High-toughness,environment-friendly solid epoxy resins: Preparation,mechanical performance,curing behavior,and thermal properties

The development of a facile and efficient approach to prepare high-toughness epoxy resin is vital but has remained an enormous challenge. Herein, we have developed a high-performance environment-friendly solid epoxy resin modified with epoxidized hydroxyl-terminated polybutadiene (EHTPB) via one-step melt blending. The characterization, mechanical performance, curing behavior, and thermal properties of EHTPB-modified epoxy resin were investigated. EHTPB-modified epoxy resin exhibited excellent toughness with a 100% increase in elongation at break of tensile than that of neat epoxy resin. The transfer stress and dissipated energy in the rubber phase were predominant mechanisms of toughening. The toughening effect of EHTPB on solid epoxy resin was better than that of some of the previously reported liquid epoxy resins. Meanwhile, at 10 wt % of EHTPB loading, the EHTPB-modified epoxy resin displayed high strength and 22 and 101% improvement of flexural strength and impact strength, respectively. Moreover, at 10 wt % of EHTPB loading, the activation energy of EHTPB-modified epoxy resin for curing reaction decreased from 73.89 to 65.12 kJ·mol⁻¹, which is beneficial for the curing reaction. Furthermore, EHTPB-modified epoxy resin had a good thermal stability and the initial degradation temperature increased from 249 to 313 °C at 10 wt % of EHTPB loading. This work provides a simple-preparation and highly efficient and large-scale approach for the production of high-toughness environment-friendly solid epoxy resins. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48596.     

Flame retardant and mechanical properties of epoxy composites with ammonium polyphosphate and hyperbranched silicon-containing polymers

The epoxy resin was mixed with ammonium polyphosphate (APP) and hyperbranched silicon-containing polymers (HBP-B2). The cured composites were investigated by thermogravimetric analysis, Underwriters Laboratory standard for the flammability properties under vertical burning (UL-94V), and limited oxygen index (LOI) test methods. The LOI of 43.5 and could be obtained at the weight ratio of 70:25:5 for the epoxy resin:APP:HBP-B2, Sample A25B5, and the LOI was higher than that of the composite with 30 wt % APP only, Sample A30B0, of which the LOI was 34.5. It suggested that the HBP-B2 could cooperate with the epoxy/APP composite to form a more effective protection layer during combustion, which resulted in a higher second-stage thermal degradation temperature. During the UL-94V test, the flame was extinguished immediately once the burner was removed. Furthermore, the tensile and impact strength of the epoxy/APP composite could also be improved by using HBP-B2 compound as the toughening agent. The composite containing 20% of APP and 10% of HBP-B2, Sample A20B10, still had excellent flame retardant properties with a V-0 rating. Moreover, the tensile strength and impact strength of that composite got 19 and 25% increases compared with the Sample A30B0, which contained 30% of APP only. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48857.     

Modification of epoxy resins by acrylic copolymers with side-chained mesogenic units

A series of acrylic copolymer modifiers with mesogenic side chain (LCGMB) were synthesized and used to modify E-51/DDM system. The dynamic mechanical behavior and impact strength of the modified systems were investigated. The results showed that the impact strength and modulus were influenced by the composition and the amounts of the modifiers. With addition of 10% (wt %) LCGMB (molar ratio of GMA : HEMA : MMA : BA = 4 : 10 : 26 : 60) based on the amount of the epoxy resin, the modified systems obtained 100% increase in impact strength, 10% increase in modulus, and a little increase in Tg. The toughening mechanism of the modified systems was also discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1787–1792, 1999     

新型增韧阻燃环氧树脂胶黏剂的研究

采用以聚氨酯（PU）增韧改性环氧树脂为基体,在其中添加两次包覆红磷作为阻燃剂,从而制备出一种新型增韧阻燃环氧树脂胶黏剂。通过对所制得胶黏剂进行力学性能测试、热失重测试（TG）以及阻燃性能测试,从而研究了聚氨酯和两次包覆红磷用量对改性环氧树脂胶黏剂性能的影响。结果表明,采用100份环氧树脂、30份聚酯型聚氨酯预聚体、15份阻燃剂,可制备出综合性能较好的增韧阻燃环氧树脂胶黏剂,剪切强度为23．2MPa,氧指数可达到30％。     

Epoxidized Mesua ferrea L. seed oil-based reactive diluent for BPA epoxy resin and their green nanocomposites

