Properties of Phenolic Resins

Moulding compound Tensile strength (MPa) Tensile modulus (GPa) Strain at break (%) Flepoiral strength (MPa) Compressive strength (MPa) 

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Table 23.3 Average physical properties of phenolic resin-based laminates...

Important properties of phenolic resins are their hardness, corrosion resistance, rigidity, and resistance to water hydrolysis. They are also less expensive than many other polymers. 

Experiment 2. Effect of Molar Ratio of Sodium Hydroxide to Phenol of Phenolic Resin on Strength Properties of Lignin-Phenolic Resin Adhesives. Sodium hydroxide has been the predominant chemical used as a catalyst in resol resin technology. Through variation in the amounts of the catalyst and the method of catalyst addition, a wide variety of resin systems can be formulated. This experiment examined the properties of phenolic resins formulated with various sodium hydroxide/phenol ratios and their effects on the bond properties of structural flakeboards made with lignin-phenolic resin adhesive systems. Variables for resin preparation were four molar ratios of sodium hydroxide/phenol (i.e., 0.2, 0.45,0.7, and 0.95). The formaldehyde/phenol ratio and solids content were fixed at 3/1 and 42%, respectively. 

Phenolic Resin Properties. Average physical and chemical properties of phenolic resins as affected by molar ratio of formaldehyde/phenol are summarized as follows ... 

Table II. Effect of Molar Ratio of NaOH/Phenol on Physical and Chemical Properties of Phenolic Resins...

The cross-linked polymers obtained from the addition-cure approach are often a complex arrangement of atoms bonded in heterocyclic and carbocyclic rings. However, the objective in the preparation of these systems is not simplicity. It is to obtain systems with the desirable properties of phenolic resins retained and the undesirable properties improved or removed. Voids are an undesirable result in the synthesis of both resols and novolacs. Hence, addition-cure phenolic resins are designed to avoid this result. Ease and flexibility of processing are also sought in the addition-cure systems. 

Phenolic resins continue to be an important material at both the commercial and the research levels. These complex systems are fascinating not only because of their current usefulness, but also because of their potential to become even more useful materials of the future. The classical phenol-formaldehyde system is deceptively simple and lends itself to much variation depending on factors such as pH, molar ratio of reactants, preparation/cure temperature, and curing agents. The desire to enhance the properties of phenolic resins and expand the processing options has led to considerable work on modified-classical and nonclassi-cal phenolic resins. 

Choi, M.H. In, J. Mechanical and thermal properties of phenolic resin-layered silicate nanocomposites synthesized by melt intercalation. J. Appl. Polym. Sci. 2003, 90 (9), 2316-2321. 

Fire resistance is an important property of phenolic resins. The combination of phenolic resin with Expancel expandable microspheres leads to many useful products. Composites for high speed train interiors take advantage of the light weight, excellent fire rating, and very low thermal conductivity. Polyester filled with aluminum hydroxide is an alternative solution for train interior materials. The resin and filler can be easily processed when viscosity regulating additives are added. 

There is ample evidence that the structural properties of phenolic resins such as novolac and poly (hydroxy styrene), as well as the inhibitors associated with them, do exert considerable influence on the dissolution properties of the DNQ/ novolac resist. ... 

Yang, J.-B., et al.. Preparation and properties of phenolic resin-based activated carbon spheres with controlled pore size distribution. Carbon. 2002,49(6), 911-916. 

Cup-flow test n. A British standard test (B S 771) for measuring the flow properties of phenolic resins. A standard mold is charged with the specimen material and then closed under preset pressure. The time in seconds for the mold to close completely is the cup-flow index. 

Dynamic mechanical analysis provides a useful technique to study the cure kinetics and high temperature mechanical properties of phenolic resins. The volatile components of the resin do not affect the scan or limit the temperature range of the experiment. However, uncured samples must be supported by a braid, a scrim, or paper. This does not influence the kinetic results and can be corrected in the calculations of dynamic mechanical properties (qv). Recent DMA work on phenolic resins has been used to optimize the performance of structural adhesives for engineered wood products and determine the effect of moisture in wood product on cure behavior and bond strength (75-77). 

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