同分异构双酚F型苯并噁嗪的研究

分别以同分异构体混合型双酚F和对位双酚F为原料,通过溶液法制备出双酚F型苯并噁嗪。利用傅里叶变换红外光谱(FTIR)、核磁共振氢谱(1H NMR)、凝胶渗透色谱法(GPC)、示差扫描量热法(DSC)、动态热力学分析(DMA)和热重分析(TGA)对2种双酚F型苯并噁嗪中间体的结构、固化行为及其固化物的性能进行了研究。结果表明双酚F中的同分异构体对苯并噁嗪的性能存在影响。对位双酚F型苯并噁嗪的成环率、固化物耐热性和热稳定性均高于同分异构混合双酚F型苯并噁嗪。     

含烯炔基苯并噁嗪的制备与分析

本文以二氧六环为溶剂、以烯丙基双酚A、间氨基苯乙炔和甲醛为原料,合成了含烯炔结构的苯并噁嗪化合物.采用FTIR、1H NMR方法确定了苯并噁嗪化合物的化学结构.该噁嗪化合物室温下为液态,对噁嗪化合物固化产物进行了动态力学分析(DMA),结果表明,制备的噁嗪化合物固化物具有较高的使用温度,玻璃化转变温度高达367.61℃,有望作为高性能复合材料树脂基体使用.     

苯并噁嗪/含磷环氧/双氰胺三元体系阻燃性能的研究

分别制备了不同配比的双酚A型苯并噁嗪/含磷环氧(B/E)二元体系和双酚A型苯并噁嗪/含磷环氧/双氰胺(B/E/D)三元体系浇铸体及玻璃纤维层压板。采用垂直燃烧试验和锥形量热试验两种方法表征了样品的阻燃性能,并通过示差扫描量热(DSC)、热失重(TGA)和热重红外联用(TG-FTIR)分析了影响体系阻燃性能差异的原因。结果表明:B/E/D三元体系的阻燃性明显低于B/E二元体系,双氰胺的加入使得三元体系的热稳定性降低,300℃以下的热分解加剧并释放出更多的气体,及800℃残碳率降低。双氰胺结构中的氮元素未能对提高树脂体系的阻燃性能发挥积极作用。     

纳米炭粉改性苯并噁嗪树脂烧蚀性能研究

为进一步提高苯并噁嗪树脂的烧蚀性能,采用纳米炭粉对其进行了改性研究。采用透射电镜(TEM)和场发射电子显微镜(SEI)观察了纳米炭粉在苯并噁嗪树脂的中的分散状态;通过热失重分析研究了纳米炭粉质量分数对苯并噁嗪树脂残炭率的影响并测试了烧蚀性能;同时采用X-射线衍射法(XRD)对炭层结构进行了分析。结果表明,质量分数为10%纳米炭粉的改性苯并噁嗪800℃残炭率可达到63.6%,该体系700℃炭化后的压缩强度为纯树脂的3.8倍。改性后的苯并噁嗪树脂炭化层结构致密,裂纹小,石墨化度与炭结构的有序度大大提升,最终使树脂的耐烧蚀性能与抗热震性获得改善。     

氢氧化镁改性苯并噁嗪树脂的热性能

本文应用示差量热扫描法(DSC)、动态热机械分析(DMA)和热失重(TGA)对氢氧化镁改性苯并噁嗪树脂的固化行为和热性能进行了研究。结果表明,氢氧化镁的加入对苯并噁嗪树脂的固化反应基本没有影响。DMA测试结果表明,氢氧化镁的加入使聚苯并噁嗪体系的玻璃化转变温度略微有所增高,室温下的储能模量略有增加。TGA测试结果表明,氢氧化镁的加入使聚苯并噁嗪体系的热稳定性提高,起始分解温度和800℃残重均有所提高。     

丁胺-芴基苯并噁嗪/环氧共混树脂的性能研究

以双酚芴、正丁胺和多聚甲醛为原料,二氧六环为溶剂,通过Mannich缩合反应,合成了高纯度丁胺-芴基苯并噁嗪单体（BF-n-b）。以差式扫描量热仪（DSC）研究了苯并噁嗪单体/E-51环氧共混树脂的固化行为,通过动态热机械分析（DMA）和热重分析（TGA）研究了共混树脂的热机械和热稳定性能。结果表明,采用改进的制备方法简化了苯并噁嗪单体的合成过程,单体收率和纯度显著提高;苯并噁嗪/环氧共聚物的玻璃化转变温度（Tg）达到165~178℃,初始热分解温度（热失重5%）达312~342℃,800℃时残碳率最高达22.4%。     