An epoxidized vegetable oil of Mesua ferrea L. seed was prepared and used as a reactive diluent for commercial BPA-based epoxy resin at different compositions for the first time. The prepared epoxidized oil (ENO100) was characterized by determination of physical properties like epoxy equivalent, viscosity, hydroxyl value, saponification value, iodine value, acid value, etc. and FTIR study. The morphology and rheological characteristics of the ENO100 modified commercial epoxy systems have been studied by SEM and rheometer. The performance of poly(amido amine) cured above resin systems have been investigated by the measurement of drying time, tensile strength, elongation at break, adhesive strength, impact resistance, scratch hardness, gloss and chemical resistance studies. The results indicate that the epoxidized oil not only reduces the viscosity of the BPA-based epoxy resin but it also enhances the performance of the cured resin. The performance of this system (50 wt.% dilution) was further enhanced by formation of nanocomposites using ex-situ technique with organically modified nanoclay at different dose levels (1–5 wt.%).The formation of nanocomposites was confirmed by XRD, SEM and FTIR studies. The studies of above performance indicate the enhancement of properties compared to pristine system. As naturally renewable diluent is used in the above studies, so the resultant nanocomposites are green high performance materials with zero VOC.     

一种高韧性耐湿性环氧树脂的合成及其性能研究

利用β-甲基环氧氯丙烷与双酚A在氢氧化钠的存在下合成了一种新的甲代双酚A型缩水甘油醚环氧树脂(BPA-MECH EP)预聚物,并通过FT-IR、1H NMR、GPC等手段对产物结构进行了表征。用盐酸-丙酮滴定法测定其环氧值为0.43 mol/100 g。用DDM作固化剂,利用DSC对其添加量为树脂质量的20%时体系的固化反应动力学以及最佳固化工艺条件进行了探讨。实验结果表明:BPA-MECH/DDM固化体系的反应级数n为1.30;表观活化能为15.37 kJ/mol;最佳固化工艺条件为:120℃/1 h→140℃/1 h→175℃/3 h→200℃/1 h逐步阶段升温固化。与E-44的DDM固化物进行了性能比较,结果表明:BPA-MECH与E-44固化产物的热变形温度无显著差别,但吸水率降低了47.6%,弯曲强度和弯曲模量分别提高了10.5%和7.8%,冲击强度上升了129.4%,拉伸强度、弹性模量以及断裂伸长率都有不同程度的提高,最大增幅分别为27.6%、25.9%和12.9%。研究结果表明,甲代双酚A型缩水甘油醚环氧树脂是一种性能优良的环氧树脂预聚物。     

聚醚砜改性环氧树脂的研究

研究了聚醚砜在环氧树脂及各类溶剂中的溶解性能;通过对涂层附着力、柔韧性的比较,研究了聚醚砜添加量对环氧树脂的增韧改性效果,比较了增韧改性环氧树脂涂层的抗空蚀性能。结果表明:聚醚砜在环氧树脂及强极性溶剂中具有较好的溶解性;聚醚砜能明显改善环氧树脂的柔韧性,且其加入量为20%~25%时增韧效果较好,此时增韧改性环氧涂层的抗空蚀性能相对较好。     

Bio-based epoxy/polyaniline nanofiber-carbon dot nanocomposites as advanced anticorrosive materials

Application of anticorrosive coating on metal surface enhances the durability of the metal. Anticorrosion can be achieved by the incorporation of conducting nanomaterials like polyaniline or its nanohybrid to a coating material. Thus, bio-based epoxy nanocomposites were fabricated by the in situ method using polyaniline nanofiber-carbon dot nanohybrid (0.50 and 1 wt % with respect to epoxy), as the anticorrosive material. The epoxy resin was obtained by polycondensation of bisphenol-A, sorbitol, and monoglyceride of castor oil (mole ratio of 16:3:1), as hydroxyl compounds with epichlorohydrin (1:3 equivalent, hydroxyl:epichlorohydrin). The morphological analyses of the nanocomposites revealed the uniform dispersion and good compatibility of the nanohybrid in the epoxy matrix. The thermosets demonstrated good tensile strength (30 MPa), elongation at break (45%), scratch resistance (>10 kg) and impact resistance (14.75 kJ/m), good thermal stability (above 250°C), and chemical resistance. The anticorrosion study of the nanocomposites showed excellent corrosion protection efficiency (corrosion rate: 5.68 × 10⁻³ mils per year) in 3.5 wt % NaCl compared to the pristine epoxy system. Therefore, this bio-based thermosetting epoxy nanocomposite was demonstrated as efficient anticorrosive material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47744.     

