Influence of processing conditions on polymer crystallization measured by fast scanning DSC

The structural formation of polymers during processing significantly influences the mechanical properties and the temperature stability of polymer products. The analysis of structural formation by conventional thermal analysis techniques is limited because of the relatively low scanning rates. Thus, reorganization during heating changes the initial structure, and the applicable cooling rates are not representative for the applied cooling rates during production, i.e., crystallization at high supercooling cannot be investigated. To overcome these limitations, chip calorimeters with very high scanning rates have been developed. The fast scanning Flash DSC 1 based on MEMS chip-sensors allows for scanning rates up to 40,000 K s^?1. In this paper, we discuss some basic concepts of chip calorimetry in general. We then study the influence of additives and molecular modifications on the structural formation at technically relevant cooling rates. This information is crucial to adapt polymer formulation and processing conditions to specific product requirements.     

Flash DSC crystallization study of blown film grade bimodal high density polyethylene (HDPE) resins. Part 2. Non‐isothermal kinetics

Non‐isothermal ultra‐fast cooling crystallization tests were conducted on three blown film grade bimodal high density polyethylene (HDPE) resins using a fast differential scanning calorimeter, the Flash DSC. Non‐isothermal tests were performed at cooling rates between 50 and 4000°K/s, and the data were analyzed using the modified Avrami model by Jeziorny (Polymer, 1978 , 19, 1142). Non‐isothermal data were used to propose a new method named crystallization–time–temperature–superposition, and the two activation energies were obtained for each of the resins. This is very useful for obtaining theoretical crystallization kinetics data at different cooling rates, allowing its use in ultra‐fast cooling polymer processes such as blown film. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1822–1827     

Flammability and phase-transition studies of nylon 6/montmorillonite nanocomposites

Nylon 6 (PA6)/clay hybrids have been prepared using a direct melt intercalation technique by two processes. One is PA6 melt-mixing with modified clay, the other is PA6 melt-mixing with natural (Na⁺ base) clay using an ammonium salt bearing long alkyl chains as a polymer/clay reactive compatibilizer. Their structure and flammability properties are characterized by X-ray diffraction, transmission electron microscopy and cone calorimeter experiments. The results of the cone calorimeter experiments show that hybrids made by these two processes have a lower heat release rate peak and higher thermal stability than that of original PA6. Meanwhile, X-ray diffraction was used to investigate PA6/clay hybrids with various cooling histories from the melt, including medium-rate cooling (air cooling) and rapid cooling (water-quenched). In contrast to pure PA6 dominated by the α phase, the addition of clay silicate layers by these two methods favors the formation of the γ crystalline phase in PA6/clay hybrids. Flammability and phase-transition studies confirm that silicate layers added by these two methods have a similar nanoeffect and nanodispersion in the PA6 matrix.     

Structures and physical properties of rigid polyurethane foams with water as the sole blowing agent

Polyurethane rigid foams have been used for many applications such as pipelines insulation materials, automotive parts, solar water heater and construction materials[1,2], due to their desirable physical properties. Traditional rigid foam is made by the reaction of a polyol and 4,4′-diphenylmethane diisocyanate (MDI) with chlorofluorocarbons (CFCs), in particular tri- chlorofluoromethane (CFC-11) and/or HCFC-141b as blowing agents. However, the CFCs blowing agents contain halogens, whic…     

A method for bulk hydrogen analysis based on transmission and back scattering of fast neutrons

A method was proposed for bulk hydrogen analysis. It is based on simultaneous detection of transmitted fast neutrons and back scattered thermal neutrons from the investigated samples by ³He detectors. The fast neutron beams were obtained from ²⁵²Cf and Pu–Be neutron sources. The experimental set-up as well as samples preparation were described. Incident thermal neutrons beams obtained from either ²⁵²Cf or Pu–Be sources, were used to investigate the samples by neutron backscattering. The results obtained from transmission and backscattering of fast neutrons were compared and discussed. The advantage and capabilities of the proposed method were presented. The results obtained using fast neutron beams are more sensitive than those obtained using thermal neutron beams. Validation procedures were proposed to credit the results.     

