Rubber compound characteristics

Modifiers of group (b) have a more pronounced influence on fluorosiloxane rubber compound characteristics (Table 4). Optimal content of each modifier is individual and varies from 3.5% for modifier VI up to 7% for modifier VIII. Thus, in the presence of modifier VI, increase of strength to 9.4 MPa (instead 6.4 MPa for the control specimen) may be achieved, and Shore hardness is increased to 60. 

Positive SIMS spectra obtained from plasma polymerized acetylene films on polished steel substrates after reaction with the model rubber compound for times between zero and 65 min are shown in Fig. 44. The positive spectrum obtained after zero reaction time was characteristic of an as-deposited film of plasma polymerized acetylene. However, as reaction time increased, new peaks appeared in the positive SIMS spectrum, including m/z = 59, 64, and 182. The peaks at 59 and 64 were attributed to Co+ and Zn, respectively, while the peak at 182 was assigned to NH,J(C6Hn)2, a fragment from the DCBS accelerator. The peak at 59 was much stronger than that at 64 for a reaction time of 15 min. However,... 

Where resorcinol adhesives are not suitable, resins can be prepared from modified resorcinol [128], Characteristic of these types of resins arc those used for tyre cord adhesives, in which a pure resorcinol-formaldehyde resin is used, or alternatively, alkyl resorcinol or oil-soluble resins suitable for rubber compounding are obtained by prereaction of resorcinol with fatty acids in the presence of sulfuric acid at high temperature followed by reaction with formaldehyde. Worldwide more than 90% of resorcinol adhesives are used as cold-setting wood adhesives. The other most notable application is as tyre cord adhesives, which constitutes less than 5% of the total use. 

Addition of scrap rubber in the form of either ground waste vulcanizates or reclaim in rubber compounds gives economic as well as processing advantages. In addition to lowering the cost of rubber compounds, the use of cross-linked rubber particles has beneficial effects such as faster extrusion rate, reduced die swell, and better molding characteristics. 

Ishiaku, U.S., Chong, C.S., and Ismail, H., Cure characteristics and vulcanizate properties of blends of a rubber compound and its recycled DE-VULC, Polym. Polym. Comp., 6, 399, 1998. 

Differential Thermal Analysis (DTA). One of the characteristics of a rubber useful in tire rubber compounds is that it is amorphous at room temperature but readily undergoes strain induced crystallization. For this reason, copolymers were prepared in order to appropriately adjust the crystalline melt temperature. 

An apparatus for determining the curing characteristics of rubber compounds. 

The feed characteristics of cold rubber compounds differ considerably from those of hot compound to the extruder and a number of devices were developed to overcome this problem. However, the productivity of the early machines was not as high as for the hot-feed machines. 

Compression of the rubber compound as it travels up the barrel is developed in the extruder by either decreasing the thread pitch but maintaining a constant root diameter, or alternatively by increasing root diameter whilst maintaining constant thread pitch. Each of these situations increases the pressure as the rubber compound travels up the barrel. The last portion of the screw prior to the die entry, however, is maintained at a constant pitch or root diameter to enable stock to stabilise in characteristics just prior to entering the die head, to ensure uniformity for extrusion through the die. Conventional extruder screws achieve a compression ratio of 2.5 1. 

These complex systems demand strict screw speed control for all the individual machines in the setup, to balance the extrusion characteristics of the different rubber compounds forming the multiunit component. 

Carbon black Finely divided carbon made by incomplete combustion or decomposition of natural gas or petroleum-based oils in different types of equipment. According to the process and raw material used, it can be furnace (e.g., HAF), thermal (e.g., MT), or channel carbon black (e.g., EPC), each having different characteristics, such as particle size, structure, and morphology. The addition of different types of carbon blacks to rubber compounds results in different processing behavior and vulcanizate properties. 

Methylphenyldimethoxysilane is used as a stabiliser (antistructuring additive) in the production of rubber compounds based on silicone elastomers and highly active fillers. Introducing up to 10% (weight) of methylphenyldimethoxysilane into a rubber mixture improves the physicochemical properties of vulcanised rubbers and helps to preserve the technological characteristics of the compounds in storage. 

