Analysis of hexafluoropropylene/vinylidene fluoride copolymers by high resolution continuous wave and Fourier transform nuclear magnetic resonance spectrometry
“…Chemical shift assignments for each peak according to probable five-carbon sequences and the integrated areas for different regions used for monomer ratio calculations are presented in Table . The peak assignments in terms of five-carbon sequences were made by comparing our results to those of solution-state 19 F NMR studies of similar polymers. − , We obtained comparable resolution to those of the solution-state NMR studies previously published. 3 VT MAS 19 F NMR spectrum of fluoropolymer copolymer A, composed of 78.8% VF 2 and 21.2% HFP (mole percent).…”
Section: Resultssupporting
confidence: 55%
“…Figure shows the spectrum obtained of copolymer B, which is also a copolymer of VF 2 and HFP. Chemical shift assignments for each peak according to probable five-carbon sequences and integrated areas for different regions used for monomer ratio calculations are presented in Table . − , The spectrum appears to be identical to that of copolymer A. This is not suprising, since the polymers were prepared using identical monomer feed ratios (Table ), but the integrated areas are slightly different.…”
Section: Resultsmentioning
confidence: 95%
“…Chemical shifts were referenced to polytetrafluoroethylene, which was assigned a chemical shift of −121 ppm. Five-carbon sequences were assigned to particular resonances on the basis of solution-state studies of similar compounds. − , Integrated areas of peaks in each spectrum were measured for each compound, and calculations of monomer ratios were based on these values. We estimate that each of the fixed integration values has an error of ±0.1%.…”
Section: Methodsmentioning
confidence: 99%
“…As a result, the type and quantity of monomer sequences can be determined in a fluorocarbon polymer on the basis of 19 F chemical shifts. [2][3][4][5][6][7][8][9][10] The routine analysis of fluoropolymers and monomer ratio determination via 19 F NMR spectroscopy have typically required the polymers to be in solution. Many fluoropolymers, however, are insoluble or intractable and therefore require analysis in the solid state.…”
Section: Introductionmentioning
confidence: 99%
“…A valuable tool for the analysis of the structure of fluorocarbon polymers is 19 F NMR spectroscopy. , In 19 F NMR, neighbors of a particular fluorine nucleus have a significant effect on its chemical shift. As a result, the type and quantity of monomer sequences can be determined in a fluorocarbon polymer on the basis of 19 F chemical shifts. − The routine analysis of fluoropolymers and monomer ratio determination via 19 F NMR spectroscopy have typically required the polymers to be in solution. Many fluoropolymers, however, are insoluble or intractable and therefore require analysis in the solid state.…”
Variable-temperature (VT) solid-state 19 F NMR spectroscopy with high-speed magic-angle spinning (MAS) has been used to study copolymers of vinylidene fluoride and hexafluoropropylene and of vinylidene fluoride and chlorotrifluoroethylene, and terpolymers of vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene. High-resolution spectra were obtained by simultaneously using MAS speeds up to 25 kHz and heating to 250°C. Sufficient resolution was achieved to assign peaks by comparison to results obtained from solution-state NMR studies and to determine the monomer composition of the polymer.
