Ebonites solid

When there is no volume change, as when an elastomer is stretched, Poisson s ratio is 0.5. This value decreases as the Tg of the polymer increases and approaches 0.3 for rigid solids such as PVC and ebonite. For simplicity, the polymers dealt with here will be considered to be isotropic viscoelastic solids with a Poisson s ratio of 0.5, and only deformations in tension and shear will be considered. Thus, a shear modulus (G) will usually be used in place of Young s modulus of elasticity E Equation 14.2) where E is about 2.6G at temperatures below Tg. 

However, for construction purposes, solid ebonites were chosen. As is known from rubber chemistry, solid ebonite, commonly known as hard rubber, is a polymer material with sulfur content used for vulcanization. Ebonite, like elastomeric or flexible rubber, is made from a combination of sulfur with polydienes (unsaturated rubbers containing double bonds). The sulfur and polydienes are combined with some auxiliary additives and heated to produce vulcanization. Typical mass ratios of sulfur to rubber are 2 100 for elastomeric rubber and 40 100 for hard rubber. Due to the large degree of sulfide cross linking formed in the vulcanization process, solid ebonite is a hard, non-flexible, plastic-like material possessed of... 

These filters were used in illmenite beneficiation and titanium dioxide plants. These and their parts like agitators, troughs etc., were lined with a semi-hard flexible ebonite of natural rubber to protect the equipment against the abrasive action of the ore and solid particles in the slurries. 

Lees used a modification of his apparatus for solids ( 5.IX O). To the series of 4 cm. diam. discs used for solids, containing a glass disc 0-28 cm. thick of known conductivity, was attached an ebonite ring... 

Ebonite Ebonite is hard natural rubber that is vulcanized to its maximum degree. It is the final product of the reaction of rubber with an excess of sulfur. Ebonite is a hard, inextensible solid containing about 32% combined sulfur. Low-cost fillers and extenders are used primarily to minimize difficulties in handling the rubber-sulfur mix before vulcanization. It has been produced on a commercial scale since about 1860. 

Of course, the first manmade crosslinked polymer was Charles Goodyear s vulcanized rubber with low crosslink density. Since there were only a few sulfur crosslinks between the polyisoprene chains, Charles Goodyear s product, which he called vulcanite, was elastic but had a higher modulus than the original linear Hevea braziliensis. However, Nelson Goodyear s product, called ebonite, produced by the addition of larger amounts of sulfur (25-30%) to natural rubber, was a nonelastic intractable solid. 

A small rectangular block (10x5x3 mm) is excised from the specimen containing the feature of interest and immersed in molten sulfur at 125°C for 24 hours. At the end of this period, the speci-ment is obtained in the form of a hard ebonite-like solid suitable for ultrathin sectioning in the usual manner. In this study, the rubbers were sectioned in the usual manner with a Reichert OMU-2 ultra-microtome and subsequently examined using transmission electron microscopy. 

---