Urethane foams from animal fats: VIII. Properties of foams from epoxidized tallow trimethylolpropane polyols

Polyols made by reacting trimethylolpropane with epoxidized tallow were converted to urethane foams by reaction with a polymethylene polyphenylisocyanate in the presence of fluorotrichloromethane. Adjusted with triisopropanolamine or an oxypropylated triamine to hydroxyl equivalent of either 100 or 120, the polyols yielded rigid foams of density 1.5–2.0 lb/ft³, open cell content 15–19%, and compressive strength 34–49 psi. These values were superior to those of similar foams from hydrated epoxidized tallow. Polyols made from epoxidized tallow-trimethylolpropane-HBr and adjusted to equivalent wt of 100 and 120 by triisopropanolamine gave foams whose small-scale flammability test samples burned less than 20% of their length. At hydroxyl equivalent 100, foams had density 1.6–1.8, open cell content 20–21%, and compressive strength 34–39 psi; in flammability tests burned <20% of length. The present foams were stronger than those made earlier from solvent-purified hydroxybrominated tallow. Formulation with half the normal amount of freon gave foams of higher compressive strength but lower flame resistance.     

Mechanical properties of an epoxy resin toughened by polyester

The epoxy resins were toughened by 4–24 phr polyester with average molecular weight 1.9×10⁴ g/mol in this investigation. The mechanical properties were examined and dynamic mechanics analyses were performed for the epoxy resins before and after the modification. The toughening mechanism of polyester to epoxy resin is discussed in light of the scanning electronic microscopy observation of the fracture surfaces. The results showed that the impact strength and tensile strength of the modified epoxy resin were remarkably greater than those of the unmodified cured epoxy resin. The most suitable composition for the modified epoxy resin was the addition of 16 phr polyester, which led to 138 and 46% increments in the impact strength and the tensile strength, respectively. And the mechanical properties depended greatly on the congregating state of polyester added. The polyester dispersing in the epoxy matrix was amorphous when its addition was less than or equal to 12 phr, and was sphere crystals when the addition was over 16 phr. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3384–3389, 2003     

Influence of Submicron TiO2 Particles on the Mechanical Properties and Fracture Characteristics of Cured Epoxy Resin

Submicron titanium dioxide (TiO₂) was used in different weight fractions as a toughening agent for amine-cured epoxy resin. After the use of X-ray photoelectron spectroscopy (XPS), which confirmed that the TiO₂ particles were evenly distributed in the cross-linked epoxy resin matrix, the composites were characterized by tensile and impact testing, followed by scanning electron microscopy of the fracture surfaces. The results indicated that the submicron TiO₂ toughening particles markedly improved the mechanical properties of the cured epoxy resin compared to the untoughened epoxy resin. The optimal properties were achieved at a TiO₂ concentration of 4 wt. %, at which point the toughness and the impact resistance values increased by 65% and 60%, respectively. The results also indicated that an increase in the amount of TiO₂ causes a decrease in toughness. Stress whitening, out-of-plane flaking, and thumbnail markings were the major visible features of the toughening mechanisms.

It is suggested that, at 4 wt. % of the submicron TiO₂ particles, microvoids are developed in the epoxy matrix. These microvoids are able to absorb some of the deformation work applied to the material, and thus enhance the toughness of the material. On increasing the TiO₂ content in the matrix (> 4 wt. %), the submicron particles got closer to each other and the microvoids were converted to macrovoids, which may act as stress concentrating flaws, leading to the deterioration of the mechanical properties of the epoxy resin.     

Toughening of aromatic diamine-cured trifunctional epoxy resins by modification with N-phenylmaleimide–styrene copolymers containing pendant p-hydroxyphenyl groups

N-Phenylmaleimide (PMI)–N-(p-hydroxy)phenylmaleimide (HPMI)–styrene (St) terpolymers (HPMS), containing pendant p-hydroxyphenyl (HP) groups, were prepared and used to improve the toughness of triglycidyl aminocresol epoxy resin cured with p,p′-diaminodiphenyl sulfone. HPMS was effective as a modifier for the toughening of the epoxy resin. When using 15 wt % of HPMS (1.0 mol % HP unit, M_w 129,000), the fracture toughness (K_IC) for the modified resin increased 190% with a medium loss of flexural strength. The toughening of epoxies could be attained because of the cocontinuous phase structure of the modified resins. The decrease in flexural strength was suppressed to some extent by introducing a functional group into the modifier. The toughening mechanism was discussed in terms of the morphological behavior of the modified epoxy resin system. © 1995 John Wiley & Sons, Inc.     

