The effects of experimental parameters on the extent of intercalation of PMMA/MMT nanocomposites prepared in solution

The effects of various parameters on nanocomposite preparation by solution intercalation were studied. Nanocomposites of poly(methyl methacrylate) (PMMA) and commercial organically modified montmorillonites (MMT) were prepared in solvents of different polarities, from strongly polar protic ethanol to nonpolar toluene. The extent of intercalation was studied in correlation with processing parameters, such as time of intercalation, temperature, concentration of PMMA/MMT in solution, and method of preparation determined by X‐ray diffractometer. Solvent polarity was the most important of all studied parameters. In general, the lower the dielectric constant of the solvent, the better the intercalation is; however, the exact correlation also depends on the type of modifier. Another important parameter is isolation of the nanocomposite, whereas other studied parameters are of minor importance. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Intercalation of epoxy resin in organically modified montmorillonite

Various methods of preparation of epoxy resin/clay mixtures, before the addition of the crosslinking agent and curing to form epoxy‐based polymer layered silicate (PLS) nanocomposites, have been investigated to determine their effect on the nanostructure. Organically modified montmorillonite clay was used, and the mixtures were prepared by both simple mixing and solvent‐based methods. X‐ray diffraction shows that intercalation of the resin into the clay galleries occurs for all clay loadings up to 25 wt % and for both preparation methods, but the dispersion of the clay in the resin, observed by optical microscopy, is significantly better for the solvent preparation method. Differential scanning calorimetry (DSC) shows that the intercalated resin has the same molecular mobility as the extra‐gallery resin, but suggests that the intercalated resin does not penetrate completely into the galleries. Prolonged storage of the resin/clay mixtures at room temperature leads to changes in the DSC response, as well as in the response to thermogravimetry, which are interpreted as resulting from homopolymerization of the epoxy resin, catalyzed by the onium ion in the modified clay. This confirms and explains the earlier observation of Benson Tolle and Anderson (J Appl Polym Sci 2004, 91, 89) that “conditioning” of the resin/clay mixtures at ambient temperature has a significant effect when the crosslinking agent is subsequently added, and indicates that the preparation method has important consequences for the nanostructure development in the PLS nanocomposites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:3751–3763, 2006     

Curing behavior and thermal property of epoxy resin with boron‐containing phenol‐formaldehyde resin

The curing reaction of bisphenol‐A epoxy resin (BPAER) with boron‐containing phenol–formaldehyde resin (BPFR) was studied by isothermal and dynamic differential scanning calorimetry (DSC). The kinetic reaction mechanism in the isothermal reaction of BPAER‐BPFR was shown to follow autocatalytic kinetics. The activation energy in the dynamic cure reaction was derived. The influence of the composition of BPAER and BPFR on the reaction was evaluated. In addition, the glass transition temperatures (T_gs) were measured for the BPAER‐BPFR samples cured partially at isothermal temperatures. With the curing conditions varying, different glass transition behaviors were observed. By monitoring the variation in these T_gs, the curing process and the thermal property of BPAER–BPFR are clearly illustrated. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1054–1061, 2000     

含有联萘基团的环氧树脂的合成与固化

合成了一种具有联萘结构的环氧树脂(BEBN)。通过红外光谱、核磁共振氢谱以及元素分析对其结构进行了表征。以双酚A型环氧树脂(E-51)作为参照,采用二氨基二苯基甲烷为固化剂,通过差示扫描量热法(DSC)研究了BEBN,E-51的固化反应性;采用DSC,热重分析对固化物的热学性能进行测试,比较了固化物的力学性能、热性能以及吸水率;探讨了BEBN的结构与性能之间的关系。结果表明,同E-51相比,BEBN的固化反应平缓：BEBN固化物的玻璃化转变温度升高29℃,吸水率降低0．31％,热失重5％和50％的温度分别升高15℃和13℃。     

潜伏性环氧固化剂研究进展

按固化条件的不同分别介绍了加热型、光固化型、潮湿型潜伏性环氧固化剂,列举了各类固化剂的典型代表及其性质,展望了今后潜伏性固化剂的研究重点和发展趋势。     

Rubber–clay nanocomposite by solution blending

Ethylene vinyl acetate rubber (45% vinyl acetate content, EVA‐45) and organomodified clay (12Me‐MMT) composites were prepared by solution blending of the rubber and the clay. A combination of X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy studies showed that the composites obtained are on the nanometer scale. The measurements of the dynamic mechanical properties for different compositions over a temperature range (?100 to +100°C) showed that the storage moduli of these rubber–clay nanocomposites are higher above the glass to rubber transition temperature compared to the neat rubber. The tensile strength of the nanocomposites is about 1.6 times higher than that of the EVA‐45. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2216–2220, 2003     

