Pressure Differential Scanning Calorimetry Research Articles

Effect of alkylated diphenylamine antioxidants on the anti-aging properties of ester lubricants at the molecular level: Molecular simulations and experiments

A combined study of molecular simulation and experimental methods is presented for trimethylolpropane trioleate (TMPTO) with different alkylated diphenylamine antioxidants: 4,4′-dimethyldiphenylamine (DMDPA), 4,4′-dioctyldiphenylamine (ODA), and 4,4′-dinonyldiphenylamine (T558) to investigate the mobility, activity, and O2 migration of antioxidants. The solubility parameter (δ), binding energy (Ebinding), mean square displacement (MSD), hydrogen bond dissociation energy (BDE), and solubility coefficient of O2 (P) were calculated by molecular simulation. The simulation results showed that the antioxidant T558 exhibits lower mobility and better physical resistance to O2 penetration. Fourier transform infrared spectroscopy (FT-IR), 1,1-diphenylamine-2-trinitrophenylhydrazine (DPPH) radical scavenging, pressure differential scanning calorimetry (PDSC), and surface tension were investigated by experiments. The experimental results showed that antioxidant T558 with larger relative molecular mass and longer amine para-alkyl chain exhibited better antioxidant properties, which was in an agreement with simulation results. The aim of this study is to provide a molecular-level theoretical basis for the anti-ageing protection of lubricants.

Structure–Performance Relationship of Coal-Based Lubricating Base Oils and Sensitivities to Typical Additives

The relationship between the structure characteristics and performances of coal-based hydrogenation isomeric (CTL) base oil and metallocene-catalyzed coal-based poly-alpha-olefin (mPAO) base oil is clarified in this paper. CTL and mPAO were compared with typical petroleum-based and natural gas-based commercial API III and IV base oils. Pressurized differential scanning calorimetry (PDSC), the rotary bomb oxidation test (RBOT), and a four-ball friction tester were used to evaluate the oxidation stability and lubrication performance of base oils under different working conditions. The sensitivity of different base oils to typical antioxidants and extreme-pressure antiwear agents was compared. In particular, the composition and structure of CTL base oil are clearly different from GTL and mineral base oil. The coal-based CTL and mPAO base oils exhibit commendable viscosity–temperature properties, coupled with low-temperature fluidity, fire safety, and minimal evaporation loss. The lubricating properties, oxidation stability, and sensitivity to extreme-pressure antiwear agents of CTL are close to those of similar base oils. However, the sensitivity of CTL to typical antioxidants is relatively poor. In addition, compared with commercial PAO base oil, mPAO has a lower isomerization degree and fewer isomerization types. The oxidation stability and sensitivity to typical antioxidants of mPAO base oil are comparable with those of commercial PAO base oil, while its lubrication performance and sensitivity to typical extreme-pressure antiwear agents are significantly better than those of commercial PAO base oil.

Thermal decomposition characteristics of BHT and its peroxide (BHTOOH).

2,6-Di-tert-butyl-4-methylphenol (BHT) is an excellent antioxidant that is easily oxidized to 2,6-di-tert-butyl-4-hydroperoxyl-4-methyl-2,5-cyclohexadienone (BHTOOH). For the safety of BHT production and usage, it is meaningful to study the thermal stability and decomposition properties of BHT and BHTOOH. In this paper, the thermal decomposition properties of BHT and BHTOOH were compared by the mini closed pressure vessel test (MCPVT) and differential scanning calorimetry (DSC). Their kinetics of thermal decomposition were studied using thermogravimetric analysis (TGA). The thermal decomposition products of BHT and BHTOOH were analyzed by gas chromatography-mass spectrometry (GC-MS). The results show that there was no significant change in temperature pressure when BHT was warmed up under a nitrogen atmosphere, indicating that BHT was stable within 400K. The thermal decomposition reaction of BHTOOH was rapid with an initial reaction temperature of 375.2K. The initial exothermic temperature (Ti) and heat release (QDSC) of DSC were 384.9K and 865.0Jg-1, respectively. The apparent activation energies (Ea) for the thermal decomposition reactions of BHT and BHTOOH calculated by the Kissinger method were 151.8kJmol-1 and 66.07kJmol-1, respectively. The main decomposition products of BHT were isobutene and 2-tert-butyl-4-methylphenol. The thermal decomposition products of BHTOOH included BHT, 2,6-di-tert-butyl-4-ethylphenol, 3,5-di-tert-butyl-4-hydroxybenzaldehyde, 4,4'-(1,2-ethanediyl) bis [2,6-bis (1,1-dimethylethyl) phenol, etc. Based on the thermal decomposition behavior and products, the reaction pathway has been described. These results indicate that BHT is a potential thermal hazard during production, storage and application. For the safety of the chemical industry, the oxidation of BHT should be avoided.

