Synthesis and physical properties of lipid-based poly(ester-urethane)s,I: Effect of varying polyester segment length

Four aliphatic thermoplastic poly(ester-urethane)s (PEUs) with similar molecular weights but varying polyesters molecular weight (534–1488 g/mol) were prepared from polyester diols, obtained by melt condensation of Azelaic acid and 1,9-Nonanediol, and 1,7-heptamethylene di-isocyanate (HPMDI) all sourced from vegetable oil feedstock. The thermal, and mechanical properties, and crystal structure of PEUs were investigated using DSC, TGA, DMA, tensile analysis and WAXD. For sufficiently long polyester chain, WAXD data indicated no hydrogen bonds polyethylene (PE)-like crystalline packing and for short polyester chains, small crystal domains with significant H-bonded polyamide (PA)-like packing. Crystallinity decreased with decreasing polyester molecular weights. The polymorphism of PEUs and consequently their melting characteristics were found to be largely controlled by polyester segment length. TGA of the PEUs indicated improved thermal stability with decreasing polyester chain length, suggesting a stabilization effect by urethane groups. Mechanical properties investigated by DMA and tensile analysis were found to scale predictably with the overall crystallinity of PEUs.     

Diminishing Marginal Utility of Cooling Rate Increase on the Crystallization Behavior and Physical Properties of a Lipid Sample

It is well established that variation of the rate of cooling (r) of a lipid sample is an effective tool to influence the crystallization process and effect changes in network structure and physical functionality. However, the extent of the physical changes does not always justify the extent to which the cooling rate must be altered. It is therefore important to understand the rates at which marginal changes in physical functionality begin to diminish, and to understand the mechanisms which introduce such limitations. A commercially available cocoa butter alternative, Temcote (Bunge Oils, Bradley, IL), was crystallized under cooling rates varying from 0.1 to 20 °C min⁻¹. The growth mode and polymorphism of each sample was studied using DSC and X-ray diffraction (XRD). The hardness of the sample was monitored using cone penetrometry and its solid fat content (SFC) evolution was monitored using a temperature controlled pulse-NMR. The data demonstrates that the melting profile of the sample could be greatly manipulated over a relatively narrow range of cooling rates. Large increases in cooling rate increase the final SFC of the sample by approximately 6%. Doubling the cooling rate increases the hardness of the sample 50%. Variation of the cooling rate as a tool to modify physical functionality of the network was found to be effective only for cooling rates lower than 5 °C min⁻¹.     

Metrological Assurance of Optimal Technological Process Control

The effectiveness of optimal control of technological process is shown to depend on the metrological characteristics of the measuring instruments chosen to monitor the optimal settings of the variables. Methods have been developed for determining the requirements relating to the metrological characteristics of the measuring instruments employed so as to ensure that the optimization is acceptably effective.     

Modification of the Avrami model for application to the kinetics of the melt crystallization of lipids

The Avrami model was developed to model the kinetics of crystallization and growth of a simple metal system. The original assumptions of the model do not apply for high-volume-fraction crystallizing lipids, although it is incorrectly and frequently applied. A modified form of the Avrami model, wellsuited to complex lipid crystallization kinetics, is developed. It produces excellent fits to experimental data and allows the prediction of physically meaningful parameters, such as changes in nucleation rate and type, growth rate, morphology, and dimensionality. Morphological changes highlighted by time-resolved temperature-controlled polarized light microscopy support its application to crystallizing lipids. The kinetics of crystallization for six separate lipid samples were monitored by pulsed NMR, and fits were performed using the classical and modified Avrami model. In all cases, the modified model provided superior fits to the data compared with that of the classical model. The modified model supports the theory that lipids crystallize and grow into networks via very specific growth modes. Furthermore, the case is made that it is useful for interpreting crystallization kinetics of other systems such as polymer melts, which have nonconstant growth rates, dimensionalities, and nucleation conditions, and whose growth become diffusion-limited within specific regimes.     

Separation and Quantification of Vegetable Oil Based Polyols by High Performance Liquid Chromatography with Evaporative Light Scattering Detection

Polyols with terminal primary alcohol functionalities were obtained from canola oil via an ozonolysis and hydrogenation process. A high performance liquid chromatography (HPLC) method with evaporative light scattering detection (ELSD) was developed for separating and quantifying the polyol products. Linear calibration curves were obtained for the mono-ol, diol and triol components with correlations (r ²) above 0.98. According to the standard curve, the content of mono-ol, diol and triol can be obtained from their HPLC-ELSD chromatograms.     

Calculation of Heat Transfer in Nanosized Heterostructures

Russian Microelectronics - We calculate the temperature regime in nanosized AlAs/GaAs binary heterostructures. When modeling the heat transfer in nanocomposites, it is important to take into...     

Ion–Electron Recombination and Heat Fluxes in High-Frequency Ion Thrusters

Technical Physics Letters - Heat fluxes emitted from plasma to the surface of structural elements of high-frequency (HF) ion thrusters with perforated electrodes of the ion-optical system have been...     

Semi‐ and full‐interpenetrating polymer networks based on polyurethane produced from canola oil and poly(methyl methacrylate)

Semi‐ and full‐interpenetrating polymer networks (IPNs) were prepared using polyurethane (PUR) produced from a canola oil‐based polyol with primary terminal functional groups and poly(methyl methacrylate) (PMMA). The properties of the material were studied and compared using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and tensile measurements. The morphology of the IPNs was investigated using atomic force microscopy (AFM). Semi‐IPNs demonstrated different thermal mechanical properties, mechanical properties, phase behavior, and morphology from full IPNs. Both types of IPNs studied are two‐phase systems with incomplete phase separation. However, the extent of phase separation is significantly more advanced in the semi‐IPNs compared with the full IPNs. All the semi‐IPNs exhibited higher values of elongation at break for all proportions of acrylate to polyurethane compared with the corresponding full IPNs. These differences are mainly due to the fact that in the case of semi‐IPNs, one of the constituting polymers remains linear, so that it exhibits a loosely packed network and relatively high mobility, whereas in the case of full IPNs, there is a higher degree of crosslinking, which restricts the mobility of the chains. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Physical properties of new polyurethanes foams from benzene polyols synthesized from erucic acid

High density triol‐based polyurethane (PU) foams were developed from aromatic triol isomers prepared from erucic acid. The triol monomers were crosslinked with 4,4′‐diphenylmethane diisocyanate (MDI) into PU foams. The foam's properties were studied by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The foams were analyzed for closed cell content and compression strength. The effect of the benzene ring in the polyol structure on the physical properties of these new PU foams was compared with high density foams made from aliphatic polyols originating from canola oil. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010