Thermosetting resins phenolic

Poly(hydroxyphenyl maleimide)-b-PBA was added to thermosetting phenol resin to improve heat resistance [63]. PVC blended with poly(vinyl copolymer having cyclohexyl maleimide group)-b-PVC showed improved heat resistance and tensile strength with thermal stability during processing [64]. 

Thermosetting phenolic resins in wood, 26 355 Thermosetting plastics... 

Acrylonitrile-Butadiene Elastomers. These polymers, the so-called nitrile rubbers , are used dissolved in ketone or other highly polar solvents. When they are compounded with thermosetting phenolic resins it is possible to obtain good resistance to elevated temperatures. 

Shell mold casting, which uses molds that are thin shells of sand bonded with a thermosetting phenolic resin. The shell is removed from the pattern and baked at 300--400°F (147-202°C) to completely set the resius. Finally the shells are assembled to complete the mold. 

Polymers with aromatic hydrocarbon backbone include polymers containing in their chain aromatic hydrocarbon rings, or alternating aromatic rings and aliphatic carbon groups. Thermosetting phenolic resins can be included in this class. 

Thermosetting phenolic resins form a separate class of polymers containing aromatic rings and aliphatic carbon groups in the polymeric network. These resins are formed from the reaction of phenol (or substituted phenols) with formaldehyde. The fully crosslinked macromolecule is insoluble and infusible. Other thermosetting resins are known in practice, some derived from the reaction of melamine or of urea with formaldehyde. Because these have a different chemical structure, containing nitrogen, they are included in a different class (see Section 15.3). 

THERMOSETTING PHENOLIC RESINS AND RELATED POLYMERS - General aspects... 

Thermosetting phenolic resins include a number of polymers, the most common being obtained from the condensation of phenol with formaldehyde. The OH group on the benzene ring increases the reactivity in the o- and p- positions leading to three reactive centers for the phenolic component, while formaldehyde acts as having two active centers that can lead to a fully crosslinked polymer. The process may take place in neutral or alkaline conditions when in the first stage of the reaction, compounds known as methylol derivatives are formed. The condensation of phenol with formaldehyde occurs randomly at ortho- or para- position of the phenol, as shown below ... 

Synthetic polymers are relatively recently introduced materials. The natural fiber wool has already been used since antiquity, but the first completely synthetic fibers have only been in use since 1940. Iron has been known as a working material for thousands of years, but the oldest thermoset, phenolic resin, has only been known since 1906, and the oldest completely synthetic thermoplast, poly(vinyl chloride-co-acetate), has only been commercially produced since 1928. Large-scale application of elastomers has only been known since the beginning of the 19th century, when natural rubber was used, but the first commercial synthesis of a completely synthetic elastomer, poly(2,3-dimethyl butadiene), was only made in 1916. Since this time, the commercial production of thermoplasts, thermosets, chemical fibers, and synthetic rubbers has increased strongly (Figure 33-2). 

These alloy adhesives are thermosetting phenolic resins blended with neoprene (polychloroprene) rubber. They are available in solvent solutions in toluene, ketones, or solvent mixtures, or as unsupported or supported films. The supporting medium may be glass or nylon cloth. Neoprene-phenolic adhesive may be used to bond a variety of substrates such as aluminum. 

Thermosetting phenolic resins are used for exterior particleboard, oriented strand board (OSB) and plywood panels. They are heat hardened. 

Resins based on para-substituted phenols can be either one-step or two-step, but they cannot cure to a thermoset state. In the manufacture of phenolic resins, smaller quantities of acetaldehyde and furfuraldehyde are used in addition to formaldehyde. Furthermore, resorcinol, bisphenol A, and p-alkylphenols are employed, in addition to phenol, when special properties are desired. Formaldehyde concentrations of 37-50 weight % in aqueous solutions are most commonly employed. The catalysts most frequently used are acids such as oxalic, hydrochloric, sulfuric, p-toluenesul-fonic, and phosphoric and bases such as sodium, calcium, and barium hydroxide. In the weakly acidic range metal carboxylates are employed. Thermoset phenolic resins are employed as structural adhesives for laminating and bonding applications. Para-alkyl-substituted resins are employed as tackifiers in contact adhesives, pressure-sensitive adhesives, and hot-melt adhesives. 

Thermosetting phenolic resins are used in combination with other components as friction materials for brake systems. The design of such systems should account for the need to maintain a stable and reliable friction force under a variety of conditions, such as wide ranges of pedal pressure, vehicle speed, temperature and humidity. Fibers correspond to one of the ingredients and are used as reinforcement. Aramid pulp performs well as a reinforcement fiber in such systems because of its good filler retention, leading to enhanced wear resistance and friction stability (Kim and Jang, 2000). 

This company specialises in the manufacture of a wide-range of thermosetting phenolic resins which are tailor made for customers within the following typical industries abrasives (flexible, non-woven and rigids), industrial laminates, refractory, foundry and ancillary products, paper-impregnation, friction materials and general laminating applications. Consequently no data sheets are published. 

MIL-P-8059A Thermoset Phenolic Resin Sheet and Tubes. Asbestos Paper and Cloth Reinforced... 

MIL-P-15037E Thermoset Melamine Resin Sheet, Glass Reinforced MIL-P-15047B Thermoset Phenolic Resin Sheet, Nylon Reinforced MIL-I-15126F Insulation Tape, Electrical, Pressure Sensitive and Thermoset Adhesive... 

These alloy adhesives are thermosetting phenolic resins blended with neoprene (polychloroprene) rubber. They are available in solvent solutions in... 

---