Synthesis of tetrafunctional epoxy resins and their modification with polydimethylsiloxane for electronic application

High-performance tetrafunctional epoxy resins were synthesized by reacting a suitable tetraphenols which were obtained by the condensation of appropriate dialdehyde with phenol followed by epoxidation with a halohydrin. The structure of the synthesized tetraphenols was confirmed by infrared (IR), mass spectra (MS), and nuclear magnetic resonance (NMR) spectroscopy. Dispersed silicone rubbers were used to reduce the stress of the synthesized tetrafunctional epoxy resin cured with phenolic novolac resin for electronic encapsulation application. The dynamic viscoelastic properties and morphologies of neat rubber-modified epoxy networks were investigated. The thermal mechanical properties and moisture absorption of encapsulants formulated from the synthesized tetrafunctional epoxy resins were also studied. The results indicate that a low-stress, high glass transition temperature (T_g), and low-moisture-absorbing epoxy resin system was obtained for semiconductor encapsulation application. © 1996 John Wiley & Sons, Inc.     

Preparation of high-performance epoxy-containing silicone rubber via hydrosilylation reaction

A novel epoxy-containing silicone rubber network was constructed by hydrosilylation reaction among the synthesized vinyl-containing epoxy resin prepolymers, vinyl terminated silicone oil and hydrogen-containing silicone oil. The structure of the vinyl-containing epoxy resin prepolymers was characterized by Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance spectroscopy. Morphology observations revealed that uniform “sea-island” phase separation structure was present in modified silicone rubbers. The compatibility between silicone rubber and epoxy resin was enhanced, thanks to the good dispersion of vinyl-containing epoxy prepolymers in silicone rubber matrix. The adhesion and tensile properties of modified silicone rubbers were greatly enhanced when compared with those of unmodified counterparts. The thermal degradation behavior of cured silicone rubbers was studied using thermogravimetric analysis and thermogravimetric/infrared spectrometry analysis. Results showed that the formation of epoxy-containing silicone rubber network altered the degradation process of silicone rubber, thereby yielding a higher residue at 800 °C under nitrogen atmosphere. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48397.     

Dispersion,Mechanical and Thermal Properties of Epoxy Resin Composites Filled with the Nanometer Carbon Black

The nanometer carbon black (CB) was employed to prepare epoxy resin/carbon black (EP/CB) composites by blending-casting method. The different modified methods of silicone coupling agent were used to improve the dispersion of CB in epoxy resin. The mechanical and thermal properties of EP/CB composites were investigated. Experimental results showed that the mechanical properties increased at first, but decreased with excessive addition of CB. When the mass fraction of CB was 2%, the mechanical properties were maximum. The use of modified CB significantly enhanced the mechanical properties of the composites. For given CB loading, the CB modified by pretreatment method displayed better dispersion in the epoxy resin than that of the direct mixing method. SEM observation revealed that the tensile fracture surface of the composite filled with 2 wt% modified CB held more microcracks than that of 5 wt% modified CB, and the formed microcracks could consume more energy of rupture, finally to have better tensile strength. DSC analysis showed that the glass transition temperature (Tg) of the composites increased with the increasing mass fraction of CB.     

Studies on The Modification of Epoxy Resin with Silicone Rubber

In order to find a compatibilizer for epoxy resin/silicone rubber systems, interfacial tension of epoxy resin mixed with modified silicone oils which had the compatible groups to epoxy resin was measured against RTV silicone rubber and silicone oil. From the results, it was found that one of polyether modified silicone oils (EtMPS) had strong interfacial activity. Then using the EtMPS as the compatibilizer, RTV silicone rubber or silicone diamine was filled in epoxy resin. The effects of silicone content of these materials on impact fracture energy and on peel strength were investigated. The impact fracture energy of epoxy resin was increased by the addition of RTV silicone rubber up to two times that of unmodified resin while silicone diamine had almost no effect which might be due to the small molecular weight. T-peel strengths of aluminium plates bonded by epoxy resin filled with RTV silicone rubber and with silicone diamine effectively increased with the increasing of silicone content showing the maximum at 10 ∼ 20 phr. The fracture surfaces after the mechanical tests of these materials were observed by a scanning electron microscope. Many particles of silicone rubber in the size of 1 ∼ 20 μ were observed over the fracture surface.     

