Effects of Coagent Functionalities on Properties of Ultrafine Fully Vulcanized Powdered Natural Rubber Prepared as Toughening Filler in Rigid PVC

Ultrafine fully vulcanized powdered natural rubber (UFPNR) has a promising application as a renewable toughening modifier in polymer matrices. In this work, the effects of acrylate coagents, which had different amounts of functional groups, on properties of UFPNR produced by radiation vulcanization and spray-drying was systematically investigated for the first time. Dipropylene glycol diacrylate (DPGDA), trimethylol propane trimethaacrylate (TMPTMA), and ditrimethylol propane tetraacrylate (DTMPTA) were used as coagents with two, three, and four acrylate groups, respectively. The radiation in the range of 250 to 400 kGy and coagent contents of up to 11 phr were used in the production process. Physical, chemical, and thermal properties of the UFPNR were characterized by swelling analysis, scanning electron microscopy, infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The properties of UFPNR produced by using different type and content of coagents were compared and discussed. The results revealed that UFPNR with the smallest particle size of 3.6 ± 1.1 μm and the highest thermal stability (Td5 = 349 °C) could be obtained by using DTMPTA, which had the highest amount of functional group. It was proposed that the coagent with the greater number of acrylate groups enhanced the crosslinking of natural rubber as it had more reactive groups. Finally, an application of UFPNR as a toughening filler in rigid PVC was demonstrated with 34% improvement of impact strength.

Download Full-text

Iridium-Catalyzed Silylation of C-H bonds in Unactivated Arenes: A Sterically-Encumbered Phenanthroline Ligand Accelerates Catalysis Enabling New Reactivity

10.26434/chemrxiv.7744175 ◽

2019 ◽

Author(s):

Caleb Karmel ◽

Zhewei Chen ◽

John Hartwig

Keyword(s):

High Activity ◽

Functional Group ◽

Activity Analysis ◽

High Reactivity ◽

High Yield ◽

Phen Ligand ◽

Mechanistic Studies ◽

Phenanthroline Ligand ◽

First Time ◽

New System

We report a new system for the silylation of aryl C-H bonds. The combination of [Ir(cod)(OMe)]2 and 2,9-Me2-phenanthroline (2,9-Me2phen) catalyzes the silylation of arenes at lower temperatures and with faster rates than those reported previously, when the hydrogen byproduct is removed, and with high functional group tolerance and regioselectivity. Inhibition of reactions by the H2 byproduct is shown to limit the silylation of aryl C-H bonds in the presence of the most active catalysts, thereby masking their high activity. Analysis of initial rates uncovered the high reactivity of the catalyst containing the sterically hindered 2,9-Me2phen ligand but accompanying rapid inhibition by hydrogen. With this catalyst, under a flow of nitrogen to remove hydrogen, electron-rich arenes, including those containing sensitive functional groups, undergo silylation in high yield for the first time, and arenes that underwent silylation with prior catalysts react over much shorter times with lower catalyst loadings. The synthetic value of this methodology is demonstrated by the preparation of key intermediates in the synthesis of medicinally important compounds in concise sequences comprising silylation and functionalization. Mechanistic studies demonstrate that the cleavage of the aryl C-H bond is reversible and that the higher rates observed with the 2,9-Me2phen ligand is due to a more thermodynamically favorable oxidative addition of aryl C-H bonds.

Download Full-text

Rigid PVC pipes. Differential scanning calorimetry (DSC) method

10.3403/30151901 ◽

2008 ◽

Keyword(s):

Differential Scanning Calorimetry ◽

Scanning Calorimetry ◽

Rigid Pvc ◽

Dsc Method

Download Full-text

Sulfonyl Radical Triggered Selective Iodosulfonylation and Bicycli-zations of 1,6-Dienes

Chemical Communications ◽

10.1039/d1cc03252f ◽

2021 ◽

Author(s):

Shi-Ping Wu ◽

Dong-Kai Wang ◽

Qing-Qing Kang ◽

Guo-Ping Ge ◽

Hongxing Zheng ◽

...

