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Journal of Thermal Analysis and Calorimetry
Authors: M. Arnal, V. Balsamo, G. Ronca, A. Sánchez, A. Müller, E. Cañizales, and C. Urbina de Navarro

Abstract  

A new technique to thermally fractionate polymers using DSC has been recently developed in our laboratory. The applications of the novel successive self-nucleation and annealing (SSA) technique to characterize polyolefins with very dissimilar molecular structures are presented as well as the optimum conditions to thermally fractionate any suitable polymer sample with SSA. For ethylene/-olefin copolymers, the SSA technique can give information on the distribution of short chain branching and lamellar thickness. In the case of functionalized polyolefins, detailed examinations of SSA results can help to establish possible insertion sites of grafted molecules. The application of the technique to characterize crosslinked polyethylene and crystallizable blocks within ABC triblock copolymers is also presented.

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Journal of Thermal Analysis and Calorimetry
Authors: Blanca Rojas de Gáscue, José Luis Prin, Gilma Hernández, Enrique M. Vallés, Arnaldo T. Lorenzo, and Alejandro J. Müller

maximum lamellar sizes attained. Successive Self-nucleation and Annealing (SSA) is a thermal fractionation technique, developed by Müller et al. in 1997, which has gained wide acceptance in the literature [ 15 – 19 ]. It is based on the sequential

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Abstract  

Bisphenol-A polycarbonate (BAPC) was crystallised by exposure to acetone vapours for a period of 9 h; it developed a 20% crystallinity according to WAXS measurements. The samples of semi-crystalline BAPC were then submitted to a series of thermal treatments including annealing, self-nucleation and subsequent isothermal crystallizations. The results showed that the polymer possesses a remarkable crystalline memory and a much faster recrystallization and reorganization capacity (lamellar thickening) than its very low thermal crystallization rate. This peculiar crystallization behaviour probably stems from its rigid backbone molecular structure.

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was from −75 to 120 °C. Isothermal crystallization experiments at various temperatures in the range of 30–47.5 °C were performed after self-nucleation of the polyester sample. Self-nucleation measurements were performed analogous to the

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Abstract  

Nucleation of crystallizable polymers is quantified through an efficiency scale obtained and calculated using differential scanning calorimetry (DSC). This scale, defined in self-nucleation experiments, is a simple, convenient and reliable calorimetric efficiency scale. Typical nucleating agents for isotactic polypropylene are evaluated; they rate at best at 60 to=70% on this efficiency scale.

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Abstract  

The investigation of the intermolecular composition distribution of an ethylene/1-hexene copolymers using DSC method has been carried out. The known methods: step crystallization (SC) and successive self-nucleation/annealing (SSA) have been adapted for this purpose, and particularly, the optimal condition of the process have been chosen to enable the best fractional crystallization of the copolymer. The method has been applied for fractionation of two ethylene/1-hexenecopolymers synthesized with supported vanadium and zirconocene catalysts and having similar concentrations of 1-hexene. Although metallocene catalysts are known from their more homogeneous structure of active sites in comparison to multi-site Ziegler–Natta catalysts, the copolymers obtained over both catalytic systems gave DSC curves resolved into several peaks but with different melting points. Using the Thomson–Gibbs equation, comparable average lamellar thickness of the separated peaks has been calculated. The amounts of copolymer fraction with defined lamellar thickness have been determined. It was obtained that the copolymer produced from the metallocene system contains a thinner and more homogeneous lamella thickness than that obtained with Ziegler–Natta vanadium catalyst supported on the same carrier.

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Abstract  

Normally, for Standard DSC, the PerkinElmer power-compensation setting is the low dynamic range mode (LDRM). In this mode, a noise filter is applied to decrease the noise-to-signal ratio, which concomitantly gives rise to a delay in time of the signal measured. In case the signal is expected to be of high intensity — experienced for instance at high scan rates using High Performance DSC (HPer DSC) — the noise filtering could be diminished by which the associated delay in time would be less, leading to a faster response of the instrument, also resulting in an improved resolution. In fact, such can be realized using the faster noise filter of the high dynamic range mode (HDRM) available for the Pyris 1 and Diamond DSCs, which DSCs are both equipped with the HyperDSCTM technique (HyperDSC being the commercial version of HPer DSC). The improvement in response is maximal for high rates like 100–500°C min−1 but even at low rates like 10°C min−1 it is still significant. Thus, taking advantage of HDRM, low-molar substances like indium and 4,4′-azoxyanisole show appreciable increasing height-to-width ratios for signals caused by crystallization, melting and the crystal <>liquid crystal transition respectively. Another advantage, the faster realization of steady state after the starting of the DSC, is of help in case of overlapping starting and transition signals during dynamic crystallization and melting, and during isothermal crystallization as elucidated for a HDPE. For 4,4′-azoxyanisole and for an ethylene-propylene copolymer having a broad melting range, it is shown that such faster response leads to a still better resolution with respect to temperature, even at high scan rates. Thus, the peaks belonging to the crystal-to-liquid crystal and the liquid crystal-to-isotropic liquid transitions of 4,4′-azoxyanisole were completely resolved while a thermal fractionation of the copolymer by the successive self-nucleation and annealing (SSA) technique with good resolution has been realized, both using rates as high as 200°C min−1.

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supercoolings of only 20–50 K [ 8 ]. Self-nucleation is the third type of nucleation. Both, high and low-temperature self-nucleations have been suggested ([ 8 ], Vol. III, Sect. 5.1.4). The self-nuclei were found to remain after heating

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obtain β -PP in the PET20A blend by changing the T f . The higher T cp and T m of PP in the PET20A blend melted at T f of 160 °C was attributed to the effect of the self-nucleation of unmolten PP crystals and re-crystallization of PP

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