【作者】 王军；

【导师】 杨世伟；

【作者基本信息】 哈尔滨工程大学 ， 材料科学与化学工程， 2010， 博士

【摘要】 聚苯并嗯嗪是在传统酚醛树脂的基础上发展起来的一种新型热固性树脂。此类树脂除具有酚醛树脂优良的耐热性和阻燃性外,还在一定程度上改善了酚醛树脂的脆性和尺寸不稳定性,最显著的优点是通过自身开环聚合形成三维网络结构,固化时无小分子释放,制品孔隙率低,其体积近似零收缩,有高的Tg和热稳定性,以及良好的机械性能、电气性能、阻燃性能和高的残碳率,因而在先进复合材料基体树脂、电子封装材料等方面有潜在应用。本文以苯酚和芴酮为原料,在液体酸和固体酸催化剂存在的情况下,利用微波辅助合成技术,合成了具有芴基双酚结构的单体,并与甲醛和伯胺反应,制备了系列双官能度芴基苯并噁嗪单体,通过红外光谱(IR)、核磁共振氢谱(1H NMR)和碳谱(13C NMR)对产物结构进行了表征,利用差示扫描量热仪(DSC)、IR、动态热机械分析仪(DMA)、热重仪(TGA)等对聚合反应行为、固化动力学、聚合物网络结构以及纯苯并嗯嗪和共混树脂的性能进行了研究。实验结果表明,双酚芴的优化合成工艺条件为：酚酮物质的量比8：1,β-巯基丙酸与芴酮物质的量比为0.05：1,液体酸法(硫酸、甲基磺酸)催化剂质量分数为2%-5%(占反应物料,以下同),微波辐射时间30 min,反应温度45-55℃,双酚芴收率大于83%；固体酸法(磷钨酸、强酸性阳离子交换树脂)催化剂质量分数为6%-9%,微波辐射反应时间90 min,反应温度130℃,双酚芴收率在70%以上,熔点223-224℃。其中,强酸性阳离子交换树脂法是今后发展的方向。以双酚芴、甲醛和伯胺(包括苯胺、邻甲苯胺、间甲苯胺、对甲苯胺、3,5-二甲基苯胺、丁胺、辛胺、环己胺、烯丙胺、炔丙胺)为原料,采用混合溶剂法制备了十种新型芴基苯并嗯嗪单体。单体优化的合成工艺条件为：双酚芴、甲醛和伯胺物质的量比为1：4：2,无水乙醇和二氧六环作为溶剂,二者的体积比为1：1,甲醛和伯胺的加成反应在5℃以下,反应时间2h,加成产物与双酚芴的成环反应温度为90-100℃,反应时间5-7 h,芴基苯并噁嗪单体收率在50%-63%之间。芴基苯并噁嗪呈典型1,3-苯并噁嗪热开环聚合特征,聚合物链由酚Mannich桥键、芳香胺Mannich桥键、亚甲基链以及分子间和分子内氢键组成,芳香胺间位有取代基时,其对位产生活性位,从而增加了活性交联点。通过动态DSC曲线分析确定了芴基苯并噁嗪的固化工艺条件为：170-180C/2h→200-220℃/3h→240-250℃/2h；利用Kissenger法、Ozawa法和Crane法计算了固化反应表观活化能和反应级数,芴基苯并嗯嗪的表观活化能在122～174 kJ/mol之间,反应级数近似为一级。芳香胺基、饱和脂肪胺基以及不饱和脂肪胺基苯并噁嗪单体的热性能研究结果表明,芴基聚苯并噁嗪树脂优异的热稳定性与芴基结构、胺取代基结构和聚合物网络结构有关。庞大的芴基引入聚苯并噁嗪结构中使得聚合物的刚性提高,聚合物链段的内旋转和热运动受到限制,极大地提高了芴基聚苯并噁嗪树脂的玻璃化转变温度和内在热稳定性；分子内和分子问氢键使聚合物链的堆积更加紧密,阻碍了聚合物链段的运动,提高了聚合物的刚性,而更多的分子间氢键数量有助于玻璃化转变温度的提高,分子内氢键对聚合物的耐热性起到重要作用；芴基苯并噁嗪结构中含有可聚合基团时,提高了聚合物的交联密度,有助于提高聚合物的初始热分解温度和残炭率,玻璃化转变温度显著提高；具有活性交联位的芳香胺基聚苯并噁嗪的交联密度有所增大,促进玻璃化转变温度的提高；脂肪族分子链含柔性侧基,使得分子间距离增大,内增塑作用增强,相互作用减弱,且随着碳链的增加,玻璃化转变温度和热稳定性显著下降,显著低于芳香胺基聚苯并噁嗪；炔丙胺基聚苯并噁嗪具有最高的热稳定性。环氧树脂对噁嗪环的开环反应起到催化作用,从而降低了聚合反应温度,自身也参与交联反应,使得聚合物分子内增塑作用增强,聚合物的刚性和堆积密度降低,Tg下降,热稳定性有所提高,残炭率的降低主要与苯并噁嗪的加入量有关。共混树脂的热分解过程为单一热分解机理,环氧树脂的引入对聚合物的热稳定性和加工性能有一定改善。EMI(2-乙基-4-甲基咪唑)对芴基苯并噁嗪具有催化开环聚合作用,共聚物的热稳定性和残炭率高于相应的纯树脂以及芴基苯并噁嗪/E-51共混树脂,芴基苯并噁嗪树脂-环氧树脂-EMI三元共混树脂聚合反应经历3个阶段,EMI不仅对共混树脂起到催化作用,降低固化温度,还使聚苯并噁嗪和环氧树脂固化物形成均相共聚物,提高了共混树脂的交联密度和相容性,固化树脂无相分离现象,综合性能优于相应的纯树脂和同样比例未加EMI的共混树脂体系,有望在高性能树脂基体、电子封装、层压材料、绝缘材料以及阻燃材料等领域得到应用。更多还原

【Abstract】 Polybenzoxazines, as a class of thermosetting phenolic resins formed by the thermal ring-opening of the corresponding benzoxazines monomers without any catalyst, have demonstrated various attractive properties such as high thermal stability, high char yields, high glass transition temperature (Tg), near-zero volumetric change upon curing, good mechanical and dielectric properties, low water absorption, and low flammability. These unique characteristics make the polybenzoxazines a better candidate over epoxies and traditional phenolic resins in the electronics, aerospace, and other industries.9,9-bis(4-hydroxyphenyl)-fluorene (BHPF) was synthesized from phenol and fluorenone as raw materials in the presence of liquid acids and solid acids as catalyst by microwave-assisted synthesis technology. A series of difunctional fluorene-based benzoxazine monomers were synthesized from the reaction of BHPF with formaldehyde and primary amines. Their chemical structures were confirmed by FTIR, 1H and 13C NMR analyses. The polymerization behaviors, curing dynamics, and network structure of the precursors and polymers were monitored by differential scanning calorimetry (DSC) and FT-IR. The mechanical performance and thermal properties of neat polybenzoxazines