Mechanical and Thermal Properties of Eva Blended with Biodegradable Ethyl Cellulose

In this study, biodegradable blend of Poly (Ethylene-co-Vinyl Acetate) (EVA) and Ethyl Cellulose (EC) were prepared. Ethylene vinyl alcohol (EVOH) copolymer was used as an interfacial compatibilizer to enhance adhesion between EVA and EC. The melt blended compatibilized biocomposites were examined for mechanical and thermal properties as per the ASTM standards. It has been found that the EC has a reinforcing effect on EVA leading to enhanced tensile strength and also impart biodegradability. Thus, a high loading of 50% EC could be added without compromising Much on the mechanical properties. Analysis of the tensile data using predictive theories showed an enhanced interaction of the dispersed phase (EC) and the matrix (EVA). The compatibilizing effects of EVOH on these blends were confirmed by the significant improvement in the mechanical properties comparable with neat EVA as also observed by SEM microscopy. The TGA thermograms exhibits two-stage degradation and as EC content increases, the onset temperature for thermal degradation reduces. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 116: 1044-1056, 2010

Thermal decomposition studies on copolyurethanes based on hydroxyl terminated polybutadiene and poly(12-hydroxy stearic acid-co-TMP) ester polyol

Thermal degradation of copolyurethanes based on hydroxyl terminated polybutadiene (HTPB) and poly(12-hydroxy stearic acid-co-TMP) ester polyol (PEP) with varying compositions has been studied by thermo-gravimetric and pyrolysis-GC techniques. The copolyurethanes were found to decompose in multiple stages and the kinetic parameters were found to be dependent on the method of their evaluation. The activation energy for the initial stage of decomposition was found to increase, and for the main stage decreases with the increase in PEP content. The pyrolysis-GC studies on the ammonium perchlorate filled copolyurethanes (solid propellants) showed that the major products during the pyrolysis were C-2, C-3 hydrocarbons and butadiene. The amount of C-2 fraction in the pyrolyslate increased with solid loading, as well as with the HTPB content in the copolyurethanes. A linear relationship apparently exists between the amount of C-2 fraction and the burn rates of the solid propellants. (C) 2000 Elsevier Science Ltd. All rights reserved.

Synthesis, structural characterization, thermal studies and chain dynamics of poly(methacrylonitrile peroxide) by NMR spectroscopy

Poly(methacrylonitrile peroxide) (PMNP) has been synthesized from methacrylonitrile by free radical initiated oxidative polymerization and characterized by different spectroscopic methods. NMR spectroscopy confirmed the alternating copolymer structure with labile peroxy bonds in the main chain. The extreme instability of PMNP was noted from FTIR spectroscopy. Thermal degradation studies by using differential scanning calorimetry and thermogravimetry have revealed that PMNP degrades highly exothermically and the heat of degradation, 42.5 kcal mol−1, is of the same order as that reported for other vinyl polyperoxides. Mass spectral fragmentation pattern under electron impact (EI) condition has also been investigated. The mechanism of the primary exothermic degradation has been substantiated by thermochemical calculations. The chain dynamics of the polyperoxide chain has been studied by means of 13C spin–lattice relaxation times (T1) of the main chain as well as the side chain carbons. The temperature dependence of the spin–lattice relaxation times shows that the PMNP is more flexible compared to the analogous poly(styrene peroxide).

