Elastomers, additives

Most of the phosphate esters are used in the production of hydrauHc fluids (qv), plastic and elastomer additives, flame retardants (qv), oil stabilizers, pesticides (qv), and medicinal intermediates (see Surfactants). Some trialkyl phosphates, OP(OR)2, are outstanding solvents for nitrates, especially (UO2) (N02)2, and therefore are important in uranium processing (see Extraction). 

FAB has been used to analyse additives in (un) vulcanised elastomer systems [92,94] and FAB matrices have been developed which permit the direct analysis of mixtures of elastomer additives without chromatographic separation. The T-156 triblend vulcanised elastomer additives poly-TMDQ (AO), CTP (retarder), HPPD (antiozonant), and TMTD, OBTS, MBT and A,lV-diisopropyl-2-benzothiazylsulfenamide (accelerators) were studied in three matrix solutions (glycerol, oleic acid, and NPOE) [94]. The thiuram class of accelerators were least successful. Mixture analysis of complex rubber vulcanisates without chromatographic separation was demonstrated. The differentiation of matrix ions from sample ions was enhanced by use of high-resolution acquisition. 

Among the butylenes, isobutylene has become one of the important starting materials for the manufacture of polymers and chemicals. There are many patents that describe the use of isobutylene or its derivatives to produce insecticides, antioxidants, elastomers, additives for lubricating oils, adhesives, sealants, and caulking compounds. Table 9 shows the use pattern of butylenes in the United States. 

CTBN and derivatives are also used in unsaturated polyester and vinylester resins but with less success. Studies have shown that the elastomer additive alone is very often immiscible in a polyester resin. 

Compared to the carboxylated nitrile elastomer additives, the use of thermoplastics has primarily been focused on the aerospace industry. On a cost per pound basis, the two-phase nitrile additives offer the best combination of property improvement without negative impact. The thermoplastic additives, however, may offer better high-temperature performance, but they are more difficult to formulate and to process as adhesives. As a result, the cost of these adhesives is generally much higher than that of other toughened epoxy mechanisms. 

In this work, we have investigated one aspect of this problem i.e. the effects of adding two types of particulate elastomeric additives and of filler content on two recognized stress factors (coefficient of thermal expansion and modulus) of a model molding compound. From this work, we have concluded that particulate elastomer additives can not only lower stress by modulus reduction but also by CTE reduction and possibly by reduced dimensional changes when the part cools from the molding temperature. 

Thermal mechanical analysis (Dupont 990/942 IMA), and dynamic mechanical analysis (Dupont 1090/982 DMA) curves for a designed set of model formulations were evaluated for CTE and tensile storage modulus as a function of filler level and elastomer additive type and level. Fifteen formulations were prepared with 68-75% filler, 0-4% silicone elastomer A, 0-4% non-silicone elastomer B and the balance 17-32%. Both elastomers have Tg s below room temperature. An extreme vertices formulation design was generated by computer (Table I). 

Chart I. Chemical structures and characteristics of dicyanate monomers, elastomer additives, and PES additives. 

It was said that they had low TgS (ranging from - 26 to - 86 °C) and exhibited the highest degree of thermal and oxidation stability that has been observed so far for any elastomers . Additionally they were supposed to be promising candidates for potential applications as flame-retardant elastomers, one of the critical needs in many industrial branches such as the aircraft and automotive industry. 

Polyurethane-based plasticizers can be obtained as a product of hydrolysis of poly-methane scrap as described elsewhere for material from printing rollers.These plasticizers were used to modify acrylonitrile-butadiene rubber.In still another development, diurethane was used in polyurethane elastomers. " Addition of diurethane improved potlife, and mechanical properties. The plasticizer performed better than DOP and it was substantially less migrating than DOP. " ... 

Other important polymers for the additives business include the styrenics and ABS, the polyesters PET and PBT, the polyamides, acrylics, thermoplastic polyurethanes and thermoplastic elastomers. Additives are widely used in blends too. 

Rynite DuPont PET elastomer addition of elastomer does not lower weather stability of PET... 

