Showing papers on "Epoxy published in 1980"

Thermal expansion and swelling of cured epoxy resin used in graphite/epoxy composite materials

Abstract: The paper presents results of experiments in which the thermal expansion and swelling behavior of an epoxy resin system and two graphite/epoxy composite systems exposed to water were measured. It was found that the cured epoxy resin swells by an amount slightly less than the volume of the absorbed water and that the swelling efficiency of the water varies with the moisture content of the polymer. Additionally, the thermal expansion of cured epoxy resin that is saturated with water is observed to be more than twice that of dry resin. Results also indicate that cured resin that is saturated with 7.1% water at 95 C will rapidly increase in moisture content to 8.5% when placed in 1 C water. The mechanism for this phenomenon, termed reverse thermal effect, is described in terms of a slightly modified free-volume theory in conjunction with the theory of polar molecule interaction. Nearly identical behavior was observed in two graphite/epoxy composite systems, thus establishing that this behavior may be common to all cured epoxy resins.

A model for the toughness of epoxy-rubber particulate composites

Abstract: Epoxy resins are toughened significantly by a dispersion of rubber precipitates. Microscopic examinations of propagating cracks in epoxy-rubber composites reveal that the brittle epoxy matrix cracks, leaving ligaments of rubber attached to the two crack surfaces. The rubber particles are stretched as the crack opens and fail by tearing at large, critical extensions. This fracture mechanism is the basis of a new analytical model for toughening. An increase in toughness (ΔGIC) of the composite is identified with the amount of elastic energy stored in the rubber during stretching which is dissipated irreversibly (e.g. as heat) when the particles fail. The model predicts the failure strain of the particles in terms of their size. It also relates the toughness increase to the volume fraction and tearing energy of the rubber particles. Direct measurements of the tearing strains of rubber particles, and toughness data obtained from epoxy-rubber composites, are in good agreement with the model. The particle-stretching model provides a quantitative explanation, in contribution to existing qualitative theories, for the toughening of epoxy-rubber composites.

Photosensitive resin composition

Abstract: PURPOSE:To prepare a photosensitive resin composition having excellent flexibility, adhesivity, air drying characteristics, curability, and storage stability, and useful as a raw material of paint, letter press, etc., by compounding a specific reaction product, an unsaturated epoxyester, a polymerizable monomer, and a photosensitizer. CONSTITUTION:A composition composed of (A) a reaction product obtained by (1) reacting (i) an epoxy compound having two or more epoxy groups in a molecule with (ii) 0.1-0.95 equivalent, based on the epoxy group, of (meth)acrylic acid, (2) reacting the above product with (iii) an amino compound having two or more active hydrogen atoms in a molecule to obtain the product wherein the equivalent ratio of the active hydrogen atom to the residual epoxy group is 0.5-1.1, and (3) reacting the product with (iv) a polyisocyanate compound to obtain the product wherein the equivalent ratio of the isocyanate group to the unreacted hydroxyl group is 0.05-0.7, (B) an unsaturated epoxyester, (C) a polymerizable monomer such as hydroxyalkyl acrylate, and (D) a photo-sensitizer. The amounts of the components (A)-(D) are adjusted to satisfy the formulas I-III (weight ratio).

Epoxy‐water interactions

Abstract: It has been shown that sorbed moisture plasticizes epoxy resins with a resultant depression in the glass transition temperature of the polymer. The nature of the epoxy-water interaction still requires further investigation. The equilibrium sorption and diffusion of water in a high Tg epoxy is examined. Other analytical techniques including differential scanning calorimetry, infrared spectroscopy, electron microscopy and nuclear magnetic resonance are applied to the system. Experimental results suggest that the sorbed water at low concentrations is strongly localized at specific segments or groups in the polymer. Discussion is given relative to the structure-properties of the epoxy and its possible correlation to the experimental data obtained.

