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Role of Occupational Neurotoxicants in Psychiatric and Neurodegenerative Disorders
Published in Lucio G. Costa, Luigi Manzo, Occupatinal Neurotoxicology, 2020
Stefano M. Candura, Luigi Manzo, Lucio G. Costa
Presently, organotin compounds are mainly used as pesticides, antioxidants, catalysts, lubrificants, and polymer stabilizers. After the Stalinon catastrophy, other cases of accidental acute organotin poisoning occurred in the occupational setting. Signs and symptoms similar to those induced by TET (headache, vertigo, asthenia, photophobia, nausea and vomiting), though less severe, appeared in two farmers a few days after the exposure to a fungicide formulation containing triphenyltin (TPT).40 Rey and colleagues41 reported six workers who were exposed to dimethyltin (DMT) and trimethyltin (TMT) while cleaning a caldron. Once again, clinical manifestations appeared after a latency period (one-three days). They included headache, tinnitus, deafness, impaired memory, disorientation, aggressiveness, psychotic behavior, syncope, loss of consciousness and, in some cases, respiratory depression requiring ventilatory assistance. One patient died. Postmortem examination revealed cerebral edema with irreversible cell damage in the area of the amygdala. Two patients suffered permanent sequelae. The other three victims recovered, but complained of memory loss for about six months.41
Inorganic Nanoparticles for Catalysis
Published in Claudia Altavilla, Enrico Ciliberto, Inorganic Nanoparticles: Synthesis, Applications, and Perspectives, 2017
In the case of metal nanoparticles, they can be used like the homogeneous catalyst as colloidal dispersion in solution as well as the heterogeneous catalyst supported on inorganic supports, as shown in Figure 17.4. When metal nanoparticles are used in a colloidal state in solution, the stability of the colloid is a key factor to get active catalysts. Colloidal dispersion can be stabilized by electric or steric repulsion between particles. In order to get the stable dispersion even under the severe reaction conditions, the electric stabilization is not enough but the steric stabilization using polymer stabilizers are effective. In the history of colloid chemistry, several researchers tried to use metal colloid as a catalyst. However, the activity could not be kept for enough long period for the reaction. Hirai et al. developed a new method to prepare stable polymer-protected metal colloids by the reduction of metal ions with alcohol in the presence of water-soluble polymers (Hirai et al. 1979, Hirai and Toshima 1986). The polymers can coordinate to the metal ions before reduction, and the coordination to metal atoms and the metal nanoparticles are kept after the reduction, as shown in Figure 17.5, which results in stable colloidal dispersions of metal.
Degradation and Protection
Published in Anil K. Bhowmick, Current Topics in ELASTOMERS RESEARCH, 2008
Rabin N. Datta, Nico M. Huntink
To limit the thermal oxidative deterioration of elastomers and their vulcanizates during storage, processing, and use, different systems of antioxidants are used. The activity of the antioxidants depends on their ability to trap peroxy and hydroperoxy radicals and their catalytic action in hydroperoxide decomposition. Their compatibility with the polymers also plays a major role. Moreover, it is very important to limit antioxidant loss by extraction (leaching) or by volatilization. Food packaging and medical devices are areas in which additive migration or extraction is of major concern. Contact with oils or fats could conceivably lead to ingestion of mobile polymer stabilizers. In an effort to address this concern, the U.S. Food and Drug Administration (FDA) has set a code of regulations governing the use of additives in food contact applications [79]. These regulations contain a list of acceptable polymer additives and dose limits for polymers, which may be used for specific food contact. Inclusion of a particular compound in this list depends both on specific extractability and toxicological factors. Obviously, polymer-bound stabilizers cannot be extracted and would therefore prevent inadvertent food contamination. An additional consideration is the effect of additive migration on surface properties. As additives migrate or bloom to the polymer surface, the ability to seal or coat the surface may deteriorate. This affects coating adhesion and lamination peel strength.
Effect of synthetic and natural polymers on reducing bauxite residue dust pollution
Published in Environmental Technology, 2020
Xuhan Ding, Guang Xu, Wei Zhou, Mahinda Kuruppu
Polymer stabilization is one of the effective ways in mitigating dust emission. Due to chemical reaction and physical bonding, a crust with enhanced strength is formed after the polymer stabilizers are sprayed on the red sand surface. Polymer stabilizers are normally classified into synthetic and natural polymers. Synthetic polymers (SPS) have been well investigated in previous studies on enhancing the structure strength and erosion resistance of treated materials. For example, several studies investigated the effectiveness of poly(methyl methacrylate) (PMMA) and polyvinyl acetate on improving the unconfined compressive strength (UCS) of soil, and found that the UCS increases linearly with stabilizer concentration in a certain range [9,10], and this improvement levelled off with further increased concentrations [11,12]. When applied to soil and sand, different type of polymer stabilizers were reported to increase the cohesion force [12] and enhance the wind erosion resistance [13].