MRE composites were prepared according to the commonly used methods. It was found that micro- and nano- sized iron oxides and carbonyl iron powder were active fillers improving mechanical properties of elastomers. Additionally, they... 

Formation of a strong interfacial layer is the key factor of the mechanism describing retardation of ozone degradation of a diene rubber by elastomer additives with a low degree of unsaturation [1-4]. The effect of comonomer ratio in ethylene-propylene-diene terpolymers (EPDMs) and stereoregularity of propylene units on the interfacial interaction and the amount of crosslinks in ihe interfacial layer was considered for heterophase crosslinked blends with butadiene-acrylonitrile mbbers (BNRs) of different polarities. 

Stress-strain relationships are determined by DMA and temperature scans reveal glass transitions, crystallization and melting information. Blends of polypropylene and rubber have been studied by where the intensity of one of the two crystallization exotherms was used as a measure of the polypropylene domains and compared to the size determined by TEM cryomicrotomy and osmium tetroxide staining methods [25]. Isothermal annealing of PET above the crystallization temperature was shown to influence the morphology and increase thermal stability by combined SAXS and DSC analysis [26]. An excellent text edited by Turi [21] described the instrumentation and theory of thermal analysis and its application to thermoplastics, copolymers, thermosets, elastomers, additives and fibers. 

The first major elastomer that could be processed without vulcanization was the urethanes. The TP polyurethanes (PURs) do not have quite the heat resistance and compression-set resistance of the TS PURs, but most of their other properties are the same. The abrasion resistance among the elastomers is outstanding, their low-temperature flex is good, PURs oil resistance is excellent at 82°C (180°F), and their load-bearing capability ranks them with the best of all the elastomers. Additives can improve their dimensional stability or heat resistance, reduce friction, or increase their flame retardancy, fungus resistance, or weatherability. 

Another approach for toughening UP and VE resins which has had success with epoxy resins is the use of liquid rubber (or elastomer) additives. The chief benefit of emplojdng liquid rubbers (LR) versus a flexibilized resin is that decreases in hardness, stiffness and heat-deflection properties can be minimized. During cure, the liquid rubber phase separates from the resin and is concentrated in a particulate phase. Very little of the rubber remains in solution with the cured resin so the resin s heat deflection temperature is for the most part unaffected. The toughness of the two-phase, or composite, material will be a function of the microstructure, which in turn will depend on processing and cure conditions. The subject of epoxy resin toughening is covered in separate articles in this book. 

Provorov et al. [520] have studied a rather extensive group of elastomer additives (accelerators, stabilisers, softeners, fillers, and other ingredients) for possible analysis by fluorescence techniques. No fluorescence lifetime measurements have been applied for discriminating stabilisers in polymers. UV microscopy is another means of measuring the concentration (and distribution) of UV absorbing or fluorescent additives in plastics (cfr. Chp. 5.3.2). 

No discussion of self-bonding elastomers and their possible adhesion mechanisms would be complete without reference to the most widely used system in this category. This is the approach of elastomer additives comprised of silica, resorcinol and formaldehyde donor (or "SRB if hexamethylene tetramine is the formaldehyde carrier). In many practical cases, such additives are able to promote enough adhesion to textile fibers or even metal substrates that use of a primer or tie-coat proper can be obviated. 

Pigment dispersions, thermoplastic elastomer additives, thickeners additive concentrates... 

An excellent text edited by Turi [47] describes the instrumentation and theory of thermal analysis and its application to thermoplastics, copolymers, thermosets, elastomers, additives, and fibers. 

Grade Selection Criteria Melt flow characteristics for injection moulding, extrusion and blow moulding. Filler/reinforcement additions, elastomer additions, food contact approvals, electrical properties. ... 

Comments GF = glass fibres, TZ = impact modified, E = elastomer addition, GFK = glass fibres/beads. Data for material in dry condition, nylon absorbs moisture which alters mechanical and physical properties. ... 

Comments GF = glass fibres, FR = flame retardant, E = elastomer addition. ... 

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