顺序双重热固化的硫醇-丙烯酸酯-环氧树脂三维网络的构建及性能

在常温下,叔胺催化的巯基-丙烯酸酯和巯基-环氧反应活性的差异明显,具有可控顺序固化特征。以四(3-巯基丙酸)季戊四醇酯(SH4)、对苯二甲醇二缩水甘油醚(BOB)或2,5-呋喃二甲醇二缩水甘油醚(BOF)、1,4-环己烷二甲醇二丙烯酸酯(CHDMDA)构建了硫醇-丙烯酸酯-环氧顺序双重热固化体系,并研究氢键对体系固化过程及性能的影响。采用FTIR、流变分析、DSC、DMA、万能材料试验机和硬度仪表征了一重固化后的中间态材料和二重固化后的终态材料的热性能、流变性能、力学性能及常温适用期。结果表明,氢键的存在会延缓双重固化反应的进行,提高终态材料的力学性能。此外,此顺序双重热固化体系所产生的两阶段材料流变性能、热性能和力学性能可调控,中间态材料可在室温24 h保持性能稳定。可控顺序双重固化赋予热固性聚合物方便的复杂形状加工成型、高性能于一身,以及更广泛的应用范围,如形状记忆致动器和压敏胶膜,突破了热固性塑料在形状设计与加工上的局限性。     

新型脂环环氧树脂/胺体系固化动力学及性能研究

采用DSC研究了脂环环氧树脂稀释剂1,4-环己烷二甲醇二缩水甘油醚(CHDMDGE)与异佛尔酮二胺及聚醚胺D230的固化行为,得出其固化反应的活化能、指前因子和反应级数等动力学参数。通过外推法计算出了固化工艺的特征温度,以此为依据制定了固化工艺并对固化后体系的力学性能进行了测试。结果表明,与线形脂肪族环氧稀释剂1,4-丁二醇二缩水甘油醚和1,6-己二醇二缩水甘油醚相比,CHDMDGE的拉伸强度分别提高了0.4倍和2.7倍,断裂伸长率则提高了1.9倍和5.0倍。     

环氧基POSS/PAMAM杂合材料的制备及性能研究

以3-缩水甘油基氧丙基三甲氧基硅烷(EPTMS)为原料,合成得到了八官能团缩水甘油醚-多面体低聚倍半硅氧烷(简称POSS-EP)。采用4代树型端氨基聚酰胺-胺(PAMAM)作为POSS-EP和双酚A型环氧树脂(DGEBA)共混物的固化剂,制备了5个环氧基POSS/PAMAM杂化材料。通过动态差示扫描量热仪(DSC),研究了环氧和PAMAM的固化反应动力学。通过DSC、热重分析(TGA)、拉力和冲击测试,对环氧基POSS/PAMAM杂化材料的热性能和力学性能进行了研究。结果表明,该环氧基POSS/PAMAM杂化材料具有优良的热性能和力学性能。     

环氧改性聚氨酯防水灌封材料的合成及性能研究

以丁羟胶(HTPB)、异佛尔酮二异氰酸酯(IPDI)为原料合成预聚体,采用双酚A二缩水甘油醚(环氧E51)及3,3′-二氯-4,4′-二氨基二苯基甲烷(MOCA)对其固化。通过力学性能和吸水率测试研究了环氧树脂添加量对聚氨酯性能的影响。研究表明,环氧的添加增加了聚氨酯的硬度,当环氧添加质量分数为10%时,材料的力学性能最好。而材料的吸水率随着环氧量的增加而降低。     

新型脂环族环氧树脂的制备与性能

制备了脂环族环氧树脂——1,2-环己二醇二缩水甘油醚,用傅里叶红外光谱对其结构进行表征,测试了其固化物的热性能、力学性能、电性能。结果表明,1,2-环己二醇二缩水甘油醚具有良好的力学性能和电性能,在电工材料、电子封装领域有广泛的应用前景。     

环己二醇二缩水甘油醚/环氧树脂固化动力学

对E-44环氧树脂,1,2-环己二醇二缩水甘油醚与E-44环氧树脂的混合物,1,2-环己二醇二缩水甘油醚分别与二氨基二苯基甲烷的固化反应应用示差扫描量热仪(DSC)进行了研究。在E-44环氧树脂中加入1,2-环己二醇二缩水甘油醚后,不但对环氧树脂有较好的稀释作用,降低了环氧体系固化反应的表观活化能,增加了环氧树脂的固化反应活性和固化反应速度,还提高了环氧固化物的力学性能。测定了反应热焓,计算出固化反应的表观活化能分别为46.08 kJ/mol,39.50 kJ/mol,35.58 kJ/mol,相应的固化反应级数分别为0.86,0.84,0.83。     

