Study On Preparation And Properties Of Functionalized Halloysite Nanotubes And Chitosan Composites

Chitosan is biodegradable as a kind of natural polymer material,has a wide application prospect in many fields,such as medicine,food,chemical industry,because of its good biocompatibility and antibacterial properties.However,due to its poor mechanical strength,limited water resistance,and lack of stability in acid medium,it is easy to form flocculation in aqueous solution and other shortcomings,which limits the application of chitosan.Therefore,in order to improve the properties of chitosan,it is necessary to improve its properties by the way of crosslinkin g or compounding with other materials.Halloysite nanotubes(HNTs)are natural nano particles with high modulus and large aspect ratio,which have the advantages of high availability,rich functions,good biological adaptability and high mechanical strengt h.However,HNTs will be affected by size effect,surface electronic effect and hydrogen bond formed by surface hydroxyl,which makes it difficult for HNTs to obtain good dispersion in the polymer matrix in practical applications,and it is easy to cause agglomeration,thus affecting the application effect of HNTs.To solve the dispersibility of HNTs and its compatibility with organic matrix,two different modification methods were used to prepare functionalized halloysite nanotubes in the article,and composited with chitosan to prepare functionalized halloysite nanotube/chitosan composite materials,and their properties were discussed and studied.The main research contents are as follows:Firstly,3-aminopropyltriethoxysilane(APTS)was selected as modifi er to obtain aminoated halloysite nanotubes(HNTs-NH₂).On this basis,add succinic anhydride to obtain carboxylated halloysite Stone nanotubes(HNTs-COOH).The results of FTIR and XPS showed that the functionalization of amino group and carboxyl group was successful;The results of TGA indicated that the original halloysite nanotubes(RHNTs)themselves have higher heat resistance,while the weight loss rate increased after functionalization,and the mass loss of HNTs-COOH was greater than that of HNTs-NH₂;Dynamic light scattering(DLS)results showed that after functional modification,the average particle size of halloysite nanotubes increased from 343.72nm of RHNTs to 452.37 nm of HNTs-NH₂ and 717.33 nm of HNTs-COOH;TEM images show that RHNTs have tubular structure,the surface is smooth,uniform and easy to aggregate,the outer surfaces of HNTs-NH₂ and HNTs-COOH become rough,but the dispersion is improved.Using HNTs-NH₂ as the nanofiller reinforcement phase,the nanocomposites were prepared by solution intercalation with chitosan,and ethylene glycol diglycidyl ether(EGDE)was added to the formulation as a crosslinking agent.FTIR showed that EGDE had chemical reaction with HNTs-NH₂ and chitosan,which made the composite membrane form a cross-linked network structure.The XRD curves showed that HNTs-NH₂ could be mixed with chitosan uniformly,and after EGDE was added,the reaction between HNTs-NH₂ and chitosan resulted in the loss of crystallinity of the composite membrane after egde was added.SEM imag es observed that the surface of the pure chitosan membrane was smooth and dense,and the surface of the composite membrane formed a small microporous structure after adding HNTs-NH₂,while the addition of EGDE made the surface of the material form a large number of pores.The addition of HNTs-NH₂ and EGDE can improve the water vapor transmission rate and swelling of the composite membrane,improve the physical properties of the composite material,and make the composite membrane exhibit stronger thermal stability and higher mechanical properties.HNTs-COOH was selected as the nano-filler reinforcing phase,the different proportions of HNTs-COOH and condensing agent were added to the chitosan polymer matrix to reinforce and plasticize the prepared composite m aterial.The results show that:HNTs-COOH can be well dispersed in the chitosan matrix,and the thermal stability and mechanical properties of the composite material have been improved.The addition of HNTs-COOH and the condensing agent can change the fracture mode and swelling property of the composite membrane materials,improve the water vapor permeability,and have better moisture absorption and moisture retention properties.