五氧化二磷改性水性环氧树脂的合成及性能

为获得具有良好表面活性的水性环氧树脂,采用五氧化二磷为磷酸化试剂对环氧树脂进行改性,并对此磷酸化工艺过程进行优化。从反应投料比、时间、温度等主要因素考察了反应条件对产物环氧值和单双酯含量的影响,确定了较佳的反应条件：反应投料摩尔比n（E20）∶n（P2O5）=1.2∶1,反应时间为3 h,反应温度为85 ℃。此工艺条件下制备产物的环氧值为0.057 mol/100 g,单酯含量为0.44 %,双酯含量为0.56 %。使用红外光谱仪、核磁共振谱仪对改性环氧树脂的结构进行了表征,并对其热稳定性、乳液的黏温、黏浓特性、粒径及表面活性进行了测试。结果表明,改性后样品的分子结构中有部分环氧键断裂,同时有磷酸单双酯官能团的出现,说明合成了新的产物;改性环氧树脂的热稳定性较好;乳液的平均粒径较小;乳液质量分数低于10 %时,其黏度几乎不受质量分数的影响,具有较好的表面活性;乳液质量分数为0.5 %时,乳液的表面张力最小。     

Toughening of semi-IPN structured epoxy using a new PEEK-type polymer via in situ azide–alkyne click polymerization

A new poly(ether ether ketone)-type polymer prepared from 1,4-bis(azidomethyl)benzene (p-BAB), 4,4′-bis(2-propynyloxy)benzophenone (PBP) or 4,4′-sulfonylbis(propynyloxy)-benzene (SBP) via azide–alkyne click polymerization was used as a toughening agent to improve the fracture toughness, thermal stability of the toughened epoxy and reduce its viscosity during processing. The epoxy was toughened by the polymer [poly(p-BAB/PBP)] via in situ polymerization during the curing process, which largely decreased viscosity during the epoxy mixing process compared to that of a neat epoxy. The fracture toughness of 5 wt % poly(p-BAB/PBP) toughened epoxy is two times higher than that of the neat epoxy, and even higher than that of the polyethersulfone-type [poly(p-BAB/SBP)] toughened epoxy using the same amount of toughening agents. In addition, the T _g of this toughened epoxy is higher than that of engineering plastic, which could be regarded as the evidence for the excellent thermal resistance. These phenomena might be attributed to the formation of semi-interpenetrating polymer networks composed by the epoxy network and the linear poly(p-BAB/PBP). In situ poly(p-BAB/PBP) has unique advantages such as decreased viscosity and improved thermal stability in comparison with in situ poly(p-BAB/SBP). These features are significant for the development of carbon-fiber-reinforced plastics as alternate materials to metals. Therefore, in situ poly(p-BAB/PBP) is a promising toughener for epoxy systems. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48178.     

新型环氧大豆油增韧酚醛树脂的合成与性质

A novel epoxidized soybean oil-toughened-phenolic resin（ESO-T-PR）has been synthesized by etheri- fication graft and multi-amine curing ESO.Fourier transform infrared spectroscopy（FTIR）was adopted to investi- gate its molecular structure and scan electron microscope（SEM）was used to observe the micro morphology of its impact fracture surface.This ESO-T-PR was adopted as the matrix resin to prepare paper copper clad laminate （P-CCL）and the properties of resulting P-CCL are found superior to the related Chinese National Standard.The toughing mechanism was investigated by comparing the impact strength,solderleaching resistance,flexural strength, peeling strength and morphology of this ESO-T-PR with those of other two ESO modified phenolic resins.It is demonstrated that during the synthesizing process of ESO-T-PR,the phenol hydroxyl is etherified by ESO or ESO epoxy resin prepolymer（ESO chain extension polymer）and the long ESO epoxy resin chain segments enhance the crosslink density of ESO-T-PR and consequently improve the impact toughness and solderleaching resistance of P-CCL made of ESO-T-PR.The ESO-T-PR is a cheap matrix resin with excellent properties to make P-CCL（elec- tric guide board）.     

Toughening mechanisms of rubber modified thin film epoxy resins

An epoxy terminated polybutadiene (ETPB) was synthesized and utilized to enhance the toughening of an epoxy system, in both bulk and coating states. In the first step, the fracture energy of the modified samples was determined using a single edge notched type specimen in a three point bending (SEN3PB) geometry. The effective toughening mechanisms of bulk epoxy specimens were examined using scanning electron microscopy (SEM). The results showed that plastic void growth, cavitation and shear yielding mechanisms were the main toughening mechanisms of the bulk epoxy systems. In the next step, mechanical properties (i.e. impact resistance, flexibility, cupping resistance and hardness) and adhesion of the thin film specimens were evaluated in accordance to the amount of synthesized ETPB. The results showed that the mechanical properties of the ETPB modified epoxy resins considerably improved. In all cases, it was found that the improvement of the mechanical properties reached a maximum at 7.5 wt.% and then began to decrease with further increase in ETPB content. The effective toughening mechanisms in the modified thin films were also examined using SEM and compared to the bulk types. In contrast to the bulk types, the results showed that crack arresting and shear yielding were active mechanisms in thin films. The contribution of these mechanisms led to the improvement of adhesion and mechanical properties by energy dissipation.     