Synthesis and properties of polyurethane/clay nanocomposite by clay modified with polymeric methane diisocyanate

A polyurethane (PU)/clay nanocomposite was synthesized from polyol, polymeric 4,4′‐diphenyl methane diisocyanate (PMDI), and modified clay with PMDI. To achieve the modified clay with PMDI, the silanol group of the clay and the NCO group of the PMDI were reacted for 24 h at 50°C to form urethane linkage. Fourier transform IR analysis of the clay modified with the PMDI demonstrated that the NCO characteristic peak was observed in the clay after a modification reaction with PMDI. The results of the X‐ray pattern suggested that the clay layers were exfoliated from the PU/clay nanocomposite. From the results of the mechanical properties, the maximum values of the flexural and tensile strength were observed when 3 wt % clay based on PMDI was added into the PU/clay nanocomposites. The glass‐transition temperature and change in the heat capacity at glass transition temperature (ΔC_p) of the PU/clay nanocomposite decreased with an increase in the modified clay content. We suggested that the decrease in the ΔC_p with the modified clay content might be due to the increase of steric hindrance by the exfoliated clay layers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2879–2883, 2006     

Copper particles/epoxy resin thermosetting conductive adhesive using polyamide resin as curing agent

Thermosetting conductive adhesive (TCA) comprised of epoxy resin E‐51 as matrix, Cu microparticles and nanoparticles modified by silane coupling KH550 as conductive fillers, polyamide resin with low molecular weight as curing agent, and some other additives. It was reported creatively a new liquid curing agent, which solved successfully some difficult problems during preparation of TCA, such as limit of quantity of conductive fillers. Therefore, application of this liquid curing agent decreased greatly the resistivity of TCA under the condition of keeping enough adhesion strength. Antioxidized and mixed Cu particles were developed as conductive fillers in place of expensive Ag. The results showed that optimum conditions of conductive adhesive composed of 16 wt % of epoxy resin E‐51, 8 wt % polyamide resin, 65 wt % of Cu microparticles and nanoparticles, 1.3 wt % of silane coupling agent, and 9 wt % of other additives with curing time for 4 h at 60°C. The adhesion strength reached 16.7 MPa and the bulk resistivity was lower than 3.7 × 10^?4 Ω cm. The variation of bulk resistivity was less than 15% at high temperature (100°C). © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation of polyethylene–clay nanocomposites directly from Na+ montmorillonite by a melt intercalation method

Polyethylene (PE)/clay nanocomposites were prepared directly from Na⁺ montmorillonite by a melt intercalation technique, using hexadecyl trimethyl ammonium bromide (C16) as a reactive compatibilizer. Three other polymer–clay nanocomposites were also prepared by this new technique. Their structures were characterized by X‐ray diffraction and transmission electron microscopy. The mechanism of this new method was studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2583–2585, 2003     

叔胺催化环氧树脂/水性醇酸树脂固化行为及其性能研究

从合成的水性醇酸树脂(AR)和水性环氧树脂(ER)出发,合成了水性ER/AR树脂,用红外光谱仪、差示扫描量热仪研究了叔胺催化的固化行为;用动态力学谱仪、热重分析技术研究了材料的玻璃化转变温度(Tg)和热降解性能,测定了ER/AR玻璃钢复合材料的力学和电性能以及涂膜的性能。结果表明,N-N二甲基苄胺对该体系有很好的催化作用;材料的Tg随着AR含量的增加呈现降低的趋势,当ER/AR的质量比为5 ：5时,Tg为64.6 ℃,拉伸强度为141.67 MPa,冲击强度达到120.54 kJ/m2;ER/AR玻璃钢复合材料的介电常数在1.5 1.99之间, 损耗角正切在0.001~0.008之间;涂膜的硬度高于4H,冲击强度可达20 kg·cm。     

环氧树脂固化剂的改性研究

以异佛尔酮二胺和1,6-己二胺为原料,加入适量自制的催化剂,在190℃反应2.5 h,即制成新型环氧树脂固化剂(简称YFJA)。将其按不同比例添加到传统固化剂二氨基二苯甲烷(简称DDM)和甲基四氢苯酐(简称Me-THPA)中,通过对固化物的冲击强度、拉伸强度和力学损耗等性能的检测分析,发现当自制固化剂添加量为固化剂总量的50%时,体系的力学性能达到最佳效果,冲击强度最高可提高346.5%,拉伸强度可提高73.0%。     

