Activation Energy For Thermal Destruction Research Articles

Increasing the Service Life of Marine Transport Using Heat-Resistant Polymer Nanocomposites.

This paper presents the technological aspects of increasing the thermal stability of polymers, with epoxy binder used to form the polymer materials. Polyethylene polyamine was used to crosslink the epoxy binder. To ensure the thermal stability of the polymer, nanodispersed condensed carbon with a dispersion of 10-16 nm was used. The research into nanocomposites under the influence of elevated temperatures was carried out using the "Thermoscan-2" derivatograph. Complex studies of thermophysical properties were carried out, according to the results of which the optimal content of nanofiller (0.050 pts.wt.) was determined. At the same time, this particular polymer was characterized by the following properties: temperature of the beginning of mass loss-T0 = 624.9 K; final temperature of mass loss-Tf = 718.7 K; relative mass loss-εm = 60.3%. Research into the activation energy of thermal destruction was performed to determine the resistance to the destruction of chemical bonds. It was proved that the maximum value of activation energy (170.1 kJ/mol) is characterized by nanocomposites with a content of nanodispersed condensed carbon of 0.050 pts.wt., which indicates the thermal stability of the polymer.

Investigation of the modifier 2-benzofuran-1,3-dione content effect on the heat resistance of epoxy composites

The technological aspects of modification of epoxy oligomer DER – 331 to provide improvement of thermophysical characteristics of composite materials and protective coatings based on them are presented. Cold-cured triethylenetetramine TETA hardener was used to crosslink the epoxy binder (q = 10 parts by weight per 100 parts by weight of DER-331 epoxy resin). Thermogravimetric (TGA) and differential thermal (DTA) analysis was performed to study modified composites under the influence of elevated temperatures. A mathematical calculation of the values of the activation energy of thermal destruction to determine the resistance to destruction of chemical bonds under the influence of temperature factor.

Thermal stability of UV-cured vegetable oil epoxidized acrylate-based polymer system for 3D printing application

Fabrication of sustainable photo-cured vegetable oil epoxidized acrylates were performed with two distinct methods using stereolithographic (SLA) 3D printer set up and UV-LED lamp. Two reactive monomers of 1,6-hexanediol diacrylate and trimethylolpropane triacrylate were selected to adjust the 3D printing conditions and improve thermal properties of the photocured polymer. Thermal destruction was preformed using thermogravimetric analysis (TGA) set up combination with FTIR sensor to investigate decomposition products. The glass transition of the polymer was determined using modulated differential scanning calorimetry (MDSC). The obtained results show that addition of appropriate reactive comonomers can increase glass transition temperature by 10°C, thermal degradation temperature by 28°C, and also decrease necessary resin photocuring time by almost a half from 4 sec up to 2 sec. Thermal destruction kinetics investigation by Friedman method revealed that addition of the reactive comonomers increases necessary activation energy for thermal destruction by 10% with UV-LED lamp, while curing resin with SLA printer further increases activation energy by 25%. The 3D printed resin release less hazardous gases and more CO2.

Obtaining and Investigation of the β-Cyclodextrin Inclusion Complex with Vitamin D 3 Oil Solution.

Background. The research results of fat-soluble vitamin D3 (cholecalciferol) encapsulation with β-cyclodextrin have been presented in this work. The vitamin D3 inclusion complex with β-cyclodextrin was obtained under microwave radiation. The surface morphology of obtained clathrate inclusion complexes was described with the help of a scanning electron microscope. The thermographic measurement results on a differential scanning calorimeter have been presented. The activation energy of the β-cyclodextrin : vitamin D3 clathrate complex thermal oxidative destruction reaction was calculated. The clathrate thermal destruction kinetic parameters were determined. The inclusion complex spectral properties were characterized by IR-Fourier and 1H and 13C NMR spectroscopy. The existence of β-cyclodextrin inclusion complex with vitamin D3 in a 2 : 1 ratio was confirmed by the experimental results. The activation energy of thermal destruction of the inclusion complex of β-cyclodextrin with vitamin D3 was calculated using four different methods.

Heterogenization of metalorganic catalysts of olefin polymerization and evaluation of active site non‐uniformity

AbstractHeterogenized activators ‐ “support‐H2O/AlR3” (where R=Me, iBu, support=montmorillonite, zeolite), synthesized directly on the support, form with metallocenes metal alkyl complexes highly active in olefin polymerization without the use of commercial methylaluminoxane (MAO). It was shown by the method of temperature programmed desorption with the application of mass‐spectrometry (TPD‐MS) that the aluminumorganic compound in support‐H2O/AlR3 is in general similar to the structure of commercial MAO. The heterogenization of Zr‐cenes on support‐H2O/AlR3 is accompanied by the appearance of the energy non‐uniformity of active sites. The activation energy of thermal destruction of active Zr‐C bonds in the active sites of prepared catalysts changes in the range from 25 to 32 kcal/mol.