and blending resins were evaluated with DSC, Dynamic Mechanical Analyzer (DMA) and Thermogravimetric Analyzer (TGA).The experimental results show that the yields of BHPF was more than 83% under the optimal process conditions that the molar ratio of phenol to fluorenone was 8 to 1, the mass percentage of catalysts including sulfuric acid and methylsulphonic acid was 2-5% of the total reactants, reaction temperature was 45-55℃and reaction time was 30 min. When solid acids such as phosphotungstic acid and strongly acid cation exchange resin were used as catalyst, the yields of BHPF was more than 70% under the optimal process conditions that the mass percentage of catalysts was 6-9%, reaction temperature was 130℃and reaction time was 90 min. The melting point of BHPF was 223-224℃. The synthetic method using strongly acid cation exchange resin as catalyst will be the direction of development in the futrue.New fluorene-based bezoxazine monomers was synthesized under the optimal process conditions that the molar ratio of BHPF, formaldehyde, and primary amine including aniline, o-toluidine, m-toluidine,p-toluidine,3,5-di-methyl-toluidine, n-butylamine, n-octylamine, cyclohexylamine, allylamine, and propargyl amine was 1:4:2, the mixtures of dioxane and anhydrous ethanol, which the volume ratio is 1:1, were used as solvent, the addition reaction temperature between formaldehyde and primary amine was less than 5℃, the addition reaction time was 2 h, the ring-closing reaction temperature between addition product and bisphenol fluorene was 90-100℃, the ring-closing reaction time was 5-7 h. The yields of fluorene-based bezoxazine monomers were 50-63%.The fluorene based polybenzoxazines show the typical curing characteristic of oxazine ring-opening for difunctional benzoxazines centred at 231-250℃. The chain segments of polymers consist of phenolic Mannich bridge network, arylamine Mannich bridge, arylamine methylene bridge, intramolecular hydrogen bonding, and intermolecular hydrogen bonding. The pendant arylamine rings activated in the para position can undergo an aminomethylation reaction during the polymerization. The curing kinetics and curing craft of fluorene-based bezoxazines was investigated using non-isothermal DSC. and determined by Kissinger, Ozawa and Crane methods. The activation energy of fluorene-based bezoxazines calculated by Kissinger and Ozawa method is 122-174 kJ/mol. The reaction order is approximate 1. The step curing profil of fluorene-based bezoxazines is as follows:170-180℃/2 h,200-220℃/3 h,240-250℃/2 h.The introduction of bulky fluorene moieties into the benzoxazine chains must arise from the higher rigidity of fluorene skeleton in the chain backbone, which restrains the internal rotations and thermal motion of polymer segments. As a result, the Tg values of fluorene-based polybenzoxazines are higher than those of the relative bisphenol A-based polybenzoxazines. In addition, the tighter packing of the polymer chains due to the strong intermolecular and intramolecular hydrogen bonding has significant influence on the Tg of the fluorene containing polybenzoxazines, which confines segmental mobility and contributes to a rigidity of the polymer chains. The aromatic amine-fluorene-based polybenzoxazines are more chemically