Neutral resins, formulation

Neutral resins formulated with various xylose contents were used to bond Douglas-fir veneers into two-ply panels at 170 °C as opposed to 140 °C used for the basic resins. This temperature was chosen for bonding since differential scanning calorimetry (DSC) showed that the unmodified and modified neutral resins produce a major exotherm at about this temperature, whereas, resol resins cured under basic conditions produce an exotherm at about 140 °C. 

Carbohydrate-Modified Phenol-Formaldehyde Resins Formulated at Neutral Conditions... 

In this study, up to about 50% of the phenol-formaldehyde was replaced with carbohydrates and the modified resins used to bond wood veneer panels. The carbohydrate modified resins were formulated and cured under neutral conditions. The resins bond wood with acceptable dry- and wet-shear strengths, and wood failures. Reducing as well as nonreducing carbohydrates can be used as modifiers. The carbohydrate modifiers are being incorporated into the resin via ether linkages between the hydroxyls of the carbohydrate and methylol groups in the phenol-formaldehyde resin. The resins formulated under neutral conditions are very light in color. 

Figure 1. Comparison of dry- and wet- (hatched) shear strengths of resins Comm = commercial resin (basic) Basic = resin formulated under basic conditions in laboratory Neut = resin formulated under neutral conditions.

Color of Bond Line. Two-ply veener panels bonded with carbohydrate-modified resins formulated under neutral conditions had bond lines that are extremely light colored in contrast to the dark red-black color characteristic of resins cured under basic conditions. The color ranges from a light yellow-tan with unmodified and xylose-modified resins to a medium tan with the prehy-drolyzate modified resins. These resins would therefore be suited for bonding wood used for decorative purposes. 

Extract ability. About 60 to 70% of the total modifier added is extractable from resins cured under basic conditions and modified with alditols and methyl glycosides (2). In contrast, only about 0 to 20% of the xylose and prehydrolysate is extractable from samples of cured resin modified with 0.6 moles of either modifier per mole of phenol. Approximately 20 to 30% of xylitol (II), methyl xyloside (III), or glucose (IV) is extractable from neutral resins modified with these carbohydrates, indicating that neutral resins incorporate the carbohydrate more effectively than resins formulated and cured under basic conditions. In addition, free reducing sugars can be used directly. 

With certain exceptions, cyanoacrylate monomer formulations containing additives e.g. rubbers, high-density neutral resins, silicon dioxide, etc., may hinder accurate and precise analysis using dilution methods. In such cases it may be necessary to prepare samples using destructive techniques, particularly where the levels are very low. Solvent selection for dilution of cyanoacrylate adhesive must be compatible for the entire journey of the sample solution from sample vessel to torch. Failure to do this could cause the cyanoacrylate to polymerise locally and block the entire sample transport system in ICP-OES and can cause serious damage requiring expensive replacements. The solvents suggested in the above dilution methods were found to be satisfactory. 

Surfactants are added to a thermoset resin system to promote the dispersion of fillers in the resin matrix. Recently, surfactants have been used to disperse carbon nanotubes in polymer matrices [48-50]. Surfactants are of two types neutral and ionic. Surfactants have many applications in coating industries for the development of a water-based resin system [51]. Surfactants are added to phenolic or polyurethane foam formulation in which they facilitate formation of small bubbles. The size and uniformity of bubble formation results in a fine cell structure. A surfactant reduces the surface tension of resin formulations and provides an interface between the highly polar resin and the non-polar blowing agent. The surfactant for a particular resin system must be selected carefully so that it is compatible with the resin and resistant... 

A B-side resin formulated for use in colour-neutral applications and designed to consistently thicken SMC without affecting shrinkage/expansion as the levels change. 

Furfuryl alcohol may also be converted into polymeric materials in the presence of acids and such products have found some commercial use. Typically, furfuryl alcohol is heated at about lOO C with an acid catalyst such as phosphoric acid. The reaction is extremely exothermic and efficient cooling is necessary to prevent premature cross-linking. When the required degree of reaction is reached the system is neutralized and dehydrated under reduced pressure. The product is a dark free-flowing liquid. Often urea and formaldehyde are also included in resin formulations. Final cure of the resin is effected in situ by addition of an acid just prior to application. Weak acids (e.g., phthalic anhydride and phosphoric acid) give mixtures with long pot life which cure at 100—200°C whilst strong acids (e.g., p-toluenesulphonic and sulphuric acids) are effective at room temperature. 

Resin Solubilizers. In general, water-soluble resins ate amine salts of acidic polymers. Water-soluble coatings formulated with AMP-95 and DMAMP-80 exhibit superior performance (15,16) (see Water-SOLUBLE polymers). AMP-95, used in conjunction with associative thickeners (17) or hydroxy-ethylceUulose, provides for the most efficient utilization of such thickeners. It also is the neutralizer of choice for use with hair spray resins. 

