Properties of oriented polyimide films prepared by different methods

Smirnova, V.Ye.; Bessonov, M.I.; Sklizkova, V. P.

doi:10.1016/0032-3950(90)90014-w

Cited by 7 publications

(3 citation statements)

References 2 publications

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“…As far as we know, most of the reported studies concerning the stretching of PI films focus mainly on the influences of stretching on the macroscopic property enhancement. [15,16] Very little attention has been paid to the detailed underlying molecular motions. In fact, although stretching of polymer materials usually does not bring any change in their chemical nature, it could alter the conformational structures of macromolecular chains, [17,18] inducing molecular rearrangements and the evolving of higher order packing structures, such as molecular alignments, orientations, and crystallizations.…”

Section: Introductionmentioning

confidence: 99%

Insights into Entropy Change of β₂ Relaxation in Retraction of Uniaxially Stretched Polyimide Films

Jiang,

Hu,

Cui

et al. 2023

Macro Chemistry & Physics

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Stretching has been extensively applied for decades in the production of polyimide (PI) materials with improved mechanical, electrical, and thermal properties. Meanwhile, a detailed understanding of the molecular motions during stretching is still limited. Herein, the thermomechanical behaviors of uniaxially stretched PI films prepared from 3,3′,4,4′‐biphenyl tetracarboxylic dianhydride (BPDA) and 2,2′‐bis (trifluoromethyl) benzidine (TFDB) are studied, and the possible molecular motions responsible for the sub‐glass transition temperature (Tg) stretchability and retraction after stretching are systematically investigated. Based on X‐ray diffraction and dynamic mechanical analysis, it is revealed that both the sub‐Tg stretchability and retraction correlates with β2 relaxation, which originates from the highly cooperative molecular motions of conformational rotations involving segmented BPDA units. A thermodynamic model is established and applied for the analysis of the retraction behaviors of stretched BPDA‐TFDB PI films. It is found that the increase of entropy under stretching plays a significant role in most retraction cases. However, as the stretching temperature increases, the α relaxation‐correlated large‐scale molecular motions emerge. Such motions partially counterbalance the conformational rotations of BPDA segments, leading to an enhanced contribution of enthalpy decrease during the retraction of BPDA‐TFDB PI films.

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Section: Introductionmentioning

confidence: 99%

Insights into Entropy Change of β₂ Relaxation in Retraction of Uniaxially Stretched Polyimide Films

Jiang,

Hu,

Cui

et al. 2023

Macro Chemistry & Physics

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“…Due to its flexible nature, PI membranes need to be stretched and fixed to have good surface flatness, which is crucial in optical applications. The stress and its distribution in such PI membrane-based devices play an important role in affecting surface figure and device performance [5][6][7][8][9][10]. The optical PI membrane is a promising isotropic material for large-aperture-membrane diffractive lenses applied in next-generation space telescopes [11].…”

Section: Introductionmentioning

confidence: 99%

Investigation of Photoelastic Property and Stress Analysis for Optical Polyimide Membrane through Stress Birefringence Method

et al. 2020

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Optical polyimide (PI) membranes have been increasingly attractive in optoelectronic substrate and optical element material applications. Controlled stress distribution is very important to optical PI membrane-based optics. However, nondestructive absolute stress measurement inside optical PI membranes remains challenging. In this letter, we adopted the stress birefringence method to experimentally investigate the correlation between stress and retardation in uniaxially, biaxially, and circularly stretched PI membranes. The calculated value of the photoelastic coefficient was found to be around 400 nm/Mpa·cm. A theoretical model was established where the retardation angle is the negative arctan of the principal stress ratio in the biaxially stretched membrane. We also found that the average retardation angle is an important parameter for evaluating the uniformity of stretching force in the circularly stretched membrane. This work provides a better understanding of the stress birefringence measurement of membrane materials.

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“…Aromatic polyimides [1] tend to be somewhat intractable, however1 conventional melt or solution processing is difficult. In general, the approaches to processing polyimides have been: (1) to process a precursor polyamic acid in solution and then convert it to the imide form1 (2) to synthesize meltor solution-processable linear polyimides by careful choice of monomers and control of molecular weight1 or (3) to employ processable monomers or oligomers that can later be cured and crosslinked via addition chemistry. The first approach has been used to improve properties of films via stretch-orientation of the polyamic acid [2,3].…”

Section: Introductionmentioning

confidence: 99%

Stretch-orientation of LaRC™ RP50 Polyimide Film

Hawkins

Hinkley

Pater

et al. 2006

High Performance Polymers

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Properties of oriented polyimide films prepared by different methods

Cited by 7 publications

References 2 publications

Insights into Entropy Change of β₂ Relaxation in Retraction of Uniaxially Stretched Polyimide Films

Insights into Entropy Change of β₂ Relaxation in Retraction of Uniaxially Stretched Polyimide Films

Investigation of Photoelastic Property and Stress Analysis for Optical Polyimide Membrane through Stress Birefringence Method

Stretch-orientation of LaRC™ RP50 Polyimide Film

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Properties of oriented polyimide films prepared by different methods

Cited by 7 publications

References 2 publications

Insights into Entropy Change of β2 Relaxation in Retraction of Uniaxially Stretched Polyimide Films

Insights into Entropy Change of β2 Relaxation in Retraction of Uniaxially Stretched Polyimide Films

Investigation of Photoelastic Property and Stress Analysis for Optical Polyimide Membrane through Stress Birefringence Method

Stretch-orientation of LaRC™ RP50 Polyimide Film

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Product

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Insights into Entropy Change of β₂ Relaxation in Retraction of Uniaxially Stretched Polyimide Films

Insights into Entropy Change of β₂ Relaxation in Retraction of Uniaxially Stretched Polyimide Films