Rubber compounding preparation

The rubber compounds prepared in this way are analysed and packed into polyethylene bags. Then they are loaded into metal cylinders or rubberised bags and sent to the consumer. Silicone rubber compounds can be stored for 3 to 6 months depending on the type of fillers and stabilisers. 

To estimate the properties of ozonizated Indian rubber in the rubber compound a sample of 0.4 kg mass was obtained with ozonization degree of 0.8 mass % (sample 6 in Table 13.1). This sample was used for the preparation of the rubber compoimd according to the standard formulation approved in tire production. Rubber compound prepared on the basis of the rubber extracted from the sample of original latex that was preliminarily plasticized with the use of cold rolling mills with the gap of 2 mm for 3 min was applied as the reference sample. The choice of plasticization time was connected with the necessity of decrease of the rubber molecular mass up to the value of that one obtained from the ozonizated latex. 

Fast, low temperature curing mbber compounds can be prepared by initial heat prevulcanisation of the Hquid latex and are marketed commercially (Revultex, Doverstrand Corporation). Rubber deposited from these often needs tittle more heat than that required to dry the deposit, to achieve optimum tensile strength and elongation. Such compounds are often used by small companies manufacturing thin-wall dipped medical latex products, such as examination gloves, as few compound preparation facilities are needed by the dipping company. 

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. 

The production of a rubber lining includes the preparation of the rubber compound followed by processing to form the lining sheet, substrate preparation, lining application, vulcanisation and inspection. All these stages require thorough quality control, especially compound manufacture and sheet preparation, as chemical resistance depends on satisfactory dispersion of the individual ingredients and undetected flaws in the sheet will cause problems in service. 

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. 

The usual agent used for the purpose is calcium oxide (quicklime). In its dry powder form dispersion in the rubber compound is a serious problem. Thus, the chemical is offered in a variety of carrying media to ensure adequate dispersion and, in most cases, to prevent moisture uptake by the calcium oxide after preparation and prior to incorporation in the rubber compound. 

Fumed silica is prepared by burning volatile silicon compounds such as silicon tetrachloride. This type of silica contains less than 2% combined water and generally no free water. It reacts readily with hydroxyl groups. The particle size is in the region 5-10 nm. Fumed silicas are not generally used in conventional rubber compounding but find application with silicone rubber. The recognised surface area values for best reinforcement of silicone rubber by an amorphous silica lies between 150-400 m2/g. 

An alternative method to that of using a spreading machine or a calender for the initial preparation of fabrics for application of rubber (for composite product assembly) can be by the use of dip coaters. Application of rubber compound by this method ensures a better penetration of the fabric interstices than can be achieved by conventional frictioning techniques using calenders. More delicate fabrics which would not be strong enough for calender application can also be treated with rubber by this technique. 

The two-roll mill represents the earliest form of rubber processing machine, used by the rubber manufacturer being developed from the masticator of Hancock. Over the years the emphasis of the role of the two-roll mill has moved from being that of the prime means of compound preparation for the majority of the rubber industry, to that of secondary usage. In the modem factory conventional two-roll mills are used for compound blending and for sheeting off of compound mixed by other means. In addition they are used to warm-up compounds from store, and for a number of blending purposes to achieve compound uniformity for other processes. 

A pre-cured tread with pattern is prepared by moulding. A thin strip of unvulcanised cushion rubber compound is inserted between the casing and the tread rubber to form the bonding agent between the new and old components. The tread is then applied to the casing and consolidated by pressure. The cushion rubber is then vulcanised. This is also known as cold retreading . 

Rubber compounds are colored with powder pigments and increasingly with granulated pigment preparations, known in the rubber industry too as master-batches. 

Polymers. In combination with various metal salts, sorbitol is used as a stabilizer against beat and light in poly(vinyl chloride) (qv) resins and, with a phenolic antioxidant, as a stabilizer in uncured styrene—butadiene mbber (qv) compositions and in polyolefins (see He AT STABILIZERS Olefin polymers Rubber compounding). Heat-sealable films are prepared from a dispersion of sorbitol and starch in water (255). Incorporation of sorbitol in collagen films gready restricts their permeability to carbon dioxide (256). 

Preparation of rubber compounds based on organosiloxane elastomers... 

Silicone elastomer-based rubber compounds are prepared in conventional apparatuses (closed agitators, roll mills, etc.) and consist of the following ingredients elastomer, active fillers, vulcanising agent, stabiliser, pigment additives. 

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... 

Stephens et al.70-72 examined the commercial potential of SX-reinforced rubber. SX reinforced styrene-butadiene and nitrile-butadiene rubber compounds, but displayed no reinforcement of natural rubber. The addition of resorcinol-formaldehyde resin at 8% of the starch weight significantly improved the mechanical properties for all three rubber compounds. The preparation of starch xanthide-rubber compounds by crosslinking the SX with sodium nitrite produced results similar to those obtained by adding resorcinol-formaldehyde resin. 

Starch poly(ethyleniminothiourethanes) prepared by the reaction of SX with poly(ethylenimine) were shown to be suitable reinforcing agents for rubber compounds.79,80 Master batches were prepared using SX with DS values ranging from 0.08 to 0.58 and starch contents of 15 to 50 phr. Best results were obtained at a DS of —0.22 and a loading of 25 phr starch, with a PEI stoichiometric ratio of 3.5. Hardness generally increased with DS and starch content, while compression set and abrasion resistance decreased. 

Carboxylic elastomers have been reinforced with cationic starch products.93 Compounds were prepared either by solution mixing followed by drying, or by using a torque rheometer. The addition of cationic starch significantly reduced the toluene solubility of the carboxylated rubber. Physical properties of these compounds were greater than compounds prepared with unmodified pearl starch. 

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