Resistance ozone

Ozone gas is regarded as a main causative substance that promotes the phenomenon of discoloration of inkjet recorded images (27). As this phenomenon of discoloration or fading is characteristic of inkjet images, the improvement of ozone gas fastness is an important technical challenge. 

In particular, a porous white inorganic substance is provided for use for many of the ink receiving layers on the surface of inkjet professional paper to obtain photo quality, in order for the ink to dry the ink more quickly and bleed less for high image quality. 

Ozone resistance improving agents are compounds which have a function to suppress the oxidation of a dye (28). Examples of 

NR/EPDM blends were extensively analyzed for its ozone resistance property (70). The blend ratios of NR/EPDM used in this study were 100/0, 80/20,70/30,60/40, and 0/100. To improve the NR/EPDM blends for ozone resistance, the amount of EPDM 

and 4 are 70/30 NR/EPDM blends with TOR content of 0, 5, 10, and 20 phr, respectively. [From Reference 27 with permission from John Wiley Sons.] 

Ozone is found in the atmosphere, especially around electrical appliances such as motors. Empirically, it has been found that exposure to 3 ppm ozone under 25% strain gives a good indication of ozone resistance. At this level the material does not crack after 500 hours of exposure. If the level is increased to 100 ppm, some cracking is observed after 45 hours, and the sample breaks after 460 hours. 

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

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. 

The prime installation method is mechanically fastened but fully adhered and ballasted appHcations can also be used. CSPE exhibits strong resistance not only to weathering but also to a broad range of chemicals and pollutants it is also inherently ozone-resistant. It can be produced in many colors and the sheet widths are typically 5—6.5 ft (1.5—1.65 m). The physical characteristics of a CSPE sheet have been described (17) (see Elastomers, SYNTHETIC-Cm OROSULFONATED POLYETHYLENE). 

Physical Factors. Unsatuiated elastomers must be stretched for ozone cracking to occur. Elongations of 3—5% are generally sufficient. Crack growth studies (10—18) have shown that some minimum force, called the critical stress, rather than a minimum elongation is required for cracking to occur. Critical stress values are neady the same for most unsaturated mbbers. However, polychloroprene has a higher critical stress value than other diene mbbers, consistent with its better ozone resistance. It has been found that temperature, plasticization, and ozone concentration have httie effect on critical stress values. 

Ozonc-rcsjstant elastomers which have no unsaturation are an exceUent choice when their physical properties suit the appHcation, for example, polyacrylates, polysulfides, siHcones, polyesters, and chlorosulfonated polyethylene (38). Such polymers are also used where high ozone concentrations are encountered. Elastomers with pendant, but not backbone, unsaturation are likewise ozone-resistant. Elastomers of this type are the ethylene—propylene—diene (EPDM) mbbers, which possess a weathering resistance that is not dependent on environmentally sensitive stabilizers. Other elastomers, such as butyl mbber (HR) with low double-bond content, are fairly resistant to ozone. As unsaturation increases, ozone resistance decreases. Chloroprene mbber (CR) is also quite ozone-resistant. 

Blends of diene and backbone-saturated mbbers are frequently used in appHcations where discoloration by chemical antiozonants caimot be tolerated, yet where cost is stiH a primary consideration (eg, white sidewalls of tires). Disadvantages are that physical properties have to be compromised and the two mbbers usually differ greatly in their rates of vulcanization. Usually, at least a 25% replacement by the ozone-resistant mbber is needed for an appreciable enhancement in ozone protection (6). 

The first use for butyl mbber was ia inner tubes, the air-retention characteristics of which contributed significantly to the safety and convenience of tires. Good weathefing, ozone resistance, and oxidative stabiUty have led to appHcations ia mechanical goods and elastomeric sheeting. Automobile tires were manufactured for a brief period from butyl mbber, but poor abrasion resistance restricted this development at the time. 

Blends of halogenated butyl mbber are used in tire sidewalls and tread compounds (97). In sidewalls, ozone resistance, crack cut growth, and... 

The resistance to heat and aging of optimized EPM/EPDM vulcanizates is better than that of SBR and NR. Peroxide-cured EPM can, for instance, be exposed for 1000 h at 150°C without significant hardening. Particularly noteworthy is the ozone resistance of EPM/EPDM vulcanizates. Even after exposure for many months to ozone-rich air of 100 pphm, the vulcanizates will not be seriously harmed. EPM/EPDM vulcanizates have an excellent resistance to chemicals, such as dilute acids, alkaUes, alcohol, etc. This is in contrast to the resistance to aUphatic, aromatic, or chlorinated hydrocarbons. EPM/EPDM vulcanizates swell considerably in these nonpolar media. 

