Vulcanization radiation

If crosslinking is performed in a dry polymer (rubber vulcanization, radiation, etc.), then 7 I. Crossliiiking of chains in solution is a different thing (Dusek and Prins. 1969). 

Lead sesquioxide is used as an oxidation catalyst for carbon monoxide ia exhaust gases (44,45) (see Exhaust control), as a catalyst for the preparation of lactams (46) (see Antibiotics, P-lactams), ia the manufacture of high purity diamonds (47) (see Carbon, diamond-natural), ia fireproofing compositions for poly(ethylene terephthalate) plastics (48), ia radiation detectors for x-rays and nuclear particles (49), and ia vulcanization accelerators for neoprene mbber (50). 

The oldest technology involved in the elastomer blending and vulcanization process is essentially a temperature controlled two roll mill as well as internal mixers followed by an optimum degree of crosslinking in autoclave molds (compression, injection, etc.) in a batch process or in a continuous process such as continuously heated tube or radiated tubes. A few examples of laboratory scale preparation of special purpose elastomeric blends is cited here. 

Romero-Sanchez M.D., Pastor-Bias M.M., Martm-Martmez J.M., Zhdan P.A., and Watts J.M., 2001, Surface modifications in a vulcanized rubber using corona discharge and ultraviolet radiation treatments, J. Materials Sci., 36(24), 5789-5799. 

Over the last few decades, the use of radiation sources for industrial applications has been widespread. The areas of radiation applications are as follows (i) Wires and cables (ii) heat shrinkable tubes and films (iii) polymeric foam (iv) coating on wooden panels (v) coating on thin film-video/audio tapes (vi) printing and lithography (vii) degradation of polymers (viii) irradiation of diamonds (ix) vulcanization of mbber and rubber latex (x) grain irradiation. 

EB irradiation (like the other ionizing radiation techniques) can bring about the vulcanization of saturated chemically inert polymers which cannot be achieved in the conventional thermochemical curing methods [44]. 

The tensile strength of NR compounds in the presence of cross-link promoters such as dichlorobenzene is increased as compared to the sulfur-accelerator and peroxide-curing systems. The retention of the maximum tensile strength at elevated temperamres is greater for radiation cured than for chemically vulcanized NR [326,327]. Also reported are a higher abrasion resistance [328] and a lower flex life in the case of radiation-cured system. Effect of phenoxy ethyl acrylate (PEA)... 

UV stabilizer Additive that retards degradation caused by UV radiation, vulcanization Cross-linking with heat and sulfur. 

Lead trioxide is a catalyst for oxidation of carbon monoxide in exhaust gases. Other uses are vulcanizing neoprene rubber fireproofing plastics detecting radiation and manufacturing high-purity diamonds. 

Hot air, steam, and hot water vulcanization is widely used in the latex industry, and fluid-bed heat transfer and electronic microwave curing has also been used. Cross-linking by electron radiation has been experimentally used, but has not yet been developed commercially. 

Identical to chemically cross-linked (vulcanized) elastomers, the modulus of radiation cured gum elastomers depends on the concentration of elastically effective network strands and temperature. ... 

The prevulcanization of natural rubber in latex form has also been a subject of much investigation. The cross-linking mechanism is not yet fully understood, but the water apparently plays a major role in it. Irradiation results in the cross-linking of the rubber molecules and in coarsening of the latex particles. A process of cross-linking of natural rubber latex has been developed to the point that it can be used for an industrial-scale application. The irradiation is performed in aqueous media by electron beam without a prorad (sensitizer) at a dose of 200 kGy (20 Mrad) or in the presence of n-butyl acrylate at considerably lower doses, typically 15 kGy. The cross-linked film exhibits physical properties comparable to those obtained from sulfur cured (vulcanized) film. As an alternative, the addition of a variety of chloroal-kanes makes it possible to achieve a maximum tensile strength with radiation doses of less than 5 Mrad (50 kGy). ... 

The most common compound for peroxide cross-linking of PE in the wire and cable industry is dicumyl peroxide (DCP), which decomposes at 120-125°C (248-257°F), generating free radicals needed for the process plus by-products (carbinol, acetophenone, and methane). The production line for continuous vulcanization of wire and cables by peroxide must be about 200 m (61 ft) long. 2 The plant space required for radiation cross-linking using... 

Cure (curing) 1. Polymerization or cross-linking (or both) by radiation (UV or EB). 2. Cross-linking or vulcanization of elastomeric materials. 

In the case of rubber this cross linking is called vulcanization. Experiments conducted in 1946 at the Clinton Pile (D6) demonstrated a slight curing action of pile irradiation on natural rubber. Charlesby has shown that the degree of cross linking is directly proportional to radiation dose. Approximately 50 X 106 r. produces one cross link/90 isoprene units. 

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