Kinetics of catalytic degradation of polycarbonate in benzene

The degradation kinetics of polycarbonate [poly(bisphenol A carbonate)] in benzene catalyzed by commercial (rutile) TiO2 (BET surface area = 11 m(2)/g), anatase TiO2 (156 m(2)/g), and 1 atom % Pt/TiO2 (111 m2/g), prepared by the solution combustion technique, was investigated at various temperatures (230-280 degreesC) and 50 atm. The time evolution of the molecular weight distribution (MWD) was determined by gel permeation chromatography (GPC) and modeled with continuous distribution kinetics to obtain the degradation rate coefficients. The rate coefficients for the catalytic degradation of polycarbonate increased by factors of 20, 3.5, and 1.3 compared to the rate coefficients for thermal degradation when catalyzed by nanosized TiO2 anatase, Pt/TiO2 anatase, and commercial TiO2, respectively, at 280 degreesC. The increased catalytic activity of combustion for synthesized TiO2 and 1% Pt/TiO2 might be due to the increased acidity and BET surface area. The activation energies, determined from the temperature dependencies of the rate coefficients, were 16.3, 21.5, and 39.1 kcal/mol for commercial TiO2, combustion-synthesized Pt/TiO2, and anatase TiO2, respectively.

Investigation of Degradation Behavior of Polymer on Surface of Film Due to the Existence of Monochromatic X-ray

Degradation and its temperature dependence of poly(methyl methacrylate) (PMMA) in the blend film of PMMA/SAN were investigated via ire-situ X-ray photoelectron spectroscopy(XPS). The results show that thermal degradation of PMMA takes place at 185, 130, 80 degrees C and even room temperature due to the existence of monochromatic X-ray. Furthermore, the degradation rate depends crucially on the experiment temperature.

Chemical effects of cationic surfactant and anionic surfactant used in organically modified montmorillonites on degradation and fire retardancy of polyamide 12 nanocomposites

Three kinds of organically modified Na+-montmorillonites (OMMTs), including two kinds of octadecylammonium modified montmorillonite with different contents of octadecylammonium and a kind of sodium dodecylsulfonate (SDSo) modified montmorillonite, were used to prepare polyamide 12 (PA12)/OMMT nanocomposites. Effects of the modifiers on degradation and fire retardancy of PA12/OMMT nanocomposites were investigated. Acid sites formed in cationic surfactant modified MMT via Hoffman decomposition could accelerate degradation of PA12 at high temperature. However, catalytic effect of the acid sites on carbonization of the degradation products promoted char barrier formation, which reduced heat release rate (HRR). Higher content of cationic surfactant in OMMT is beneficial to fire retardancy of PA12 nanocomposites and the dispersion states of OMMT have assistant effects. In contrast, Na+-montmorillonite (Na-MMT) and anionic surfactant modified MMT (a-MMT) could not form acid sites on the MMT layers; in this case, fire retardancy of PA12/Na-MMT appears to have no improvement and PA12/a-MMT appears to have limited improvement.

Thermal analysis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) irradiated under vacuum

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was irradiated by Co-60 gamma-rays (doses of 50, 100 and 200kGy) under vacuum. The thermal analysis of control and irradiated PHBV, under vacuum was carried out by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The tensile properties of control and irradiated PHBV were examined by using an Instron tensile testing machine. In the thermal degradation of control and irradiated PHBV, a one-step weight loss was observed. The derivative thermogravimetric curves of control and irradiated PHBV confirmed only one weight-loss step change. The onset degradation temperature (T-o) and the temperature of maximum weight-loss rate (T-p) of control and irradiated PHBV were in line with the heating rate (degreesC min(-1)). T-o and T-p of PHBV decreased with increasing radiation dose at the same heating rate. The DSC results showed that Co-60 gamma-radiation significantly affected the thermal properties of PHBV. With increasing radiation dose, the melting temperature (T-m) of PHBV shifted to a lower value, due to the decrease in crystal size. The tensile strength and fracture strain of the irradiated PHBV decreased, hence indicating an increased brittleness.

THERMAL-DECOMPOSITION PROCESSES OF SOME ELECTRICALLY CONDUCTING POLYMERS INVESTIGATED BY DIRECT PYROLYSIS MASS-SPECTROMETRY

Thermal decomposition processes of poly(thio-1,4-phenylene) (PPS), polythiophene (PT) and polyaniline (PAn) were investigated by direct pyrolysis EI or CI mass spectrometry (DPMS). They can provide up to heptemer pyrolynates and give some structure properties. The results indicate that the thermal degradation all undergoes in radical decomposition, PPS pyrolyzes into linear and cyclic oligmers, but PT and PAn pyrolyze only into linear oligmers.

