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Abstract  

In pharmaceutical practice it is important and useful to know the crystallinity of materials and to monitor it during formulation development, production processes and storage. The purpose of this study was to assess the quantitative capability of DSC for determining crystallinity in crystalline/amorphous powder mixtures and to compare the accuracy of the DSC method with that of conventional powder X-ray diffraction. Alpha-lactose monohydrate was chosen as the model material. On the basis of this study it can be concluded, that DSC method can be applied safely for semiquantitative evaluation of the crystallinity of lactose samples consisting of an amorphous content higher than 20%.

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Abstract  

The evaluation of the crystallinity of several samples of ALPO-11 was performed by X-ray diffraction and thermogravimetry. Through XRD, the degrees of crystallinity of the samples were determined by the measurement of the area of the peaks at 2γ ranging from 20.7 to 24.1 degrees. The sample that presented the largest area was considered as 100% crystalline and the areas of the other samples were normalized in relation to this. From TG, the degree of crystallinity was determined considering the mass loss in the temperature range from 453 to 653 K that is related to remotion of di-isopropylamine molecules used during the synthesis procedure. The quantity of diisopropylamine on the material is proportional to the degree of crystallinity.

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Abstract  

The crystallinity of poly(ethyleneterephthalate) has been determined by differential scanning calorimetry and by density. The results obtained by calorimetry show that the increment in the crystallinity due to the heatsetting treatment is produced by the increase of the crystallinity corresponding to the premelting endothermic peak.

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Abstract  

The increment of heat capacity at the glass transition for semi-crystalline poly(ethylene terephthalate) (PET) observed by temperature-modulated differential scanning calorimetry (TMDSC) shows significant deviations from a simple crystalline/amorphous two-phase model. Introduction of a rigid amorphous fraction, which is non-crystalline but which also does not participate in the normal glass transition, allows a much better description of the transition behaviour in semi-crystalline PET. Certain questions arise such as what is the rigid amorphous fraction and over what temperature range do these rigid amorphous segments devitrify? These TMDSC results show that the rigid amorphous component may be treated as an interphase between amorphous and crystalline phases. This interphase does not exhibit a separate glass transition temperature at temperatures above the normal Tg. The suggestion is made that the glass transition of the rigid amorphous component occurs continually between the glass transition temperature of the amorphous phase and up to about 135C for this particular sample of PET.

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Abstract  

Recycled poly(ethylene terephthalate) (R-PET) was chain extended with pyromellitic dianhydride (PMDA) in a commercial size twin-screw reactive extrusion system. Temperature-modulated differential scanning calorimetry (TMDSC) was used to evaluate the effect of the chain extension process on the thermal transitions and crystallinity of R-PET. Reactive extruded recycled PET (RER-PET) samples were tested based on different PMDA concentration and reactive extrusion residence times. The glass transition temperature (T g) did not show a significant change as a function of PMDA addition or the extrusion residence time. Melting temperature (T m) and crystallisation temperature (T c) decreased with increasing PMDA concentration and with increasing extrusion residence time. RER-PET samples showed double melting peaks, it is believed that different melting mechanism is the reason behind this phenomenon. The crystallinity of RER-PET samples is lower than that of R-PET. RER-PET samples at constant PMDA concentration showed a decrease in crystallinity with increasing extrusion residence time. Results suggest that the reactive extrusion process is more dependent on PMDA concentration rather than reactive extrusion process residence time.

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Abstract  

Poly-L-lactic acid (PLLA) is a semi-crystalline, optically active, biodegradable, and biocompatible polymer that has been utilized extensively in biomedical applications as an implantable artificial cell scaffold material. In its crystalline form, PLLA is piezoelectric and it has been implicated in the enhancement of electromechanically induced osteogenesis in vivo. In its amorphous state, however, PLLA does not exhibit piezoelectricity. By uniaxially cold-drawing the polymer, PLLA can be endowed with varying degrees of piezoelectricity. It is important to understand the crystalline architecture of drawn PLLA so that the osteogenic potential imparted by piezoelectricity, if any, can be differentiated from the effects of sample crystallinity. In our work we investigate the induced crystallinity for samples of drawn PLLA at draw ratios between 1.0 and 5.5 by differential scanning calorimetry (DSC). As long-range molecular ordering occurs along the draw axis, we observe an increase in the average percent crystallinity up to a draw ratio of 5.0 and a slight decrease at a draw ratio of 5.5. More importantly, we observe significant heterogeneity in the crystalline content along the draw axis of standard dumbbells cut from PLLA and cold-drawn to representative draw ratios of 2.5 and 4.0. On average, the highest percent crystallinity occurs nearest the dumbbell center, but the maximum crystallinity is independent of draw ratio. Therefore, the draw ratio should not be considered a semi-quantitative estimate of localized PLLA crystallinity and point-to-point analysis of crystallinity in PLLA samples is required for constructing scaffolds with enhanced cell growth properties.

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. Chung, H-J. , Liu , Q. & Hoover , R. 2010 : Effect of single and dual hydrothermal treatments on the crystalline structure, thermal properties, and nutritional fractions of pea, lentil, and

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Liquid crystalline polymers

III. Characterization by thermo-optometry of some copolyethers containing an oxetane ring in the main chain

Journal of Thermal Analysis and Calorimetry
Authors: N. Hurduc, A. Stoleru, D. Pavel, and C. I. Simionescu

The suitabilities of thermo-optometry and differential scanning calorimetry for the characterization of certain copolyethers were compared. Under certain conditions, such polymers do not exhibit the endotherm signal corresponding to the solid/liquid crystalline transition in the DSC curves. Thermo-optometry provides evidence of these phase transitions into the liquid crystalline state, and is a very useful additional method.

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Solid-state mechanical properties of crystalline drugs and excipients

New data substantiate discovered dielectric viscoelastic characteristics

Journal of Thermal Analysis and Calorimetry
Authors: Shravan Singh Thakur, Manik Pavan Kumar Maheswaram, Dhruthiman Reddy Mantheni, Lakshmi Kaza, Indika Perara, David W. Ball, John Moran, and Alan T. Riga

Introduction Most of the active pharmaceutical ingredients (APIs) known today are crystalline. An amorphous material can be substantially more soluble than the corresponding crystalline material, and thus more readily

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Introduction Azomethines called also imines are quite often investigated as liquid crystalline (LC) compounds [ 1 – 4 ]. Azomethine bond (HC=N) incorporated into the molecular structure cause increase the length and

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