The mechanical properties of epoxy resins

Abstract: Crack propagation in a series of epoxy resins described in Part 1 has been studied as a function of testing rate and temperature. It has been found that crack propagation is continuous at low temperatures but that as the temperature is raised the mode of propagation becomes unstable (stick/slip). Features on the fracture surfaces at the crack arrest lines have been shown to be of the same dimensions as those expected for a Dugdale plastic zone. It has been suggested that the “slip” process takes place by slow growth of a crack through the plastic zone followed by rapid propagation through virgin material. It has been shown that the stick/slip behaviour is due to blunting of the crack which is controlled by the yield behaviour of the resin. A unique fracture criterion has been shown to be applicable to epoxy resins which is that a critical stress of the order of three times the yield stress must be achieved at a critical distance ahead of the crack. Electron microscope replicas of the fracture surfaces have been obtained and an underlying nodular structure can be resolved. However, no direct correlation between the nodule size and fracture properties has been found.

Compression strength of carbon, glass and Kevlar-49 fibre reinforced polyester resins

Abstract: The compression behaviour of a series of polyester resins of various compositions and in different states of cure has been investigated. Their mechanical characteristics having been established, the same range of resins was then used as a matrix material for a series of composites reinforced with carbon, glass and aromatic polyamide fibres. The composites were unidirectionally reinforced, having been manufactured by pultrusion, and were compression tested in the fibre direction after a series of experiments to assess the validity of a simple testing procedure. “Rule of Mixtures” behaviour occurred in glass-polyester composites up to limiting volume fractions (V f) of 0.31 for strength and 0.46 for elastic modulus, the compression modulus being equal to the tensile modulus, and the apparent fibre strength being in the range 1.3 to 1.6 GPa at this limiting V f. At a V f of 0.31 the strengths of reinforced polyesters were proportional to the matrix yield strength, σ my, and their moduli were an inverse exponential function of σ my. For the same matrix yield strength a composite with an epoxy resin matrix was stronger than polyester based composites. At V f=0.30, Kevlar fibre composites behaved as though their compression modulus and strength were much smaller than their tensile modulus and strength, while carbon fibre composites were only slightly less stiff and weaker in compression than in tension. The compression strengths of the polyester resins were found to be proportional to their elastic moduli.

Ultraviolet curable silicone adhesives

Abstract: An ultraviolet light curable silicone pressure sensitive adhesive is provided which is comprised of an epoxy functional silicone polymer and a combination of standard MQ silicone resins or epoxy functional MQ silicone resins, which can be cured to an adhesive composition in the presence of certain bis(aryl)halonium salt catalysts.

Thermoplastic resinous composition

Abstract: Disclosed is a soft and flexible thermoplastic resinous composition having high impact and tear resistances, a good processability and a good thermal adhesion to a wide variety of plastic and other materials. The resinous composition consists essentially of 5 to 70 wt. % of a thermoplastic polyurethane elastomer and 30 to 95 wt. % of a modified polyolefin or an olefin copolymer, having functional groups of at least one type selected from carboxyl, carboxylate salt, carboxylic anhydride, amide, hydroxyl and epoxy groups. A typical application of the thermoplastic resious composition is a laminate having at least two laminae bonded to each other, at least one of the laminae being comprised of the above-mentioned resinous composition and the other being comprised of at least one material selected from vinyl chloride polymer resins, vinylidene chloride polymer resins, thermoplastic polyester resins, ethylene/vinyl alcohol copolymer resins, polyamide resins, polyacrylonitrile and nitrile copolymer resins, polystyrene and styrene copolymer resins, polymethyl methacrylate and acrylic copolymer resins, polyurethane resins, olefin polymer resins, polyacetal resins, polyvinyl acetal resins, polycarbonate resins, polyphenylene oxide resins, polysulfone resins, epoxy resins, phenol-formaldehyde resins, unsaturated polyester resins, melamine-formaldehyde resins, urea-formaldehyde resins, natural and synthetic rubbers, cellulosic materials, cement, glass and other ceramic materials and metals.

Process for consolidating water-wet sands with an epoxy resin-forming solution

Abstract: In a well treating process for consolidating a mass of particles with an epoxy resin precipitated from a resin-forming solution, a significant improvement is provided by using: a polyamino curing agent, a particular ratio of curing agent to epoxide, and a pretreatment which wets the particles with an aqueous liquid that contains an effective proportion of a dimethylaminomethyl-substituted phenol.

