PVDF, additives

Poly(viaylidene fluoride) [24937-79-9] is the addition polymer of 1,1-difluoroethene [73-38-7], commonly known as vinylidene fluoride and abbreviated VDF or VF2. The formula of the repeat unit in the polymer is —CH2—CF2—. The preferred acronym for the polymer is PVDF, but the abbreviation PVF2 is also frequently used. The history and development of poly(vinyhdene fluoride) technology has been reviewed (1 3). 

The incidence of these defects is best determined by high resolution F nmr (111,112) infrared (113) and laser mass spectrometry (114) are alternative methods. Typical commercial polymers show 3—6 mol % defect content. Polymerization methods have a particularly strong effect on the sequence of these defects. In contrast to suspension polymerized PVDF, emulsion polymerized PVDF forms a higher fraction of head-to-head defects that are not followed by tail-to-tail addition (115,116). Crystallinity and other properties of PVDF or copolymers of VDF are influenced by these defect stmctures (117). 

Materials. For holographic information storage, materials are required which alter their index of refraction locally by spotwise illumination with light. Suitable are photorefractive inorganic crystals, eg, LiNbO, BaTiO, LiTaO, and Bq2 i02Q. Also suitable are photorefractive ferroelectric polymers like poly(vinyhdene fluoride-i o-trifluorethylene) (PVDF/TFE). Preferably transparent polymers are used which contain approximately 10% of monomeric material (so-called photopolymers, photothermoplasts). These polymers additionally contain different initiators, photoinitiators, and photosensitizers. 

The most widely used fluoroelastomers are copolymers of VDF and HFP and optionally also TFE. HFP interrupts the crystallimty of otherwise crystaUme PVDF TFE increases the fluonne content for mcreased solvent and heat resistance without raising the glass transition temperature as much as would an equivalent amount of additional HFP The dipolymer is random except that there are no contiguous HFP units and can therefore be represented as follows... 

Polyarylate (PAR)-b-PSt and PAR-b-PMMA for compatibiiizers are described 135,39,40). The addition of PAR-b-PSt (1-10 parts) to 100 parts of a blend of PAR-PSt (7w-3w) resulted in improvement of the tensile and flexural modulus (Fig. 4), and PSt dispersed particles were diminished from 1-5 microns to an order that is undetectable by SEM, indicating the excellent, compatibilizing effect of the block copolymer. The alloy thus formed exert the characteristic of PAR, an engineering plastic, as well as easy processability of PSt. Addition of PAR-b-PMMA (3 or 8 parts) to 100 parts of a blend of PAR-polyvinylidenefluoride (PVDF) (7w-3w) resulted in improved microdispersed state of PVDF due to compatibility of PMMA with PVDF, while segregation of PVDF onto the surface was controlled. 

For manufacturing of positive electrodes, pastes with the following ratio of the ingredients were applied Lithium cobaltate by Merck or by "Baltiyskaya Manufaktura" (Russia) - 42,5wt%, conductive additive (acethylene soot) - 3,5wt%, PVDF - 4wt%, solvent - the balance. Aluminium foil with the thickness of 0,02 mm was used as a current collector. 

ABS resists hydrolysis well but is naturally sensitive to light and UV the more so as the amount of polybutadiene increases. It must be protected by addition of anti-UV and other protective agents or by a film of UV-resistant polymer such as PVDF. 

Figure 4.16 Melt densities for select resins as a function of temperature. PVC, PMMA, and PVDF resin data are from Zoller and Walsh [43]. All resins contain only extremely low level of additives...

To overcome the poor mechanical properties of polymer and gel polymer type electrolytes, microporous membranes impregnated with gel polymer electrolytes, such as PVdF. PVdF—HFP. and other gelling agents, have been developed as an electrolyte material for lithium batteries.Gel coated and/ or gel-filled separators have some characteristics that may be harder to achieve in the separator-free gel electrolytes. For example, they can offer much better protection against internal shorts when compared to gel electrolytes and can therefore help in reducing the overall thickness of the electrolyte layer. In addition the ability of some separators to shutdown... 

In follow-up work, Kimura et al. (2005) classihed the removal of various pharmaceuticals, by a 0.4-pm PVDF membrane versus conventional activated sludge into three distinct categories (Table 5.5). A few other physical characteristics of those compounds are also included in Table 5.5 to give some additional information that may influence membrane performance. Note that all of the compounds in category 2 in Table 5.5 have Cl ion in their structure. The chloride ion is fairly common in PPCPs (Jjemba, 2006), and chloride-based compounds are usually quite recalcitrant (Eker and Kargi, 2006). 

PVC, another widely used polymer for wire and cable insulation, crosslinks under irradiation in an inert atmosphere. When irradiated in air, scission predominates.To make cross-linking dominant, multifunctional monomers, such as trifunctional acrylates and methacrylates, must be added. Fluoropolymers, such as copol5miers of ethylene and tetrafluoroethylene (ETFE), or polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), are widely used in wire and cable insulations. They are relatively easy to process and have excellent chemical and thermal resistance, but tend to creep, crack, and possess low mechanical stress at temperatures near their melting points. Radiation has been found to improve their mechanical properties and crack resistance. Ethylene propylene rubber (EPR) has also been used for wire and cable insulation. When blended with thermoplastic polyefins, such as low density polyethylene (LDPE), its processibility improves significantly. The typical addition of LDPE is 10%. Ethylene propylene copolymers and terpolymers with high PE content can be cross-linked by irradiation. ... 

