The preparation of multifunctional accelerators derived from tea phenols and their use in rubber compounds

2017 ◽  
Vol 50 (1) ◽  
pp. 58-70 ◽  
Author(s):  
Sun Jutao ◽  
Wang Lili ◽  
Liu Xiaoling ◽  
Liang Yunhao ◽  
Sun Xuehong
Keyword(s):  
Control Sample ◽  
Molecular Structures ◽  
Tea Polyphenols ◽  
Rubber Matrix ◽  
Hydroxyl Groups ◽  
Chemical Structures ◽  
Transmission Electron ◽  
Rubber Compounds ◽  
Phenolic Hydroxyl Groups ◽  
The Mannich Reaction

Tea polyphenols (TPs) are natural compounds extracted from tea trees whose molecular structures possess many phenolic hydroxyl groups, and therefore are highly reactive. Based on the principle of the Mannich reaction, two types of multifunctional accelerators (Tea polyphenols-mercaptobenzothiazole [TPM] and Tea polyphenols-N-tert-butylbenzothiazole-2-sulphenamide [TPN]) were synthesized by the reaction of TPs with 2-mercaptobenzothiazole and N-tert-butylbenzothiazole-2-sulphenamide, respectively. The chemical structures of TPM and TPN were characterized using Fourier transform infrared spectroscopy, and the curing activity was measured using a vulcameter. The results showed that TPM and TPN had been synthesized successfully and possessed curing activity similar to that of traditional accelerators. TPM and TPN were then used in silica/rubber compounds to determine their effects on processing and on physiomechanical and antiaging properties. The results showed that TPM and TPN improved the curing rate of silica compounds and also improved the dispersion of silica in a rubber matrix as observed using transmission electron microscopy. Furthermore, the retention of tensile strength was higher for TPM and TPN vulcanizates after air aging than it was for the control sample. These results indicated that TPM and TPN, which incorporated the functions of a “curing accelerator,” a “silica surface modifier,” and an “antidegradant,” were new multifunctional accelerators for silica/rubber compounds.

scholarly journals Effect Of Liquid Rubbers On The Thermal And Adhesion Properties Of The Tire Skim Compound

2021 ◽  
Vol 4 (1) ◽  
pp. 101-110
Author(s):  
Furkan Celtik ◽  
Enes Kilic ◽  
Mustafa Ozgur Bora ◽  
Ekrem Altuncu
Keyword(s):  
Mechanical Properties ◽  
Dynamic Mechanical Properties ◽  
Rubber Matrix ◽  
Hydroxyl Groups ◽  
Rubber Compound ◽  
Carboxyl Content ◽  
Adhesion Properties ◽  
Rubber Compounds ◽  
Reaction Extent ◽  
And Migration

Polymeric textile cords, steel cords and steel cables are mainly reinforcing materials that are used in tire production. Polymeric textile cords such as Polyester (PEs), Nylon, Aramid and Rayon are commonly treated with bi-functional resorcinol formaldehyde latex (RFL) to obtain desired adhesion to rubber matrix. PEs cords are known as their poor adhesion to both RFL and rubber compounds due to limited reactivity on the surface and poor reaction extent between methylol and hydroxyl groups of RFL. Increasing carboxyl content on PEs surface or in the rubber compound is one of the best strategies to overcome this adhesion problem. Liquid rubbers, which can co-vulcanize with solid rubbers, are also strong alternatives of process oils with their excellent plasticizing effect without deterioration in mechanical properties of the resulting material. Co-vulcanization also improves the stability of this additive and prevents possible bleeding and migration during service life of the tire. In this study, carboxylated grafted liquid isoprene rubber has been incorporated to rubber compound to improve adhesion in PEs-RFL-Rubber ternary system. Rheological and dynamic-mechanical properties of reactive liquid rubber containing tire rubber compounds have been evaluated extensively, as well as H-adhesion behaviour of PEs cord-rubber composite matrix.

scholarly journals The Therapeutic Implications of Tea Polyphenols Against Dopamine (DA) Neuron Degeneration in Parkinson’s Disease (PD)