巯基-烯/环氧光-热双重固化体系的制备与表征

通过光引发的巯基-烯点击化学反应和热引发的环氧开环反应制备了以烯丙基环氧树脂(DADGEBA)为基体树脂的巯基-烯/环氧杂化材料。通过实时红外(RT-FTIR)和傅里叶红外光谱(FT-IR)跟踪了双固化反应过程,以及不同官能度硫醇化合物对光聚合反应速率和转化率的影响。采用动态机械热分析(DMA)、热失重分析(TGA)和拉伸性能测试方法对烯丙基环氧树脂的光固化、热固化和光-热双固化3种固化材料的热力学性能和机械力学性能进行了对比研究。结果表明,烯丙基环氧树脂光-热双固化反应结合了光固化和热固化的优点,固化物的拉伸强度可以达到48 MPa,断裂伸长率为15%,玻璃化转变温度(T_g)为68℃,失重5%的热分解温度为343℃。     

硅氧烷改性环氧丙烯酸酯及其紫外-湿气双固化涂层的性能

以环氧树脂和丙烯酸合成环氧丙烯酸酯,再与正硅酸乙酯反应,合成硅氧烷改性的环氧丙烯酸酯。以FT-IR分析合成产物的结构和UV-湿气固化过程;研究UV-湿气双重固化硅氧烷改性环氧丙烯酸酯涂膜的性能。以正硅酸乙酯封闭环氧丙烯酸酯的羟基,使环氧丙烯酸酯的黏度降低82%;经紫外-湿气双重固化,改性环氧丙烯酸酯涂层的摆杆硬度、耐磨性、水接触角均比未改性样品大幅提升,起始热失质量温度比未改性环氧丙烯酸酯高约63℃。     

光产碱型高性能硫醇 -环氧光 -热双重固化涂层的制备及性能研究

针对传统硫醇 -环氧光产碱固化涂层物理机械性能不足的弱点，通过调控 2，4，6-三巯基-s-三嗪（ TTCA）与四（ 3-巯基丁酸）季戊四醇酯（ PE-1）的比例制备了一系列硫醇 -环氧光产碱固化涂层。利用实时红外光谱监测了各涂层体系中巯基及环氧基团的转化率，通过动态力学性能分析（DMA）和拉伸试验测试了固化膜机械性能，同时测试了固化膜的玻璃化转变温度及涂层基本性能。结果表明：随着 TTCA含量的增加，涂层光固化速度呈现一定的下降趋势，但最终光 -热双重固化后固化膜的玻璃化转变温度、力学性能和表面硬度都得到了显著提高。     

非离子水性环氧低温固化剂的制备及固化研究

采用聚乙二醇二缩水甘油醚、双酚A型环氧树脂、脂肪族多胺或芳香族多胺合成了非离子型低温干固化水性环氧同化剂.研究了采用不同种类的多胺制备的固化剂、聚乙二醇二缩水甘油醚含量对固化剂外观、稳定性及固化性能的影响,研究了水性环氧体系的成膜过程及其活化期,讨论了不同的环氧/胺氢固化比例对最终固化性能的影响.     

1,4-Bis(2,3-dicarboxyl-phenoxy)benzene dianhydride-based phenylethynyl terminated thermoset oligoimides for resin transfer molding applications

A series of thermoset oligoimides have been prepared by the thermal polycondensation of 1,4-bis(2,3-dicarboxyl-phenoxy)benzene dianhydride with three different aromatic diamines in the presence of 4-phenylethynylphthalic anhydride as an end capping reagent. The aromatic diamines included 4,4′-oxydianiline, 2,2′-bis(trifluoromethyl)benzidine (TFDB) and 2-phenyl-4,4′-diaminodiphenyl ether (p-ODA). Effects of the chemical structures and molecular weights of the oligoimides on their aggregated structures, melt processability as well as the thermal and mechanical properties of the cured films were then systematically investigated. X-ray diffraction results indicated that ODA series oligoimides and TFDB series oligoimides showed crystallinity; however, the asymmetrical p-ODA enables the p-ODA series oligoimides to exhibit amorphous forms. So the p-ODA based oligoimides with molecular weight of 750 g mol⁻¹ showed much lower melt viscosity at a low temperature and the melt viscosity could maintain below 1 Pa s⁻¹ after isothermal aging for 2 h at any temperature in the range of 220–280 °C by rheological measurements. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47967.     

