Thermomechanical and thermogravimetric analyses of systematic series of polyimides

Gillham, J. K.; Hallock, K. D.; Stadnicki, S. J.

doi:10.1002/app.1972.070161013

Cited by 47 publications

(6 citation statements)

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“…a y relaxation process can be observed. This process has been attributed to moisture absorption (3, 4,6) and is consistent with the results from dielectric relaxation studies (16,17). Since our purpose is to understand the origin of the p relaxation process, the y relaxation will not be further discussed.…”

Section: Introductionsupporting

confidence: 86%

The origin of β relaxations in segmented rigid‐rod polyimide and copolyimide films

Arnold

Bruno

Shen

et al. 1993

Polymer Engineering & Sci

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Most aromatic polyimides and copolyimides show a β relaxation process below their α relaxation processes in dynamic mechanical and dielectric measurements. The origin of this β relaxation has been under active discussion. In order to gain a better understanding of the origin of the β relaxation process, the dynamic mechanical behavior of a series of segmented rigid‐rod polyimide and copolyimide films with different dianhydrides and diamines has been systematically studied. For some of the polymers, crystallinity and orientation effects on the β relaxation process were also investigated. It is found that the β relaxation process in the unoriented films can mainly be attributed to a relatively noncooperative motion in uncrystallized diamines. However, this noncooperative nature may be gradually lost by increasing the crystallinity and orientation. Molecular modeling and computation have led to a discussion of possible diamine motion in the β relaxation process.

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Section: Introductionsupporting

confidence: 86%

The origin of β relaxations in segmented rigid‐rod polyimide and copolyimide films

Arnold

Bruno

Shen

et al. 1993

Polymer Engineering & Sci

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“…On the other hand, flexural vibration and resonance frequency methods are subject to possible deterioration resulting from high‐frequency fatigue 34. In this ultrasonic method, we observed many friction peaks, compared with those of low‐frequency (<15 kHz) methods such as torsional pendulum32, 35 and resonance frequency 28, 36. For this reason, it is known that the ultrasonic thermal relaxation losses occur when significant segments of the polymer chain oscillate at the same frequency as that of the applied wave 37.…”

Section: Resultsmentioning

confidence: 97%

Temperature dependency of elastic moduli and internal dilational and shear frictions of polyetherimide

Fukuhara

2003

J of Applied Polymer Sci

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ABSTRACT:To investigate the thermally activated structural change of polyetherimide, longitudinal and transverse wave velocity, six kinds of elastic parameters (Young's, shear, and bulk moduli, Lamé parameter, Poisson's ratio, and Debye temperature), and dilational and shear internal frictions were simultaneously measured over a temperature range 69 -474 K, using the ultrasonic pulse method. All elastic moduli decreased with increasing temperature, suggesting a lowering of molecular bonding strength. From shear internal friction, the 190, 314, 371, 395, and 430 K peaks are interpreted as the ␥-[derived from -C(AO)-motion], ␤* 1 -(interplane slippage between benzene rings), ␤-(softeningglass transition) peaks, and rotational vibration of main benzene rings and a local relaxation of the main chain, respectively. The abrupt increase peak from 449 K in dilational friction would be a low-temperature side shoulder of the ␣-glass-transition peak.

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“…PEI also shows a secondary transition at À100 C, which appears in all polyimides in which the rigid phenyl groups consist of rigid backbone molecules spaced with flexible groups such as methylene and ether. 50 The PEI/PC blends of this work showed a transition at the same temperature range as the neat components. No signs of a transition suppression, which could affect negatively the blend ductility 48 were observed.…”

Section: Mechanical Propertiesmentioning

confidence: 87%

Phase Structure and Mechanical Properties of Blends of Poly(ether imide) and Bisphenol A Polycarbonate

Ramiro¹,

Eguiazábal²,

Nazábal³

2004

Polym J

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Poly(ether imide) (PEI)/bisphenol A polycarbonate (PC) blends were obtained throughout the composition range both by direct injection moulding (DI blends) and by extrusion followed by injection moulding (PM blends). Although some reaction was observed by FT IR, the blends were fully phase separated at the detection level of DMTA. An anomalous decrease in the high temperature T g of the 90/10 and 80/20 blends, was only seen in PM blends. This was attributed to an anomalous thermodynamic behaviour, after rejecting degradation, reactions or particle size as possible explanations. With the exception of the PC-rich DI blends, the morphology was fine and homogeneous. Both the modulus of elasticity and the yield stress were very close to those expected from the rule of mixtures, whatever the morphology. Unexpectedly, ductility followed the same trend, even in the less homogeneous PC-rich DI blends. This points to the very slight reactions observed, and to parameters related to chemical features of the components (such as the highly aromatic character of the components of the blend) as the main reasons for the observed ductility behaviour. [DOI 10.1295/polymj.36.705] KEY WORDS Poly(ether imide) / Polycarbonate / Blends / Mechanical Properties / Phase Structure / Blending thermoplastic polymers 1,2 to obtain multicomponent materials is one of the most useful ways to develop new polymeric materials. This is because the costs associated with the development of a new polymer do not usually compensate the likely profit. Moreover, the preparation and development of blends based on commercial polymers requires less time for the optimisation of the final product. Usually, the components of a blend are selected looking at complementary characteristics in processability, final properties or price. Thus, polymer blending can allow the combination, for example, of an expensive high performance polymer with a cheaper one, to obtain the expected performance at an advantageous cost.Poly(ether imide) (PEI) is a high performance amorphous thermoplastic with good thermal stability (T g ¼ 220 C) and remarkable modulus of elasticity and tensile strength. 3 It is used, among other applications, for advanced parts in electrical and electronics industry, in aircraft applications and in the automotive industry. Blends of PEI with poly(ether ether ketone) (PEEK), 4-6 aliphatic-aromatic polyesters, 7-20 polyarylate (PAr), 21,22 polyamide 6,6, 23,24 poly(phenylene sulphide) (PPS) and polysulfone of bisphenol A (PSU), 25 among others, have been studied and several patents 26 with polymers such as polycarbonate, polyamides, polypropylene, polysulfones and liquid crystal polymers, have been granted.Bisphenol A polycarbonate (PC) is an engineering thermoplastic with applications in a wide variety of fields, such as electronics, illuminating engineering, household, automotive industry, sports, security elements, etc. Its blends with many other polymers have been studied 27,28 or registered, 26 and some of them such as those with poly(ethylene terepht...

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Thermomechanical and thermogravimetric analyses of systematic series of polyimides

Cited by 47 publications

References 1 publication

The origin of β relaxations in segmented rigid‐rod polyimide and copolyimide films

The origin of β relaxations in segmented rigid‐rod polyimide and copolyimide films

Temperature dependency of elastic moduli and internal dilational and shear frictions of polyetherimide

Phase Structure and Mechanical Properties of Blends of Poly(ether imide) and Bisphenol A Polycarbonate

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