Enzymatic Reactions for the Calorimetric Detection of Phenolic Compounds

This study furnished results on the enzymatic detection of phenolic compounds by means of a miniaturized heat-flow calorimeter (IC-calorimeter). Two enzymes were used: tyrosinase and peroxidase. Additionally to the investigations with the IC-calorimeter, measurements were carried out with a classical reaction calorimeter (LKB 8700) for the very slow reactions with tyrosinase. By way of contrast, the reactions with peroxidase are fast and seem more suitable for sensor application. The detection limit for the investigated phenolic compounds is of the order of 1 mmol l⁻¹ . This revised version was published online in July 2006 with corrections to the Cover Date.     

Glass Forming Properties of Benzodiazepines and Co-evaporate Systems with Poly(hydroxyethyl Methacrylate)

In the present study, we report on the thermal properties of a series of benzodiazepines. The heat of fusion varied between approximately 25 and 40 kJ mol^–1, except for oxazepam and lorazepam where dimerization in the solid state increased the heat of fusion to 78.54(±0.37) and 77.03 (±0.84)kJ mol^–1, respectively. Heating alprazolam at a low rate (0.5 K min^–1) showed that polymorphs I and II are an enantiotropic pair with a solid-solid transition at 481.4 K It was shown that all benzodiazepines could be transformed to the glassy state by cooling fused samples, irrespective of the cooling rate. The size of the relaxation endotherm accompanying the glass transition increased by heating the glassy drugs at a higher rate through T_g or by cooling the fused samples at a slower rate. The time dependence of the glass to liquid transition can be described to a good approximation as a first order transformation. The Gordon-Taylor equation was used to predict T_g of a binary mixture of temazepam, diazepam or prazepam with polyHEMA. It was shown that the predictability was acceptable as long as the drug concentration was below 10%w/w; at higher concentration, specific drug-polymer interactions causing changes in free volume of the system could not be ignored.This revised version was published online in November 2005 with corrections to the Cover Date.     

A modified accelerating rate calorimeter (ARC) with capabilities for handling gaseous samples under vacuum or an inert atmosphere

A simple modification was made to the accelerating rate calorimeter (ARC^®), which has allowed for gaseous samples to be tested without the introduction of air. The modified ARC^® can also be used to test solids, liquids, or mixtures of two phases under a particular atmospheric environment with more convenience than in the original ARC^®. After the experiment, the gaseous products and/or any unreacted gaseous sample can easily be collected for further characterization. This facilitates one's ability to understand the mechanism of the exothermal reactions. The utility of this modified ARC^® was demonstrated by examining the thermal properties and polymerization of 1,1-difluoroethylene.     

Non-adiabatic thin-film (chip) nanocalorimetry

To study the kinetics of processes on a millisecond time scale a thin-film nanocalorimeter based on a commercially available microchip (thermal conductivity vacuum gauge, TCG 3880, from Xensor Integration, NL) was constructed. The gauge consists of a submicron silicon nitride membrane with a film-thermopile and a film-heater, which are located at the 100 μm × 100 μm central part of the membrane. Controlled fast cooling is possible in addition to fast heating at essentially non-adiabatic conditions. To allow fast cooling the measurements are performed in an ambient gas atmosphere. It is proved that the maximum rate of the controlled cooling can be achieved with a gas cooling agent, rather than in a system with a solid heat-sink. The advantage of the gauge TCG 3880 is that its central heated region is small enough to be considered as a point source of the heat-flow into the gas, which essentially simplifies the calorimeter calibration. The maximum cooling rate is inversely proportional to the radius of the heated region. The gauge is placed in a thermostat with controlled gas pressure and temperature to be utilized as a device for fast scanning calorimetry of sub microgram samples with sensitivity 1 nJ/K and time resolution ca. 5 ms.     