The effect of graft copolymers of maleic anhydride and epoxy resin on the mechanical properties and morphology of PP/ABS blends

In this work, maleic anhydride‐grafted polypropylene (PP‐g‐MAH) and maleic anhydride‐grafted poly(acrylonitrile‐butadiene‐styrene) (ABS‐g‐MAH) at 2 : 1 mass ratio were added as a compatibilizer in the PP/ABS blends. The compatibilizing effect was evaluated by adding the graft copolymers together with epoxy resin/imidazole curing agent (E51/2E4MZ). The reaction in reactive extrusion, morphological structure, and properties of PP and ABS blends were investigated by using infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X‐ray spectrum, transmission electron microscope (TEM), dynamic thermomechanical analysis (DMA), differential scanning calorimetry (DSC), and mechanical properties tests. The results showed that the compatibilizing effect was greatly improved because of the addition of the graft copolymers together with epoxy resin/imidazole curing agent (E51/2E4MZ) because the link structure of PP‐g‐MAH and ABS‐g‐MAH was formed by the reaction of anhydride group with epoxy group catalyzed by the imidazole. The size of the dispersed phase decreased dramatically, the interfacial adhesion between ABS particles and PP matrix was improved, and the tensile strength and flexural modulus of the PP/ABS blends increased further. The optimizing properties were obtained at 3 phr E51/2E4MZ. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40898.     

Characterization of a rigid silicone resin

Silicone resins have been used as binders for ceramic frit coatings and can withstand temperatures of 650°C to 1260°C. Conceptually, silicone resins can potentially be used as matrices for high temperature fiber‐reinforced composites. The mechanical and thermal properties of a commercially available silicone resin, Dow Corning® 6‐2230, were characterized. Neat 6‐2230 resin was found to have inferior room temperature mechanical properties such as flexural, tensile and fracture properties when compared to epoxy. The room temperature flexural properties and short beam shear strength of the silicone/glass composites were also found to be lower than those of epoxy/glass composite with similar glass content. However, the silicone resin had better elevated temperature properties. At an elevated temperature of 316°C, the retentions of flexural modulus and strength were 80% and 40% respectively of room temperature values; these were superior to those of phenolic/glass. Unlike the carbon‐based resins, the drop in flexural properties of the silicon/glass laminates with temperature leveled off with increase in temperature beyond 250°C. The resin weight loss at 316°C in 100 cm³/min of flowing air was small compared to other carbon‐based resins such as PMR‐15 and LaRC TPI. Only Avimid‐N appeared comparable to Dow Corning® 6‐2230.     

Mechanical and tribological properties of epoxy modified by liquid carboxyl terminated poly(butadiene-co-acrylonitrile) rubber

Diglycidyl ether of bisphenol A (DGEBA)-based epoxy resin was modified using liquid carboxyl-terminated poly(butadiene-co-acrylonitrile) (CTBN) rubber. The liquid CTBN contents used ranged from 2.5 to 20 parts per hundred parts of resin (phr). Mechanical properties of the modified resins were evaluated and the microstructures of the fracture surfaces were examined using SEM technique. The changes in storage modulus and the glass transition temperature were also evaluated using dynamic mechanical analysis (DMA). The tribological tests were performed using a ball-on-disc tribometer. The worn surfaces and the ball counter-mates after tribological tests were investigated using optical microscope technique. The results revealed the influence of liquid CTBN content on mechanical and tribological properties, and also microstructure of the modified epoxy resins. Impact resistance increased whereas the storage modulus and the hardness decreased when the CTBN rubber was introduced to the epoxy network. The coefficient of friction of the CTBN-modified epoxy was lower than that of the neat epoxy. The CTBN content of lower than 10 phr was recommended for improving the wear resistance of epoxy resin. Changes in tribological properties of the CTBN-modified epoxy correspond well to those in mechanical changes, especially the toughness properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Low-stress encapsulants by vinylsiloxane modification

Dispersed silicone rubbers were used to reduce the stress of cresol–formaldehyde novolac epoxy resin cured with phenolic novolac resin for electronic encapsulation application. The effects of structure, molecular weight, and contents of the vinylsiloxane oligomer on reducing the stress of the encapsulant were investigated. Morphology and dynamic mechanical behavior of rubber-modified epoxy resins were also studied. The dispersed silicone rubbers effectively reduce the stress of cured epoxy resins by reducing flexural modulus and the coefficient of thermal expansion (CTE), whereas the glass transition temperature (T_g) was hardly depressed. Electronic devices encapsulated with the dispersed silicone rubber modified epoxy molding compounds have exhibited excellent resistance to the thermal shock cycling test and have resulted in an extended device use life. © 1994 John Wiley & Sons, Inc.     

