Hyperbranched Epoxy Research Articles

Effect of Hyperbranched Poly (Trimellitic Anhydride Ethylene Glycol) Epoxy (HTME) on Thermal Degradation Activation Energies of HTME/Diglycidyl Ether of Bisphenol-A Epoxy Hybrid Resin by Kissinger and Flynn–Wall–Ozawa Method

The thermal degradation behavior and kinetics of hyperbranched poly (trimellitic anhydride ethylene glycol) epoxy (HTME)/diglycidyl ether of bisphenol-A epoxy (DGEBA) hybrid resin was investigated with thermogravimetric analysis (TGA) by using Kissinger method and Flynn–Wall–Ozawa method. The results show that the thermal degradation activation energies of DGEBA, 9 wt% HTME-1/91wt% DGEBA, 3 wt% HTME-2/97 wt% DGEBA, 9 wt% HTME-2/91 wt% DGEBA, 15 wt% HTME-2/85 wt% DGEBA, and 9 wt% HTME-3/91wt% DGEBA are 152.5, 144.4, 135.4, 133.2, 121.8 and 143.0 kJmol−1, respectively, by Kissinger method. and the activation energies are 173.3, 165.0, 163.2, 151.7, 137.7 and 159.7 kJmol−1, respectively by Flynn–Wall–Ozawa method. With the increase of HTME content, the activation energies of HTME/DGEBA hybrid resin decrease. Although molecular weight or generation of hyperbranched epoxy resins (HTME) has little effect on the thermal degradation activation energies and other kinetics data.

Kinetics of curing and thermal degradation of hyperbranched epoxy (HTDE)/diglycidyl ether of bisphenol-A epoxy hybrid resin

Hyperbranched epoxy resin (HTDE) has relatively low viscosity and high molecular mass and holds great promise as a functional additive for enhancing the strength and toughness of thermosetting resins. In this work, the curing and thermal degradation kinetics of HTDE/diglycidyl ether of bisphenol-A epoxy (DGEBA) hybrid resin were studied in detail using differential scanning calorimetry (DSC) and thermogravimetric analysis (TG) techniques by Coats–Redfern model. The effect of molecular mass or generation and content of HTME on the activation energy, reaction order, and curing time were discussed; the results indicated that HTDE could accelerate the curing speed and reduce the activation energy and reaction order of the curing reaction.

Synthesis and characterization of low viscosity aromatic hyperbranched polyester epoxy resin

Low viscosity aromatic hyperbranched polyester epoxy resin (HTBE) was synthesized by the reaction between epichlorohydrin (ECH) and carboxyl-end hyperbranched polyester (HTB) which was prepared from inexpensive materials A2 (1,4-butanediol glycol, BEG) and B3 (trimellitic anhydride, TMA) by pseudo one-step method. The molar mass of the HTB was calculated from its acid value by “Recursive Probability Approach”. The degree of branching (DB) of the HTB was characterized by model compounds and1H NMR-minus spectrum technology, and the DB of the HTB was about 0.47∼0.63. The viscosity and epoxy equivalent weight of the HTBE were 3,600∼5,000 cp and lower than 540 g/mol respectively. The reaction mechanism and structure of the AB2 monomer, HTB and HTBE were investigated by MS,1H NMR and FTIR spectra technology. The molecular size of HTBE is under 8.65 nm and its shape is ellipsoid-like as determined by molecular simulation.

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.

Preparation and Characterization of Hyperbranched Polymer/Silica Hybrid Nanocoatings by Dual‐Curing Process

AbstractSummary: Organic‐inorganic nanocomposite hybrid coatings were prepared through a dual‐cure process involving cationic photopolymerization of a hyperbranched epoxy functionalized resin and subsequent condensation of an alkoxysilane inorganic precursor. All the formulations investigated gave rise to photocured films characterized by high gel content values. An increase in glass transition temperature and an increase in storage modulus above Tg in the rubbery plateau is observed with increasing TEOS content in the photocurable formulation. The important role of GPTS on reducing the inorganic domain size and avoiding macroscopic phase separation was demonstrated by TEM analyses.TEM obtained for one of the cured films in the presence of GPTS.magnified imageTEM obtained for one of the cured films in the presence of GPTS.

Study on the Performance of Diglycidyl Ether of Bisphenol-A/Hyperbranched Aromatic Polyester Epoxy Resin (HTME) System and Their Toughness Mechanism

This paper reports on the use of liquid hyperbranched aromatic polyester epoxy resin (HTME) as an additive to an epoxy resin/amine system. Four kinds of different molecular weight and epoxy equivalent weight HTME as modifiers in the diglycidyl ether of bisphenol-A (DGEBA) amine systems are discussed in detail. It was shown that the content and molecular weight of HTME have important effect on the performance of the cured system, and the performance of the HTME/DGEBA blends has maximum with the increase of content and molecular weight or generation of HTME. The impact strength and fracture toughness of the cured system with 9 wt.% second or three generation of HTME are almost 2.77 and 1.71 times, respectively, DGEBA performance; furthermore, the tensile and flexural strength can be enhanced about 17% and 20%, respectively. The glass transition temperature and Vicat temperature, however, are found to decrease to some extent. The scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), and molecular simulation technology are used to study the situ reinforcing and toughening mechanism. The three-dimensional size and structure shape of HTME-2 are displayed by molecular simulation technology.

