Ozone rubber


Ozone Rubber and elastomers Cracking, weakening  [c.501]

It is a very lightweight rubber and has very good weathering and electrical properties, excellent adhesion, and excellent ozone resistance.  [c.1064]

Ozone ALkenes, aromatic compounds, bromine, diethyl ether, ethylene, HBr, HI, nitric oxide, nitrogen dioxide, rubber, stibine  [c.1210]

Nitrile mbber finds broad application in industry because of its excellent resistance to oil and chemicals, its good flexibility at low temperatures, high abrasion and heat resistance (up to 120°C), and good mechanical properties. Nitrile mbber consists of butadiene—acrylonitrile copolymers with an acrylonitrile content ranging from 15 to 45% (see Elastomers, SYNTHETIC, NITRILE RUBBER). In addition to the traditional applications of nitrile mbber for hoses, gaskets, seals, and oil well equipment, new applications have emerged with the development of nitrile mbber blends with poly(vinyl chloride) (PVC). These blends combine the chemical resistance and low temperature flexibility characteristics of nitrile mbber with the stability and ozone resistance of PVC. This has greatly expanded the use of nitrile mbber in outdoor applications for hoses, belts, and cable jackets, where ozone resistance is necessary.  [c.186]

Rubber chemicals are materials that are added ia minor amounts to mbber formulations in order to improve their properties and make them commercially useful. Raw mbber polymer has very limited practical appHcations because of tackiness, flow, and other undesirable features. Rubber chemicals are added to assist processing, promote cross-linking, and provide longevity to the part in service. Vulcanising adjacent polymer chains together by cross-links prevents flow, increases strength, and provides recovery from deformation. The most widely used method of cross-linking polymer chains is by heating with elemental sulfur (vulcanisation). Accelerators speed up the reaction of sulfur with polymer to improve the economics of manufacture and prevent degradation that would otherwise occur upon prolonged heating. Peptizers and process aids assist flow during the mixing and shaping operations. Antidegradants protect the part in service from heat, oxygen, ozone, and repeated flexing. Other mbber chemicals function as blowing agents, adhesion promoters, and activators or retarders which modify the onset of cross-linking.  [c.219]

Rubber and Synthetic Elastomers. For many years nondecorative coated fabrics consisted of natural mbber on cotton cloth. Natural mbber is possibly the best all-purpose mbber but some characteristics, such as poor resistance to oxygen and ozone attack, reversion and poor weathering, and low oil and heat resistance, limit its use to special appHcation areas (see Elastomers, synthetic Rubber, natural).  [c.296]

Production of chlorosulfonated polyethylene products on a worldwide basis is estimated to be approximately 50,000 t/yr. The Du Pont Co. is the primary manufacturer with one plant in the United States having a capacity of about 33,000 t and one plant in Northern Ireland with about 13,000 t capacity. The remaining world capacity is provided by Toyo Soda Manufacturing Ltd. in Japan. The Du Pont Co. manufactures all CSM types under the trade names of Hypalon and Acsium Synthetic Rubber at each of its plant sites. Toyo Soda makes closely related products under the trade name CSM-CP, or Ts. Since the precursor material is primarily ethylene, materials costs are related to petroleum prices. Costs of environmental control procedures surrounding the use of carbon tetrachloride solvent have escalated extensively because it was placed on the Montreal Protocol of potential ozone depleting agents in 1989. Because carbon tetrachloride is to be completely phased out by the year 1996, significant investment in new equipment designed to handle replacement solvents is anticipated. General-purpose grades of CSM, ie, Hypalon 40, have a selling price of 2.80—3.00/kg whereas special grades, ie, Acsium, sell for about 7.70/kg. Average selling prices of all CSM grades is about 3.50/kg.  [c.496]

Corrosion. A more serious effect and one of great economic-importance is the corrosive action of acid gases on building materials. Such acids can cause stone surfaces to blister and peel mortar can be reduced to powder. Metals are also damaged by the corrosive ac tion of some pollutants. Another common effect is the deterioration of tires and other rubber goods. Cracking and apparent drying occur when these goods are exposed to ozone and other oxidants.  [c.2178]

