硅氧烷预聚体改性热塑性酚醛树脂的交联结构及其力学性能

通过不同预聚程度的环氧化硅氧烷（ES）与酚醛树脂共固化及固化物理状态的调控,构建不同拓扑结构的交联网络,探讨了不同预聚程度的硅氧烷预聚体（PES）改性热塑性酚醛树脂（NR-PES）交联网络的调控及其强韧化的构建方法。首先,合成了一种不同预聚程度的环氧化硅氧烷（PES）,通过DSC和流变分析,明确了NR-PES的固化反应和物理状态特征,在此基础上,确定了不同交联结构NR-PES的制备方法。接着,采用DMA、TGA、力学测试研究了PES的预聚程度对NR-PES交联网络和性能的影响规律。结果表明,当PES预聚程度较低时,NR-PES的交联密度较低,导致其热稳定性和弯曲强度较低;随着PES预聚程度的增加,NR-PES的交联密度不断增加,其热稳定性、弯曲强度随之增加,但K_IC不断降低。特别是,PES的预聚程度为30%时,2-NR-PES展现出优异的热稳定性、弯曲强度和断裂韧性,残炭率C_800℃为53.43%,弯曲强度为20.51 MPa,K_IC为0.389 MPa·m^1/2。此外,当PES预聚程度过高时,NR-PES的热稳定性、弯曲强度和断裂韧性显著降低。     

Ce-Y(Ca)-TZP陶瓷及Ce-TZP/Al2O3复相陶瓷的研究与应用进展

氧化铈稳定的四方氧化锆多晶陶瓷(Ce-TZP)具有良好的抗低温老化性和很高的断裂韧性(K_IC>20 MPa·m^1/2),但是弯曲强度较低(500 MPa左右)。如何在保留Ce-TZP陶瓷的抗低温老化性和高断裂韧性的同时,提高其强度,是本领域研究人员共同关心的问题。大量研究表明,通过添加其他固溶离子(如Y³⁺)达到共稳定效果和引入第二相(如Al₂O₃)获得细晶Ce-TZP基的复相陶瓷,可以显著提高材料的断裂强度,综合改善其力学性能。本文对CeO₂与其他氧化物共稳定的ZrO₂陶瓷及Ce-TZP/Al₂O₃复相陶瓷的研究进展进行了综述,并以义齿种植和增材制造为例介绍了其应用现状。     

聚硼硅氮烷固化氰酸酯基耐高温胶粘剂的制备与性能研究

以氰酸酯为基胶,聚硼硅氮烷前驱体为固化剂,复配相应的填料,制备了氰酸酯基耐高温胶粘剂。研究了聚硼硅氮烷用量对氰酸酯固化特性、固化产物的结构变化及固化物热稳定性的影响。研究结果表明：与传统的氰酸酯胶粘剂相比,聚硼硅氮烷催化氰酸酯的固化温度降低了50～100℃;聚硼硅氮烷可以催化氰酸酯在150℃低温固化,20份聚硼硅氮烷催化氰酸酯固化物T_5%最高达到476.3℃。以此为基础制备的耐高温胶粘剂的室温粘接强度最高为16 MPa,400℃老化3 h后粘接强度仍达到12 MPa,表明该胶粘剂具有较好的粘接性能和耐老化性能。本研究制备的胶粘剂凭借较低的固化温度、良好的粘接性能和耐温性,有望用于航空、航天和电子等行业。     

