The Preparation Of Ionic Liquid Grafted Polyamide 6 And The Investigations On Its Structure,Properties And Applications

Polyamide 6(PA6)is an important polymer material with good mild acid/alkali resistance,solvent resistance,mechanical properties and processability.Thus PA6 is widely used as fiber,porous membrane,engineering plastic and so on.With the development of technology,higher requirements are proposed for PA6 materials in practice.Physical blending and chemical grafting are two critical strategies to obtain high performance PA6 materials.Specifically,the chemical grafting method immobilize the functional component on PA6 chains via covalent bonds and modify the chain structure,leading to permanent functionalization.The radiation induced graft polymerization(RIGP)method is an important way to realize the chemical grafting.It exhibits several advantages,such as high grafting efficiency,wide application range and mild reaction condition.On the other hand,the ionic liquid(IL)is extensively used in polymer modifications due to its antibacterial property,ion conductivity,hydrophilicity or hydrophobicity and so on.In this work,imidazolium IL with different structure of anion: 1-vinyl-3-butyl imidazolium chloride IL(Cl)and 1-vinyl-3-butyl imidazolium bis(trifluoromethylsulfonyl)imide IL(TFSI)were employed to modify PA6.The compatibility between PA6 and IL was investigated systematically.The IL(Cl)was further grafted onto PA6 chains(PA6-g-IL(Cl))via RIGP method.In addition,the applications of PA6-g-IL(Cl)were explored as porous membrane and fiber material and the compatibilizer for poly(vinylidene fluoride)(PVDF)/PA6 blends.The detailed research in this dissertation were listed as follows:(1)Study on the structure and properties of PA6/IL blends.The blends of PA6 and IL with different anions were prepared by melt processing.The SEM and DSC results indicated that PA6 has good compatibility with both IL(Cl)and IL(TFSI).The FTIR spectra confirmed that the anions and cations of the IL interacted with N-H and C=O in amide groups of PA6 respectively,which exerted great influence on the thermal and rheological properties of PA6/IL blends.The IL with different anion structure had varied effects on the properties of PA6 matrix.Specifically,the PA6/IL(Cl)blends exhibited noteworthy improvements in mechanical property,antistatic property and hydrophilicity.(2)The preparation of IL(Cl)grafted PA6 and investigations on its properties.The IL(Cl)grafted PA6(PA6-g-IL(Cl))was prepared via RIGP method.To be detailed,the imidazolium cations of IL(Cl)were grafted on PA6 chains located in amorphous region.The grafting site was confirmed to be-CH2-which was immediately adjacent to-NH in amide group according to XPS spectra.The anions of IL(Cl)was mobilizable so that PA6-g-IL(Cl)exhibited antistatic property to some extent.TEM and SEM results showed that the grafted IL(Cl)formed nanoscale ion cluster without triggering further phase separation in PA6 matrix.The thermal and rheological behaviors and mechanical property of PA6-g-IL(Cl)varied greatly from those of PA6.Most importantly,the chemical grafting immobilized the IL(Cl)as well as its functionalities,and realized the design and modification of PA6 chains at the same time.(3)The preparation of PA6-g-IL(Cl)porous membrane and investigations on its properties.The properties of PA6-g-IL(Cl)as porous membrane were studied.Results indicated improved solubility and hydrophilicity of PA6-g-IL(Cl).PA6-g-IL(Cl)porous membranes were obtained by immersion-precipitation phase inversion method.The SEM results showed that the grafting of IL(Cl)had marked influence on the microstructure of porous membrane.The pore size and porosity of porous membrane were characterized by mercury injection measurements.It was found that the pore size gets smaller and the porosity gets higher simultaneously as the increasing of degree of grafting(DG)for PA6-g-IL(Cl)under the same conditions.In addition,the 2%-50 K porous membrane exhibited smaller pore size but higher water flux as well as improved Cr(VI)adsorption compared to those of PA6 porous membrane.(4)The preparation of PA6-g-IL(Cl)fiber and investigations on its properties.Fibers with different morphology were prepared via solution electrospinning and melt spinning methods.SEM observation found that the grafted IL(Cl)affected the morphology of PA6-g-IL(Cl)fiber significantly.With increasing DG,the diameter of fiber increased correspondingly.The fibers,which were obtained by both solution and melt spinning methods,exhibited antistatic properties when the DG of PA6-g-IL(Cl)was high.Besides,the 4%-50 K fiber also performed excellent antibacterial property.This was particularly important for the practical application as fiber.(5)The investigations of PA6-g-IL(Cl)on the compatibilization effect of PVDF/PA6 blends.PA6-g-IL(Cl)was used to compatibilize PVDF/PA6 blends.Results showed that the incorporation of PA6-g-IL(Cl)modified the microstructure and improved the mechanical properties of PVDF/PA6 blends.Specifically,with 5 wt% of E-8%-50 K,the microstructure of PVDF/PA6=60/40 blends turned into bi-continuous structure.Moreover,the compatibilizer of E-8%-50 K also endowed the PVDF/PA6 blends with antistatic property.This work offered new strategy to prepare new compatibilizers as well as high performance PA6 alloys.