Interpretation of the enhanced solubility of poly(vinylidene chloride) in certain solvent mixtures

The 3-component mixture poly(vinylidene chloride)—tetramethylene sulfoxide–tetrahydrophalene has been investigated by viscometric methods. This solvent pair shows an unusal affinity for the polymer. This can be attributed to the strong polar interaction between the acidic polymer and the basic sulfoxide which is enhanced by the presence of the nonpolar diluent.     

The solubility of poly(vinylidene chloride)

The relative abilities of various solvents to dissolve crystalline polyvinylidene chloride were judged by comparing temperatures at which dilute suspensions became homogeneous. PVDC is not soluble in common solvents at ambient temperatures. It dissolves in solvents of matching solubility parameter only above ～130°C. An analysis of the data suggests that δ = 10.1 for PVDC. Five classes of specific solvents were observed that could dissolve PVDC at much lower temperatures. These include sulfoxides, dialkyl amides, alkyl lactams, cyclic sulfides, and cyclic ketones. PVDC acts as a weak Lewis acid in these solutions. The best solvents found, in order of decreasing activity, are: hexamethylphosphoramide, tetramethylene sulfoxide, N-acetylpiperidine, N-methylpyrrolidone, N-formylhexamethyleneimine, and trimethylene sulfide.     

Effect of recrystallization on the solubility of poly(vinylidene chloride)

A study of the crystallization of poly(vinylidene chloride) from dilute solution in various solvents was carried out. The temperature at which the polymer dissolved was dependent on crystallization history. The minimum solution temperature obtained by recrystallization at high undercooling and redissolving is the preferred parameter for characterizing solvents for poly(vinylidene chloride).     

The solubility of vinyl chloride in poly(vinyl chloride)

The solubility of vinyl chloride monomer (VCM) in PVC powders has been studied by equilibrium vapor pressure and microbalance gravimetric techniques at temperatures from 30 to 110°C. At temperatures and VCM concentrations above the glass transition, the solubility closely follows the Flory-Huggins equation with χ = 0.98 and is independent of temperature and of the PVC type, molecular weight, or history. In the glassy state, the VCM solubility is higher than the Flory-Huggins value and shows pronounced dependence upon time and the PVC history. These results have been interpreted through the dual-mode sorption concept of Michaels, Vieth, and Barrie: Normal dissolution follows the Flory-Huggins relation, and the additional glassy-state solubility represents the contribution of a hole-filling process. Changes in solubility with time and sample history parallel well-known volume relaxation processes, indicating that vapor solubility measurements offer a direct and sensitive measure of the free-volume state of glassy polymers.     

Modification of pitches by poly (vinylidene chloride) and poly (vinyl chloride)

Poly(vinylidene chloride) — PVDC — and poly(vinyl chloride) — PVC — reacted with pitches at elevated temperature with an increase in the yield of residual carbon; the greater the aromaticity and ‘fixed carbon’ of the pitch, the greater the increase. PVDC especially had a remarkable effect. This increase of residual carbon may be due to an increase in the molecular weight of pitch produced by its reaction with PVDC or PVC via dehydrochlorination. This tends to elevate the softening point and increase the insolubility in solvents. It is clearly indicated from i.r. spectra that reaction takes place mainly between aromatic hydrogen in the pitch and chlorine in PVDC. X-ray diffraction profiles of the reaction products show that the pitch forms hard (non-graphitizing) carbon as the PVDC content in the mixture increases.     

The thermal decomposition of poly(vinylidene chloride) in the solid state

The rate of decomposition of PVDC is sensitive to differences in the method of preparation of the polymer. Polymers prepared by mass polymerization of very pure monomer were most stable. Emulsion polymerized PVDC degraded the fastest. The activation energy for the latter was 34.4 kcal/mole. Over the range of 130°–190°C, the rate of decomposition increases with reaction time to ～10% HCl evolved. Beyond this point, the reaction follows first-order kinetics. The first-order rate is independent of molecular weight. Lamellar crystals of PVDC degrade at a higher rate than “as polymerized” powders. This may be due in part to annealing of the crystals in the degradation temperature range; but it also results from a sensitization of the polymer to thermal degradation from exposure to the polar solvents used for recrystallization. A mechanism is proposed to account for these observations.     

Constant voltage electrodeposition of poly(vinylidene chloride) emulsions

In the field of organic coatings, electrodeposition is a technique that holds many advantages over traditional methods of immersion and dispersion, such as low levels of contamination, ease of control and automatization, and high penetration capacity. In this article, the results of the electrodeposition of poly(vinylidene chloride) emulsions on galvanized steel are presented. The operating conditions to form thin, uniform, and adherent films were established. A mathematical model was also developed to predict film growth with time as a function of the process parameters. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2479–2486, 1998     

Polymer compatibility: Ternary blends of poly(vinylidene chloride-co-vinyl chloride), poly(vinyl chloride) and poly(acrylonitrile-co-butadiene)

Mixtures of two compatible polymers, poly(vinyl chloride) and poly(acrylonitrile-co-butadiene) containing 40 percent acrylonitrile, can be compatible with poly(vinylidene chloride-co-vinyl chloride), which is incompatible and partially compatible respectively with these two polymers. The crystalline melting temperature and relative heat of fusion of poly(vinylidene chloride-co-vinyl chloride) in blends are higher than those in the pure component. This is attributed to greater ordering of the polymer chains in the crystalline phases of the blends. Replacing the rubber by poly(acrylonitrile-cobutadiene) containing 30 percent acrylonitrile, shows that these three polymers, in which each pair is incompatible or at most partially compatible, also form compatible ternary blends. The crystalline melting temperature is higher and relative heat of fusion lower than those in the pure component. This is attributed to dissolving of parts of the polymer chains originally located in the crystalline phases in the amorphous phases of the blends.     