含磷烯丙基胺型苯并噁嗪的合成与表征

以含磷中间体(BPPP),烯丙基胺,甲醛溶液为原料合成了—种含磷烯丙基胺型苯并噁嗪,并采用核磁共振氢谱(1H-NMR)、傅里叶红外光谱(FTIR)、差示量热扫描仪(DSC)和热失重分析仪(TGA)对其化学结构、固化行为及热稳定性进行了表征.结果表明,含磷烯丙基胺型苯并噁嗪的固化温度为216℃.固化产物的5％和10％热失重温度分别为269和315℃.800℃时的残炭高达51％,表明聚苯并噁嗪具有良好的热稳定性.     

含双DOPO的双酚A-单苯并嗪合成、表征及其与环氧树脂共聚物的阻燃性能

以含双DOPO-双酚A、苯胺和多聚甲醛为原料,合成了含双DOPO的双酚A-单苯并嗪(1DD)。采用红外、核磁(氢谱核磁和碳谱核磁)等分析手段对1DD的化学结构进行了表征;采用DSC对1DD的固化特性进行研究,使用TG分析了所得聚苯并嗪的热稳定性。再将1DD与环氧树脂以0.5/1的质量比进行共混,按照一定的程序进行升温固化,得到共聚物P1DD-ER。采用UL94垂直燃烧实验、极限氧指数仪(LOI)测试了共聚物的阻燃性能。结果表明:含双DOPO的双酚A-单苯并嗪树脂的起始熔点约为185℃,在222℃处有一个很明显的放热峰。固化后的树脂从348℃开始分解,在463℃分解速率达到最快,在800℃时的残碳率为35.78%。制备的苯并嗪可以用作环氧树脂的固化剂,且其共聚物具有很好的阻燃性能,LOI可以达到37,UL94等级为V-0。     

苯并噁嗪树脂改性环氧树脂胶黏剂的阻燃性能

以双酚A型环氧树脂E51为基体,苯并噁嗪树脂为改性剂,4,4-二氨基二苯甲烷为固化剂,并加入少量无机填料,制备了苯并噁嗪树脂改性环氧树脂胶黏剂,研究了其耐热性能与阻燃性能。结果表明：苯并噁嗪树脂改性的环氧树脂胶黏剂耐热性能和阻燃性能较好,在氮气气氛下质量损失10%时的温度由390.75℃提高到401.12℃,800℃时的残炭率为21.988%(w),175℃的拉伸剪切强度达到19.4 MPa,极限氧指数达到31.6%。     

含双DOPO的双酚A-单苯并(口恶)嗪合成、表征及其与环氧树脂共聚物的阻燃性能

以含双DOPO-双酚A、苯胺和多聚甲醛为原料,合成了含双DOPO的双酚A-单苯并(口恶)嗪(1DD)。采用红外、核磁(氢谱核磁和碳谱核磁)等分析手段对1DD的化学结构进行了表征;采用DSC对1DD的固化特性进行研究,使用TG分析了所得聚苯并(口恶)嗪的热稳定性。再将1DD与环氧树脂以0.5/1的质量比进行共混,按照一定的程序进行升温固化,得到共聚物P1DD-ER。采用UL94垂直燃烧实验、极限氧指数仪(LOI)测试了共聚物的阻燃性能。结果表明:含双DOPO的双酚A-单苯并(口恶)嗪树脂的起始熔点约为185℃,在222℃处有一个很明显的放热峰。固化后的树脂从348℃开始分解,在463℃分解速率达到最快,在800℃时的残碳率为35.78%。制备的苯并(口恶)嗪可以用作环氧树脂的固化剂,且其共聚物具有很好的阻燃性能,LOI可以达到37,UL94等级为V-0。     

Influence of PEPA-containing polyether structure on fire protection of transparent fire-resistant coatings