“…Chemical shift assignments for each peak according to probable five-carbon sequences and the integrated areas for different regions used for monomer ratio calculations are presented in Table . The peak assignments in terms of five-carbon sequences were made by comparing our results to those of solution-state 19 F NMR studies of similar polymers. − , We obtained comparable resolution to those of the solution-state NMR studies previously published. 3 VT MAS 19 F NMR spectrum of fluoropolymer copolymer A, composed of 78.8% VF 2 and 21.2% HFP (mole percent).…”
Section: Resultssupporting
confidence: 55%
“…Figure shows the spectrum obtained of copolymer B, which is also a copolymer of VF 2 and HFP. Chemical shift assignments for each peak according to probable five-carbon sequences and integrated areas for different regions used for monomer ratio calculations are presented in Table . − , The spectrum appears to be identical to that of copolymer A. This is not suprising, since the polymers were prepared using identical monomer feed ratios (Table ), but the integrated areas are slightly different.…”
Section: Resultsmentioning
confidence: 95%
“…Chemical shifts were referenced to polytetrafluoroethylene, which was assigned a chemical shift of −121 ppm. Five-carbon sequences were assigned to particular resonances on the basis of solution-state studies of similar compounds. − , Integrated areas of peaks in each spectrum were measured for each compound, and calculations of monomer ratios were based on these values. We estimate that each of the fixed integration values has an error of ±0.1%.…”
Section: Methodsmentioning
confidence: 99%
“…As a result, the type and quantity of monomer sequences can be determined in a fluorocarbon polymer on the basis of 19 F chemical shifts. [2][3][4][5][6][7][8][9][10] The routine analysis of fluoropolymers and monomer ratio determination via 19 F NMR spectroscopy have typically required the polymers to be in solution. Many fluoropolymers, however, are insoluble or intractable and therefore require analysis in the solid state.…”
Section: Introductionmentioning
confidence: 99%
“…A valuable tool for the analysis of the structure of fluorocarbon polymers is 19 F NMR spectroscopy. , In 19 F NMR, neighbors of a particular fluorine nucleus have a significant effect on its chemical shift. As a result, the type and quantity of monomer sequences can be determined in a fluorocarbon polymer on the basis of 19 F chemical shifts. − The routine analysis of fluoropolymers and monomer ratio determination via 19 F NMR spectroscopy have typically required the polymers to be in solution. Many fluoropolymers, however, are insoluble or intractable and therefore require analysis in the solid state.…”
Variable-temperature (VT) solid-state 19 F NMR spectroscopy with high-speed magic-angle spinning (MAS) has been used to study copolymers of vinylidene fluoride and hexafluoropropylene and of vinylidene fluoride and chlorotrifluoroethylene, and terpolymers of vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene. High-resolution spectra were obtained by simultaneously using MAS speeds up to 25 kHz and heating to 250°C. Sufficient resolution was achieved to assign peaks by comparison to results obtained from solution-state NMR studies and to determine the monomer composition of the polymer.
Due to their excellent chemical stability, fluoroelastomers have been widely used in various severe circumstances since birth. At present, carbon blacks and inorganic fillers are the two most prominent reinforcing agents in fluoroelastomers. However, despite the rise of silica in the rubber industry, it is still difficult to apply this non‐carbon filler alone as a reinforcing agent in fluoroelastomer. Research on the interaction between silica and fluoroelastomer is even less and not systematical. Based on the above, we analyzed the interaction between silica and fluoroelastomer under different conditions through x‐ray photoelectron spectroscopy (XPS), Fourier‐transform infrared spectroscopy, bound rubber (BR) content analysis and rheological properties, and so forth. The interaction between fluoroelastomer and silica can be characterized by the binding energy variation at different temperatures (especially 260°C the new peak at about 685 eV) and wavenumber shift of Si–OH and Si–O–Si in XPS and infrared (IR) analysis, respectively. The BR content varied with loading, temperature, and atmosphere, reflecting the strength of the interaction from a macro perspective. The evolution of the rheological curves of different recipes and test conditions correlate closely with the results of XPS, IR, and BR content analysis, which also shows the sensitive response of polymer‐filler interaction to temperature and load. The observation results of transmission electron microscopy (TEM) directly demonstrate the differences in the dispersion of fillers at different temperatures. The proposed mechanism of fluoroelastomer–silica interaction mode will provide us with novel approaches to the applications of silica in the fluorine industry.Highlights
X‐ray photoelectron spectroscopy analysis indicates new fluorine species on the interfaces.
Infrared and bound rubber tests verify the fluoroelastomer–silica interactions.
Rheological curves reflect the interaction strength.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
