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Migration in elastomers

The pigment also lends itself to application in elastomers, such as natural rubber blends. It is migration fast enough to satisfy most specifications. P.R.53 1 is also completely bleed resistant in natural rubber, although some color is transferred into the wet cotton cloth liner, the wrapper (Sec. 1.8.3.6). P.R.53 1 is lightfast enough for most applications. Products containing P.R.53 1 are not always entirely fast to hot water or alcohol. [Pg.321]

Amerongen [34a] has an early review on curative migration in het-erophasic elastomer blends based on optical and radiochemical analyses. A later, more detailed work by Gardiner [34b-d] used optical analysis to study curative diffusion across the boundaries of elastomer blends consisting of binary combination of polymers of CllR, HR, EPDM, CR, SBR, BR, and NR. Gardiner measured a diffusion gradient for the concentration change as a function of distance and time. His measurements for the diffusion of accelerator and sulfur from HR to other elastomers are listed in Table IV. [Pg.541]

The migration ofcuratives was observed to happen very quickly (e.g., 3 satl50°C). A diffusion gradient may be produced between the dissimilar elastomers well before any vulcanization occurs. The practical consequences of the solubility and diffusion differences in elastomer blends are curative imbalance between the component phases and associated over- and under-cure. [Pg.190]

The elastomeric sheetings made out of butyl and polychloroprene rubbers were first introduced as barriers against water migration. In the early 1960s, EPDM rubbers were commercially available. Considering the superiority of EPDM-based membrane over other elastomers, its application to construction industry as moisture barrier was first introduced in the United States about 30 years ago. [Pg.78]

In their activity, stabilizers normally are consumed other losses may occur through migration into elastomer inclusions or to the surface as well as through fixation to filler/reinforcement surfaces (adsorption). Under low loading levels, chemical aging will definitely determine the lifetime of a PP part. Not only does it create discolorations and aesthetic failure of the surface, but also cracks are induced which increase the stress sensitivity dramatically. [Pg.395]

Many theories have been proposed to explain the mechanism of how antiozo-nants protect elastomeric articles from the effects of ozone. Most support the scavenger model, and indicate that an ideal antiozonant should be capable of migrating in a mbber matrix to the surface whenever the equilibrium of the antiozonant concentration in the compound is upset by the formation of ozonized antiozonant at the surface, but yet not freely migrate to the surface and volatilize out of the elastomer without first reacting with ozone at the surface. On the... [Pg.430]

In addition, silicone polymers in both gel and elastomer forms have been shown to induce a typical subcutaneous foreign body reaction and fibro sarcoma development in rats. The lower-molecular weight silicone polymers may migrate into the adjacent tissues or stimulate other cellular and immunological response. [Pg.243]

Of all the commercially available organic and inorganic polymeric materials, RTV silicone elastomer has proved to he one of the most effective encapsulants used for mechanical and moisture protection of the Integrated Circuitry (1C) devices. A general overview of the RTV silicone elastomer and its commercial preparation and cure mechanism are described. Improved electrical performance of the RTV silicone encapsulant, by immobilizing the contaminant ions, such as Na, K" , Cl , with the addition of the heterocyclic poly-ethers as the contaminant ion scavengers seems to have a potential application as the contaminant ionic migration preventor in the electronic applications. [Pg.171]

A similar effect is observed with silicone elastomers prepared with the co-cure method the surfaces are hydrophobic and deficient in PEO, because PDMS and PHMS constituents are directed to the air interface. Interestingly, in this case, however, the silicones partition differently at the surface. ATR-FTIR demonstrated a relative increase in SiH functionality over PDMS when compared to the control. These results can only be explained by preferential migration of SiH polymer to the surface when sequestering PEO in the interior, perhaps as a result of the reduced steric bulk of each monomer unit. The resulting inside out elastomers with a hydrophilic interior and a SiH rich exterior may offer a potential route to asymmetrically structured siloxanes by subsequent reactions with other olefinic groups. [Pg.45]


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See also in sourсe #XX -- [ Pg.174 ]




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In elastomers

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