Resin Characterization

Extensive use of the three-dimensional solubility parameters for predicting adhesion seems not to have been made, although its additional flexibility should make it successful over a wider range of conditions than the single-parameter approach. Some recent studies involving dental adhesion employed the method with success. Asmussen and Uno fl40 successfully correlated the shear bond strength of various dental adhesive resins, characterized in terms of their three-... 

Epoxy resins are thermosetting matrix resins, characterized by the epoxide group [48,193], as shown in Figure 2.9. 

The characteristics of the three most common thermoset resin systems used in pultrusion are compiled in Table 11.2 [3]. It is noteworthy that unreinforced polyesters and vinylesters shrink 7-9% upon crosslinking, whereas epoxies shrink much less and tend to adhere to the die. These epoxy characteristics translate into processing difficulties, reduced processing speed, and inferior component surface finish. It is normal practice to use resin additives to improve processability, mechanical properties, electrical properties, shrinkage, environmental resistance, temperature tolerance, fire tolerance, color, cost, and volatile evaporation. It is normally the resin, or rather its reactivity, that determines the pulling speed. Typical pulling speeds for polyesters tend to be on the order of 10-20 mm/s, whereas speeds may exceed lOOmm/s under certain circumstances. Apart from the resins characterized in Table 11.2, several other thermosets, such as phenolics, acrylics, and polyurethanes, have been tried, as have several thermoplastics (as will be discussed in Sec. 11.2.6). 

UF resins, characterization, polymerization reaction, ageing, GPC/SEC, HPLC... 

All resins characterized in this work were produced according to the alkaline-acid process, which consists basically of three steps methylolation under alkaline conditions, condensation under acidic conditions, and neutralization and addition of the so-called final urea or last urea. 

Fourier transform infrared speetroseopy (FTIR) is a modem method for last analysis of phenolic resins [204,226,227], the modilied products [33,148,183,214], the curing process [218], and the erosslinked products. Several FTIR techniques are useful in phenolic resin characterization. The simplest method is transmission spectroscopy. This method requires an optimum optical density of the sample. Soluble prepolymers and soluble products may be examined as solutions using solvents i.e. triohloromethane, that are reasonably transparent over the range of400-4000 cm. Absorbance measurements can also be made on a thin film prepared by casting from solution. Solid, insoluble products may be mixed with potassium bromide and compessed at room temperature to an optical clear disk that can measured using the transmission method. 

In the case of reinforcements with pultruded composite materials performed directly in the processing plant, the geometry of the pultruded sheets can be chosen among those realized by the producers. In the case of pultruded composite materials, the percentage of fibers in the composite material usually does not exceed 65 %. Even if the mechanical properties of the composite materials are mainly given by the fibers, the properties of the matrix are also very important. For this reason, it is important to use resins characterized by very high mechanical properties, such as the epoxy resins. 

In recent years, epoxy resins have been nsed to realize optical disk matrices, lenses and prisms. However, the refractive index of conventional epoxy resins is low and their applications as optical materials where a high refractive index is reqnired are limited. For this reason, many efforts are being dedicated to synthesizing new optical epoxy resins characterized by a high refractive index, good mechanical properties and optimal thermal insulation. 

IRI Iribarren, J.I., Iriarte, M., Uriarte, C., and Iruin, J.J., Phenoxy resin characterization, solution properties, and inverse gas chromatography investigation of its potential miscibility with other polymers, J. Appl. Polym. Sci., 37, 3459, 1989. 

Ken Carlson and co-workers, from the U.S. Department of Agriculture, have reported that "vernonia" coatings can be obtained directly from vernonia oil by a standard baking procedure at 150< C for 30 minutes in the presence of different drier systems.Our initial goal is determination of the drying mechanism and compatibility of vernonia oil with alkyd and other resins, characterization of these "vernonia" coatings, evaluation of different drier systems, and eventually, improvement of their properties. 

The role of spectroscopy in polyethylene resin characterization is to determine the types and concentrations of chemical species present in the material. The chemical species detected in a polyethylene resin may be directly attached to the polymer molecules or part of independent smaller molecules. Chemical moieties incorporated into the polymer molecules include olefinic branches, comonomers, nnsaturation, and various oxidative products. Independent molecules that commonly occur include antioxidants, catalyst residues, and processing aids. Due to the enormous variety of chemical species that find their way into polyethylene, either deliberately or adventitiously, a detailed description of their qualitative and qnantitative determination is beyond the scope of this book. Those wishing to explore this area more deeply are directed to the works of Haslam et al, Koenig, and Snyder listed in the bibliography. 

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