新型环氧树脂固化剂的合成及其环氧胶粘剂

以4,4’-二氨基二苯甲烷为原料,经乙酰化、硝化、酸解、还原、中和5步反应合成得到了一种新型环氧树脂固化剂,即3,3’,4,4’-四氨基二苯甲烷,并通过FT—IR分析及熔点测定对其进行了表征。此外,对改性环氧树脂／3,3’,4,4’-四氨基二苯甲烷体系也作了性能研究。     

Synthesis and characterization of sulfonated poly(ethylene terephthalate)/montmorillonite nanocomposites

Sulfonated poly(ethylene terephthalate) (SPET)/montmorillonite nanocomposites were prepared by in situ intercalative polymerization. The microstructure, morphology, and properties of the nanocomposites were studied with wide‐angle X‐ray diffraction, transmission electron microscopy, atomic force microscopy, differential scanning calorimetry, and thermogravimetric analysis. The results indicated that an increase in the ? SO₃Na content improved the dispersion of organically modified montmorillonite in the SPET ionomer matrix, and the dispersed layered silicates in the SPET matrix acted as nucleating agents in SPET crystallization processes and improved the thermal stability of SPET. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1150–1156, 2005     

Effect of montmorillonite on the swelling behavior and drug‐release behavior of nanocomposite hydrogels

A series of nanocomposite hydrogels were prepared from various ratios of N‐isopropylacrylamide (NIPAAm) and organic montmorillonite (MMT). The influence of the extent of MMT in the NIPAAm/MMT nanocomposite hydrogels on the physical properties and drug‐release behavior was the main purpose of this study. The microstructure and morphology were identified by X‐ray diffraction (XRD) and scanning electronic microscopy (SEM). The results showed that the swelling ratios for these nanocomposite hydrogels decreased with increase in the content of MMT. The gel strength and Young's modulus of the gels also increased with increase in the content of MMT. XRD results indicated that the exfoliation of MMT was achieved in the swollen state. Finally, the drug‐release behavior for the gels was also assessed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3652–3660, 2003     

剥离型酚醛树脂/蒙脱土纳米复合材料研究

用十六烷基三甲基溴化铵(CTAB)对蒙脱土进行了有机化处理,使蒙脱土由亲水性变成亲油性。采用XRD、FTIR及TEM研究了有机蒙脱土及其在酚醛树脂中的剥离行为,制备了酚醛树脂/蒙脱土纳米复合材料并测试了其层间剪切性能和烧蚀性能。实验结果表明,经CTAB处理的蒙脱土与酚醛树脂具有良好的相容性,且CTAB的含量较多时所制得的有机蒙脱土的结构较好,根据Bragg方程计算,CTAB用量超过蒙脱土量50%时,蒙脱土的片层间距由原来的1.48 nm增加到2.33 nm;有机蒙脱土用量小于5%时生成完全剥离型酚醛树脂/蒙脱土纳米复合材料;与碳布增强酚醛树脂复合材料相比,碳布增强酚醛树脂/蒙脱土纳米复合材料的力学性能和烧蚀性能均有一定的提高和改善,层间剪切强度随蒙脱土含量的增多而增大,蒙脱土用量为15%时,层间剪切强度提高了27.1%,线烧蚀率在用量为3%时降低了48.5%,质量烧蚀率变化不明显。     

The effects of promoter and curing process on exfoliation behavior of epoxy/clay nanocomposites

The effects of a catalyst and coupling agent as well as a curing process on exfoliation behavior of CH₃(CH₂)₁₅NH₃+–montmorillonite clay in an anhydride‐cured epoxy–clay system have been investigated by XRD, DSC, and TEM. The results have shown that the organoclay is easily intercalated by the epoxy precursor during the mixing process, and the clay galleries continue to expand during the curing process, but the Na⁺–montmorillonite clay is not intercalated during either the mixing or the curing process. The results also suggest that in the cured system without any promoter although partial exfoliated clay layers have already formed, an amount of the intercalation structure still remains. Although addition of a promoter or coupling agent into the cured system significantly lowers the maximum reaction temperature, and during the curing process the layered organoclay can be gradually broken into nanoscale structures, in which no d₀₀₁ diffraction peaks are observed, the complete exfoliation is achieved at gel time or before. The possible mechanism for the complete exfoliation is discussed on the thermodynamic and kinetic point of view. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 808–815, 2000     