An Experimental Study and Numerical Simulation Analysis of Thermal Oxidation Characteristics Based on Kinetic Parameters in Heavy Oil Reservoirs

In situ combustion (ISC), an efficient and economical method for enhancing heavy oil recovery in high-pressure, high-viscosity, and thermally challenged reservoirs, relies on the kinetics of crude oil oxidation. Despite an increased focus on kinetic models, there is a gap in understanding how oxidation kinetic parameters impact ISC effectiveness in heavy oil reservoirs. This study addresses this by selecting heavy oil samples from the G Block in the Liaohe oilfield and the M Block in the Huabei oilfield and conducting ramped temperature oxidation (RTO), pressure differential scanning calorimetry (PDSC), and thermogravimetric analysis (TGA) experiments. RTO detailed the thermal conversion process, categorizing oxidation into low-temperature oxidation (LTO), fuel deposition (FD), and high-temperature oxidation (HTO) stages. PDSC and TGA provided thermal characteristics and kinetic parameters. The feasibility of fire flooding was evaluated. Using CMG-STARS, an ISC model was established to analyze the impact of kinetic parameter changes. Activation energy significantly affected coke combustion, while the pre-exponential factor had a notable impact on cracking reactions. The recommended values for activation energy and the pre-exponential factor are provided. This study not only guides fire flooding experiments but also supports field engineering practices, particularly for in situ combustion in heavy oil reservoirs.

A New Antioxidant with Higher Activity at Elevated Temperature Based on Multiple Intramolecular Synergisms

AbstractA new type of multifunctional antioxidant RSSPD was designed through combining four different antioxidant fragments. Pressure differential scanning calorimetry (PDSC) tests show that RSSPD has outstanding antioxidative activity especially at high temperature compared with both the traditional antioxidants and our reported antioxidant SSPD. From the comparison with different related formulations and the density functional theory (DFT) calculations, a complicated intramolecular synergism mechanism is proposed. The intramolecular synergism between different primary antioxidants and the intramolecular synergism between primary antioxidants and secondary antioxidants can be considered as the main reasons for the high antioxidative activity of RSSPD.

Strategical design of bridged vanillic Schiff-bases as jet fuel antioxidants

Two vanillic Schiff-base antioxidants, 2-methoxy-4-(((4-(phenylamino)phenyl)imino)methyl)phenol (PPIMP) and 2-methoxy-4-(((4-(phenylamino)phenyl)amino)methyl)phenol (PPAMP), have been synthesized through the Schiff-base condensation reaction and hydrogenation to improve the thermal-oxidative stability of hydrocarbon fuels. Both novel antioxidants exhibited remarkable performance in decalin and JP-10 fuel. For example, pressurized differential scanning calorimetry (P-DSC) tests showed that adding 100 ppm of PPIMP or PPAMP to JP-10 improved the oxidation induction time from 9.5 min to 19.2 and 27.8 min, respectively. JFTOT tests showed that adding 100 ppm of either antioxidant helped alleviate JP-10 deposition. Theoretical calculations on electron properties and orbital conformation revealed that the C = N bridge in PPIMP had an electron donation effect and conjugative stabilization effect, which can stabilize intermediate antioxidant radicals and improve the antioxidants’ reactivity. The hydrogenation of C = N further enhanced the performance of PPAMP by introducing an additional antioxidant group. Therefore, both C = N and C-N in the synthesized antioxidants were found to be essential. The chemical combination of small molecular antioxidants achieves 1 + 1 > 2 synergism with the assistance of the azomethine group.

