An epoxy‐ended hyperbranched polymer as a new modifier for toughening and reinforcing in epoxy resin

A new epoxy‐ended hyperbranched polyether (HBPEE) with aromatic skeletons was synthesized through one‐step proton transfer polymerization. The structure of HBPEE was confirmed by Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR) measurements. It was proved to be one high efficient modifier in toughening and reinforcing epoxy matrix. In particular, unlike most other hyperbranched modifiers, the glass transition temperature (T_g) was also increased. Compared with the neat DGEBA, the hybrid curing systems showed excellent balanced mechanical properties at 5 wt % HBPEE loading. The great improvements were attributed to the increased cross‐linking density, rigid skeletons, and the molecule‐scale cavities brought by the reactive HBPEE, which were confirmed by dynamical mechanical analysis (DMA) and thermal mechanical analysis (TMA). Furthermore, because of the reactivity of HBPEE, the hybrids inclined to form a homogenous system after the curing. DMA and scanning electron microscopy (SEM) results revealed that no phase separation occurred in the DGEBA/HBPEE hybrids after the introduction of reactive HBPEE. SEM also confirmed that the addition of HBPEE could enhance the toughness of epoxy materials as evident from fibril formation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1064‐1073, 2013     

Improved thermosets obtained from diglycidyl ether of bisphenol A/4,4′‐diaminodiphenylsulfone based on a new epoxy‐terminated hyperbranched polymer

A new hyperbranched polymer (HBP) with a flexible aromatic skeleton and terminal epoxy groups was synthesized to improve the toughness of diglycidyl ether of bisphenol A. The HBP was characterized using nuclear magnetic resonance, Fourier transfer infrared spectroscopy and gel permeation chromatography. The effect of HBP on the thermomechanical and mechanical properties of modified epoxy systems was studied. For evaluating the efficiency of the modified epoxy systems, composite samples using glass fiber cloth were molded and tested. Using dynamic mechanical analysis, a slight reduction in glass transition temperature (T_g) with increasing HBP content was observed. Analysis of fracture surfaces revealed a possible effect of HBP as a toughener and showed no phase separation in the modified resin systems. The results showed that the addition of 15 phr HBP maximized the toughness of the modified resin systems with 215 and 40% increases in impact and flexural strengths, respectively. T_g and heat resistance of cured modified resin systems decreased slightly with an increase in HBP content and, at 15 phr HBP, only a 2.6% decrease in thermomechanical properties was observed. Meanwhile, a molded composite with HBP showed improved mechanical properties and retention rate at 150 °C as compared to that made with neat resin. © 2015 Society of Chemical Industry     

超支化聚合物在环氧树脂中的应用

综述了超支化聚合物在环氧树脂中的应用,简述了超支化环氧树脂、超支化环氧树脂固化剂和超支化环氧树脂添加剂的合成及应用进展,展望了其研究前景。     

超支化环氧树脂的研究进展及应用

从超支化聚合物出发,重点总结了超支化环氧树脂(EP)独特的结构特点、四种合成方法及优缺点,综述了目前超支化EP合成的新思路、超支化EP的应用、发展方向以及存在的问题。     

超支化聚合物改性环氧树脂的研究进展

超支化聚合物因其独特的结构和性能特点,已在众多领域得到了广泛的应用,尤其是在热固性树脂的改性中的应用,可作为热固性树脂的增韧剂。该文介绍了环氧树脂的性能特点及应用,超支化聚合物的结构及特点,着重论述了近年来超支化聚合物在改性环氧树脂力学性能、固化行为及热性能方面的研究进展,并指出了超支化聚合物在环氧树脂和其它热固性树脂改性方面的发展方向。     

Highly efficient in situ toughening of epoxy thermosets with reactive hyperbranched polyurethane

