Blending modification advantages

Barrier films of exfoliated clay-polymer composites have been a subject of considerable investigation with some commercial utility (e.g., barrier layer for termis balls).The thin exfoliated clay platelets dispersed in a polymer matrix present a tortuous diffusion path for gas molecules similar to that observed in Figure 12 for biaxially oriented polymer blends. The advantages of exfoliated clay modification for barrier properties are the retention of transparency and low cost. A novel approach utilizing nanocomposites involves dispersion of the exfoliated clay in a water emulsion or suspension and coating a desired substrate. This approach has been commercialized by IntMat for tennis balls, tires, and food packaging applications. For exceptional barrier properties, and where transparency is not required, metalized polymer films or aluminum foil polymer film laminates are usually employed. 

The property of polybutadiene of most interest to the mbber compounder is excellent abrasion resistance coupled with excellent resilience. The polymer has very high rebound and low heat generation. With a few exceptions, such as the core of soHd golf balls, the polymer is blended with other polymers to take advantage of its excellent abrasion and rebound. Uses in North America are as follows tires, 500,000 t (74%) plastic modification,... 

The blending of a BMI with a powder of a thermoplastic polymer without solvent offers a great advantage for the processing. Some results have been published based on a non-disclosed formula BMI blended with the CIBA GEIGY Matrimide 5218. The addition of 20% of powder did not require a modification of the cure cycle and an improvement in the mechanical properties (inhibition of crack propagation) was observed [115]. 

Probably a majority of practical expansive cements have depended on the modification of a Portland cement in such a way as to increase the formation of ettringite. Single expansive cement clinkers can be made, but it has been more usual to produce admixtures that are blended or interground with a normal Portland cement or clinker. Blending has the advantage that the... 

The other major alternative fuel is ethanol. Ethanol is more polluting, although less so than petrol, but it has the advantage in that it can be blended with petrol or used by itself (with minor modifications to the engine). 

The finding that the PEIs of 27b and monosubstituted hydro quinones form broad nematic phases, but show little propensity to crystallize, has prompted various modifications of their structures and properties. In this connection it should be stated that non-crystalline LC-polymers have found little interest in the past decades, but they may be attractive for various applications provided that the Tg can be varied between 90 and 250 °C. For instance, the absence of crystallinity has the advantage that the mechanical properties do not depend on the thermal history, and thus on the processing conditions. The temperature allowing a convenient processing may be reduced below 200 °C, which is of interest for the processing of LC-polymer reinforced blends and composites. Furthermore, non-crystalline nematic FC-polyesters are a useful basis for the synthesis of cholesteric lacquers, films or pigments (Sect. 5). 

Specifically, PVC blends with polyethylene, polypropylene, or polystyrene could offer significant potential. PVC offers rigidity combined with flammability resistance. In essence, PVC offers the promise to be the lowest cost method to flame retard these polymers. The processing temperatures for the polyolefins and polystyrene are within the critical range for PVC. In fact, addition of the polyolefins to PVC should enhance its ability to be extruded and injected molded. PVC has been utilized in blends with functional styrenics (ABS and styrene-maleic anhydride co-and terpolymers) as well as PMMA offering the key advantage of improved flame resistance. Reactive extrusion concepts applied to PVC blends with polyolefins and polystyrene appear to be a facile method for compatibilization should the proper chemical modifications be found. He et al. [1997] noted the use of solid-state chlorinated polyethylene as a compatibilizer for PVC/LLDPE blends with a significant improvement in mechanical properties. A recent treatise [Datta and Lohse,... 

Today, very few unmodified resins are being used. Some polymers require less modification then others. For example, the semi-crystalline polymers that already have a two-phase structure may need modification less urgently. By contrast, the amorphous resins, such as PVC, PS, PPE, or polycarbonate of bis-phenol-A (PC), are brittle and require blending more frequently. The advantages of blending fall into two categories. 

Pullulan films have several other advantages. The films are colorless, tasteless, odorless, transparent, resistant to oil and grease, and heat sealable. The properties of the films can be modified by chemical modification of pullulan, blending with poly-vinylalcohol, gelatin, or amylose, and by addition of plasticizers. These properties indicate that pullulan can be used as a coating or packaging for foods to prevent their oxidation. This is the only apparent outstanding application for pullulan. 

The behavior of nanocomposites, in which the filler can interact with the host polymer via specific secondary interactions, is similar to that of the hydrogen-bonded blends, but may have even greater potential for reducing aging rates. Nanocomposites also have several advantages over the blends, such as the use of common polymers that require little or no chemical modification, the ability to vary the polymer-filler composition relatively easily, and the ready availability of economical filling materials. Clearly, this group of materials deserves further study. 

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