All parts up to the ozonizer may be connected with heavy rubber tubing. It is desirable to place this purification train  [c.64]

Rubber products may be protected against ozone attack by the use of a highly saturated rubber molecule, the use of a wax inhibitor which will "bloom" to the surface, and the use of paper or plastic wrappings to protect the surface. Despite these efforts, rubber products still crack more on the West Coast than on the East Coast of the United States.  [c.133]

Describe why some types of synthetic rubber are less susceptible to ozone attack than natural rubber.  [c.135]

For any pollutant, air quality criteria may refer to different types of effects. For example. Tables 22-1 through 22-6 list effects on humans, animals, vegetation, materials, and the atmosphere caused by various exposures to sulfur dioxide, particulate matter, nitrogen dioxide, carbon monoxide, ozone, and lead. These data are from fhe Air Quality Criteria for these pollutants published by the U.S. Environmental Protection Agency.  [c.367]

This situation is identical to the previous one and occurs for example when paraffin wax is mixed into rubber above the melting point of the wax. On cooling, the wax starts to crystallise, some of it forming a bloom on the rubber surface. Such a bloom assists in protecting a diene rubber from ozone attack.  [c.85]

When diene rubbers are exposed to ozone under stressed conditions cracks develop which are perpendicular to the direction of stress. Whilst ozone must react with unstressed rubber no cracking occurs in such circumstances nor when such rubber is subsequently stressed after removal of the ozone environment. For many years such rubbers were protected by waxes which bloomed on to the surface of the rubber to form an impermeable film. This was satisfactory for static applications but where the rubber was operating under dynamic conditions the wax layer became broken and hence less effective.  [c.143]

Polybutadiene, polyisoprene (both natural and synthetic), SBR and poly-(dimethyl butadiene) (used briefly during the First World War as methyl rubber) being hydrocarbons have limited resistance to hydrocarbon liquids dissolving in the unvulcanised state and swelling extensively when vulcanised. Being unsaturated polymers they are susceptible to attack by such agencies as oxygen, ozone, halogens and hydrohalides. The point of attack is not necessarily at the double bond but may be at the a-methylenic position. The presence of the double bond is nevertheless generally crucial. In addition the activity of these agencies is affected by the nature of the groups attached to the double bond. Thus the methyl group present in the natural rubber molecule and in synthetic polyisoprene increases activity whereas the chlorine atom in polychloroprene reduces it.  [c.282]

Like NR, SBR is an unsaturated hydrocarbon polymer. Hence unvulcanised compounds will dissolve in most hydrocarbon solvents and other liquids of similar solubility parameter, whilst vulcanised stocks will swell extensively. Both materials will also undergo many olefinic-type reactions such as oxidation, ozone attack, halogenation, hydrohalogenation and so on, although the activity and detailed reactions differ because of the presence of the adjacent methyl group to the double bond in the natural rubber molecule. Both rubbers may be reinforced by carbon black and neither can be classed as heat-resisting rubbers.  [c.292]

The close structural similarities between polychloroprene and the natural rubber molecule will be noted. However, whilst the methyl group activates the double bond in the polyisoprene molecule the chlorine atom has the opposite effect in polychloroprene. Thus the polymer is less liable to oxygen and ozone attack. At the same time the a-methylene groups are also deactivated so that accelerated sulphur vulcanisation is not a feasible proposition and alternative curing systems, often involving the pendant vinyl groups arising from 1,2-polymerisation modes, are necessary.  [c.295]

More recently, in 1975, Du Pont introduced a terpolymer (Vamac) based on ethylene, methyl acrylate and a third monomer of undisclosed composition which contained a carboxylic acid group to provide a cure site for use with peroxides or amines. Both types of rubber exhibit good heat, oxygen and ozone resistance.  [c.301]

