Continuous reactors in free radical polymerization with branching—II experimental results on vinyl acetate polymerization

Nagasubramanian, K.; Graessley, William W.

doi:10.1016/0009-2509(70)85078-3

Cited by 42 publications

(21 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Note that they do not represent a specific chemical system, but the range for the propagation, termination and transfer-to-polymer rate coefficients is close to that for PVAc. [13,14] Regarding LCB generation it should be noted that also terminal double bond propagation leads to LCB. [9] However, to properly deal with these mechanisms, one needs to keep track of the number of terminal double bonds in a molecule, which requires formulating the problem as a two-dimensional distribution system.…”

Section: Cld Modelling With a Cut-off Limitmentioning

confidence: 99%

Molecular-Weight-Distribution Modelling of Radical Polymerization in Batch and Continuous Reactors with Transfer to Polymer Leading to Gel Formation

Iedema¹,

Hoefsloot

2002

Macromol. Theory Simul.

View full text Add to dashboard Cite

Section: Cld Modelling With a Cut-off Limitmentioning

confidence: 99%

Molecular-Weight-Distribution Modelling of Radical Polymerization in Batch and Continuous Reactors with Transfer to Polymer Leading to Gel Formation

Iedema¹,

Hoefsloot

2002

Macromol. Theory Simul.

View full text Add to dashboard Cite

“…For example, short branching may influence protective colloid ability, which can affect the latex viscosity of emulsions polymerized in the presence of PVA,7 and ~r y s t a l l i n i t y ,~.~ which affects tenacity and water resistance of PVA fibres.1° It is to be expected that the extent of branching in PVA will differ with polymerization conditions" and reactor type. 12 McDowell and Kenyon13 were among the first to address the problem of branching in PVAc, by experimentally determining the presence of hydrolyzable branches in PVAc. This was done by comparing degrees of polymerization determined by viscosity measurements.…”

Section: Introductionmentioning

confidence: 99%

Characterization of poly(vinyl alcohol)

Bugada

Rudin

1985

J of Applied Polymer Sci

View full text Add to dashboard Cite

SynopsisMolecular weight distributions, long chain branching frequency, and solution viscosities of samples of commercial poly(viny1 alcohol) (PVA) are reported. The PVA was fully reacetylated to poly(viny1 acetate) (PVAc) for characterizations by size exclusion chromatography using a low angle light scattering detector. The Mark-Houwink constants for PVAc in toluene were determined to be K = 0.106 cm3 g-' and a = 0.59, at 25°C. Long chain branching frequency in the commercial PVAs studied was small and was little affected by polymer molecular weight. Some 95% or more of the branches in these species were short. Aqueous solutions at 10% (w/v) of PVA were Newtonian. The polymers examined differed in chemical composition, molecular weight distributions, and mean block lengths of vinyl acetate residues. Variations in a single characteristic, like a solution or intrinsic viscosity, cannot be used to deduce structural differences between PVAs. INTRODUCTIONThe principal characteristics that determine the physical and technological properties of polymers are chemical composition, molecular weight distribution, and branching character. Poly(viny1 acetate) (PVAc) and its derivative poly(viny1 alcohol) (PVA) are not exceptions. Fine differences in PVA microstructure reflect structural variations in the precursor PVAc and in the reaction system used to convert the PVAc to PVA. These differences are often not reflected in the results of commercial quality control tests, but they can be very important in the performance of PVA as a protective colloid in emulsion and suspension polymerizations..We have earlier' reported on the characterization of the molecular architecture of commercial PVAs. Polymer samples were analyzed by 13C nuclear magnetic resonance spectroscopy and by differential scanning calorimetry to measure tacticity, chemical composition, branch frequency, and mean run lengths of vinyl acetate and alcohol units.Further characterization procedures are reported and discussed in this article. Parameters measured here include molecular weight distribution, long chain branching, intrinsic viscosities, and aqueous solution viscosities and unsaturation in the polymer backbone.Mark-Houwink constants for linear PVAc in toluene are also reported. This report and its predecessor' provide a critical survey of procedures that are thought to give reliable and fairly comprehensive characterizations of the chemical structure of commercial PVAs. EXPERIMENTALSix commercial partially hydrolyzed PVA samples, referred to as A to F inclusive, were used in this study. These materials have been described earlier. ' Acetylation ProcedureThe following reacetylation procedure was used for all of the six partially hydrolyzed PVA samples under investigation. Five grams of the polymer was placed in a round bottom flask. The flask was purged with nitrogen gas for about 10 mins. Fifty milliliters of a 2:l pyridine/acetic anhydride solution were added to the reaction vessel, and the contents were heated on a steam bath at 93-94"C, with stirr...

show abstract

“…The propagation rate constant for the monomer is a recently measured value by PLP for vinyl acetate [42] and the values for ratios of constants relative to transfer to monomer, transfer to polymer, transfer to solvent, and propagation of terminal double bonds were taken from earlier works also dealing with vinyl acetate polymerization. [10,11,13] Termination is supposed to occur with equal probability by combination and by dismutation.…”

Section: Prediction Of Moment Generating Function Of Chain Length Dismentioning

confidence: 99%

“…Initial and feed concentrations of monomer, solvent, and initiator used in the simulations are typical values present in experimental works in this subject [13,16] and are reported in Table 5. Molecular masses of monomer, solvent and initiator fragments were taken as the corresponding values of 86, 73, and 68 for vinyl acetate, t-butanol, and AIBN, respectively.…”

Section: Reaction Name Chemical Equationmentioning

confidence: 99%

“…When the comparison between the simulations obtained with this kind of models with experimental results [13] was carried out, two major difficulties were identified: divergence of the second moment (gelation) was predicted but not observed and it was not possible to simultaneously predict the behavior of batch and CSTR reactors with a unified set of kinetic parameters.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Transient Behavior and Gelation of Free Radical Polymerizations in Continuous Stirred Tank Reactors

Dias

Costa

2005

Macro Theory & Simulations

View full text Add to dashboard Cite

Summary: Using the authors' previously developed method for the general kinetic analysis of non‐linear irreversible polymerizations, the simulation of free radical homogeneous polymerization systems with terminal branching and chain transfer to polymer has been carried out for continuous stirred tank reactors. Its improved accuracy on the numerical evaluation of generating functions has been exploited in order to perform their numerical inversion and chain length distributions could also be estimated with or without the presence of gel. A comparison with alternative techniques emphasizing the effect of their simplifying assumptions on the accuracy of calculations is also presented.Predicted CLD before gelation (t = 1 h), after gelation (t = 15 h, steady state), and close to gel point for a free radical polymerization with transfer to polymer in a CSTR with τ = 60 min.magnified imagePredicted CLD before gelation (t = 1 h), after gelation (t = 15 h, steady state), and close to gel point for a free radical polymerization with transfer to polymer in a CSTR with τ = 60 min.

show abstract

Continuous reactors in free radical polymerization with branching—II experimental results on vinyl acetate polymerization

Cited by 42 publications

References 4 publications

Molecular-Weight-Distribution Modelling of Radical Polymerization in Batch and Continuous Reactors with Transfer to Polymer Leading to Gel Formation

Molecular-Weight-Distribution Modelling of Radical Polymerization in Batch and Continuous Reactors with Transfer to Polymer Leading to Gel Formation

Characterization of poly(vinyl alcohol)

Transient Behavior and Gelation of Free Radical Polymerizations in Continuous Stirred Tank Reactors

Contact Info

Product

Resources

About