Elastomers, additives Antioxidants

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. 

The substituted phenols and cresols constitute about half the total volume of this group. Para-t-butylphenol is produced by the alkylation of phenol with isobutylene. The principal applications for this derivative are in the manufacture of modified phenolic resins for the rubber industry and in surface coatings. BHT is obtained from isobutylene and p-cresol. Technical-grade BHT is an antioxidant for plastics and elastomers, and is a gum inhibitor in gasoline. Food-grade BHT is an antioxidant in edible oils, preserves, and many other foods. 2,6-Di-t-butylphenol is used to produce a wide range of plastics additives, antioxidants, and gasoline additives. 

Chem. Descrip. Tributyl phosphate CAS 126-73-8 EINECS/ELINCS 204-800-2 Uses Plasticizer for CR, CPE, Hypalon elastomers, PVC, PVAc, cellulo-sics, PS, ABS, ink systems lubricant additive antioxidant for cellulo-sics, nylon, polyester, PP, PVC antifoam ink solvent paints/coatinqs additive... 

The test were made aimed for determining a threshold value of content of elastomer in the iPP/EOE mixture, which was subject of the d5mamic vulcanization process, considering the influence of these parameters on variable properties of iPP. A series of tests was made, in which the proportions of PP and elastomer Engage I were changed in the range 15-60%, with continuous addition of the cross-linking system (silane A-172/ dicu-myl peroxide) 3/0.03% in relation to elastomer and antioxidant additive 0.2%. 

The antioxidants used in adhesive formulations are similar to those used in rubber compounding and include materials such as the aromatic amines, substituted phenols, and hy-droquinoes. Elastomer and resin manufacturers typically incorporate antioxidants (0.1-0.3 wt %) in their products for protection during storage and shipment. Adhesive formulators will usually add additional antioxidant to protect the adhesive during processing and use. It is not unusual for an adhesive formulation to contain as many as three or four different types of antioxidants. 

Organophosphoms compounds, primarily phosphonic acids, are used as sequestrants, scale inhibitors, deflocculants, or ion-control agents in oil wells, cooling-tower waters, and boiler-feed waters. Organophosphates are also used as plasticizers and flame retardants in plastics and elastomers, which accounted for 22% of PCl consumed. Phosphites, in conjunction with Hquid mixed metals, such as calcium—zinc and barium—cadmium heat stabilizers, function as antioxidants and stabilizer adjutants. In 1992, such phosphoms-based chemicals amounted to slightly more than 6% of all such plastic additives and represented 8500 t of phosphoms. Because PVC production is expected to increase, the use of phosphoms additive should increase 3% aimually through 1999. 

Silicone Heat-Cured Rubber. Sihcone elastomers are made by vulcanising high molecular weight (>5 x 10 mol wt) linear polydimethylsiloxane polymer, often called gum. Fillers are used in these formulations to increase strength through reinforcement. Extending fillers and various additives, eg, antioxidants, adhesion promoters, and pigments, can be used to obtain certain properties (59,357,364). 

However, binding the antioxidant chemically to the elastomer chain by copolymeri2ation or grafting is a better solution to this problem. The addition of /V-(4-ani1ino-pheny1)methacrylamide [22325-96-8] (38) to a polymeri2ation recipe for NBR mbber produces a polymer with a built-in antioxidant resistant to extraction (23). 

AGE-Gontaining Elastomers. The manufacturing process for ECH—AGE, ECH—EO—AGE, ECH—PO—AGE, and PO—AGE is similar to that described for the ECH and ECH—EO elastomers. Solution polymerization is carried out in aromatic solvents. Slurry systems have been reported for PO—AGE (39,40). When monomer reactivity ratios are compared, AGE (and PO) are approximately 1.5 times more reactive than ECH. Since ECH is slightly less reactive than PO and AGE and considerably less reactive than EO, background monomer concentration must be controlled in ECH—AGE, ECH—EO—AGE, and ECH—PO—AGE synthesis in order to obtain a uniform product of the desired monomer composition. This is not necessary for the PO—AGE elastomer, as a copolymer of the same composition as the monomer charge is produced. AGE content of all these polymers is fairly low, less than 10%. Methods of molecular weight control, antioxidant addition, and product work-up are similar to those used for the ECH polymers described. 

Complete inhibition of oxidation is seldom obtained in elastomers by addition of antioxidants or stabilizers. What is usually observed is an extended period of retarded oxidation in the presence of... 

In the rubber field it is not only the polymer that determines the properties of an elastomer, but many accompanying substances, like fillers, pigments, plasticisers, curing agents, antioxidants, stabilisers and processing aids (cf. Table 2.2). With rubbers the possible compositional permutations are numerous. In fact, already within the additive group of CBs there are more than 30 different possible products. 

It is of interest to examine the development of the analytical toolbox for rubber deformulation over the last two decades and the role of emerging technologies (Table 2.9). Bayer technology (1981) for the qualitative and quantitative analysis of rubbers and elastomers consisted of a multitechnique approach comprising extraction (Soxhlet, DIN 53 553), wet chemistry (colour reactions, photometry), electrochemistry (polarography, conductometry), various forms of chromatography (PC, GC, off-line PyGC, TLC), spectroscopy (UV, IR, off-line PylR), and microscopy (OM, SEM, TEM, fluorescence) [10]. Reported applications concerned the identification of plasticisers, fatty acids, stabilisers, antioxidants, vulcanisation accelerators, free/total/bound sulfur, minerals and CB. Monsanto (1983) used direct-probe MS for in situ quantitative analysis of additives and rubber and made use of 31P NMR [69]. 

Saturated hydrocarbons (waxes), fatty acids, metal soaps, fatty acid amides and esters (primarily Cig-Cis) act as internal lubricants, fluoro elastomers as external lubricants. Many other polymer additives, e.g. antistatic agents, antifogs, antioxidants, UV stabilisers, etc., act as lubricants in the barrel of the extruder once they are in the liquid form. 

The styrenic thermoplastic elastomers are the only type which are fully compounded in the manner of conventional elastomers. In this case, however, the addition of carbon black, or other fillers, does not give reinforcement. Additions of polystyrene, or high impact polystyrene, and oil are used to vary hardness and tear strength, and fillers can be used to cheapen the material. Other added polymers, e g., EVA, can be used to increase ozone resistance. These materials also require antioxidants for protection during processing and service life, and the poor UV stability restricts their use in outdoor applications. 

The information on physical properties of radiation cross-linking of polybutadiene rubber and butadiene copolymers was obtained in a fashion similar to that for NR, namely, by stress-strain measurements. From Table 5.6, it is evident that the dose required for a full cure of these elastomers is lower than that for natural rubber. The addition of prorads allows further reduction of the cure dose with the actual value depending on the microstructure and macrostructure of the polymer and also on the type and concentration of the compounding ingredients, such as oils, processing aids, and antioxidants in the compound. For example, solution-polymerized polybutadiene rubber usually requires lower doses than emulsion-polymerized rubber because it contains smaller amount of impurities than the latter. Since the yield of scission G(S) is relatively small, particularly when oxygen is excluded, tensile... 

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