Controllable Preparation Of Nylon6/Silicone Rubber Thermoplastic Dynamic Vulcanizate

Nylon 6(PA6)is an engineering plastic with high strength,excellent processing performance and temperature resistance.Silicone rubber(PDMS)exhibits excellent high temperature resistance and chemical solvent resistance.Therefore,it is expected that a thermoplastic elastomer with excellent properties can be prepared by compounding PA6 and PDMS.However,the compatibility of PA6 and PDMS is poor and the vulcanization rate is difficult to control.Therefore,it is a big challenge to improve the compatibility of PA6 and PDMS and control the dynamic vulcanization process for the preparation of PDMS/PA6 thermoplastic rubber.Firstly,the dissipative particle dynamics(DPD)simulation was used to study the influence of the molecular structure of block copolymer on the compatibility efficiency of PDMS/PA6 blends,and then reactive block copolymers with high compatibility were designed and synthesized.The synergistic effect of organic nano-montmorillonite(OMMT)and reactive block copolymer on the dispersion and continuous range of PDMS/PA6 blend were further investigated.Finally,the preparation process and properties of PDMS/PA6 thermoplastic elastomers were investigated.This thesis obtained the following results:(1)Comparing the compatibility of different structural block copolymers on PDMS/PA6 blend by DPD simulation,it was found that a polymer segment with the solubility parameter between PDMS and PA6 embedded in the block copolymers could stabilize at the interface,which could significantly reduce the interfacial tension,the size of the dispersed phase,and the time required for the blend to reach equilibrium.(2)Based on the DPD simulation results,reactive block copolymers characterized by embedding polyether segments in the amino-terminated silicone oil were designed and synthesized.The terminal amino group of the copolymer can react with nylon 6 to form a triblock copolymer as the compatibilizer of PDMS/PA6 blend.Compared with the conventional amino-terminated silicone oil,the reactive block copolymer can reach the phase interface more quickly,and promote the dispersion of the dispersed phase,which exhibits higher compatibility efficiency.(3)For the PDMS/PA6(20/80)blend system,the introduction of reactive block copolymer and OMMT together showed a synergistic effect to promote the dispersion of the blend and shorten the time required for the dispersed phase to reach equilibrium.This is because OMMT is mainly dispersed in PA6.On the one hand,it can increase the viscosity of PA6 and reduce the viscosity ratio of dispersed phase(PDMS)to matrix phase(PA6).On the other hand,it can prevent the aggregation of PDMS.In addition,the combined usage of OMMT and reactive block copolymers could also improve the tensile strength of PDMS/PA6(20/80)from 42.8 MPa to 52.9 MPa,and reduce the water absorption from 2.6%to 1.5%.(4)Unlike traditional compatiblizers reducing the co-continuous range,the addition of 5%reactive block copolymer coculd widen the co-continuous range of PDMS/PA6 blend from 45/55?60/40 to 45/55?70/30.This is mainly because the polyether segments in the reactive block copolymer are capable of increasing the thickness of the two-phase interface layer,and promoting the formation of co-continuous structure.Further addition of OMMT can reduce the size of co-continuous phase.(5)In the preparation of PDMS/PA6 thermoplastic elastomer in a twin-screw extruder,the addition of reactive block copolymer and the prolongation of the mixing time before vulcanization can reduce the continuous phase size of PDMS/PA6,and obtain PDMS/PA6 thermoplastic elastomer with smaller and more uniform.The introduction of a hydrosilyl functional group into the molecular chain of the reactive compatibilizer can produce a vulcanization compatibilizer,which not only acts as a compatibilizer,but also enhances the cross-linking degree of the silicone rubber at the interface of the blend phase.As a result,the tensile strength was improved from 21 to 24.7 MPa,and the elongation at break was increased from 23%to 89%,and the swelling rate in high temperature oil was dropped from 44.5%to 17%.Further addition of OMMT can broaden the continuous range of PDMS/PA6 to get a thermoplastic dynamic vulcanizate with 70%content of PDMS.