Plasticizer backbone

Therefore, one can expect two types of plasticizing action the more conventional type known in the prior art where a viscosity reduction arises from free volume effects (backbone plasticizers) and a second that acts ideally by diminishing the interchain association of the ionic groups on the polymer chain (ionic domain plasticizers). One would... 

Dioctyl phthalate (DOP) was used as a representative of the class of backbone plasticizers and glycerol as a plasticizer for ionic groups. Both systems were studied with S-PS (sodium salt) as the base polymer in which the base resin had a sodium sulfonate content of 1.78 mol %. Various quantities of the two aforementioned diluents were added to this resin. 

The data thus far have shown that S-PS can be plasticized effectively with respect to backbone and ionic domain plasticizers. By appropriate choice of the plasticizer type either the PS backbone or the ionic domains can be plasticized preferentially. By appropriate control of the metal sulfonate content and the polarity of the plasticizer used, flexible S-PS compositions possessing useful tensile properties are feasible. While this approach has substantial merit, it is apparent that simply increasing the level of a phthalate plasticizer to improve melt flow results in a substantial decrease in useful tensile properties. It would be desirable to use a given level of backbone plasticizer and adjust the melt flow of the entire composition by independently plasticizing the ionic domains. One approach to achieve this objective has been described in the plasticization of ionic groups in metal-sulfonated ethylene propylene terpolymers (9). In those systems, the incorporation of metal carboxylates as plasticizers can improve both flow behavior and tensile properties. It is of interest to determine if this class of plasticizers can be combined with the phthalate plasticizers used for the S-PS backbone to provide an improved balance of flow behavior and tensile properties for S-PS s. 

This study has shown that the strong physical cross-links in lightly sulfonated PS can be controlled by the use of suitable polar plasticizers. At the same time the PS backbone can be plasticized independently. By appropriate control of the backbone plasticizer, the ionic group plasticizer, the sulfonate level, and the cation, a family of flexible sulfonated plastics can be prepared possessing acceptable flow and tensile properties. Such flexible compositions are similar in some respects to plasticized PVC. 

The binder system of a plastic encapsulant consists of an epoxy resin, a hardener or curing agent, and an accelerating catalyst system. The conversion of epoxies from the Hquid (thermoplastic) state to tough, hard, thermoset soHds is accompHshed by the addition of chemically active compounds known as curing agents. Flame retardants (qv), usually in the form of halogens, are added to the epoxy resin backbone because epoxy resins are inherently flammable. 

Benzene, toluene, and xylene are made mosdy from catalytic reforming of naphthas with units similar to those already discussed. As a gross mixture, these aromatics are the backbone of gasoline blending for high octane numbers. However, there are many chemicals derived from these same aromatics thus many aromatic petrochemicals have their beginning by selective extraction from naphtha or gas—oil reformate. Benzene and cyclohexane are responsible for products such as nylon and polyester fibers, polystyrene, epoxy resins (qv), phenolic resins (qv), and polyurethanes (see Fibers Styrene plastics Urethane POLYiffiRs). 

The aromatic sulfone polymers are a group of high performance plastics, many of which have relatively closely related stmctures and similar properties (see Polymers containing sulfur, polysulfones). Chemically, all are polyethersulfones, ie, they have both aryl ether (ArOAr) and aryl sulfone (ArS02Ar) linkages in the polymer backbone. The simplest polyethersulfone (5) consists of aromatic rings linked alternately by ether and sulfone groups. 

Biodegradable polymers and plastics are readily divided into three broad classifications (/) natural, (2) synthetic, and (J) modified natural. These classes may be further subdivided for ease of discussion, as follows (/) natural polymers (2) synthetic polymers may have carbon chain backbones or heteroatom chain backbones and (J) modified natural may be blends and grafts or involve chemical modifications, oxidation, esterification, etc. 

Sihcone polymer plasticizers have historically been used in many formulations. These plasticizers (qv) are of the same Si—O backbone as the functional polymers but generally are terrninated with trimethyl groups which are unreactive to the cure system. This nonreactivity means that, if improperly used, the plasticizer can migrate from the sealant and stain certain substrates. Staining has been a widely pubHcized flaw of sihcone sealants, but the potential of a formulation to stain a substrate can be minimized or eliminated with proper formulation work. In general, this is accompHshed by not using plasticizers for formulations developed for stain-sensitive substrates. 

Other polymers used in the PSA industry include synthetic polyisoprenes and polybutadienes, styrene-butadiene rubbers, butadiene-acrylonitrile rubbers, polychloroprenes, and some polyisobutylenes. With the exception of pure polyisobutylenes, these polymer backbones retain some unsaturation, which makes them susceptible to oxidation and UV degradation. The rubbers require compounding with tackifiers and, if desired, plasticizers or oils to make them tacky. To improve performance and to make them more processible, diene-based polymers are typically compounded with additional stabilizers, chemical crosslinkers, and solvents for coating. Emulsion polymerized styrene butadiene rubbers (SBRs) are a common basis for PSA formulation [121]. The tackified SBR PSAs show improved cohesive strength as the Mooney viscosity and percent bound styrene in the rubber increases. The peel performance typically is best with 24—40% bound styrene in the rubber. To increase adhesion to polar surfaces, carboxylated SBRs have been used for PSA formulation. Blends of SBR and natural rubber are commonly used to improve long-term stability of the adhesives. 

SBR, polycarbonates, etc., can often be achieved by choosing a polyol backbone that is similar in polarity to the substrate to be bonded. For example, polyethers often work well for obtaining adhesion to these medium polarity plastics, whereas polyesters usually work better for polar substrates, such as glass and metal. 

The liquid nitrile rubbers are generally used as nonvolatile and nonextractable plasticizers. They also function as binders and modifiers for epoxy resins. Their moderate heat resistance limits their ability to meet industrial requirements. Hence, attempts have been made to improve their thermal and oxidative resistance by saturating the polymer backbone. 

A membrane ionomer, in particular a polyelectrolyte with an inert backbone such as Nation . They require a plasticizer (typically water) to achieve good conductivity levels and are associated primarily, in their protonconducting form, with solid polymer-electrolyte fuel cells. 

There are methods to manipulate the backbones of polymers in several areas that include control of microstructures such as crystallinity, precise control of molecular weight, copolymerization of additives (flame retardants), antioxidants, stabilizers, etc.), and direct attachment of pigments. A major development with all this type action has been to provide significant reduction in the variability of plastic performances, more processes can run at room temperature and atmospheric pressure, and 80% energy cost reductions. 

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