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Ingredients for Elastomer- Based Composite Materials: Requirements and Ecological Concerns
Published in Nikolay Dishovsky, Mihail Mihaylov, Elastomer-Based Composite Materials, 2018
Nikolay Dishovsky, Mihail Mihaylov
Sulfur vulcanization in the presence of various types of accelerators and activators is performed in elastomers containing double bonds. The name of this vulcanization type itself shows that the vulcanizing agent in the case is elemental sulfur. Sometimes it is possible to use organic substances containing sulfur in their molecule, which serve as donors of sulfur. Such a substance, for example is tetramethylthiuram disulfide (TMTD). Sulfur vulcanization is a process whereby mono-, di-, and polysulfide cross-links are formed between the elastomeric macromolecules. The advantage of composites wherein polysulfide cross-links dominate is their elasticity. These cross-links, however, are thermolabile, which determines the low resistance of the composites to thermal oxidation and ozone aging. The problem could be overcome using the so-called efficient or semi-efficient vulcanization system. The method requires using a sulfur amount in the range of 0.5-1 phr (parts per hundred rubber), and an accelerator (usually TMTD) at about 2.5-3.5 phr. Thus, significantly more thermostable mono- and disulfide cross-links prevail in the vulcanization network of the elastomer composites built through an effective vulcanization system,7−10 unlike in a conventional vulcanization system, wherein the amount of sulfur is 1-2.5 phr, and the accelerator about 1.2-2 phr.
Medical Rubber Glove Waste As Potential Filler Materials in Polymer Composites
Published in S. M. Sapuan, Y. Nukman, N. A. Abu Osman, R. A. Ilyas, Composites in Biomedical Applications, 2020
M. Nuzaimah, S. M. Sapuan, R. Nadlene, M. Jawaid, R. A. Ilyas
Sulfur vulcanization is a process in which sulfur forms cross-links (bridges) between rubber polymer chains. Cross-linkage between sulfur and rubber polymer chains forms a three-dimensional (3D) chemical network that makes rubber a thermoset material, which is incredibly elastic, insoluble, and infusible with high strength (Martınez et al., 2013, Ikeda, 2014; Safia & Fajula, 2015; Kruželák et al., 2016; Nuzaimah et al., 2018). Figure 9.1 shows the general scheme of rubber-sulfur vulcanization.
Fourier-transform rheology of unvulcanized styrene butadiene rubber filled with increasingly silanized silica
Published in Soft Materials, 2019
Shouliang Nie, Jorge Lacayo-Pineda, Manfred Wilhelm
To improve the dispersion of silica, and thus, enhance the performance of the compounds, there are a variety of strategies, including surface treatment of the fillers and/or adding additives to enhance the compatibility between the silica and diene rubbers. One common approach is to add bifunctional alkyl silane, e.g. 3,3′-tetrathiobis(propyl-triethoxysilane) see Figure 1 (known also in a commercial context as Si-69), as coagent to couple the polymer chains with silica particles (3–4). During the mixing process, silane can functionalize the silica surface via a condensation reaction with the silanol groups on the particle surface at a certain temperature (normally, it is 145–155 °C for Si-69 (5)). During rubber curing, the sulfur containing silane is expected to react with the sulfur vulcanization system so that silica can be chemically coupled with the rubber networks (above 150 °C for Si-69 (5)). The silanized silica particles with lower interparticle interactions gain a better dispersibility in the polymer matrix. Such vulcanizates provide enhanced mechanical dynamic properties to rubbers when compared with CB reinforced ones. Tire treads made from this silane-coupled vulcanizates allow lower rolling resistance (the so-called “green tire” due to the lower fuel consumption) and better wet grip.
Enhancing mechanical properties of prevulcanized natural rubber latex via hybrid radiation and peroxidation vulcanizations at various irradiation doses
Published in Radiation Effects and Defects in Solids, 2018
Sofian Ibrahim, Khairiah Badri, Chantara Thevy Ratnam, Noor Hasni M. Ali
The cis-1,4-polyisoprene polymer is the main component in natural rubber latex (NR). NR itself is a sticky and non-elastic material. The crosslinking of NR molecules via the vulcanization process makes NR heat-stable and elastic, whereby crosslinking causes changes in the physical properties of polymers. At present, there are three popular vulcanization processes being used in natural rubber latex industries; namely sulfur, radiation and peroxide vulcanizations. However, this does not mean that there is no other vulcanization process used to produce vulcanized NR latex. For example, the photo-curing of NR latex via thiol–ene reaction has also become a prominent way to cure NR lately and efforts have been made to implement it in industrial processes (1). Of all three popular vulcanization processes mentioned earlier, sulfur vulcanization produced products with superior tensile strength compared to radiation and peroxide vulcanization. However, sulfur vulcanization is able to produce by-products such as nitrosamines and nitrosatables, carcinogenic materials that may cause cancer and chemical allergies (2, 3).