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861.
Epoxy/polysufone (PSF) composites cured with 4,4'-diaminodiphenyl sulfone (DDS) and 4,4'-diaminodiphenyl methane (DDM) were fabricated, and the effect of dual curing reaction of diamines with epoxy on morphology, mechanical, and thermal performance was investigated. DSC results indicated that DDM was more reactive than DDS and the activation energy decreased with the rising of DDM content. Structures with small domain size at the early stage of phase separation were fixed by the fast epoxy-DDM reaction. When the DDM content was elevated to a high level, large dual structures were changed to fine bicontinuous structures, which was favorable to improve the mechanical property. The mechanical performance of epoxy composites was enhanced and the maximum values were achieved when the DDM/DDS ratio was located at 75/25 (PSF/DDS0.25-DDM0.75). The flexural and tensile strength relative to epoxy/DDM system were enhanced more than those relative to epoxy/DDS, while the increase in toughness was the opposite. TGA measurement showed that thermal stability of epoxy/PSF composites was improved because of the restricting effect of continuous PSF domains on thermal motion of epoxy. DMA analysis exhibited two relaxation peaks for PSF/DDS0.25-DDM0.75, which could be attributed to the formation of phase separated morphology and epoxy network with different cross-link density. 相似文献
862.
Presented here is an investigation of the structure–property relationships of crosslinked networks using three bi-functional glycidyl ether aromatic epoxy resins, two bi-aryl and one tri-aryl, cured with bi- and tri-aryl amines. Subtle changes to the monomer chemistry including changing aromatic substitution patterns from meta to para, methylene to isopropyl and isopropyl to ether were explored. Changing an epoxy resin backbone from methylene to isopropyl enhances backbone rigidity thus increasing glass transition temperature (Tg), yield strength, and strain despite reducing modulus. Changing meta-substitution to para increases Tg and yield strain while leaving strength unaffected and reducing modulus. Changing isopropyl linkages to ether reduces modulus, strength, Tg, and yield strain reflecting increased molecular flexibility. Using three instead of two aromatic rings increases the molecular weight between crosslinks thereby decreasing Tg and yield strain while increasing modulus and strength. Despite the complexities of multiple systems for varying epoxy resins and amine hardeners, the effect upon network properties is explained in terms of short- and long-range molecular and segmental mobility, crosslink density, and equilibrium packing density. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48874. 相似文献
863.
Huanhuan Dong Yuanfang Luo Jing Lin Jie Bai Yongjun Chen Bangchao Zhong Demin Jia 《应用聚合物科学杂志》2020,137(26):48838
Rubber blends are widely used for combining the advantages of each rubber component. However, to date, how to determine and distinguish the vulcanization kinetics for each single rubber phase in rubber blends during the co-vulcanization process is still a challenge. Herein, high-resolution pyrolysis gas chromatography–mass spectrometry (HR PyGC-MS) was employed for the first time to investigate the vulcanization kinetics of natural rubber (NR) and styrene–butadiene rubber (SBR) in NR/SBR blends filled with modified silica (SiO2). The reaction rates of crosslinking of each rubber phase in NR/SBR were calculated, which showed that the crosslinking rates of NR were much lower than those of SBR phase in the unfilled blends and blends filled with unmodified and silane modified silica. Interestingly, the vulcanization rates of NR and SBR phase were approximately same in the vulcanization accelerator modified silica filled blends, showing better co-vulcanization. In addition, the vulcanization accelerator modified silica was uniformly dispersed and endowed rubber blends with higher mechanical strength compared to the untreated silica. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48838. 相似文献
864.
865.
866.
以二氯乙二肟、二甲基甲酰胺、叠氮化钠、盐酸羟胺和硝酸铅等为原料,合成了1,1-二羟基-5,5′-联四唑羟胺铅盐(Pb-TKX-50)燃烧催化剂,研究了Pb-TKX-50对推进剂机械感度的影响以及与推进剂组分的相容性;利用差示扫描量热法和热重法研究了Pb-TKX-50在不同升温速率下的热分解过程,计算其表观活化能(E K和E O)和指前因子(A K),得到其热分解动力学参数、热分解机理函数、热爆炸温度和热力学性质。结果表明,在推进剂配方中加入Pb-TKX-50燃烧催化剂,可以改善其撞击感度和摩擦感度,且与推进剂组分的相容性良好;Pb-TKX-50的主峰分解温度相对于TKX-50的主峰分解温度显著提高,说明其热稳定性显著提高。Ozawa法和Kissinger法得到Pb-TKX-50的表观活化能分别为181.45 kJ/mol和182.49 kJ/mol,且热分解过程符合Avrami-Erofeev方程;Pb-TKX-50的自加速分解温度和爆炸临界温度分别为500.53 K和544.33 K,表明其热稳定性良好;Pb-TKX-50催化剂的热分解自由能(ΔG^≠)为158.87 kJ/mol,活化焓(ΔH^≠)为187.03 kJ/mol,活化熵(ΔS≠)为52.98 kJ/mol。 相似文献
867.
脲醛树脂(UF树脂)胶黏剂具有胶合强度高、制作简单、成本低廉、原料来源丰富等一系列特点,成为我国人造板生产的主要胶种,是市场上需求量最大的胶黏剂之一。但由于在固化时会放出刺激性的甲醛,游离甲醛高,在使用时严重危害人的健康。近年来,随着人们环保意识的提高,生产和使用低毒UF树脂胶势在必行。本文介绍了稀土氧化镧对脲醛树脂的改性过程并对改性后脲醛树脂胶的各项性能进行了测试。本实验通过在不同反应阶段加入稀土氧化镧,分别探讨它们对脲醛树脂胶黏剂性能影响。实验表明:在脲醛树脂胶中加入稀土氧化镧可以增加黏度、固化时间、固含量,并可以减少游离甲醛释放量。 相似文献
868.
以白云石粉为原料,利用TG、DTG、DSC联用的方法对白云石进行非等温热分解动力学研究,并进行了物相分析。结果表明,在Ar气保护和升温速率10 ℃/min的条件下,白云石的热分解是分两步进行的,第一步(CO32的扩散为控制步骤)、第二步(CO2的逸出为控制步骤)开始分解的温度分别在470、700 ℃,与纯物质的理论值相差较大;白云石的分解温度范围主要在470~590 ℃、700~820 ℃,在800 ℃时有个最大的吸热峰,此后白云石热分解吸热逐渐减小,温度达到820 ℃时失重率达到最大值45.27%,也几乎不再吸热,说明没有晶格转变在消耗能量。利用Freeman-Carroll的差减微分法对白云石非等温热分解计算分析,得到活化能E分别约为62.488、73.880 kJ/mol,指前因子A分别约为14.360、 ,两阶段的反应级数n分别约为0.490、0.819,白云石热分解过程属于相界反应模型。 相似文献
869.
870.
研究了脉冲辐解过程中氨基羟基脲与水辐解活性粒子(e-aq、·OH和·H)及单电子氧化剂·CO3-的反应动力学过程。反应近似为准一级反应,反应速率常数分别为k(e-aq)=1.41×108 L/(mol·s)、k(·OH)=1.05×1010 L/(mol·s)、k(·H)=2.68×105 L/(mol·s)、k(·CO-3)=4.25×108 L/(mol·s)。其中氨基羟基脲与·OH的反应速率常数最大,故在辐解过程中其为主要反应。 相似文献