Cells ◽  
2019 ◽  
Vol 8 (8) ◽  
pp. 911 ◽  
Author(s):  
Zhou ◽  
Xie ◽  
Saw ◽  
Ho ◽  
Wang ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Signaling Pathways ◽  
Tea Polyphenols ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Groups ◽  
Neuron Degeneration ◽  
Endogenous Dopamine ◽  
Oxidative Signaling ◽  
Phenolic Hydroxyl Groups

: Accumulative evidence indicated that the pathologically accumulated metal ions (iron species and Mn3+) and abnormally up-regulated monoamine oxidase B (MAOB) activity induced oxidation of endogenous dopamine (DA) can lead to mitochondria impairment, lysosome dysfunction, proteasome inhibition, and selective DA neuron vulnerability, which is implicated in the pathogenesis of Parkinson’s disease (PD). The DA oxidation can generate deleterious reactive oxygen species (ROS) and highly reactive DA quinones (DAQ) to induce DA-related toxicity, which can be alleviated by DA oxidation suppressors, ROS scavengers, DAQ quenchers, and MAOB inhibitors. On the other hand, the nuclear factor erythroid 2-related factor 2 (Nrf2)-Keap1 and Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) anti-oxidative and proliferative signaling pathways play roles in anti-oxidative cell defense and mitochondria biogenesis, which is implicated in DA neuron protections. Therefore, agents with capabilities to suppress DA-related toxicity including inhibition of DA oxidation, scavenge of ROS, detoxification of DAQ, inhibition of MAOB, and modulations of anti-oxidative signaling pathways can be protective to DA neurons. Accumulative evidence shows that tea or coffee consumptions and smoking are related to deceased PD prevalence with unknown mechanisms. In this study, we investigate the protective capabilities of tea polyphenols and other PD relevant agents to inhibit DA-related toxicity and protect against environmental or genetic factors induced DA neuron degeneration in vitro and in vivo. We find that tea polyphenols can significantly suppress DA-related toxicity to protect DA neurons. The tea polyphenols can protect DA neurons via inhibition of DA oxidation, conjugation with DAQ, scavenge of ROS, inhibition of MAOB, and modulations of Nrf2-Keap1 and PGC-1α anti-oxidative signaling pathways. The tea polyphenols with more phenolic hydroxyl groups and ring structures have stronger protective functions. The protective capabilities of tea polyphenols is further strengthened by evidence that phenolic hydroxyl groups can directly conjugate with DAQ. However, GSH and other sulfhydyl groups containing agents have weaker capabilities to abrogate DA oxidation, detoxify ROS and DAQ and inhibit MAOB; whereas nicotine (NICO) and caffeine (CAF) can only modulate Nrf2-Keap1 and PGC-1α pathways to protect DA neurons weakly. The tea polyphenols are identified to protect against overexpression of mutant A30P α-synuclein (α-syn) induced DA neuron degeneration and PD-like symptoms in transgenic Drosophila. Based on achievements from current studies, the excellent and versatile protective capabilities of tea polyphenols are highlighted, which will contribute and benefit to future anti-PD therapy.

scholarly journals Reactivity of Aliphatic and Phenolic Hydroxyl Groups in Kraft Lignin towards 4,4′ MDI

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2131
Author(s):  
Leonardo Dalseno Antonino ◽  
Júlia Rocha Gouveia ◽  
Rogério Ramos de Sousa Júnior ◽  
Guilherme Elias Saltarelli Garcia ◽  
Luara Carneiro Gobbo ◽  
...  
Keyword(s):  
Experimental Work ◽  
Chemical Structure ◽  
31P Nmr ◽  
Kraft Lignin ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Diphenylmethane Diisocyanate ◽  
Complex Chemical ◽  
Heterogeneous Reactivity ◽  
Phenolic Hydroxyl Groups

Several efforts have been dedicated to the development of lignin-based polyurethanes (PU) in recent years. The low and heterogeneous reactivity of lignin hydroxyl groups towards diisocyanates, arising from their highly complex chemical structure, limits the application of this biopolymer in PU synthesis. Besides the well-known differences in the reactivity of aliphatic and aromatic hydroxyl groups, experimental work in which the reactivity of both types of hydroxyl, especially the aromatic ones present in syringyl (S-unit), guaiacyl (G-unit), and p-hydroxyphenyl (H-unit) building units are considered and compared, is still lacking in the literature. In this work, the hydroxyl reactivity of two kraft lignin grades towards 4,4′-diphenylmethane diisocyanate (MDI) was investigated. 31P NMR allowed the monitoring of the reactivity of each hydroxyl group in the lignin structure. FTIR spectra revealed the evolution of peaks related to hydroxyl consumption and urethane formation. These results might support new PU developments, including the use of unmodified lignin and the synthesis of MDI-functionalized biopolymers or prepolymers.