快速固化环氧树脂胶黏剂的研究

介绍了一种新型快速固化环氧胶黏剂的研制过程及其性能。选用不同固化剂和增韧剂,以及通过调整固化剂和增韧剂的添加量,对胶黏剂配方进行了优选。在固化工艺方面,研究了固化剂含量和固化温度对于凝胶时间的影响。当增韧剂Q含量在15—20份(质量)时,固化剂在21—24份(质量)时,胶黏剂的剪切强度和剥离强度最佳。结果表明,所研制的胶黏剂具有良好的耐湿热老化和耐介质性能,该胶黏剂同时具有胶接强度高和固化工艺方便的优点。     

聚氨酯改性室温固化环氧结构胶粘剂的研究

采用聚氨酯预聚体改性环氧树脂,制备了高性能室温固化环氧结构胶粘剂,研究了聚氨酯预聚体加入量对环氧结构胶剪切强度、冲击强度和拉伸强度等指标的影响,利用扫描电镜(SEM)对环氧胶固化物的冲击断裂面进行了分析。结果表明,聚氨酯预聚体的加入可显著提高环氧胶粘剂的韧性。采用NCO质量分数为3.86%的甲苯二异氰酸酯/聚醚多元醇预聚体(TDI/N220)改性环氧树脂,加入量为20 g/(100 g环氧树脂)时,环氧结构胶粘剂的综合性能最佳,剪切强度为20.8 MPa,冲击强度为44.2 kJ/m2,拉伸强度为17.4 MPa。     

Investigation of mechanical properties of graphene decorated with graphene quantum dot-reinforced epoxy nanocomposite

In this investigation, the mechanical properties such as compression, impact, and flexural properties of graphene decorated with graphene quantum dots (GDGQD) epoxy composites with concentration of GDGQD ranging from 0.25 to 1 wt % were studied. Ideal mechanical properties are obtained by systematically varying the filler weight in the epoxy matrix. The morphological studies of GDGQD have been characterized using transmission electron microscope, X-ray diffraction, and Fourier transform infrared technique. The compression, impact, and flexural strengths were enhanced effectively by the GDGQD loading. With the addition of 0.75 wt % of GDGQD, the compressive strength, compressive modulus, flexural strength, and flexural modulus of the composites were improved by 22, 29, 31, and 63%, respectively. Also an improvement in impact strength of 102% for 0.75 wt % GDGQD epoxy sample was also obtained. Examination of fractured test specimens was performed with scanning electron microscope. The enhancement in the mechanical properties is due to the better stress transfer that is attributed by enhanced interfacial bonding between GDGQDs and the epoxy. Using the GDGQD aspect ratio in the two-dimensional randomly oriented filler modified Halpin–Tsai model, the theoretical flexural modulus for the GDGQD/epoxy composites has been established. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48680.     

Effect of graphene and CNT reinforcement on mechanical and thermomechanical behavior of epoxy—A comparative study

Graphene‐nanoplateles (Gr) and multiwalled carbon nanotubes (CNTs) reinforced epoxy based composites were fabricated using ultrasonication, a strong tool for effective dispersion of Gr/CNTs in epoxy. The effect of individual addition of two different nanofillers (Gr and CNT) in epoxy matrix, for a range of nanofiller content (0.1–1 wt %), has been investigated in this study. This study compares mechanical and thermomechanical behavior of Gr and CNT reinforced epoxy. Gr reinforcement offers higher improvement in strength, Young's modulus, and hardness than CNT, at ≤0.2 wt %. However, mode‐I fracture toughness shows different trend. The maximum improvement in fracture toughness observed for epoxy‐Gr composite was 102% (with 0.3 wt % loading of Gr) and the same for epoxy‐CNT composite was 152% (with 0.5 wt % loading of CNT). Thorough microstructural studies are performed to evaluate dispersion, strengthening, and toughening mechanisms, active with different nanofillers. The results obtained from all the studies are thoroughly analyzed to comprehend the effect of nanofillers, individually, on the performance of the composites in structural applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46101.