Effects of fiber length on the tensile strength of epoxy/glass fiber and polyester/glass fiber composites

Abstract: In discontinuous fiber-reinforced composites, the shear strength at the fiber–matrix interface plays an important role in determining the reinforcing effect In this paper, a method was devised to accurately determine this shear strength, taking the strength distribution of glass fiber into consideration Calculated strength values based on the shear strenght obtained by the method were in better agreement with the experimental observations than those calculated by employing the shear strength obtained on the assumption that the fiber strength was uniform The tensile strength of composites increases with increasing aspect ratio of the reinforcing fibers This trend is almost the same regardless of the kind of matrix, the nature of interfacial treatment, and the environmental temperature When composites are reinforced with random-planar orientation of short glass fibers of 15 times the mean critical fiber length, the tensile strength of composite reaches about 90% of the theoretical strength of composites reinforced with continuous glass fiber Reinforcing with glass fibers 5 times the critical length, the tensile strength reaches about 97% of theoretical However, from a practical point of view, it is adequate to reinforce with short fibers of 15–20 times the mean critical fiber lenght

Woven material and layered assembly thereof

Abstract: Complex woven material as reinforcement for forming layered resin impregnated articles which are resistant to catastrophic damage from shock or local impact as from a hard object, comprised of woven bands or strips of high modulus fibers such as carbon or graphite fibers, separated in at least one direction of the material, from each other by woven bands or strips of low modulus fibers such as glass fibers, and which in a preferred embodiment are narrower than the strips of high modulus fibers. Superimposed layers of such materials can be formed, wherein the strips of high modulus fibers and low modulus fibers in the respective layers are at different angles. Such woven materials, e.g. in the form of a layered assembly, are impregnated with a suitable thermosetting resin such as an epoxy resin, and cured, to produce a layered resin impregnated article having improved damage tolerant physical and mechanical properties.

Stabilization composition for coating composition

Abstract: The invention comprises a method for the color stabilization of iodoalkyne carbamates by the addition thereto of selected epoxy compounds. The epoxy compounds which thus function as stabilizers may be employed as a part of solutions containing the iodoalkyl carbamates, or they may be employed as a part of the films, coatings or compositions containing the iodoalkyne compounding.

Durable antisoiling coatings for textile filaments

Abstract: A durable antisoiling coating composition for textile filaments and articles made therefrom comprises a perfluoroalkyl ester of a citric acid urethane and fluorinated alcohols in combination with a modified epoxy resin which is the reaction product of a carboxyl-functional vinyl polymer, an epoxy resin and a tertiary amine. The composition can be applied as an aqueous dispersion, including a non-ionic textile lubricant based on poly(ethylene glycol). The dispersion can be used as a spin finish to provide durable protection to filaments, particularly nylon filaments.

The Structure and Moisture Stability of the Matrix Phase in Glass-Reinforced Epoxy Composites

Abstract: The utilization of reinforced plastic composites is generally limited by their sensitivity to long-term environmental exposure. Glass-reinforced thermosetting polymers in particular are detrimentally affected, reversibly and/or irreversibly, by exposure to water vapor or liquid water. A reinforced composite consists of three mutually interacting regions: fiber, matrix, and the fiber/ matrix interface. Each region may, for purposes of convenience, be further subdivided according to its location or properties. Most common is the listing of regions comprising the “interface”: glass/ coupling agent interface, the coupling agent polymer itself, and the coupling agent/matrix interface. Even the amorphous cross-linked matrix nearby the filler is believed to possess properties dissimilar to those of the bulk. Each region and subregion is altered by moisture exposure to some extent; at this time studies on composite stability still focus on determining which regions are most affected by the environment an...

Roofing composition and structure

Abstract: A pourable roofing composition composed of chopped discrete small chunks or pieces of closed cell plastics material, such as polystyrene, polyurethane, and the like; inexpensive granular or powder particles of fly ash or the like inert particulate material which will hold down the light cellular plastic pieces; and an emulsion caulking or sealing type binder or adhesive capable of setting under atmospheric conditions to seal the composition into an all weather resisting waterproof layer. Suitable binders or adhesives are liquid based emulsions of acetates, acrylic resins, epoxy adhesives, and the like. The composition is flowable, can be premixed remote from the building or use site, can be transported to the site in a concrete mixer type truck, and can thereafter be spread over a roof base and screed to the desired contour and level. After an initial set, an overcoat of a sealer such as an acrylic resin-type sealer can be applied.

