Preparation And Properties Of Coal-based Environment-friendly PVC/ASA Flame Retardant And Antistatic Composites

As an important energy source in China,excessive coal combustion will cause air pollution.The accumulation of solid waste coal gangue（CG）in coal mining also affects the ecological environment.In response to the national call for"clean and efficient coal utilization",coal-based environment-friendly flame-retardant and antistatic polyvinyl chloride/acrylonitrile-styrene-acrylate（PVC/ASA）resin composites were prepared by melting blending method,which can be divided into three parts.Firstly,based on the graphite-like lamellar structure of Coal,dimethyl sulphoxide（DMSO）was used to intercalate the Coal to obtain the intercalated modified Coal（A-Coal）.Then,A-Coal was incorporated into PVC/ASA via melt blending,and PVC/ASA/unmodified Coal（M-Coal）composites were also prepared for comparison.The research shows that although M-Coal improved the flame-retardant properties of PVC/ASA material,it was inferior to PVC/ASA composites with the same A-Coal loading.PVC/ASA/15A-coal composites were V-1 rating in vertical combustion（UL-94）test,limit oxygen index（LOI）was 30.0%,0.8%higher than PVC/ASA/15M-coal material.In addition,there were many uneven but dense vesicles on the surface of carbon residue after PVC/ASA/15A-coal burning,which was consistent with the result of carbon yield.In terms of antistatic properties,the surface resistivity （ρ_s） and volume resistivity （ρ_v） of PVC/ASA/Coal materials decreased nonlinearly,and there was no apparent percolation threshold.The and of PVC/ASA/15A-Coal were 9.33×10⁷ Ωand1.26×10⁷ Ω·cm.Secondly,nontoxic and efficient alkaline calcium-based CG thermal stabilizer（Y-CG）was prepared with cheap and readily available CaO,CG and stearic acid（SA）.The mass ratio of CG to water was 1:7,the loading of Ca（OH）₂between CG sheets reached the maximum value of 3.01 mmol/g.Then,different Y-CG content was mixed into PVC material to test its thermal stability.The results showed that the Congo red test showed thermal stabilization time of PVC improved up to 55.9 min with 10 phr Y-CG.The torque rheological test showed dynamic thermal stabilization time of PVC improved up to 62.10min with 10 phr Y-CG.Still,Y-CG can absorb HCl and initiate the carbonization of PVC to inhibit degradation.At the same time,the slightly alkaline calcium stearate formed by SA and Ca（OH）₂ can absorb HCl,and can also be used as a compatibilizer to improve the compatibility between Y-CG and PVC.Compared with the commonly used thermal stabilizers,the thermal stability of Y-CG was only slightly worse than that of hydrotalcite thermal stabilizers.Finally,the Y-CG thermal stabilizer developed by our group was prepared to replace the composite lead salt thermal stabilizer in PVC/ASA/A-coal to prepare the PVC/ASA/A-coal/Y-CG flame-retardant and antistatic composites.The flame-retardant mechanism of PVC/ASA/A-Coal/Y-CG material mainly included incombustible gas,maze effect,carbon residue layer and blowing-out effect through LOI value,UL-94 and SEM test.The results showed that PVC/ASA/12A-Coal/10Y-CG composites were classed V-0 rating in the UL-94 test,the LOI value was the maximum value of 31.8%,1.8%higher than PVC/ASA/15A-Coal.As with PVC/ASA/A-Coal,and values PVC/ASA/A-Coal/Y-CG first decreased and then increased,which dropped to the minimum values of 5.14×10⁶ Ωand 9.05×10⁵ Ω·cm at 12 phr A-Coal,which meet the standard of antistatic material.In terms of mechanical properties,the tensile strength and impact strength of PVC/ASA/A-Coal/Y-CG materials increased first and then decreased,determined by the filler dispersion in the matrix.The tensile strength and impact strength of PVC/ASA/12A-Coal/10Y-CG material were the maximum values of 65.03 MPa and17.52 k J/m²,which were 8.87 MPa and 10.06 k J/m² higher than PVC/ASA material,and3.75 MPa and 3.22 k J/m² higher than PVC/ASA/15A-Coal material.To sum up,A-Coal and Y-CG act as a multi-functional additive for PVC/ASA with high efficiency,not only reinforce and toughen PVC/ASA composites,but it can also enhance their flame-retardant and antistatic properties.This paper contains 39 figures,19 tables and 112 references.