Biobased epoxy resin from canola oil

Epoxidized canola oil (ECO)‐based thermoset epoxy resins were formulated with phthalic anhydride (PA) as the curing agent for different ratios of ECO to PA (1:1, 1:1.5, and 1:2 mol/mol) at curing temperatures of 155, 170, 185, and 200°C. The gelation process of the epoxy resins and the viscoelastic properties of the systems during curing were studied by rheometry, whereas the dynamic mechanical and thermal properties of the cured resins were studied by dynamic mechanical analysis (DMA) and differential scanning calorimetry. We found that the thermomechanical properties of the resins were not strongly dependent on the curing temperature of the resin, although elevated temperatures significantly accelerated the curing process. However, an increase in the curing agent (PA) amount significantly altered both the reaction rate and the thermomechanical properties of the final resin. Thus, in the ECO/PA system, the selection of the combination of the curing temperature and the molar ratios of the curing agent could be used to design thermoset resins with unique thermomechanical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40142.     

Sequential heat release: an innovative approach for the control of curing profiles during composite processing based on dual‐curing systems

The sequential heat release (SHR) taking place in dual‐curing systems can facilitate thermal management and control of conversion and temperature gradients during processing of thick composite parts, hence reducing the appearance of internal stresses that compromise the quality of processed parts. This concept is demonstrated in this work by means of numerical simulation of conversion and temperature profiles during processing of an off‐stoichiometric thiol–epoxy dual‐curable system. The simulated processing scenario is the curing stage during resin transfer moulding processing (i.e. after injection or infusion), assuming one‐dimensional heat transfer across the thickness of the composite part. The kinetics of both polymerization stages of the dual‐curing system and thermophysical properties needed for the simulations have been determined using thermal analysis techniques and suitable phenomenological models. The simulations show that SHR makes it possible to reach a stable and uniform intermediate material after completion of the first polymerization process, and enables a better control of the subsequent crosslinking taking place during the second polymerization process due to the lower remaining exothermicity. A simple optimization of curing cycles for composite parts of different thickness has been performed on the basis of quality–time criteria, producing results that are very close to the Pareto‐optimal front obtained by genetic algorithm optimization procedures. © 2018 Society of Chemical Industry     

Modification of epoxy–anhydride thermosets with a hyperbranched poly(ester amide). II. Thermal,dynamic mechanical,and dielectric properties and thermal reworkability

An epoxy–anhydride formulation used for the coating electrical devices was modified with a commercially available hyperbranched poly(ester amide), Hybrane S2200, to improve the thermal degradability of the resulting thermoset and, thus, facilitate the recovery of substrate materials after the service life of the component. The thermomechanical, mechanical, and dielectric properties and thermal degradability were studied and interpreted in terms of the composition and network structure of the cured thermosets. Although the crosslinking density was significantly reduced with the incorporation of S2200, the glass transition temperature of the fully cured material (T_g∞) of the modified thermoset was hardly affected because of the enhancement of H‐bonding interactions in the presence of S2200. Despite the different network structures, the combined dielectric and dynamic mechanical analysis revealed that the relaxation dynamics of both networks were very similar. In terms of application, improvements in the dielectric and mechanical properties were observed. The incorporation of S2200 accelerated the thermal decomposition of the material and, thus, facilitated the recovery of the valuable parts from the substrate at the end of the service life of the apparatus. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Bitumen modification with a low-molecular-weight reactive isocyanate-terminated polymer

A low-molecular-weight polyethyleneglycol functionalized with a polymeric MDI (4,4′-diphenylmethane diisocynate) was used as a modifying agent for a 60/70 penetration grade bitumen. The rheological properties of the resulting modified binder, at both low and intermediate temperatures, before and after curing at room temperature were studied and compared with those corresponding to a SBS modified bitumen. The analysis showed that the addition of a small quantity of this reactive polymer leads to enhanced rheological properties mainly at high in-service temperature (50 °C). However, modification was found to be rather slow during binder curing at room temperature. Moreover, storage stability analysis showed that phase separation did not take place after bitumen storage at 163 °C, though storage at high temperature affects the modification capability of the reactive polymer. Atomic force microscopy measurements showed that the reactive polymer addition leads to asphaltene-rich regions with lower thermal susceptibility, which are present even at high temperature, yielding an improved bitumen viscosity in this range of in-service temperatures.     

