【作者】 吴雄；

【导师】 刘承美；

【作者基本信息】 华中科技大学 ， 高分子化学与物理， 2011， 博士

【摘要】 苯并噁嗪是在酚醛树脂的基础上发展的一类新型热固型树脂,它具备传统酚醛树脂所有优点,如优异的机械性能,良好的化学稳定性、样品尺寸稳定性,较高化学电阻率、热稳定性,并且相应单体热固化过程近零收缩率,固化后的样品吸水率低,阻燃性高。此外,苯并噁嗪单体来源广,且单体分子结构设计及合成操作简单,可用来制备满足不同性能需求的功能性苯并噁嗪树脂,因此它可替代传统酚醛树脂,广泛应用于高科技领域。而环三磷腈是一种典型的由N和P原子交替组成的平面非离域六元环无机化合物,每个P原子上可以连接两个基团。由于无机磷腈环的生物相容性、耐热性、结构稳定性、立体多反应点和阻燃性,使得相应的衍生物具有广泛的应用前景。通过化学键将功能性的苯并噁嗪基团和环三磷腈环结合起来,合成了环三磷腈类苯并噁嗪单体和包含苯并嗯嗪结构的预聚物,并研究其热固化交联性质及固化后材料的性能。此外,相应的环三磷腈苯并噁嗪单体改性传统的苯并噁嗪或环氧,提高了相应共聚物的耐热性和机械性能。本文通过分子设计,在无机环三磷腈上引入不同数目的有机苯并噁嗪基团和联苯基团,得到了分别含有二个(BBOz)、四个(TBOz)和六个(HBOz)苯并噁嗪基团的功能性单体。通过1H,13C,31P-NMR和元素分析表征了相应单体的结构。通过变温红外(FT-IR)和差示扫描量热仪(DSC)研究了相应单体的热开环聚合行为。通过热失重仪(TGA)和动态热机械仪(DMA)分别对目标材料的热稳定性和机械性能进行分析。同时场发扫描电镜(Fs-SEM)也用来观察目标材料的断面形貌,并研究了相应热固性树脂的微观结构。由于BBOz、TBOz和HBOz单体的不同结构,相应单体表现出了不同的聚合活性。在相同条件下,含有六个苯并噁嗪基团的HBOz单体最先发生开环聚合反应,并且最先聚合完全；而含有二个苯并噁嗪基团及二个联苯基团的BBOz单体最后发生聚合反应,也是最难被聚合完全的单体。同样,单体的不同结构,也导致相应的聚苯并噁嗪表现出不同的热稳定性、机械性能和抗湿性。由四个苯并噁嗪基团和一个联苯基团组成的单体(TBOz)聚合所得聚苯并噁嗪(PTBOz)表现出了最好的热稳定性和机械性能,其起始分解温度约为440℃,850℃时的残焦量近70%,并且相应的聚合物的玻璃化温度(Tg)为254℃。山HBOz聚合所得的聚苯并噁嗪PHBOz的热稳定性和机械性能最差,其起始分解温度和高温残焦量分别为400℃和66.9%,对应的Tg只有152℃。三种环三磷腈聚苯并噁嗪树脂的平衡吸湿量都低于1wt%,PBBOz拥有最低吸湿率,而PHBOz的吸湿率最高。在环三磷腈二胺的基础上,我们也合成了主链上同时含有苯并噁嗪基团和环磷腈的线性低聚物。相比传统一步法(方法A),分步法(方法B)合成的低聚物的分子量会高出近一倍。但用方法B合成的苯并噁嗪预聚物的起始聚合温度、最大放热峰温度和聚合放热焓都比方法A合成的苯并噁嗪低聚物要高出很多。热稳定性测试结果显示：无论方法A或B,最终交联后的聚合物都表现出了优异的热稳定性。HBOz、TBOz和BBOz单体分别与传统的苯并噁嗪单体(Pa, Ba)共聚,改善了相应共混单体的热固化条件,使得相应的混合单体在较低的温度下便可发生开环共聚合反应。共聚物的热稳定和机械性能相比传统的聚苯并噁嗪树脂有了明显的提高。添加20wt%环三磷腈类苯并噁嗪单体到Pa或Ba单体中,共聚物的起始分解温度提高约30℃,高温残焦量最高可增加60%,相应共聚物Tg也大幅度被提高。HBOz、TBOz和BBOz单体与环氧E44共聚物高温时的残焦量和Tg相对于E44环氧树脂都明显提高,高温残焦量被提高了至少500%,而对应的T。提高至少10℃但由于环氧树脂与苯并噁嗪树脂间存在微观相分离结构,对应共聚物的起始分解温度会随苯并噁嗪含量增加而降低,同时对应共聚物的初始储能模量无明显变化。更多还原

