| Cable sheaths are often gnawed by rats,resulting in serious accidents caused by short circuits of wires and cables,so the rat repellents are incorporated to protect cables.In order to prohibit the danger for human health and the environmental pollution of conventional rat repellents with higher toxicity,prospects in developing non-toxic rat repellents were put forward to improve the rat-proof and other properties of polymer and polymer composites applied in cable sheath materials preparation.In this dissertation,a green and non-toxic repellent for rats named DC was synthesized from capsaicin and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide（DOPO）.In order to investigate the effects of DC on the structure and properties of EVA,the DC/ethylene vinyl acetate copolymer（EVA）composites were prepared,and DC was found to have a synergistic effect on flame retardancy as well.In addition,the influence of DC on the performance of EVA-based material for cable sheath（CM）with low smoke halogen-free flame retardant was further studied.In further,DC-LDH was prepared from DC and synthetic hydrotalcite（LDH）,and the effects of DC-LDH on the properties of CM were investigated.The details and key conclusions are described as follows:1.DC has been successfully synthesized from capsaicin and DOPO,then DC was incorporated into ethylene vinyl acetate copolymer（EVA）via melt blending.The influence of DC on the structure and properties of EVA was investigated by theoretical calculations and various measurements.The gnawing tests of EVA for rats show that the dosage of 1 wt%DC has a significant rat-proof effect,while without side-effects on physiological characteristics of rats,so DC is an ideal repellent with advantages of high efficiency but without influence on humans and the environment safety.Thermogravimetric analysis（TGA）test results reveal that the incorporation of 4 wt%DC into EVA can significantly improve the char residues of EVA from 2.80 wt%to 6.84 wt%.In addition,limiting oxygen index（LOI）and the char residues analysis of EVA suggest that DC could facilitate the formation of char layers,resulting in the improvement of flame retardancy of DC/EVA.2.The influence of DC on properties of rat-proof,flame retardancy,thermal stability and aging resistance of CM was also investigated by introducing DC to CM via melting blending.The mechanical properties show that DC has a plasticizing function on CM,and the gnawing test for rats shows that the dosage of 2 wt%DC in DC/CM composites could provide significant and sustained effects on rat-proof.In addition,LOI values of DC/CM composites are all greater than 29.0%,which illustrates that DC has a good synergistic effect on flame retardant which is inconsistent with the char residue analysis that DC inhibits the thermal decomposition of CM by promoting the formation of char layers.3.In further,a compound named DC-LDH was successfully prepared by loading DC onto LDH,and DC-LDH was blended with polymer composites for cable sheath with low smoke halogen-free flame retardant to prepare DC-LDH/CM composites.The influence of DC-LDH on the properties of CM was investigated.It was found that DC-LDH could be dispersed well in the substrates of polymers,and significantly improve the mechanical properties of the polymer composites for cable sheath.The tensile strength of polymer composites applied as cable sheath materials increase to about 11 MPa while the elongation at break increased to 391%.On the other hand,the loading of DC on the LDH inhibits the migration of it in the polymer composites,which should endow DC-LDH/CM with continuous and efficient rat-proof performance for cable sheath.LOI values of DC-LDH/CM were more than 31.0%.Meanwhile,the DC-LDH/CM performance is improved in thermal stability,aging resistance,electrical insulation et al.,especially the volume resistivity（ρv）of DC-LDH/CM could also be remained at 3.71×1013Ω·m after aging 168h at 100°C in air condition. |
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