Blends with PVC. Nitrile mbber may be blended with poly(vinyl chloride) (PVC) by the polymer producer by two different techniques (1) blending of NBR latex with PVC latex followed by co-coagulation and drying, or (2) physically mixing the soHd NBR and PVC powder in mixing equipment such as an internal mixer. NBR—PVC polymer blends are well known for the good ozone resistance that is imparted by the PVC. 

Two propylene oxide elastomers have been commercialized, PO—AGE and ECH—PO—AGE. These polymers show excellent low temperature flexibihty and low gas permeabihty. After compounding, PO—AGE copolymer is highly resiUent, and shows excellent flex life and flexibiUty at extremely low temperatures (ca —65°C). It is slightly better than natural mbber in these characteristics. Resistance to oil, fuels, and solvents is moderate to poor. Wear resistance is also poor. Unlike natural mbber, PO—AGE is ozone resistant and resistant to aging at high temperatures. The properties of compounded ECH—PO—AGE he somewhere between those of ECH—EO copolymer and PO—AGE copolymer (22). As the ECH content of the terpolymer increases, fuel resistance increases while low temperature flexibihty decreases. Heat resistance is similar to ECH—EO fuel resistance is similar to polychloroprene. The uncured mbber is soluble in aromatic solvents and ketones. 

Some of the terpolymers containing high levels of AGE give superior sour gasoline and ozone resistance, particularly dynamic ozone resistance. Since the unsaturation is not in the polymer backbone, it can be, and apparentiy is, sacrificed under sour gasoline or ozone aging. This protection scheme is limited with the peroxide and sulfur cure systems as they involve the aHyl functionaUty of the polymer. The protection is maximized when a dinucleophilic curative, such as trithiocyanurate, is used. 

The level of unsaturation is much lower, giving rubbers of much better heat, oxygen and ozone resistance. 

At one time it was widely expected that EPDM rubbers would become of significance in the tyre sector. For a variety of reasons but primarily because of the high cost of the diene monomers this expectation has not been realised. On the other hand these rubbers have become widely accepted as moderately heat-resisting materials with good weathering, oxygen and ozone resistance and they find extensive use in cars, domestic and industrial equipment. 

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. 

In 1980 the Goodyear company announced copolymers of cyclopentadiene, cyclo-octene or cyclo-octa-1,5-diene with the Diels-Alder addition product of hexachlorocyclopentadiene and cyclo-octa-1,5-diene. This material has been proposed as an alternative to the polychloroprenes, with lower ( 5°C), and superior ozone resistance... 

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. 

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. 

Ozone attack of rubbers can be prevented in three ways (1) coating the surface (2) adding a chemical antioxidant (3) relieving internal stresses by adding ozone-resistant polymers. 

One-step vulcanization, wide range of curing conditions, high loading elasticity, snappiness, no deformation, weatherability. ozone resistance, heat resistance, tear resistance, coating performance, adhesive properties, skid resistance, abrasion resistance... 

Heat, hot oil, wear, and ozone resistance Hot oil, heat, and ozone resistance... 

Kennedy, J. P. and Chou,T. Poly (isobutylene-co-fS-Pinene) A New Sulfur Vulcanizable, Ozone Resistant Elastomer by Cationic Isomerization Copolymerization. Vol. 21, pp. 1—39. 

D 2770 Ozone-Resist Ethylene-Propylene Rubber Integral Insulation Jacket for Wire Cable. 

D 2802 Ozone-Resistant Ethylene-Propylene Rubber Insulation for Wire Cable. 

Natural rubber Solid Good physical properties and resistance to cutting and abrasion. Low heat and ozone resistance. Gaskets. 

Chlorinated polyethylene CPEs provide a very wide range of properties from soft/ elastomeric to hard. They have inherent oxygen and ozone resistance, have improved resistance (compared to PEs) to chemical extraction, resist plasticizers, volatility, and weathering. Products do not fog at high temperatures as do PVCs and can be made flame retardant. 

Ozone Resistant Elastomer by Cationic Isomerization Copolymerization. Vol. 21, pp. 1-39. 

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