Preparation And Properties Of Silicone Sealant With Quaternary Ammonium Salt

Silicone sealants have excellent heat resistance,stability,electrical insulation,and weather resistance.They are widely used in transportation,construction,home decoration,and medical fields.However,silicone sealants are susceptible to adhesion and corrosion by microorganisms during use in humid or high-temperature environments,which seriously affects their lifespan.Therefore,the development of antibacterial functional silicone sealant with antibacterial fuction and how to maintain the durability of antibacterial functions have become an important content in the research field of silicone sealants.In this paper,based on polysiloxane as the matrix,octadecyldimethyltrimethoxysilylpropylammoniumchlorideinme(C₁₈-QAS)was selected as an antibacterial agent,and quaternary ammonium salt organosilicon sealant（PDMS/QAS）was prepared by bulk modification.Secondly,using silane-terminated polyether polymers（MS matrix）as the matrix and C₁₈-QAS as antibacterial agents,a quaternary ammonium salt type silane-modified polyether sealant（MS/QAS）was prepared using a bulk modification method.Using the activity of trimethoxy groups in the molecular structure of C₁₈-QAS,C₁₈-QAS is grafted into the cross-linked network structure of silicone sealant in the form of covalent bonds,and it is expected to obtain silicone sealant with antibacterial function.The main research contents of this thesis are as follows:（1）A quaternary ammonium salt silicone sealant（PDMS/QAS）was successfully prepared using polysiloxane as a matrix,C₁₈-QAS as an antibacterial agent,and dehydration condensation between the hydroxyl group in the polysiloxane matrix and the methoxy group in the C₁₈-QAS structure.The effects of C₁₈-QAS content on the cross-linking mechanism,mechanical properties,hydrophilic and hydrophobic properties,and thermal stability of PDMS/QAS were emphatically studied.Then,the effects of the amount of TEOS and low viscosity polysiloxane on the mechanical properties,hydrophobicity,and thermal stability of PDMS/QAS were investigated.The mechanical properties of PDMS/QAS were characterized by tensile testing.The results showed that the comprehensive mechanical properties of PDMS/QAS were the best when the content of C₁₈-QAS was 3%of the matrix.Increasing the content of TEOS can significantly improve its mechanical properties.The increase in the content of low viscosity polysiloxane reduces the mechanical properties of PDMS/QAS.At the same time,SEM was used to characterize the surface morphology of PDMS/QAS,and the results showed that C₁₈-QAS had poor compatibility with the matrix.（2）A series of quaternary ammonium salt silane-modified polyether sealants（MS/QAS）were successfully prepared using MS as the matrix,using the activity of trimethoxy groups in the C₁₈-QAS molecular structure and the condensation crosslinking reaction between C₁₈-QAS and MS.The effects of C₁₈-QAS content on the crosslinking mechanism,mechanical properties,hydrophilic and hydrophobic properties,and thermal stability of MS/QAS were studied.The curing process of MS/QAS was characterized by surface dry time testing,and the results showed that the addition of C₁₈-QAS significantly improved its curing speed.Furthermore,the vulcanization and mechanical properties of MS/QAS were characterized by crosslinking density and tensile testing,respectively.The results showed that the crosslinking density and mechanical properties of MS/QAS were the best when the C₁₈-QAS content was 1.5%of the matrix.Finally,TG analysis showed that the increase in C₁₈-QAS content had little impact on the thermal stability of MS/QAS.