Elastomers plasticizers

Polymer systems have been classified according to glass-transition temperature (T), melting poiat (T ), and polymer molecular weight (12) as elastomers, plastics, and fibers. Fillers play an important role as reinforcement for elastomers. They are used extensively ia all subclasses of plastics, ie, geaeral-purpose, specialty, and engineering plastics (qv). Fillets are not, however, a significant factor ia fibers (qv). 

Hydrocarbon resins are used extensively as modifiers in adhesives, sealants, printing inks, paints and varnishes, plastics, road marking, flooring, and oil field appHcations. In most cases, they ate compounded with elastomers, plastics, waxes, or oils. Selection of a resin for a particular appHcation is dependent on composition, molecular weight, color, and oxidative and thermal stabiHty, as weU as cost. A listing of all hydrocarbon resin suppHers and the types of resins that they produce is impractical. A representative listing of commercially available hydrocarbon resins and their suppHers is included in Table 6. 

Foam Production This is important in froth-flotation separations in the manufac ture of cellular elastomers, plastics, and glass and in certain special apphcations (e.g., food products, fire extinguishers). Unwanted foam can occur in process columns, in agitated vessels, and in reactors in which a gaseous product is formed it must be avoided, destroyed, or controlled. Berkman and Egloff (Emulsions and Foams, Reinhold, New York, 1941, pp. 112-152) have mentioned that foam is produced only in systems possessing the proper combination of interfacial tension, viscosity, volatihty, and concentration of solute or suspended solids. From the standpoint of gas comminution, foam production requires the creation of small biibbles in a hquid capable of sustaining foam. 

Elastomers, plastics, fabrics, wood and metals can be joined with themselves and with each other using nitrile rubber/epoxy resin blends cured with amines and/or acidic agents. Ethylene-propylene vulcanizates can also be joined using blends of carboxylated nitrile rubber, epoxy resin and a reactive metal filler (copper, nickel, cobalt). However, one of the largest areas of use of nitrile rubber modified epoxy systems is in the printed circuit board area [12]. 

The processing technologies for elastomeric blends, thermoplastic elastomer-based on mechanical mixing, and elastomer-plastic vulcanizates are distinctly different. Depending on the type and nature of blend, size, and their final application, a wide range of processing equipment is now in use both industrially as well as in laboratory scale preparation. 

B. Preparation of Elastomer-Plastic Blend by Melt Mixing Without Vuicanization... 

Elastomer-plastic blends without vulcanization were prepared either in a two roll mill or Banbury mixer. Depending on the nature of plastic and rubber the mixing temperature was changed. Usually the plastic was fed into the two roll mill or an internal mixer after preheating the mixer to a temperature above the melting temperature of the plastic phase. The plastic phase was then added and the required melt viscosity was attained by applying a mechanical shear. The rubber phase was then added and the mixture was then melt mixed for an additional 1 to 3 min when other rubber additives, such as filler, activator, and lubricants or softeners, were added. Mixing was then carried out with controlled shear rate... 

C. Preparation of Elastomer-Plastic Blends by Static Vulcanization... 

Unlike incompatible heterogeneous blends of elastomer-elastomer, elastomer-plastic, and plastic-plastic, the reactively processed heterogeneous blends are expected to develop a variable extent of chemical interaction. For this reason the material properties, interfacial properties, and phase morphology of reactively processed blends would differ significantly from heterogeneous mixtures. 

B. Properties of Conventionally Vulcanized Elastomer-Plastic Blends... 

In the preceding sections, our discussion has been limited to softer grade elastomer-plastic vulcanizates. Commercial interest, however, also centers on another major family of polymer blends, semi-rigid impact resistant polyolefins. Thus, we report some of our findings on PRP triblock copolymer and EVA rubber blends without... 

Electron and optical microscopes are being used to see blend homogeneity. Elastomer-plastic blends are somewhat easier to identify than elastomer-elastomer blends because normal staining techniques, e.g., osmium tet-raoxide, can be used in the case of plastic-elastomer blends. Normally, there are two methods that are followed for examining the blend surface by electron microscopy. 

The use of special elastomer plastics (polyurethanes, silicones, etc.) designed ex-... 