A HEATING BLOCK SYSTEM FOR STUDYING THERMAL DEATH KINETICS OF INSECT PESTS

A novel heating block system to provide rates of temperature increase between 0.2 and 28°C/min was developed for investigating thermal death kinetics of insect pests. The finite element method was used to analyze heat transfer through the block system and during the heating of fifth-instar codling moths (Cydia pomonella L.). Measured heating rates of the block agreed with finite element predictions, and the maximum temperature difference in the testing zone was < 0.2°C at the most rapid heating of 28°C/min. Simulated temperature in the codling moth larva during 20°C/min heating to 50°C lagged behind the block temperature by a maximum of 4.6°C in the testing zone. This lag was reduced to less than 0.6°C after 30 s of holding. The temperature differential decreased with decreasing heating rate and insect size. Experiments were conducted to determine the thermal kinetics of the fifth instar codling moth at temperatures between 48 and 52°C after heating by this block system at 20°C/min. Activation energy for thermal destruction of the larvae was determined to be 499 kJ/mol, a much higher value than that for loss of fruit quality (~100 kJ/mol) due to heat treatment. The heating system can potentially be used as an effective tool to experimentally establish thermal kinetics and thermal-death-time curves for different insect pests. These values can then be used to develop appropriate quarantine treatment protocols for heat-based pest control.

Study on the energy distribution of active sites in heterogeneous Ziegler-Natta catalysts

New method of investigation of active sites non-uniformity was developed. The method is based on mass-spectrometric study of temperature programmed desorption (TPD) products from the catalyst surface at initial stages of olefin gasphase polymerization. The conditions of polymerization allowed to obtain the short macrochains on catalyst surface. Two well-resolved intense maxima in the temperature ranges of 180–210°C and 280–320°C on the TPD curves from SiO2/TiCl4/AlEt2Cl catalyst surface after polymerization were observed in a result of thermal destruction of active Ti-C bonds and the evolution of hydrocarbon molecules of different length (up to 14 monomer units in chain). One may conclude that in this catalyst there are at least two types of active sites varying in the activation energy of thermal destruction of Ti-C bonds. The distribution of active sites over activation energy of Ti-C bond thermal destruction was calculated.

Study of energy distribution of active sites in heterogeneous Ziegler-Natta catalysts

New method of investigation of active sites non-uniformity was developed. The method is based on mass-spectrometric study of temperature programmed desorption (TPD) products from the catalyst surface at initial stages of olefin gasphase polymerization. The conditions of polymerization allowed to obtain the short macrochains on catalyst surface. Two well-resolved intense maxima in the temperature ranges of 180–210°C and 280–320°C on the TPD curves from SiO2/TiCl4/AlEt2Cl catalyst surface after polymerization were observed in a result of thermal destruction of active Ti-C bonds and the evolution of hydrocarbon molecules of different length (up to 14 monomer units in chain). One may conclude that in this catalyst there are at least two types of active sites varying in the activation energy of thermal destruction of Ti-C bonds. The distribution of active sites over activation energy of Ti-C bond thermal destruction was calculated.

Thresholds for focal ultrasonic lesions in rabbit kidney, liver, and testicle.

Thresholds are reported for production of focal ultrasonic lesions in rabbit liver, kidney, and testicle for 2 and 6 MHz, singe pulse exposures ranging in length from 1 to 60 s. Intensity-exposure time thresholds are found to be nearly independent of frequency as shown in earlier work for brain tissue. The results compare favorably with a thermal model for prediction of thresholds which considers the activation energy for thermal destruction of the tissues, their thermal diffusivity, absorption coefficients, time and intensity of exposure, and baseline temperature. All thresholds are of the same magnitude as those previously reported for brain. Those differences which are observed can be explained by the thermal model for the action of ultrasound on tissue.

Engineering factors in single‐cell protein production. II. Spray drying and cell viability

AbstractOne important economical method for producing singlecell protein is to spray dry the cultured cells. This study presents some preliminary data on the effects of spray drying on cell viability. Under conditions similar to those for the production of spray‐dried milk, 4–5 log cycles destruction occurred. The results indicate that, the activation energy for thermal destruction of yeast was reduced from the normal heat treatment value of 84 kcal/°K mole to about 38 kcal/°K mole.