Keyword(s):

Functional Group ◽

High Selectivity ◽

Reaction Conditions ◽

First Time

A novel sulfonyl radical triggered selective iodosulfonylation and bicyclizations of 1,6-dienes has been described for the first time. High selectivity and efficiency, mild reaction conditions, excellent functional group compatibility, and...

Download Full-text

Synthesis of single-crystalline GeS nanoribbons for high sensitivity visible-light photodetectors

Journal of Materials Chemistry C ◽

10.1039/c5tc01435b ◽

2015 ◽

Vol 3 (31) ◽

pp. 8074-8079 ◽

Cited By ~ 66

Author(s):

Changyong Lan ◽

Chun Li ◽

Yi Yin ◽

Huayang Guo ◽

Shuai Wang

Keyword(s):

Visible Light ◽

Vapor Deposition ◽

High Performance ◽

Incident Light ◽

Chemical Vapor ◽

High Sensitivity ◽

Single Crystalline ◽

Promising Application ◽

Photo Detection ◽

First Time

Single-crystalline GeS nanoribbons were synthesized by chemical vapor deposition for the first time. The nanoribbon photodetectors respond to the entire visible incident light with a response edge at around 750 nm and a high responsivity, indicating their promising application for high performance broadband visible-light photo-detection.

Download Full-text

Xanthate-modified nanoTiO2 as a novel vulcanization accelerator enhancing mechanical and antibacterial properties of natural rubber

Nanotechnology Reviews ◽

10.1515/ntrev-2021-0038 ◽

2021 ◽

Vol 10 (1) ◽

pp. 478-487

Author(s):

Yu Liu ◽

Heliang Wang ◽

Xiwei Guo ◽

Mingyuan Yi ◽

Lihong Wan ◽

...

Keyword(s):

Titanium Dioxide ◽

Natural Rubber ◽

High Performance ◽

Antibacterial Properties ◽

Ceric Ammonium Nitrate ◽

Rubber Matrix ◽

Aging Effects ◽

Antibacterial Performance ◽

First Time ◽

Vulcanization Accelerator

Abstract With the emerging of sustainability, the fabrication of effective and eco-friendly agents for rubber industry has attracted extensive attention. In this study, a novel and nontoxic titanium dioxide-based vulcanization accelerator (xanthate-modified nanotitanium dioxide (TDSX)) with excellent antibacterial performance, for the first time, was synthesized under the catalyst of ceric ammonium nitrate. Notably, the thermal stability of xanthate was greatly enhanced after being grafted on titanium dioxide (TiO2) nanoparticles, in which the activation energy was increased from 6.4 to 92.5 kJ/mol, enabling the obtained TDSX with multiple functions, mainly consisting of fabulous vulcanization-promoting effects, reinforcing effects, antibacterial properties, and anti-ultraviolet aging effects for natural rubber (NR). Simultaneously, the TDSX can be effectively and uniformly dispersed in the rubber matrix along with the developed interface interaction between TDSX particles and rubber matrix. Compared to the traditional accelerators 2-mercaptobenzothiazole (M) system, the tensile strength and the tearing strength of NR/TDSX was improved by 26.3 and 40.4%, respectively. Potentially, our work for preparing green vulcanization accelerator can provide a new design strategy for multifunctional high performance elastomer materials.

Download Full-text

Impact of environmental agents on non-woven polylactide/natural rubber agrofiber

E3S Web of Conferences ◽

10.1051/e3sconf/202128507034 ◽

2021 ◽

Vol 285 ◽

pp. 07034

Author(s):

Yulia Tertyshnaya ◽

Maksim Zakharov ◽

Alina Ivanitskikh ◽

Anatoliy Popov

Keyword(s):