cross-linked and have tighter packing and higher crosslinking density than the linear aliphatic aminebased polybenzoxazines. The polybenzoxazines containing polymerized groups possess higher crosslinking density. Therefore, the Tg values of polymers increase dramatically. The Tg values of aliphatic amine-fluorene-based polybenzoxazines containing flexible pendant groups significantly decrease as the increases of the length of aliphatic groups.The thermal stability of fluorene-based polybenzoxazines is connected with the fluorenyl structure, substituent structure of amines, and network structure of polymers. The introduction of rigid fluorene skeleton with bulky pendent Cardo moieties into benzoxazine monomers can improve the inherent thermal stability of the thermosets dramatically. Furthermore, the intramolecular hydrogen bonding of the polymer chains, while intermolecular hydrogen bonds typically weaken significantly above Tg, has a tendency to stabilize the molecule. These may contribute to the improvement of thermal stability of the fluorene based polybenzoxazines. The introduction of polymerized groups such as allyl and propargyl into benzoxazine chains can improve the crosslinking density of polymers, and be conductive to the improvement of initial thermo-decomposing temperature and char yield. The thermal stability of propargyl amine-fluorene-based polybenzoxazine is the highest in all fluorene-based polybenzoxazines. The polybenzoxazines derived from aromatic amines attributed to the high aromatic content have the better thermal stability than those derived from aliphatic amines.Epoxy resins can catalyze the ring-opening of benzoxazines to reduce polymerizing temperature, and involve in the crosslinking reaction. The results lead to enhancement of the internal plasticization of polymer molecular, decrease of the rigidity and packing of the polymer chains, drop of the Tg values, and improvement of thermal stability. The decrease of char yields is relative to the dosages of benzoxazines. There is a single decomposition mechanism for the blending resins of benzoxazines/epoxy resins. The introduction of epoxy resins into polybenzoxazine system can improve the thermal stability and processability of polymers at a certain extent.2-ethyl-4-methyl-imidazole (EMI) can catalyze the ring-opening of benzoxazines. The thermal stability and char yields of copolymers consisting of benzoxazines and EMI are higher than those of the neat polybenzoxazines and blending resins of fluorene-based benzoxazines and E-51 epoxy resins. The polymerization resction for ternary blending resins, containing fluorene-based benzoxazines, E-51 epoxy resins, and EMI, undergos three stages. EMI has profit to the formation of homogeneous copolymers and the improvement of crosslinking density and compatibility of blending resins in the ternary system. There is no phenomena of phase separation. The comprehensive performances of the ternary blending resins are better than those of neat corresponding benzoxazines and blending resins of fluorene-based benzoxazines and E-51 epoxy resins without EMI, which may be a good candidate for high performance composite matrices, electronic encapsulation materials, laminate materials, insulation materials and fire resistant materials, etc.更多还原