Assessment of the degradation of Aspirin by Differential Scanning Calorimetry (DSC)

Purpose. To study thermal stability of Aspirin and define thermal events that are associated with the thermal degradation of aspirin. Methods. Experiments were performed using a DSC 823e (Mettler Toledo, Swiss). Aspirin is prone to thermal degradation upon exposure to high temperatures. The melting point of aspirin is 140.1±0.4ºC (DSC). Aspirin has been examined by heating samples to 120ºC, 155ºC and 185ºC with subsequent cooling to -55ºC and a final heating to 155ºC. Although different heating and cooling ranges have been used, only results obtained at a rate of 10ºC/min will be presented. All runs where conducted in hermetically sealed pans. Results. Upon heating the sample to 120ºC no significant thermal event can be detected. After cooling the sample and reheating a glass transition can be observed at ~-8ºC, followed by the melting of aspirin at ~139ºC. By heating the sample to 155ºC melting of aspirin has been detected at ~139ºC. On cooling and subsequent heating a glass transition occurs at ~-32ºC, together with a broad crystallisation (onset at ~38ºC and peak maximum at ~57ºC) followed by a broad melting with an onset at 94ºC and peak maximum at ~112ºC. Finally, by heating the sample to 185ºC melting at ~ 139ºC was observed, and upon cooling and reheating a glass transition was detected at ~-26ºC and no further events could be recorded. Conclusions. This research demonstrates that the degradation steps of Aspirin depend on the thermal treatment. The main degradation products of different thermal treatments are currently unknown it is clear that acetic acid, which is one of the degradation products, acts as an antiplasticiser by lowering the glass transition temperature. In addition, due to the presence of the degradation products in liquid form (observed by hot stage microscopy), Aspirin is still present in the sample and recrystallises during the second heating step and melts at much lower temperatures.

Effect of poly ethylene glycol on the mechanical and thermal properties of bioactive Poly (ε–caprolactone) melt extrudates for pharmaceutical applications

This paper investigates the effects of polyethylene glycol (PEG), on the mechanical and thermal properties of nalidixic acid/ploy ε-caprolactone (NA)/PCL blends prepared by hot melt extrusion. The blends were characterized by tensile and flexural analysis, dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis and X-ray diffraction. Experimental data indicated that the addition of NA caused loss of the tensile strength and toughness of PCL. Thermal analysis of the PCL showed that on addition of the thermally unstable NA, thermal degradation occurred early and was autocatalytic. However, the NA did benefit from the heat shielding provided by the PCL matrix resulting in more thermally stable NA particles. Results show that loading PEG in the PCL had a detrimental effect on the tensile strength and toughness of the blends, reducing them by 20-40%. The partial miscibility of the PCL-PEG system, causes an increase in Tg. While increases in the crystallinity is attributed to the plasticisation effect of PEG and the nucleation effect of NA. The average crystal size increased by 8% upon PEG addition.

Determination of the degradation kinetics of anthocyanins in a model juice system using isothermal and non-isothermal methods

The effect of temperature on the degradation of blackcurrant anthocyanins in a model juice system was determined over a temperature range of 4–140 °C. The thermal degradation of anthocyanins followed pseudo first-order kinetics. From 4–100 °C an isothermal method was used to determine the kinetic parameters. In order to mimic the temperature profile in retort systems, a non-isothermal method was applied to determine the kinetic parameters in the model juice over the temperature range 110–140 °C. The results from both isothermal and non-isothermal methods fit well together, indicating that the non-isothermal procedure is a reliable mathematical method to determine the kinetics of anthocyanin degradation. The reaction rate constant (k) increased from 0.16 (±0.01) × 10−3 to 9.954 (±0.004) h−1 at 4 and 140 °C, respectively. The temperature dependence of the rate of anthocyanin degradation was modelled by an extension of the Arrhenius equation, which showed a linear increase in the activation energy with temperature.

