Elastomers flex cracking

A machine for determining the resistance of elastomers to flex cracking. It is used particularly in the evaluation of shoe soling materials. Rotational Moulding... 

Ecdel [Eastman], TM for an elastomer which imparts excellent low-temperature resistance that significantly reduces product loss due to flex cracking and shattering during cold weather distribution. 

Ecdel Elastomer is ideal for applications in pharmaceutical packaging where low extractables, toughness, flex crack resistance, and utility in harsh environments are required. ... 

Blends of NR and ethylene-vinyl acetate copolymer (EVA) (physical blends and statically vulcanized) combine the good elastomeric and mechanical properties of NR with the excellent ageing and flex crack resistance of EVA. Blends of NR/EVA copolymer are becoming an important rubber/thermoplastic elastomer blend. Applications of these materials can be found in fields where... 

The properties required of a liner to perform this function include the ability to adhere permanently to the tyre carcass, heat resistance, flexibility and flex crack resistance over the full operating temperature range and a low level of permeability to air and moisture. Regular butyl rubber cannot be used in this application except, in the form of butyl reclaim, as a flexible, highly impermeable filler for other elastomers, because it cannot be made to adhere strongly enough to the tyre carcass. Bromobutyl rubber possesses all the properties, in ample measure, required for premium quality inner liners, but a few parts of natural rubber are normally included in chlorobutyl liner stocks to ensure that they have adequate cured bond strength (see Tables 16 and 17). 

The combination of elastomers used in the formulation shown in Table 23 provides an essential balance of adhesion, low heat build-up, and excellent resistance to ozone, weathering and flex cracking. Ultra-white grades of talc and clay were used. Bromobutyl would scorch if substituted directly for the chlorobutyl in this formulation. 

Some usability problems did, however, occur with the BCLCE too. Excessive heat cycles above the isotropic transitions deteriorated the alignment of the BCLCE this, however, had to be risked since the isotropic phase was one of the control groups of the experiment. Flexing at or near room temperatm-e (in the glassy phase of the elastomer) created tears and cracks in the system as well. In other words, the BCLCE has to operate in the nematic temperature range not only because this is where the gi-... 

Antiozonants are special antidegradants used by the rubber industry to protect cured rubber articles from attack by atmospheric ozone, which can be particularly potent if the rubber is unprotected. Those elastomers (NR, SBR, BR, and so on) with carbon-carbon double bonds in the polymer chain are the most susceptible to ozone attack. Ozone attack is more acute with rubber articles that in service are undergoing rapid and repeated deformation (flexing). This attack is worst when the deformation is elongation, and it manifests itself in the formation of surface cracks in the rubber. In service, these cracks will progressively grow and finally result in premature failure of the rubber article. Though observed and suffered for more than a century, this problem was only understood and remedied in the mid-twentieth century. 

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