Study On Strengthening And Toughening Modification Of Nylon 6 Filaments And Its Structure And Properties

With the progress of polymerization and spinning technology,the production capacity of nylon6 filaments increased year by year,and its application field continued to expand.However,limited by production equipment,technical barriers and other factors,the foreign dependence of high performance nylon 6 filaments is still high and the import volume is large,how to obtain both high strength and high toughness nylon 6 filaments under the existing conditions and then expand its application range has been the attention of the majority of researchers.Since the amide group(-NHCO-)in the nylon 6 molecule is a polar group,it is easy to form crystals by hydrogen bond between molecular chains,resulting in excessive intermolecular entanglement,which limits the enhancement of strength.From two perspectives of spinning process and material modification,the influence of drawing process and plasticizer modification on the structural and properties of nylon6 were studied in this paper,with the related mechanisms were analyzed,then prepared nylon 6filaments with high strength and toughness.The main research contents are as follows.High strength nylon 6 filaments were prepared by melt spinning and two-stage drawing.The influence of draft multiple on the structure and properties of nylon 6 was studied by differential scanning calorimetryer(DSC),X-ray diffractometer(XRD),sonic velocity orientation tester,thermogravimetric analyzer(TGA),tensile properties test and moisture regain test.The results showed that the crystal structure of nylon 6 changed from?crystal to?crystal with the increase of draw ratio,the molecular arrangement was more regular,and the thermal stability,crystallinity,orientation degree,and mechanical properties of the filaments were enhanced with the increase of draw ratio.When the two stap draw ratio of was 3.0 and the draw temperature was 210°C,the overall performance of the filaments was optimal.The breaking tenacity was 8.22 cN/dtex,the breaking elongation was 22.4%and the initial modulus was 59.2 cN/dtex,reached the standard of high strength nylon 6 filaments.Using D-sorbitol as a plasticizer,modified nylon 6 resin was obtained by melt blending D-sorbitol with nylon 6.By means of DSC,XRD,dynamic thermomechanical analysis(DMA),TGA and tensile properties test,the effects of D-sorbitol addition on the crystallization ability,crystal form change,dynamic mechanics,thermal stability and tensile properties of nylon 6 resin were studied.The effect of D-sorbitol on the crystallization performance of nylon 6 resin was studied by isothermal crystallization kinetics analysis of nonisothermal crystallization kinetics.The results showed that the addition of D-sorbitol can promote the heterogeneous nucleation of nylon 6 resin,reduce the glass transition temperature(T_g),melting temperature(T_m)and crystallinity(X_c)of it.This was because the introduction of D-sorbitol weakened the hydrogen bonding between the nylon6 molecular chains and improved the mobility of the molecular chains,thereby achieving the plasticizing and toughening effect on the nylon 6 molecular chains.Nylon 6 filaments with different D-sorbitol content was prepared by melt spinning and one-step drafting.The draw ratio of the spinning process was adjusted,and the effect of D-sorbitol addition on the structural properties of nylon 6 filaments under different draw ratios was studied.The results showed that the addition of D-sorbitol improved the drgree of crystallinity,the orientation degree,breaking tenacity and breaking elongation of nylon 6 filaments,and reduced the initial modulus of the filaments,which had a good strengthing and toughening effect on nylon 6filaments.Under the optimal process conditions,the breaking tenacity of nylon 6 filaments was5.29 cN/dtex,breaking elongation was 49.5%,and the initial modulus was 34.0 cN/dtex.After washing,the tensile properties of nylon 6 filaments changed wihin a narrow range the properties were excellent.