Three kinds of novel PEPA-containing polyether flame retardants were synthesized by 1-oxo-4-hydroxymethyl-2,6,7-trioxa-l-phosphabicyclo [2.2.2] octane (PEPA), phosphorus oxychloride (POCl₃), and polyether with different structures (PEG, PPG, and PTMG). Their structures were confirmed by ¹H nuclear magnetic resonance (¹H NMR) and Fourier transform infrared spectroscopy (FTIR). The solubility test showed that PEPA modified by polyethylene glycol (PEG) and polypropylene glycol (PPG) had better water solubility than that modified by poly(tetrahydrofuran) (PTMG). The decomposition process of PEPA-containing polyether flame retardants (PCPE) was studied by thermogravimetric analysis (TG) and derivative thermogravimetry. A possible mechanism was proposed to analyze the influence of polyether structure on the thermal degradation process of PCPEs. Afterward, the PEPA-containing polyether flame retardants were mixed with melamine formaldehyde resin to prepare the transparent fire-resistant coatings. The influences of polyether structure on the properties of the coatings were investigated in detail by fire protection test, TG, FTIR, X-ray photoelectron spectroscopy (XPS), and scanning electron microscope. It was found that the fire protection of the coating and foam structure of char layer were significantly improved when the number of carbon atoms in a unit of polyether chain was less. TG results showed that the chain unit of polyether with less carbon atom number could increase the residue weights of the coatings. FTIR and XPS result illustrated that the char layers were mainly composed of aromatic rings and phosphorus oxide, and the antioxidation and char-forming ability of coatings were enhanced effectively with the decrease in the number of carbon atoms in a unit of polyether chain.     

Synthesis and properties of a novel bio‐based benzoxazine resin with excellent low‐temperature curing ability

A novel bio‐based benzoxazine resin (diphenolic acid/furfurylamine benzoxazine resin, PDPA‐F‐Boz) was prepared by using bio‐based diphenolic acid, furfurylamine and paraformaldehyde as raw materials. The structure of DPA‐F‐Boz monomer was characterized by Fourier transform infrared spectroscopy, ¹H NMR and ¹³C NMR, and then its curing reaction and the thermal stability of the cured PDPA‐F‐Boz were analyzed. Compared with the traditional fossil‐based benzoxazine (bisphenol A/aniline benzoxazine, BPA‐A‐Boz) and the bio‐based benzoxazine (diphenolic acid/aniline benzoxazine, DPA‐A‐Boz), DPA‐F‐Boz monomer showed the lowest curing temperature, and PDPA‐F‐Boz had the highest residual char ratio at 800 °C and the lowest degradation rate at the peak temperature. Meanwhile, the total heat release, peak heat release rate and heat release capacity of PDPA‐F‐Boz were much lower than those of PBPA‐A‐Boz and PDPA‐A‐Boz. Thus, PDPA‐F‐Boz showed excellent low‐temperature curing ability and thermal stability. © 2019 Society of Chemical Industry     

Main-chain benzoxazine oligomers: A new approach for resin transfer moldable neat benzoxazines for high performance applications

A new approach has been developed to enhance the processability of main-chain benzoxazine polymers by synthesizing benzoxazine main-chain oligomers that are low in viscosity while maintaining the major part of the advantages of main-chain type polybenzoxazines. A series of main-chain benzoxazine oligomers have been synthesized using bisphenol-F isomers. The structure of the oligomers has been characterized by nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FT-IR). The molecular weight has been evaluated using size exclusion chromatography (SEC). For a viscosity study, a mixture of benzoxazine monomers derived from the same bisphenol-F isomers has been used as control and a reactive diluent to control the viscosity.     

Highly branched benzoxazine monomer based on cyclotriphosphazene: Synthesis and properties of the monomer and polybenzoxazines

A hyperbranched organic-inorganic hybrid benzoxazine monomer based on cyclotriphosphazene (CP) has been synthesized, which possesses six organic benzoxazine moieties distributed on the inorganic ring of CP. The high molecular weight (1491 g/mol) monomer showed excellent solubility in common organic solvents. Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) were used to study the thermal ring-opening polymerization reaction of the novel benzoxazine monomer. FT-IR spectrum implied that the characteristic absorption peaks of the benzoxazine ring disappeared completely after curing at 240 °C for 1 h, which illustrated that the completion of polymerization reaction. DSC plots indicated that the melting point of the new monomer was 77 °C and an exothermic peak was 225 °C owing to the ring-opening polymerization of the monomer. Due to its highly steric crosslinking structure with rigid and thermal stable inorganic CP as the core, the polybenzoxazine based on the new monomer showed excellent thermal stability and mechanic properties. The char yield of the polymer at 850 °C was 66.9% in nitrogen, and the T_g of the polybenzoxazine was 152 °C.     