Synthesis and crystal structure analyses of tri-substituted guanidine-based copper(II) complexes

2021 ◽  
Vol 76 (3-4) ◽  
pp. 193-199
Author(s):  
Muhammad Said ◽  
Sadia Rehman ◽  
Muhammad Ikram ◽  
Hizbullah Khan ◽  
Carola Schulzke
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Molecular Structures ◽  
Hydroxyl Groups ◽  
Synthesis And Crystal Structure ◽  
Pyramidal Geometry ◽  
Tautomeric Forms ◽  
Square Planar ◽  
Nitrogen Donor ◽  
Square Pyramidal Geometry

Abstract Three guanidine-derived tri-substituted ligands viz. N-pivaloyl-N′,N″-bis-(2-methoxyphenyl)guanidine (L1), N-pivaloyl-N′-(2-methoxyphenyl)-N″-phenylguanidine (L2) and N-pivaloyl-N′-(2-methoxyphenyl)-N″-(2-tolyl)guanidine (L3) were reacted with Cu(II) acetate to produce the corresponding complexes. The significance of the substituent on N″ for the resulting molecular structures and their packing in the solid state has been studied with respect to the structural specifics of the corresponding Cu(II) complexes. The key characteristic of the guanidine-based metal complexation with Cu(II) is the formation of an essentially square planar core with an N2O2 donor set. As an exception, in the complex of L1, the substituent’s methoxy moiety also interacts with the Cu(II) center to generate a square-pyramidal geometry. The hydroxyl groups of the imidic acid tautomeric forms of L1–L3, in addition to N″, are also bonded to Cu(II) in all three complexes rather than the nitrogen donor of the guanidine motif.

Ball-Milling Graphite Used for Synthesis of Biocompatible Blue Luminescent Graphene Quantum Dots

2021 ◽  
Vol 6 (2) ◽  
Author(s):  
Zhou J ◽  
◽  
Dong Y ◽  
Ma Y ◽  
Zhang T ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Ball Milling ◽  
Graphene Quantum Dots ◽  
Raw Material ◽  
Hydroxyl Groups ◽  
High Quality ◽  
Widespread Application ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron

Graphene Quantum Dots (GQDs) have been prepared by oxidationhydrothermal reaction, using ball-milling graphite as the starting materials. The prepared GQDs are endowed with excellent luminescence properties, with the optimum emission of 320nm. Blue photoluminescent emitted from the GQDs under ultraviolet light. The GQDs are ~3nm in width and 0.5~2 nm in thickness, revealed by high-resolution transmission electron microscopy and atomic force microscopy. In addition, Fourier transform infrared spectrum evidences the existence of carbonyl and hydroxyl groups, meaning GQDs can be dispersed in water easily and used in cellar imaging, and blue area inside L929 cells were clearly observed under the fluorescence microscope. Both low price of raw material and simple prepared method contribute to the high quality GQDs widespread application in future.

scholarly journals Zagreb Connection Index of Drugs Related Chemical Structures

2020 ◽  
Vol 11 (4) ◽  
pp. 11920-11930
Keyword(s):  
Molecular Structure ◽  
Structure Analysis ◽  
Topological Indices ◽  
Molecular Structures ◽  
Connection Number ◽  
Chemical Structures ◽  
Molecular Structure Analysis

Topological indices are used to test the medicine and pharmacology characteristics of drugs and their molecular structures. The modified first Zagreb connection number index is defined to be used in the analysis of drug structures. In this paper, by means of drug molecular structure analysis and vertex partitioning method, we compute the modified first Zagreb connection number index of graphene, polyomino chains, and Benzenoid systems, etc. These structures are used widely in molecular drug graphs.

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