Storage hardening

Storage disorders Storage hardening Storage media Storage stability Storage tankage... 

Crystallization. Raw natural mbber may freeze or crystallize during transit or prolonged storage, particularly at subzero temperatures. The mbber then becomes hard, inelastic, and usually much paler in color. This phenomenon is reversible and must be differentiated from storage hardening. The rate of crystallization is temperature-dependent and is most rapid at —26° C. Once at this temperature, natural mbber attains its maximum crystallinity within hours, and this maximum is no more than 30% of the total mbber. 

Nevertheless, storage hardening can be effectively inhibited by the addition of a reagent such as hydroxylamine, which produces an oxime via a... 

Natural rubber of consistent Mooney viscosity storage hardening has been inhibited by incorporating a small quantity of a compound which reacts with the aldehydic groups present in the rubber. 

Chloroprene rubber (CR) is well known for its high gum vulcanizate strength arising from strain-induced crystallization. The uncured rubber also shows storage hardening due to slow crystallization. It has excellent physical properties, weather... 

M.J. Gregory, and A.S.Tan, Some observations on storage hardening of Natural Rubber, Proc. Int. Rubber Conf., Kuala Lumpur, Vol. IV, p. 28,1975. 

Modification to a level of 1% is sufficient to delay storage hardening due to crystallization. The modified rubber may be vulcanized with conventional curing agents but the vulcanizates are more highly damped (due to the raised Tg), show lower gas permeability and lower swelling in hydrocarbon oils. 

CV latex is a grade which is treated at an early stage with a small amount of hydroxylamine to inhibit storage hardening. 

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