【作者】 陈小随；

【导师】 张胜；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2011， 博士

【摘要】 聚丙烯(PP)作为五大通用塑料之一,具有密度小、易加工、吸湿性低、综合力学性能好、耐化学腐蚀、电绝缘性能好等优点,广泛应用于建筑材料、电工电气、通讯交通、家用电器等领域。然而,因PP的碳氢结构使PP极易燃烧(氧指数仅为17.4%左右),燃烧速率快并伴有熔滴,从而限制了聚丙烯材料的应用范围,因此PP的阻燃研究日益受到工业和学术界的关注。阻燃剂的加入通常会破坏PP材料的整体性和连续性,使PP材料的力学性能恶化,进而影响了PP阻燃材料的应用。因此,在提高PP材料阻燃性能的同时保持或提高阻燃材料的力学性能具有非常重要的意义。本论文选择了三种增强材料(分别为纳米蒙脱土OMMT、芳纶纤维AF和玻璃纤维GF)和两种不同体系的阻燃材料复配应用到PP中,制备了高性能的聚丙烯阻燃复合材料。采用广角X射线衍射仪(WXRD),透射扫描电子显微镜(TEM)对OMMT在PP基体中的分散形态和插层结构进行了表征；采用拉伸、弯曲和缺口冲击试验对PP复合材料的力学性能进行了测试；采用差示扫描量热法(DSC)、偏光显微镜(POM)对复合材料中PP的结晶性能进行了分析；采用热重-差热分析(TG-DTA)、氧指数(LOI)、垂直燃烧测试(UL-94)、锥形量热(CONE)、扫描电子显微镜(SEM)和红外光谱(FTIR)对PP复合材料的热性能、阻燃性能、残炭结构和形态进行了分析和表征,并对其阻燃机理进行了初步研究和推测。本论文归纳起来可以分为以下三个部分：第一部分以纳米蒙脱土(OMMT)为增强材料,十溴二苯乙烷／三氧化二锑(DBDPE/Sb2O3, D-S)和膨胀型阻燃剂(MPP/PER, IFR)为阻燃体系,分别制备了复合材料PP/OMMT、PP/D-S/OMMT和PP/IFR/OMMT。研究结果表明：相容剂PP-g-MAH的引入和阻燃剂D-S、IFR的添加均可以增大PP复合材料中OMMT的层间距,提高OMMT的分散性,获得了较好的插层型或剥离型结构。OMMT在PP复合材料中起到了异相成核的作用,提高了PP的结晶速率和结晶度,使PP球晶更加细化,排列更加紧密。另外,OMMT的纳米结构和增强作用使复合材料PP/D-S/OMMT和PP/IFR/OMMT的拉伸强度和缺口冲击强度均较纯PP提高了许多,热稳定性和阻燃性能也有明显改善。如其T50%分别较纯PP提高了20-30℃,残炭量最高分别可达13.4%和24.4%,LOI最高分别可达24.2%和28.5%,UL-94等级最高分别可达V-0和V-1。复合材料PP/30phrD-S/5phrOMMT和PP/30phrIFR/5phrOMMT的峰值热释放速率(PHRR)、平均热释放速率(AHRR)、热释放总量(THR)、平均质量损失率(AMLR)较纯PP分别下降了60.2%和58.3%、52.7%和46.0%、34.7%和52.5%、31.2%和63.2%,且燃烧后残炭形态不变,炭层结实。OMMT和D-S、IFR在PP材料中表现出了较好的阻燃协同效应。第二部分以芳纶纤维(AF)为增强材料,分别以D-S和IFR为阻燃材料,制备了复合材料PP/AF, PP/AF/D-S和PP/AF/IFR。采用SEM,AFM和FTIR对AF的表面形态和结构分析表明磷酸酯偶联剂成功地接枝到AF表面。偶联剂改性的最佳实验条件为：醇水质量比为9：1,浸渍时间为1h,偶联剂浓度为1%。DSC和POM测试结果表明,AF在PP/AF材料中有异相成核作用,缩短了PP的结晶诱导期,提高了PP的结晶速率和结晶度,降低了PP的球晶尺寸；当AF含量为20phr时,PP/AF复合材料的综合力学性能最佳。PP/AF/D-S和PP/AF/IFR的T50%均较纯PP提高了25-30℃,残炭量最高分别可达17.7%和24.4%,放热晗的最大下降幅度分别为60.0%和59.3%,UL-94等级分别最高可达V-0和V-1。与纯PP相比,复合材料PP/20phrAF/30phrD-S和PP/20phrAF/30phrIFR的PHRR、AHRR、THR、AMLR、AEHR分别下降了78.8%和75.8%、71.2%和50.6%、75.0%和69.7%、36.8%和60.5%、68.5%和23.1%,且其生烟量几乎为零,残炭结实形态无变化。AF的机械强度高、耐热性能好,在PP复合材料中起到了“骨架”作用,可以承担大部分的外界应力和载荷同时将其由局部向整体分散,从而提高了整个复合材料的力学性能。此外,AF燃烧后形态不变成炭量高,提高了PP复合材料的成炭量和热稳定性能,再辅以D-S的气相阻燃作用和IFR的凝聚相膨胀炭层的保护作用,使复合材料PP/AF/D-S和PP/AF/IFR拥有优异的阻燃性能。第三部分以玻璃纤维(GF)为增强材料,同样以D-S和IFR为阻燃材料,制备了复合材料PP/GF, PP/GF/D-S和PP/GF/IFR。同样采用磷酸酯偶联剂对GF表面进行改性处理。SEM、AFM和FTIR测试表明磷酸酯偶联剂成功接枝到GF表面,提高了GF和PP之间的界面黏合性,其最佳改性条件为：醇水质量比9：1,浸渍时间为1h,偶联剂浓度为1.5%。GF在PP复合材料中也有异相成核作用,提高了PP的结晶速率和结晶度,减小了PP的球晶尺寸；当GF含量为40phr时,PP/GF复合材料的综合力学性能最佳。GF的加入使PP/GF/D-S和PP/GF/IFR复合材料的力学性能均比PP/D-S和PP/IFR提高了许多,但GF的增强效果不如AF。复合材料PP/GF/D-S和PP/GF/IFR的T50%较纯PP提高了20-40℃,残炭量最高分别可达17.7%和30.7%,放热晗也有所下降。锥形量热测试表明,与纯PP相比,复合材料PP/20phrGF/30phrD-S和PP/20phrGF/30phrIFR的PHRR、AHRR虽然均比纯PP有所下降,但是其AHRR、AMLR分别比PP/D-S和PP/IFR反而上升了24.6%和19.3%、59.4%和105.0%；且其残炭形态变化明显(尤其是PP/GF/IFR已完全熔融),残炭强度较低。此外,复合材料PP/GF/D-S和PP/GF/IFR的LOI均比PP/D-S和PP/IFR低；PP/GF/D-S的UL-94等级最高仅为V-2级,而PP/GF/IFR的则均不合格。GF的加入恶化了复合材料PP/GF/D-S和PP/GF/IFR的阻燃性能。更多还原

【Abstract】 Polypropylene (PP) has been widely used in various fields, such as construction, electronic and electric, communication and household appliance, due to its overwhelming advantages such as low density, ease of processing, low hygroscopic, nice overall mechanical properties, resistance to chemical erosion and excellent electric insulation. However, PP is rather flammable with a limited oxygen index (LOI) value of 17.4% because of its wholly carbon-hydrogen structure. Moreover, PP burns rapidly and releases plenty of heat accompanying melt-dripping, which cannot meet the requirements in many cases, and therefore