Introduction to Fluoropolymers

Ebnesajjad, Sina

doi:10.1016/b978-081551502-9.50004-1

Cited by 18 publications

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“…Fluoropolymers are macromolecules of choice when severe environmental conditions require high thermal and chemical stability. , These features are due to the presence of fluorine atoms as substituents and are coupled with good mechanical and dielectric properties and low surface energy. , Vinylidene fluoride−hexafluoropropylene (VDF−HFP) random copolymers are an important class of such materials. Their properties can be tuned from those of a semicrystalline thermoplastic to those of a fully amorphous elastomer by increasing the HFP content.…”

Section: Introductionmentioning

confidence: 99%

Copolymerization of VDF and HFP in Supercritical Carbon Dioxide: Experimental Analysis of the Reaction Loci

et al. 2010

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Free radical copolymerization reactions of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) were carried out in supercritical carbon dioxide at T = 50 °C. When ammonium carboxylate perfluoropolyether surfactants were used, the formation of polymer particles was observed provided that HFP mole fraction in the feed was not larger than 0.30. Under these conditions, the effect of the total interphase area of the polymer phase, A p, on the product properties was investigated by comparing experiments with largely different amounts of stabilizer, i.e., ranging from precipitation (smaller A p) to dispersion (larger A p) polymerization systems. We found that the copolymer molecular weight distribution (MWD) is heavily affected by A p. This experimental evidence strongly supports the presence of two reaction sites, the CO2-rich and the polymer-rich phase: the contribution of both is important in the examined range of operating conditions.

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Section: Introductionmentioning

confidence: 99%

Copolymerization of VDF and HFP in Supercritical Carbon Dioxide: Experimental Analysis of the Reaction Loci

et al. 2010

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“…Experimental as well as computational investigations on the transfer hydrogenation of thebaine N -oxide ( 6 ) additionally indicated that the reduction of 4 is considerably faster than for the oxidized derivative ( 6 ) . It is interesting to note that the residence time got longer at elevated temperatures most likely due to the increasing gas permeability of PFA . Thus, we decided to evaluate the applicability of a stainless steel coil instead of residence time units made out of polymeric material.…”

Section: Resultsmentioning

confidence: 99%

Selective Olefin Reduction in Thebaine Using Hydrazine Hydrate and O₂ under Intensified Continuous Flow Conditions

Pieber

Cox

Kappe

2015

Org. Process Res. Dev.

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Hydrocodone, a high value active pharmaceutical ingredient (API), is usually produced in a semisynthetic pathway from morphine, codeine or thebaine. The latter alkaloid is an attractive precursor as it is not used as a remedy itself. The key step in this production route is a selective olefin reduction forming 8,14-dihydrothebaine which can be subsequently hydrolyzed to yield hydrocodone. Unfortunately, standard hydrogenation procedures cannot be applied due to severe selectivity problems. A transfer hydrogenation using in situ generated diimide is the only known alternative to achieve a selective transformation. The most (atom) economic generation of this highly unstable reducing agent is by oxidizing hydrazine hydrate (N2H4·H2O) with O2. In the past, this route was “forbidden” on an industrial scale due to its enormous explosion potential in batch. A continuous high-temperature/high-pressure methodology allows an efficient, safe, and scalable processing of the hazardous reaction mixture. The industrially relevant reduction was achieved by using four consecutive liquid feeds (of N2H4·H2O) and residence time units, resulting in a highly selective reduction within less than 1 h.

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“…Fluorinated polymers represent the most versatile and important group of thermoplastics which are involved in many areas of technology as in the chemical process industries such as piping and pumps in harsh environments,56 or lining in tubes when steel and iron are corroded by the chemical products 57. The strong CF bonds are responsible for their ability to crystallize as well as for their increased thermal and chemical stability.…”

Section: Resultsmentioning

confidence: 99%

“…ECTFE is a copolymer exhibiting useful properties for a wide range of temperatures, from cryogenic temperatures up to 180°C, while ETFE offers resistance to chemicals and weathering, low flammability and stress‐crack resistance. Concerning the structure of the repetition units, ECTFE is an alternated 1 : 1 copolymer of Ethylene and chlorotrifluoroethylene,57 the latter being the monomer used for manufacturing PCTFE. ETFE can be considered equivalent to a poly(vinylidene fluoride) that has a head to head, tail to tail structure.…”

Section: Resultsmentioning

confidence: 99%

Polymer stain resistance: Prediction versus experiment

Narses

Sadaka

Brachais

et al. 2013

J of Applied Polymer Sci

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The coloration of different polymer films (from commodity and packaging films to performance films) by contact with various food coloring substances was evaluated. For this purpose, both solubility parameters as a prediction tool, and immersion experiments for time range between 24 and 1000 h were established. The two predicting tools are the Hoy and Hoftyzer-Van Krevelen (HVK) methods. For PE and PP, HVK's method is preferred for predicting coloration. Neither of the HVK's and Hoy's methods was able to establish a coloration prediction for PET while both methods could predict the staining of PEEK. The coloration of partially and fully fluorinated polymers is well predicted by the Hoy's method. The behavior of PP/PA and PP/PA/PP multilayer films was also studied. Crystallinity degree of polymers, temperature and concentration of coloring molecules are also important parameters, which are not taken into account in solubility theories.

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Introduction to Fluoropolymers

Cited by 18 publications

References 0 publications

Copolymerization of VDF and HFP in Supercritical Carbon Dioxide: Experimental Analysis of the Reaction Loci

Copolymerization of VDF and HFP in Supercritical Carbon Dioxide: Experimental Analysis of the Reaction Loci

Selective Olefin Reduction in Thebaine Using Hydrazine Hydrate and O₂ under Intensified Continuous Flow Conditions

Polymer stain resistance: Prediction versus experiment

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Introduction to Fluoropolymers

Cited by 18 publications

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Copolymerization of VDF and HFP in Supercritical Carbon Dioxide: Experimental Analysis of the Reaction Loci

Copolymerization of VDF and HFP in Supercritical Carbon Dioxide: Experimental Analysis of the Reaction Loci

Selective Olefin Reduction in Thebaine Using Hydrazine Hydrate and O2 under Intensified Continuous Flow Conditions

Polymer stain resistance: Prediction versus experiment

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Product

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Selective Olefin Reduction in Thebaine Using Hydrazine Hydrate and O₂ under Intensified Continuous Flow Conditions