The Experts below are selected from a list of 39 Experts worldwide ranked by ideXlab platform
Francesca Nanni - One of the best experts on this subject based on the ideXlab platform.
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a new green methodology for surface modification of diatomite filler in elastomers
Materials Chemistry and Physics, 2017Co-Authors: F R Lamastra, Stefano Mori, Valeria Cherubini, Manuela Scarselli, Francesca NanniAbstract:Abstract In this work a new, simple and green protocol to introduce a limited content of silanol groups on the surface of an hydrophobic diatomite, in order to be slightly hydrophilic and susceptible to be silanized by bifunctional, sulfur-containing organosilanes for Rubber Applications, is proposed. The chemical modification was carried out at 85 °C in a solution of H 2 O:NaOH:H 2 O 2 . The modified diatomite was then silanized with bis(triethoxysilylpropyl) disulfide by a procedure that does not involve toxic solvent. Morphological features and elemental composition of diatomite were investigated by Field emission scanning electron microscopy coupled with Energy dispersive X-ray spectroscopy. The surface modification and silanization process were assessed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Diatomite was composed by micrometric frustules from different diatom species with pore size ranging from 25 nm to 1 μm. The spectroscopic characterizations confirmed the surface modification of diatomite with some silanols that acted as sites for silanization reaction. The silanized diatomite and the untreated one were used as filler in unvulcanized solvent-cast SBR films in order to verify that the modification does not negatively affect the polymer/filler interface and as consequence the mechanical properties. Mechanical properties of the realized samples were assessed by uniaxial tensile tests. Films filled with 10 wt% of diatomite (untreated or silanized) showed an increase of Elastic Modulus about of 50% and a decrease of the strain at break with respect to SBR samples, while the tensile strength was not significantly affected by the diatomite addition. SEM images of fracture surfaces of tested specimens showed a fine dispersion of both untreated and silanized diatomite in the polymeric matrix and the achieving of a good interfacial adhesion SBR/fillers. The silanized diatomite, as it is potentially able to bind chemically to elastomeric molecules during vulcanization process, could be used in Rubber compounds as semi-reinforcing filler.
Zhicheng Zhang - One of the best experts on this subject based on the ideXlab platform.
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synthesis and characterization of thermally self curable fluoropolymer triggered by tempo in one pot for high performance Rubber Applications
Polymer Chemistry, 2014Co-Authors: Jing Chen, Shaobo Tan, Guoxin Gao, Zhicheng ZhangAbstract:The preparation of functional fluorine materials through chemical modification of commercial fluoropolymers has been recognized as an economic and convenient strategy to expand the application field of fluoropolymers. In this work, a thermally self-curable fluoroelastomer triggered by 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) has been successfully synthesized in one pot and carefully characterized. This strategy involves two competitive processes, including the coupling reaction between macroradicals and TEMPO, and the dehydrochlorination of commercially available poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-co-CTFE)) by a route involving a three-molecule process, together with a small amount of elimination by an E2 mechanism and β-H elimination The structure and properties of the target polymer were demonstrated by nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). The two competitive reaction processes were carefully investigated under various reaction conditions, including different reaction temperatures, reaction times, ligands, solvents, copper salt, and dosage of TEMPO. The resultant polymer is rather stable at ambient temperature and easily cured at high temperature by ‘pulling the trigger’, namely by breaking C–O or O–N bonds, and the free radicals generated in situ are responsible for initiating the crosslinking of double bonds on the polymer main chain. No other additives are required for the crosslinking of the resultant polymer, which provides a facile chemical route to prepare crosslinked fluoropolymers with high purity and excellent mechanical properties. The curing of the resultant polymer could be accomplished in several minutes at 150–160 °C without the need for a post-cure process.
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synthesis of fluoropolymer containing tunable unsaturation by a controlled dehydrochlorination of p vdf co ctfe and its curing for high performance Rubber Applications
Journal of Materials Chemistry, 2012Co-Authors: Junjie Li, Huayi Li, Zhicheng ZhangAbstract:Fluoropolymer containing unsaturation, an important intermediate for many reactions such as radical addition and Michael addition reaction, could be either utilized to synthesize fluoropolymer with desired functions or cured for Rubber Applications, which has rarely been investigated because of the absence of a synthetic strategy. A facile method to synthesize fluoropolymer with tunable unsaturation via controlled dehydrochlorination of commercially available poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-co-CTFE)) catalyzed by tertiary monoamines under mild conditions has been reported in this work. The resultant copolymers are carefully characterized with nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), and thermal gravimetric analysis (TGA). It has been shown that the elimination could be well controlled by employing proper solvent, catalyst and reaction conditions. The typical side reactions catalyzed with amines, such as Michael addition reaction and main chain scission during the dehydrofluorination of fluoropolymer, could be avoided in the present reaction system. The kinetics results indicate that the elimination reaction is in a bi-molecular mechanism (E2), which is well recognized in strong base-catalyzed elimination of halogenated hydrocarbon. The concentration, alkalinity and steric bulk of the catalysts, the polarity and capability to absorb HCl acid of solvents, and the reaction time and temperature exhibit dominant influences on the dehydrochlorination of P(VDF-co-CTFE). The fluoropolymer containing unsaturation is readily cured with peroxide, and the crosslinked fluoropolymer exhibits excellent solvent resistance and mechanical properties.
Valeria Cherubini - One of the best experts on this subject based on the ideXlab platform.