it has attracted more and more attention to reduce its flammability. The addition of flame retardants can usually cause negative effects to the mechanical properties of PP composites. Therefore, it is of great significance to improve the flame retardancy and mechanical properties simultaneously. Three kinds of reinforcing materials including nano-montmorillonite, aramid fibers and glass fibers and two types of flame retardants were introduced to PP composites. The intercalative effect of OMMT in PP composites was analyzed by wide X-ray diffraction (WXRD) and transition electron microscopy (TEM). The mechanical properties of PP composites were conducted by tensile, flexural and notched impact tests. The crystallinity of PP was characterized by differential scanning calorimetry (DSC) and polarizing optical microscope (POM). The thermal behavior, flammable property, char morphology and structure were investigated by thermogravimetric (TG), differential thermal analyzer (DTA), limited oxygen index (LOI), vertical burning test (UL-94), cone calorimetry (CONE), scanning electron microscope (SEM) and Fourier transition infrared spectroscopy (FTIR). The flame retardant mechanism was also proposed and discussed.This paper can be divided into three parts:the mechanical, thermal, crystalline property and flame retardancy of PP/OMMT composites, PP/AF composites and PP/GF composites containing different flame retardant systems respectively.In the first part, PP/OMMT, PP/D-S/OMMT and PP/IFR/OMMT composites were prepared by using organic-montmorillonite (OMMT) as reinforcing material, decabromodiphenyl ethane/antimony trioxide (DBDPE/Sb2O3, D-S), intumescent flame retardant (melamine polyphosphate and pentaerythritol, MPP/PER, IFR) as flame retardants. The results show that the addition of PP-g-MAH, D-S and IFR can increase the interlayer spacing and improve the dispersion condition of OMMT. It has been demonstrated that intercalated or even exfloliated structure has been formed in PP/OMMT composites. OMMT can act as heterogeneous nucleation which increases the crystallization speed and degree of PP, and thus make PP spherulites grow smaller and align more regular. Moreover, the nanosize effect and reinforcement of OMMT can not only improve the tensile and notched impact properties of PP/D-S/OMMT and PP/IFR/OMMT composites, but also can enhance their thermal property and flame retardancy. The T50% of PP/D-S/OMMT and PP/IFR/OMMT composites are 20～30℃higher than that of pure PP, while the maximal char yield of the two composites can reach up to 13.4% and 24.4% respectively. The LOI value has been increased up to 24.2% and 28.5% and the UL-94 test can reach V-0 and V-1 respectively after the addition of D-S and IFR. Moreover, comparing with pure PP, the peak heat release rate (PHRR), average heat release rate (AHRR), total heat release (THR), average mass loss rate (AMLR) of PP/30phrD-S/5phrOMMT and PP/30phrIFR/5phrOMMT composites are reduced by 60.2% and 58.3%、52.7% and 46.0%、34.7% and 52.5%、31.2% and 63.2% respectively. The char residue of above two composites can remain its original morphology with firm structure. Hence, there is a nice synergistic effect on flame retardancy between OMMT and D-S or IFR in PP composites.The second part of this paper studies the properties of PP/AF, PP/AF/D-S and PP/AF/IFR composites