Resins concentration

Laminates. Laminate manufacture involves the impregnation of a web with a Hquid phenoHc resin in a dip-coating operation. Solvent type, resin concentration, and viscosity determine the degree of fiber penetration. The treated web is dried in an oven and the resin cures, sometimes to the B-stage (semicured). Final resin content is between 30 and 70%. The dry sheet is cut and stacked, ready for lamination. In the curing step, multilayers of laminate are stacked or laid up in a press and cured at 150—175°C for several hours. The resins are generally low molecular weight resoles, which have been neutralized with the salt removed. Common carrier solvents for the varnish include acetone, alcohol, and toluene. Alkylated phenols such as cresols improve flexibiUty and moisture resistance in the fused products. 

Fig. 6. Upper temperature limit of solubihty in salt solution. Resin concentration is 5.0 wt % (10).

Aqueous Solution Viscosity. A special solution preparation method is used for one type of measurement of aqueous solution viscosity (96). The appropriate amount of poly(ethylene oxide) resin is dispersed in 125 mL of anhydrous isopropyl alcohol by vigorous stirring. Because the resin is insoluble in anhydrous isopropyl alcohol, a slurry forms and the alcohol wets the resin particles. An appropriate amount of water is added and stirring is slowed to about 100 rpm to avoid shear degradation of the polymer. In Table 4, the nominal resin concentration reported is based on the amount of water present and ignores the isopropyl alcohol. 

Analysis for Poly(Ethylene Oxide). Another special analytical method takes advantage of the fact that poly(ethylene oxide) forms a water-insoluble association compound with poly(acryhc acid). This reaction can be used in the analysis of the concentration of poly(ethylene oxide) in a dilute aqueous solution. Ereshly prepared poly(acryhc acid) is added to a solution of unknown poly(ethylene oxide) concentration. A precipitate forms, and its concentration can be measured turbidimetricaHy. Using appropriate caUbration standards, the precipitate concentration can then be converted to concentration of poly(ethylene oxide). The optimum resin concentration in the unknown sample is 0.2—0.4 ppm. Therefore, it is necessary to dilute more concentrated solutions to this range before analysis (97). Low concentrations of poly(ethylene oxide) in water may also be determined by viscometry (98) or by complexation with KI and then titration with Na2S202 (99). 

Formaldehyde may react with the active hydrogens on both the urea and amine groups and therefore the polymer is probably highly branched. The amount of formaldehyde (2—4 mol per 1 mol urea), the amount and kind of polyamine (10—15%), and resin concentration are variable and hundreds of patents have been issued throughout the world. Generally, the urea, formaldehyde, polyamine, and water react at 80—100°C. The reaction may be carried out in two steps with an initial methylolation at alkaline pH, followed by condensation to the desired degree at acidic pH, or the entire reaction may be carried out under acidic conditions (63). The product is generally a symp with 25—35% soHds and is stable for up to three months. 

Class and Chu [34] have studied the tackification of natural rubber and SBR over a wide range of resin concentrations for several tackifiers. From their graphical data it can be estimated that 1 1 tackification (by weight) with a poly(/-butyl styrene) resin, MW 850 and Tg = 59°C, gives a PSA with Tg about — 13°C, and storage modulus, G about 8.8 x 10 Pa, well within the PSA window. 

Viscosity. Solvent viscosity of resins is influenced by the concentration of resin, the softening point, the molecular weight distribution, the chemical composition of the resin, and the type of solvent. The higher the resin concentration, the higher the viscosity. For a given concentration, solution viscosity depends on the softening point of the resin (Fig. 22). 

P23 Adsorption - Resin concentrations (at standard temperature and pressure) as ... 

The postulated and sufficiently proven notion that asphaltenes are oxidation products of resins and that resins are oxidation products of oil (11) sort of makes the probability of finding oils whose actual resin concentration is less than their critical resin concentration small. In other... 

Plant parts often differ in their levels of secondary metabolites (Table 11.4), some containing extremely high levels. For example, the creosote bush, Larrea tridentata, of the western United States has phenolic resins concentrated in leaves, amounting to as much as 18% of dry weight. In experiments, desert woodrats, Neotoma lepida, selected plant parts of creosote bush with low levels of resins (Meyer and Karazov 1989). 

Figure 1. Schematic of resin concentration system. Filter is a replaceable Carborundum K-27 3.0-pM filter in a 90 X 270-mm stainless steel holder. The pump is a MUton-Roy FR 141-144 Teflon diaphragm type capable of 1500 lb/in.2 of pressure and a maximum flow rate of 40 L/h. A hydrodyne pulse dampener precedes the columns. All resins are packed in 49-mm i.d. stainless steel columns the XAD-2 column was 204 mm long, and the others were 102 mm long. Column effluent flow was split between the...

Polyox resin-grade Approx, mol wt Nominal resin concentration, wt % Brookfield viscometer spindle number Speed, rpm Viscosity at 25°C, Pa-sb... 

The solvent is distilled from polyalumophenylsiloxane in the same apparatus, 8. Before the distillation the product is clarified at 45-50 °C. The settled water is poured into collector 18 the clarified product (after switching inverse cooler 9 into the direct mode) is distilled to separate the toluene and butanol or ethanol mixture at a residual pressure of 800 65 GPa. The distillation temperature gradually rises to 90 °C. The distillation is considered finished when the resin concentration in the varnish is 40-65%. The vapours of the distilled solvent enter water cooler 9. There they condense and flow into receptacle 14. 

The sodium salts were dissolved in 200 cc. of cold water and immediately passed over a cation-exchange resin. Concentration of the resulting sodium-free solution at reduced pressure followed by concentration with absolute ethanol produced a crystalline residue. Fractional crystallization of this residue from absolute ethanol yielded 6.5 g. (18.5%) of 1-mtro-l-desoxy-L-mannitol and 6.6 g. (18.8%) of 1-nitro-l-desoxy-L-glucitoI. After recrystallization from absolute ethanol, the former compound showed m. p. 133-134°, [< ] , 7.0°, in water, while the latter compound showed m. p. 107-108°, [a] 9.5°, in water. 

The fabrication of composite laminates having a thermosetting resin matrix is a complex process. It involves simultaneous heal, mass, and momentum transfer along with chemical reaction in a multiphase system with time-dependent material properties and boundary conditions. Two critical problems, which arise during production of thick structural laminates, are the occurrence of severely detrimental voids and gradients in resin concentration. In order to efficiently manufacture quality parts, on-line control and process optimization are necessary, which in turn require a realistic model of the entire process. In this article we review current progress toward developing accurate void and resin flow portions of this overall process model. 

---