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a new green methodology for surface modification of diatomite filler in elastomers
Materials Chemistry and Physics, 2017Co-Authors: F R Lamastra, Stefano Mori, Valeria Cherubini, Manuela Scarselli, Francesca NanniAbstract:Abstract In this work a new, simple and green protocol to introduce a limited content of silanol groups on the surface of an hydrophobic diatomite, in order to be slightly hydrophilic and susceptible to be silanized by bifunctional, sulfur-containing organosilanes for Rubber Applications, is proposed. The chemical modification was carried out at 85 °C in a solution of H 2 O:NaOH:H 2 O 2 . The modified diatomite was then silanized with bis(triethoxysilylpropyl) disulfide by a procedure that does not involve toxic solvent. Morphological features and elemental composition of diatomite were investigated by Field emission scanning electron microscopy coupled with Energy dispersive X-ray spectroscopy. The surface modification and silanization process were assessed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Diatomite was composed by micrometric frustules from different diatom species with pore size ranging from 25 nm to 1 μm. The spectroscopic characterizations confirmed the surface modification of diatomite with some silanols that acted as sites for silanization reaction. The silanized diatomite and the untreated one were used as filler in unvulcanized solvent-cast SBR films in order to verify that the modification does not negatively affect the polymer/filler interface and as consequence the mechanical properties. Mechanical properties of the realized samples were assessed by uniaxial tensile tests. Films filled with 10 wt% of diatomite (untreated or silanized) showed an increase of Elastic Modulus about of 50% and a decrease of the strain at break with respect to SBR samples, while the tensile strength was not significantly affected by the diatomite addition. SEM images of fracture surfaces of tested specimens showed a fine dispersion of both untreated and silanized diatomite in the polymeric matrix and the achieving of a good interfacial adhesion SBR/fillers. The silanized diatomite, as it is potentially able to bind chemically to elastomeric molecules during vulcanization process, could be used in Rubber compounds as semi-reinforcing filler.
Stefano Mori - One of the best experts on this subject based on the ideXlab platform.
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a new green methodology for surface modification of diatomite filler in elastomers
Materials Chemistry and Physics, 2017Co-Authors: F R Lamastra, Stefano Mori, Valeria Cherubini, Manuela Scarselli, Francesca NanniAbstract:Abstract In this work a new, simple and green protocol to introduce a limited content of silanol groups on the surface of an hydrophobic diatomite, in order to be slightly hydrophilic and susceptible to be silanized by bifunctional, sulfur-containing organosilanes for Rubber Applications, is proposed. The chemical modification was carried out at 85 °C in a solution of H 2 O:NaOH:H 2 O 2 . The modified diatomite was then silanized with bis(triethoxysilylpropyl) disulfide by a procedure that does not involve toxic solvent. Morphological features and elemental composition of diatomite were investigated by Field emission scanning electron microscopy coupled with Energy dispersive X-ray spectroscopy. The surface modification and silanization process were assessed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Diatomite was composed by micrometric frustules from different diatom species with pore size ranging from 25 nm to 1 μm. The spectroscopic characterizations confirmed the surface modification of diatomite with some silanols that acted as sites for silanization reaction. The silanized diatomite and the untreated one were used as filler in unvulcanized solvent-cast SBR films in order to verify that the modification does not negatively affect the polymer/filler interface and as consequence the mechanical properties. Mechanical properties of the realized samples were assessed by uniaxial tensile tests. Films filled with 10 wt% of diatomite (untreated or silanized) showed an increase of Elastic Modulus about of 50% and a decrease of the strain at break with respect to SBR samples, while the tensile strength was not significantly affected by the diatomite addition. SEM images of fracture surfaces of tested specimens showed a fine dispersion of both untreated and silanized diatomite in the polymeric matrix and the achieving of a good interfacial adhesion SBR/fillers. The silanized diatomite, as it is potentially able to bind chemically to elastomeric molecules during vulcanization process, could be used in Rubber compounds as semi-reinforcing filler.
F R Lamastra - One of the best experts on this subject based on the ideXlab platform.
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a new green methodology for surface modification of diatomite filler in elastomers
Materials Chemistry and Physics, 2017Co-Authors: F R Lamastra, Stefano Mori, Valeria Cherubini, Manuela Scarselli, Francesca NanniAbstract:Abstract In this work a new, simple and green protocol to introduce a limited content of silanol groups on the surface of an hydrophobic diatomite, in order to be slightly hydrophilic and susceptible to be silanized by bifunctional, sulfur-containing organosilanes for Rubber Applications, is proposed. The chemical modification was carried out at 85 °C in a solution of H 2 O:NaOH:H 2 O 2 . The modified diatomite was then silanized with bis(triethoxysilylpropyl) disulfide by a procedure that does not involve toxic solvent. Morphological features and elemental composition of diatomite were investigated by Field emission scanning electron microscopy coupled with Energy dispersive X-ray spectroscopy. The surface modification and silanization process were assessed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Diatomite was composed by micrometric frustules from different diatom species with pore size ranging from 25 nm to 1 μm. The spectroscopic characterizations confirmed the surface modification of diatomite with some silanols that acted as sites for silanization reaction. The silanized diatomite and the untreated one were used as filler in unvulcanized solvent-cast SBR films in order to verify that the modification does not negatively affect the polymer/filler interface and as consequence the mechanical properties. Mechanical properties of the realized samples were assessed by uniaxial tensile tests. Films filled with 10 wt% of diatomite (untreated or silanized) showed an increase of Elastic Modulus about of 50% and a decrease of the strain at break with respect to SBR samples, while the tensile strength was not significantly affected by the diatomite addition. SEM images of fracture surfaces of tested specimens showed a fine dispersion of both untreated and silanized diatomite in the polymeric matrix and the achieving of a good interfacial adhesion SBR/fillers. The silanized diatomite, as it is potentially able to bind chemically to elastomeric molecules during vulcanization process, could be used in Rubber compounds as semi-reinforcing filler.
