Preparation Of Sb₂O₃/DOP/PVC Flame Retardant Composites And Research On Its Properties

Polyvinyl chloride?PVC?is widely used in the engineering field due to its advantages of corrosion resistance,plasticization,and good insulation.The chlorine content of PVC is as high as 56%,resulting that its limit oxygen index?LOI?between 45%-49%.However,with using of plasticizers and other additives,the flame retardancy of PVC has been seriously reduced.At this stage,the engineering PVC field usually adopts the method of adding micro antimony trioxide?micro-Sb₂O₃?to improve its flame retardant performance.Despite great advance,it remains highly attractive but challenging to create soft-PVC with high flame retardance and high mechanical bechavior.The mechanical properties of matrix material under large external stresses were serious damaged for split effect of micron particles.Mechanical high-energy ball milling method effectively nanometerized micro-Sb₂O₃,but also had the advantages of low cost and simple process.Of course,the nanometer antimony trioxide particles?nano-Sb₂O₃?obtained by mechanical high-energy ball milling required further processing for surface modification in older toimprove the dispersion of the particles.In this paper,micro-Sb₂O₃ was nanometerized by high-energy mechanical ball milling.Then,using industrial plasticizer dioctyl phthalate?DOP?and the silane coupling agent KH791 as modifiers,through mechanical high-energy ball milling as a processing method,the surface modification of nano-Sb₂O₃ was completed.X-ray diffraction analysis?XRD?was used to detect the change of crystal form of Sb₂O₃.The surface modification effect of nano-Sb₂O₃ was characterized by Fourier infrared?FTIR?.The dispersion was charactered by particle size analysis and transmission electron microscopy?TEM?to obtain the best modification method.Secondly,nano-Sb₂O₃ and micro-Sb₂O₃ with equal mass ratio were added to the PVC matrix to prepare PVC-based composite materials.Through the limit oxygen index test?LOI?,vertical combustion level test?UL-94?,cone calorimeter test?CCT?to study the diversity of micro-Sb₂O₃ and nano-Sb₂O₃ to the flame retardant properties of PVC-based composite materials.The thermal stability of composite materials was studied by thermogravimetric analysis?TGA?.The mechanical behavor of PVC matrix composite was investigated by tensile strength and Young's modulus.Finally,modified nano-Sb₂O₃ with equal mass ratio was added to the matrix material to prepare the PVC-based composite.Through the above detection methods,the effects of different contents and types of modifier-modified nano-Sb₂O₃ on the flame retardancy,thermal stability,tensile strength and Young's modulus of PVC-based composites were analyzed.In summary,a PVC-based composite material with high flame retardancy yet good mechanical properties would be prepared.The main research contents and results are summarized as follows:?1?After nanometerization by mechanical high-energy ball milling,the particle size was effectively reduced,making its main particle size distribution between 90-200 nm.In this process,the Sb₂O₃ crystal form was not changed.?2?The surface modification process did not change the crystal structure.Through FTIR characterization,it found that the modifiers DOP and KH791 were successfully connected to the surface of nanoparticles.Through particle size and TEM analysis,it indicated that the diameter of modified nanoparticles generally reduced,and greatly improved the dispersibility.Among them,nano-Sb₂O₃ modified by 2.0 wt%-KH791 possessed the best dispersion with the particle size range of 80-140 nm.Through the Zeta potential analysis,it found that different modifiers had different effects on the absolute value of the Zeta potential.The absolute value of Zeta potential on the surface of nanoparticles modified by DOP showed a decreasing trend,which was contrary to the effect of modification by KH791.Among them,the absolute value of Zeta potential of nano-Sb₂O₃ modified by 2.0 wt%-KH791 increased to34.5 mV,while the value reduced to 3.5 mV modified by 7.0 wt%-DOP.?3?When the equal mass ratio of micro-Sb₂O₃ and nano-Sb₂O₃ was added to the PVC matrix,the flame retardant performance of nano-Sb₂O₃ on PVC composites was significantly better than that of micro-Sb₂O₃.Characterized by the cone calorimetry test,nano-Sb₂O₃ was more significant in reducing the threat of soft PVC fire.The THR and TSP values of 2.0 wt%-nano-Sb₂O₃/DOP/PVC composites were reduced to 28.6 MJ/m² and 10.9 m²,respectively.The carbon layer on the surface of the burning residue was dense and had good flame retardant properties.Through thermogravimetric analysis,it found that when the content of nano-Sb₂O₃ in the PVC-based composite material reached 2.0 wt%,the residual carbon content reached 9.010%,which the thermal stability was significantly better than PVC-based composite materials containing the same mass ratio micro-Sb₂O₃.In the tensile test,it indicated that the decline trend of nano-Sb₂O₃/DOP/PVC composites was more gradual.?4?By comparing the addition of 2.0 wt%-nano-Sb₂O₃ modified and unmodified for PVC-based composite materials,it found that the use of different ratios of modified nano-Sb₂O₃ had different effects.In the LOI test,the PVC-based composite material with nano-Sb₂O₃ modified by 2.0 wt%-KH791 had the highest value of 30.4%.In the cone calorimetry test,the composite material with nano-Sb₂O₃ modified by 2.0 wt%-KH791 had the lowest THR value with the shortest burning time of 169 s,while the HRR peak reached259.97 kW/m².The composite material with 5.0 wt%-DOP modified nano-Sb₂O₃ provided with the lowest HRR peak yet the longest effective burning time.The HRR peak and effective burning time of the composites with nano-Sb₂O₃ modified by 2.0 wt%-DOP and 1.0 wt%-KH791 were effectively reduced.Through thermogravimetric analysis,it revealed that the composite material with nano-Sb₂O₃ modified by 2.0 wt%-KH791 possessed the best thermal stability with residual carbon rate of 9.556%.In the tensile test of PVC-based composites,it shown that the composite material with nano-Sb₂O₃ modified by 5.0 wt%-DOP possessed the most obvious effect,which tensile strength and Young's modulus value of composits rosed to15.9 MPa and 2.1 GPa,respectively.