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

AbstractThis 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 m1/2, 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

Synthesis and polymerization of a radiation curable hyperbranched resin based on epoxy functional fatty acids

A radiation curable resin has been synthesized from a hydroxy functional hyperbranched polyether onto which an epoxy functional fatty acid, vernolic acid, has been attached. The resin was cationically polymerized in presence of different amounts of vernolic acid methyl ester as a reactive diluent. The coating mixtures contained up to 30 wt.% methyl ester and all formulations polymerized readily and formed crosslinked films with T g’s between 16 and −18 °C, where the addition of the reactive diluent lowered the T g with approximately 10 °C for each 10 wt.% diluent added. The viscosities of the coating mixtures were also heavily influenced by the presence of the reactive diluent, from the pure hyperbranched epoxy functionalized polymer with a viscosity of 4100 mPa s to the formulation containing 30 wt.% methyl ester with a viscosity of 460 mPa s. The viscosities of the mixtures and the hardness of the films were also compared with a model oil based on trimethylol propane, i.e. a structurally similar resin without a polyether core. The model oil was found to have a lower viscosity than the other mixtures and produced a soft film with a low T g (−21 °C) after polymerization.

Nanocomposites based on a combination of epoxy resin, hyperbranched epoxy and a layered silicate

Epoxy/clay nanocomposites have been prepared using an diglycidyl ether of bisphenol A (DGEBA) epoxy and its blend with an epoxy functionalized hyperbranched polymer (HBP). The formation of nanocomposites was confirmed by a wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) analysis. The mechanical and dynamic mechanical properties of the nanocomposites were evaluated and compared with the corresponding matrix. The improvement in impact properties in blend and nanocomposites was explained in terms of fracture surface analysis by scanning electron microscopy (SEM).

Studies on blends of epoxy-functionalized hyperbranched polymer and epoxy resin

An epoxy-functionalized hyperbranched polymer (HBP) was used to toughen a conventional epoxy resin, diglycidyl ether of bisphenol A (DGEBA) cured with diethyltoluene-2,6-diamine (DETDA). There was little change in gel time as a result of addition of HBP, even though the HBP reacts at a slower rate with amine hardeners compared to DGEBA alone. Phase separation was investigated for various HBP contents and as a function of cure conditions as well. The thermal and dynamic viscoelastic behavior of the modified matrices have been examined and compared to the DGEBA epoxy matrix. It appears that the HBP which phase separates does not react as fully as when it is reacted with the amine alone. Nonetheless, good improvement in impact strength as a result of incorporation of HBP were observed and explained in terms of morphological behavior for a DGEBA matrix modified with various amounts of HBP.

Internal stress control in epoxy resins and their composites by material and process tailoring

AbstractThe development of internal stress during cure of epoxy and hyperbranched polymer‐modified epoxy resins was characterized, taking into account the evolving viscoelastic properties, the volumetric shrinkage due to the chemical reaction, and the thermal expansion. A criterion for void formation during cure in a constrained mold was proposed, providing guidelines for the construction of a process window for manufacturing of void‐free composites. It was shown that the internal stress development in epoxy resins during cure is strongly influenced by the presence of hyperbranched polymer modifiers. The role of these modifiers was illustrated for the case of autoclave processing of glass fiber/epoxy composites. This study showed that higher fiber volume fractions could be used with hyperbranched polymer‐modified resins than with unmodified resins, for producing void‐free laminates. It also appeared that by suitable tailoring of the process cycle, a fully stress‐free laminate could be obtained after cure, using the modified resin.

Thermomechanical properties and morphology of blends of a hydroxy-functionalized hyperbranched polymer and epoxy resin

Curing as well as the phase separation behavior of blends of a hydroxy-functionalized hyperbranched polymer (HBP) and epoxy resin have been studied by several techniques. The HBP strongly enhance the curing rate due to the catalytic effect of hydroxy groups. The phase separation has been investigated for various HBP contents and as a function of cure conditions used as well. The thermal and dynamic viscoelastic behavior of the blends have been examined and compared to the unmodified epoxy matrix. Finally, impact properties have been discussed in terms of the morphological behavior for an epoxy matrix modified with various amounts of HBP.

Hyperbranched aromatic epoxies in the design of adhesive materials

The use of hyperbranched aromatic epoxy polymer 2 (HARE) as a component in various adhesion experiments has been demonstrated. Two different modes of curing were tested, including a photoinitiated cationic curing process and a polyfunctional amine curing process. These processes gave flexible films that showed good adhesion to nylon, steel, and glass. Furthermore, blends of HARE and the commercial epoxy resin bisphenol F diglycidyl ether (BPFG) were cured with 2-ethyl-4-methylimidazole (EMI) at 150 °C on lap-shear assemblies. These cured assemblies displayed adhesive strengths in the range of 15 MPa over a broad range of HARE/BPFG weight ratios.

Hyperbranched polymers: unique design tools for multi‐property control in resins and coatings

Presents a hyperbranched polymer, a hydroxyl functional aliphatic polyester which consists of a polyalcohol core from which branches extend, forming a core‐shell structure with a large number of hydroxyl groups at its peripheral surface. It is polydisperse and consists, apart from the main core/shell fraction, of a minor fraction with tree‐like branches. Hyperbranched polyesters of this type have been found to contribute to improved physical, as well as chemical and mechanical, properties. Due to the unique molecular architecture, it is possible to design the hyper‐branched polyester in numerous ways to acquire the desired properties in different applications. Focuses on and illuminates how molecular design might affect properties in not only one, but many applications. Illustrates this by way of examples in the field of alkyds, where presented hyperbranched polymer contributes to low viscosities combined with excellent drying; in amine cured epoxies, where a hyperbranched epoxy demonstrates dramatically increased toughening; and in polyurethanes and radcure, where rapid curing can be obtained by proper molecular design.