The nature of the thermal transitions in poly(p-oxybenzoate)

Economy, James; Volksen, W.; Viney, Christopher; Geiss, Roy H.; Siemens, R.; Karis, T. E.

doi:10.1021/ma00187a023

Cited by 97 publications

(68 citation statements)

References 6 publications

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“…The crystallization peak of R5 should be attributed to PHBA, because its Tc is too high to be that of PET. 21 Moreover, the high value (340°C) of the T m of PHBA (22) agrees with the observed Tc. The crystallization peak of pure R3 was probably due to PET due to its low Tc.…”

Section: Phase Structuresupporting

confidence: 66%

Phase Structure, Processability, and Mechanical Properties of Rodrun Liquid Crystalline 5000/Rodrun Liquid Crystalline 3000 Blends

Vallejo¹,

Eguiazábal²,

Nazábal³

2001

Polym J

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ABSTRACT:New liquid crystalline materials with low processing temperature, whilst maintaining the mechanical properties characteristic of the liquid crystalline polymers, were sought by blending Rodrun 5000 and Rodrun 3000. After direct injection moulding, the solid blends appeared as miscible. The crystallization from the melt was hindered by the presence of the other component, but the minimum processing temperature of Rodrun 5000 clearly decreased as a consequence of the presence of Rodrun 3000. This decrease was not at the cost of a decrease in the overall mechanical properties. It should be noted that, unlike in thermoplastics blends, in liquid crystal polymer (LCP) blends the miscibility level influences the modulus values. Immiscibility leads to clear positive synergisms in the values of the modulus of elasticity and also in the tensile strength, that are not seen in miscible LCP blends.KEY WORDS Rodrun Liquid Crystalline 5000 I Rodrun Liquid Crystalline 3000 I Blends I Structure I Processability I Mechanical Properties IThe use of liquid crystal polymers (LCP's) as reinforcements for thermoplastic matrices has attracted considerable interest in the two last decades. 1 · 2 This is due to the fact that when thermoplastic!LCP blends are subjected to extensional flow, the LCP phase is deformed into fibrils that reinforce the matrix. A clear limitation of thermoplastic!LCP blends is that most of the commercial and performance LCP's have to be processed at temperatures close to 300'C. For this reason, most LCP's can be only blended with heat resistant thermoplastics. A possible solution to this problem is the reduction of the processing temperature of the LCP's by blending with another LCP with a lower processing temperature. This aspect has not been studied much; 3 · 4 in LCPILCP blends, the structure, 3 · 5 -15 rheological properties, 3 · 4 · 6 · 9 -11 • 16 morphology, 6 mechanical properties 4 -6 · 9 · 13 · 17 -20 and reactions in the melt state 3 · 7 · 8 • 13 are the subjects of most study.Apart from a possible reduction of the processing temperature, two additional important advantages are usually found in LCPILCP blends: a synergistic mechanical behavior 5 · 6 · 9 · 13 · 17 · 19 · 20 and a melt viscosity lower than that of either of the pure components. 9 -11 These possibilities make LCPILCP blends clearly attractive.Rodrun LC 5000 (R5) is an important commercial LCP with high processing temperature (300'C), whereas Rodrun LC 3000 (R3) has one of the lowest (240'C) LCP processing temperatures. Both are copolyesters of poly-(hydroxybenzoic acid) (PHBA) and poly(ethylene terephthalate) (PET) with different comonomer ratios. The blends of these two LCP's could produce materials with intermediate properties that would widen the commercially available range of LCP's. This is in addition to the possibility of reducing the processing temperature of R5.Moreover, when the phase structure of R5/R3 blends obtained in a Haake mixer was studied, the blends were found to be miscible. 14 The processability of blends of...

