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.     

Modification of poly(vinyl chloride). XIX. Electroplating of poly(vinyl chloride)

As a preliminary treatment in the PVC-electroplating procedure, treatment with dimethylformamide followed by sensitization leads to a finely roughened and a highly hydrophilic surface with reducing power. This is caused by the formation of an ionic complex compound between dimethylformamide and tin(II) chloride absorbed in the PVC surface. A much more finely and deeply etched surface which exhibits higher adhesion through the mechanical interlocking effect is obtained with the PVC blends containing the plasticizer with a low value of interaction parameter and with a solubility parameter approximate to that of PVC. Adhesion of the metal layer to the PVC surface thus obtained is improved about 1.5 times by thermal aging at 120°C for 20 min.     

Miscibility in poly(vinyl chloride)/chlorinated poly(vinyl chloride) blends,and blends of different chlorinated poly(vinyl chlorides)

Blends of poly(vinyl chloride) with chlorinated poly(vinyl chloride) (PVC), and blends of different chlorinated poly(vinyl chlorides) (CPVC) provide an opportunity to examine systematically the effect that small changes in chemical structure have on polymer-polymer miscibility. Phase diagrams of PVC/CPVC blends have been determined for CPVC's containing 62 to 38 percent chlorine. The characteristics of binary blends of CPVC's of different chlorine contents have also been examined using differential calorimetry (DSC) and transmission electron microscopy. Their mutual solubility has been found to be very sensitive to their differences in mole percent CCl₂ groups and degree of chlorination. In metastable binary blends of CPVC's possessing single glass transition temperatures (T_g) the rate of phase separation, as followed by DSC, was found to be relatively slow at temperatures 45 to 65° above the T_g of the blend.     

Degradation of poly(vinyl chloride)

The decomposition of poly(vinyl chloride) below 155°C has been examined by thermogravimetric analysis. Degradation is enhanced by irradiation with 1 MeV electrons. Later stages of isothermal weight loss for thermal and radiolytic decomposition follow 3/2-order kinetics and a similar reaction scheme is inferred. A free radical mechanism for dehydrochlorination involving allyl and polyenyl radicals is postulated.     

Dehydrochlorination of poly(vinyl chloride)

PVC has been dehydrochlorinated with alcoholic alkali in soution at 7°C for different lengths of time. At early stages of dehydrochlorination the dominant reaction is intramolecular removal of HCl and this gives rise to two intense Raman bands at ～ 1126 (ν₁) and ～ 1518 cm^?1 (ν₂) and following UV irradiation, to a quadruplet ESR spectrum. Increasing polyene sequence length and intermolecular removal of HCl at later stages of reaction alters the quadruplet signal to a singlet, shifts ν₁ and ν₂ to lower frequencies and increases the molecular weight. The presence of polyene units stiffens the chain and increases the elastic modulus. The T_g is, however, lowered slightly due to the removal of bulky chlorine atoms which relieves steric hindrance and dipole interaction between neighboring chains. The β-transition is also rendered less distinct.     

Modification of poly(vinyl chloride). XXXIV. Crosslinked poly(vinyl chloride) via paste-processing

A novel PVC-crosslinking technique using 6-dibutylamino-1,3,5-triazine-2,4-dithiol (DB) was applied for a paste processing to produce a crosslinked PVC product. The paste formulation recommended in the present study consisted of 100 parts of PVC (Zeon 121), 60 parts of dioctyl phthalate, 0.2 parts of MgO, and 6 parts of a 50% solution of DB-Na in butylcarbitol, which gave a highly crosslinked and transparent sheet with an excellent stability for thermal discolouring. The increasing viscosity behaviour of the paste during storage is explained by the effect of interparticle attracting forces of DB-Na which coordinates to the ether oxygen atoms in the glycol derivatives adsorbed on the surface of PVC particles. The increased viscosity can be reduced by addition of 3 parts of N-butyl-benzene-sulfonamide. The tension-distortion properties at elevated temperatures were remarkably improved at the crosslinked product compared with the uncrosslinked. The mechanical properties of the two crosslinked products produced via paste processing and roll-blending are compared in regard to the differences of the uniformity of crosslinking units.     

Solubility of vinyl chloride in poly (vinyl chloride) in a water slurry

The solubility of vinyl chloride (VCM) vapor in poly (vinyl chloride) (PVC) in a water slurry has been measured between 55 and 65°C. The heat and entropy of sorption were shown to be very close to those of condensation. The solubilities measured in this study were higher than those obtained in other studies on dry PVC and PVC latex. The interaction parameter (x) in the Flory-Huggins equation has been shown to vary between 0.34 and 0.61 over the composition range studied. The effect of ageing the slurry in the presence of VCM is also discussed.     