A filler should be dry, nonreactive with the uncured resin, and of a neutral or only slightly basic pH. Adsorbed water, which is present in some degree in most fillers, inhibits dispersion. Thus, most fillers must be dried before they are added to the adhesive formulation. The drying process will drive off adsorbed moisture and gases from the surface of the filler. The filler should generally be nonreactive with the base resins or curing agents that... 

Figure 1 illustrates the fact that resins and adhesives formed by the possible combinations of a phenolic compound, a nitrogenous compound, an aldehyde compound, and a carbohydrate have been reported in the literature. The exact conditions used to formulate the resins and adhesives represented in Figure 1 vary considerably. For example, additional circles representing acidic, basic, and neutral reaction conditions could be added. In most instances, the exact chemistry that occurs during the formulation of resins at each intersection is not known. Indeed, in many cases, the component actually reacting into the resin or adhesive system may not be the original carbohydrate added at the start. In this and other respects, these formulations will overlap with those discussed in the next section. 

The formulations should be kept as close as possible to the neutral point pH 7, and the neutralizing bases for the solvation of the resins should be as weak as possible (DMEA, NMP etc. are much more highly recommended than amines or even ammonium). 

Tablets may be formulated with coatings such as shellac, resin, or styrene-maleic acid copolymer. These coatings are insoluble in acid but dissolve readily at neutral or alkaline pH. Thus they are ideally suited to prevent drug release until the formulation has passed from the stomach into the small intestine. Preventing drug release in the stomach may protect drugs that are acid labile. It may also protect the patient from irritant substances like iron salts, diethylstilbo-estrol, and some anti-inflammatory agents. Release, and subsequent systemic availability of drugs from these formulations is likely to be highly sensitive to stomach emptying patterns.

Trimellitic Based Alkyd and Formulation. The trimellitic based alkyd was supplied as 100% non-volatile material. The acid number as received was 43.2. Calculation showed (see below) that the degree of base neutralization recommended was 85% of theory. The typical charge for resin preparation was described as (5) ... 

Hydrocarbon aerosol hair sprays contain an alcohol-hydrocarbon solvent-propellant system, a synthetic polymeric resin, a base to neutralize the resin if it is a carboxylic acid-containing resin, plasticizer(s), fragrance, and, in some cases, surfactant(s) to improve the spreading characteristics of the polymer. Most of the new low-VOC aerosol hairsprays contain alcohol-water as the solvent system and dimethyl ether as the propellant. Together the alcohol-dimethyl ether content must be below 55% (54.5%). For cost considerations, dimethyl ether is the propellant of choice, although Hydrofluorocarbon 152-A is exempt as a VOC and provides acceptable, but expensive formulations with previously used resins [54]. In Europe and other parts of the world, there are no VOC limits, and hydrocarbon-alcohol systems with virtually no water are widely used. 

Chem. Descrip. Alcohol phosphate, unneutrallzed Uses Internal mold release agent In unsat. polyester resin molding operations and FRP, e.g., metal die, compression, pultrusion corrosion protectant for ferrous metal molds release agent for externally heat-cured molding operations antistat when neutralized lubricant and corrosion inhibitor in oils formulation of textile lubricants and finishes Features Improves surf, appearance of molded parts Properties Pale yel. Ilq. mild fatty alcohol odor sol. In Freon TF, IPA, styrene, toluene, min. oil, kerosene self-dlsp. In water, glycerol Insol. in ethylene glycol sp.gr. 0.98 dens. 8.2 Ib/gal vise. 165 cps decomp. pt. > 175 C flash pt. (PMCC) > 100 C pH 2-3 anionic 100% act. 

Another common approach to water-based coating formulations is post-emulsification of a polymer in water. Several condensation polymers, e.g. alkyds, i.e. fatty-acid-modified polyesters, polyurethanes and epoxy resins, have been made into dispersions by the use of a suitable emulsifier and application of high shear. For instance, long oil alkyd resins of the type used in white-spirit-based formulations have been successfully emulsified by using nonionic surfactants such as fatty alcohol ethoxylates, alkylphenol ethoxylates or fatty acid monoethanolamide ethoxylates. Neutralization of alkyd carboxylic groups helps in producing small emulsion droplets and with the proper choice of surfactant, droplet diameters of less than 1 pm can be obtained. Such dispersions are sufficiently stable for most applications. 

An acid value is referred to an amount (mg) of potassium hydroxide added to neutralize 1 g of a resin when the resin is dissolved in an organic solvent such as toluene. From Table 2, four alkyds were formulated with an acid value between 15-20 mg KOH gr where these values falls within the preferable range (5-60 mg KOH g ) of acid value of an alkyd. It is important to obtain an acid value of alkyd resin at least 5 in order to synthesize alkyds at a low cost with lower acidity. However, an acid value of alkyd is preferably at most 60 to enable reasonable high cross-linking density in order to prevent the deterioration of an abrasion appearance or lowering of hardness during miming. 

Formulating Considerations Do not heat above 40°C. May partially neutralize acid resins—adjustment of base amount may be necessary Form Supplied Clear yellow liquid Supplier Croda... 

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