Effect of compatibility between solvent and poly(vinyl chloride) on dechlorination of poly(vinyl chloride)

In this study, the use of diethylene glycol (DEG), triethylene glycol (TEG), n-C₁₀H₂₁OH, and ethylene glycol (EG) as solvents for NaOH in the dechlorination of poly(vinyl chloride) (PVC) was investigated. In the early reaction time, the degrees of dechlorination for DEG, TEG, and n-C₁₀H₂₁OH were notably higher than that for EG. Further, the high compatibility between PVC and the solvents was considered to result in the easy penetration of the solvent and OH⁻ into PVC particles, leading to the acceleration of dechlorination in the early reaction stage. An improvement of the dechlorination was actually observed for DEG and TEG compared with EG. The solvent with the best compatibility to PVC, n-C₁₀H₂₁OH, however, showed little improvement due to the formation of a protective polyene layer on the surface of the PVC particles.     

Model systems for the study of poly(vinylidene chloride) degradation

Poly(vinylidene chloride) and copolymers which contain vinylidene chloride (VDC) as a major component undergo thermal degradative dehydrochlorination. Previous work has demonstrated that random double bonds introduced during polymerization/processing serve as the principal defect sites responsible for initiation of the dehydrochlorination reaction. However, residues from degradation of polymers of relatively high molecular weight tend to be crosslinked and relatively insoluble in most solvents. This prohibits the examination by instrumental techniques of these “products” of the degradation reaction. Low-molecular-weight model compounds prepared from appropriate multifunctional ketones or by telomerization of VDC monomer in carbon tetrachloride provide materials which upon degradation afford soluble residues which may be characterized by nmr spectroscopy. Initial results suggest that depolymerization/fragmentation can be a major degradation process for these materials.     

Synthesis and characterization of polyurethane/poly(vinylidene chloride) interpenetrating polymer networks

A series of polyurethane (PU)/poly(vinylidene chloride) (PVDC) interpenetrating polymer networks (IPNs) were synthesized through variations in the amounts of the prepolyurethane and vinylidene chloride monomer via sequential polymerization (80/20, 60/40, 50/50, 40/60, 30/70, and 20/80 PU/PVDC). The physicomechanical and optical properties of the IPNs were investigated. Thermogravimetric analysis (TGA) studies of the IPNs were performed to establish their thermal stability. TGA thermograms showed that the thermal degradation of the IPNs proceeded in three steps. Microcrystalline parameters, such as the crystal size and lattice disorder, of the PU/PVDC IPNs were estimated with wide‐angle X‐ray scattering. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1375–1381, 2007     

Chlorinated poly(vinylidene fluoride)

Chlorinated poly(vinylidene fluoride) (PVF₂) was prepared by introducing chlorine gas into a CCI₄ suspension of PVF₂ at reflux temperature. Polymer crystallinity and softening point decrease, while solubility and adhesion increase with the degree of chlorination. In contrast to PVF₂, the chlorinated polymer is soluble in low-boiling common organic solvents, such as acetone, methyl ethyl ketone, and 1,2-dimethoxyethane. Chlorinated PVF₂ is resistant to dehydrochlorination and is thermally more stable than PVF, chlorinated PVF, PVC, or chlorinated PVC. Chlorinated PVF₂ coatings on wood, prepared by solution casting at room temperature, show outstanding weathering resistance.     

The effect of solvent traces on the ultraviolet degradation of poly(vinyl chloride)

The ultraviolet degradation of poly(vinyl chloride) films was studied in a photoreactor which supplied energy near 3000 Å. It was noted that the rate of degradation and color development was increased when the level of residual solvent in the cast films was increased. Two solvents were employed in the study: tetrahydrofuran and dichloroethane. The amount of residual solvent was correlated with the height of a characteristic peak at 2800 Å for tetrahydrofuran and 1900 Å for dichloroethane. Films which had very small traces of solvent showed excellent resistance to ultraviolet degradation, even in the absence of ultraviolet stabilizers. The analysis of solubility data showed that chain scission was controlling in the early stages of exposure, while crosslinking was controlling at later stages. As a result, it was not possible to apply Charlesby's treatment of radiation-induced degradation. Comparison with the results obtained by other workers for degradation at 2537 Å showed that degradation at this wavelength was much faster than degradation at 3000 Å. Furthermore, degradation at 2537 Å appeared to be controlled by crosslinking at all stages of exposure.     

