Epoxy resins modified by carbon dioxide

Epoxy resins are widely used as high‐performance thermosetting resins for many industrial applications, but unfortunately, some are characterized by a relatively low toughness. In this respect, many efforts have been made to improve the toughness of cured epoxy resins by the introduction of rigid particles, reactive rubbers, interpenetrating polymer networks, and thermoplastics within the matrix. In this work, kaolin as a modifier was added at different contents to improve the toughness of diglycidyl ether of bisphenol A epoxy resin with polyamino‐imidazoline as a curing agent. The chemical reactions suspected of taking place during the modification of the epoxy resin were monitored and evaluated with Fourier transform infrared spectroscopy. The glass‐transition temperature (Tg) was measured with differential scanning calorimetry. The mechanical behavior of the modified epoxy resin was evaluated in terms of the Izod impact strength (IS), the critical stress intensity factor (KIC), and tensile properties at different modifier contents. Scanning electron microscopy (SEM) was used to elucidate the mechanisms of deformation and toughening in addition to other morphological features. Finally, the adhesive properties of the modified epoxy resin were measured in terms of tensile shear strength (TSS). With the addition of kaolin, the reactivity test revealed that the gel time and temperature, exotherm peak, and cure time were reduced. Infrared spectra showed the existence of a chemical reaction between kaolin and the epoxy resin. The presence of kaolin caused a steady decrease in Tg by about 10°C until 15‐phr kaolin was reached prior to leveling off. Most of the tensile properties attained a peak at an approximately 10‐phr kaolin content where the toughening reached its maximum. The modulus increased linearly from 1.85 to 2.7 GPa with increasing kaolin content. For both notched and unnotched specimens, a twofold increase in Izod IS was obtained by the addition of just 10‐phr kaolin compared to the unfilled resin. On the addition of kaolin, the Izod IS varied from 0.85 to 1.53 kJ/m2 for notched specimens and from 4.19 to 8.32 kJ/m2 for unnotched specimens, whereas KIC varied from 0.91 to 2.63 MPa m1/2 with increasing kaolin content. The adhesive properties, evaluated in terms of TSS, increased from 9.14 to 15.02 MPa. SEM analysis revealed that the prevailing toughening mechanism for the epoxy resin under consideration was localized plastic shear yielding induced by the presence of kaolin particles associated with crack pinning. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 861–878, 2001

Modification of epoxy resin using reactive liquid (ATBN) rubber

Effect of cross-link density on modification of epoxy resins with reactive acrylic elastomers

The article briefly reviews literature on the modification of epoxy resins and their properties, which are used for its industrial applications. Experimental results on modified epoxy resins are collectively summarized, which focus on the structure, curing, and alternate methods for modification of epoxy resins. The several properties such as thermal stability, adhesive, toughness, and electrical conductivity have been studied during the modifications of epoxy resins, which is useful in the field of electronic encapsulation, blending, composites, and nanocomposites, etc. The review concludes with a brief discussion on the most useful valuable modifications for industrial applications.

Targeting high‐effective modification of flame retardant epoxy resin, elements including phosphorus, nitrogen, and fluorine are simultaneously incorporated into a polymer named as PFNP. A certain amount of amino groups are preserved on PFNP chains to participate in the curing of epoxy resin. The reactive groups and segments contain 9,10‐dihydro‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) endowed PFNP with good compatibility in epoxy resin. The proper addition of PFNP improves the mechanical property and Tg values of epoxy resins. The limiting oxygen index values of EP/PFNP increases while the peak heat release rate, heat release capacity, and total heat release values reduce after introduction of PFNP. Samples with contents of PFNP higher than 5 wt% reach UL‐94 V‐0 rating without dripping. Notably, the migration effect of trifluoromethyl (CF3) groups not only increases the water contact angles, but also reduces the dielectric constants of epoxy resins.

To investigate the potential of modified epoxy resin for repairing and strengthening historical wooden structures, this study utilized polyurethane and silicone-modified epoxy resin as the base, alongside a polyamine curing agent. The resin mixture was cured at ambient temperature, resulting in the creation of ten unique epoxy resin systems. Investigation into the chemical structure and alterations to the glass transition temperature were conducted. The study conducted tests and characterization of viscosity, curing rate, mechanical properties, stress failure mode, hygrothermal aging resistance, and bonding properties. The results reveal that the curing degree of the two modified epoxy resins is high after being cured at room temperature, and the chemical structure and curing rate show insignificant changes. The range of the glass transition temperature for the modified epoxy resin is between 61.31 °C and 70.51 °C. The incorporation of polyurethane and silicone molecular chains into the epoxy resin cross-linking curing system enhances the toughness of the epoxy resin. The modified resin achieves a maximum elongation at break that is 5.18 times greater than that of the unmodified resin, along with a maximum tensile strength and a compressive strength that are 7.94 and 1.74 times, respectively, higher than those in the Chinese technical specifications for the maintenance and reinforcement of ancient wooden structures. The increase in toughness changes the failure mode of the cured epoxy resin. The modified epoxy resin exhibits great bonding ability to aged wood, with a shear strength of up to 9.6 MPa along the grain. As a result, the modified epoxy resin meets the requirements for the reinforcement and repair of the timber members of ancient buildings.

