Formulation of Elastomers

Typically, carbon blacks would be used to enhance strength characteristics, while minerals provide a more modest strength enhancement at significantly rednced cost. All modify processing performance and allow the production of articles that could not otherwise be fabricated. 

A rubber formulation may be broken down into a number of component groups, which has a specific function. These are listed in Table 7.1 and discussed by class below. 

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Uses Soft segment In formulation of elastomers such as thermoplastic urethanes, coatings, fibers, adhesives and sealants, cast urethanes, and copolymers... 

Flame and Smoke Retardants. Molybdenum compounds are used extensively as flame retardants (qv) (93,94) in the formulation of halogenated polymers such as PVC, polyolefins, and other plastics elastomers and fabrics. An incentive for the use of molybdenum oxide and other molybdenum smoke and flame retardants is the elimination of the use of arsenic trioxide. Although hydrated inorganics are often used as flame retardants, and thought to work by releasing water of crystallization, anhydrous molybdenum oxides are effective. Presumably the molybdenum oxides rapidly form... 

Certain grades and formulations of the fluorocarbon elastomers are qualified under the code of Eederal Regulations, 21, Eood and Dmgs, Part 177.2600 for use as mbber articles whose intended appHcations requite repeated or continuous contact with food. Elastomer suppHers will provide assistance in formulating for specified uses. 

While there are a large number of elastomers that can be formulated into pressure sensitive adhesives, the following list is intended to focus on commercially significant materials. Two subsets are differentiated in Table 1 those polymers that can be inherently tacky, and those that require modification with tackifiers to meet the Tg and modulus criteria to become pressure sensitive. 

Thermoplastic block copolymers were used for pressure-sensitive and hot-melt rubber adhesives as from the middle sixties. These adhesives found application in packaging, disposable diapers, labels and tapes, among other industrial markets. The formulation of these adhesives generally includes an elastomer (generally containing styrene endblocks and either isoprene, butadiene or ethylene-butylene midblocks) and a tackifier (mainly a rosin derivative or hydrocarbon resin). 

Typical formulation of hot-melt rubber adhesive Thermoplastic elastomer 100 phr... 

Formulation of a solvent-borne CR. A typical formulation of a solvent-borne CR adhesive may include the following components (fillers are not commonly added and curing agents are added to improve heat resistance) (1) polychloroprene elastomer (2) metal oxides (3) resins (4) antioxidants (5) solvents (6) fillers (7) curing agents (8) other modifiers. 

Since EPDM is a cheaper elastomer, it is often added to SBR to reduce cost. Zhao et al. have studied the effects of curative and accelerator concentration as well as the effect of mixing on the properties of ablend compound containing 70 parts of SBR and 30 parts of EPDM [41]. Table 11.18 gives the general formulation of the blend compounds. 

With amine initiators the so-called self-catalyzed polyols are obtained, which are used in the formulation of rigid spray foam systems. The rigidity or stiffness of a foam is increased by aromatic initiators, such as Mannich bases derived from phenol, phenolic resins, toluenediamine, or methylenedianiline (MDA). In the manufacture of highly resilient flexible foams and thermoset RIM elastomers, graft or polymer polyols are used. 

Most of the formulations of silicone elastomers that can be crosslinked at room temperature contain an a, co-dihydroxylated polysiloxane and a crosslinking agent with more than two labile Si-X groups ... 

Thermogravimetric analysis can yield a considerable amount of information about the composition of an elastomer system and is a common means of testing of EPDM rubber compounds [51]. The DTG curve may serve as an identifier of the type of elastomer in a compounded formulation. 

Accelerated sulfur formulations are the most common vulcanisation systems used in commercial and industrial applications. Therefore, research on both the fundamental and applied aspects of accelerated sulfur vulcanisation is ongoing. Several reviews of the chemistry and/or physics of accelerated sulfur-vulcanisation of elastomers have been published [13, 14, 22, 23]. 

The incorporation of carbon black into elastomeric systems is a process of significant commercial importance. However, the additional stiffness of the sample imparted by the reinforcement effect of fillers is not favourable in terms of the experimental conditions for high-resolution NMR spectroscopy. Electric conductivity of the carbon black may also interfere to some extent. Under these circumstances, filled formulations are not widely used for the study of elastomer vulcanisations where high resolution and signal-to-noise ratios are required to detect small amounts of vulcanisation products. 

Elastomer materials specifications usually do not focus on the adhesive properties, but mainly address the chemical and physical properties of the rubber. Thus, the supplier has wide latitude within the specification to make changes in the compound formulation that could be disastrous to the adhesive bond. One solution is to qualify every new lot of elastomer material for adhesion as well as the more standard properties. 

Chloropropyl Containing Copolymers. Copolymer (IV), consisting of 60 mole % Me2SiO and 40 mole % ClCH2CH2CH2Si0i.5, was placed in a microwave oven at 1 KW input. At the end of 5 min the copolymer became very hot (>100°C). This means that if the copolymer is used to formulate an elastomer along with a curing agent one should be able to cure the sealant with microwave. 

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