As with c -polyisoprene, the gutta molecule may be hydrogenated, hydro-chlorinated and vulcanised with sulphur. Ozone will cause rapid degradation. It is also seriously affected by both air (oxygen) and light and is therefore stored under water. Antioxidants such as those used in natural rubber retard oxidative deterioration. If the material is subjected to heat and mechanical working when dry, there is additional deterioration so that it is important to maintain a minimum moisture content of 1%. (It is not usual to vulcanise the polymer.)  [c.866]

With rubber base adhesives, it is necessary to prevent their properties from changing during service life. Oxidative changes induced by thermal, ozone exposure and UV light can dramatically affect service life of rubber base adhesives. More precisely, the rubber and the resin are quite susceptible to oxidative degradation. Environmental and physical factors exert detrimental effects on rubber base adhesive performance. These effects can be mitigated by the incorporation of low levels of stabilizers during the fabrication process of the adhesive.  [c.640]

Ozone cracking is a physicochemical phenomenon. Ozone attack on olefinic double bonds causes chain scission and the formation of decomposition products. The first step in the reaction is the formation of a relatively unstable primary ozonide, which cleaves to an aldehyde or ketone and a carbonyl. Subsequent recombination of the aldehyde and the carbonyl groups produces a second ozonide [58]. Cross-linking products may also be formed, especially with rubbers containing disubstituted carbon-carbon double bonds (e.g. butyl rubber, styrene-butadiene rubber), due to the attack of the carbonyl groups (produced by cleavage of primary ozonides) on the rubber carbon-carbon double bonds.  [c.645]

Rubbers differ in their resistance to ozone. All the highly unsaturated rubbers (natural rubber, styrene-butadiene rubber, butyl rubber, nitrile rubber) are readily cracked while the deactivated double carbon-carbon bonds rubber (such as polychloroprene rubber) shows moderate ozone resistance.  [c.645]

A physical antiozonant provides an effective barrier against the penetration of ozone on the rubber surface. This barrier should be continuous at the surface, unreactive and impenetrable to ozone, and also capable of renewing itself if damaged.  [c.645]

An antiozonant should have adequate solubility and diffusivity characteristics. Since ozone attack is a surface phenomenon, the antiozonant must migrate to the surface of the rubber to provide protection. Poor solubility in rubber may result in excessive bloom.  [c.645]

Rubber is protected against ozone attack by addition of physical and/or chemical antiozonants. Hydrocarbon waxes are the most common type of physical antiozonants, and p-phenylenediamine derivatives are the prevalent chemical antiozonants. Waxes bloom to the rubber surface and form a protective barrier.  [c.645]

Natural and Synthetic Rubber. Fluorination of natural or synthetic mbber creates a fluorocarbon coating (29,75,76) which is very smooth and water repeUent (see Water, waterproofing and water/oilrepellency). Rubber articles such as surgical gloves, O-rings, gaskets, and windshield wiper blades can be fluorinated on the surface while the interior retains the elastic, flexible properties of the natural mbber. Fluorinated O-rings can be used without extra lubricant in corrosive atmospheres since the fluorocarbon is unreactive. In food-processing equipment, grease or lubricants are eliminated and do not contaminate the food products. Fluorinated O-rings have smooth surfaces, very low frictional coefficients, and enhanced thermal stabiHties. Fluorinated windshield wiper blades have a very low coefficient of friction, mn smoother with less squeak, their surface is more resistant to the sun s uv radiation and attack by ozone, and they require less electrical energy for operation.  [c.279]

The inoigaiiic chemistiy of ozone is extensive, encompassing virtually every element except most noble metals, fluorine (qv), and the inert gases. Repotted second-order rate constants (L/(mol-s)) at 20—23°C refer to the disappearance of ozone unless otherwise stated.  [c.491]

