【作者】 仲含芳；

【导师】 江平开； 韦平；

【作者基本信息】 上海交通大学 ， 材料学， 2008， 博士

【摘要】 目前阻燃领域绿色环保的呼声日益高涨、各类阻燃法规日益严苛,特别是欧盟两项指令“废弃电子电器设备指令(West Electrical and Equipment Directive,WEEE)(2003年3月生效)及“电子电器设备中禁用有害物质指令(Restriction of Hazardous Substances Directive, RoHS)的颁布更加促使了无卤阻燃剂的研发。PC/ABS是工程塑料中产量最大的合金,具有优异的综合性能,广泛地应用于各类电子电器产品中,但是PC/ABS易燃,在很多应用中受到了一定的限制,因此阻燃PC/ABS的开发是较活跃的领域之一。无卤阻燃PC/ABS中使用的比较多的阻燃剂是含磷阻燃剂,常用的主要有磷酸三苯酯(TPP)、间苯二酚二缩合磷酸酯(RDP)和双酚磷系阻燃剂(BAPP)。含磷阻燃剂作用机理是在燃烧过程中促进聚合物成炭;有机硅化合物燃烧时形成的残炭具有高温热稳定性,能够有效地提高炭层的高温稳定性,在PC中具有一定的阻燃作用。在这基础上,本论文将有机硅元素和磷元素成功地结合到同一大分子中,合成了两类含磷聚硅氧烷阻燃剂,对其结构和性能进行了表征;研究了合成出的阻燃剂在PC/ABS中的应用以及阻燃剂和纳米蒙脱土在PC/ABS中的协同阻燃作用;通过对降解动力学以及降解产物的研究初步分析了阻燃剂的阻燃机理。1.含磷聚硅氧烷阻燃剂的合成及其结构表征首先通过9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)与乙烯基二甲氧基硅烷(VMDMS)的加成反应生成一种含磷硅氧烷,经过水解与脱水,得到中间体低聚含磷硅醇(DOPO-VMDMS),DOPO-VMDMS分别与氨基硅氧烷或二羟基硅烷进行共聚,合成出两类含磷聚硅氧烷阻燃剂(DVN和DVP)。用傅立叶变换红外光谱(FTIR)、核磁共振(NMR)氢谱、磷谱、凝胶色谱(GPC)、元素分析等对反应的中间产物以及最终产物进行结构分析表征;通过氮气和空气中的热重分析(TGA)对DVN和DVP的热性能进行了研究,结果表明DVN在氮气和空气中的残炭量都超过30wt.%,而DVP在空气中的残炭量也在20wt.%左右,同时发现DVN和DVP在空气中的成炭性均好于其自身在氮气中的成炭性,说明氧气的存在有利于促进聚硅氧烷成炭。2.含磷聚硅氧烷在PC/ABS中的应用利用自合成的含磷聚硅氧烷DVN和DVP对PC/ABS合金进行阻燃改性,采用直接熔融共混的方法得到无卤阻燃PC/ABS材料,通过氧指数(LOI)、垂直燃烧(VB)以及锥形量热仪(Cone)研究了阻燃剂对PC/ABS阻燃性能的影响,通过TGA研究了阻燃剂对PC/ABS热性能的影响,通过SEM研究了阻燃前后PC/ABS燃烧后残炭结构的区别,阻燃剂对PC/ABS力学性能的影响则通过拉伸和冲击测试来研究,通过EDS表征了P、Si元素在PC/ABS中的分布,从而推测阻燃剂在体系中的分散情况。研究表明:DVN或DVP的加入都可以显著地降低材料在燃烧过程中的热释放速率、总放热量、有效燃烧热、质量损失速率,提高燃烧成炭率以及极限氧指数值,但是DVN或DVP阻燃PC/ABS的点燃时间缩短了。TGA结果表明,相对PC/ABS来说,DVN或DVP阻燃PC/ABS的初始分解温度降低了;但是在氮气和空气中800℃下的残炭量都有所提高,并且DVP促进PC/ABS成炭的效果更为明显;阻燃PC/ABS的热降解速率要低于PC/ABS。在DVP添加量为10-15%时该阻燃体系能够通过垂直燃烧实验。与DVN阻燃PC/ABS相比,DVP阻燃PC/ABS在力学性能有所提高,但是相对于未阻燃的PC/ABS来说,还是下降较多。SEM结果和EDS结果表明,DVP在PC/ABS中的分散比较均匀。残炭的形貌研究表明,不论是DVN还是DVP阻燃的PC/ABS燃烧后形成的炭层都是表面致密、内部疏松的结构,该结构有利于阻止基体和外界进行能量和物质的交换,从而发挥较好的阻燃作用。3. DVP与OMT在PC/ABS中的协同阻燃作用研究了含磷聚硅氧烷DVP与有机纳米蒙脱土的在PC/ABS合金中的协同阻燃作用。用透射电子显微镜(TEM)和X射线衍射(XRD)考察了OMT在PC/ABS以及PC/ABS/DVP中的分散情况,结果表明蒙脱土在PC/ABS中呈插层型结构,在PC/ABS/DVP中呈插层/剥离型结构。由于DVP的存在,使得体系加工的粘度下降,剪切更为充分,从而使蒙脱土在PC/ABS中分散更为均匀。在锥形量热测试中发现,OMT的加入能够使得PC/ABS以及PC/ABS/DVP的热释放速率稍有降低,且大大延长了PC/ABS以及PC/ABS/DVP的点燃时间。PC/ABS/OMT插层结构和PC/ABS/DVP/OMT的插层/剥离型结构限制了分子链的热运动,且由于片层的阻隔效果有效地提高了材料的热稳定性,阻燃性能以及成炭性能。4.各阻燃PC/ABS体系的热降解过程的研究采用Flynn-Wall-Ozawa法研究了阻燃PC/ABS的降解动力学,通过TG-FTIR研究了在空气中DVP和DVP阻燃PC/ABS降解气相产物的结构,用FTIR和X光电子能谱(XPS)研究了PC/ABS和阻燃PC/ABS燃烧后残炭的化学结构,进而探讨阻燃剂阻燃机理。降解动力学研究结果表明,阻燃剂(DVN、DVP以及OMT)的加入降低了PC/ABS在降解初期的降解活化能;随着降解的进行,炭层逐渐形成,阻燃PC/ABS在高降解转化率时的降解活化能要比PC/ABS高,表明了阻燃PC/ABS形成的炭层的热稳定性高于PC/ABS;TG-FTIR和FTIR结果表明阻燃剂DVP在降解过程中确实形成了Si-O-Si交联结构;XPS的结果表明了PC/ABS/DVN在燃烧后Si和P元素有明显的富集现象,且结合能的结果证实了燃烧的残炭中磷的含氧酸以及P-Si键的存在,说明了Si和P存在协同成炭作用。更多还原

