Polymer Degradation and Stabilization

Hawkins, W. Lincoln

doi:10.1007/978-3-642-69376-2

Cited by 174 publications

(78 citation statements)

References 5 publications

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“…[11][12][13] Furthermore, the DSC analysis (under the same test conditions) of an atactic polystyrene (PS) revealed no transitions above its T g (in agreement with its u (T) behavior in Figure 1). The results on PS suggest that the observed transitions in polyethylene are a consequence of neither oxidation nor instrument artifacts, but rather a product of a physical phenomenon.…”

Section: Resultssupporting

confidence: 53%

“…The 227°C transition was seen by DSC in all PE resins (except the highly branched metallocene LLDPE resin), regardless of supplier and scan rate and regardless of whether light branching was present in the molecules. Furthermore, these reproducible transitions show a unique "signature" that is totally different from the strong exothermic peaks 2,11,12 associated with oxidative degradation of polyethylene.…”

Section: Resultsmentioning

confidence: 89%

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DSC Evidence for Microstructure and Phase Transitions in Polyethylene Melts at High Temperatures

Hussein

Williams

2000

Macromolecules

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Thermal/microstructural transitions were found at 208 and 227°C in commercial polyethylenes of types HDPE, LDPE, and LLDPE. DSC data were obtained for a range of heating and cooling rates, over a broad high-temperature regime (30-280°C) that spans the melt processing regime. Six samples, from four resin suppliers, were tested; all were of moderate molecular weight (M h w ) (36-85) × 10 3 ). Results are discussed in terms of molecular order and transitions between different degrees of ordering. No transitions were detectable in highly branched metallocene samples. The DSC results are in agreement with our previous rheology findings of order and high-temperature transitions in polyethylene melts.

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Section: Resultssupporting

confidence: 53%

Section: Resultsmentioning

confidence: 89%

DSC Evidence for Microstructure and Phase Transitions in Polyethylene Melts at High Temperatures

Hussein

Williams

2000

Macromolecules

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“…The thermal degradation of polymers is of considerable importance fiom both practical and theoretical points of views (Allen and Edge, 1992) : the degradation of polymers in high-temperature environments can limit their applications (Hawkins, 1984); induced degradation can potentially be used in recycling waste plastics (Powell, 1990; Miller, 1994); thermal degradation by pyrolysis coupled with gas chromatography is an important analytical procedure for identitj?ng polymeric structure (Flynn and Florin, 1985).…”

Section: In Fro Ductionmentioning

confidence: 99%

“…A few experimental and theoretical investigations address the kinetics and mechanisms of polymer degradation (Reich and Stivala, 1971; Hawkins, 1984; Kehlen et al, 1988). These studies involved the determination of the average molecular weight i (MW) of the polymer or the molecular weight distribution (MWD), and the identification of intermediate and final products.…”

Section: In Fro Ductionmentioning

confidence: 99%

Effect of tetralin on polymer degradation in solution. [Quarterly report, January--March 1995]

Madras¹,

Smith²,

McCoy³

1995

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DISCLAIMERPortions of this document may be illegible in electronic image products. Images are produced from the best available original document. AbstractThe effect of a hydrogen-donor solvent (tetralin) on the thermal degradation of poly(styrene-allyl alcohol) in solution was investigated in a steady-state tubular flow reactor at 1000 psig (6.8 MPa), at various tetralin concentrations (0-50 %), polymer concentrations ( 1-4 g/L), and temperatures (1 30-200 C). The molecular weight distributions of the emuent at each condition were examined as a fbnction of residence time by gel permeation chromatography. In the presence of tetralin, the polymer degrades by depolymerization to specific low molecular weight compounds and by random chain scission. No reaction was observed in the solvent 1-butanol in the absence of tetralin. The experimental data were interpreted with a rate expression first-order in polymer concentration based on continuous mixture kinetics, and rate coefficients were determined for the specific and random degradation processes. Activation energies were in the range of 5-10 kcaVmol for specific degradation and 33 kcdmol for the random degradation process. A plot of rate coefficients versus tetralin concentration indicates a fist-order rate at low tetralin concentrations and a zero-order dependence at high tetralin concentrations. In fro ductionThe thermal degradation of polymers is of considerable importance fiom both practical and theoretical points of views (Allen and Edge, 1992) : the degradation of polymers in high-temperature environments can limit their applications (Hawkins, 1984); induced degradation can potentially be used in recycling waste plastics (Powell, 1990; Miller, 1994); thermal degradation by pyrolysis coupled with gas chromatography is an important analytical procedure for identitj?ng polymeric structure (Flynn and Florin, 1985).Thermolytic degradation of polymers is similar in some respects to other important thermal decomposition processes, e.g., petroleum cracking and coal thermolysis. All these processes involve complex mixtures, both as reactants and as products. Simha and Wall (1958) and Jellinek (1955) did some early work on the degradation of polymers by measuring the yield of monomer, rate of decrease of molecular weight, and rate of volatilization. They developed rate expressions using tiee-radical mechanisms. This research was later followed by Madorsky (1964) McGrady, 1985, 1986). The treatment of the general set of equations for initiation, propagation, transfer, and termination reactions can be classified by two approaches: a. b.A statistical theory of random breaking of links (Simha and Wall, 1958; Wall, 1962;Jellinek, 1978) was proposed, and all reactions that form the intermediates and the species were assumed to start From a monodisperse sample (single MW).The desired fbnctions were either obtained by probability considerations of breakage of links, or by the solution of differential rate equations. However, since these theories were derived for a...

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“…It is well established that photooxidation reactions play an important role in the degradation process of ultraviolet (UV) irradiated polymeric materials, and the controlling mechanisms have been studied by some authors [3][4][5]. The physicochemical changes which occur during photooxidative reactions are characterized by an increase in the concentration of the oxygen-containing groups such as peroxides, hydroperoxides, and ketonic carbonyl groups [6].…”

Section: Introductionmentioning

confidence: 99%

A Comparative Study of the Photodegradation of Two Series of Cyclic Olefin Copolymers

Gutiérrez-Villarreal¹,

Zavala-Betancourt²

2017

International Journal of Polymer Science

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A series of commercial cyclic olefin copolymers (COC), namely, ethylene-norbornene (E-NB) and ethylene-tetracyclododecene (E-TD), were processed as thin films with thicknesses of 25 m by an extrusion process. The photodegradation of neat and formulated films with different metal stearates (Fe, Co, and Mn) was investigated using an ultraviolet (UV) light lamp (340 nm) for a period of 30 days in an accelerated weathering tester model QUV from Q-LAB according to the ASTM D 5208-01 standard practice. Changes in carbonyl index (CI) and tensile properties were used to evaluate the photodegradation of the films and other properties, such as variation by DSC, were also analyzed. The present study reveals that (E-NB) copolymers show higher sensitivity to photodegradation than (E-TD) resins, in the absence and presence of metal stearates. We also find that the Fe salt shows the highest oxidative activity.

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Polymer Degradation and Stabilization

Cited by 174 publications

References 5 publications

DSC Evidence for Microstructure and Phase Transitions in Polyethylene Melts at High Temperatures

DSC Evidence for Microstructure and Phase Transitions in Polyethylene Melts at High Temperatures

Effect of tetralin on polymer degradation in solution. [Quarterly report, January--March 1995]

A Comparative Study of the Photodegradation of Two Series of Cyclic Olefin Copolymers

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