Study On Processing And Properties Of Cellulose Nanocrystalline/Anionic Polymerized Nylon 6 Composites

Anionic polyamide 6(APA6)has more excellent properties than ordinary PA6,such as low polymerization temperature,simple process flow and large molecular weight.However,APA6 products still have some defects,such as poor strength and modulus at high temperature,insufficient toughness at low temperature and poor dimensional stability.For this reason,APA6 has been modified by blending,block and grafting methods at home and abroad to expand its application range,in which nano particle filling is an important way.Cellulose nanocrystals(CNC)have good biocompatibility,renewability,high crystallinity and high strength,so they are widely used in filling,modifying,reinforcing and toughening polymers.However,the surface energy of CNC is high and there is a strong tendency of self aggregation,which can not be achieved only by direct filling.Therefore,in this paper,two methods were used to prepare CNC/PA6 in-situ composites,one is the direct blending polymerization of PA6 monomer(caprolactam)and CNC,the other is the method of initiating grafting PA6 on the surface of CNC.Through this study,the problem of difficult processing of CNC and PA6 was solved,and a new high-performance nanocomposite was obtained,which expanded the application of natural polymer materials in the field of engineering plastics,and realized the ideal dispersion and interface adhesion of nanoparticles in polymer.The main research contents include:1.Using the surface activity of cellulose nanocrystals,modification was carried out.Firstly,the hydroxyl group on the surface of CNC reacted with the para isocyanate of toluene diisocyanate(TDI),and the remaining ortho isocyanate was capped by caprolactam(CL)to prepare CNC grafted with acylated caprolactam(CNC-g-CL).The results are as follows:the degree of substitution of TDI for-OH on CNC(DS_TDI)and the degree of caprolactam terminated isocyanate(DS_CL)were improved with increasing temperature and TDI/CNC(molar ratio)and reducing the amount of solvent,but there was a maximum.A series of CNC-g-CL with DS_CL ranged from 8.34%to 66.72%were prepared under different conditions2.In situ ring opening polymerization of CNC-g-CL and caprolactam was used to prepare mCNC/APA6 composites.CNC-g-CL has little polymerization inhibition effect and good compatibility with APA6,which realizes the enhancement effect of CNC on APA6.The tensile strength and flexural modulus of mCNC1/APA6 were 97.7 MPa and3.9 GPa,respectively,which were 24%and 63%higher than APA6.The storage modulus of mCNC1/APA6 was higher than that of pure APA6 and unmodified CNC/APA6 in the range of 0?200?.At the same time,the glass transition temperature of the composites was 70?,which was 40?higher than that of pure APA6.3.Initiated the anionic ring opening polymerization of caprolactam on the surface of CNC,the cellulose nanocrystalline grafted nylon 6(CNC-g-PA6)composites were prepared.The CNC particles were uniformly dispersed in APA6 matrix,and the average particle size was less than 1?m,at the same time,a large number of monodisperse CNC was observed by TEM,which realized the good dispersion of nano materials.The maximum tensile strength of CNC was 108.1 MPa,which was 37.7%higher than that of pure APA6.Through process control,the impact strength reached 7.9 kJ/m²,which was 46%higher than that of pure APA6.At this time,the tensile strength was 101.1 MPa,which was 29%higher than that of pure APA6.Moreover,the glass transition temperature of CNC-g-PA6 increaseed from 30?to 90? of pure APA6,which significantly improved the heat resistance of the material.