Preparation And Property Of Halogen-free Flame Retardant Cable Materials

Polyolefin is made of pure hydrocarbon elements, which has the property of qualitative light, non-toxic, chemical resistance, electric insulation, easy processing and forming, etc. It has been widely used as a halogen-free cable material. Ethylene-octene copolymer(POE) has the common features of polyolefin, and its flexibility, excellent heat resistance and aging resistance is good. So it is more suitable for the coating material of the cable. However, POE is easy burning, the limit oxygen index is about 17% and burning flame, and the obvious molten drops. As cable material, the flame retardant property must be improved. In this paper, a series of halogen-free flame retardant cable material are made by adding halogen- free flame retardant agent to the POE, and study the synergism between the different flame retardant agents.The research content and the main results are as follows:(1) Prepared the flame retardant POE composites with intumescent flame retardant(IFR), consist of ammonium polyphosphate(APP) and pentaerythritol(PER). The mechanical properties, limit oxygen index(LOI) and UL94 test were studied. And thermo gravimetric(TG), cone calorimeter test(CCT) were used in this work. When the IFR is 60 phr, APP/PER is 2/1, the LOI is 28.0%, and attain UL94 V-0 standard. The tensile strength is 18.04 Mpa, the elongation at break is 592%. The flame retardants lowered the thermal stability of materials, and PER has the main effect. When APP/PER is 2/1, the total heat release(THR) is 127.9MJ/m2, the composites show the best flame retardant effect.(2) Studied the synergism of ZB and IFR in the POE composites. The flame retardancy, mechanical properties and thermal stability of different ratio and contents PO E composites have been studied by mechanical properties test, LOI, UL-94 test,TG and CCT. The SEM is used for investigate the char layer. Results show that, when ZB content is 10 phr, the tensile strength is 15.99 Mpa, the elongation at break is 593%, LOI is 28.5%, and meets the V-0 rating in the UL-94 test. The CCT results show that THR is 128.20 MJ/m2. And the remanent mass is improved when ZB is added to the system. ZB can restrain the production of smoke. The SEM shows that a prefect char layer is formed, which has the effect of isolation and absorption.(3) Studied the synergism of AHP and IFR in the PO E composites. The flame retardancy and mechanical properties of POE composites with different AHP ratio and contents are investigated. And CCT, TG and SEM analysis methods were used to determine the best ratio between AHP and IFR. The results show that the POE composites have the optimum comprehensive performance with 10~15phr AHP added, LOI is 30.8%, UL94 test is V-0. AHP can promote dehydration and the remanent mass. When AHP content is 10 phr, the peak of heat release rate(p-HRR) is 206.22 k W/m2, the THR is 109.20MJ/m2, the total smoke production(TSP) is 17.27m2, the production of smoke is restrained. The SEM shows that when 10 phr AHP are added to the system, a prefect char layer can be formed.(4) The effect of wollastonite(Wo) in the intumescent flame retardant system and synergistic flame retardant system were studied. And the synergism and padding of Wo with the IFR system were discussed. At the same time, the flame retardancy and mechanical properties of POE composites with Wo surface modified or not were stud ied. The results show that there is a bad synergism effect between Wo and IFR in POE composites. The mechanical properties can be improved by adding surface modified Wo. When filled with 10 phr surface modified Wo, the mechanical properties of ZB cooperated POE composites can be improved, and the LOI is 27.9%, but the UL94 test is classless. In the AHP cooperated system, the filling amount of Wo can be 30 phr, and the mechanical properties improved a lot, but the LOI decreases slightly and cannot meet UL 94 V-0 test.