Dilute solution properties and molecular characterization of polyvinyl chloride

Vries, A. J. de; Bonnebat, C.; Carrega, Marc

doi:10.1351/pac197126020209

Cited by 63 publications

(7 citation statements)

References 5 publications

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“…Cyclohexanone is most often used for viscosity measurements on PVC polymer 50,51 . However, THF, has been the most appropriate solvent, 52,53 as it avoids the presence of aggregates (non‐soluble portion of PVC). The solubility parameter, δ, of PVC is about 19.4 MPa 1/2 , and is therefore resistant to non‐polar solvents that have a lower solubility parameter.…”

Section: Resultsmentioning

confidence: 99%

“…Although it is not an absolute experiment, since viscosity depends on a series of other molar properties besides mass, viscosimetric experiments show the existence of a relationship between molecular size and viscosity of macromolecular solutions. In a plot of inherent viscosity, η inh , or reduced viscosity, η red , against solution concentration, extrapolating to a concentration equals to zero, the intrinsic viscosity, [ η ], is obtained, which is further used to calculate the viscosimetric‐average molar mass,

{\bar{M}}_{v}

, with the Mark‐Houwink‐Sakurada equation:

([], η) = K {({\overset{false¯}{M}}_{v})}^{a}

where [ η ] is the intrinsic viscosity or limiting viscosity number, and K and a are constants that depends of the polymer‐solvent system and temperature of the measurement 52 …”

Section: Resultsmentioning

confidence: 99%

“…where [η] is the intrinsic viscosity or limiting viscosity number, and K and a are constants that depends of the polymer-solvent system and temperature of the measurement. 52 Table 2 shows the PVC solutions and their concentrations, the flow time [t(s)] of each solution (t 0 for pure solvent was 7.93 s), and the results of the different viscosities obtained, including the inherent viscosity of each solution. Statistical treatment was performed considering a 95% confidence interval.…”

Section: Viscosimetric Analysismentioning

confidence: 99%

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Thermal dehydrochlorination of pure PVC polymer: Part I—thermal degradation kinetics by thermogravimetric analysis

Cruz

Silva

Fiuza-Jr

et al. 2021

J of Applied Polymer Sci

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Thermal degradation of PVC occurs in two stages, with each stage subdivided into two substages. The first refers to the dehydrochlorination, where hydrochloric acid is formed, and giving polyene structures. Hitherto, the degradation mechanism and action of hydrochloric acid as a catalyst during the dehydrochlorination stage are poorly known. Recently, the importance of the tacticity has gained attention for its influence on the dehydrochlorination mechanism. The present work focused on the dehydrochlorination stage, studying the molecular structure by FTIR analysis and the kinetic parameters by TGA analysis in Nitrogen atmosphere, based on three mathematical methods: Friedman, Kissinger, and Flynn-Wall-Ozawa. The sample was a pure homopolymer obtained by suspension polymerization. The dehydrochlorination kinetics follows a first order reaction model and occurs by nucleation and growth. The dehydrochlorination begins with the loss of very labile chlorine atoms present in defective and isotactic molecular segments. The formed HCl acts as a catalyst in the degradation. Following 40% conversion, a drop in Ea is observed. After that, chlorine atoms present in syndiotactic and atactic sequences, are released and, added to the large number of polyene chain sequences, and an increase in Ea is observed up to 60% conversion, where the dehydrochlorination stage is concluded.

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Section: Resultsmentioning

confidence: 99%

{\bar{M}}_{v}

, with the Mark‐Houwink‐Sakurada equation:

([], η) = K {({\overset{false¯}{M}}_{v})}^{a}

where [ η ] is the intrinsic viscosity or limiting viscosity number, and K and a are constants that depends of the polymer‐solvent system and temperature of the measurement 52 …”

Section: Resultsmentioning

confidence: 99%

Section: Viscosimetric Analysismentioning

confidence: 99%

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Thermal dehydrochlorination of pure PVC polymer: Part I—thermal degradation kinetics by thermogravimetric analysis

Cruz

Silva

Fiuza-Jr

et al. 2021

J of Applied Polymer Sci

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“…De Vries (1) showed that tetrahydrofuran (THF) solution of PVC fractions in the molecular weight range 6400 -650 000 g/mole obeyed the following Mark-Houwink relation :…”

Section: Structure Of the Pvc Chain Long Branchesmentioning

confidence: 99%

Characterisation of poly(vinylchloride)

Carrega¹

1977

Pure and Applied Chemistry

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-0.5 10-3 .r;O~g branch and 5 10-3 chloromethyl group permonomer uni t (m.u.) possibly originating from head-to-head monomer placement are f.ound in industrial PVC (fewer in low-temperature polymerized products). TertiarY chlorine atoms, if any, correspond to long branches ; internal double bonds (0.05 10-3 per m.u. and over) can start polydiene sequences. 1 H and 1 3c NMR spectroscopy shows that syndiotactic placement is slightly favored over isotactic, depending only on polymerization temperature (PT). The number of aggregates in solution is very sensitive to PT,increasing with syndiotacticity, and heating up gives molecular solutions. Crystallizability increases with syndiotacticity, and two types of crystals exist ;. crystallinity is higher in virgin powder, and fusion range covers 120o to 220°C • .Annealing over 110°C develops a lower order detectable by DSC. A zone of higher density disappearing at 210°C is seen at the center of virgin PVC "one micron granules"• The temperature of pseudofusion in plasticizers depends on heat treatment, and the kinetics of impregnation reveals morphological heterogeneities.

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“…The degree of tacticity of samples prepared between 25 and 60°C varies only slightly and is close to 0 .53 (3, 4 ) . The branching structure of PVC can be described as consisting of very few, if any, long branches (5,6), and a few short branches-probably less than 10 short branches per 1000 repetition units. For this molecular structure, one would certainly expect that the melt flow behavior would be describable by theories for the melt flow of linear molecules.…”

Section: Introductionmentioning

confidence: 99%

Melting of crystallites in polymers with low degree of crystallinity under shear flow conditions I: Poly(vinyl chloride)

Lyngaae-Jørgensen

1974

Polymer Engineering & Sci

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The aggregates found in dilute solutions of nearly atactic PVC have been shown to consist of 10 to 15 single molecules held together by a crystalline nucleus. Based on the postulate that the last crystallites in a PVC melt have the same structure as found in dilute solution, a relation between the melting temperature in shear (Tdyn), the static melting temperature (Tm) and the shear stress (τ) is found: where Q is a constant. The model predictions are in accordance with data from a Brabender rheometer and a Rheometrics mechanical spectrometer. Q is found to be a constant for samples with weight average molecular weights in the interval between 70,000 and 160,000 corresponding to polymerization temperatures between 40 and 70°C.

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Dilute solution properties and molecular characterization of polyvinyl chloride

Cited by 63 publications

References 5 publications

Thermal dehydrochlorination of pure PVC polymer: Part I—thermal degradation kinetics by thermogravimetric analysis

Thermal dehydrochlorination of pure PVC polymer: Part I—thermal degradation kinetics by thermogravimetric analysis

Characterisation of poly(vinylchloride)

Melting of crystallites in polymers with low degree of crystallinity under shear flow conditions I: Poly(vinyl chloride)

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