Study On Preparation Of Polyamide - Imide By Diisocyanate Method

Polyamide-imide (PAI) is a high performance engineeirng mateiral withheat-resistant aromatic heterocyclic imide groups and flexible amide groups in themolecular structure. PAI has the excellent heat resistance, dielectric properties,mechanical properties and chemical stability, and is widely used in some high-techifeld such as aviation, aerospace and microelectronics.In this paper, PAIs were synthesized rfom tirmellitic anhydirde (TMA) anddiphenyl methene-454’diisocyanate (MDI). The influence of mixing procedure, solventsitfing, solvent water removal, post-processing of product, the structure of the product,reaction temperature, reaction time,monomer feed ratio and monomer concentrationwere investigated by intrinsic viscosity machine, DSC, TGA and Karl Fischer anddis’cussed. The products inherent viscosity is26.8mL/g, glass transition temperatureis305.23。C，thermal decomposition temperature is490。.61C in N2atmosphere whichhigher than the data from literature reported and reached the domestic leading level.This paper further explores the polymerization technology about PPDI or TDI as thethird monomer of modified PAI, preliminary feeding proportion was optimized, thecharacteirstics of the product viscosity reached29.8mL/g and58.5arL/g, The mainresearch contents are as follows:1.PAIs were synthesized from TMA and MDI of NMP or DMF or DMAc withone-heating method. The inlfuence of mixing procedure, solvent sitfing, solvent waterremoval and post-processing of product were investigated by intirnsic viscositymachine, DSC, TGA and Karl Fischer and discussed. It showed that PAI had thebetter performance when using the first cast MDI approach, NMP as solvent, vacuumdistillation to remove water and extraction method.2.PAIswere synthesized rfom TMA and MDI of NMP with one-step heatingmethod. The influence of the structure of the product, reaction temperature，reactiontime,monomer feed ratio and monomer concentration were investigated by FTIR,intrinsic viscosity machine, DSC and TGA. It showed that PAI had the betterperformance when synthesized at140°C with feed ratio iimdi: iitma=1.05:1andmonomer concentration of20%for4h. The product’s inherent viscosity is20.8mL/g，glass transition temperature is260.31。C，thermal decomposition temperature is448°.12Cin N2atmosphere.3.PAIswere synthesized from TMA and MDI of NMP with two-steps heatingmethod. The influence of the structure of the product, reaction temperature, reaction time,monomer feed ratio and monomer concentration were investigated by FTIR,intirnsic viscosity machine, DSC and TGA. It showed that PAIhad the betterperformance when synthesized at40。C for2h and130。C for4h with feed ratio hmdi:niMA=1.05:l and monomer concentration of20%. Th’e products inherent viscosity is26.8mL/g, glass transition temperature is305.23。C，thermal decompositiontemperature is490.61。C in N2atmosphere which higher than the data from literaturereported and reached the domestic leading level and the product has excellentchemical-resistance.4.PAIs were synthesized from TMA and MDI or PPDI or TDI of NMP withtwo-steps heating method. The influence of the structure of the product anddiisocyanatefeed ratio were investigated by]H-NMR, intrinsic viscosity machine,DSC and TGA. It showed that (1) T-PAI had the better performance when synthesizedwith diisocyanatefeed ratio iimdi: htdi=7:3. The product’s inherent viscosity is29.8mL/g，glass transition temperature is280.76°C，thermal decompositiontemperature is480。.16C in N2atmosphere.(2) P-PAI had the better performancewhen synthesized with diisocyanate feed ratio iimdi: nppD产7:3. The product’s inherentviscosity is58.5mL/g, glass transition temperature is308.32。C，thermaldecomposition temperature is517.80。C in N2atmosphere. Both kinds of the producthave excellent chemical-resistance.