Resins, nonreactive

When reactive (carboxyl groups present) resins are used, the pebble mill, or color chip techniques are most frequently encountered. (The color chip is prepared with a nonreactive resin.)... 

Phenolic resins are of two types, reactive and nonreactive. Nonreactive resins tend to be oligomers of alkyl-phenyl formaldehyde, where the para-alkyl group ranges from to C4 to C9. Such resins tend to be used as tackifying resins. Reactive resins contain free methylol groups. In the presence of methylene donors such as hexamethylenetetramine, crosslink networks will be created, enabling the reactive resin to serve as areinforcing resin and adhesion promoter. 

The primary chemical classes from which adhesives are made include epoxies, acrylics, phenolics, urethanes, natural and synthetic elastomers, amino resins, silicones, polyesters, polyamides, aromatic polyheterocyclics, and the various natural products such as carbohydrates and their derivatives as well as plant- and animal-based proteins. Chemical class was once a relatively clean differentiator of adhesives, but so many adhesives now are hybrids, designed to take advantage of specific attributes of more than one chemical class or type of material. Hybridization can be accomplished by incorporating into an adhesive a nonreactive resin of a different chemical class adding another type of reactive monomer, oligomer,... 

Nonreactive resins with a variety of compositions are of considerable importance in the formulation of adhesives. In some cases, they are used on their own in solvent adhesives, so-called resin adhesives, but generally in combinations with polymers, in which they perform various functions. Above all, they increase tack, improve adhesion, influence viscosity, fluidity, and scalability, and, in some cases, also act as plasticizers. The most important applications for nonreactive resins are in pressure-sensitive adhesives, contact adhesives, hot-melt adhesives, solvent adhesives, and emulsion-based adhesives. In this context, the term resin covers materials differing very widely in their composition ... 

Composition (wt. parts) Nonreactive Resin Reactive Resin... 

Petroleum resins are low molecular weight thermoplastic hydrocarbon resins synthesized from steam cracked petroleum distillates. These resins are differentiated from higher molecular weight polymers such as polyethylene and polypropylene, which are produced from essentially pure monomers. Petroleum resin feedstocks are composed of various reactive and nonreactive aliphatic and aromatic components. The resins are usually classified as C-5... 

Chemical Properties and Reactivity. LLDPE is a saturated branched hydrocarbon. The most reactive parts of LLDPE molecules are the tertiary CH bonds in branches and the double bonds at chain ends. Although LLDPE is nonreactive with both inorganic and organic acids, it can form sulfo-compounds in concentrated solutions of H2SO4 (>70%) at elevated temperatures and can also be nitrated with concentrated HNO. LLDPE is also stable in alkaline and salt solutions. At room temperature, LLDPE resins are not soluble in any known solvent (except for those fractions with the highest branching contents) at temperatures above 80—100°C, however, the resins can be dissolved in various aromatic, aUphatic, and halogenated hydrocarbons such as xylenes, tetralin, decalin, and chlorobenzenes. 

Treatments with Chemicals or Resins. Resin treatments are divided into topical or chemical modifications of the fiber itself. Most chemical treatments of synthetic fibers are topical because of the inert character of the fiber itself and the general resistance of the fiber to penetration by reagents. By contrast, ceUulosics and wool possess chemical functionality that makes them reactive with reagents containing groups designed for such purchases. Natural fibers also provide a better substrate for nonreactive topical treatments because they permit better penetration of the reagents. 

The most important coating appHcation for the nonreactive polyamide resins is in producing thixotropy. Typical coating resins such as alkyds, modified alkyds, natural and synthetic ester oils, varnishes, and natural vegetable oils can be made thixotropic by the addition of dimer acid-based polyamide resins (see Alkyd resins). Specialty high performance coating appHcations often requite the properties imparted by dimer acid components. 

Reactive Polyamide Resins. Another significant commercial appHcation of dimer acids is in reactive polyamide resins. These are formed by the reaction of dimer acids with polyamines such as diethylenetriamine to form polyamides containing reactive secondary amine groups (see DiAMlNES AND HIGHER AMINES, aliphatic). In contrast to nonreactive polyamides, these materials are generally Hquids at 25°C. 

Depending on the characteristics and performance requirements, adhesives systems are frequendy modified with diluents (reactive and nonreactive) and polyfunctional high performance resins, as weU as with fillers of various types. 

Solvents used as nonreactive diluents include acetone, cellosolve, methyl ethyl ketone, methyl isobutyl ketone, methylene chloride, 1,1,1-trichloroethane, toluene, and xylene. Skin and eye irritation and, in higher concentrations, CNS depression and respiratory irritation may result ftom exposure to these solvents as diluents for epoxy resin... 