PurposeTo reduce the cost of epoxy adhesive without affecting the properties of epoxy adhesive in two pack system.Design/methodology/approachFor effective toughening, adhesion, chemical resistance, etc. various compositions were made by incorporating flow modified solid epoxy resin. The impact, adhesive strengths and some other properties of the unmodified and modified epoxy networks were characterised.FindingsThe modification of epoxy resin using flow modified solid epoxy resin showed significant enhancement of impact and adhesive strengths and chemical resistance over the unmodified one. The optimum results were obtained at 13.66 parts per hundred parts of epoxy resin (phr) of modifier by replacing 4.33 phr of aerosil.Research limitations/implicationsThe modifier, 7004 FM, used in the present context was high molecular weight flow modified epoxy resin. Besides, these results could be obtained from other grades of flow modified high molecular weight epoxy resin. In addition, the efficiency of modification of epoxy resin using this could also be studied.Practical implicationsThe method developed provided a simple and practical solution to removing the costly aerosil without affecting properties such as toughness, adhesive strength and chemical resistance of the cured epoxy.Originality/valueThe method for enhancing toughness, adhesive strength and chemical resistance of cured epoxy was novel and could find numerous applications in surface coating and adhesive.

Investigation on fundamental properties and chemical characterization of water-soluble epoxy resin modified cement grout

Development of a method of degradation of poly(ethylene terephthalate) (PET) wastes for the preparation of materials for the synthesis and modification of epoxy resins, development of a method of preparation of epoxy resins, characterization of epoxy resins so prepared, and optimization of the composition of epoxy resins modified with recycled materials were the goals of this work. Therefore, the conditions required for the strong degradation of waste PET by glycolysis reaction were chosen. Glycols with different length of alkyl chain were tested. Composition and structure of the degradation products were determined by GPC and spectroscopic methods (i.e. FT‐IR, 1H‐NMR, and 13C‐NMR). Next, the products of waste PET glycolysis were used as polyhydroxylic reagents for the synthesis of epoxy resins by their reaction with epichlorohydrin. Bis(2‐hydroxyalkyl)‐terephthalate was used as a model compound. The products were applied in the preparation of compositions with Bisphenol A‐based low‐molecular‐weight epoxy resins. It was found that modification of epoxy resins with the products of PET degradation led to the improvement of their tensile and flexural strengths, hardness, and thermal stability. Better results were obtained for the products with longer alkyl fragments. The incorporation of alkylether chains from PET glycolysis not only increased water absorption of the modified resins, but also improved their chemical stability against 10% HNO3, 75% H2SO4, and ethyl acetate. Copyright © 2008 John Wiley & Sons, Ltd.

Modification of epoxy resin: a comparison of different types of elastomer

ABSTRACTThis research is dedicated to improving the mechanical properties and thermal stability of epoxy resin modified with polyimide. Two types of imides, along with soluble polyimides incorporating trifluoromethyl and tert‐butyl groups, were synthesized as modifiers for epoxy resins. We investigated the effects of imide units with varying structures and soluble polyimides on the mechanical, thermal, and dielectric properties of epoxy resins. The six‐membered imide ring demonstrated enhanced thermal stability compared to its five‐membered counterpart. The modified epoxy resins exhibited a substantial improvement in mechanical properties, with elongation at break increasing from 6.5% to 11.33%, compared to unmodified ones. SEM images of the fracture surfaces of the modified epoxy resins showed distinct fracture features, which indicated enhanced toughness as a result of the incorporation of imide units. These modified resins also demonstrated excellent thermal stability (with a char yield of 31.5% at 800°C), low hydrophilicity (water absorption ranging from 0.69% to 1.54%, and contact angles between 72° and 85°), and superior dielectric properties (the dielectric constant decreased by 1.95 at 103 Hz, while the volume resistivity increased by two orders of magnitude). This research provides new insights into the application of epoxy resins in the aerospace and advanced electronic materials fields.

