Study On Preparation And Properties Of Cellulose Nanofibers/poly(lactic Acid) Composites

Poly(lactic acid) is the novel environment-friendly bio-degradable polymer. However, PLAhas some shortages, for example, the crisp texture and the low softening point. In order to makebetter use of PLA, it must be modified by other materials. In this paper, PLAwere reinforced bycellulose nanofibers and study CNFs/PLA composites performance. Five aspects were includedin this research:1) CNFs were isolated from wood powder and cotton by chemical processingcombined with mechanical treatment.2) Preparation CNFs film with high modulus by CNFs.3)compared the performance of CNFs film by mixing method and immersion method.4) Analyzedthe influence on the CNFs/PLA composites by different mechanical treatment.5) Analyzed theinfluence on the CNFs/PLA composites by different immersion time.Based on the thesis, the following conclusions are drawn:(1) The use of chemical removal of lignin in wood raw material and most of the hemicellulose,and then using mechanical treatment, the system morphology were uniform size, mesh tangle ofwood cellulose nano-fibrils. The use of grinding30min combined with homogeneous has beena nano-fibrils of uniform, high aspect ratio, reaching1200, mesh tangle of biomass cellulosenano-fibrils.(2) Compared with grinding30min combined with ultrasound60min, grinding60min,ultrasonic60min combined with homogeneous, the performance of CNFs film prepared bygrinding30min combined with homogeneous is the best, through the light transmittance,mechanical properties, fracture surface and thermal expansion coefficient analysis. The CNFsfilm of wood powder compared with CNFs film of cotton show better performance.(3)CNFs/PLA composites were prepared by mixing method. After adding a small amount ofCNFs, the mechanical properties, thermal stability, and barrier properties of CNFs/PLAcomposites had been improved in a certain extent. CNFs were dispersed in PLA well and therehave no chemical reaction between PLA and CNFs. CNFs/PLA composites were combined byphysical function and strong hydrogen bonding interaction.(4)CNFs/PLA composites were prepared by immersion method. After compound with CNFs,the mechanical properties and thermal stability of CNFs/PLA composites had been improvedsignificantly. The fracture surface of CNFs/PLA composites showed three layer structures. PLAwere deeply permeated to CNFs film. However, the barrier properties and light transmittance ofCNFs/composites were decreased for the increasing content of CNFs.(5)Compared with CNFs/PLA composites prepared by mixing method, CNFs/PLA compositesprepared by immersion method show a better performance. Due to mixing preparation methods, the content of CNFs in PLA was limited. CNFs were not dispersed well in PLA matrix andReunion phenomenon were occurred if increasing the content of CNFs. However, the content ofCNFs/PLA prepared by immersion method can achieve60%or more, which could improvecomposites performance greatly.(6)CNFs/PLA composites prepared by different mechanical treatment have differentperformance. CNFs/PLA composite prepared by grinding30min combined with homogeneousis the best. The thermal expansion coefficient is the minimum; water absorption is the lowest;light transmittance is the highest.(7) CNFs/PLA composites prepared by different immersion time have different performance.When the immersion time increases, it has a better performance. By the analysis ofexperimental results, it is known that the dipping8hours is the best time. If dipping time tooshort, it will cause CNFs/PLAcomposites having a poor performance. However, if dipping timetoo long, it will cause the waste of PLA.