Лако-красочные материалы — производство

Conventional plasticizers may be used in formulated products. Phthlate esters are the preferred plasticizers. They exhibit little tendency to migrate and have good compatibility with both resins and hardeners. Addition rates are typically 5 to 20%. Chlorinated plas­ticizers may be used to reduce flammability, especially in conjunction with antimony trioxide. The effect of plasticizer additions […]

In addition to the monofunctional epoxies described under resins, products with active hydrogens, such as furfuryl alcohol, coal tars, or phenols, will react with the epoxy resins Table 2 Epoxy Curing Agents Usage Uncatalyzed HDT Curing agent (phr)a cure (°C) (°C) Applications Aliphatic primary amines Diethylene triamine 10-12 Ambient 80-100 Short pot life Tetraethylene pentamine […]

Use of mixed hardener systems is common. Hardeners may be blended to achieve proper­ties intermediate to the individual components, to reduce exotherm or accelerate cure, to modify the cured properties, or simply to arrive at a more convenient mix ratio. Several classes of curing agents each having distinctive characteristics may be used. 1. Aliphatic primary […]

Although DGEBA resins provide the backbone of most epoxy formulations, they may be blended with other types to achieve modifications. Epoxy novolacs, having higher func­tionality, increase the cross-linking density, which improves heat resistance but decreases impact resistance. Incorporation of epoxidized oils increases flexibility at the expense of heat and chemical resistance. Low-viscosity polyfunctional epoxies based […]

Epoxy resins offer a unique combination of properties for adhesive applications. These include the ability to formulate liquid systems without solvents or carriers, the ability to convert these systems to cured products without the production of low-molecular-weight by-products, the ability to bond dissimilar or nonporous surfaces, and the ability to produce thick sections without subsequent […]

During cure of epoxies, especially systems with a short pot life or large mixes, considerable heat is evolved. This accelerates the cure, leading to even greater heat evolution. Mixes larger than 5 kg can reach excessive temperatures even with systems that have relatively long pot lives in quantities of 100 g. In addition to shortening […]

Stoichiometric ratios can be calculated similarly for hardeners. In principle, each active hydrogen will react with one epoxy group. Thus a low-molecular-weight aliphatic poly­amine such as diethylene triamine (DETA) has a molecular weight of 103 and five active hydrogens. The hydrogen equivalent is thus 20.6. The stoichiometrically correct ratio with an epoxy resin of EEW […]

Epoxy resins react with hardeners in stoichiometric quantities. Thus a knowledge of the number of reactive sites is needed in order to calculate correct ratios. For the resin this is given by the epoxide equivalent weight (EEW), which is the quantity of resin required to yield one epoxy group. For a DGEBA type in which […]

Epichlorhydrin is capable of reacting with hydroxyl groups, with the elimination of hydro­chloric acid. The most widely used epoxy resins are the family of products produced by the reaction between epichlorhydrin and bisphenol A. This reacts with additional epichlorhydrin to produce a molecule of general structure Commercially useful grades are relatively low-molecular-weight products in which […]

T. M. Goulding Consultant, Johannesburg, South Africa I. INTRODUCTION Epoxy or epoxide resins are a group of reactive compounds that are characterized by the presence of the oxirane group They are capable of reacting with suitable hardeners to form cross-linked matrices of great strength and with excellent adhesion to a wide range of substrates. This […]