Hyperbranched polyurethane (HBPU), with low‐molecular‐weight polyethylene glycol space segments between the branching points, was synthesized by a pseudo one‐pot procedure. HBPU was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and gel permeation chromatography. The HBPU was used as a modifier of diglycidyl ether of bisphenol A (DGEBA)/anhydride system. The rheological properties of HBPU‐G3/DGEBA blends were investigated by rotational rheometer. A slight decrease in viscosity of modified blends was observed by adding low content of HBPU and there was chemical reaction between HBPU and epoxy resin even without a hardener. The mechanical and thermal properties of the HBPU‐G3/DGEBA thermosets were characterized and compared with that of the neat epoxy thermosets. Their impact fracture surfaces were investigated by scanning electron microscopy, and the results indicated that no phase separation occurred in the DGEBA/anhydride system after the introduction of HBPU, which was confirmed by dynamic mechanical analysis and thermogravimetric analysis. After addition of 10 wt % HBPU, the toughness of the modified thermosets was found to be significantly improved without sacrificing their processability and thermal and mechanical properties to a large extent. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40614.     

Toughness and strength improvement of diglycidyl ether of bisphenol‐A by low viscosity liquid hyperbranched epoxy resin

This article reports on the use of low viscosity liquid thermosetting hyperbranched poly(trimellitic anhydride‐diethylene glycol) ester epoxy resin (HTDE) as an additive to an epoxy amine resin system. Four kinds of variety molecular weight and epoxy equivalent weight HTDE as modifiers in the diglycidyl ether of bisphenol‐A (DGEBA) amine systems are discussed in detail. It has been shown that the content and molecular weight of HTDE have important effect on the performance of the cured system, and the performance of the HTDE/DGEBA blends has been maximum with the increase of content and molecular weight or generation of HTDE. The impact strength and fracture toughness of the cured systems with 9 wt % second generation of HTDE are 58.2 kJ/m² and 3.20 MPa m^1/2, which are almost three and two times, respectively, of DGEBA performance. Furthermore, the tensile and flexural strength can be enhanced about 20%. The glass transition temperature and Vicat temperature, however, are found to decrease to some extent. The fracture surfaces are evaluated by using scanning electron microscopy, which showed that the homogeneous phase structure of the HTDE blends facilitates an enhanced interaction with the polymer matrix to achieve excellent toughness and strength enhancement of the cured systems, and the “protonema” phenomenon in SEM has been explained by in situ reinforcing and toughening mechanism and molecular simulation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2504–2511, 2006     

Bisphenol-A epoxy resin reinforced and toughened by hyperbranched epoxy resin

The study on toughening and reinforcing of bisphenol-A epoxy resin is one of important developmental direction in the field. This paper reports a one-pot synthesis of aromatic polyester hyperbranched epoxy resin HTDE-2, an effect of HTDE-2 content on the mechanical and thermal performance of the bisphenol-A (E51)/HTDE-2 hybrid resin in detail. Fourier transform infrared (FT-IR) spectrometer, scanning electronic microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMA) and molecular simulation technology are used to study the structure of HTDE-2, performance and toughening and reinforcing mechanism of the HTDE-2/E51 hybrid resin. It has been shown that the content of HTDE-2 has an important effect on the performance of the hybrid resin, and the performance of the HTDE-2/E51 blends has maximum with the increase in HTDE-2 content. The impact strength and fracture toughness of the hybrid resin with 9 wt-% HTDE-2 are almost 3.088 and 1.749 times of E51 performance respectively, furthermore, the tensile and flexural strength can also be enhanced about 20.7% and 14.2%, respectively. The glass transition temperature and thermal degradation temperature, however, are found to decrease to some extent. __________ Translated from Journal of South China University of Technology (Natural Science Edition), 2006: 34(9): 90–94 [译自: 华南理工大学学报 (自然科学版)]     

A thiol‐ene clickable hyperbranched polyester via a simple single‐step melt trans‐esterification process

