Preparation and properties of modified cellulose nanocrystal/PBAT composites
To improve the mechanical and barrier properties of poly(butylene adipate-co-terephthalate)(PBAT),silane coupling agent modified cellulose nanocrystals(MCNC)were prepared by the alcohol-water solution method,which was used as a filler for melt blending with PBAT to obtain MCNC/PBAT composites,and the effects of MCNC content on the microstructure and properties of the composites were investigated.It is found that the addition of MCNC can inhibit the molecular chain movement of PBAT and decrease the crystallinity of PBAT,and the crystallinity of PBAT is reduced to 5.8%with the addition of 1 wt%MCNC.On the other hand,MCNC can promote the crystallization of PBAT through heterogeneous nucleation,significantly increasing the crystallization temperature of PBAT.A small amount of MCNC can be uniformly dispersed in the PBAT matrix to increase the thermal stability of the composites,agglomeration of MCNC occurs and the thermal stability of the composites decreases with high content of MCNC.The elongation at break of the composites increases from 446%to 502%and 478%with the addition of 0.5 wt%MCNC and 1 wt%MCNC respectively,but the elongation at break of the MCNC/PBAT composite is lower than that of pure PBAT with further addition of MCNC,this is mainly attributed to the fact that the rigid percolated network structure formed between MCNC with high concentration and PBAT enhances the modulus and reduces the toughness of the composite.Compared with pure PBAT,the O2 transmission and water vapor transmission of the composite film decrease by 31.1%and 37.6%respectively,when the mass fraction of MCNC is 1%.
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