The Synergistic Effect of Dibenzyldithiocarbamate Based Accelerator on the Vulcanization and Performance of the Silica-Filled Styrene-Butadiene Elastomer

Presence of 1, 3-diphenylguanidine and its derivatives in human urine and their human exposure

Recent studies have demonstrated the widespread presence of 1,3-diphenylguanidine (DPG) and its derivatives in environmental matrices. While, the amount of human exposure to these rubber additives remains unclear. In this study, we collected human urine samples from healthy general adults (n = 221) living in Quzhou, China, and analyzed these samples for DPG and its five derivatives. DPG, 1,6-bis(cyano-guanidino)hexane (HCG), 1,3-di-o-tolylguanidine (DTG) and exhibited detection frequencies exceeding 50% in collected human urine. Presence of HCG, 1-(o-tolyl)biguanide (detection frequency 17%), and 1-(4-cyanophenyl)guanidine (6.0%) in human urine was also demonstrated for the first time. The highest mean human urinary concentration was found for DPG (0.89 ng/mL, < LOD-4.7 ng/mL), followed by DTG (0.57 ng/mL, < LOD-3.1 ng/mL) and HCG (0.34 ng/mL, < LOD-1.8 ng/mL). Male participants had consistently higher average human urinary levels of DPG, DTG, and HCG than female subjects, but none of these differences were significant (p > 0.10). DPG and DTQ consistently showed a decline in the human urinary concentrations as age of the participant increased. DPG (mean 170 ng/kg bw/day, median 137 ng/kg bw/day) had the highest human daily exposure amount, followed by DTG (106 ng/kg bw/day, 91 ng/kg bw/day) and HCG (58 ng/kg bw/day, 38 ng/kg bw/day). The study enhances our understanding of human exposure to these rubber additives, which is crucial for assessing their potential health risks.

Effect of Fillers Modification with ILs on Fillers Textural Properties: Thermal Properties of SBR Composites

In this work, we present the effect of graphene nanoplatelets (GnPs) modification with ionic liquids (ILs). The textural properties of graphene nanoplatelets (GnPs) used as styrene-butadiene rubber's filler and the thermal properties of the composites obtained with the use of the mentioned fillers were investigated. GnPs were modified with 1-butylpyridinium bromide (BPyBr) and 4-methyl-1-butylpyridinium bromide (BmPyBr) through two different ways. One strategy has been to deposit the filler modifier from the solution. The second one involved the modification of the filler with ionic liquids in bulk during the preparation of elastomer blends. Settlement of the proposed ionic liquids onto the GnPs' surface led to significant changes in the textural characteristics. BPyBr has restricted the filler's microporosity, whereas BmPyBr has caused the formation of a more opened filler structure without the increase in its average pore size. GnPs modified with ILs led to reducing the temperature of vulcanization of SBR compounds and affected the thermal stability of the composites.

The Potential Application of Starch and Walnut Shells as Biofillers for Natural Rubber (NR) Composites

The goal of this study was application of corn starch and ground walnut shells in various amounts by weight as biofillers of natural rubber (NR) biocomposites. Additionally, ionic liquid 1-butyl-3-methylimidazolium chloride (BmiCl) and (3-aminopropyl)-triethoxysilane (APTES) were used to increase the activity of biofillers and to improve the curing characteristics of NR composites. The effect of biofillers used and their modification with aminosilane or ionic liquid on the curing characteristics of NR composites and their functional properties, including crosslink density, mechanical properties in static and dynamic conditions, hardness, thermal stability and resistance to thermo-oxidative aging were investigated. Starch and ground walnut shells were classified as inactive fillers, which can be used alternatively to commercial inactive fillers, e.g., chalk. BmiCl and APTES were successfully used to support the vulcanization and to improve the dispersion of biofillers in NR elastomer matrix. Vulcanizates with starch, especially those containing APTES and BmiCl, exhibited improved tensile properties due to the higher crosslink density and homogenous dispersion of starch, which resulted from BmiCl addition. NR filled with ground walnut shells demonstrated improved resistance to thermo-oxidative aging. It resulted from lignin present in walnut shells, the components of which belong to polyphenols, that have an antioxidant activity.