Determination of the number and the nature of the end groups of poly(vinyl chloride)

Carrega, Marc; Bonnebat, C.; Zednik, Georges.

doi:10.1021/ac50160a058

Cited by 26 publications

(6 citation statements)

References 7 publications

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“…Secondary C -C bonds were not cut since the nurober average degree of polymerization DPn was approximately preserved (5,6). If tertiary C -C bonds were cut it would diminish DP and the weight average degree DP by a factor of approxin w mately two in the case of only one long branch per chain, and this was not found to be the case.…”

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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Section: Structure Of the Pvc Chain Long Branchesmentioning

confidence: 99%

Characterisation of poly(vinylchloride)

Carrega¹

1977

Pure and Applied Chemistry

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“…Baum and Wartman3* found from ozonolysis experiments that 6096 of the molecules have double bonds at the end of the chain. In a more recent investigation Carrega et al 30 determined the difference in methyl content after hydrogenation by LiAlH4 and a following reduction by Raney Nickel. The latter reagent was supposed to reduce even the chloro-containing double bonds at chain ends.…”

Section: Branchingmentioning

confidence: 99%

On the thermal degradation of poly(vinyl chloride). III. Structural changes during degradation in nitrogen

Abbås

Sörvik

1975

J of Applied Polymer Sci

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SynopsisThe structural changes in poly(viny1 chloride) during thermal degradation in nitrogen at 190OC have been investigated. From gel permeation chromatography analyses no chain scission, but only crosslinking reactions were observed. An increase in the molecular weight was measured even a t 0.3% conversion. For longer polyene sequences and at higher conversions, a crosslinking reaction competed with the "zipper" propagation. The secondary reactions were more extensive at longer polyene sequence lengths. The growing polyene sequences can be terminated not only by branching reactions but also at existing pendent chloromethylene groups. A decrease in the amount of short chain branching with conversion also indicated other types of secondary reactions. Such a decrease was also observed during thermomechanical degradation in a Brabender Plastograph. The average polyene sequence length was calculated to be around LO, depending somewhat on the type of analysis used. Although allylic chlorine atoms seem to be the main points of initiation, other sites cannot be excluded as the number of initiation points increases appreciably during the early stages of the degradation. Such an increase is, of course, also consistent with a radical mechanism.

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“…134 In UV degradation studies it was found that the technique was insensitive and erroneous conclusions have been easily drawn. Starnes et al [182][183][184] gave a detailed description of NMR spectroscopy potential, and Abbas 185 made measurements using Starnes' method. It was used to predict color with very good results because both NIR and color determination measure changes caused by formation of polyenes.…”

Section: Laser Photopyroelectric Effect Spectrometrymentioning

confidence: 99%

“…Starnes et al, [182][183][184] who experimented with various reducing agents, made excellent use of the full capabilities of this method by utilizing Bu 3 SnD as a reducing moiety. Monodeuteration of 13 C atom converts its proton-decoupled NMR signal from a singlet into a triplet, due to which this signal and those from neighboring carbon undergo upfield shifts.…”

Section: Laser Photopyroelectric Effect Spectrometrymentioning

confidence: 99%

Analytical Methods

Wypych¹

2015

PVC Degradation and Stabilization

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Determination of the number and the nature of the end groups of poly(vinyl chloride)

Cited by 26 publications

References 7 publications

Characterisation of poly(vinylchloride)

Characterisation of poly(vinylchloride)

On the thermal degradation of poly(vinyl chloride). III. Structural changes during degradation in nitrogen

Analytical Methods

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