Phosphorus Modified Cardanol: A Greener Route to Reduce VolaTile Organic Compounds and Impart Flame Retardant Properties to Alkyd Resin Coatings

Novel phosphorylated cardanol molecules based on phosphonate (PO₃CR) and phosphate (PO₄CR) functions were synthetized. Those molecules have two main actions which are described in this article: the reduction in volatile organic compounds (VOC) and the development of flame retardant (FR) properties conferred on alkyd resins used as coatings for wood specimen. Phosphorylated cardanol compounds have been successfully grafted by covalent bonds to alkyd resins thanks to an auto-oxidative reaction. The impact of the introduction of PO₃CR and PO₄CR on the film properties such as drying time and flexibility has been studied and the thermal and flame retardant properties through differential scanning calorimeter, thermogravimetric analysis and pyrolysis-combustion flow calorimeter. These studies underscored an increase in the thermal stability and FR properties of the alkyd resins. In the cone calorimeter test, the lowest pHRR was obtained with 3 wt% P of phosphate-cardanol and exhibited a value of 170 KW.m⁻², which represented a decrease of almost 46% compared to the PO_xCR-free alkyd resins. Moreover, a difference in the mode of action between phosphonate and phosphate compounds has been highlighted. The most effective coating which combined excellent FR properties and good coating properties has been obtained with 2 wt% P of phosphate-cardanol. Indeed, the film properties were closed to the PO_xCR-free alkyd resin and the pHRR decreased by 41% compared to the reference alkyd resin.     

The morphological effects upon enzymatic degradation of poly(butylene succinate-co-butylene terephthalate)s (PBST)

In this work, the enzymatic degradation of poly(butylene succinate-co-butylene terephthalate) (PBST) copolyesters was studied using the lipase from Pseudomonas (Lipase PS^®). The biodegradation behavior was found to strongly depend on the overall impacts of several important factors as the BT comonomer structure and molar content, thermal characteristics, morphology, the enzyme-substrate, and so forth. Further, the biodegraded residual film samples were allowed to be analyzed by means of gel permeation chromatography (GPC), proton nuclear magnetic resonance (¹H NMR), differential scanning calorimeter (DSC), small angle X-ray scattering (SAXS), and scanning electron microscope (SEM). On the experimental evidences, an exo-type mechanism of enzymatic chain hydrolysis preferentially occurring in the amorphous region was suggested for the PBST film samples.     

Advanced two-channel ac calorimeter for simultaneous measurements of complex heat capacity and complex thermal conductivity

The advanced construction of a two-channel ac calorimeter for simultaneous measurements of frequency-dependent complex heat capacity C(ω) and complex thermal conductivity λ(ω) is presented. In the new calorimeter, the number of interfaces with thermal-wave reflections was reduced. Thus, the new construction can be easily calibrated with higher precision and is simpler in handling than the previous one. The new construction allows to measure thermal conductivity in steady-state mode, as well as frequency-dependent complex thermal properties in ac mode, in the same measuring cell. The capabilities of this technique were demonstrated, being applied for simultaneous measurements of complex effusivity, diffusivity, heat capacity, and thermal conductivity of glycerol in the glass transition region. The so-called ac and dc thermal conductivities of glycerol were measured as a function of temperature. It was shown that the double-channel ac calorimetry is a technique, which can be used for reliable distinguishing of relaxation processes related to relaxing thermal conductivity or relaxing heat capacity.In the region apart from phase transitions, the calorimeter provides the unique possibility of simultaneous measurements of the thermal contact properties together with the sample’s thermal parameters. The improvement of the accuracy gave us the possibility to observe the thermal contact resistance, leading to a step of 1 and 5% in the temperature-modulation amplitude at the cell/sample interface in the case of liquid samples such as Apiezon™-H grease and glycerol, respectively. A step of 25% was observed in the case of a dry thermal contact between the cell and an ethylene-1-octene copolymer sample. Thus, the thermal contact resistance must be taken into account in the temperature-modulated calorimetry, especially in the case of a dry cell/sample contact.     

Thermal decomposition analysis of organic peroxides using model-free simulation

To understand better the thermal decomposition characteristics of organic peroxides, a C80 heat flux calorimeter was used and the decomposition pattern of cumene hydroperoxide and di-tert-butylperoxide were classified as auto-catalytic and n ^th order reaction, respectively. Based on the scanning results with the C80 at several differing rates of heating, the thermal decomposition behavior of organic peroxides under isothermal storage at lower temperature was simulated with a model-free simulation. Simulated results showed that the calculated conversion of cumene hydroperoxide as a function of time was in good agreement with experimental data obtained with the TAM-III high sensitivity thermal activity monitor.     