Natural Rubber ◽

Uv Irradiation ◽

Thermal Characteristics ◽

Degree Of Crystallinity ◽

Distilled Water ◽

Fibrous Materials ◽

Scanning Calorimetry ◽

Melting Temperatures ◽

Environmental Agents ◽

The Degree Of Crystallinity

In the work an eco-friendly non-woven fiber made of polylactide and natural rubber with a rubber content from 0 to 15 wt.% was obtained by electrospinning. The influence of distilled water and UV irradiation on the agrofibers has been investigated. The water sorption test showed that the addition of natural rubber into the polylactide matrix does not significantly affect the degree of water absorption of the fibrous materials, which is in the range of 49-50.6%. Thermal characteristics after 180 days of degradation in distilled water at 22±2 oC and UV irradiation at a wavelength of 365 nm during 100 hours were determined using the differential scanning calorimetry. Changes in the values for glass transition and melting temperatures, and the degree of crystallinity were determined.

Download Full-text

A comparative study on the effect of higher acrylate on cross-linkable PMMA used as environment friendly latexes

High Performance Polymers ◽

10.1177/0954008319894638 ◽

2020 ◽

Vol 32 (2) ◽

pp. 135-141

Author(s):

Sweta Shukla

Keyword(s):

Thermal Analysis ◽

Differential Scanning Calorimetry ◽

Butyl Methacrylate ◽

Cross Linking ◽

Scanning Calorimetry ◽

Environment Friendly ◽

Glycol Diacrylate ◽

Poly Propylene ◽

Kinetics Of ◽

Scanning Electron

The kinetics of emulsion polymerization of monomers methyl methacrylate (MMA)/ n-butyl methacrylate (BMA) was studied to investigate the effect of cross-linkable monomer poly(propylene glycol diacrylate) (PPGDA). The results showed that by the incorporation of PPGDA rate constant of reaction decreased. Fourier transform infrared spectroscopy and scanning electron microscope were used to characterize the synthesized polymers. The thermal analysis of samples was done by differential scanning calorimetry, and the results were compared by the previous studies with MMA/ n-butyl acrylate (BA) and MMA/2-ethylhexyl acrylate (EHA). The glass transition temperature ( T g) values show that the latexes prepared using BA and EHA as comonomer was suitable for binder purpose, but in the present study the T g is not suitable in case of BMA as higher acrylate comonomer. That may be due to more cross-linking in MMA-BMA-PPGDA. The results conclude that the BA and EHA can be used as the binder, but the use of BMA is limited for the binder in coating applications.

Download Full-text

Non-Isothermal Sublimation Kinetics of 2,4,6-Trinitrotoluene (TNT) Nanofilms

Molecules ◽

10.3390/molecules24061163 ◽

2019 ◽

Vol 24 (6) ◽

pp. 1163 ◽

Cited By ~ 1

Author(s):

Walid Hikal ◽

Brandon Weeks

Keyword(s):

Activation Energy ◽

Analytical Techniques ◽

Heating Rates ◽

Scanning Calorimetry ◽

Absorbance Spectroscopy ◽

Calculated Activation Energy ◽

Sublimation Kinetics ◽

Sublimation Rates ◽

First Time ◽

Kinetics Of

Non-isothermal sublimation kinetics of low-volatile materials is more favorable over isothermal data when time is a crucial factor to be considered, especially in the subject of detecting explosives. In this article, we report on the in-situ measurements of the sublimation activation energy for 2,4,6-trinitrotoluene (TNT) continuous nanofilms in air using rising-temperature UV-Vis absorbance spectroscopy at different heating rates. The TNT films were prepared by the spin coating deposition technique. For the first time, the most widely used procedure to determine sublimation rates using thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) was followed in this work using UV-Vis absorbance spectroscopy. The sublimation kinetics were analyzed using three well-established calculating techniques. The non-isothermal based activation energy values using the Ozawa, Flynn–Wall, and Kissinger models were 105.9 ± 1.4 kJ mol−1, 102.1 ± 2.7 kJ mol−1, and 105.8 ± 1.6 kJ mol−1, respectively. The calculated activation energy agreed well with our previously reported isothermally-measured value for TNT nanofilms using UV-Vis absorbance spectroscopy. The results show that the well-established non-isothermal analytical techniques can be successfully applied at a nanoscale to determine sublimation kinetics using absorbance spectroscopy.

Download Full-text