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Silk fibroin (SF), a unique and promising natural material extracted from silkworm, has gained much attention for its use as biomedical material, because of its biocompatibility, biodegradability, and nontoxicity. Despite its strength, SF alone is not appropriate because of its poor flexibility. Thermoplastic polyurethane (TPU) is a very desirable material for medical applications because of its flexibility. A solution to the problem of SF’s poor flexibility can be achieved by mixing flexible TPU with SF. The aim of this work was to examine the influence of FS content on the physical and thermal properties of TPU/FS blends. Blends of SF and TPU were prepared with melt mixing of TPU with 5, 10, 15, and 20 wt% of SF in a laboratory Brabender kneading chamber. The specimens of the neat components and their blends were moulded in a hydraulic press. The structural characteristics, thermal, and viscoelastic properties of neat TPU, SF and their blends (TPU/SF blends) were examined by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). The FTIR results showed that the SF was successfully introduced to TPU matrix. Results obtained with DSC and DMA measurements showed that, when the SF content increased in the TPU/SF blends, the Tg, expressed as Teig, Tmg, and Tefg of the TPU, slightly shifted to lower temperature due to the incorporation of the amorphous phase of FS (aspartic acid) in the amorphous phase of TPU, and mobility of polymer chains increased. The melting temperature (Tm), expressed as Teim, Tpm, and Tefm, decreased because of the less organised crystal structure with the addition of SF. Thermal stability was determined by TGA, which showed that, with the addition of SF, the thermal stability decreased because of the lower thermal stability of SF. [ABSTRACT FROM AUTHOR]

In this work, the influence of multiwalled carbon nanotubes (MWCNT) and carbon nanotubes modified with COOH groups (MWCNT-COOH) on the structure and properties of thermoplastic polyurethane (PU) were investigated. The samples of nanocomposite were prepared from a mixture of polyurethane and MWCNT in acetone by slow drying at room temperature. The effect of the addition of nanofillers on the spherulite structure of polyurethane and the distribution of the nanofillers in the PU matrix were analysed with optical polarization microscopy. Thermal properties in non-isothermal and isothermal conditions were investigated by differential scanning calorimetry (DSC). The results of contact angle measurement imply that modification of MWCNT surface with COOH groups changes its surface from hydrophobic to hydrophilic (Fig. 2 and Table 1). Optical polarization microscopy showed that the addition of both nanofillers disrupts the coarse spherulite morphology of the polyurethane matrix (Fig. 4 and Fig. 5). It was observed that, at the macro level, the modified MWCNT-COOH filler is better distributed in the PU matrix than is the MWCNT filler (Fig. 5). The DSC results showed that, in non-isothermal conditions, up to a certain amount, both nanofillers accelerate the crystallization of the soft segments of polyurethane. This effect is more pronounced in systems with MWCNT filler (Fig. 9). The results of the crystallization enthalpy during cooling showed that MWCNT filler, despite its worse distribution in the PU matrix, more significantly enhances crystallization of PU’s soft segment than does the MWCNT-COOH filler (Fig. 10). This conclusion can be ascribed to better compatibility between the nonpolar MWCNT filler and the nonpolar soft phase of the PU matrix, as well as to the previous scientific finding that functional groups at MWCNT surface decrease the nucleation effect of MWCNT. By analysing the melting peaks, it can be concluded that the PU systems with MWCNT compared to systems with MWCNT-COOH contain a higher proportion of less ordered crystalline soft phase (Fig. 11). In isothermal conditions, the MWCNT filler accelerates crystallization more significantly than does the MWCNT-COOH filler (Fig. 16). [ABSTRACT FROM AUTHOR]

The widespread use of thermal analysis (TA) by scientists as a laboratory technique carries with it a working vocabulary. This document is intended to provide those working in the field with a consistent set of definitions to permit clear and precise communication as well as understanding. Included in the document are the definitions of 13 techniques, 54 terms within the glossary, as well as symbols and units. [ABSTRACT FROM AUTHOR]

The document gives definitions of terms met in the conventional thermal and thermomechanical characterisation of polymeric materials. [ABSTRACT FROM AUTHOR]

