The Effect Of Calcium Alginate Fiber On The Flame Retardancy Of Ethylene-vinyl Acetate

Ethylene-vinyl acetate copolymer(EVA)has been widely used in many areas due to its excellent properties,especially in the fields of wire and cable.However,EVA is easy to burn with a limit oxygen index(LOI)only about 18%.It may produce many droplets during combustion,which has limited its application in many cases.The conventional halogen containing flame retardants and inorganic flame retardants have been facing more and more pressure:the former one can release toxic gases during combustion and has bioaccumulation;the later one can cause damage to mechanical properties due to the high loading requirements.Thus,it is necesarry and important to investigate environmental friendly and sustainablethe flame retardants for EVA polymers.Calcium alginate fiber(CAF)is a kind of natural and environmental fiber.The main raw material of CAF is alginic acid which is extracted from brown algae.Brown algae is much reserved in china.Besides,the production process of CAF is so simple that CAF can be easily produced on a large scale.In addition,CAF has good self-flame resistance and carbon-forming ability.Therefore,the CAF can be applied on improving the flame retardant and heat-conducting property of EVA.The main content of this research is as follows:In the first part,the effects of CAF on the fire performance of EVA composites were investigated.The CAFs with different lengths(5 mm,20 mm,40 mm)and different content(20 wt%,30 wt%,40 wt%)were introduced into EVA.With the increase of the content and length of CAF in the matrix,the flame retardancy of CAF/EVA composites were improved significantly.When adding 40 wt%CAF with a length of 40 mm to EVA,the LOI of CAF/EVA composites was increased from 18.3 to 22.7.The pHRR of CAF/EVA composites was decreased from 1383 kW/m2 to 681 kW/m2,by 50.8%.The improvement of flame retardancy of CAF/EVA composites is mainly due to the excellent carbon forming properties of CAF,which can protect the matrix in combustion.In the second part,CAF in association with the traditional intumescent flame retardants(IFR)was added to EVA to improvethe fire resistant properties of the composites.Compared to the EVA composites with only 33 wt%IFR,the flame retardancy of the EVA composites containing 30 wt%IFR and 3%CAF was improved.The LOI reached 31.6 and passed V-0 rating in the vertical combustion test.The results showed that the addition of CAF can promote the carbonization of IFR/EVA system.Thus,the amount of carbon residue was increased and the quality of carbon layer was improved.Besides,small amount of CAF could have a certain positive effection the mechanical properties of composites.As CAF has a relatively large aspect ratio,it is easier to form thermal conduction path in the EVA matrix.Therfore,the thermal conductivity of composites was increased with the the amount of CAF in the composites.In the third part,the effect of CAF on the fire performance of EVA composites contains aluminum hydroxide(ATH)and magnesium hydroxide(MH)respectively was investigated.The sample contained EVA 50wt%,ATH/MH 46t%and CAF 4 wt%showed the best flame retardant property.The LOI was 28.3 and reached V-0 rating in the vertical combustion.It is suggested that calcium alginate fiber improves the flame retardancy of EVA composite containing ATH/MH by promoting the quality of carbon residue during the combustion of the composite materials.