酚醛树脂/碳化硼/聚硼氮烷复合物的固化行为及其热解性能

酚醛树脂作为一种热固性树脂基体具有广泛的应用。为了满足其作为高性能树脂基体在苛刻条件（耐高温和抗氧化）下的使用,进一步提高酚醛树脂的耐热性能并兼顾其工艺性能显得尤为重要。采用含有无机元素的耐热性聚合物（聚硼氮烷）和碳化硼纳米粒子协同改性酚醛树脂的方法,能够克服单独加入碳化硼导致的酚醛树脂固化温度升高的问题。固化动力学分析表明,加入聚硼氮烷的酚醛树脂改性体系,其固化转化率显著高于同温度下酚醛树脂或碳化硼改性酚醛树脂的转化率。同时,聚硼氮烷和碳化硼协同改性酚醛树脂固化物在高温阶段（800～1000℃）的热解稳定性较改性前有大幅度的提高。通过红外光谱分析了不同热解程度下酚醛树脂及其改性物的结构,进一步阐述了聚硼氮烷和碳化硼协同作用对酚醛树脂改性体系固化行为和热解过程的影响机制。上述采用耐热性活性聚合物和碳化硼陶瓷粒子协同改性热固性树脂的方法,有望在高性能复合材料树脂基体中得到运用。     

油井堵水用高强度酚醛树脂预聚体封堵剂的合成

以苯酚、甲醛为原料,氢氧化钠为催化剂,采用两步碱催化方法合成了一种高强度酚醛树脂预聚体封堵剂。考察了甲醛与苯酚摩尔比、体系pH值、反应温度和反应时间等对酚醛树脂预聚体性能的影响。结果表明:当甲醛与苯酚摩尔比为3:1、体系pH值为9~10、反应温度为90℃、反应时间为30 min时,得到水溶性好、黏度较低的酚醛树脂预聚体,且该预聚体固化后,形成的固体强度高;封堵剂强度随酚醛树脂预聚体用量的增加而增大,当酚醛树脂预聚体的质量分数为50.0%时,填砂管模拟实验测得的突破压力梯度为40.65 MPa/m,具有很强的封堵能力。     

三乙醇胺催化制备热固性酚醛预聚体的研究

酚醛树脂作为应用广泛的热固性树脂,其预聚体的固化温度以及固化物的分解温度对其使用范围有重要影响。使用三乙醇胺制备热固性酚醛预聚体,利用差示扫描量热分析(DSC)和热失重分析(TG)等分析手段,表征了不同三乙醇胺催化制备酚醛树脂的固化过程和热失重过程。DSC测试表明,用三乙醇胺催化合成酚醛预聚体,当催化剂用量较低时,随着催化剂用量的增加,预聚体的固化温度逐渐降低;但当催化剂用量超过19g时,预聚体的固化温度逐渐升高。TG测试表明,三乙醇胺催化制备酚醛预聚体,其固化产物的热稳定性均不理想,几乎随着温度的升高呈现线性的失重。     

双重改性酚醛树脂的合成及性能研究

以环氧大豆油(ESO)和苯胺对酚醛树脂进行改性,得到分子结构中含有苯并噁嗪环的环氧豆油醚化增韧酚醛树脂预聚体,并通过红外光谱对其结构进行了表征。采用非等温差示扫描量热法及热重分析法分别对该预聚体的热固化温度及固化产物的耐热性进行了研究。同时研究了环氧大豆油不同添加量对改性树脂的冲击强度及弯曲强度的影响。研究结果表明,改性树脂的固化物失重5%时的温度为323℃,比纯酚醛树脂高80℃左右;而冲击强度在ESO添加量40%时为4.61 kJ/m2,是普通酚醛树脂的3~4倍。     

有机硅磷杂化改进环氧树脂耐热性、韧性和阻燃性的研究

将聚甲基三乙氧基硅烷（PTS）与一种合成的含磷硅烷偶联剂以一定配比进行反应,所得改性剂添加到双酚A环氧树脂E51/酚醛树脂固化体系中,对改性环氧树脂固化产物的玻璃化转变温度、热失重、冲击强度、拉伸强度、极限氧指数进行了测试,并对固化产物的表面形貌进行了SEM观察。结果表明,在保持拉伸强度基本不变的同时,改性环氧树脂固化物的玻璃化转变温度、高温热稳定性、冲击强度、极限氧指数均有不同程度提高,使改性环氧树脂的性能得到综合提升。     