Self‐condensation of AB₂ type monomers (containing one A‐type and two B‐type functional groups) generates hyperbranched (HB) polymers that carry numerous B ‐type end‐groups at their molecular periphery; thus, development of synthetic methods that directly provide quantitatively transformable peripheral B groups would be of immense value as this would provide easy access to multiply functionalized HB systems. A readily accessible AB₂ monomer, namely diallyl, 5‐(4‐hydroxybutoxy)isophthalate was synthesized, which on polymerization under standard melt‐transesterfication conditions yielded a peripherally clickable HB polyester in a single step; the allyl groups were quantitatively reacted with a variety of thiols using the facile photoinitiated “thiol‐ene” reaction to generate a wide range of derivatives, with varying solubility and thermal properties. Furthermore, it is shown that the peripheral allyl double bonds can also be readily epoxidized using meta‐chloroperoxybenzoic acid to yield interesting HB systems, which could potentially serve as a multifunctional cross‐linking agent in epoxy formulations. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40248.     

Six‐arm star‐shaped polymer with cyclophosphazene core and poly(ε‐caprolactone) arms as modifier of epoxy thermosets

A six‐arm star‐shaped poly(ε‐caprolactone) (s‐PCL) based on cyclophosphazene core was obtained by presynthesis of a hydroxy‐teminated cyclophosphazene derivative and subsequent initiation of the ring‐opening polymerization of ε‐caprolactone, and its use in different proportions as toughening modifier of diglycidylether of bisphenol A/anhydride thermosets was studied. The star‐shaped polymer was characterized to have approximately 30 caprolactone units per arm. Differential scanning calorimetry revealed a nonsignificant influence on the curing process of the epoxy‐anhydride formulation by the addition of s‐PCL. The s‐PCL‐modified epoxy thermosets exhibited a great improvement in both toughness and strength compared with the neat resin, as the result of a joint effort by the internal rigid core and the external ductile polyester chains of s‐PCL. When the addition of the modifier was 3 wt %, an optimal mechanical and thermomechanical performance was achieved. The impact resistance and tensile strength of the cured epoxy resin were enhanced by 150% and 30%, respectively. The glass transition temperature was also increased slightly. Moreover, the addition of the star‐shaped modifier had little harmful effect on the thermal stability of the material. Thus s‐PCL was proved to be a superior toughening agent without sacrificing thermal and mechanical properties of the thermosets. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44384.     

端羧基超支化聚酯改性环氧树脂固化体系研究

利用丁二酸酐对端羟基超支化聚酯(AHBP)的端基进行改性,得到新的端羧基超支化聚酯(CHBP),并将其用于环氧树脂体系的增韧。研究了CHBP用量、羧基含量对环氧树脂/甲基四氢苯酐(EP/MeTHPA)固化体系的力学性能和热性能的影响。结果表明,改性后分子末端全部带羧基的CHBP的增韧作用最好,冲击强度可达18.5kJ/m2。CHBP质量分数为15%时,固化物的冲击强度可达18.2 kJ/m2,拉伸强度64.86 MPa,玻璃化温度(Tg)从100℃提高到106℃左右,可满足增韧环氧树脂的同时不降低其耐热性的要求。     

Rubber-toughening epoxy thermosets with epoxidized crambe oil

Epoxidized crambe oil and rapeseed oil were synthesized by reaction of the oils with m-chloroperoxybenzoic acid. Formulating the neat epoxidized oils with epoxy-amine systems gave two-phase thermosets with epoxidized crambe oil, but not with epoxidized rapeseed oil. Glass transition temperature, mechanical properties, and fracture toughness of the epoxidized crambe oil thermoset specimen were measured. Fracture toughness values of the epoxy thermosets were increased approximately 100% by both 5 and 10% epoxidized crambe oil. Glass transition temperature and mechanical properties were affected only modestly.     

