Structural aspects of suspension poly(vinyl chloride): relationship between molecular structure and structural order

Scherrenberg, Rolf; Reynaers, Harry; Gondard, C.; Verluyten, Jp

doi:10.1021/ma00068a008

Cited by 16 publications

(11 citation statements)

References 17 publications

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“…Given the critical dimensions required for thermodynamic reasons, however, longer ethylene sequences will still on average crystallize sooner than shorter ones. A comparable situation occurs in PVC, where syndiotactic sequences of unequal length form crystallites -probably of the fringed micelle type -with an orthorhombic unit cell [100,101], the difference being that the lateral dimensions are not limited. This difference is caused by the fact that in the case of PVC the densities of the amorphous and crystalline phases are practically the same, so a crowding problem does not occur.…”

Section: Discussionmentioning

confidence: 99%

Dynamic DSC, SAXS and WAXS on homogeneous ethylene-propylene and ethylene-octene copolymers with high comonomer contents

Mathot

Scherrenberg

Pijpers

et al. 1996

Journal of Thermal Analysis

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Ethylene-propylene (EP) and ethylene-octene (EO) copolymers polymerized with the aid of homogeneous vanadium and metallocene catalysts were compared by DSC and time-resolved simultaneous SAXS-WAXS-DSC at scanning rates of 10 and 20~ rain -1 using synchrotron radiation. An EP eopolymer with a density of 896 kg m -3 (about 89 mol% ethylene) after compression moulding gave orthorhombic WAXS reflections. The crystallinity as a function of temperature [wC(7)] calculated from these reflections using the two-phase model was in good agreement with we(T) calculated from Cp measurements using DSC. The Cp measurements also enabled calculation of the baseline Cp and the excess Cp. The SAXS measurements revealed a strong change in the long period in cooling and in heating. The SAXS invariant as a function of temperature showed a maximum in both cooling and heating, which could be explained from the opposing influences of the crystallinity and the electron density difference between the two phases. Two EO eopolymers with densities of about 871 kg m -3 (about 87 mol% ethylene) no longer showed any clear WAXS reflections, although DSC and SAXS measurements showed that these eopolymers did crystallize. The similarity between the results led to the conclusion that the copolymers, though based on different catalyst systems -vanadium and metallocene -did not have strongly different sets of propagation probabilities of chain growth during polymerization. On the basis of a Monte Carlo simulation model of crystallization and morphology, based on detailed knowledge of the mierochain structure, the difference between WAXS on the one hand and DSC and SAXS on the other could be explained as being due to loosely packed cryz,tallized ethylene sequences in clusters. These do cause the density and the electron density of the cluster to increase (which is measurable by SAXS) and the enthalpy to decrease (which is measurable by DSC) but the clusters are too small and/or too imperfect to give constructive interference in the case of WAXS. Of an EP copolymer with an even lower ethylene content (about 69 mol%), the crystallization and melting processes could still be readily measured by DSC and SAXS, which proves that these techniques are eminently suitable for investigating the crystallization and melting behaviour of the copolymers studied.

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Section: Discussionmentioning

confidence: 99%

Dynamic DSC, SAXS and WAXS on homogeneous ethylene-propylene and ethylene-octene copolymers with high comonomer contents

Mathot

Scherrenberg

Pijpers

et al. 1996

Journal of Thermal Analysis

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“…1,2 However, it has very recently been shown that PVC recovered from concentrated solution in DOP exhibits a higher ordered state than that obtained from solutions in other solvents. The main effect of the plasticizer consists in the reduction of the glass transition temperature T g ͑plasticization effect͒.…”

Section: Introductionmentioning

confidence: 99%

Plasticizer effect on the dynamics of polyvinylchloride studied by dielectric spectroscopy and quasielastic neutron scattering

Zorn

Monkenbusch

Richter

et al. 2006

The Journal of Chemical Physics

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We have studied the influence of plasticization on the microscopic dynamics of a glass-forming polymer. For this purpose we studied polyvinylchloride (PVC) with and without the commercially used plasticizer dioctylphthalate (DOP). We used dielectric spectroscopy and inelastic neutron scattering employing the neutron spin echo (NSE) technique. For both kinds of spectra the alpha relaxation could be consistently described by a model involving a distribution of individual relaxations of the Kohlrausch type. In contrast to earlier studies it turned out that an asymmetric distribution is necessary to fit the data at the lower temperatures investigated here. The shape parameters of the distribution (width, skewness) for PVC and PVC/DOP turned out to coincide when the characteristic relaxation times were the same. This means that the plasticizer only induces a remapping of the temperature dependence of the alpha relaxation. Comparison of NSE spectra S(Q,t)S(Q) at different scattering vectors Q gave the result that the slowing down at the structure factor peak Q(max) is surprisingly small for PVC while it is in the normal range for PVC/DOP.

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“…So, the scattering pattern of PVC is considered as crystalline with an underlying signal provoked by the amorphous phase. Recently, several authors39 have begun realizing that the noncrystalline phase is very important in the explanation of the properties of PVC; analysis40 of the scattering pattern of isotactic chemically modified PVC leads us to think of a wide variety of sizes and perfection of the ordered entities, as well as a lack of order in the chain direction that allows us to conclude that the term crystallinity in the case of nonsyndiotactic PVC has to be used more cautiously. Moreover, Yoon and co‐workers41 have interpreted the scattering pattern of atactic PVC in terms of a noncrystalline order based in interchain orientational correlations with highly parallel segments tending to occur in small localized clusters rather than being homogeneously distributed.…”

Section: Resultsmentioning

confidence: 99%

Interventions for promoting the initiation of breastfeeding

Dyson

McCormick²,

Renfrew³

2006

Evid.‐Based Child Health

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Structural aspects of suspension poly(vinyl chloride): relationship between molecular structure and structural order

Cited by 16 publications

References 17 publications

Dynamic DSC, SAXS and WAXS on homogeneous ethylene-propylene and ethylene-octene copolymers with high comonomer contents

Dynamic DSC, SAXS and WAXS on homogeneous ethylene-propylene and ethylene-octene copolymers with high comonomer contents

Plasticizer effect on the dynamics of polyvinylchloride studied by dielectric spectroscopy and quasielastic neutron scattering

Interventions for promoting the initiation of breastfeeding

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