Hygrothermal cycling effects on the durability of phenolic based composites

Work has been performed to investigate the thermal and mechanical properties of carbon fiber/phenolic resin composites as engineering materials for the aerospace industry. These materials are cost effective while displaying excellent temperature and fire resistance as well as good mechanical properties. All phenolic and epoxy composite specimens used here were prepared by resin transfer molding (RTM) to model a cost‐effective process. Hygrothermal cycling effects on the property changes of phenolic composites were evaluated through thermal, mechanical, and morphological tests. The fracture performance of a phenolic composite modified with a silicone‐based additive decreased after fewer hygrothermal cycles than unmodified phenolic and epoxy composites. Results from dynamic mechanical analysis (DMA) experiments showed that the modified phenolic composite was more significantly affected by the hygrothermal cycling than the unmodified phenolic composites. Fatigue tests showed that the phenolic composites that were not exposed to hygrothermal cycling had more resistance to fatigue cycles than the epoxy composites.     

新型有机硅多元胺环氧树脂固化剂结构与性能

评价了3种有机硅多元胺APS、SFA和PSPA分别固化环氧树脂E51(DGEBA)时,固化物的力学性能和粘接强度,并与常见脂肪胺类固化剂[乙二胺、己二胺、聚醚胺(D-230)]作了对比。固化物基体力学和热性能测试表明,有机硅多元胺环氧固化物表现出较佳的冲击强度、弯曲强度和热稳定性。有机硅多元胺/环氧树脂胶粘剂的铁片粘接强度以及耐水性明显高于脂肪胺/环氧胶粘剂体系,其中含苯基有机硅多元胺作为固化剂时粘接强度最高,达到14.8 MPa。()     

Studies on The Modification of Epoxy Resin with Silicone Rubber

In order to find a compatibilizer for epoxy resin/silicone rubber systems, interfacial tension of epoxy resin mixed with modified silicone oils which had the compatible groups to epoxy resin was measured against RTV silicone rubber and silicone oil. From the results, it was found that one of polyether modified silicone oils (EtMPS) had strong interfacial activity. Then using the EtMPS as the compatibilizer, RTV silicone rubber or silicone diamine was filled in epoxy resin. The effects of silicone content of these materials on impact fracture energy and on peel strength were investigated. The impact fracture energy of epoxy resin was increased by the addition of RTV silicone rubber up to two times that of unmodified resin while silicone diamine had almost no effect which might be due to the small molecular weight. T-peel strengths of aluminium plates bonded by epoxy resin filled with RTV silicone rubber and with silicone diamine effectively increased with the increasing of silicone content showing the maximum at 10 ～ 20 phr. The fracture surfaces after the mechanical tests of these materials were observed by a scanning electron microscope. Many particles of silicone rubber in the size of 1 ～ 20 μ were observed over the fracture surface.     

环氧改性有机硅树脂的应用研究

以不同环氧改性有机硅树脂作为基料树脂,研究了不同树脂对漆膜性能的影响;通过选用不同固化体系对漆膜机械性能和耐热性做了比较;同时研究了环氧改性有机硅树脂与有机硅树脂的混溶性及影响;分别研究了该树脂配制的底、中、面涂层的常规性能及复合涂层的机械性能。同时对不同固化剂的影响和不同树脂的影响做了TG和DSC分析,结果表明,环氧改性有机硅树脂耐温性能较环氧树脂有较明显的提高,基本可用于高温涂料;环氧改性有机硅树脂可与纯有机硅树脂复配,有望形成具有更高耐温性能的涂膜。并且可通过复合固化剂的选用达到更佳的耐温性能和较好的物理机械性能。     

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.     