PurposeTo evaluate the efficiency of modifying epoxy resin using amine terminated poly(ethylene glycol) benzoate (ATPEGB) for improved toughness and to optimise the results of such a modification.Design/methodology/approachFor effective toughening, various compositions were made by incorporating different concentrations of ATPEGB. The impact and adhesive strengths of the unmodified and modified epoxy networks were characterised.FindingsThe modification of epoxy resin using ATPEGB showed significant enhancement of impact and adhesive strengths over the unmodified one. The modification caused a chemical linkage between ATPEGB and resin which led not only to a phase separation but also to ensuring the intrinsically strong chemical bonds across the ATPEGB phase/resin matrix interface, which was the main cause to the improved impact and adhesive strengths. The optimum results were obtained at 12.5 phr (parts per hundred parts of epoxy resin) of modifier.Research limitations/implicationsThe modifier, ATPEGB, used in the present context was synthesised from poly(ethylene glycol) (PEG) of molecular weight 600. Besides, it could be synthesised from PEG of molecular weight 200, 400, 4,000, 20,000 etc. In addition, the efficiency of modification of epoxy resin using these could also be studied.Practical implicationsThe method developed provided a simple and practical solution to improving the toughness of cured epoxy.Originality/valueThe method for enhanced toughness of cured epoxy was novel and could find numerous applications in surface coating and adhesive.

Epoxy resins are a very versatile class of compounds. They have excellent mechanical properties and are easily processable; however, their major drawback is their brittleness. An attempt was made to improve the impact strength of the epoxy without decreasing its other properties. In the present study a commonly used epoxy resin, diglycidyl ether of Bisphenol‐A, was modified by the addition of bismaleimide (BMI) and diallyl phthalate (DAP) and was cured with diaminodiphenylmethane and benzoyl peroxide. The composition incorporating 5 phr BMI showed maximum heat deflection temperature (HDT) and flexural strength with impact properties remaining almost unaffected. Further addition of BMI reduced the HDT and flexural properties but increased the impact strength. For epoxy‐DAP systems the maximum HDT and flexural strength were observed on addition of 5 phr DAP. Further addition of DAP lead to a decrease in all properties except impact strength, which was observed to increase. Incorporation of both BMI and DAP, simultaneously, into the epoxy resin resulted in improvement in mechanical properties for most of the compositions. However, the HDT was found to be less than that for unmodified epoxy. POLYM. ENG. SCI., 47:1881–1888, 2007. © 2007 Society of Plastics Engineers

Hydroxy‐terminated polybutadiene was functionalized with isocyanate groups and employed in preparation of a block copolymer of polybutadiene and bisphenol A diglycidyl ether (DGEBA)‐based epoxy resin. The block copolymer was characterized by Fourier transform infrared (FTIR) spectroscopy and size‐exclusion chromatography (SEC). Cured blends of epoxy resin and hydroxy‐terminated polybutadiene (HTPB) or a corresponding block copolymer were characterized by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMTA), and scanning electron microscopy (SEM). All modified epoxy resin networks presented improved impact resistance with the addition of the rubber component at a proportion up to 10 wt % when compared to the neat cured resin. The modification with HTPB resulted in milky cured materials with phase‐separated morphology. Epoxy resin blends with the block copolymer resulted in cured transparent and flexible materials with outstanding impact resistance and lower glass transition temperatures. No phase separation was discernible in blends with the block copolymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 838–849, 2002

L‐leucine was converted to S‐2‐chloro, 4‐methyl pentanoic acid (CMPA) with retention of optical activity. CMPA was reacted with the epoxy resin to form chiral monoester and chiral diester compounds. The modified epoxy resin (MER) was characterized by FTIR spectrophotometer and polarimeter and was analyzed for epoxy content. The MER shows optical activity and the optical rotation increases with increasing concentration of CMPA. DSC studies indicate similar reactivity of the enantiomers of CMPA as well as the recemic mixture. The MER containing different concentrations of chiral modifier was cured with a stoichiometric amount of amine hardener. The cured film (obtained up to 21 mol % of CMPA) exhibits chiral property as well. Dynamic mechanical thermal analysis (DMTA) studies indicate high damping behavior. A shift in tan δ peak toward lower temperature was observed with increasing concentration of chiral modifier. The tan δmax increases up to 14 mol % of CMPA in MER and decreases thereafter. However, storage modulus gradually decreases with an increase in CMPA. Cured film based on two enantiomer‐modified epoxy samples shows different damping behavior. CMPA was also blended with poly(methyl methacrylate) and the blend films were studied similarly. The system behaves in a similar fashion as observed with cured MER films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2523–2529, 2002