IPN结构聚氨酯改性环氧树脂的性能研究

采用同步互穿聚合物网络技术制备了聚氨酯改性TDE-85/Me THPA环氧树脂体系,比较了环氧树脂TDE-85/MeTHPA固化体系改性前后力学性能和热稳定性的差异。研究结果表明,加入适量的由不同分子量聚醚二元醇合成的聚氨酯预聚体,对TDE-85/MeTHPA固化体系的力学性能、热稳定性均有所增加;当聚醚二元醇分子量为1000,且合成的聚氨酯预聚体加入量为15%时,同未改性的固化体系相比,该改性体系的拉伸强度和冲击强度分别上升48.0%和115%,分别达到69.39 MPa和23.56 kJ/m2,同时,该改性材料的热稳定性也有较明显的提高,其失重1%的温度T1%为300℃,比未改性的固化体系失重1%的温度高了30℃。     

三乙胺对酚醛树脂耐热性及层压制动材料摩擦性能的影响

以三乙胺作为催化剂制备了热固性酚醛树脂预聚体,并以酚醛树脂预聚体、芳纶纤维、玻璃纤维、铜丝制备了层压式制动材料。利用DSC、TG和蔡氏摩擦试验机等分析手段,对酚醛树脂预聚体的固化行为、固化物的热稳定性及酚醛基层压式制动材料的摩擦性能进行了研究。DSC测试结果表明,用三乙胺催化合成的酚醛树脂预聚体在280℃左右出现一个固化放热峰。TG测试结果表明,用三乙胺催化制备酚醛树脂预聚体存在一个最佳用量,当三乙胺用量为27 g时,酚醛树脂固化物的热性能最好;当三乙胺用量为33 g时,酚醛树脂固化物的初始失重率较大,但在300~400℃时酚醛树脂固化物的热失重率很小。摩擦试验表明,当三乙胺用量为33 g时,层压制动材料的摩擦系数较为稳定。     

Effect of the structure of curing agents modified by epoxidized oleic esters on the toughness of cured epoxy resins

The aim of this study was to determine the effect of the ester carbon chain length of curing agents modified by epoxidized oleic esters on the toughness of cured epoxy resins. An amine‐terminated prepolymer (i.e., curing agent G) was synthesized from a bisphenol A type liquid epoxy resin and triethylene tetramine. The toughening curing agents (G1 and G2) were prepared by reactions of epoxidized oleic methyl ester and epoxidized oleic capryl ester, respectively, with curing agent G. Fourier transform infrared spectrometry was used to characterize the chemical structure of the curing agents. The effects of the carbon chain length of the oleic ester group in the curing agents on the toughness and other performances of the curing epoxy resins were investigated by analysis of the Izod impact strength, tensile strength, elongation at break, thermal properties, and morphology of the fracture surfaces of the samples. The results denote that the toughness of the cured epoxy resins increased with the introduction of oleic esters into the curing agents without a loss of mechanical properties and that the toughness and thermal stability of the materials increased with increasing ester carbon chain length. The toughness enhancement was attributed to the flexibility of the end carbon chains and ester carbon chains of the oleic esters in the toughening curing agents. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

异氰酸酯/可发性酚醛树脂泡沫体的制备

采用端异氰酸酯聚醚预聚物与可发性酚醛树脂制备了新型泡沫体。通过ESI-MS光谱分析和泡沫物理力学性能测试研究了异氰酸酯基团与可发性酚醛树脂比例、异氰酸酯基团和三聚体相对含量、可发性酚醛树脂分子质量对泡沫体制备及性能的影响。结果表明:异氰酸酯基团与酚醛树脂质量比为40/100、三聚体质量分数17.33%、酚醛树脂聚合时间45min时,泡沫体的体积稳定性好,收缩率低;可发性酚醛树脂分子质量增加时,泡沫体的密度从60.16kg/m3增加到63.96kg/m3,基本保持稳定;其弯曲强度为0.2MPa,弯曲应变达到15%以上,远高于纯酚醛泡沫(6%)。在150℃下烘烤2h,泡沫体的质量损失为6%左右,体积变化为-5%左右。泡沫体的热稳定性优于聚氨酯泡沫,同时又有良好的韧性。     