Thermoplastic Natural Rubber. Thermoplastic elastomers are probably the fastest-growing sector of the polymer market in the 1990s because of their easy processibiUty, efficiency in reuse of scrap or out-of-spec mol dings, and general recycling capabiUty. Natural mbber thermoplastic materials are based on blends of natural mbber and polypropylene (52,53). Basically, there are two types those with a low natural mbber content, which are really only mbber toughened forms of polypropylene, and the softer grades with high natural mbber content, which are truly classed as thermoplastic elastomers. The latter have high strength and good recovery properties, better aging than conventional natural mbber vulcanizates, and excellent ozone resistance. These materials all have to be processed on thermoplastic machinery, and 180°C is regarded as the minimum melt temperature.  [c.271]

Stratospheric Ozone Protection. Tide VI of the 1990 Amendments deals with stratospheric o2oae protectioa. Certaia chloriaated fluorocarboa (CEC) compouads, eg, 1,1,1-trichloroethane and carbon tetrachloride, will be phased out over a scheduled time period. Knowingly venting CECs from household appHances, commercial refrigerators, and air conditioners is prohibited. Siace 1992, repair shops must use certified recycling equipment when servicing motor vehicle air conditioning units. Nonessential CEC-containing consumer products ate to be banned, including plastic party streamers, noise horns, and cleaning fluids for electronic and photographic equipment. Among iadustrial solveat users, the largest impact will be felt ia the area of vapor-phase degreasiag.  [c.263]

Another important class of random copolymers are the ethylene—propylene elastomers. The saturated hydrocarbon backbone provides good ozone resistance and better weathering and aging characteristics than diene mbbers. Even though these materials are synthesized by Ziegler—Natta catalysts, they do not exhibit much stereospecificity. There are basically two types of these copolymers, ethylene—propjiene (EPM) and ethylene—propjiene—diene (EPDM) materials (67). EPM materials are completely saturated if vulcanization is requited, it is carried out by means of free-radical generators (ie, organic peroxides). These copolymers are typically polymerized in an organic solvent or by using the Hquid phase of the monomer itself. Copolymers containing from 40 to 60 mol % of ethylene are most desirable more ethylene leads to crystalline block stmctures. EPDM materials contain 3 to 10 wt % of one of the following nonconjugated dienes ethyHdene norbornene (ENB) 1,4-hexadiene (HD) or dicyclopentadiene (DCPD). Similarly, these random terpolymers are made in a solution process where the solvent is organic or the monomer itself is in the Hquid phase. Suspension processes have also been developed. Because these materials contain unsaturation, they are easily vulcanized with either common mbber accelerators and sulfur or with organic peroxides. Important producers of EP elastomers include Copolymer Rubber and Chemical (EP syn), Du Pont (Nordel), Exxon Chemical (Vistalon), Polysar Inc. (Polysar EPM and EPDM), and Unicoyal (Royalene). The U.S. production of EPM and EPDM in 1990 was 295,000 t (68).  [c.184]

Materials The damage that air pollutants can do to some materials is well known ozone in photochemical smog cracks rubber, weakens fabrics, and fades dyes hydrogen sulfide tarnishes silver smoke dirties laundry acid aerosols ruin nylon hose. Among the most important effects are discoloration, corrosion, the soiling of goods, and impairment of visibility.  [c.2174]

Natural rubber is resistant to dilute mineral acids, alkalies, and salts, but oxidizing media, oils, and most organic solvents will attack it. Hard rubber is made by adding 25 percent or more of siilfur to natural or synthetic rubber and, as such, is both hard and strong. Chloro-prene or neoprene rubber is resistant to attack by ozone, sunhght, oils, gasohne, and aromatic or halogenated solvents but is easily permeated by water, thus limiting its use as a tank hning. Styrene rubber has chemical resistance similar to that of natural. Nitrile rubber is known for resistance to oils and solvents. Butyl rubbers resistance to dilute mineral acids and alkahes is exceptional resistance to concen-  [c.2461]

Does the Toller use a primary ozone depleting compound (ODC, for example, a CFC or 1,1,1, -trichloroethane) m their process Are ODC management practices followed (for example no uncontrolled releases of ODCs, installation of capture and recycle equipment, leak detection and repair, use of well trained personnel)  [c.167]