【Abstract】 Polycarbonate/Acrylonitrile-Butadiene-Styrene (PC/ABS) is a kind of engineering plastic with good properties. It combines good physical properties of PC and easy processing of ABS, and has been widely used in automobile panel, parts, mobile-phone housing, power tools which need high heat and flame retardance property. PC/ABS is easily combustible, in order to meet the requirement of some applications, flame retardant formulations are needed in PC/ABS. According to West Electrical and Equipment Directive, WEEE and Restriction of Hazardous Substances Directive, RoHS, some halogen-containing flame retardants are forbidden to use in some applications although they are very effective in most polymers. The halogen-free flame retardant used in PC/ABS are mostly phosphorus-containing flame retardant, they mainly acts in condensed phase to help PC/ABS charring during burning. Organic silicon compounds form char with high thermal stability while burning, and have been used as flame retardant in PC. According to the above discussion, in this paper, organic silicon and phosphorus are successfully combined in one molecular, two kinds of phosphorus-containing polysiloxanes flame retardants are synthesized. The structure and thermal properties of the flame retardants are studied, and then they are applied into PC/ABS, their effects on flame retardancy, thermal property and thermal degradation behavior are also studied.(1) The synthesis and characteristic of phosphorus-containing polysiloxanes First, 9,10-dihydro-9-oxa-10-phospha-phanthrene-10oxide (DOPO) was reacted with vinyl methyl dimethoxysilane (VMDMS) to form a phosphorus-containing siloxane, after hydroxylation and dehydration, a intermediate product named DOPO–VMDMS was obtained. After that, two kinds of phosphorus-containing polysiloxanes (DVN and DVP) were synthesized by condensation of DOPO-VMDMS and N-β-(aminoethyl)-γ-aminopropyl methyl dimethoxysilane (NMDMS) orα,ω-dihydroxide polydimethsiloxane (PDMS). The structure of the intermediate product DOPO–VMDMS and product (DVN and DVP) was characterized by Fourier transform infrared spectroscopy (FTIR), Nuclear Magnetic Resonance (1H NMR, 31P NMR), element analysis and so on. The thermal properties of DVN and DVP were investigated by thermogravimetric analysis (TGA) in both nitrogen and air. It was found that both DVN and DVP had better char yield in air than in nitrogen at 800℃which indicates that oxygen can help the charring progress of polysiloxane..