Improvement of thermal properties of biodegradable polymer poly(3‐hydroxybutyrate) by modification with acryloyloxyethyl isocyanate

Poly(3‐hydroxybutyrate) (PHB) is one type of polyhydroxyalkanoates often used as a biomedical material due to its biodegradable and biocompatible nature. However, the mechanical and thermal properties of PHB must be improved before it can be used in a wider variety of biomedical applications. To improve the thermal properties of biodegradable PHB, various reaction conditions were studied. Results demonstrate that reacting PHB with acryloyloxyethyl isocyanate (AOI), a monomer with dual functional groups, produces a modified PHB material with markedly improved thermal properties. The 10% thermal decomposition temperature for PHB modified with 5% AOI was 297°C, which was 26.8°C higher than original PHB. The T_g also increased from 4°C to around 30°C for AOI‐modified materials. Additionally, due to the poly(ester‐urethane) structure and hydrogen bonding of polymer materials, the mechanical properties also improved. Thus, this modified PHB biodegradable polymer may have greater application as a biomedical material due to its enhanced thermal and mechanical properties. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Polyethylenimine‐Based Shape Memory Polyurethane with Low Transition Temperature and Excellent Memory Performance

Flexible shape memory polyurethanes (SMPUs) are the favorable candidates as a coating or substrate for wearable smart textiles, electronics, and biomedical applications. However, conventional SMPUs (e.g., 1,4 butanediol (BDO)‐based) are not suitable in these applications due to high rigidity, poor mechanical properties, low shape recovery, and high transition temperature. Herein, a polyethylenimine (PEI)‐based SMPU with low transition temperature and tailored properties are reported. The synthesized SMPU are characterized, and their properties are compared with BDO‐SMPUs. The chemical structure of PEI is explored to improve thermal and mechanical properties and to assess their effect on shape memory behavior. The bulky nature of PEI plays a critical role in lowering transition temperature and introduces flexibility in the structure at room temperature. A drop in Young's modulus is found from 13.6 MPa in BDO‐SMPU to 6.2 MPa in PEI‐SMPU. Simultaneously, tensile strength is increased from 3.77 MPa in BDO‐SMPU to 11.85 MPa in PEI‐SMPU. Owing to the improved mechanical properties in PEI‐SMPU, 100% shape recovery is observed, which displays a reproducible trend in ten repetitive cycles due to the presence of reversible physical crosslinks. Therefore, it is envisioned that this can serve as a potential shape memory material in smart wearable technologies.     

Construction of improved isothermal TTT cure diagram based on an epoxy–amine thermoset

Cure degree plays a pivotal role in determining the final properties of thermosetting resin, while the parameter cannot be visually presented by the classic isothermal time–temperature-transformation (TTT) diagram. An improved isothermal TTT cure diagram is built for an epoxy–amine thermoset with the visual relationship between temperature, time, and cure degree during the whole curing. As for the improved isothermal TTT cure diagram, the curing surface and the gelation plane were developed using Vyazovkin method and rheological analysis in turn, and the variation between glass transition temperature (T _g) and curing degree was described by Dibenedetto's equation. The obtained improved isothermal TTT diagram of epoxy–amine thermoset was constructed by the combination of calorimetric and rheological analysis. The fitting results of vitrification surface and gelation plane obtained via improved isothermal TTT diagram were in good agreement with experimental results. In addition, the experimental gelation curve of epoxy–amine thermoset is directly linked to the steepest location of curing surface. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47279.     

Reactive processing of thermoset/thermoplastic blends: A potential for injection molding

Poly(2,6-dimethyl-1,4-phenylene ether) (PPE) is an engineering plastic with high heat distortion temperature. Melt processing of neat PPE is usually accompanied with thermal degradation. The degradation problem is solved by blending with polystyrene to reduce the processing temperature. We propose an alternative using triallylisocyanurate (TAIC). TAIC is a low viscosity liquid that can be cured by peroxide, e.g. α,α′-bis(t-butylperoxy-m-isopropyl)benzene (PBP), to provide a thermoset. The PPE/TAIC mixture was shown to have the upper critical solution temperature (UCST) type phase behavior. At the single-phase regime above UCST and below the cure temperature (∼180°C for PBP), the mixture had a low viscosity, less viscous than a conventional thermoplastic such as PC and PP. That is, a nice window for injection molding was available, e.g., at 100°C to 160°C for a 50/50 blend. After injecting into a hot mold set at cure temperature, the blend cured in a short time (∼80% conversion in 5 min). Then the molded and partly cured material kept its shape and dimensions during post-cure in a hot chamber at higher temperature (e.g. 250°C). Using transmission electron microscopy and dynamic mechanical analyses, it was shown that the cured blend had a bicontinuous two-phase structure with periodic spacings of ∼30 nm, suggesting a structure formation via a spinodal decomposition driven by the increase in molecular weight of TAIC during cure. The cured material showed excellent flexural strength and high chemical resistance.