Toughening of an epoxy anhydride resin system using an epoxidized hyperbranched polymer

This paper reports on the use of an epoxidized hyperbranched polymer (HBP) as an additive to an epoxy anhydride resin system. The hyperbranched polymer used was an aliphatic polyester with a molecular weight of around 10 500 g mol^?1. The epoxy resin mixture used was a combination of a difunctional diglycidyl ether of bisphenol A (DGEBA) epoxy and an epoxy novolac, and was cured with a catalysed anhydride curing agent. It has been shown that, at a concentration range of 0 to 20 wt% addition, the HBP is able to almost double the fracture toughness, with little evidence of any deleterious effects upon processing and the durability of the cured resin system. The flexural modulus and stress, however, were found to both decrease by about 30% as a result of HBP addition while the T_g was found to decrease by about 10%. The processability of the uncured resin systems has been investigated by using rheological and calorimetric techniques and it was found that the processability window, as determined by the gel time and viscosity changes, was relatively unaffected by HBP addition. The fracture surfaces were evaluated by using scanning electron microscopy which showed that the unique structure of the HBP facilitates an enhanced interaction with the polymer matrix to achieve excellent toughness enhancement of the polymer matrix. The durability of the epoxy network has been investigated via thermogravimetric analysis (TGA) and solvent uptake, and the HBP has been shown to have little systematic deleterious effect upon the degradation temperatures and the total amount of solvent absorbed. Copyright © 2003 Society of Chemical Industry     

新型脂肪族超支化环氧树脂的制备及其改性作用

采用一步法合成了新型脂肪族超支化环氧树脂HTPE-3,利用FT-IR对其结构进行了表征。研究了双酚A型环氧树脂E-51/HTPE-3杂化树脂的力学性能和热性能。结果显示,杂化树脂的韧性和强度随HTPE-3含量的增加先增加后降低,具有极大值;当HTPE-3质量分数为12%左右时,与纯E-51树脂相比,杂化树脂的冲击强度和断裂韧性分别提高了169.8%和35.2%,拉伸强度和弯曲强度分别提高了6.5%,10.0%,维卡软化点温度、玻璃化转变温度和热分解温度略有下降。     

Preparation of epoxy‐ended hyperbranched polymers with precisely controllable degree of branching by thiol‐ene Michael addition

Epoxy‐ended hyperbranched polymers (EHPs) have a wide range of applications due to their outstanding performances. Because their microstructures are not positively identified, it is very difficult to ascertain the reinforcing and toughening mechanisms of EHPs and their interface interaction with other matrixes. Controllable synthesis of EHPs with precise degree of branching (DB) remains to be a major challenge. Here, a method for preparing novel nitrogen‐phosphor skeleton epoxy‐ended hyperbranched polymers (NPEHP) with controllable DB by a thiol‐ene Michael addition between thiol‐ended hyperbranched polymers (NPHSH) and glycidyl methacrylate have been firstly reported. NPHSH is synthesized by an esterification between hydroxyl‐ended hyperbranched polymers (NPHOH) and 3‐mercaptopropionic acid. NPHOH is prepared by a thiol‐ene Michael addition between methacrylate group of a monomer and thiol group of linear monomer (AB) and/or branched monomer (AB₂). The molar ratio between the AB and AB₂ monomers controls the DB of the products. The ¹H NMR spectra analysis of NPHOH shows that their experimentally determined DBs are very close to their theoretical values, indicating good controllability of their DBs. The narrow molecular weight distributions of NPHOH, NPHSH, and NPEHP suggest high efficiency of the thiol‐ene Michael addition. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44277.     

低黏度高分子质量超支化环氧树脂的合成及性能

利用一步法合成了低黏度高分子量的第四代芳香族超支化环氧树脂HTDE-4,该种树脂能作为环氧树脂的稀释剂。将HTDE-4与双酚A型环氧树脂杂化复合,研究其固化物的机械性能。杂化树脂的性能随超支化环氧树脂含量的增加先增加后下降;当用量为12%(质量分数)左右时,体系的拉伸强度、弯曲强度、冲击强度和断裂韧性分别提高15.6%,14.8%,158.9%和36.9%,断裂韧性达到2.78 kPa.m1/2。用傅里叶变换红外光谱和核磁共振氢谱、扫描电镜和分子模拟技术对产物进行了研究。     

Superiority of nanosized over microsized hyperbranched polymer second phase in modifying brittle epoxy resin