Contribution a l'etude du dosage par radioactivation du sourfre et du phosphore en tres faibles concentrations dans les metaux de tres haute purete (Aluminium,magnesium, cuivre,fer, nickel)

The chemical separation of sulphur and phosphorus from pure iron and nickel, is described. Sulphur has been determined first by irradiation in fast neutrons, then by irradiation in mixed fast and thermal neutrons. The two methods gave two different results; so, we were led to point out the same phenomenon asJ. Le Hericy had already pointed out for the determination of sulphur in copper. We found that the abnormal amounts of sulphur came from external contamination with chlorine since sulphur is then produced by the³⁵Cl(n, p)³⁵S reaction. The diffusion of³⁵S atoms (produced on the edge of the samples) explains that the concentration of sulphur decreases from the edge to the middle of the sample. We prepared samples of iron and nickel, artificially covered with ammonium chloride, and we studied the apparent concentration of sulphur as a function of the depth in these samples. Our experiences pointed out that the contamination in sulphur yielded by the (n, p) reaction, reaches very quickly the middle of the samples. This phenomenon limits the determination of sulphur by the³⁴S(n, γ)³⁵S reaction, in nickel and iron.      

Heats of immersion of clinoptilolite and its ion-exchanged forms

The heats of immersion (in water) of outgassed clinoptilolite and its ion-exchanged forms were measured with a Calve calorimeter at 30°C, and the integral heats of sorption were calculated therefrom in order to use zeolites in heating and cooling applications. The immersion and sorption heats were studied as functions of the water saturation degree and the cation contents. The changes observed in the slopes of the sorption curves at low saturation for Ca²⁺ and Mg²⁺ ion-exchanged forms were related to the thermal destruction of the heulandite-type structure.     

Highly Sensitive and Fast‐Responsive Fluorescent Chemosensor for Palladium: Reversible Sensing and Visible Recovery

The well‐known rhodamine spiro‐lactam framework offers an ideal model for the development of fluorescence‐enhanced chemosensors through simple and convenient syntheses. Herein, we report a new tridentate PNO receptor, which was introduced into a rhodamine spiro‐lactam system to develop Pd²⁺‐chemosensor RPd4 , that displayed significantly improved sensing properties for palladium. Compound RPd4 shows a very fast response time (about 5 s), high sensitivity (5 nM ), and excellent specificity for Pd²⁺ ions over other PGE ions (Pt²⁺, Rh³⁺, and Ru³⁺). In addition, RPd4 displays quite different responses to different valence states of the Pd ions, that is, very fast response towards Pd²⁺ ions but slow response towards Pd⁰, which may provide us with a convenient method for the selective discrimination of Pd species in different valence states. According to proof‐of‐concept experiments, RPd4 has potential applications in Pd²⁺‐analysis in drug compounds, water, soil, and leaf samples. Owing to its good reversibility, RPd4 can also be used as a sensor material for the selective detection and visual recovery of trace Pd²⁺ ions in environmental samples.     

Characterization of form-stable phase-change material for solar photovoltaic cooling

Solar PV panel cooling is essential to achieve maximum efficiency of PV modules. Phase-change material (PCM) is one of the prominent options to cool the panel and reduce the temperature, since PCMs have low thermal conductivity. Expanded graphite particles are used to enrich the structure and stability as well as to increase the thermal properties. In the present research work, polyethylene glycol (PEG) 1000 is used as a base material and expanded graphite for inclusive particle. A novel form-stable PEG1000/EG composite PCM mixture is prepared, using impregnation and dispersion method. Expanded graphite and PEG1000/EG sample phase compositions are investigated, using X-ray diffraction technique. No new peak is identified in the composite PCM sample. The surface morphology and structure of EG and PEG1000/EG are investigated, using scanning electron microscopy (SEM). Chemical stability analysis is done by Fourier-transform infrared spectroscopy. Thermal properties of the prepared composite PCMs are analysed by differential scanning calorimetry, thermogravimetric analysis (TGA) and KD2 pro analyser. Results show that addition of EG in various propositions (5%, 10% and 15%) enhances the thermal conductivity of PCM samples from 0.3654 to 1.7866 W mK^?1, while melting point and latent heat of fusion of PCM samples are getting reduced. TGA thermographs are used to investigate the thermal stability of the composite PCM samples. TGA curves show that loss of mass happens above the operating temperature, and it is varied with different mass ratios of EG. Characterization of the prepared composite PCM samples is compared and found that PEG1000-85%/EG-15% is the best form-stable PCM, suitable for cooling the solar PV panel as well as to improve the electrical efficiency coupled with a decrease of temperature in the range of 35 °C to 40 °C.

