Cresol-formaldehyde resole

These resins (Resole or Novolac) are used as curing agents or hardeners for epoxy molding compounds for electronics applications such as computer components. 0-cresol-formaldehyde resins have heen also used to modify phenol-formaldehyde resins, and in laminates. 

Optical properties Mostly available in dark, opaque colours (novolaks), though transparent, unfilled castings are formed by reacting cresols or resourcinol with formaldehyde (resoles). May be painted or decorated by electroplating. 

Addition of p-cresol formaldehyde (PCF) into phenolic/NBR blends resulted in rednction in the domain size of the dispersed phase and improvement in mechanical properties [244]. PCF resin has an intermediate polarity compared with NBR and resole and can react faster with NBR. Therefore, PCF molecules are likely to be concentrated at the phenolic/NBR interface and act as an external compatibilising agents [245]. Thus compatibility and chemical bonding between NBR and phenolic resin is improved, leading to the enhancement in properties. The other materials used as toughening agents of phenolic resin include elastomers such as natural rubber and nitrile rubber [246, 247], reactive liquid polymers [248] and thermoplastics such as polysulfone, polyamide, polyethylene oxide [249, 250]. 

Cresol-, xylenol-, and phenol-formaldehyde resoles find importance in the electronics field application. These materials are made flexible with PVB, PVF and alkyds. They are used in impregnating, dynamo sheet, and wire varnish applications. 

ALKALINE PHENOLIC Resol - Alkaline phenol Formaldehyde resin 1. Gas hardened 2. Self-setting Particulate matter - soot fiom the inconqrlete combustion of carbon based resins Carbon oxides Formaldehyde Phenol, cresols and xylenols Aromatics Odom may be a problem... 

Phenolic resins are the reaction products of formaldehyde (usually in the form of aqueous formaldehyde), with phenol. Sometimes alkyl phenols, such as cresol and xylenol, are incorporated to reduce crosslink density and brittleness, although reactivity is also reduced. Phenolic resins are offered in two forms, novolacs and resols, characterised by their different methods of manufacture and curing. 

Phenolics which are formed when the molar ratio of formaldehyde to phenol is greater than one are called resoles. The phenol moieties are terminated with reactive hydroxymethyl groups (—CH2OH), known as methylol groups. If the mole ratio of formaldehyde to phenol is less than one, the polymer becomes phenol terminated and is called a novolak. All phenolic chemistry today revolves about these two basic chemistry strategies. Although phenol is most commonly involved in phenolics, resins containing p-r-butylphenol, p-r-amylphenol, p-nonylphenol, mixed cresols, and substituted... 

---