The relationship between rate of reaction with oxygen and chemical change in polymers as indicated by I.R. analysis

Chan, M. G.; Hawkins, Walter

doi:10.1002/pen.760070407

Cited by 14 publications

(1 citation statement)

References 8 publications

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“…Such considerations make the NMR analysis an ideal technique when both quantitative measurements and identification information are required. Complementing the NMR measurements are infrared determinations which are particularly sensitive to C-0 bonds and thus afford high sensitivity for assessment of the oxidation products in solid polyethylene.12, 13 The IR results provide excellent corroboration of the NMR data. Examples of IR spectra of the oxidized polyethylene samples are shown in Figure 5.…”

Section: Resultsmentioning

confidence: 91%

Thermal oxidation and its analysis at low levels in polyethylene

Jelinski¹,

Dumais²,

Luongo³

et al. 1984

Macromolecules

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Water causes electrical breakdown and erosion processes to occur in polyethylene dielectric material at voltages lower than in the dry polymer. It has recently been shown that solubility and diffusion of water in branched polyethylene are related to the degree of oxidation of the polymer. This report concerns (1) the chemical identification and quantification of the sites of oxidation in polyethylene that has been thermally oxidized at low levels (0.6-1.9% oxygen) and (2) assessment of the motional nature of water in oxidized polyethylene. Carbon-13 NMR is shown to be an effective spectroscopic technique that can identify oxidation products at the 0.05% level. Ketones, secondary alcohols, secondary hydroperoxides, and carboxylic acids are found as the major oxygen-containing groups. The striking differences in the distribution of these species that are found between linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE) are attributed to differences in thermal treatment and branch patterns. Proton NMR, infrared spectroscopy, and ultraviolet spectroscopy provide complementary data. The motional state of water is determined by solid-state quadrupole echo deuterium NMR spectroscopy of oxidized polyethylene that has been saturated with D20. The water associated with polyethylene has an approximate correlation time of 1CT9 s at 20 °C.

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Section: Resultsmentioning

confidence: 91%

Thermal oxidation and its analysis at low levels in polyethylene

Jelinski¹,

Dumais²,

Luongo³

et al. 1984

Macromolecules

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Chemical reactions in crosslinking of copolymers of ethylene and vinyltrimethoxy silane

Hjertberg

Palmlöf

Sultan³

1991

J of Applied Polymer Sci

105

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'Neste Polyeten AB, S-444 86 Stenungsund, Sweden SYNOPSISThe crosslinking reactions of a new type of polyethylene, an ethylene vinyltrimethoxy silane (EVS) copolymer, when reacted with water has been studied. Samples of EVS were treated in water a t 90°C. The kinetics of the crosslinking was followed by measuring the gel content and by determination of the content of different structures ( -Si-OCHB, -Si-OH, and -Si-0-Si-) using FT-IR. The observations show that a maximum gel content of 70-75% is obtained after 25 h treatment in water at 90°C. On the other hand, the absorption index for the crosslinks, -Si-0-Si-, continues to increase until about 100 h, i.e., more crosslinks seem to be formed without a simultaneous increase in gel content. Mechanical measurements showed decreased elongation a t break even after very long treatments. Thermo-oxidative degradation is, however, also responsible for the change in mechanical properties. For properly stabilized samples, the decrease in elongation leveled off after about 100 h of treatment. This indicates that the crosslinks formed after 25 h mainly should be within the already existing gel. The observed synergistic effect of crosslinking and thermo-oxidative degradation emphasizes the importance of a proper stabilizing system. INTRODUCTIONIn many applications there is a need to improve the properties of polyethylene, in particular with respect to heat deformation resistance; but chemical resistance, stress cracking, shrinkage, etc. may be important as well. Crosslinking is then an obvious alternative, and it is used today on a large commercial scale. The most common technique is radical crosslinking's2 initiated by peroxides or by irradiation. Both these crosslinking techniques suffer, however, from high investment costs. In the case of radiation initiation crosslinking efficiency decreases with thickness, and thick sections are impossible to crosslink sufficiently. In the case of peroxide crosslinking production, speed is limited by the cure rate and the demands for a certain residence time in the heating zone. The extrusion rate is in itself also limited by the necessity to use a rather low melt temperature. After the introduction of the S i o p l a~~?~ and Monosi15 techniques in the seventies, silane crosslinking of polyethylene has been an expanding field. In both these processes vinyl silane is grafted to the polymer chains after initiation by a small amount of added peroxide. The crosslinking is then performed by a water treatment after the addition of a catalyst in the final extrusion step. In commercial processes typical conditions to obtain crosslinking may be treatment at 80-90°C at 100% RH or in water. The use of free radicals for the grafting reaction leads to side reactions, in particular molecular enlargement, in the same way as observed in connection with compounding and processing prior to peroxide crosslinking. These reactions negatively influence the surface finish, limit the choice of antioxidants, and lead to increased consumption of antioxidants. Dec...

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Studies on homologous series of oligomeric antioxidants derived from p‐cresol/formaldehyde condensates. II. Evaluation in polystyrene

1972

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The effectiveness of compounds of the type R -H, CH3. and C(CH3)s n -0.1.2 and 4 R as antioxidants in polystyrene has been examined and the results compared with those for some commercial high mol. wt. antioxidants. Effectiveness was found to depend not only on mol. wt., but also on molecular structure, concentration, and temperature of me. ZUSAMMENFASSUNG: Die Wirksamkeit von Verbindungen des Typs R -H, CH3 und C(CH&; n -0 , 1 , 2 und 4 ale Antioxydantien in Polystyrol wurde untersucht, und die Resultate wurden mit denen einiger kommenieller, hochmolekularer Antioxydantien verglichen. Wie sich zeigte, hing die Wirksamkeit nicht nur vom Mo1.-Gew. ab, sondern auch von der Molekularstruktur, der Konzentration und der Gebrauchstemperatur.

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The relationship between rate of reaction with oxygen and chemical change in polymers as indicated by I.R. analysis

Cited by 14 publications

References 8 publications

Thermal oxidation and its analysis at low levels in polyethylene

Thermal oxidation and its analysis at low levels in polyethylene

Chemical reactions in crosslinking of copolymers of ethylene and vinyltrimethoxy silane

Studies on homologous series of oligomeric antioxidants derived from p‐cresol/formaldehyde condensates. II. Evaluation in polystyrene

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