Preparation And Properties Of Halogen-free Flame Retardant Antistatic Wood-plastic Composites

Wood plastic composite(WPC)has been accepted by more and more people as a new green environmental protection material,and is widely used in gardens and interior decoration fields.Since the main component of wood-plastic is made of wood powder and polymer,it is easy to burn at high temperature,generating a large amount of volatile gas.It is difficult for WPC to self-extinguish after ignition,resulting in a great safety hazard.Since both wood fiber and plastic are good electrical insulators,they still belong to electrical insulators after compounding and static charge accumulation readily occurs during usage,which causes distortion of precision instruments,and also causes accidents such as fire,explosion,electric shock.In view of this,the flame retardant and antistatic properties of wood-plastic materials become particularly important.This work is mainly aimed at the flame retardant and antistatic properties of WPC.whose content includes the following aspects:Firstly,PP/WF composites were prepared by solution method.The mechanical properties,electrical and thermal conductivity,thermal stability,flame retardant and crystallization behavior of PP/WF wood-plastic composites with different ratios of flame retardant APP and conductive filler Fe powder were studied.The results showed that due to the agglomeration of Fe and the toughening effect of rigid particles,excessive Fe led to a decrease of tensile strength and an increase of impact strength.The Fe powder cannot form an effective thermal network and conductive network in the composites at a low content,and the electrical and thermal conductivity is very small.As the Fe content increased,the thermal conductivity of the composite material increased remarkably.The results of heat stability test and combustion test showed that the addition of APP could promote the thermal decomposition of wood powder in the composite to form a dense carbon layer,protecting the PP matrix.The addition of APP can significantly reduce the Heat Release Rate(HRR)and the Total Heat Release(THR)of PP/WF composites,which effectively prevented the composites from burning.Moreover,even small amount of Fe can act as a flame retardant.In terms of crystallization,rapid cooling will accelerate the crystallization process of PP;on the other hand,Fe will also hinder the movement of PP segments and inhibit the crystallization of PP to some extent.Secondly,the mechanical properties,electrical and thermal conductivity,thermal stability and flame retardancy of PS/WF composites were studied.The results showed that with the decrease of Fe content and increase of APP content,the tensile strength of wood-plastic composites tended to increase,and its maximum value increased to 34.0%while the impact strength of composites showed a decrease trend.The results of electrical and thermal conduction showed that with the increase of Fe content,the conductive filler became more evenly distributed in the matrix,and the conductive and heat-conductive paths were good,showing stronger electrical and thermal conductivity.Because the inherent insulation of PS plastic was better than PP,PS/WF composites with same WF content displayed higher resistivity than PP/WF counterparts.The combustion test showed that after adding APP,both HRR and THR values of the composites were significantly reduced,e.g.,the LOI value reached 39%,passing the V-0 rating,which suggested that APP could effectively prevent the combustion process of WPC.In addition,PS/WF composites were prepared by solution method,and a magnetic field was also applied during the solid-liquid conversion stage to change the distribution status of Fe in the composites.Mechanical properties,electrical and thermal conductivity,thermal stability,flame retardant properties were examined.It was shown that the magnetic field orientation had some influence on the tensile properties.impact properties,combustion properties and thermal decomposition behavior of PS/WF wood-plastic composites.Due to the exertion of the magnetic fields.Fe particles which were originally randomly distributed can be rearranged along the direction of the magnetic fields,thus exhibiting higher thermal conductivity.In order to further study the relationships between the thermal conductivity of composite materials and conductive fillers,the experimental thermal conductivities were compared with the predicted values from three classical heat conduction equations,and the Agari model was found to present the best fitting result.The model parameters indicate that the PS/WF composites after magnetic field orientation is more likely to form a heat-conductive chain than those without magnetic treatment.