Water-borne coating composition made from modified epoxy resin, polymeric acid and tertiary amine

Abstract: Water-borne reaction products of (a) carboxylfunctional polymers; (b) modified polyepoxides; and (c) tertiary amines are useful as film-forming components of coating compositions which can be spray-, flow-, dip-, roller-, or electro-coated. The coating compositions are useful as such or can be crosslinked with crosslinking agents such as a nitrogen resin and, when coated on metal and paper substrates, they provide coatings of improved properties, including a high degree of flexibility during machining and stamping of the coated articles, corrosion resistance, gloss, hydrolytic stability, and nonadulterating of foods and beverages in contact therewith.

Coating composition capable of forming a multilayer film

Abstract: A coating composition capable of forming a multilayer coated film, said composition comprising (a) a solid powder comprising an olefinic resin containing at least 76% by weight of a structural unit derived from an olefin and having a melt index of from 0.3 to 120 g/10 min., (b) a film-forming resin material containing an epoxy resin having a number average molecular weight of about 300 to about 4,000 and an epoxy equivalent of from 100 to 3,300, and (c) a volatile organic liquid medium capable of wetting said powder (a) but substantially incapable of swelling and dissolving said solid powder (a).

Co-curing agents for epoxy resins

Abstract: A N-substituted piperazine or N-substituted homopiperazine adduct with a polyepoxide is used as a co-curing agent in epoxy resin systems containing a polyepoxide and a known curing agent such as dicyandiamide, a carboxylic acid anhydride, or a dihydrazide. The preferred adducts have a ratio of epoxy groups to secondary amino groups of between 1.2:1 and 3:1. The preferred polyepoxides are polyglycidyl ethers of 4,4'-isopropylidenediphenol (bisphenol A). Suitable adducts are prepared from N-methyl-, N-(2-hydroxyethyl)-, N-octyl-, N-phenyl- and N-benzyl piperazine and N-methyl homopiperazine.

Micromechanisms of crack extension in composites

Abstract: Typical engineering composites consist of brittle fibres, such as glass or carbon, in a weak, brittle, plastic matrix such as epoxy or polyester resin. An important characteristic of these composites, however, is that they are surprisingly tough, largely as a result of their heterogeneous nature and the manner of their construction. During deformation, microstructural damage is widespread throughout the composite, but much damage can be sustained before load-bearing ability is impaired. Beyond some critical level of damage, failure may occur by the propagation of a crack which usually has a much more complex character than cracks in homogeneous materials. Crack growth is inhibited by the presence of interfaces both at the microstructural level between fibres and matrix and at the macroscopic level as planes of weakness between separate laminations in a multiple laminate. The fracturing of a composite therefore involves not only the breaking of the load-bearing fibres and the weak matrix, but a co...

Phosphonium phenoxide catalysts for promoting reaction of epoxides with phenols and/or carboxylic acids

Abstract: Certain tetrahydrocarbyl phosphonium phenoxide salts are described herein which are novel compounds and/or novel catalysts for promoting the reaction between vicinal epoxides and phenols and/or carboxylic acids or anhydrides. These catalysts are particularly useful in preparing high molecular weight epoxy resins by the advancement reaction of diglycidyl ether of bisphenol A with bisphenol A.

Sizing composition and sized glass fibers and process

Abstract: A sizing composition for use in a process of producing sized glass fiber strands that can be used in reinforcing polymers is provided. Also provided are the sized glass fiber strands, glass fiber reinforced polymers and processes for producing these materials. The sizing composition comprises one or more organo silane coupling agents, a major amount of the solids of the aqueous sizing composition is an epoxidized polar thermoplastic copolymer where there are three to about twelve parts of epoxy per 100 parts of the other comonomer and one or more nonionic, cationic or anionic lubricants. The sizing composition can also have one or more compatibilizing agents such as a polyvinyl-acetate-ethylene copolymer unsaturated polyester resins, polyvinylacetate homopolymer, epoxy polymers and epoxy polyester copolymers. The comonomers for the epoxidized polar thermoplastic copolymer are vinyl acetate, acrylates, polyurethane condensate monomer, polyester condensate monomer, and polyamide condensate monomer. The epoxidized polar thermoplastic copolymer has a Tg in the range of ambient temperatures to about 70° C. The glass fiber strands treated with this sizing composition can be made into roving for use in producing glass fiber reinforced polymers like polyester polymers, vinyl ester polymers and epoxy polymers.