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Extraction and Chemistry of Rubber Allergens
Published in Robert N. Phalen, Howard I. Maibach, Protective Gloves for Occupational Use, 2023
Both synthetic and natural latexes, also known as elastomers, are colloidal suspensions of polymeric materials in aqueous systems that require vulcanization to produce rubber gloves. Vulcanization is the process where the rubber molecules are polymerized through cross-linking by sulfur to increase tear and tensile strength, stretch ability, and other desired physical properties. CR vulcanization uses metal oxides such as MgO and ZnO. Sulfur vulcanization of latex is a necessary step in the production of NRL, IIR, NBR, EPDM, and SBR gloves. For sulfur crosslinking to occur, the rubber elastomers must have C=C bonds which require modification of EDPM and IIR to be amenable to sulfur vulcanization. The use of sulfur alone produces very slow vulcanization that requires high temperatures resulting in a product that is prone to oxidative degradation and has poor physical properties. The use of chemical accelerators allows for lower vulcanization temperatures and increases vulcanization efficiency. The type of accelerator(s) used is dependent on the type of rubber and desired product properties. Many of these accelerators are known to cause contact allergies.
The Nature of Sulfur Vulcanization
Published in Nicholas P. Cheremisinoff, Elastomer Technology Handbook, 2020
Michael R. Krejsa, Jack L. Koenig
Sulfur vulcanization can be divided into two main categories: unaccelerated and accelerated sulfur vulcanization. Unaccelerated formulations typically consist of sulfur, zinc oxide, and a fatty acid such as stearic acid, while accelerated formulations include an accelerator in the system. A subcategory of accelerated sulfur vulcanization is sulfur-free systems, also referred to as sulfur-donor systems. In these systems the sulfur needed for network formation is supplied by the accelerator, which functions as both an accelerator and sulfur-donor. It should be noted that while unaccelerated sulfur systems are no longer of commercial significance, they are of interest as a starting point to understanding accelerated sulfur vulcanization systems.
Chemicals from Non-hydrocarbons
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
Carbon black produced by the channel process was generally acidic, while those produced by the furnace process and the thermal process are slightly alkaline. The pH of the black has a pronounced influence on the vulcanization time of the rubber. (Vulcanization is a physicochemical reaction by which rubber changes to a thermosetting mass due to cross-linking of the polymer chains by adding certain agents such as sulfur.) The basic nature (higher pH) of furnace blacks is due to the presence of evaporation deposits from the water quench. Thermal blacks, due to their larger average particle size, are not suitable for tire bodies and tread bases, but they are used in inner tubes, footwear, and paint pigment. Gas and oil furnace carbon blacks are the most important forms of carbon blacks and are generally used in tire treads and tire bodies.
Large deformation analysis of a hyperplastic beam using experimental / FEM/ meshless collocation method
Published in Waves in Random and Complex Media, 2023
Omid Azarniya, Gholamhossein Rahimi, Ali Forooghi
The natural rubber compound is made based on Table 1 to analyze the static bending. Vulcanization is a chemical process for converting raw natural rubber into a material with desired properties by adding fillers, activators, sulfur, or other equivalent material and accelerators; these additives modify the rubber by forming cross-links between polymer chains. First, the rubber composition is done on a two-roll mixer mill with a speed of 40 rpm and a mixing time of 10 min. This process improves the mixing of the rubber. Secondly, the natural rubber (SMR) and Carbon Black (N660) are mixed with butadiene rubber (PBR) for 5 min in a Banbury machine. Then, the accelerator (TBBS), stearic acid, oxide, and other substances in Table 1 are added to the mixture for 5–7 min, creating cross-links between the polymer chains and enhancing the mechanical properties of the compound. Finally, after leaving the Banbury machine, the mixture is converted into a strip of the same thickness by a mixer with two rollers. Figure 4 shows the compound after rolling out of the mixer.
Physicochemical properties of high-content rubber modified bio-asphalt using molecular simulation
Published in Petroleum Science and Technology, 2023
Asphalt is a kind of complex compound and the three components model is usually used to describe the molecular structure of asphalt in molecular simulations. The three components (the molar of asphaltene: 1,7-dimethylnaphthalene: n-C22 is 5:27:41) of asphalt molecular model was proposed and used widely (Zhou et al. 2020a) and it is shown in Figure 2a. Bio-oil is derived from biomass pyrolysis and its molecular model can be used single component molecular model (Yang et al. 2018), as shown in Figure 2b. Waste rubber powder consists of the sulfur cross-linked natural rubber (NR), styrene-butadiene rubber (SBR), and butadiene rubber (BR) (Jiao, Pan, and Che 2022). Sulfur and hydrogen disulfide are used as the vulcanizing agent during vulcanization process for rubber. The detailed molecular model of waste rubber powder is shown in Figure 2c. The waste rubber molecular model consists of 5 NR molecule, 3 SBR molecule, and 2 BR molecule. In order to modeling purposes, the degree of polymerization of NR, SBR, and BR was set as 10 because the systems energy is stable when the the degree of polymerization is 10. The contents of waste tire rubber in HRMBA are 20, 25, 30, 35, and 40%, respectively, and the corresponding molecular numbers are 1, 2, 3, 4, and 5, respectively. The bio-oil contents is constant and 20%. The molecule bulk models of HRMBA with different rubber contents are seen in Figure 2d. The molecular structures of HRMA and bio-oil have been used by many researchers and their reliability has been also verified (Zhou and Adhikari 2019; Zhou et al. 2020a).
Waste tire pyrolysis and desulfurization of tire pyrolytic oil (TPO) – A review
Published in Journal of the Air & Waste Management Association, 2023
Moshe Mello, Hilary Rutto, Tumisang Seodigeng
Waste tires are a carbon-rich material (about 85 wt%) composed mainly of synthetic rubber, natural rubber, carbon black, organic and inorganic fillers, and steel. Table 1 shows the typical elemental composition of the waste tire. Variations in raw materials used can affect the elemental composition of the waste tire. The carbon and sulfur contents can sometimes range between 65–85 wt% and 1–2 wt%, respectively. Sulfur, the primary building block of the vulcanization process, is usually added to form cross chains in the rubber structure. Nitrogen and hydrogen contents remain stable at less than 2 wt% and around 6–8 wt%, respectively. From the proximate analysis, the volatile matter content is approximately 66.5 wt%, the fixed carbon about 30 wt%, and the ash content (includes all minerals used in tire fabrication) about 2 wt%. Based on the characteristics, a particle of waste tire free of textile matter and steel has an energy density equivalent to 40 MJ/kg, suggesting a possible application as a fossil fuel alternative (Ahmad and Ahmad 2013; Campuzano et al. 2020; Martínez 2021; Serefentse et al. 2019).