Vegetation damage can be measured biologically or socioeconomically. Using the latter measure, there is a 0% loss when there is no loss of the sale value of the crops or ornamental plants but a 100% loss if the crop is damaged to the extent that it cannot be sold. These responses are related to dose, i.e., concentration times duration of exposure, as shown by the percent loss curves on the chart. A number of manifestations of material damage, e.g., rubber cracking by ozone, require an exposure duration long enough for the adverse effects to be significant economically. That is, attack for just a few seconds or minutes will not affect the utility of the material for its intended use, but attack for a number of days will.  [c.58]

Although it was known for some time that ozone cracks rubber products under tension, the problem was not related to air pollution. During the early 1940s, it was discovered that rubber tires stored in warehouses in Los Angeles, California, developed serious cracks. Intensified research soon identified the causative agent as ozone that resulted from atmospheric reaction between sunlight (3000-4600 A), oxides of nitrogen, and specific types of organic compounds, i.e., photochemical air pollution.  [c.133]

Natural rubber is composed of polymerized isoprene units. When rubber is under tension, ozone attacks the carbon-carbon double bond, breaking the bond. The broken bond leaves adjacent C = C bonds under additional stress, eventually breaking and placing shll more stress on surrounding C = C bonds. This "domino" effect can be discerned from the structural formulas in Fig. 9-4. The number of cracks and the depth of the cracks in rubber under tension are related to ambient concentrations of ozone.  [c.133]

Since the mid-1950s several materials have been found effective in combating ozone-initiated degradation, in particular certain p-phenylenediamine derivatives. The actual choice of such antiozonants depends on the type of polymer and on whether or not the polymer is to be subject to dynamic stressing in service. Since antiozonants are not known to have any use in plastics materials, even those which may have certain rubber particles for toughening, they will not be dealt with further here. Anyone interested further should consult references 3-5.  [c.143]

The rubber has a very low of -68°C, excellent hydrolytic stability and excellent resistance to ozone, solvents and acids. In addition the rubber does not bum even in an oxidising atmosphere. Although its properties are virtually unchanged in the range -75 to + 120°C it does not possess the heat resistance of other fluoroelastomers. This polymer was marketed by Firestone in the mid-1970s as PNF rubber, but in 1983 the Ethyl Corporation obtained exclusive rights to the Firestone patents and the polymer is now marketed as Eypel F.  [c.383]

Vulcanisation can be effected by diamines, polyamines and lead compounds such as lead oxides and basic lead phosphite. The homopolymer vulcanisate is similar to butyl rubber in such characteristics as low air permeability, low resilience, excellent ozone resistance, good heat resistance and good weathering resistance. In addition the polyepichlorohydrins have good flame resistance. The copolymers have more resilience and lower brittle points but air impermeability and oil resistance are not so good. The inclusion of allyl glycidyl ether in the polymerisation recipe produces a sulphur-curable elastomer primarily of interest because of its better resistance to sour gas than conventional epichlorhydrin rubbers.  [c.548]

Polyurethane rubbers in general, and the Vulkollan types in particular, possess certain outstanding properties. They can have higher tensile strengths than any other rubber and have excellent tear and abrasion resistance. They tend to have a high hardness and a low resilience and in fact may be regarded as somewhat intermediate between conventional rubbers and flexible thermoplastics. The urethane rubbers also show outstanding resistance to ozone and oxygen (features lacking with the diene-rubbers) and to aliphatic hydrocarbons. Reversible swelling occurs with aromatic hydrocarbons. One disadvantage of the materials is that hydrolytic decomposition occurs with acids, alkalis and the prolonged action of water and steam.  [c.788]


See pages that mention the term Ozone rubber : [c.73]    [c.891]    [c.494]    [c.715]    [c.387]    [c.64]    [c.66]    [c.340]    [c.295]    [c.880]   
Fundamentals of air pollution (1994) -- [ c.133 ]