VDF/CTFE copolymers

FIGURE 12.6 (Left) Releasing energy density and (right) energy loss of VDF/CTFE copolymer and three VDF/TrFE/CTFE terpolymers (runs A-2, A-3, A-4). The solid curves are only for guiding the eyes in order to see the trend. 

VDF/CTFE copolymer has thermostability similar to that of VDF/HFP copolymer but possesses advantages of high copolymerization reactivity and wide variation in molar VDF/CTFE ratio, which could effectively reduce the cost of a membrane and give more options to control physical properties of the polymer. By varying ClFE... 

Wang Z, Zhang ZC, Chung TC (2(X)6) High dielectric VDF/TrFE/CTFE terpolymers prepared by hydrogenation of VDF/CTFE copolymers synthesis and characterization. Macromolecules... 

The electrostrictive behavior of P(VDF-CTFE) copolymers was investigated (Li et al. 2004 Li et al. 2006). A high electromechanical response was obtained in these copolymer films. As other PVDF-based polymers, the processing condition plays a very critical role on its properties. For a well-stretched and annealed P (VDF-CTFE) 88/12 copolymer film, a longitudinal electrostrictive strain as much as 5.5 % was obtained. A linear relationship between the strain response and the was observed, which indicates the electrostrictive nature of the electromechanical response in P(VDF-CTFE) copolymers. The corresponding electric field-related electrostrictive coefficient for the copolymer film is obtained as Mss = —1.23 0.02 X 10 (m /V ) (Li et al. 2006). 

Fig. 1.5 Actuation strain as a function of electric field for irradiated P(VDF-TrFE) copolymer (2), P(VDF-TrFE-CTFE) (4), P(VDF-CTFE) (5), and P(VDF-TrFE-CFE)...

Figure 12.3 compares the dielectric constant between VDF/CTFE (92/8 mol%) copolymer and VDF/TrFE/CTFE (65.6/26.7/7.7 mol%) terpolymer. The dielectric... 

VDF-CTFE (chlorotrifluoroethylene) copolymer is a colourless granular material (Figure 3.12) that is commercially available as Kel-F 800 or FK 800 (3M) in... 

Paciorek et al. [20] studied the treatment of Viton-A [poly(VDF-co-HFP) copolymer] and Kel-F [poly(VDF-co-CTFE) copolymer] with different primary, secondary and tertiary mono- and diamines. It appears that Kel-F elastomer required specific crossHnking conditions according to the nature of the (di)amine, at room temperature for primary mono- and diamines, at 50-60 °C for secondary mono- and diamines, at 90-100°C for tertiary diamines, and at 180-190 C for tertiary monoamines. 

Scheme 4 Reaction mechanism between butylamine and a poly(VDF-co-CTFE) copolymer [20]...

As mentioned above, Padorek et al. [22] studied the addition of buty-lamine, dibutylamine and triethylamine on model fluoro-compounds. They also studied the reaction between a Viton-A poly(VDF-co-HFP) copolymer and a Kel-F poly(VDF-co-CTFE) copolymer with monoamines [20], in solution of diglyme, at different times and temperatures, and for different amounts of amines ... 

Poly(VDF-co-CTFE) copolymers are crosslinked more easily in the presence of monoamines than poly(VDF-co-HFP) copolymers are, because HF ehmination should proceed more readily with tertiary fluorine than with the difluoromethylene group [20]. Hence, dehydrofluorination proceeds at a much lower rate with Viton-A than with Kel-F elastomer. 

Different diamines (piperazine, triethylene diamine, and tetramethylethyidiamine), given in Scheme 9 were also used as crosslinking agents for two copolymers poly(VDF-co-HFP) copolymer (Viton A) and poly(VDF-co-CTFE) copolymer (Kel-F) [19,20, 111, 130]. Those curing agents were mixed with both copolymers in a solution of diglyme, at different temperatures and for different reaction times. Results are summarized in Tables 11 and 12 [20]. Kel-F exhibits a gel formation when vulcanized with piperazine at 57 °C... 

Piperazine can crosslink poly(VDF-co-HFP) and poly(VDF-co-CTFE) copolymers at 57 °C in one day, whereas triethylene diamine and tetram-ethylethyldiamine can crosslink poly(VDF-co-CTFE) copolymer at 97 °C in one day. Finally, diethylene triamine crosslinks PVDF at 70 °C in 16 h. 