Properties of poly(vinylidene fluoride)

The properties of fluorocarbon plastics have made them desirable for numerous new applications. Poly(vinylidene fluoride) (PVF₂) can be easily extruded into films or fibers or injection molded into a variety of shapes. It was found that crystallinity, molecular weight distribution and polymer structure are important in establishing resin properties. Highly crystalline PVF₂ with a narrow Gaussian molecular weight distribution gives specimens with optimum physical and chemical properties.     

Effect of solvent on thermal transitions and conductivity of poly (vinylidene fluoride) gel electrolytes

ABSTRACT

The melting (T_m) and crystallization (T_c) temperature increased with increasing solvent phenyl propanol (PhP) concentration in the mixture of solvent propylene carbonate and phenyl propanol (PC/PhP). It is also a little enhances of Tm and Tc with adding ethylene carbonate (EC) to propylene carbonate (PC). The melting (T_m) and softening temperature (T_soft) follows the following order of solvents PC<EC:PC<PhP:PC. There was a small change of modulus was observed with the addition of PhP. The conductivity falls with increasing PhP concentration and viscosity and re-calculate free ion concentration. The adding EC to PC raises temperatures slightly, but conductivity much the same. The overall, adding poorer solvent PhP increases the melting and crystallization temperatures at the expense of conductivity, but a little changes was observed in storage modulus, much better gel network, thereby securing the continuity of the complex leads to more flexible ductile and crystalline phase serves better mechanical properties. The crystallinity of PVDF gel electrolyte is about 50%, which facilitate to changes gel network structure slightly with PhP concentration. The formation of fully interconnected three dimensional frame work structure uniformly distributed pores with large surface area can function as efficient channels for ion conduction.     

Tensile yield in poly(chlorotrifluoroethylene) and poly(vinylidene fluoride)

Uniaxial tension tests to the yield point were performed on poly(chlorotrifluoroethylene) (PCTFE) and poly(vinylidene fluoride) (PVF2) from room temperature to near the melting point at a strain rate of 2 min^?1. At room temperature and at least two elevated temperatures, measurements were also made at strain rates from 0.02 to 8 min^?1. The properties of these polymers were found to be similar to those of other semicrystalline polymers. In the absence of other transitions, yield energy was found to be a linear function of temperature extrapolating to zero near the melting temperature. The ratio of thermal to mechanical energy to produce yielding is smaller than for glassy polymers. Yield stress is a linear function of log strain rate. The ratio of yield stress to (initial) Young's modulus is about 0.03 at room temperature for both polymers. Yield stress is a linear function of unstrained volume. Yield strain, elastic, and plastic strain all initially increase with temperature, but PCTFE shows a decrease with temperature starting at about 100°C, thus behaving like a glassy amorphous polymer in this region.     

Prediction of gas solubility in binary polymer+solvent mixtures

This paper is devoted to a theory of gas solubility in highly asymmetrical mixed solvents composed of a low molecular weight (such as water, alcohol, etc.) and a high molecular weight (such as polymer, protein, etc.) cosolvents. The experimental solubilities of Ar, CH₄, C₂H₆ and C₃H₈ in aqueous solutions of polypropylene glycol and polyethylene glycol were selected for comparison with the theory. The approach for predicting these solubilities is based on the Kirkwood-Buff formalism for ternary mixtures, which allowed one to derive a rigorous expression for the Henry constant in mixed solvents. Starting from this expression, the solubilities could be predicted in terms of those in each of the two constituents and the properties of the mixed solvent. This expression combined with the Flory-Huggins equation for the activity coefficient in a binary mixed solvent provided very accurate results, when the Flory-Huggins interaction parameter was used as an adjustable quantity. A simple expression in which the solubility could be predicted in terms of those in each of the two constituents and the molar volumes of the latter was also derived. While less accurate that the previous expression, it provided more than satisfactory results.     

The crystalline morphology of poly(vinylidene fluoride)/poly(methylmethacrylate) blends

Poly(vinylidene fluoride), PVF₂, as well as blends of PVF₂ with poly(methyl methacrylate), PMMA, develop a variety of crystalline morphologies at low undercoolings. Both the α and γ crystal forms grow from the melt and the former undergoes a solid-solid phase transition to the latter, though its morphology remains unaltered. Three melting temperatures which decrease with increasing PMMA content are observed. Hoffman-Weeks analysis shows the equilibrium melting points of the blends to be depressed. Using these equilibrium values, the thermodynamic interaction energy density is calculated to go from ?5.40 × 10⁶ to ?2.96 × 10⁷ j/m³ as the blend composition goes from 40.1 volume percent to pure PVF₂. The band periodicity in the α form spherulites increases with crystallization temperature and PMMA content and it appears to be from a lamellar reorientation process with an apparent activation energy of 322 cal/mole. Electron diffraction patterns taken along the radial direction in a given spherulite reveal lamellar twisting which causes the banded appearance. Light scattering results suggest that the lamellar are formed into rod-like structures on a local scale but that on a larger scale they develop a disoriented spherulitic morphology.