New thermosetting resin from poly(p‐vinylphenol) based benzoxazine and epoxy resin

Poly(p‐vinylphenol) (VP) based benzoxazine was prepared from VP, formaline, and aniline. The curing behavior of the benzoxazine with the epoxy resin and the properties of the cured resin were investigated. Consequently, the curing reaction did not proceed at low temperatures, but it proceeded rapidly at higher temperatures without a curing accelerator. The reaction induction time or cure time of the molten mixture from VP based benzoxazine and epoxy resin was found to decrease, compared with those from conventional bisphenol A based benzoxazine and epoxy resin. The curing reaction rate of VP based benzoxazine and epoxy resin increased more than that of conventional bisphenol A based benzoxazine and epoxy resin. The properties of the cured resin from neat resins and from reinforced resins with fused silica were evaluated. The cured resins from VP based benzoxazine and epoxy resin showed good heat resistance, mechanical properties, electrical insulation, and water resistance compared to the cured resin from VP and epoxy resin using imidazole as the catalyst. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 555–565, 2001     

Mechanical properties of poly(styrene‐co‐acrylonitrile)‐modified epoxy resin/glass fiber composites

Poly(styrene‐co‐acylonitrile) was used to modify diglycedyl ether of bisphenol‐A type epoxy resin cured with diamino diphenyl sulfone and the modified epoxy resin was used as the matrix for fiber‐reinforced composites (FRPs) to get improved mechanical properties. E‐glass fiber was used as fiber reinforcement. The tensile, flexural, and impact properties of the blends and composites were investigated. The blends exhibited considerable improvement in mechanical properties. The scanning electron micrographs of the fractured surfaces of the blends and tensile fractured surfaces of the composites were also analyzed. The micrographs showed the influence of morphology on the properties of blends. Results showed that the mechanical properties of glass FRPs increased gradually upon fiber loading. Predictive models were applied using various equations to compare the mechanical data obtained theoretically and experimentally. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of a marine bacterial biofilm on adhesion and retention of pseudo barnacle to silicone coating surface

The effect of a marine bacterial Cytophaga lytica (C. lytica) biofilm on the adhesion and retention of a pseudobarnacle (epoxy adhesive) to platinum-cured silicone coatings was investigated at varying coating thickness (100–800 μm), modulus (E=0.08–1.3 MPa), and shear rate (2–22 μm/s). The initial adhesion of C. lytica biofilm on the silicone coating surfaces was increased as the coating modulus was increased. Nonetheless, the adhesion strength of the pseudobarnacle was not significantly influenced by the attached biofilms, with its strength decreasing with increasing the coating modulus. Thus, these results suggest that the pseudobarnacle adhesion strength would be primarily determined by physico-mechanical properties of the silicone coatings. Also, the adhesion/detachment tests demonstrated that the retention of the pseudobarnacle after water jetting was minimal for the soft silicone coating (VP1), which showed better performance than the widely acceptable silicone resin of DC 3140.     

Epoxy-functionalized polysiloxane reinforced epoxy resin for cryogenic application

The poor cryogenic mechanical properties of epoxy resins restrict their extensive application in cryogenic engineering fields. In this study, a newly synthesized epoxy-functionalized polysiloxane (PSE) is used to improve the cryogenic mechanical properties of bisphenol-F epoxy resin. The Fourier transform infrared spectra and nuclear magnetic resonance confirm the formation of epoxy-functionalized –Si–O–Si– molecular chain. The surface free energy test results show that the PSE has a better compatibility with epoxy resin. The mechanical test results show that the cryogenic tensile strength, failure strain, fracture toughness, and impact strength of epoxy resin is improved significantly by adding the suitable amounts of PSE. Compared to the neat epoxy resin, the maximum tensile strength (196.92 MPa, an improvement of 11.2%), failure strain (2.97%, an improvement of 33.8%), fracture toughness (3.05 MPa·m^1/2, an improvement of 30.7%) and impact strength (40.55 kJ m⁻², an improvement of 14.8%) at cryogenic temperature (90 K) is obtained by incorporating 10 wt % PSE into the neat epoxy resin. Moreover, the results also indicated that the tensile strength, Young's modulus, and fracture toughness of epoxy resin with the same PSE content at 90 K are higher than that at room temperature (RT). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46930.     