Quality sportswear is evaluated through its thermal physiological and ergonomic comfort. In this paper we study the correlation of the mechanical properties of knitwear garments and the ergonomic comfort of clothes. Sportswear is made from different types of materials that can visually seem the same, but when it comes to the mechanical properties that are significantly associated with the fitting of clothes and its deformation during use, there can be significant differences between them. To create a pair of women's cycling pants, the following two kinds of knitwear with the same structural characteristics but with different raw material composition, were used. Two models of women's cycling pants were made from these kinds of knitwear. For making both models of pants, the cutting parts of the same design were used, but with different combinations of knitwear of different elasticity for individual cutting parts, for the purpose of reaching a better ergonomic comfort. The correlation of the mechanical properties of knitwear and the ergonomic comfort of women's cycling trousers was determined through trial wearing and subjective evaluation. Taking into account the study of literature that deals with the issue of comfort sportswear, the mechanical and thermal properties of the used knitwear, and finally the realized trial wearing of female cycling pants, it can be concluded that, in addition to clothing design, the mechanical properties of knitwear and extensibility of materials have a large impact on the ergonomic comfort of the used clothing. Tests have shown that a large contact pressure on certain parts of the body can be reduced by using higher tensile knitwear, as shown in this paper for Model 2. The structural model of cycling pants for Model 2 is the same, and has a significantly increasing functionality and comfort when for the side part of pants instead of ACG-S knitwear we use the ACG-C knitwear, which has a higher extensibility in the transverse direction. [ABSTRACT FROM AUTHOR]

Properties of poly(L-lactide) (PLLA) were modifi ed using olive stone fl our (OSF) and citrate plasticizers such as tributyl citrate (TBC) and acetyltributyl citrate (TBAC). The properties of blends and composites prepared by applying different processing procedures were investigated. The results of differential scanning calorimetry (DSC) indicate that thermal properties of the samples were greatly affected by processing procedure, without any difference among the chosen plasticizers. Thus, the research has been continued with acetyltributyl citrate. OSF slightly affects thermal properties of PLLA; the greatest infl uence is on the crystallization of PLLA. Plasticizer lowers the value of thermal transition temperatures, but increases the crystallinity of PLLA. Non-isothermal thermogravimetric analysis (TGA) showed that addition of OSF deteriorates the thermal stability of PLLA while TBAC improves it. Scanning electron microscope (SEM) images confi rmed weak interactions between PLLA and OSF and no infl uence of TBAC on it. According to Fourier transform infrared spectroscopy (FT-IR) spectrums in plasticized composites only hydrogen bonds were formed. OSF reduces the fl exibility and the strength of PLLA while TBAC increases the fl exibility and signifi cantly reduces the strength of PLLA. Thermal properties of the investigated blends and composites, especially the process of crystallization and melting of PLLA crystals have been affected by ageing. Biodegradation of prepared PLLA samples in the soil was increased substantially by addition of OSF and TBAC, but TBAC has a lower infl uence. The migration of plasticizer at elevated temperatures increases with time exposure to given temperatures. In such conditions OSF facilitates migration of TBAC from the investigated composites. Migration of plasticizer from samples immersed in food-simulating solvents increases with time exposure to food-simulating solvents. Therefore, thermal properties of the investigated samples have been changed. [ABSTRACT FROM AUTHOR]

The infl uence of repeated extrusions of polypropylene (PP) on its thermal properties is investigated by differential scanning calorimetry and non-isothermal thermogravimetric analysis. PP is extruded six times on a laboratory extruder at a temperature of 190 °C and screw speed of 120 min-1. Extruded samples show a slight reduction of the melting point and the crystallization degree compared to the original PP. The non-isothermal degradation of all samples occurs through one degradation step and the extruded samples show a slightly lower thermal stability compared to the original PP. Kinetics analysis of the non-isothermal degradation of all samples was performed by isoconversional Flynn-Wall-Ozawa method. All extruded samples show higher values of activation energy compared to the original PP. Activation energy is constant in a wide range of conversion for all samples what also indicates that the non-isothermal degradation of PP occurs through one degradation step, without change of the reaction mechanism due to extrusion. Therefore, repeated extrusions under these conditions slightly worsen the thermal properties of PP and can be used for recycling its waste. [ABSTRACT FROM AUTHOR]