Structural order in heat treated vinyl chloride polymers

Gray, Andrew; Gilbert, Marianne

doi:10.1016/0032-3861(76)90152-x

Cited by 76 publications

(31 citation statements)

References 16 publications

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“…1 Each cell contains two PVC chains arranged in planar zig-zag conformation, with the c direction corresponding to two chemical repeat units. Since lengths of syndiotactic sequences are on average no more than 5-6 repeat units, 2 crystallites in the c direction are very thin, consistent with the model proposed by Summers. 3 X-ray diffraction (XRD) traces for PVC were first published by Mammi and Nardi in 1963.…”

Section: Introductionsupporting

confidence: 86%

X‐ray pole figures to assess orientation in PVC sheets

Gilbert

Ross

Kim

2007

J of Applied Polymer Sci

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A series of X-ray pole figures were obtained from oriented and unoriented rigid polyvinyl chloride sheets. From these, information about crystallite orientation in uniaxially and biaxially drawn sheets stretched at 908C was obtained. Uniaxial orientation produced two crystallite orientations with the extent of orientation increasing with draw ratio; for biaxial samples the chain direction (c) was distributed uniformly in the plane of the sheet, with the planar orientation improving as draw ratio increased.

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Section: Introductionsupporting

confidence: 86%

X‐ray pole figures to assess orientation in PVC sheets

Gilbert

Ross

Kim

2007

J of Applied Polymer Sci

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“…No fUndamentally new DSC results have appeared in the literature since the wo.rk of Illers (61) ; Gray (49,62) recently published the same type of work but focused on the endotherme obtained over Tg' he confirmed that annealing below Tg decreases free volume and increases density but does not change crystallinity (WAXD) ; this was also apparent from Illers who showed that xylene absorption was slowed down but reached the same final value. AnneaLing at 90°C, on the contrary, very much slowed absorption but also diminished the final value.…”

Section: Calorimetrymentioning

confidence: 96%

“…Diffraction by the fringe micelle type has been mentioned in polyethylene and quite recently in isOtactic polystyrene (47). In the case of PVC,the structure observed by Biais could characterize isotactic sequences Sa.H' and not Minimum sequence length of syndiotactic units for the existence of crystallites has been evaluated to be 5 to 1 from WAXD, using the Flory theory for copolymer crystallization (44,49). In order to explain the resistance to long-term creep of plasticized PVC it has been proposed that numerous small crystallites act as crosslinks of the gel network.…”

Section: Order In Solid Pvcmentioning

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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“…Similar results have been reported earlier for noncrosslinked plasticized PVC. 15 As a somewhat lower initial temperature was chosen for the DSC runs given in Figure 5, peak 1 is much more well defined in these cases. The relation between peak 1 and storing (or annealing) at room temperature is illustrated in Figure 6.…”

Section: Resultsmentioning

confidence: 99%

Cooperation between chemical and physical networks in crosslinked and plasticized PVC

Hjertberg¹,

Dahl²

1991

J of Applied Polymer Sci

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SYNOPSISThe effect of crosslinking of plasticized PVC on the mechanical properties has been investigated. Crosslinking was performed by using a dithioltriazine, and penetration as a function of temperature was used to follow the changes in mechanical properties. Changes in the melting behavior were detected by differential scanning calorimetry. Even rather low levels of gel content gave a substantial reduction in penetration in the interval 60-llO"C, while a more complete reaction prevented major penetration up to at least 200°C. The penetration curve of heavily crosslinked materials showed several plateaus and the transitions could be related to melting of different crystallites formed by annealing at different temperatures. The physical network formed by the crystallites constitutes an important complement to the chemical network in plasticized PVC crosslinked by dithioltriazine. Both the amount and the melting temperature of the crystallites increased after annealing. The introduction of the chemical network further improved the heat resistance of the crystallites. The presence of the two networks will therefore show a synergistic effect with respect to the mechanical properties at increased temperatures.

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Structural order in heat treated vinyl chloride polymers

Cited by 76 publications

References 16 publications

X‐ray pole figures to assess orientation in PVC sheets

X‐ray pole figures to assess orientation in PVC sheets

Characterisation of poly(vinylchloride)

Cooperation between chemical and physical networks in crosslinked and plasticized PVC

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