Epoxy content

Other materials that are often referred to as secondary plasticizers iaclude materials such as epoxidized soybean oil (ESBO) and epoxidized linseed oil (ELO) and similar materials. These can act as lubricants but also as secondary stabilizers to PVC due to thein epoxy content which can remove HCl from the degrading polymer. 

Owing to relatively low viscosity, these resins offer advantages for 100% soHds (solvent-free) systems. Higher filler levels are possible because of the low viscosity. Faster bubble release is also achieved. Higher epoxy content and functionaHty of bisphenol F epoxy resins can provide improved chemical resistance compared to conventional epoxies. 

The epoxy resin component is made by a 2-stage process involving reaction of l-chloro-2,3-epoxypropane (epichlorhydrin) with isocyanuric acid to give the l,3,5-tris(2-hydroxy-3-chloropropyl) derivative, which is then treated with sodium hydroxide to eliminate hydrogen chloride to form the title compound. One batch contained more than the normal amount of hydroly sable chlorine, and when excess epichlorhydrin was distilled off, the residual material decomposed with explosive violence. It was later established that the abnormal chlorine content was associated with reduced thermal stability, and criteria for hydrolysable chlorine, epoxy content and pH have been set to prevent distillation of off-spec, material. 

See also Epoxy coatings Epoxy chalcone, 10 450 12,13-Epoxy-cis-9-octadecenoic (vernolic) acid, physical properties, 5 35t Epoxy coatings, 10 436 450 17 845. See also Epoxy can coatings for corrosion protection, 7 199 markets for, 10 442-449 performance of, 10 423 waterborne, 10 439 Epoxy composites, 10 450, 451 Epoxy compounds, photoinitiated polymerization of, 23 716 Epoxy content analysis, 10 385 Epoxy cresol novolac (ECN) resins, 10 367, 369... 

Properties often used by epoxy resin manufacturers to specify particular grades of resin include the epoxy content, viscosity or softening point, and color. In addition, properties such as density, vapor pressure, flash point, refractive index, solubility characteristics, and hydroxyl content are often reported. The important properties of uncured epoxy formulations with regard to most adhesive applications are... 

Epoxy novolac resins also differ from standard DGEBA-based epoxy resins in their multifunctionality, which is about 2.5 to 6.0. The multiplicity of epoxy groups allows these resins to achieve increased crosslink density. The commercial epoxy novolac resins (e.g., DER 438, Dow Plastics, and EPON 164, Resolution Performance Products LLC) are semisolid to solid resins with EEW in the range of 170 to 230. Recently low-viscosity epoxy novolac resins have been produced (18,000 to 28,000 cP) to provide easy processing however, these generally have lower epoxy content. 

Polysulfide resins combine with epoxy resins to provide adhesives and sealants with excellent flexibility and chemical resistance. These adhesives bond well to many different substrates. Tensile shear strength and elevated-temperature properties are low. However, resistance to peel forces and low temperatures is very good. Epoxy polysulfides have good adhesive properties down to -100°C, and they stay flexible to -65°C. The maximum service temperature is about 50 to 85°C depending on the epoxy concentration in the formulation. Temperature resistance increases with the epoxy content of the system. Resistance to solvents, oil and grease, and exterior weathering and aging is superior to that of most thermoplastic elastomers. 

Table 12.2 describes an epoxy formulation cured with DEAPA. Cure conditions of only 45 min at 100°C are adequate to obtain high bond strength on aluminum and moderately better performance at elevated temperatures than that for systems cured at room temperature. In this formulation the low-molecular-weight, high-epoxy-content resin (EPON 1009)... 

ASTM has developed a Standard Guide for Testing Epoxy Resins, which covers several procedures that can be conducted on the same starting sample (e.g., viscosity, color, and density). Other contents of the standard include test methods for nonvolatile content, acid value, epoxy content, hydrolyzable chlorine, and total chlorine. The most important of these test methods are described below. 

Next to viscosity, epoxy content and hydroxyl content are the prime properties of importance in formulating epoxy-based adhesive systems. Epoxy content allows one to determine the correct amount of curing agent to use. With certain curing agents it may also be important to know the hydroxyl content. These values determine the reactivity of the system. 

Epoxy content is generally determined by wet analytical techniques. ASTM D 1652 is widely used. The most common method is based on the addition of hydrogen halide (e.g., hydrogen chloride, hydrogen bromide, or hydrogen iodide) to the epoxy group. The difference between the amount of acid added and the amount unconsumed, determined by titration with standard base, is a measure of the epoxy content. There are numerous epoxy assay methods based on this technique. The specific method used depends on the resin type being analyzed as well as on the extent to which side reactions can occur. 

The relation between the epoxy content of various epoxy resins based on Bisphenol-A diglycidylether and AH and the glass transition temperatures of linear and cured resins is given in Table 3. 

Table 3. Relation between the epoxy content, heat of polymerization AH and Initiator concentration 2,5%(w/w)...

Epoxy content mole epoxide per kg resin Repeating unit X Heat of polymerization AH (DSC) T, (°C) resin (DSQ ... 

Epoxide oligomers before crosslinking are characterized by a number of properties, such as epoxy content, melt (or solution) viscosity, volatile content, melting (or softening) point, color, or density [1-3]. These characterizations are usually made for quality control or the specification of products. In addition, GPC and HPLC are frequently used for studying the molecular composition or purity... 

Figure 26, Effect of epoxy content on sound absorption.

Figure 28. Tensile strength of the foams v. epoxy content.

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