聚磷酸铵改善稻秸-高密度聚乙烯复合材料的理化性能
Ammonium polyphosphate improving physicochemical properties of rice straw-high density polyethylene composites
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摘要: 为了实现稻秸的资源化利用，以稻秸为增强相、高密度聚乙烯（high density polyethylene，HDPE）为基体相、聚磷酸铵（ammonium polyphosphate，APP）为阻燃剂制备了稻秸-HDPE复合材料，并利用热重分析仪、锥形量热仪和力学性能测试仪，探讨APP的添加量（0、8%、10%、12%）对复合材料热性能、阻燃性能和力学性能的影响。1）热分析结果表明：当增强相的质量分数为30%，HDPE的质量分数为70%时，以稻秸为增加相的复合材料初始分解温度和热解峰温低于以木材为增加相的复合材料，但残余率较高。当在稻秸-HDPE复合材料中添加10%～12% APP时，会促使稻秸-HDPE复合材料提前发生热降解，使得初始分解温度向低温方向移动8～9℃，并且APP的加入提高了稻秸-HDPE复合材料的热解峰温和残余率。2）阻燃性能结果表明，当增强相的质量分数为30%，HDPE的质量分数为70%时，稻秸-HDPE复合材料的阻燃性高于木材-HDPE复合材料。当在稻秸-HDPE复合材料中添加APP时，稻秸-HDPE复合材料的阻燃性能进一步提高。当APP添加量为12%时，稻秸-HDPE复合材料的平均热释放速率、热释放速率峰值和总热释放量达到133 kW/m2、357 kW/m2和105 MJ/m2，比未添加APP时分别降低了20.4%、20.7%和11.0%，氧指数达到23%，比未添加APP时增加了12.7%。3）力学性能表明，当增强相的质量分数为30%，HDPE的质量分数为70%时，稻秸-HDPE复合材料的韧性高于木材-HDPE复合材料，APP的加入使得稻秸-HDPE复合材料的韧性得到提高，而弯曲强度、拉伸强度几乎没有影响。研究结果为以稻秸为增强相制备阻燃型木塑复合材料提供参考。Abstract: Abstract: In recent years, plant fiber reinforced thermoplastic composites have been widely used as interior automotive panels, garbage pails, crates, and garden equipment due to their excellent durability, dimensional stability, high rigidity, and relatively low density. However, its poor fire resistance often limits its expansion into the residential construction industry and development of applications for the furniture industry. In order to improve the flame retardancy of the reinforced composites, fire retardant agents, such as halogen/nitrogen-containing substances, metal hydroxides, and phosphorus/silicon compounds, have been introduced. While there are environmental impact concerns, the most commonly used flame retardant additive is ammonium polyphosphate (APP). Recently, the synergistic effect between nano-SiO2 and ammonium polyphosphate (APP) in polymer and composites has been extensively investigated, and study has showed that the novel nano-SiO2/APP flame retardant could promote char formation, and improve the thermal stability of the char layer formed during combustion.China has been an important agricultural nation with 300 million tons of rice production annually. Using rice straw as a substitute feedstock material of wood fiber could be helpful for conserving valuable wood resources, protecting the environmental and contributing to sustainable development. Rice straw consists of cellulose, hemicellulose, lignin, silicon and pectin. Silicon, which is widely distributed in the surface of rice straw through biomineralization, could be also used as a synergistic agent of APP. In this paper, rice straw-high density polyethylene composites (RPC) with ammonium polyphosphate (APP, 0, 8%, 10%, and 12%) were prepared to investigate the effects on the thermal properties, flame retardancy, and mechanical properties of RPC using thermogravimetric analysis (TG), cone calorimentry analysis (Cone) and mechanical measurements. The mechanism of flame retardancy are also investigated with scanning electric microscopy/x-ray energy dispersive spectroscopy analysis (SEM-EDXA).1) TG results showed that: RPC had a lower initial temperature (Tinitial), and peak temperature of thermal degradation (Tpeak) when compared to wood-high density polyethylene composites (WPC). Furthermore, RPC possessed higher char residues. Introducing APP to RPC, Tinitial was shifted to a lower temperature of 8-9℃, that means APP made the thermal degradation of RPC take place earlier. APP also increased Tpeak and improved the char residues. 2) Cone results showed that RPC exhibited better flame retardancy, and the incorporation of APP to RPC could improve the flame ratardancy. The lowest heat release rate (HRR) and total release rate (THR) both occurred when the APP addition reached up to 12%, with corresponding to a decrease of 20.4%, 20.7% and 11.0% in aHRR, pkHRR, and THR respectively, and an increase of 12.7% in the limited oxygen index (LOI). 3) The mechanical properties showed that RPC possessed better toughness, and the APP addition had a positive effect on toughness, while it had no appreciable effect on the flexural and tensile strength of RPC.
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Keywords:
- composite materials /
- high density polyethylenes /
- toughness /
- rice straw /
- APP /
- flame retardancy /
- thermal property
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