A composition containing at least 70 wt % of PVDF and about 30 wt % of acrylic resin has been recommended as a standard coating formulation. The recommended formulation is designed to provide coatings with optimized physical properties and a resistance to the effects of long-term environmental exposure. In addition to internal research results, a literature search was done to confirm that this composition provides the best balance of optical properties, solvent resistance, hardness, mechanical strength, and weatherability. 

For PVDF/PMMA blends prepared by a melt process without additional thermal treatment, the melting point of crystalline PVDF cannot be observed for... 

In addition to quantitative estimates of material properties, molecular modeling can offer valuable qualitative insights into the dynamical properties of materials, without resorting to direct simulation (e.g., molecular dynamics), where the rigorous treatment of all the dynamics at the atomic scale would be prohibitively time-consuming. To illustrate this point, the second part of this chapter describes recent studies of the relaxation in the crystalline a-phase of PVDF. Molecular modeling provides a way to characterize the mechanism of... 

Coleman et al. 2471 reported the spectra of different proportions of poly(vinylidene fluoride) PVDF and atactic poly(methyl methacrylate) PMMA. At a level of 75/25 PVDF/PMMA the blend is incompatible and the spectra of the blend can be synthesized by addition of the spectra of the pure components in the appropriate amounts. On the other hand, a blend composition of 39 61 had an infrared spectrum which could not be approximated by absorbance addition of the two pure spectra. A carbonyl band at 1718cm-1 was observed and indicates a distinct interaction involving the carbonyl groups. The spectra of the PVDF shows that a conformational change has been induced in the compatible blend but only a fraction of the PVDF is involved in the conformational change. Allara M9 250 251) cautioned that some of these spectroscopic effects in polymer blends may arise from dispersion effects in the difference spectra rather than chemical effects. Refractive index differences between the pure component and the blend can alter the band shapes and lead to frequency shifts to lower frequencies and in general the frequency shifts are to lower frequencies. 

Approximate conformational energy estimates are utilized to evaluate the RIS model of PVDF, Occasional 10-20%) head to head tail to tail (H-H T-T) addition of monomer units in a random fashion is accounted for In the calculation of these conformational properties. In general it is found that the calculated conformational properties are relatively insensitive to the amount of H-H T-T addition assumed, but are instead markedly dependent upon the value of the dielectric constant Is) selected to mediate the electrostatic interactions encountered along a PVDF chain. 

The durability of E-CTFE is questionable based on these test results. Embrittlement of the E-CTFE coupon at elevated temperatures was severe however, additional changes in hardness or physical appearance were not observed. The Increase in hardness of the PVDF coupons at both ambient and elevated temperatures (Table 4) is relatively insignificant in comparison with the uncertainty associated with the hardness measurements. Therefore, there is no clear evidence that PVDF is Inadequate for mixed-acid streams. The PTFE, ETFE, PFA, and FEP materials appear to be resistant to the corrosive acids used in the tests. 

PVDF membranes bind proteins primarily through hydrophobic interactions and are commonly used for their chemical resistance as well as physical stability. High-affinity PVDF membranes such as Trans-Blot (Bio-Rad), ProBlott (Perkin-Elmer), and Immobilon-PSQ (Mil-lipore) are preferred for blots intended for use in N-terminal protein sequencing, whereas low-retention membranes such as Immobilon-P (Millipore) may produce lower background in both immunoblotting and common staining procedures. In addition, low-retention membranes are preferred when proteins will be extracted from the membrane. 

Another problem often encountered with poor transfer of proteins relates to the amount of SDS in the gel, which coats the proteins and improves mobility during electrotransfer. Nitrocellulose membranes are not sensitive to the amount of SDS in the gel and can even tolerate addition of SDS to the transfer buffer to encourage transfer of recalcitrant proteins. PVDF membranes are more sensitive to excess SDS, which can inhibit protein binding to the hydro-phobic membrane nevertheless, in a limited number of cases, addition of SDS to the transfer buffer may be beneficial. Low-retention PVDF membranes are particularly sensitive to excess SDS concentrations, whereas high-retention PVDF membranes are less so. Methanol is a common component of many transfer buffers because it facilitates dissociation of bound SDS from proteins. Therefore, if proteins transfer from the gel efficiently but do not bind well to PVDF membranes, the methanol concentration can be increased to 20% and/or the gel can be preequilibrated in transfer buffer for 15 to 30 min prior to transfer to reduce the SDS concen-... 

An additional visualization technique for PVDF membranes is transillumination, described by Reig and Klein (1988). In that technique, the membrane is dried at room temperature, then wet with 20% methanol and viewed on a white light box. Protein bands appear as clear areas. Sensitivity is usually comparable to that of Coomassie blue staining. 

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