Preparation And Performance Of The Nanocellulose/Water-Borne Acrylic Resin Composites

The aim of this study was to improve the property of biaxially oriented polypropylene(BOPP),and to enlarge the nanocellulose application in packaging film.The new development was designed by using ball milling pretreatment,enzymatic hydrolysis,neutral sulfite cooking,and cellulose upgradation to generate four target products(sugars,lignosulfonates,cellulose,and cellulose nanocrystals).The chemical components,particle size of solid residues,and crystallinity in each process were monitored.The comparation between cellulose nanocrystals isolated from the new progressive refining and isolated from the commercial microcrystalline cellulose were investigated.The cellulose I with three different particle size were selected,and TEMPO-mediated oxidized to enhance the dispersing stability of cellulose in acrylic resin.The mixed cellulose nanoparticle/acrylic resin composites and laminated cellulose nanoparticle/acrylic resin composites were prepared and coated on BOPP.This dissertation explored the film formation mechanism of cellulose nanoparticle suspensions and their shear-thinning behavior,estimating the particle size of cellulose nanoparticles by using the relationship between aspect ratio of cellulose nanoparticles and the static viscosity of cellulose nanoparticle suspensions,evaluating the dimensional feature influencing on the physical,mechanical,light,oxygen barrier property of cellulose nanoparticle suspensions and their acrylic resin composites.The main conclusions are summerized as follows:(1)Ball-milled wood with 80 min and 120 min(BMW80 and BMW120)has the length of 74 ?m and 23 ?m,respectively.The carbohydrate yield and cellulose-to-glucose conversion of BMW120 reached to 67.7%and 76.1%,respectively,three times as high as those of BMW80,both ball-milled wood had the carbohydrates and sugars recovery over 90%.After neutral sulfate cooking,57.72 g/L and 88.16 g/L lignosulfonate were harvested from the BMW80 and BMW120,respectively.The cellulose recovery were 36.4%and 10.2%,respectively.In the process,the solid residues exhibited a size reduction to nano-scale,an increasing aspect ratio and crystallinity.The resultant cellulose nanocrytals had a comparative property to the cellulose nanocrystals isolated from the commercial microcrystalline cellulose,with relative low crystallinity while more stable thermal property.They were able to be a new cellulose nanoparticle resource.(2)TEMPO-mediated oxidation transfered the hydroxyl groups into the carboxyl groups on cellulose with carboxylate content over 1.99 mmol/g cellulose.TEMPO-mediated oxidized cellulose nanoparticles(T-CNPs)presented decreased particle size,crystallinity,and thermal stability,while their aspect ratio,z-potential increased.The oxidation led to T-CNP suspensions becoming transparent and dispersing uniformly.T-CNP of small aspect ratio presented a bundle-like shape along with the ice crystal growing direction when freeze-drying,the increasing cellulose concentration resulted in the bundled cellulose being linked as a layered dense film.However,T-CNP with large aspect ratio exhibited network structure when freeze-drying,concentrated cellulose led to the pore being filled as a continuous porous film.As a result,it was deduced that cellulose nanoparticle suspensions was able to form network and parallel structural films with gradually natural evaporation.The viscosity of T-CNP suspension increased with the increasing concentration and aspect ratio,while gradually declined with the increased shear rate.The suspension exhibited smooth,three-region,or four-region shear-thinning behavior,owing to the agglomeration and deagglomeration of cellulose with various cellulose.The aspect ratio of cellulose nanofibers were predicted by using the functional relationship between aspect ratio and viscosity.Its length was 7.583 ?m.This approach is of analytical and practical worth for the determination of cellulose nanofiber without the observation and calculation by microscope or optical instrument.(3)The negative charged T-CNP and acrylic resin(AR)mutually repel to form transparent and dispersing uniformly composites,the viscosity of the T-CNP/AR composites gradually increased with the increasing T-CNP concentration and aspect ratio,exhibiting the typical shear-thinning behavior curve.Their storage modulus and loss modulus rose with the accelerating angular frequency.The composites were then coated on the BOPP,the resulting BOPP film still presented high light transparency and excellent anti-fog property.The results showed T-CNP had slight influence on the surface energy of composites,the roughness of film all kept below than 1.89 nm,peeling area decreased from 2B grade to 3B grade with the increasing T-CNP concentration.The oxygen transmittance rate and water vapor transmittance rate had no obvious reduction.The tensile strength decreased after gradually improved when the T-CNP concentration continuously increased.(4)Laminated BOPP-AR-T-CNP composites films were prepared based on the T-CNP core layer,AR adhesion layer,and BOPP base layer.The T-CNP layer finally had the thickness of 1.25?1.92 ?m,the roughness were only 2.81?4.59 nm,their surface energy were higher than both BOPP's and AR's.Laminating structure led to film maintaining high light transparency,tensile strength obviously enhanced,and the larger aspect ratio,the higher tensile strength.The laminated BOPP-AR-T-CNP film presented excellent oxygen transmittance rate,lower to 2.356 cc/(100in2 day),the water vapor transmittance rate increased compared with the BOPP-AR/T-CNP composites films,while the physical structure had no distinguished influence on the water vapor transmittance rate.