(2) Application of phosphorus-containing polysiloxanes in PC/ABSThe phosphorus-containing polysiloxanes (DVN and DVP) were then incorporated into PC/ABS to improve its flame retardance. The flame retardance of the flame retarded PC/ABS was investigated by LOI, vertical burning test and cone calorimeter, the thermal stability was investigated by TGA, the structure of the char formed after fire were investigated by scanning electron microscopy (SEM). The results show that the LOI values of the flame retarded PC/ABS were increased by incorporation of DVN or DVP, the heat release rate (HRR), effective heat of combustion (EHC), total heat released (THC) and mass loss rate (MLR) were reduced in cone, and the char yield was increased in both cone and TG analysis. But the initial degradation temperature (IDT) in TGA and time to ignition (TTI) in cone were reduced which was caused by the relative early decomposition of phosphorus-containing polysiloxanes comparing with PC/ABS. SEM results reveal that the outer surface of the char layer of flame retarded PC/ASB after the LOI test was smooth and the inner side structure was swollen cells like, which benefits to the flame retardancy of PC/ABS. The char acts as an insulating barrier to reduce both radiant heat of flame and the diffusion of flammable degradation products into the combustion zone.(3) The synergistic effect of OMT and DVP in PC/ABSPC/ASB/OMT and PC/ABS/DVP/OMT were obtained by melting compounding; the flame retardance, thermal stability, the dispersion of OMT, and the structure of the char formed after fire were investigated. The dispersion of OMT in PC/ABS and PC/ABS/DVP was investigated by X-Ray Diffraction (XRD) and transmission electron microscopy (TEM). It was found that OMT in PC/ABS was intercalation structure while in PC/ABS/DVP was intercalation and semi-exfoliation structure. The incorporation of OMT can not improve the LOI and vertical burning test behavior of PC/ABS and PC/ABS/DVP, but it can low down the HRR, increase the TTI and char yield in the cone.(4) Study of the degradation behavior of flame retarded PC/ABSThe degradation behavior of flame retarded PC/ABS were investigated by TGA,TG-FTIR, FTIR and XPS. Flynrr-Wall-Ozawa method was used to calculate the degradation activation energies (E) of flame retarded PC/ABS at different degradation conversion degree (α). The results reveal that comparing with PC/ABS, E of DVN or DVP flame retarded PC/ABS decreased at lowαbut increased at highα. That mean the char formed by flame retarded PC/ABS had better thermal stability than PC/ABS. TG-FTIR and FTIR results convinced that during the degradation of DVP, a cross-linking structure with Si-O-Si formed. XPS results reveal that for PC/ABS/DVP, there are P-Si and phosphorous acids in the char formed after burning.更多还原