Research On Preparation And Properties Of Multi-networks Polynorbornene Composites

Shape memory polymer(SMP)is a special shape memory material.Its research began in the 1980 s.It has the advantages of excellent comprehensive performance,high practical value,and low cost,and has been rapidly developed.Polynorbornene(PNB),in the form of a white powder,has a molecular weight of up to 3 million.The entangled structure between molecular chains becomes the stationary phase of the material to maintain its original shape.The glass transition from the glassy state to the rubbery state of the molecular chain due to temperature changes is used as a reversible phase,which makes PNB has excellent shape memory properties.In order to further expand the application of PNB and enrich theoretical research,this paper selects PNB as the research matrix.Based on the previous research,it mainly uses rotorless vulcanization analyzer(MDR),Fourier transform infrared spectrometer(FTIR),X-ray Diffraction(XRD)and other instruments explore the influence of different types and degrees of chemical cross-linking networks and conductive networks formed by functional fillers on the shape memory properties of PNB material,and optimize the shape memory performance of PNB through blending methods,and explore the mechanism of shape memory,to broaden its shape memory response mode.Shape memory materials must have good mechanical properties while ensuring excellent shape memory performance to ensure their service life.Ordinary fillers are poorly dispersed inside PNB,so we innovatively add resorcinol prepolymer(HT1005)and formaldehyde donor(HMMM)to PNB,and form a bulk phenolic resin network and PNB through in-situ curing reaction.The internal physical entanglement network jointly builds a dual network structure.The research results show that a small amount of phenolic resin network can improve the mechanical properties of PNB while maintaining the excellent shape memory properties of the composite material.In order to explore the influence of different types of cross-linking networks on the shape memory performance of PNB,by adding different amounts of sulfur and Dicumyl peroxide(DCP),the cross-linking agent constructs two different types of chemical cross-linking networks inside the PNB,and "like interpenetrating networks" are introduced.The study found that the carbon-carbon cross-linked bond produced by DCP cross-linking has a short bond length and a large bond energy,and the adjacent double bonds form an aggregate structure after addition polymerization,which is unfavorable for the mechanical properties of DCP cross-linked PNB composites.The sulfur-containing cross-linked bond has a longer bond length,a smaller bond energy,and a strong ability to bear external forces under large strains.It gives the sulfur-crosslinked PNB composites excellent mechanical properties,and also ensures its entropy elastic recovery in the shape memory test.It has sufficient restoring force,high shape recovery rate,and the material has the better shape memory performance.In order to expand the electro-induced shape memory effect of PNB materials,the composites prepared by using PNB as the matrix material,adding conductive carbon black and carbon fiber all exhibit electrothermal dual-induced shape memory properties.Compared with conductive carbon black,carbon fiber has higher strength and modulus,which makes the composite prepared by it have more excellent mechanical properties.However,the amount of carbon fiber should not be too small,otherwise it will not provide good mechanical support.Carbon fiber has poor dispersion inside PNB.Therefore,the conductive network formed by carbon fiber is not as perfect as the formation of conductive carbon black.A small amount of conductive carbon black can ensure that the composite material has excellent mechanical properties while also having electrically induced shape memory properties.