Toughening epoxy resin with blocked isocyanate containing soft chain

A series of imidazole (MI) blocked 2,4‐toluene diisocyanate (TDI) with polyethylene glycol (PEG‐400) as soft segment (PEG‐MI‐b‐TDI) were synthesized for toughening and curing the bisphenol A type epoxy resin (E‐44). Fourier transform infrared (FTIR) spectrum indicates that the NCO groups of the isocyanate molecule are blocked with MI. For curing epoxy systems, elimination of epoxy group and the formation of urethane bonds were studied by FTIR spectroscopy. The results of mechanical property were shown that the tensile shear and impact strengths of neat MI and MI‐b‐TDI cured E‐44 are lower than those of PEG‐MI‐b‐TDI cured E‐44. Based on the scanning electron microscope studies, microstructure evolutions of the E‐44 cured by different curing agents were imaged. The mechanical, thermal, and dynamic mechanical properties were measured by universal testing machine, differential scanning calorimeter and dynamic mechanical analyzer (DMA). The toughness of E‐44 cured by PEG‐MI‐b‐TDI was effectively improved without sacrificing the tensile shear strength. Based on the DMA studies, the long soft chain of PEG brought in a noticeable lowering in the glass transition temperature (T_g). The glass transition temperature is near 165°C for the neat MI cured E‐44, which is higher than the T_gs of the other curing agents cured epoxy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41345.     

Application of a series of novel chain-extended ureas as latent-curing agents and toughening modifiers for epoxy resin

A series of novel chain-extended ureas (U_i) containing poly(ethylene glycol) (PEG) spacers with different molecular weights were synthesized and the reactive mechanism, reactive activity, impact strength, dynamic mechanical behavior, morphology, and storage properties of the epoxy resin/chain-extended urea system were studied. Experimental results revealed that the impact strength of the epoxy resin modified with chain-extended urea containing a PEG flexible spacer with molecular weight of 1000 is 9.5 times higher than that of the epoxy resin/dicyandiamide system. Results also show that the molecular weight of PEG in chain-extended ureas hardly has any influence on the reactive activity of the chain-extended ureas. The storage life of the epoxy resin/U_i system can be delayed to 38 h at 50°C. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 339–347, 1998     

Dynamically cured polypropylene/epoxy blends

The dynamic vulcanization process, usually used for the preparation of thermoplastic elastomers, was used to prepare polypropylene (PP)/epoxy blends. The blends had crosslinked epoxy resin particles finely dispersed in the PP matrix, and they were called dynamically cured PP/epoxy blends. Maleic anhydride grafted polypropylene (MAH‐g‐PP) was used as a compatibilizer. The effects of the reactive compatibilization and dynamic cure were studied with rheometry, capillary rheometry, and scanning electron microscopy (SEM). The crystallization behavior and mechanical properties of PP/epoxy, PP/MAH‐g‐PP/epoxy, and dynamically cured PP/epoxy blends were also investigated. The increase in the torque at equilibrium for the PP/MAH‐g‐PP/epoxy blends indicated the reaction between maleic anhydride groups of MAH‐g‐PP and the epoxy resin. The torque at equilibrium of the dynamically cured PP/epoxy blends increased with increasing epoxy resin content. Capillary rheological measurements also showed that the addition of MAH‐g‐PP or an increasing epoxy resin content increased the viscosity of PP/epoxy blends. SEM micrographs indicated that the PP/epoxy blends compatibilized with PP/MAH‐g‐PP had finer domains and more obscure boundaries than the PP/epoxy blends. A shift of the crystallization peak to a higher temperature for all the PP/epoxy blends indicated that uncured and cured epoxy resin particles in the blends could act as effective nucleating agents. The spherulites of pure PP were larger than those of PP in the PP/epoxy, PP/MAH‐g‐PP/epoxy, and dynamically cured PP/epoxy blends, as measured by polarized optical microscopy. The dynamically cured PP/epoxy blends had better mechanical properties than the PP/epoxy and PP/MAH‐g‐PP/epoxy blends. With increasing epoxy resin content, the flexural modulus of all the blends increased significantly, and the impact strength and tensile strength increased slightly, whereas the elongation at break decreased dramatically. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1437–1448, 2004