The influence of thermal history on internal stress distributions in sheets of PMMA and polycarbonate

Saffell, John; Windle, A. H.

doi:10.1002/app.1980.070250614

Cited by 49 publications

(10 citation statements)

References 10 publications

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“…On the other hand, PET/PC blends were opaque, apparently because of the phase separation between PET and PC, as shown in Figure 1. These results clearly demonstrate that FBP/PC alloy system is absolutely compatible and miscible, whereas conversely, PET/PC alloys are completely immiscible and incompatible 14–15…”

Section: Resultsmentioning

confidence: 66%

Preparation of a novel alloy composed of fluorene‐based polyester and polycarbonate and their properties for the optical uses

Kawasaki

Yamada

Kobori

et al. 2008

J of Applied Polymer Sci

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This paper is concerned with the structures and properties for fluorene-based polyester-polycarbonate (FBP/PC) alloys. Obtained alloys were characterized thermodynamically, optically, and viscoelastically, and the relationship between drawing behavior and molecular dynamics were also investigated. FBP/PC alloys showed transparent and a single glass transition temperature (Tg) for all compositions that indicated the complete compatibility in FBP/PC alloy systems. Tendency of the maximum draw ratios for alloy sheets was very similar to the profile of Tg versus FBP content. Maximum draw ratio was increased linearly with FBP content, demonstrating the intimate relationship between the large deformation and the molecular motion. A large amount of orientational birefringence occurred in PC sheet, but in the case of FBP/PC alloys and FBP, orientational birefringence was drastically decreased or not observed at all. This meant that positive birefringence of PC molecules was compensated by the absolutely smaller birefringence of FBP molecules. From a molecular mobility perspective, relaxation time (T2) for PC was smaller even at 200 C. However, for FBP and its alloys, T2 were much larger, showing the considerably enhanced molecular mobility in FBP or FBP/PC alloys. In this study, we could first reveal that the relationship between Tg and FBP content was very similar to the behaviors of birefringence (Dn)/draw ratio (k) versus FBP content, T2 versus FBP content and 1/maximum draw ratio (k max ) versus FBP content. Based on these results, we were able to propose a novel alloy with high refractive index, low orientational birefringence, and higher processability by alloying FBP with PC.

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Section: Resultsmentioning

confidence: 66%

Preparation of a novel alloy composed of fluorene‐based polyester and polycarbonate and their properties for the optical uses

Kawasaki

Yamada

Kobori

et al. 2008

J of Applied Polymer Sci

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“…Although most ofthe studies are of a preliminary nature, the phenomenon itself has been defined and distinguished from other phenomena that frequently accompany residual stresses, such as molecular orientation. In recent studies, the level and distribution of R. S. in thermally treated amorphous polymers (1)(2)(3) as well as in melt-processed (4-7) and cold-rolled (8)(9) polymers, have been investigated. The effect of thermal history, including quenching through a variety of temperature gradients and levels with respect to the polymer glass discussed in Part I of the presint study (10).…”

Section: Introductionmentioning

confidence: 99%

Residual stresses in polymers III: The influence of injection‐molding process conditions

Siegmann

Buchman

Kenig

1982

Polymer Engineering & Sci

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Following the evaluation of Residual Stresses (R.S.) in quenched specimens (Part I) and the resulting mechanical‐physical properties (Part II), the, present study deals with the effect of injection‐molding process conditions on R.S. and the respective properties of amorphous polymers. Melt temperature, mold temperature, injection rate, and injection pressure were the parameters studied. Experimental results indicated that the melt temperature caused two maxima in R.S. The second one reverses from compressive to tensile. In general, most changes occur in the surface regions, while R.S. decreases with increasing melt temperature, as is the case in zones far away from the gate. Furthermore, tensile modulus increased, in general, with rising melt temperature. In the case where the effect of mold temperature was studied, it was found that R.S. are compressive in the surface layers and tend to decrease upon increase in mold temperature and distance from the entrance region. Significant changes in R.S. were also detected in the interior layers. As the mold temperature approached Tg, low values of R.S. were measured, as was the case in quenched specimens. Injection rate affects surface R.S. to a large extent. With low flow rates, tensile stresses were developed in the exterior, reversing to compressive stresses at higher speeds. The reversal in sign depends on the location relative to the gate. Once compressive stresses were formed, further increase in rate caused a reduction in R.S. In addition, variations in tensile modulus, as high as 30 percent, were measured at high injection rates. As far as injection and holding pressures are concerned, experimental results showed that a maximum in R.S. was obtained, with increasing pressure, at the surface. Close to the gate entrance, a reverse from compressive to tensile R.S. was detected at high injection pressures. As in the other cases, injection pressure influenced mostly the exterior layers. Only in zones close to the entrance and at high pressures were high levels of R.S. measured in the core regions.

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“…Experiments on polymer materials by many researchers showed that after the annealing of polymer materials there is still certain amount of birefringence remained [7,8] .…”

Section: Transverse Birefringence Due To Molecular Alignmentmentioning

confidence: 98%

“…This quenching-induced birefringence can be removed by annealing process [5,7] , in which the temperature of the fibre is raised to a certain level, and then the fibre is cooled down to room temperature gradually and slowly with very similar temperature across the whole cross section of the fibre. This will relax the internal thermal stress due to the quenching temperature gradient and therefore remove the birefringence caused by quenching effect.…”

Section: Transverse Birefringence Due To the Quenching Effectmentioning

confidence: 99%

Transverse birefringence in polymer optical fiber introduced in drawing process

Peng

2003

SPIE Proceedings

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In this work, we investigated the transverse birefringence in PMMA-based polymer optical fibre introduced in the drawing process. We proposed a simple theoretical model that attributes the induced transverse birefringence to three major factors: quenching effect, molecular alignment, and thermal expansion mismatch. Various experiments have been designed and performed to ascertain and identify the individual contribution of the three factors. In our experiments, polymer optical fibres are drawn under varying conditions and end their transverse birefringence is measured using the interferometric microscope method. These experiments have determined the respective contributions of the three factors and produced important findings agreeable to our theoretical model: the birefringence increases with the drawing speed ratio; the quenching-induced birefringence has profile of parabolic shape which can be removed by annealing; the profile of birefringence due to thermal expansion mismatch has an abrupt change at the core-cladding interface; and the birefringence induced by molecular alignment is constant across the fibre, and the magnitude is small.

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The influence of thermal history on internal stress distributions in sheets of PMMA and polycarbonate

Cited by 49 publications

References 10 publications

Preparation of a novel alloy composed of fluorene‐based polyester and polycarbonate and their properties for the optical uses

Preparation of a novel alloy composed of fluorene‐based polyester and polycarbonate and their properties for the optical uses

Residual stresses in polymers III: The influence of injection‐molding process conditions

Transverse birefringence in polymer optical fiber introduced in drawing process

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