Synthesis And Application Of Low Molecular Weight Glycidyl Methacrylate Chain Extenders

Glycidyl methacrylate(GMA)contains carbon-carbon double bonds which can undergo free radical polymerization and epoxy groups which can react with hydroxyl,carboxyl,and amino groups.GMA is expensive,but it can copolymerize with styrene(St),methyl methacrylate(MMA)and these copolymerized polymers are widely used as additives for polymer material modification.In particular,GMA copolymer can react with the end group of macromolecular chain of engineering plastic polyamide 6(PA6)to form a"bridging"to connect the macromolecular chain,thus improving the molecular weight and viscosity of PA6.The chain extension effect of GMA copolymer increases as its molecular weight decreases.Therefore,the synthesis of low molecular weight GMA copolymers is of great significance.In this paper,the solution polymerization method was used to copolymerize GMA with St and MMA,respectively,to prepare GMA-St binary copolymer(PGS)and GMA-MMA binary copolymer(PGM).The reaction conditions of the GMA/St and GMA/MMA copolymer system were optimized.The more suitable reaction conditions were:the reaction temperature was 75?,the reaction time was 10 h,and the addition amount of the chain transfer agent n-dodecanethiol(NDM)was 4.0 wt%of the total monomer mass,and the addition amount of the initiator azobisisobutyronitrile(AIBN)was 5.0 wt%of the total monomer mass.Under these conditions,the(?)_w of the binary copolymer PGS obtained was5.3×10³,and the yield was 89.0%.The(?)_w of the obtained binary copolymer PGM was6.9×10³,and the yield was 92.9%.On this basis,?-methylstyrene(AMS)was used as the third monomer to replace part of St or MMA to obtain GMA-St-MMA terpolymer(PGSM)and GMA-MMA-AMS terpolymer(PGMM).When the mole fraction of AMS in the total monomer was 3.0 mol%,the(?)_w of the obtained terpolymer PGSM-3 was 4.8×10³,and the yield was 70.5%.The(?)_w of the obtained terpolymer PGMM-3 was 4.7×10³,the yield was90.9%.The composition of PGMM-3 was determined by ¹H-NMR.The results showed that the molar ratio of each structural unit in PMGA-3 was equivalent to the feed ratio.A torque rheometer was used to study the influence of the molecular weights of PGS and PGM on their chain extension effects and the difference in their chain extension effects.The results showed that the chain extension effects of PGS and PGM on PA6 increased with the decrease of its molecular weight;PGM with the same epoxy equivalent and weight average molecular weight could extend PA6 more effectively than PGS.In addition,the influence of AMS structural unit on the chain extension effect of PGMM-3 was studied.The results showed that T_5%(the 5%weight loss temperature)of PGMM-3 decreased to 187.4?,while the T_5%of the copolymer without AMS was 282.3?.PGMM-3 could depolymerize during processing,which further reduced the molecular weight and improved the chain extension effect.PGSM-3 and PGMM-3 were used to modify PA6 by melt blending and extrusion,and their effects on the processability,crystallinity and mechanical properties of PA6 were investigated.The results showed that the melt viscosity,glass transition temperature,tensile strength and notched impact strength of PA6 increased with the increase of PGMM-3 content,while the crystallization temperature,crystallinity and crystallization rate of PA6 decreased with the increase of PGMM-3 content.When the content of PGMM-3 was 1.0 wt%,the chain extension reaction of PA6 occurred,but not excessive crosslinking.The melt mass flow rate of PA6 decreased from 21.9 g/10 min to 8.2 g/10 min,the complex viscosity when the angular frequency was 1.0 rad/s increased from 491 Pa·s to 1381 Pa·s,glass transition temperature increased from 71.6?to 79.9?,tensile strength increased from 74.3 MPa to 79.2 MPa,and notched impact strength increased from 6.8 k J/m² to 7.5 k J/m².And the crystallization temperature decreased from 189.7?to 185.5?,the crystallinity decreased from 26.6%to24.6%,the crystallization rate at 195?decreased from 2.45 min^-1 to 1.31 min^-1.The addition of PGSM-3 had the same effect on PA6,but the effect was not as good as PGMM-3.In addition,comparing the chain extension effects of PGSM-3 and PGMM-3 with the commercially available chain extender ADR 4370F,it was found that PGSM-3 and PGMM-3could effectively improve the melt viscosity of PA6 than ADR 4370F.