Thermal and structural properties of commercial dental resins light-cured with blue emitting diodes (LEDs)

We have investigated the thermal and structural properties of different commercial dental resins: Filtek(TM) Z-350, Grandio(A (R)), Tetric Ceram(A (R)), and TPH Spectrum(A (R)). The purpose of the present study was to evaluate quantitatively the photo-polymerization behavior and the effect of filler contents on the kinetic cures of the dental resins by using Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FT-IR) techniques. We have successfully obtained the low and high glass transition T (g) values of the dental composite resins from DSC curves. It was also observed a good agreement between the both T (g) values, activation energies from thermal degradation, and the degree of conversion obtained for all samples. The results have shown that Tetric Ceram(A (R)) dental resin presented the higher T (g) values, activation energy of 215 +/- A 6 KJ mol(-1), and the higher degree of conversion (63%) when compared to the other resins studied herein.

Studies on the properties and the thermal decomposition kinetics of natural rubber prepared with calcium chloride

To evaluate calcium chloride coagulation technology, two kinds of raw natural rubber samples were produced by calcium chloride and acetic acid respectively. Plasticity retention index (PRI), thermal degradation process, thermal degradation kinetics and differential thermal analysis of two samples studied. Furthermore, thermal degradation activation energy, pre-exponential factor and rate constant were calculated. The results show that natural rubber produced by calcium chloride possesses good mechanical property and poor thermo-stability in comparison to natural rubber produced by acetic acid.

Thermal and mechanical properties of ultrasonically treated wool

Wool fabrics, ultrasonically treated in various chemical conditions and for different time durations, were analysed for thermal properties by thermo-gravimetric analysis and differential scanning calorimeter, in comparison with the untreated fabric. Fabric mechanical properties, such as bending and tensile performance, and changes in fibre morphology were also evaluated before and after ultrasonic treatment.It is found that wool treated with ultrasonics at the appropriate time, has less mass loss and a higher thermal degradation temperature than that without ultrasonic treatment or with prolonged ultrasonic treatment. Resistance to thermal degradation is reduced when wool is ultrasonically treated in the presence of alkali. Differential scanning calorimeter analysis shows that while ultrasonic treatment has little effect on fibre crystallinity, an appropriate treatment can provide wool with increased water absorption. Ultrasonic treatment stiffens wool fabric to some extent when the treatment time is prolonged. The addition of detergent alone to the ultrasonic bath has little effect on fabric tensile behaviour, whereas a treatment with both detergent and alkali produces severe fibre damage and significant loss of fabric tensile strength.

Enhanced thermal stability and lifetime of epoxy nanocomposites using covalently functionalized clay: Experimental and modelling

The present work aims at finding a relationship between kinetic models of thermal degradation process with the physiochemical structure of epoxy-clay nanocomposites in order to understand its service temperature. In this work, two different types of modified clays, including clay modified with (3-aminopropyl)triethoxysilane (APTES) and a commercial organoclay, were covalently and non-covalently incorporated into epoxy matrix, respectively. The effect of different concentrations of silanized clay on thermal behaviour of epoxy nanocomposites were first investigated in order to choose the optimum clay concentration. Afterwards, thermal characteristics of the degradation process of epoxy nanocomposites were obtained by TGA analysis and the results were employed to determine the kinetic parameters using model-free isoconversional and model-fitting methods. The obtained kinetic parameters were used to model the entire degradation process. The results showed that the incorporation of the different modified clay into epoxy matrix change the mathematical model of the degradation process, associating with different orientations of clay into epoxy matrix confirming by XRD results. The obtained models for each epoxy nanocomposite systems were used to investigate the dependence of degradation rate and degradation time on temperature and conversion degree. Our results provide an explanation as to how the life time of epoxy and its nanocomposites change in a wide range of operating temperatures as a result of their structural changes.