The resulting resins were mixed with 20% acetic anhydride in DMF (200 pL) at room temperature for 10 min, for capping of nonreacted amines. After washing with NMP (6 times), EtOH (1 time), and 20% EtOH (1 time), in series see Note 11), the resins were kept at 4°C in an aqueous solution of 20% EtOH until the binding experiment. 

In a dynamic and cross-linkable system, such as the curing of a thermoset that contains a thermoplastic, the phase separation is more complicated than nonreaction system. The phase separation is controlled by the competing effects of thermodynamics and kinetics of phase separation and cure rate of thermoset resin (i.e. time dependent viscosity of the system). 

Tetrabromobisphenol A is used in epoxy resins especially for glass fiber reinforced used in printed circuit board. Nonreactive compounds such as tetrabromophatalate ester, bis(tribromophenoxy) ethane, and decabromodiphenyl ether are also used. The use of synergists, such as antimony oxide, reduces the quantity of brominated flame retardant necessary but decreases the electrical properties required. 

Chigwada et al.36 have combined polyhedral oligosilsesquioxanes (POSS), which are cage-like hybrid molecules of silicon and oxygen, with TCP (tricresylphosphate) in poly(vinyl ester) resins (PVE). POSS molecule contains nonreactive organic functionalities allowing solubility and compatibility of the POSS with various polymers. POSS was incorporated alone (3-10 wt %) in PVE, and four compositions were made with TCP at 4wt % POSS + 4wt % TCP and 5wt % POSS + 5, 10, 15 wt % TCP. Fligh reductions in PHRR and THR were noticed. Nevertheless, the POSS/ TCP combination did not exhibit better performances than compositions with only 5 or 10 wt % of TCP alone. 

An ingredient added to an adhesive to reduce the concentration of base resin or binder is called a diluent. Diluents are principally used to lower the viscosity and modify the processing conditions of some adhesives. The degree of viscosity reduction caused by various diluent additions to a conventional epoxy adhesive is shown in Fig. 1.5. Diluents do not evaporate as does a solvent, but they become part of the final adhesive. Reactive diluents react with the resin base during cure, so that the final adhesive characteristics are determined by the reaction product of the binder and diluent. Nonreactive diluents do not react with the resin or curing agent and, therefore, more seriously weaken the final properties. Coal and pine tar are common nonreactive diluents. 

Of course, in the case of both curing agents and catalysts, suitable adjustments will have to be made for the presence of nonreactive fillers and modifiers. Such ingredients can be liquids such as a solvent, a hydrocarbon resin, or a plasticizer. Since they do not contribute any epoxide functionality, they should not be considered when one is determining stoichiometry. However, if the additives have epoxy functionality, such as in the case of reactive diluents, the stoichiometric calculations will have to take these materials into consideration, by calculating ratios similarly as with an epoxy resin. 

Diluents have much lower vapor pressures and generally do not evaporate at ambient conditions. However, they do have a finite vapor pressure, and given the right set of conditions (time, temperature, and pressure) they will vaporize. Two distinct classes of diluents are used with epoxy resins nonreactive diluents and reactive diluents. Reactive diluents will enter into the crosslinking reaction with the primary resin, and nonreactive diluents will not. Nonreactive diluents primarily act as low-molecular-weight plasticizers for the epoxy composition. 

Coal and pine tar are examples of common nonreactive diluents from natural substances. These are interesting nonreactive diluents because of their relatively low cost. They are often used as extenders in epoxy systems to reduce the cost. Coal tar is widely used because of its excellent compatibility with epoxy resins and relatively small sacrifice in cured properties. Nonyl phenol, furfural alcohol, and dibutyl phthalate are also common nonreactive diluents for epoxy systems. Dibutyl phthalate is also used as a plasticizer in many thermoplastics, such as polyvinyl chloride. 

Dibutyl phthalate (Fig. 6.4) is a commonly used nonreactive diluent because it does not exhibit migratory tendencies on aging. It is generally incorporated into the DGEBA epoxy with heating. When it is used at about 17 pph, the viscosity of the resin can be reduced from... 

The monofunctional epoxy diluents are essentially chain stoppers since they inhibit crosslinks from forming. The extent to which the cured properties are affected is directly dependent on the concentration of the diluent added to the epoxy resin. The general effect is to reduce viscosity and improve the impact and thermal shock resistance while slightly reducing the thermal resistance. The thermal expansion of the cured resin is increased, as it is also with nonreactive diluents. This can lead to internal stress on the bond line depending on the thermal expansion of the substrate material. 

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