The solubility of poly(vinylidene chloride) in solvent mixtures

Effective solvents for poly(vinylidene chloride) (PVDC) were obtained by mixing a polar aprotic solvent with a less polar solvent of cyclic structure. The polar components included sulfoxides, N,N-dialkylamides, and N-alkyl lactams. The cyclic cosolvents included aliphatic and aromatic hydrocarbons, ketones, ethers, and thioethers. The problem of solubility of a crystalline polymer in a mixed solvent was analyzed by extending the Flory theory of melting point depression to three component mixtures. The results predict that favorable mixtures arise when at least one of the components interacts strongly with the polymer but is nearly incompatible with the cosolvent. This is in qualitative agreement with the observed behavior of PVDC.     

Chemically crosslinked poly(vinyl chloride)

The effect of mixing time, temperature, and thermal treatment on mechanical properties of crosslinked PVC is investigated. The tensile properties and gel content of crosslinked and uncrosslinked PVC molded samples are evaluated. The cured samples exhibited higher tensile strength and thermal stability than unmodified PVC.     

Wet poly(vinyl chloride) membrane

Wet, porous, and semipermeable poly(vinyl chloride) (PVC) membrane prepared from a binary system, PVC and dimethylformamide, by immersing in alcohols or ethers was studied. The pore dimensions of the wet PVC membrane were from 0.01 to 0.05 μm, calculated from hydrodynamic permeability by using experimental values such as water flux and water content. They agreed reasonably well with the dimension of the pores which prevented the protein passing through the membrane, observed by SEM photographs. Formation of the wet PVC membrane can be explained by slow phase separation and slow leaching of the casting solution immersed in alcohols and ethers such as methanol and ethylene glycol monomethyl ether.     

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.     

Electrical conductivity in poly(vinyl chloride)

An interpretation by mathematical theory of experimental data already published by the author is given, concerning the electrical conductivity measurement, in direct current, of PVC and plasticizer compositions. The electrical conduction in PVC is due to two mechanisms: one of polarization, which predominates at low temperature, below a transition temperature T₀ and one of ionic conduction which predominates at high temperature above T₀. The mathematical expressions for polarization conductivity k_p and ionic conductivity k₀, agree very well with the experimental data and justify also the great difference in activation energy between the two mechanisms and the independence of activation energy of ionic conductivity from the system viscosity and type of ions.     

Molecular aggregation in poly(vinyl chloride)

Molecular weight distributions and molecular aggregation for poly(vinyl chloride) (PVC) polymerized in bulk at ?10, ?30, and ?50°C have been measured using gel permeation chromatography. The aggregate content in PVC polymerized at ?50°C was found to be 87 wt-%. These spherical aggregates of mean diameter of 5000 A are formed preferentially from PVC chains having high molecular weights and long syndiotactic sequence lengths. A temperature of 200°C was used to disintegrate these aggregates into single PVC molecules. In disagreement with measurements of M _n and M _w published in the literature, our measured values do not reach a minimum but rather increase continuously with decreasing temperature of polymerization. This disagreement is most probably due to the phenomenon of molecular aggregation in PVC.     

Molecular aggregation in poly(vinyl chloride)

PVC synthesized in a bulk polymerization at ?25°C was fractionated by preparative GPC. The eluent THF solutions consist largely of dissociated molecules. Following precipitation into methanol, recovered PVC fractions contain aggregated molecules and are partially insoluble in THF. The soluble portions produce distorted chromatograms characteristic of molecular aggregation. The aggregate fraction increases with molecular weight. Heating recovered PVC fractions at 90°C in THF was adequate to dissociate the aggregates. Following recovery, fractions of PVC do not show crystalline x-ray diffraction patterns. The PVC fractions were crystallizable by subsequent annealing at 150°C to approximately 15% crystallinity, largely independent of molecular weight.     

The influence of poly(vinyl alcohol) suspending agents on suspension poly(vinyl chloride) morphology

The requirements for PVC suspension resin have changed considerably in the last few years, so much so that few companies have products on their ranges that are more than 4 or 5 years old. The suspending agent has a crucial influence on the morphology of the resin, so the changes in resin characteristics have largely been achieved by changes in the suspending agent systems. After a brief review of the mechanism of PVC suspension polymerisation, the properties of polymers made using PVOH suspending agents are related to changes in the latter. The effect of variations in PVAc degree of hydrolysis and viscosity are related to changes in surface tension. Methods of achieving higher porosity by using low hydrolysis co-suspending agents are described. It is shown that higher bulk densities can be achieved by delayed addition of the PVOH. Levels of conjugated unsaturation and copolymer distributions are also shown to have important influences.     

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.