     

Preparation and properties of an efficient smoke suppressant and flame‐retardant agent for thermoplastic polyurethane

APP@ETA, as a new type of flame retardant, was prepared by chemically modifying ammonium polyphosphate (APP) with ethanolamine (ETA) and applied to thermoplastic polyurethane (TPU) in this study. Then, the smoke suppression properties and flame‐retardant effects of APP@ETA in TPU composites were evaluated using smoke density test, cone calorimeter test, etc. And, the thermal degradation properties of flame‐retardant TPU composites were investigated by thermogravimetric analysis/infrared spectrometry. The smoke density test results indicated that APP@ETA could obviously improve the luminous flux of TPU composites in the test with or without flame. The cone calorimeter test results showed that total smoke release, smoke production rate and smoke factor of the composites with APP@ETA were significantly decreased than those of the composites with APP. For example, when the loading of APP@ETA or APP was 12.5 wt%, the total smoke release of the sample with APP@ETA decreased to 3.5 m²/m² from 6.0 m²/m², which was much lower than that of the sample with APP, reduced by 41.7%. The thermogravimetric analysis results demonstrated that APP@ETA could decrease the initial decomposition temperature and improve the thermal stability at high temperature for TPU composites. Copyright © 2017 John Wiley & Sons, Ltd.     

Gamma-spectrometry and residual nuclide analysis of pion irradiated PbWO4 crystals

The electromagnetic calorimeter of the CMS detector at CERN, Geneva will consist of PbWO₄ crystals and be exposed to a hadron flux of 10⁶ cm^-2·s^-1, mostly pions, during its operation. We have used FLUKA and DETRA codes for advance prediction of the activation of the detector. To assess the accuracy of these calculations, a small PbWO₄ crystal was irradiated in a 345 MeV/c pion beam of the PSI to a fluence of 1.6·10¹² cm^-2. The resulting activation was measured using an HPGe-detector after cooling times varying from a few minutes to 14 months. The spectra were analyzed using the SAMPO 90 code for peak search and area determination and the SHAMAN code for radionuclide identification and quantification. The spectra were extremely complex and the first ones measured not useful due to violent peak overlap and pile-up. The number of found peaks in the spectra we analyzed varied between 841 and 128 peaks depending on the cooling time. The corresponding number of nuclides identified per spectrum varied between 116 and 15. The comparisons between the predicted time-development of the nuclide composition by FLUKA/DETRA and the analyzed results show that the activities of nuclides agree excellently for the most important nuclides and very well even for the less abundant ones. The total dose rate in the vicinity of the activated crystals, including its time dependence, is very well reproduced by the FLUKA/DETRA calculations.     

Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/Ni functionally graded materials (FGM) obtained by centrifugal-slip casting method

The paper deals with the study of latent heats of melting of three real steels (one low-alloyed steel and two chromium steels) and temperatures of liquidus, peritectic transformation and solidus of these steels. All quantities were obtained using the differential scanning calorimetry method (DSC). The Setaram MHTC (multi-high-temperature calorimeter) Line 96 device equipped with 3D DSC sensor was used for all experiments. Measurements were done in alumina crucibles under inert atmosphere of pure argon. Controlled heating and cooling of steel samples was conducted at the rate of 5 K min^?1. All investigated quantities were also calculated using the Thermo-Calc software package with the use of the Thermo-Calc Fe-based alloys (TCFE) database. Comparison and discussion of experimental and calculated data was performed, and very good agreement was observed. The largest difference between measured and calculated values was 18 J g^?1 for latent heat of melting and up to 2 °C for all investigated temperatures of phase transformation, except for one temperature of peritectic transformation.