Tires, ozonization

Furthermore, it was foxmd that the content of butadiene units in the ozo-nolyzed oligomers decreases witir ozonolyis time, since they are destroyed by tire ozone attack. It is therefore possible to isolate the blocks of styrene units present in the copolymers, and to estimate their chain length by FAB analysis. ... 

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... 

Tires whose sidewalls are made of natural rubber tend to crack and weather rapidly in areas around cities where high levels of ozone and other industrial pollutants are found. Explain. 

Fifteen tire brand-vehicle combinations were collected from Phoenix, AZ Los Angeles, CA Detroit, MI and Hartford, CT. Six different vehicle types and three different tire manufacturers were studied as detailed in Table 34.1. Vehicle-brand combinations are denoted by the vehicle type followed by the letter denoting the specific manufacturer, e.g., SUV/Minivan-A. The geographic locations were chosen based on ambient temperature and ozone level. Both on-road and full-size spare tires were collected ranging in age from two weeks to six years old. In total, over 1500 tires were analyzed in this study. A small number of tires from Miami, FI and Denver, CO were collected to evaluate the effects for road roughness on aging. No significant effect was observed and these tires were not included in the analysis. 

From equation (12) it can be concluded that the required residence time 0 to achieve a certain value of s is inversely proportional to the average concentration of ozone present in tire reactor. The value of the required residence time and therefore the required volume V of the reactor is completely independent of the distribution of ozone over the reactor. This also holds for the conversion of component A and component B. 

Most polystyrene products are not homopolystyrene since the latter is relatively brittle with low impact and solvent resistance (Secs. 3-14b, 6-la). Various combinations of copolymerization and blending are used to improve the properties of polystyrene [Moore, 1989]. Copolymerization of styrene with 1,3-butadiene imparts sufficient flexibility to yield elastomeric products [styrene-1,3-butadiene rubbers (SBR)]. Most SBR rubbers (trade names Buna, GR-S, Philprene) are about 25% styrene-75% 1,3-butadiene copolymer produced by emulsion polymerization some are produced by anionic polymerization. About 2 billion pounds per year are produced in the United States. SBR is similar to natural rubber in tensile strength, has somewhat better ozone resistance and weatherability but has poorer resilience and greater heat buildup. SBR can be blended with oil (referred to as oil-extended SBR) to lower raw material costs without excessive loss of physical properties. SBR is also blended with other polymers to combine properties. The major use for SBR is in tires. Other uses include belting, hose, molded and extruded goods, flooring, shoe soles, coated fabrics, and electrical insulation. 

This three-component copolymer (terpolymer) (EPDM) contains about 15 double bonds per 1000 carbon atoms in the polymer. This provides enough reactive sites for low-density cross-linking, but unlike Hevea rubber (polyi-soprene), which contains about 200 double bonds per 1000 carbon atoms, EPDM is resistant to ozone. EPDM is used for the sidewalls of tires and for rubber hose but develops too much heat during flexing to be used for heavy-duty tire treads. 

These factors have led researchers to examine novel methods for tire degradation of these contaminants, including liquid-phase photocatalytic oxidation. The treatment of wastewaters contaminated with agents like chlorinated aromatics has also prompted research into the optimum methods of integrating chemical oxidation techniques with existing water treatment methods, particularly biological treatment and ozonation techniques [37],... 

DOPDA h as been used as an addidve to rubber.composidons at the time of manufacture for the purpose of providing ozone resistance to elastometers. Mixtures of DOPDA with solvents such as acetone (usually in 50/50 ratio) are flammable and toxic, causing skin irritation. The material covered by US Military Specification MIL-D-50000A(MR), July 1966 is intended for use as an externally applied (brush or dip) solution to rubber items, particularly tires. This chemical functions as an antiozonant, preventing cracking of stressed, vulcanized rubber items in outdoor storage Requirements and tests covered by the above Spec are as follows ... 

Ozone is a pungent pollutant. It causes eye irritation and at high levels can be lethal. Plant life suffers when exposed to even relatively low concentrations of ozone, and it causes rubber to harden and turn brittle. To protect tires from ozone, manufacturers have incorporated paraffin wax, which reacts preferentially with the ozone, sparing the rubber. As we ll see in Section 17-4, ozone is also formed by natural processes in Earth s stratosphere, where it filters out as much as 95 percent of the sun s ultraviolet rays. So, at Earth s surface, ozone is a harmful pollutant, while 25 kilometers straight up it serves as a sunscreen and is vital for the good health of all living organisms. 

Kargin, Usmanov, and Aikhodzhaev (64) used a similar technique of ozonization to introduce hydroperoxide groups into cellulose substrates. They observed grafting of styrene to ozonized viscose tire cord even without the presence of any other initiating system imparting improved rubber-adhesion to the rayon tire cord. In a later report, Usmanov, Aikhodzhaev, and Azizov (65) described the grafting of acrylonitrile, methyl methacrylate, methylvinylpyridine, and of vinylacetate onto ozonized cellulose. 

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