The Study Of Poly (Lactic Acid) Reinforced With Cellulose

In this paper,three kinds of Nanofibrillated Cellulose(NFC),Nanocrystalline Cellulose(NCC)and a-cellulose were modified by acetylated method,and marked as mNFC、mNCC and ma-Cellulose,respectively.The resulted celluloses were added into poly(lactic acid)(PLA)as reinforcement to prepare biodegradable composites of mNFC/PLA,mNCC/PLA,and ma-cellulose/PLA by solution blending method.Then,microcellular foaming materials were prepared to be initially explored by supercritical carbon dioxide technology.The acetylated modification is low cost,and can obtain cellulose with high degree of acetylated substitution easily.FTIR and Contact Angle test showed that a part of hydroxyls were replaced by acetyl successfully.The surface property of the modified celluloses were changed to hydrophilic,and thus improved the interfacial compatibility with poly(lactic acid)(PLA)to prepare the well dispersed polylactic acid composites.The degree of acetylated substitution was calculated by the results of ~1H NMR spectrum,mNFC was 1.32,mNCC was 1.62 and ma-cellulose was 1.98.TEM and XRD exhibited that their crystallinity were reduced but their crystalline nature was still preserved,and the modification mainly occurred on the surface of cellulose.TG showed that there was a slight decrease on their thermostability.Methylene chloride is easy to be removed as the solvent in the process of preparing mNFC/PLA,mNCC/PLA and ma-cellulose/PLA composites by solution blending method.The mechanical properties of the composites were tested with stress-strain standard methods.The results implied that the addition of three kinds of cellulose in the PLA matrices induced a significant enhancement on the mechanical properties.The tensile strength was improved,meanwhile the elongation at break was opposite compared with pure PLA.The effects of mNFC,mNCC and ma-cellulose on the thermal properties of poly(1-lactide)matrices were also investigated.TG tests revealed that the thermal decomposition temperature and the temperature of the maximum degradation rate exhibited varying degrees of decline,however DSC showed Glass transition temperature Tg and Melting temperature Tm were much higher than pure PLA,Ultraviolet spectrum analyses showed that with the mNFC content increasing,light transmittance and transparency were reduced.The supercritical foaming technology of celluloses/PLA composites was tried studying.When the foaming temperature was increased to near the melting temperature of composites and the preservation time was extended to about 20h,it significantly promoted CO2 to be dissolved in the composites to become a saturation state with pressure relief technology.SEM showed the cellular structures in resin matrix by the supercritical CO2.In the meantime,the high temperature control technologywe was initially studied.However,the optimum technological conditions of obtaining uniform cell morphology and larger expansion rate of foaming still need to be further studied.