA composite film had better thermal stability and opacity than the PVA film,but the water resistance of the composite film was poor.Nano-sized CNF was prepared by cohosh,bleaching,TEMPO oxidation and high-intensity ultrasonication.TEM images showed that CNF fibers had good dispersibility and high aspect ratio.The average diameter of CNF was 5.6 nm and the average length is 252.8 nm.The CNF/CL/PVA composite membrane was prepared by adding CNF to a mixture of CL and PVA.The composite film exhibited superior mechanical properties and water resistance than the CL/PVA composite film.The tensile strength of 3CNF/CL/PVA composite film was up to 65.9 MPa,and the increase of CNF content was not conducive to the increase of elongation at break.Infrared spectroscopy indicated that CNF was mainly linked to CL and PVA in the composite membrane by hydrogen bonding.