Synthesis, characterization and thermally activated curing of polysulfones with benzoxazine end groups

Polysulfones with benzoxazine end groups (PSU-B-a) were obtained using monomer synthesis method from the phenol terminated polysulfone (PSU-OH), aniline and paraformaldehyde as starting materials. For this purpose, the precursor PSU-OHs with different molecular weights were prepared by condensation of bisphenol-A and bis(p-chlorophenyl) sulfone in presence of potassium carbonate. The structure of the polymers before and after functionalization was confirmed by proton nuclear magnetic resonance spectroscopy (¹H NMR) and Fourier transform infrared spectroscopy (FT-IR). Thermally activated crosslinking behavior of these polymers was investigated by differential scanning calorimetry (DSC). Thermal and tensile properties of the crosslinked polymers obtained from PSU-B-a alone or with low molar mass benzoxazine (P-a) were studied by thermal gravimetric analysis (TGA) and dynamic mechanical analysis (DMA).     

Synthesis of linear polymers containing benzoxazine moieties in the main chain with high molecular design versatility via click reaction

Linear polymers with benzoxazine rings in the main chain have been synthesized applying click chemistry approach. These polymers possess molecular weights significantly higher than the benzoxazine polymers which have been chain extended via Mannich reaction. The number average molecular weight is estimated from size exclusion chromatography (SEC) to be between 20,000 and 40,000 Da. The structure of the polymers is confirmed by ¹H and ¹³C nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FTIR). Differential scanning calorimetry (DSC) is used to study crosslinking behavior of the polymers. The nature of the low temperature exotherm DSC peak observed in this work and the previous work of other authors is studied by model reactions. It is due to thermal coupling of the residual propargyl and azide end groups in the absence of active catalyst. In addition, a novel diazide-functional benzoxazine monomer has been prepared, showing a tremendous flexibility for applying click reaction to obtain various polymer architectures. Three types of polymers have been prepared from dipropargyl- and diazide-functional benzoxazine monomers. These polymers have been characterized by dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA).     

Preparation of a liquid benzoxazine based on cardanol and the thermal stability of its graphene oxide composites

A novel liquid benzoxazine was synthesized by Mannich reaction of cardanol, paraformaldehyde, and allylamine. The benzoxazine structure was characterized by ¹H‐NMR and FTIR. The liquid benzoxazine could dissolve easily in many solvents. The curing behavior of the benzoxazine was characterized by differential scanning calorimetry (DSC) and its curing temperature was about 233°C. A benzoxazine‐functional silane coupling agent (BFSca) was synthesized with paraformaldehyde, phenolphthalein, and aminopropyltriethoxysilane. Graphene oxide (GO) was also made via improved Hummer's method. Then benzoxazine/GO composites were prepared using BFSca by solution blending and the curing behaviors of the composites were also characterized by IR, DSC, and thermogravimetric analysis. The minimum curing temperature and the highest 5% weight loss temperature for the composites was, respectively, 185 and 399.8°C. The SEM images of benzoxazine/GO composites demonstrated that BFSca had improved the dispersion of GO in the benzoxazine and also enhanced the thermal decomposition temperature of the composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40353.     

Novel benzoxazine monomer containing diacetylene linkage: An approach to benzoxazine thermosets with low polymerization temperature without added initiators or catalysts

A novel benzoxazine monomer containing diacetylene linkage has been synthesized by applying an oxidative coupling approach. The structure is confirmed by ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. Differential scanning calorimetry (DSC) is used to study crosslinking behavior of synthesized material. The benzoxazine monomer exhibits unexpectedly low exothermic peak with the onset around 140 °C, which is significantly lower than conventional benzoxazines or benzoxazines containing additional crosslinking sites. Benzoxazine polymerization at this low temperature is also confirmed by FTIR. The initial model studies are made in order to understand this phenomenon and preliminary explanation is given. High thermal stability of the crosslinked thermoset was confirmed by thermogravimetric analysis (TGA).     

Well-defined organic-inorganic hybrid benzoxazine monomers based on cyclotriphosphazene: Synthesis, properties of the monomers and polybenzoxazines

Well-defined organic-inorganic hybrid benzoxazine monomers based on cyclotriphosphazene (CP) cores have been synthesized. Theses monomers possessed controllable number of organic benzoxazine moieties and biphenyl groups distributed on the inorganic ring of CP. Corresponding ring-opening polymerization under heat led to highly cross-linked polymers with different number of crosslinking sites. The ring-opening polymerization behaviors of the new benzoxazine monomers were investigated by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMA). The results indicated that the polymerization activity of the monomers depended on the number of benzoxazine moiety of corresponding monomers. Those monomers with more benzoxazine moieties resulted in higher polymerization rate. Due to the high crosslinking nature with rigid and stable inorganic CP ring and biphenyl groups in the networks, the resulted polybenzoxazines from the monomers showed excellent thermal stability, mechanic property and humidity resistance.