Non-vulcanized rubber

Zmierczak et al.4 have investigated the catalytic hydrocracking of non-vulcanized rubber (SBR, styrene-butadiene copolymers) over superacid solids, consisting of sulfated Zr and Fe oxides. Figure 6.7 shows the GC-MS analysis of the liquids produced at 400 °C over sulfated Fe203, with assignments of the main peaks. Three types of product are observed C5-C9 paraffins produced from the butadiene blocks of the polymer, alkylbenzenes derived from the... 

Tack, dry n. The property of certain adhesives, particularly non-vulcanizing rubber adhesives, to adhere on contact to themselves at a stage in the evaporation of... 

METHOD 41 - IDENTIFICATION OF ACCELERATORS AND ANTIOXIDANTS IN NON-VULCANIZED RUBBER COMPOUNDS. THIN LAYER CHROMATOGRAPHY. ... 

This thin-layer chromatographic method determines a range of accelerators and antioxidants in non-vulcanized rubber compounds in amounts down to 5 ppm. 

Subsequently, much improved thermoplastic polyolefin rubbers were obtained by invoking a technique known as dynamic vulcanisation. This process has been defined (Coran, 1987) as the process of vulcanizing elastomer during its intimate melt-mixing with a non-vulcanizing thermoplastic polymer. Small elastomer droplets are vulcanized to give a particulate... 

Reclaimed rubber can be used in non-vulcanizing general-purpose NR adhesives. It can be used for insulation, packaging materials, and bonding of polyethylene, canvas, metals and wood. 

Unreacted free sulfur can be determined to ISO 7269 1995 — Rubber — Determination of free sulfur. Three methods for the determination of free sulfur in vulcanized rubber are detailed two versions of the copper spiral method and the sodium sulfite method. The copper spiral methods are also applicable, subject to limitations, to unvulcanised rubber. The technique of DSC can detect non-reacted rubber curatives such as residual peroxides. 

Fig. 40 WAXD patterns of non-polar rubbers (a) and polar rubbers filled with 20 phr swollen clay (b). All the vulcanized rubbers contain some curing ingredients like organic accelerator, zinc oxide, etc...

By the process of vulcanization, rubber elasticity, impact resistance, flexibility, thermal stability and many other properties are either introduced or improved. In addition, the crosslinking of non-elastomeric polymers increases the toughness, abrasion resistance and, particularly, the maximum service temperatures of the material. 

For penetration stain, a 0.5 mm thick veneer of white, non-discolouring rubber, is applied under pressure to a sheet of the test rubber and the composite vulcanized. A test piece cut from the composite sheet is exposed to artificial light and examined for staining. The composition of the white veneer is left for agreement between the interested parties. Alternatively, part of a finished product incorporating a veneer may be used or the rubber test piece without the veneer coated with a non-staining white laquer. 

As pointed out by Hirai and Eyring (1959) the values of the compressibilities above and below Tg are so uncertain that we cannot even be sure that there is a discontinuity in the (non-equilibrium) values of (i at Tg. Weir (1953) was unable to find any discontinuity studying the compressibilities of vulcanized rubbers. However, Eq. (43) tells us that A fi cannot be zero because A a is not zero and Acv is not infinite. It is better to compute A ft from known values of A cv, T, V and A a. When this is done, the expected change in the internal pressure at Ta can then be calculated, see the next section. 

We now understand that the material is, in this condition, soft and still coherent, but the question is, for non-cross-linked polymers above Tg as well as for vulcanized rubbers why does it show spontaneous recovery after being stretched As a model we take a chain with freely rotating links stretching of such a chain from a coiled state does not require any energy, while, after stretching, it retains its shape. 

Early work in this field was conducted prior to the availability of powerful radiation sources. In 1929, E. B. Newton "vulcanized" rubber sheets with cathode-rays (16). Several studies were carried out during and immediately after world war II in order to determine the damage caused by radiation to insulators and other plastic materials intended for use in radiation fields (17, 18, 19). M. Dole reported research carried out by Rose on the effect of reactor radiation on thin films of polyethylene irradiated either in air or under vacuum (20). However, worldwide interest in the radiation chemistry of polymers arose after Arthur Charlesby showed in 1952 that polyethylene was converted by irradiation into a non-soluble and non-melting cross-linked material (21). It should be emphasized, that in 1952, the only cross-linking process practiced in industry was the "vulcanization" of rubber. The fact that polyethylene, a paraffinic (and therefore by definition a chemically "inert") polymer could react under simple irradiation and become converted into a new material with improved properties looked like a "miracle" to many outsiders and even to experts in the art. More miracles were therefore expected from radiation sources which were hastily acquired by industry in the 1950 s. 

A growing volume of waste materials, especially vulcanized rubbers and crosslinked polymers are proving difficult to recycle. As an alternative to their disposal in landfills, there have been many attempts to grind these materials and use the products as a substitute for fillers in composite materials. Other non-plastic materials such as glass, paper, natural fibrous materials, and fly ash are also used for filler replacement. There is extensive literature on the use of ground tires as filler replacements. This is a specialized topic with only a minor relationship to fillers. 

Hard rubber, vulcanite, or ebonite, is a hard, tough variety of vulcanized rubber, susceptible of a good polish, and a non-conductor of electricity. It contains 20 to 35 per cent, of 8 (the ordinary vulcanized rubber contains 7 to 10 per cent.). 

Contemporary science considers SA an effective activator (along with ZnO) of sulto vulcanization of non-saturated rubbers. With regards to the mechanism accelerated sulfur vulcanization, most of the presently proposed hypotheses suggest that at the conditions of the process a... 

Stearic Acid - Activator of the Sulfur Vulcanization of Non-Saturated Rubbers... 

The subject of filler reinforcement on vulcanized rubber is very wide and complex. Fillers can be classified as reinforcing, semi-reinforcing and non-reinforcing. All fillers increase the hardness, modulus and stiffness of vulcanized rubber whether or not they are reinforcing or non-reinforcing. It has been established for a very long time that the term reinforcement has been widely used by the rubber technologist to denote the enhancement in the tensile... 

The hydrophilic nature of silica also affects the cure characteristics of rubber compounds, the properties of vulcanized rubber and also the compatibility with non-polar rubber such as natural rubber (NR). Silica retards the vulcanization as it reacts with zinc-accelerator-sulfur complex. These drawbacks can be overcome through the use of silane coupling agents. The most common silane coupling agent used is bis(3-triethoxysilylpropyl) tetrasulfide (TESPT). A silane... 

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