Molar mass strongly influences the performance of raw (unvulcanized) rubbers during the preparation of rubber compounds, e.g. addition of fillers and other ingredients. Also the processing characteristics of the compounded rubbers as well as the physical properties of the vulcanized rubbers significantly depend on the molar mass of the unvulcanized rubbers. In order to better meet various requirements, there is not only one BR grade available but... 

The elastomer determines most of the physical and chemical characteristics of a rubber compound. Typical elastomers are natural elastomers such as natural rubber (NR), sometimes called crepe, and synthetic elastomers such as butyl (including chlorobutyl and bromobutyl), ethylene propylene diene monomer (EPDM), and styrene butadiene rubber (SBR). A list of commonly used elastomers is shown in Table 2. 

The effect of synthesized modifiers on fluorosiloxane rubbers is determined on the basis of fluorosiloxane rubber CKTFT-100 As seen fix)m data presented in Table 3, characteristics of fluorosiloxane rubber depend on quantity of introduced modifier and its molecular mass Properties of rubber compounds are highly dependent on modifier concentrations. Optimal modifier content amounts to 6 - 7%. Increase in molecular mass of modifier on transition from modifier II to modifier VI leads to increase in tear strength and relative elongation in comparison to the control specimen (modifier concentration = 0). Also, after thermal treatment at 250 °C for 24 h in the presence of modifier VI, improvement of all fluorosiloxane rubber compound properties is observed. 

Covers two vocedures for determining the compression-de-flection characteristics of rubber compounds other than those usually classified as hard rubber or sponge rubber. 

Polymers, as well as elastomers, are reinforced by the addition of small filler particles. The performance of rubber compounds (e.g. strength, wear resistance, energy loss, and resilience) can be improved by loading the rubber with particulate fillers. Among the important characteristics of the fillers, several aspects can be successfully interrogated by AFM approaches. For instance, the particle and aggregate size, the morphology, and in some cases the surface characteristics of the filler can be assessed. 

For many decades carbon black has enjoyed a practical monopoly as a filler in the tire industry. It retains this position today, the tire industiy consumes 70% of carbon black production. A major breakthrough for non-black fillers came in the early 1970s when a winter tire containing silica in its treading compound was introduced. This resulted in numerous problems with rubber compound processing. The tire compound had different flow and molding characteristics. The development initiated friendly competition (friendly because the major producers of carbon black are also major manufacturers of precipitated silica) which continues to bring improvements to tire performance. 

Many moulded components are affixed on the rubber-lined surface such as anode sleeves in mercury cells used in caustic soda industry. These moulded components are either made from natural soft or ebonite rubbers or Neoprene rubber compounds. While moulding, the flow characteristics of the rubber compound and shrinkage need to be taken into consideration. Some aspects of mould designs are described next. 

From previous accelerated and real time ageing studies, it is known that rubber compounds exhibit complex property changes over time (1,2). Oftentimes, this can lead to less than desirable characteristics in the rubber, such as increased stiffness, embrittlement, poor abrasion characteristics, and others. In thin latex rubber products, it is common practice to under cure the rubber. As the product ages, certain properties will tend to improve for a while before starting a decline. For example, latex rubber condoms are stored in hermetically sealed packages, which limit exposure to oxygen, ozone and UV therefore, their ageing characteristics are more predictable and less pronounced than tires or footwear outsoles, since they can establish a three to five year shelf-life (3). 

It is hypothesized that improved ageing characteristics of rubber compounds could be facilitated by reducing the amount of sulfur and/or under curing the... 

Carbon black finds its way into many products inks, paints, paper, fertilizer, plastics, and explosives to name a few. By far the major use, however, is in automotive tires which consume 65% of the total production. The present day tire contains roughly 1 pound of carbon black for each 2 pounds of rubber and provides both the bounce and wear characteristics desired by the user. The properties carbon black imparts to rubber compounds are so critical that there are currently more than 20 classified grades of oil blacks. Most distinctions between grades are mainly a function of particle size and structure, although surface chemistry is sometimes a factor for specialty uses. The more important grade designations are illustrated in Table I. Each of those listed are also subdivided according to their structure levels. 

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