Vulcanization methods

The scope of compounding includes specifying the type and amount of various ingredients in a mix, evolving the mixing procedure and vulcanization methods and their details accordingly. This basically covers the consideration of the requirements of the end use and the service properties of the products, processibility of the compounds and cost. The three most important factors to be considered in the development of a compound are ... 

Chorvath I et al. (2002) Thermoplastic elastomer compositions containing silicone rubber and nylon resins and the dynamically vulcanizing method. US Patent... 

Their elution data for standard polystyrenes from EPDM packed columns showed clearly the differences presented between two vulcanizing methods one was photo-cross linked and the other was peroxide-cured EPDM. From this study they concluded that the M the molecular weight between cross-linking junctions, was different for the two samples. 

Vulcanization Methods for producing a material with good elastomeric properties (rubber) involves the formation of chemical crosslinks between high-molecular-weight linear molecules. The starting polymer (such as raw rubber) must be of the noncrystallizing type (NR is crystallizable), and its glass transition temperature Tg must be well below room temperature to ensure a rubbery behavior. A -axis The axis in the plane of a material used as 0° reference thus the y-axes is the axes in the plane of the material perpendicular to the x-axis thus the z-axes is the reference axis normal to the x-y plane. The term plane or direction is also used in place of axis. 

Schmitt, S. W. Vulcanizing Methods for Neoprene, Du Pont Publication, NP460.1, p.8. 

There are many ways to measure these properties and some of them are proprietary. However, most laboratory tests are standardized by American Standard Testing Methods (ASTM). Many of them are interactive to various degrees. The rate and state of vulcanization is especially important to consider for components of heavier and thicker tines. The heat used to vulcanize the tine in a mold under pressure requites time to penetrate from both sides of the giant tine to the innermost portions. Securing a balanced state of cure, ie, the maximizing of physical properties in all the components, results in the innermost components having a faster rate of cure. The peripheral compounds should have a cure system which holds its physical properties well when overcured. 

Vulcanization. Vulcanization of articles made from latex compounds generally foUows the same principles and methods as in vulcanizing... 

Mold temperatures vary between 150—200°C, depending on the mol ding methods and part size. Parts can be molded in 1.5—10 min depending on the configuration and thickness of the part, the mold temperature, and the desired state of cure at demolding. Since most ethylene—acryflc parts are postcured, it is sometimes possible to demold partly cured articles and complete vulcanization in the postcuring oven. 

The method of dynamic vulcanization was applied to mixtures of NR with LDPE, PP homopolymer, and PRP... 

Dynamic vulcanization as a method to improve the mechanical properties of NR-PE blends has been discussed in detail by Choudhary et al. [30]. The physical properties of unvulcanized and vulcanized NR-HDPE blends are given in Table 7 where notations A, B, and C indicate 70 30, 50 50, 30 70 NR-HDPE blends, respectively. The subscripts C and D denote blends containing DCP and high abrasion furnace (HAF) black (40 phr), respectively. 

Blend of (1) and (2) type categories mostly include the modification of engineering thermoplastics with another thermoplastic or rubber. PS-EPDM blends using a low-molecular weight compound (catalyst) Lewis acid have been developed [126]. Plastic-plastic blends, alloys of industrial importance, thermoplastic elastomers made by dynamic vulcanization, and rubber-rubber blends are produced by this method. 

It is possible to distinguish between SBR and butyl rubber (BR), NR and isoprene rubber (IR) in a vulcan-izate by enthalpy determination. In plastic-elastomer blends, the existence of high Tg and low Tg components eases the problems of experimental differentiation by different types of thermal methods. For a compatible blend, even though the component polymers have different Tg values, sometimes a single Tg is observed, which may be verified with the help of the following equation ... 

Ionic polymers are a special class of polymeric materials having a hydrocarbon backbone containing pendant acid groups. These are then neutralized partially or fully to form salts. lonomeric TPEs are a class of ionic polymers in which properties of vulcanized rubber are combined with the ease of processing of thermoplastics. These polymers contain up to 10 mol% of ionic group. These ionomeric TPEs are typically prepared by copolymerization of a functionalized monomer with an olefinic unsamrated monomer or direct functionalization of a preformed polymer [68-71]. The methods of preparation of various ionomeric TPEs are discussed below. 

Accelerated sulfur vulcanization is the most widely used method. This method is useful to vulcanize NR, SBR, BR, HR, NBR, chloroprene mbber (CR), XIIR, and EPDM mbber. The reactive moiety present in aU these mbbers is... 

Most accelerators used in the accelerated sulfur vulcanization of other high diene rubbers are not applicable to the metal oxide vulcanization of CR. An exception is the use of so-called mixed-curing system for CR, in which metal oxide and accelerated sulfur vulcanization are combined. Along with the metal oxides, TMTD, DOTG, and sulfur are used. This is a good method to obtain high resilience and dimensional stability. 

The specimen was prepared by the following method. After mixing HAF carbon black (50 phr) with natural rubber (NR) in a laboratory mixer, carbon gel was extracted from unvulcanized mixture as an insoluble material for toluene for 48 h at room temperamre and dried in a vacuum oven for 24 h at 70°C. We made the specimen as a thin sheet of the carbon gel (including carbon black) by pressing the extracted carbon gel at 90°C. The cured specimen was given by adding sulfur (1.5 phr) to the unvulcanized mixture and vulcanized for 30 min at 145°C. The dynamic viscoelastic measurement was performed with Rheometer under the condition of 0.1% strain and 15 Hz over temperatures. 

EB irradiation (like the other ionizing radiation techniques) can bring about the vulcanization of saturated chemically inert polymers which cannot be achieved in the conventional thermochemical curing methods [44]. 

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