A hydroxyl‐functionalized hyperbranched polymer (HBP, H30) is used to modify 4,4′‐diaminodiphenylsulfone‐cured bisphenol‐A type epoxy resin and a separate phase structure of modified epoxy resins is observed. The effects of the H30 second phase size on the mechanical properties of modified epoxy systems are investigated systematically. The dependence of the toughening mechanisms on the HBP particle size is reported for the first time. It is shown that the nanosized H30 second phase is superior over microsized counterparts in modifying brittle epoxy resin. The tensile strength is slightly enhanced by the introduction of nanosized H30 second phase, whereas the strength is significantly reduced by the addition of microsized H30 phase. The failure strain and impact strength are obviously enhanced by the introduction of nanosized H30 second phase at low contents, whereas these properties are reduced by the addition of microsized H30 second phase at high contents. Finally, differential scanning calorimetric and thermogravimetric analyses are conducted to examine the effects of the HBP content on the glass transition temperature and the thermal stability, respectively. The glass transition temperature is slightly reduced while the thermal stability is not obviously influenced by the introduction of H30 second phase. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A novel method for preparation of epoxy resins using thiol–ene click reaction

Epoxy resins (EPs) have a wide range of applications due to their remarkable performances. A major issue about them is the associated serious environmental pollution and high manufacturing cost because of the tedious synthetic procedure and the large amount of organic solvents used in production. Here, we report a facile, highly efficient approach to addressing these challenges using thiol–ene click reaction. The new synthesis process is based on mass‐produced materials including triols, diols, mercaptopropionic acid and glycidyl methacrylate and involves only two steps, that is, esterification and thiol–ene click reaction. Three types of high purity sulfur‐containing EPs are synthesized at high yields. The chemical structures and molecular weights of the newly synthesized EPs were characterized by Fourier translation infrared spectroscopy, ¹H‐NMR and matrix‐assisted laser desorption/ionization time of flight mass spectrometry. Using the methyl nadic anhydride as crosslinker, these resins have shown excellent heat‐resistance due to the absence of hydroxyl groups. They demonstrate high thermal decomposition temperatures, showing no dehydration decomposition at 260°C and therefore are suitable for applications as solvent‐free resins. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42316.     

Incorporation of hyperbranched polyamide‐functionalized graphene oxide into epoxy for improving interfacial and mechanical properties

The incorporation of hyperbranched polyamide‐functionalized graphene oxide (HPA‐GO) into epoxy was proposed to improve the interfacial and mechanical properties. Benefiting from improved dispersion and strengthened interfacial interaction, epoxy composites with HPA‐GO showed significant improvements in mechanical and thermomechanical properties at low GO loading. The interaction at the HPA‐GO/epoxy interface was investigated to confirm the occurrence of chemical bonding. Strong interfacial bonding improved the stress transfer and distribution of HPA‐GO/epoxy interface. Accordingly, the overall strength of epoxy composites was effectively improved on account of the uniform dispersion of HPA‐GO and interfacial chemical interaction between HPA‐GO and epoxy. Compared with neat epoxy resin, the inclusion of 0.10 wt% HPA‐GO led to 310.5 and 37.2% increase in impact strength and tensile strength, respectively. © 2019 Society of Chemical Industry     

超支化聚酰胺酯增韧增强环氧树脂的性能研究

以四氢甲基苯酐(MeTHPA)为固化剂,超支化聚酰胺酯(HBP)为增韧剂,制备了HBP/MeTHPA/环氧树脂(EP)固化体系。采用红外光谱(FT-IR)对HBP/MeTHPA/EP复合体系的固化机理进行了研究,并讨论了不同含量的HBP对固化体系热力学性能的影响。实验结果表明,HBP的加入会促进体系的固化反应;当w(HBP)=10%时力学性能最佳,冲击强度和拉伸强度分别增加了142.71%和34.44%,而玻璃化转变温度(Tg)有所下降,储能模量在玻璃态时均明显提高。