【Abstract】 Benzoxazine rensins are developed class of high-performance thermosetting resins instead of traditional phenolic-formaldehyde resin in high-tech field. These thermosetting resins not only possess all the advantages of traditional phenolic resins such as excellent mechanical, thermal properties, dimentional stability and high chemical resistivity, but also have unique advantages of near-zero shrinkage upon curing, thermal and flame retardant, low water absorption and remarkable molecular design flexibility. Besides, corresponding monomers can be conveniently designed and generated, so the funcatioanal polybenzoxazines can be easily gained and satisfied for different applications. On the other hand, cyclotriphosphazene (CP) derivatives are a typical class of organic-inorganic compounds with a planar non-delocalized cyclic ring consisting of alternating N and P atoms. Six functional groups can be attached onto a CP ring. Due to the versatility of cyclotriphosphazene chemistry, high stability and biocompatibility of the CP ring allows for a wide range of functional groups to be attached onto CP, and corresponding CP-based derivatives can be applied in many fields. So that, combining the CP and benzoxazine together by chemical bonding is an interesting method to obtain high-performance benzoxazine monomer and polybenzoxazine. Similarly, synthesizing a linear polymer precursor with benzoxazine moieties and CP in main chain is also a good way to get high-performance polybenzoxazine. Besides, the performances of thermal stability and mechanic property for traditional benzoxazine and epoxy resins can also be improved by co-polymerizing with CP-base benzoxazines.A series of organic-inorganic hybrid benzoxazine monomers based on cyclotriphosphazene (CP) have been synthesized, which possess variable number of organic benzoxazine moieties and biphenyl groups distributed on the inorganic ring of cyclotriphosphazene. The structures of the monomers were confirmed by 1H NMR,13C NMR,31P NMR and elemental analysis. The ring-opening polymerization behaviors of the new benzoxazine monomers were investigated by Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). The thermal property and mechanic performance of the thermoset polymer were also evaluated by thermal gravimetric analyzer (TGA) and DMA, respectively. Besides, the fracture surfaces of co-polybenzoxazines samples were also observed by scanning electron.The polymerization activity of the monomers relied on the number of benzoxazine moiety and biphenyl group, the monomers with six benzoxazine moieties (HBOz) was easier to polymerize than the others, while the monomer with two benzoxazine moieties and two biphenyl groups (BBOz) was the hardest one to polymerize. Due to the high crosslinking nature containing rigid and stable inorganic CP ring and biphenyl groups in the networks, the polybenzoxazines resulting from the as-prepared monomers showed different thermal stability, mechanic property and humidity resistance. The polybenzoxazine PTBOz resulting from TBOz which contain four benzoxazine moieties and one biphenyl group showed the highest thermal stability and glass transition temperature (Tg). The onset decomposition temperature of PTBOz was about 440℃, the char yield at 850℃(Yc) was 69.6%, and corresponding Tg was as high as 254℃. While PHBOz which polymerized from HBOz got the lowest thermal stability and Tg, it started to be thermal degradation at about 400℃, and its Yc and Tg were 66.9% and 152℃, respectively. Meanwhile, PBBOz exhibited the highest humidity resistance, and PHBOz got the lowest, but all of the polybenzoxazines showed high humidity resistance, and the balance water uptakes were lower than 1wt%.Based on the CP-diamine, two routes were attempted to synthesize the linear polymer precursor with benzoxazine moieties and CP rings in the main chain. Comparing to traditional method A, higher molecular weight can be gained by method B, and the molecular weight was about two times higher than that synthesized by method A. However, the polymer precursor synthesized with method A could undergo ring-opening polymerization at lower temperature than that using method B. No matter what, both the polybenzoxazines resulting from the polymer precursors showed excellent thermal stability.The performances of traditional benzoxazine were improved by co-polymerizing with CP-based benzoxazines. The CP-based benzoxazines could decrease the polymerization temperature of traditional benzoxazines. Due to the different dimensional crosslinking structures of the CP-based benzoxazines under ring-opening polymerization, the CP-based benzoxazines showed different degree of improvement on the thermal stability and mechanic properties for the co-polybenzoxazines. However, the Yc of all co-polybenzoxazines was improved at least 36%, even higher to 60% for some samples after adding 20wt% CP-based benzoxazines. What’s more, the Tg of the co-polybenzoxazine raised at least 10℃by adding 20wt% CP-based benzoxazines.Similarly, the Yc and Tg of epoxy/CP-based benzoxazine co-polymers were also improved. The Yc of the co-polymer was improved at least 500%, and corresponding Tg was improved about 10℃. However, there was an appearance of microphase separation between epoxy resin and CP-based polybenzoxazine, the onset decomposition temperature decreased with the increasing content of CP-based benzoxazines; Meantime, there was little change to the storage modulus of the epoxy co-polymerizing with CP-based benzoxazines.更多还原