气干性酚醛环氧乙烯基树脂的研制

采用交联共聚法合成了气干性酚醛环氧乙烯基树脂。研究了物料配比、阻聚剂用量、反应温度对反应的影响,测试了树脂的耐腐蚀性、气干性和力学性能。结果表明,酯化过程最佳工艺条件为:反应温度110～115℃,反应时间2.5 h,醇、酸物质的量比1.1∶2,阻聚剂质量分数0.05%,催化剂质量分数0.3%。交联聚合过程最佳工艺条件为:反应温度75～85℃反应时间2.0 h,改性剂(甲苯二异氰酸酯)加入质量5%。合成的树脂的弯曲强度为101 MPa,弯曲模量3.66 GPa,冲击强度11.4 kJ/m2,气干性、韧性、固化性能均超过同类树脂,可用于耐温强腐蚀场合以及用作表面涂层、耐温腻子基体树脂、自流平树脂等。     

Preparation and properties of cyanate ester modified by epoxy resin and phenolic resin

Stiff and brittle cyanate ester (CE) resin was modified by copolymerizing it with epoxy resin (ER) and phenolic resin (PR) to improve its toughness and flexibility. The cure process of the modified CE resin was characterized by gel time curves and differential scanning calorimetry curves. The Fourier transform infrared spectra of the modified CE resin showed its chemical structure during the curing process. The mechanical properties, thermal behavior, dielectric properties, and morphology of the modified CE resins were investigated. The results showed that an increase in epoxy and phenolic resins resulted in improved flexibility while maintaining thermal stability. When the mass ratio of CE/ER/PR was 70 : 15 : 15 (w/w), flexural strength and impact strength of the modified CE resin increased from 113.6 MPa and 5.2 kJ/m² to 134.5 MPa and 16.7 kJ/m², respectively. Little of the thermal stabilityand dielectric properties was sacrificed in the modification of the CE. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3150–3156, 2007     

Novel phenolic resins with improved mechanical and toughness properties

Novel phenolic type of thermoset resins were synthesized, and their mechanical and toughness properties were evaluated. Phenol Formaldehyde (PF) phenolic resins were modified to broaden their applications for modern composite structures. A first modification consisted of copolymerization of Phenol with Cardanol during the synthesis of resole phenolic (CPF) resins. The modified phenolic resins (CPF) were prepared at various molar ratios of total Phenol to Formaldehyde (F : P ratio) and with different weight ratios of Phenol to Cardanol. CPF resins with a maximum content of 40 wt % of Cardanol were synthesized and used. The CPF resins were applied as a plasticizer and toughening agent to the base PF resins. Both resins (CPF/PF) were mixed in different proportions, and their thermal and mechanical properties were then established. A full miscibility of the two resins was observed with the formation of a single‐phase system. An increase in the content of Cardanol resulted in a proportional increase of the flexural strength and fracture toughness together with a decrease of the flexural modulus of the cured CPF/PF resins. Further increased plasticizing and toughening effect was also observed by the blending of the CPF resins with propylene glycol. The higher toughness and flexibility effect of the CPF resins was obtained with a F : P molar ratio equal to 1.25 and with a Cardanol content of 40% (w/w). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A novel addition curable novolac bearing phthalonitrile groups: synthesis,characterization and thermal properties

Summary Novel phenolic novolac resins, bearing phthalonitrile groups anchored to benzene ring through phenyl azo linkage were realized by the coupling reaction between novolac and phthalonitrile diazonium salt. The diazo-coupling occurred to a maximun of about 61%. The apparent molecular weight, determined form GPC showed a downward drift with increase in degree of phthalonitrile substitution. Analysis using DSC technique indicated that the resin underwent curing in a temperature range form 290 to 320 °C . The curing occurred via addition polymerization of phthalonitrile groups. The thermal stability and anaerobic char yield of the polymers increased proportion to the crosslinking. The probable cure mechanics were discussed.     

