Phenolic resins, curatives

Polypropylene Is derived from propylene, which was just discussed. The phenolic resin curative (methylol terminated, para-alkyl substituted, phenol-formaldehyde... 

Two important types of elastomeric polyolefin blends are reactor-made iPP/ EPR blends and postreactor blend iPP/EPDM. The latter is called thermoplastic vulcanizates (TPVs), produced by dynamic vulcanization of blends containing a thermoplastic and an elastomer. To make iPP/EPDM TPV, the two polymers PP and EPDM are mixed with curatives, such as peroxides, phenolic resins, or sulfur with accelerators, and dynamically cured in an extmder resulting in a blend consisting of micrometer-sized elastomer particles dispersed in the PP matrix (20-24). Paraffinic oils are added in the melt mixing process for viscosity control and cost. In iPP/ EPDM TPV, the crystalline iPP resin is normally the minor phase. Recently, polyolefin plastomers have been added to the class of elastomeric polyolefin blends. Polyolefin plastomers are ultralow molecular weight linear low density polyethylenes (ULMW-LLDPE). Nonelastomeric polyolefin blends are blends of polyolefins with mostly nonpolyolefin (other thermoplastic) matrices as mentioned earlier. 

TP Vs are prepared from blends of isotactic PP and EPDM with curatives, such as peroxides, phenolic resins, or sulfur, by using a process called dynamic vulcani-... 

Other curatives, which react through addition mechanisms are phenolic resins, particularly if the hydroxyl/epoxy reaction is catalysed using a tertiary amine (usually accomplished at elevated temperatures), thiols, polysulphides and mercaptans (can be formulated to give very rapid cures), polyetheramines (relatively slow cures, which can be accelerated with nonyl phenol), polyamides (less reactive than their amine counterparts) and amidoamines (characterized as having very long pot lives). 

The alternating copolymers of p-hydroxystyrene and p-isopropenyl-phenol with MA (Table A.6) have recently received a fair amount of study. These copolymers, with two different types of functional acid groups, are being studied in polyion complexes for membranes, detergent additives, epoxy resin curatives, rubber additives, coatings, adhesives, laminates, ion-exchange resins, and other applications. The equimolar 2-allylphenol and 2-methallyl-phenol-MA copolymers (Sec. 10.2.1) are potentially useful in many of the same applications.Maruzen Oil has announced their intention to produce and test market the p-hydroxystyrene copolymer. 

With EPDM/PP, the rubber is EPDM and the thermoplastic resin is polypropylene. Even though early patents show the vulcanizing agent to be sulfur with an accelerator such as 2-bis(benzothiazolyl)disulfide (MBTS) or tetramethyl thiuram disulfide (TMTD), these sulfur-based curatives are not used today for TPVs. Likely a methylol-terminated phenol-formaldehyde resin curative with a tin chloride activator is used. For a lighter color, sometimes a peroxide crosslinker is used instead. Also, paraffinic... 

Cements prepared from carboxylic butadiene-acrylonitrile copolymers blended with phenolic resins, like the analogous cements prepared with noncarboxylic butadiene-acrylonitrile copolymers, are adhesive agents for steel to rubber. Employed without curative agents, the carboxylic copolymers give better steel-to-rubber adhesion than the analogous noncarboxylic copolymers. Confirmation of this is cited in the patent literature. 

Phenolic materials go back to the patents of Baekeland and are based upon the reaction of phenol and formaldehyde to yield a lower molecular weight resinous material that can be formulated with other resins and sometimes other curatives to yield a paste adhesive or a film adhesive. When phenol and formaldehyde are reacted in the presence of an acidic catalyst with an excess of phenol versus formaldehyde, they yield what are known as novolac resins. These materials are soluble in organic solvents and do not react further with themselves thus, they need to have a curative added. That curative is most often hexamethylene tetraamine. Another type of phenolic resin can be generated with an excess of formaldehyde and under basic conditions. These materials, known as resole phenolics, will react with themselves to yield a ftilly cured phenolic and thus must be stored frozen in order to limit this reaction. Thus, resole phenolics do not need an external CTOsslinker. Resole phenolics are widely used in the binding of paper products and the bonding of wood. Adhesives based upon these materials were brittle and could only be used to bond wood, where it is still widely used. A more widely usable adhesive was developed during World War II which modified the very brittle phenolic adhesive with poly(vinyl formal) resins. These materials were... 

