A New Approach to the Description of Mechanical Behavior of Polymer Glasses

Arzhakov, M. S.; Arzhakov, S. A.

doi:10.1080/00914039508012119

Cited by 9 publications

(6 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The existence of two regimes of recovery has also been reported by Hassan and Boyce (7) and Azharkov and Azharkov (8,9). The present data are consistent with the suggestion that changes are associated with the relaxation of residual thermal stresses at heat treatment temperatures below Tg, and with the randomization of orientation above Tg.…”

Section: Discussionsupporting

confidence: 93%

“…They reported the presence of two distinct A. McDonagh-Smith, J. C. Arnold, and D. H. ISCUE regimes of recovery: the first below Tg and the second above Tg. The existence of these two regions of recovery was also evident from dilatometry measurements reported by Azarkhov and Azarkhov, also on uniaxially compressed PMMA (8,9).…”

Section: Jntroductionsupporting

confidence: 75%

“…Figures 6 and 7 illustrate the variations in curvatures across the sheet for these individual longitudinal and transverse samples, and Rg. 8 shows the average figures for both orientations as a function of heat treatment temperature (up to 140°C). As with length changes, there is little change in curvature following heat treatment up to 100°C.…”

Section: Resultsmentioning

confidence: 99%

“…These results indicate that the level of thermal residual stress is relatively constant across sheets of both copolymers, whereas orientations are lower at the edges than across the central region of the sheets. It may be that edge effects during extrusion play a part, but also, since some recovery is known to occur during deformation (8,9). it is likely that this recovery occurs preferentially at the edges of the sheet where there is less constraint during calendering.…”

Section: Discussionmentioning

confidence: 99%

See 3 more Smart Citations

Thermal stresses and orientations in acrylic sheet

McDonagh-Smith

Arnold

Isaac

2001

Polymer Engineering & Sci

View full text Add to dashboard Cite

Two copolymers of poly(methy1 methacrylate) with 3% and 10??0 ethyl acrylate, respectively, were extruded and calendered, with the same line speed and roll temperatures. The residual stresses and anisotropies, induced by the complex processing deformations and temperature variations, were characterized by monitoring the dimensional changes and sample curvatures resulting from subsequent heat treatments. In both copolymers, two distinct recovery regimes were observed: heat treatments just below Tg caused relaxation of residual thermal stresses and at temperatures above Tg led to recovery of chain extended orientations. It was found that the similar processing conditions induced similar residual thermal stresses in the two copolymers, but the higher viscosity of the 3% EA sheet led to greater residual orientations. Across the width of the sheets, little variations were seen in the thermal stresses, but orientations were lower at the edges. Some curvature changes observed following heat treatment well below Tg, were interpreted as resulting from aging effects. JNTRODUCTIONmethod used in the present analysis, the recovery of xtruded and calendered sheet is produced for a and for subsequent thermoforming. Calendering involves the cooling of an extrudate around a series of rolls to produce flat sheets of uniform thickness. The large thermal gradients and imposed strains during calendering may lead to unacceptably high levels of residual stresses in the fiial sheet, causing warping or even promoting failure (1-4). High levels of preferred orientation lead to anisotropy in mechanical properties (5) and may also present difficulties during subsequent processing at temperatures where orientations relax. For these reasons, knowledge of the levels of residual thermal stresses and orientations in calendered plastics is desirable. Furthermore, an understanding of the factors that are important in determining these levels presents a route towards producing an optimized microstructure, suitable for subsequent processing. In the longer term, control of orientation and residual stresses may also prove to be a useful tool in polymer engineering. Before an analysis can be made of the effects of calendering conditions on residual stress and orientation distributions, procedures must be developed to characterize fully these distributions. Both residual stresses and orientations are known to relax at elevated temperatures as a polymer recovers. In the E W .de range of uses, both directly in sheet form 'Corresponding author. E-mail. d.h.isaa&swansea.ac.uk samples is monitored as they are-heat treated across a range of temperatures, including that associated with the glass transition. At elevated temperatures, the polymer network approaches an equilibrium state due to increased molecular mobility. This process is driven by the dissipation of elastic and inelastic strain energy, stored during calendering. Polymer recovery manifests itself in these materials in the form of changes in length and curvature, which are readily measurable. Thes...

show abstract

Section: Discussionsupporting

confidence: 93%

Section: Jntroductionsupporting

confidence: 75%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Thermal stresses and orientations in acrylic sheet

McDonagh-Smith

Arnold

Isaac

2001

Polymer Engineering & Sci

View full text Add to dashboard Cite

show abstract

“…plasticization of PMMA, and copolymerization of methyl methacrylate with methacrylic monomers [5,7]. This experimental evidencc was attributed to enhancement of local segmental mobility in certain structural sublevels.…”

Section: S a R Z H A K O V A N D S A A R Z H A K O Vmentioning

confidence: 90%

Physical and Mechanical Behavior of Polymer Glasses. IV. Cross-Linked Poly(Methyl Methacrylate)

Arzhakov

1997

International Journal of Polymeric Materials

Self Cite

View full text Add to dashboard Cite

Temperature-induced relaxation of plastic deformation in cross-linked PMMA samples was studied. For cross-linked PMMA with low concentration of cross-linking agent (less, than 5.2 mol.%), relaxation curves involve low-temperature component at temperatures well below glass transition temperature and high-temperature component at temperatures close to glass transition. Increasing concentration of cross-linked agents in polymer samples to 11.2 mol.% is accompanied with degeneration of high-temperature component of relaxation, and complete relaxation of plastic deformation proceeds via low-temperature component. The effect of cross-linking on temperature-induced relaxation of plastic deformation was discussed in terms of restriction of segmental mobility within certain structural regions in polymer sample.

show abstract

Characterizing the Temperature Dependent Spring-Back Behavior of Poly(Methyl Methacrylate) (PMMA) for Hot Embossing

Mathiesen

Dupaix

2014

Challenges in Mechanics of Time-Dependent Materials, Volume 2

View full text Add to dashboard Cite

A New Approach to the Description of Mechanical Behavior of Polymer Glasses

Cited by 9 publications

References 4 publications

Thermal stresses and orientations in acrylic sheet

Thermal stresses and orientations in acrylic sheet

Physical and Mechanical Behavior of Polymer Glasses. IV. Cross-Linked Poly(Methyl Methacrylate)

Characterizing the Temperature Dependent Spring-Back Behavior of Poly(Methyl Methacrylate) (PMMA) for Hot Embossing

Contact Info

Product

Resources

About