淀粉基生物质胶粘剂的固化与性能研究

将淀粉在硫酸作用下水解的产物用于替代甲醛与苯酚进行缩聚反应生成淀粉基酚醛树脂,然后以六次甲基四胺为固化剂进行交联固化。研究了淀粉基酚醛树脂的凝胶时间、固化反应表观活化能、冲击强度、热失重性能与断面形貌,并与甲醛基酚醛树脂性能进行比较。结果表明,淀粉基酚醛树脂的固化反应表观活化能为19.8kJ/mol,冲击强度为741J/m2,600℃质量残留率为40%,具有良好的耐热性能,游离甲醛质量分数仅为0.4%,大大低于常规酚醛树脂的甲醛含量。     

Toughening of epoxy resin using synthesized polyurethane prepolymer based on hydroxyl-terminated polyesters

Epoxy resins are increasingly finding applications in the field of structural engineering. A wide variety of epoxy resins are available, and some of them are characterized by a relatively low toughness. One approach to improve epoxy resin toughness includes the addition of either a rigid phase or a rubbery phase. A more recent approach to toughen brittle polymers is through interpenetrating network (IPN) grafting. It has been found that the mechanical properties of polymer materials with an IPN structure are fairly superior to those of ordinary polymers. Therefore, the present work deals with epoxy resin toughening using a polyurethane (PU) prepolymer as modifier via IPN grafting. For this purpose, a PU prepolymer based on hydroxyl-terminated polyester has been synthesized and used as a modifier at different concentrations. First, the PU-based hydroxyl-terminated polyester has been characterized. Next, an IPN (Epoxy–PU) has been prepared and characterized using Fourier transform infrared (FTIR) spectroscopy, thin-layer chromatography (TLC), and scanning electron microscopy (SEM) prior to mechanical testing in terms of impact strength and toughness. In this study, a Desmophen 1200-based PU prepolymer was used as a modifier at different concentrations within the epoxy resin. The results also showed that, further to the IPN formation, the epoxy and the PU prepolymer reacted chemically (via grafting). Compared to virgin resin, the effect on the mechanical properties was minor. The impact strength varies from 3–9 J/m and K_c from 0.9–1.2 MPa m^1/2. Furthermore, the incorporation of a chain extender with the PU prepolymer as a modifier into the mixture caused a drastic improvement in toughness. The impact strength increases continuously and reaches a maximum value (seven-fold that of virgin resin) at a modifier critical concentration (40 phr). K_c reaches 2.5 MPa m^1/2 compared to 0.9 MPa m^1/2 of the virgin resin. Finally, the SEM analysis results suggested that internal cavitation of the modifier particles followed by localized plastics shear yielding is probably the prevailing toughening mechanism for the epoxy resin considered in the present study. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2603–2618, 1998     

Toughening of a dicyandiamide-cured epoxy resin: Influence of cure conditions on different rubber modifications

Cure kinetics of modified epoxy resins cured with dicyandiamide are studied. The influence of different heating rates in the curing process, such as curing behavior, morphology, and thermo-mechanical properties, is studied. Additionally, three different post-cure cycles at 180°C are employed. Two butadiene-based toughening agents are used, a carboxyl-terminated polybutadiene-co-acrylonitril (CTBN) prepolymer and a functionalized block copolymer of polytetrahydrofuran and hydroxyl-terminated polybutadiene. The amphiphilic block copolymer enables investigations with a bimodal particle size morphology. All results are contrasted with those of the neat resin and butadiene-free block polymer. Faster curing processes result in smaller average particle sizes and better fracture toughness of the modified epoxy resins. Further improvements are achieved with additional post-cure cycles at 180°C. An increased interfacial adhesion between the particles and the epoxy matrix is considered to be the main mechanism. Optimized lengths of the post-cure process can be determined with the butadiene-based toughening agents indicating a competing thermal degradation. Longer post-cures than 40 min lead to lower fracture toughness in the butadiene-based modified materials. In general, similar influences of the curing and post-curing process on the bimodal and unimodal distributed system can be observed differing in more intense dependencies of the bimodal system.