FTIR has shown the close similarity of most resins based on Bis-Phenol A and has helped narrow the focus of development on the curative as the principal contributor to successful formulation. For present applications oligomeric polyamide amines appear successful in meeting present criteria. However, the only objective analysis of cured resin to date exhibiting a correlation of measured value with success in creep resistance as well as adhesion is heat distortion temperature. The following presents a correlation of heat distortion temperatures and adhesion for several formulations tested. In most cases, pass/fail criteria was based on the majority of six samples tested. 

Epoxide adhesives comprise epoxy resin, many of which are prepared from phenols and epichlorohydrin, for example, the diglycidyl ether of bis-phenol A or bis-phenol F usually, these resins are a mixtnre of molecular weights blended to fit the applications. The most-common cnratives for epoxy resins are polyanfines (used in stoichiometric amounts), usually a chain-extended primary aliphatic amine, for example, diethylene triamine or triethylene tetraamine or chain-extended equivalents, which react rapidly with the epoxy resin at room temperature. Aromatic amines react slowly at room temperature but rapidly at higher temperatures. Most epoxide adhesives also contain catalysts, typically, tertiary amines. Dicyanimide is the most-common curative for one-component high-temperature-cured epoxide adhesives. Mercaptans or anhydrides are used as curatives for epoxide adhesives for specialist applications, for example, for high-speed room-temperature cures or for electronic applications. A smaller number of epoxide adhesive are cured by cationic polymerization catalysed by Lewis acids photogenerated at the point of application. Lewis acid photoinitiators include diaryliodonium and triarly sulphonium salts. See Radiation-cured adhesives. 

Reactive diluents are low viscosity mono- or difunctionai epoxies based on aiiphatic aicohols, diols, alkylated phenols or carboxylic acid that are used to reduce the viscosity of standard epoxy resins and react with curatives during the curing process (Figure 2.42). They tend to reduce chemicai resistance, heat resistance and hardness of the coatings. The difunctionai diluents have fewer negative effects than monofunctional diluents. Higher vapor pressure (volatility) of some of the reactive diluents increases their toxicity, heaith risks and problems with skin irritancy. 

Methylol-terminated para-alkyl-substituted phenol formaldehyde resin is used as the vulcanizing agent for compounds based on butyl and EPDM rubber. The alkyl group is usually octyl. It is commonly used to cure butyl rubber where superior heat resistance is needed. Therefore, this vulcanizing agent is commonly used as the curative to make butyl bladders for repetitive curing of tires. It is also sometimes used in dynamic vulcanization with a tin chloride activator to make thermoplastic vulcanizates (TPVs). 

The alternative approach involves the determination of the water uptake by the adhesive, checking at the same time that the difihision leading to saturation obeys Pick s two laws, deducing the diffusion constant from the rate of uptake of water and thence calculating the distribution of water in the joint. These steps are outlined by Comyn (1981) together with data on a number of epoxide-curative combinations. The epoxide resins were aU based on the commonly used bis phenol A with various amine curing agents. 

Furan no-bake resins are two-component, r.t.-cur-ing, acid-catalyzed systems of furfiiryl alcohol prepolymer with additional monomer. Hot and warm box resins are mainly based on urea-modified fur-ftiryl alcohol-formaldehyde condensates that are cured at 100-170 °C. Also phenol-formaldehyde resins, modified with furfiiryl alcohol, are used. In cold box binder systems, the sand is mixed with a low-viscosity fiiran resin and a peroxide. The core is formed, and SO2 is blown into or generated in situ in the sand to cure the resin rapidly. 

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