Burg. Stolklaan 16, 4002 WJ Tiel, The Netherlands Tel +31 (0) 344 616 161 Fax +31 (0) 344 631 014 E-mail info schouenberg.demon.nl SOFINE includes detailed technical information of more than 11,000 plastics (thermoplastics and elastomers) plastic materials from over 100 producers continuous updating of the program operates in 7 languages. SOFINE versions available include ... 

Although they have an endless variety of properties, polymers can be divided into three general categories, based on their form and resistance to stretching. These are plastics, fibers, and elastomers. Plastics differ in form from fibers whereas plastics exist as blocks or sheets, fibers have been drawn into long threads. Unlike plastics or fibers, elastomers can be stretched without breaking. Polyethylene packaging films and polyvinylchloride (PVC) pipe are examples of plastics. Orion carpets are made from polymer fibers, and mbber bands are elastomers. Some polymers, such as Nylon, can be formed into both plastics and fibers. 

The lower limit 100 for the DP of high polymers has been established because the physical properties needed for useful fibres, elastomers, plastics and coatings, are not characteristic of low Molecular weight polymers. However, there is no upper limit for DP. Thus, the average Molecular weight for most Synthetic polymers is 10,000 to 1,00,000. However, in some cases, Molecular weights of over 100 millions have been found. 

Ethylene/propylene products reign supreme among the copolymers. They are elastomers. Plastics containing about 20% or more propylene perform like natural rubber and can be cured by peroxide cross-linking. They are faster to chemical and to ageing than other types of natural rubber. 

Effect of Creep and Other Time Related Factors on Plastics and Elastomers, Plastics Design Library, New York, 1991. 

The EVAs make it possible to produce compounds with high filler levels and are compatible with many elastomers, plastics and other materials SBR, butyl rubber, EPDM, nitrile rubber, Hypalon, thermoplastic elastomers, epoxies, PVC, PVDC, bitumen. 

While polymeric hydrocarbons have been used as illustrations for simplicity, it is important to note that the principles discussed apply to all polymers, organic as well as inorganic, and natural as well as synthetic, and to elastomers, plastics, and fibers. 

Thermoplastic elastomers based on polyolefins (TPO) are blends of PE or PP wifh EPDM elastomers wherein the elastomer is often cross-linked using thermochemical systems. TPOs more suitable for medical producfs with no chemical residuals can be made using EB processing to cross-link the elastomer portion in such an elastomer-plastic blend. The thermoplastic governs the melt transition, and thus the extrusion properties of TPOs. The radiahon response of these materials is also governed by the choice of fhe thermoplastic. An example of an EB cured blend of EPDM and polyefhylene used is for fluid transmission tubing and electrical insulation. ... 

Cyclopentene is readily available as a byproduct in the ethylene production. Norbornene 2-ethylhexyl carboxylate is obtained by the Diels-Alder reaction of 2-ethylhexyl acrylate with cyclopenta-diene (5). Norbornene isobornyl carboxylate, norbornene phen-oxyethyl carboxylate, and other related monomers are synthesized according to the same route. Polymers obtained from these esters exhibit excellent properties in terms of controlling the crosslinking density, the associated product modulus, and the glass transition temperature (Tg), thus allowing tailoring the properties of elastomers, plastics and composites. Other suitable monomers are summarized in Table 1.1 and sketched in Figure 1.2. 

By varying the nature of the side chain, R, various elastomers, plastics, films, and fibers have been obtained. These materials tend to be flexible at low temperatures, and water and fire resistant. Some fluoroalkoxy-substituted polymers (R = CHXFJ are so water repellent that they do not interact with living tissues and promise to be useful in fabrication of artificial blood vessels and prosthetic devices. 

Aping (elastomers, plastics, leather, food products). 

Caps, Corks, and Wire Hoods. Crown caps are used for closures on bottles before secondary fermentation. The caps are 26 mm in diameter (one company uses 29 mm) and are coated tinplate or stainless steel. Two companies use stainless steel to prevent corrosion and leakage during storage under moist and cold conditions, or for long aging under high pressure. The liners of the caps are ground cork with vinyl disks or elastomer plastic. Cork and plastic liners appear to work equally well. 

---