水性环氧树脂乳化型固化剂固化特性研究

在多元胺中引入环氧树脂(EP),再通过成盐反应,合成出含仲胺盐结构、可乳化液体EP的固化剂;然后采用相反转法制备出稳定的水性EP乳液。结果表明:该固化剂在室温时具有一定的潜伏性(水性EP乳液室温储存期超过14 d),而在较高温度时具有快速固化的特点。仲胺盐的起始分解温度(Ti)约为113℃,当固化温度较低时,仲胺盐热分解反应难以进行,封闭的仲胺基与环氧基的固化反应难以发生,表现为成盐率越高,乳液凝胶时间越长;当固化温度>Ti时,仲胺盐快速热分解后释放出被封闭的活性仲胺基,乳液可快速固化,成盐率对乳液凝胶时间的影响不大。各固化膜均具有较低的吸水率(<3.1%),其耐水性和耐丙酮性能优良,但耐强酸、强碱性能较差且随固化剂成盐率提高而下降。     

Properties and microstructures of epoxy resin/TiO2 and SiO2 hybrids

Epoxy resin/TiO₂ and epoxy resin/SiO₂ hybrids were prepared by different procedures, and their mechanical properties were correlated to their microstructures, as indicated by small‐angle X‐ray scattering (SAXS) measurements. Epoxy resin/TiO₂ hybrids were prepared by mixing the epoxy resin (EP828) with N‐(2‐aminoethyl)‐3‐aminopropyltrimethoxysilane (S320) in acetone, and then titanium‐n‐butoxide (TnBU) was added. In addition, epoxy/SiO₂ hybrids were prepared by mixing EP828 with a curing agent, a diamino heterocyclic compound (B002) in acetone, and an organo silica sol (silica nanoparticles dispersed in methylethylketone) was added. In the EP828/S320/TiO₂ hybrid systems, the TiO₂ component was attached to both of the chain ends of the epoxy matrix, hence leading to the formation of inorganic domains via the covalent bonds. SAXS profiles of these hybrids showed peaks at q = 2.3 nm^?1, caused by interference between the domains. The storage modulus increased with increasing TiO₂ content above the T_g, owing to the strong interactions between TiO₂ and the epoxy matrix. The tanδ peak position did not change, although the intensity decreased with increasing TiO₂ content. The SAXS profiles of the EP828/B002/SiO₂ hybrids were very different to those of the corresponding EP828/S320/TiO₂ hybrids, and indicated that SiO₂ particles with rough surfaces were randomly dispersed in the epoxy matrix. The storage moduli of the EP828/B002/SiO₂ hybrid systems increased only slightly with SiO₂ content, because of the weak interactions. These mechanical properties are well explained by the microstructures derived from the SAXS profiles. Copyright © 2004 Society of Chemical Industry     

一种新型环氧树脂固化剂的合成

以乙二胺和含有8个丙烯酸酯双键的化合物(I)为原料,甲醇为溶剂和催化剂,经迈可尔加成反应合成了多氨基的化合物。考察了投料比、反应温度、反应时间以及溶剂等因素对反应产率和纯度的影响。并研究了此化合物作为环氧树脂固化剂的不同固化时间,得其比乙二胺体系的固化速度快3-60倍。     

Preparation and analysis of a flexible curing agent for epoxy resin

A kind of novel aromatic amine bis(4‐nonyl‐2,5‐diamine‐penoxyl)alkylate (RA_n) as curing agents for epoxy resins were prepared through three steps of reactions using nonyl phenol and dibromoalkylate as materials. Dynamic mechanical analysis (DMA) indicated that the secondary relaxation for the resins cured by RA_n were generated by the nonyls in RA_n molecules when temperature was below ?50°C. Comparing with other reference resins, the enhancement for toughness of RA_n cured‐resins were at least 15%, which were contributed by such secondary relaxation. Furthermore, stiffness of the networks and thermal properties of the resins were not influent by the flexible groups (nonyl) in RA_n after curing, since the groups were located only in the branched chains of the networks. The mechanical and thermal properties of the new material have been significantly enhanced. The relevant method and procedure developed through this research have been granted Chinese patent recently (Yang and Gong, Chin. Pat. CN1978483A, 2007). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009