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Section: Phase Structuresupporting

confidence: 66%

Phase Structure, Processability, and Mechanical Properties of Rodrun Liquid Crystalline 5000/Rodrun Liquid Crystalline 3000 Blends

Vallejo¹,

Eguiazábal²,

Nazábal³

2001

Polym J

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“…And the naphthalene homopolyester I-0 reveals small endotherms before the final melting transition. Such a premelting phnenomenon 23,25,37 is fairly common for polymers that are able to form different sizes of crystallites with varying degrees of defects. In case of the II-0.5, II-0.7, and II-0.85, the endothermic peaks appearing before melting transition seem to be related to crystal-to-crystal transition.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and characterization of a series of wholly aromatic copolyesters containing 2-(?-phenylisopropyl)hydroquinone moiety

Song

Yun

Jin

1999

J. Polym. Sci. A Polym. Chem.

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“…It is noted that ref. 35 does not indicate whether the dimer and tetramer are liquid crystalline; the heat of transition listed would suggest these two oligomers were undergoing melting rather than a crystal-liquid crystal transition. On the other hand, better agreement was obtained for CTFMP samples; a CTFMP sample polymerized 5 h at 180°C had a 285°C T k-m , corresponding to a DP of 15, 35 with a lamellar thickness of about 100 Å (DP ϭ 16).…”

Section: Bulk Melt Polymerizationmentioning

confidence: 98%

“…35 does not indicate whether the dimer and tetramer are liquid crystalline; the heat of transition listed would suggest these two oligomers were undergoing melting rather than a crystal-liquid crystal transition. On the other hand, better agreement was obtained for CTFMP samples; a CTFMP sample polymerized 5 h at 180°C had a 285°C T k-m , corresponding to a DP of 15, 35 with a lamellar thickness of about 100 Å (DP ϭ 16). 10 Although the bulk melt polymerization DP-T k-m data above is not as consistent as that for the CTFMP sample, a 180°C T p is below the T m of even dimers (230°C 35 and 216.5°C 36 for the acetoxy-dimer), leading to our suggestion the presence of the "melt" must be due to mutual solution of a number of "monomers".…”

Section: Bulk Melt Polymerizationmentioning

confidence: 98%

“…However, neither DP nor T k-m were determined for all but one of the samples listed in Table II and only limited DSC data is available in the literature. 9 A bulk melt, an acetone-extracted sample polymerized at 180°C for 40 h had a 250°C T k-m in a first-run DSC scan with TEM of related samples indicating lamellar thicknesses of about 70 Å for samples polymerized 24 and 32 h. 9 The DSC data corresponds to the T k-m of oligomers with a DP of about 3 (acetoxy-tetramer T m is 262°C 35 ) although our IR measurements on solution polymerized samples (ref. 14, Table II) suggest a higher value (e.g., 10 -11 for T k-m ϭ 253-255°C, 26 -49 for T k-m ϭ 260 -265°C) for samples with this T k-m .…”

Section: Bulk Melt Polymerizationmentioning

confidence: 99%

See 1 more Smart Citation

Phase I and II crystals of poly(p-oxybenzoate). I. Effects of substrate and melt polymerization conditions

Rybnikář¹,

Sáha²,

Yuan

et al. 1999

J. Polym. Sci. B Polym. Phys.

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Acid and base treatment of glass and mica substrates affects the phase II/I crystal structure ratio of poly(p‐oxybenzoic acid) polymerized by the confined thin film melt polymerization (CTFMP) technique; acid treatment of mica enhances the phase I content, whereas base treatment of glass and mica results in growth of 100% phase II crystals. In bulk melt polymerized samples, without added catalyst, the fraction of phase II increases with increasing polymerization temperature, up to 25–30% above 300 °C; this is suggested to be related to a “PH phase” (pseudo‐hexagonal), consisting of 3 pairs of phase I and II crystals, rotated by 60°, in CTFMP samples annealed above their Tk‐m. The addition of a base to the polymerization system also results in an increase in the phase II content, up to almost 100% in some cases. The effect of the addition of base is tentatively attributed to a change in the alignment of neighboring molecules growing out from the initial nucleus during the simultaneous polymerization (liquid crystal) crystallization. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3520–3531, 1999

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The nature of the thermal transitions in poly(p-oxybenzoate)

Cited by 97 publications

References 6 publications

Phase Structure, Processability, and Mechanical Properties of Rodrun Liquid Crystalline 5000/Rodrun Liquid Crystalline 3000 Blends

Phase Structure, Processability, and Mechanical Properties of Rodrun Liquid Crystalline 5000/Rodrun Liquid Crystalline 3000 Blends

Synthesis and characterization of a series of wholly aromatic copolyesters containing 2-(?-phenylisopropyl)hydroquinone moiety

Phase I and II crystals of poly(p-oxybenzoate). I. Effects of substrate and melt polymerization conditions

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