As two important copolymers of PVDF, the P(VDF-HFP) [4] and P(VDF-CTFE) [23] had been developed for gel polymer electrolyte in LIBs. The introduction of copolymer components was to reduce the crystallinity of the PVDF chain. The reduction of crystallinity could increase the ionic conductivity. Electrospun P(VDF-HFP) and P(VDF-CTFE) fibrous membranes had been proved to show high ionic conductivities in the range of several mS cm which was attributed to the easy transportation of the liquid electrolyte through the fully interconnected pore structure of the membrane. For example, the electrospun P(VDF-HFP) fibrous membrane had high ionic conductivities in the range of 4.59 mS cm", high electrolyte uptake of 425 % at room temperature, and good electrochemical stability with a potential of over 4.5 V versus Li/Li+ [29]. 

Uses. Vinyhdene fluoride is used for the manufacture of PVDF and for copolymerization with many fluorinated monomers. One commercially significant use is the manufacture of high performance fluoroelastomers that include copolymers of VDF with hexafluoropropylene (HFP) (62) or chlorotrifluoroethylene (CTFE) (63) and terpolymers with HEP and tetrafluoroethylene (TEE) (64) (see Elastomers, synthetic-fluorocarbon elastomers). There is intense commercial interest in thermoplastic copolymers of VDE with HEP (65,66), CTEE (67), or TEE (68). Less common are copolymers with trifluoroethene (69), 3,3,3-trifluoro-2-trifluoromethylpropene (70), or hexafluoroacetone (71). Thermoplastic terpolymers of VDE, HEP, and TEE are also of interest as coatings and film. A thermoplastic elastomer that has an elastomeric VDE copolymer chain as backbone and a grafted PVDE side chain has been developed (72). 

Many vinyl monomers were reported to have been grafted onto fluoropolymers, such as (meth)acrylic acid and (meth)acrylates, acrylamide, acrylonitryl, styrene, 4-vinyl pyridine, N-vinyl pyrrolidone, and vinyl acetate. Many fluoropolymers have been used as supports, such as PTFE, copolymers of TFE with HFP, PFAVE, VDF and ethylene, PCTFE, PVDF, polyvinyl fluoride, copolymers ofVDF with HFP, vinyl fluoride and chlorotrifluoroethylene (CTFE). The source of irradiation has been primarily y-rays and electron beams. The grafting can be carried out under either direct irradiation or through the use of preliminary irradiated fluoropolymers. Ordinary radical inhibitors can be added to the reaction mixture to avoid homopolymerization of functional monomers. 

The first commercial fluoroelastomer, Kel-F, was developed by the M. W. Kellog Company in the early to mid-1950s and is a copolymer of vinylidene fluoride (VDF) and chlorotrifluoroethylene (CTFE). Another fluorocarbon elastomer, Viton A, is a copolymer of VDF and hexafluoropropylene (HFP) developed by du Pont was made available commercially in 1955. The products developed thereafter can be divided into two classes VDF-based fluoroelastomers and tetrafluoroethylene (TFE)-based fluoroelastomers (perfluoroelastomers).72 The current products are mostly based on copolymers of VDF and HFP, VDF and MVE, or terpolymers of VDF with HFP and TFE. In the combination of VDF and HFP, the proportion of HFP has to be 19 to 20 mol% or higher to obtain amorphous elastomeric product.73 The ratio of VDF/HFP/TFE has also to be within a certain region to yield elastomers as shown in a triangular diagram (Figure 2.2).74... 

The structure of polyvinylidene fluoride chain, namely, alternating CH2 and CF2 groups, has an effect on its properties which combine some of the best performance characteristics of both polyethylene (-CH2-CH2-)n and polytetrafluoroethylene (-CF2-CF2-)n. Certain commercial grades of PVDF are copolymers of VDF with small amounts (typically less than 6%) of other fluorinated monomers, such as HFP, CTFE, and TFE. These exhibit somewhat different properties than the homopolymer. 

Fluorocarbon elastomers, such as copolymers of VDF and HFP, typically have a maximum continuous service temperature of 215°C (419°F). Some metal oxides may cause dehydrofluorination at a temperature of 150°C (302°F) or even lower.16 Copolymers of VDF and CTFE (e.g., Kel-F ) have a maximum long-term service temperature of 200°C (392°F). Fluorocarbon elastomers based on copolymers of VDF/HPFP (hydropentafluoropropylene) and on terpolymers of VDF/HPFP/TFE have lower thermal stability than copolymers of VDF/HFP because they have a lower fluorine content than the latter.17 A detailed study of thermal stability of fluoroelastomers was performed by Cox et al.18... 

Partially fluorinated fluoropolymers confain hydrogen (H) or other atoms such as chlorine, in addition to fluorine and carbon. The mosf significanf are homopolymers and copolymers of vinylidene fluoride (VDF). There are also copolymers and homopolymers of CTFE, alfhough some have elastomeric properties. Other significant fluoroplastics include ETFE and PVF. 

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