composed of AF and D-S, IFR. AF was modified by phosphate coupling agent and the best modification condition is as follows:the mass ratio of ethanol and water is 9:1, the immersion time is 1h and the concentration of coupling agent is 1%. DSC and POM results show that AF can improve the crystallization speed and degree of PP but decrease the size of PP spherulites by acting as a heterogeneous nucleating agent. The PP/AF composite with 20phr AF has optimal mechanical properties. The T50% of PP/AF/D-S and PP/AF/IFR composites are 25～30℃higher than that of pure PP, while the maximum char yield is raised up to 17.7% and 24.4% respectively, the maximum exothermal fusion is reduced by 60% and 59.3% respectively, the maximum rate in UL-94 is V-0 and V-1 respectively. The PHRR、AHRR、THR、AMLR、AEHC of PP/20phrAF/30phrD-S and PP/20phrAF/30phrIFR composites are decreased by 78.8% and 75.8%、71.2% and 50.6%、75.0% and 69.7%、36.8% and 60.5%、68.5% and 23.1% respectively, and there was almost no smoke released in above two composites, when comparing with that of pure PP. Moreover, the morphology of above two samples before or after being heating is almost the same and the residue char is strong. AF with superior mechanical and thermal properties can act as "skeleton" materials and hinder the move of PP chains and thus improve the thermal stability and char yield of PP composites. The protective effect of D-S in gas phase together with the improved char protective effect in solid phase by IFR and AF make the flame retardancy of PP/AF/D-S and PP/AF/IFR improved greatly.The third part is about the properties of PP/GF, PP/GF/D-S and PP/GF/IFR composites when GF was used as reinforcing material while D-S and IFR were added as flame retardants. The surface of GF was also modified by phosphate coupling agent showing a better interface cohesion between GF and PP proved by SEM and FTIR tests. The optimal modification condition is listed below:the mass ratio of ethanol and water is 9:1, the immersion time is 1h and the concentration of phosphate coupling agent is 1.5%. The crystallization speed and degree of PP are improved while the size of PP spherulite decreases in the presence of GF in PP/GF composites. The mechanical properties of PP/GF/D-S and PP/GF/IFR composites are higher than that of PP/D-S and PP/IFR, but the reinforcing effect on mechanical properties of GF is lower than that of AF. The T50% of PP/GF/D-S and PP/GF/IFR composites are about 20～40℃higher than that of pure PP, while the maximum char yield is improved to 17.7% and 30.7% respectively, the exothermal fusion is also decreased a lot. The results from cone calorimetry tests show that:the PHRR and AHRR of PP/20phrGF/30phrD-S and PP/20phrGF/30phrIFR composites are decreased slightly compared with that of pure PP; however, the AHRR and AMLR are increased by 24.6% and 19.3%、59.4% and 105.0% respectively when compared with that of PP/D-S and PP/IFR composites. Moreover, the char morphology of above two composites changes greatly, especially for the latter one which has been melted completely during combustion. The LOI values of PP/GF/D-S and PP/GF/IFR composites are both lower than that of PP/D-S and PP/IFR, and the UL-94 rate of the former is V-2 but the latter is failed. Therefore, it is concluded that GF can cause negative effect on flame retardancy of PP composites.更多还原