Research On APA6 Polymerization System And The T-RTM Process Composites

Anionic polymer nylon 6(APA6)obtained by anionic ring-opening polymerization of caprolactam(CPL)has better performance than nylon 6 obtained by industrial hydrolysis and polycondensation and has been widely studied.However,due to the harsh polymerization conditions of APA6,the preparation process of composite materials is not perfect and limited its development.In this paper,using sodium methoxide as initiator and toluene diisocyanate(TDI)as activator,APA6 castings were prepared by "two-component method".Based on the research,the thermoplastic resin transfer molding(T-RTM)process was used to conduct the preparation and performance research of related composite materials.The polymerization process and polymerization results were studied when the molar ratios of sodium methoxide and TDI were 1:1,1:2,1:3,2:1,3:1 and 4:1,respectively.The results showed that with the increase of the molar ratio of sodium methoxide,the polymerization rate was accelerated,and the time to reach the exothermic peak decreased from 300 s to 172 s;the time for the viscosity to reach 2500 m Pa·s decreases from 1119 s to 418 s;the tensile strength of the castings are all greater than 83 MPa,the bending strength is greater than 100 MPa,and the fluctuation range of the impact strength is small;the monomer conversion rate is all higher than 96%,the polymer crystallinity is all greater than 42%,and the thermal deformation temperature(HDT)has declined.As the increase of TDI mole ratio,the polymerization rate of polymerization system greatly slowed,which meet the time needed for polymerization exothermic peak and the time needed for change the viscosity increase;mechanical properties,monomer conversion,polymer crystallinity and HDT dropped significantly.The results show that when the molar ratio of sodium methoxide to TDI is 2:1,the best ap6 is prepared.Based on the molar ratio of sodium methoxide-TDI of 2:1,the usage amount of sodium methoxide-TDI was studied.The experimental results of temperature and viscosity change of polymerization system show that the reaction rate increases with the increase of initiator and activator dosage,and the time for the reaction system temperature to reach the peak temperature becomes longer and longer.Polymerization temperature reduced from 168 s to 64 s.The time for the viscosity of the reaction system to reach 2500 m Pa·s decreased from 659 s to 323 s.In addition,the monomer conversion rates of the polymers were all greater than 97%;the crystallinity was all about 43%;the highest HDT was 181.73 °C,and the lowest was 155.2 °C.The mechanical properties are less affected,the tensile strength is 85-90 MPa,and the bending strength is above 100 MPa.The effect of polymerization temperature on APA6 polymerization was studied based on64S32 T polymerization system.The results show that the polymerization rate of the system increases with the increase of polymerization temperature,the time from the polymerization system temperature to the peak temperature of the polymerization exotherm is reduced from224 s to 44 s,and the time for the system viscosity to reach 2500 m Pa·s is shortened from 490 s to 218 s;The conversion rates of polymer monomers are all greater than 95%;the crystallinity is continuously decreasing;the maximum HDT is 181.73?,and the minimum is 90.96?;the mechanical properties of the polymer casting body are the best when the polymerization temperature is 160?.After synthesizing various properties,it is considered that 160? is the best casting temperature.Using the polymerization system of 64S32 T,glass fiber reinforced APA6 composites were prepared by T-RTM process at mold temperatures of 140 °C,150 °C,160 °C,170 °C and 180 °C,respectively.Material properties are tested.The relevant test results show that the monomer conversion rate of the resin matrix is the highest at 96.56% when the mold temperature is 170 °C;50.31 MPa;the mass fiber content and volume fiber content of the composite are about 72%and 54%,respectively;the monomer conversion of resin matrix and porosity of composite decrease with the increase of mold temperature.