界面阻燃化玻璃纤维协同聚磷酸铵增强阻燃聚乳酸树脂

The synergism between interfacial flame-retarded glass fibers and ammonium polyphosphate on the flame-ratarding and reinforcing effects in polylactic acid resin

摘要:

采用短切玻璃纤维（GF）作为载体，先经3-氨丙基三乙氧基硅烷（KH550）对其表面氨基化处理后（GF-KH550），再以三乙胺为缚酸剂和催化剂，三氯氧磷（POCl3）和4, 4-二氨基二苯甲烷（DDM）为反应单体，在玻璃纤维表面原位聚合，获得超支化聚磷酰胺界面阻燃化玻璃纤维（GF@HBPN），并与聚磷酸铵（APP）一起应用于聚乳酸树脂（PLA），制备了系列GF-KH550/PLA、GF@HBPN/PLA和APP/GF@HBPN/PLA复合材料，对复合材料的热稳定性、力学和阻燃性能进行了系统分析。结果表明，与纯PLA相比，GF-KH550/PLA复合材料的拉伸强度有了明显提高，但玻璃纤维的“烛芯效应”严重恶化了其燃烧性能； GF@HBPN/PLA复合材料的拉伸强度也有提高，且燃烧过程中GF表面形成的界面残炭抑制其“烛芯效应”，改善了其燃烧性能（UL-94 V-2），但不足以达到理想阻燃效果。对于APP/GF@HBPN/PLA复合材料，当APP含量达10%、GF@HBPN含量（GF和APP含量以复合材料的整体质量为基准）达30%时，其极限氧指数（LOI）提升至26.8%，垂直燃烧等级达UL-94 V-0级，且其峰值热释放率（PHRR）、总热释放量（THR）和最大质量损失率（MLRmax）也较纯PLA分别下降了31.39%、23.57%和49.26%，显示出优异的火安全性能。

Abstract:

The chopped glass fibers (GF) were first modified by 3-aminopropyltriethoxysilane (KH550) (GF-KH550), and then were coated by a layer of hyperbranched polyphosphamide (HBPN) to form interfacial flame-retarded GF@HBPN by in situ polymerization among phosphorus oxychloride (POCl3) and 4, 4-diaminodiphenylmethane (DDM) with triethylamine as acid binding agent and catalyst. Then a series of polylactic acid (PLA) composites including GF-KH550/PLA、GF@HBPN/PLA and APP/GF@HBPN/PLA composites were prepared by mixing various GF (GF-KH550 or GF@HBPN) with ammonium polyphosphate (APP). Their thermal, mechanical, and flame-retarding properties were systematically characterized and analyzed. Compared with neat PLA, GF-KH550/PLA composites exhibited significantly improved tensile strength but seriously worsened flammability caused by the obvious “candle wicking” effect of smooth GF, while GF@HBPN/PLA showed moderately enhanced tensile strength and improved flame-retardancy (passing UL-94 V-2 rating) due to the interfacial char residue formed by the pyrolysis of HBPN on the GF surface. To achieve a satisfied flame retardancy, APP was added into GF@HBPN/PLA composites. It is found that APP/GF@HBPN/PLA composite containing 10%APP and 30%GF@HBPN reached a high LOI value of 26.8% and achieved a UL-94 V-0 rating, moreover, its peak heat release rete (PHRR), total heat release (THR) and maximum mass loss rate (MLRmax) also decreased greatly in comparison with neat PLA, which were 31.39%, 23.57% and 49.26% respectively, illustrating superior fire safety of the above PLA composite.