Characterization of Thermal Properties of Ruby Chocolate Using DSC, PDSC and TGA Methods

Barely explored in the prior literature, ruby chocolate was investigated in this study to explore its thermal properties. The fatty acid composition of ruby chocolate (RC) fat was determined using gas chromatography. Differential scanning calorimetry (DSC) was successfully used to determine the melting behavior and polymorphic forms of the cocoa fat and milk fat present in the RC. The oxidative stability of the fat extracted from the RC was studied with the use of pressurized differential scanning calorimetry (PDSC). The thermal behavior of the chocolate and the fat were investigated using thermogravimetry (TGA). The thermal profile and characteristics of the RC showed how the parameters compared with those of dark and milk chocolate. The melting temperature of the RC obtained by DSC was more similar to that of milk chocolate than to that of dark chocolate. Regression analysis of the PDSC data for the fat extracted from the RC was characterized by very high correlation coefficients (>0.99). It was noticed there was no statistically significant difference between the values of the activation energy (Ea) of the oxidation process for the fat extracted from the RC, obtained by the means of maximum temperature (dynamic mode) and maximum induction time (isothermal mode).

Thermochemistry, Tautomerism, and Thermal Stability of 5,7-Dinitrobenzotriazoles

Nitro derivatives of benzotriazoles are safe energetic materials with remarkable thermal stability. In the present study, we report on the kinetics and mechanism of thermal decomposition for 5,7-dinitrobenzotriazole (DBT) and 4-amino-5,7-dinitrobenzotriazole (ADBT). The pressure differential scanning calorimetry was employed to study the decomposition kinetics of DBT experimentally because the measurements under atmospheric pressure are disturbed by competing evaporation. The thermolysis of DBT in the melt is described by a kinetic scheme with two global reactions. The first stage is a strong autocatalytic process that includes the first-order reaction (Ea1I = 173.9 ± 0.9 kJ mol-1, log(A1I/s-1) = 12.82 ± 0.09) and the catalytic reaction of the second order with Ea2I = 136.5 ± 0.8 kJ mol-1, log(A2I/s-1) = 11.04 ± 0.07. The experimental study was complemented by predictive quantum chemical calculations (DLPNO-CCSD(T)). The calculations reveal that the 1H tautomer is the most energetically preferable form for both DBT and ADBT. Theory suggests the same decomposition mechanisms for DBT and ADBT, with the most favorable channels being nitro-nitrite isomerization and C-NO2 bond cleavage. The former channel has lower activation barriers (267 and 276 kJ mol-1 for DBT and ADBT, respectively) and dominates at lower temperatures. At the same time, due to the higher preexponential factor, the radical bond cleavage, with reaction enthalpies of 298 and 320 kJ mol-1, dominates in the experimental temperature range for both DBT and ADBT. In line with the theoretical predictions of C-NO2 bond energies, ADBT is more thermally stable than DBT. We also determined a reliable and mutually consistent set of thermochemical values for DBT and ADBT by combining the theoretically calculated (W1-F12 multilevel procedure) gas-phase enthalpies of formation and experimentally measured sublimation enthalpies.

Effect of the natural antioxidant ferulic acid and its ester derivatives on the oxidative stability of ester-based lubricants: Experimental and molecular simulation investigations

Pentaerythritol oleate, as one of the ester-based lubricants, has excellent lubricity and low temperature properties, but is susceptible to oxidation due to the susceptible α-H of isolated double bonds in the molecular structure. Ferulate natural antioxidants, including the ferulic acid and its two ester derivatives were selected, focusing on exploring mechanisms, especially the effect of physical factors on the antioxidant properties. The chemical activity, dispersion, mobility and oxygen resistance of antioxidants were studied by molecular simulation. These combined results of the simulations show that the sequence of the antioxidation were isooctyl ferulate > ethyl ferulate > ferulic acid. Then the rotational oxygen bomb test and the pressure differential scanning calorimetry results confirmed the antioxidant activities of the three species. According to the Rancimat test, the oxidation induction time of the isooctyl ferulate/PETO was increased by 300% compared to the control.

Hydrothermal carbonization enthalpy using differential scanning calorimetry: Assessing the accuracy of the exhaust sample method

High pressure differential scanning calorimetry (DSC) is suitable to study the thermodynamics and kinetics of hydrothermal carbonization (HTC). To isolate the thermal effect of the process from the heat required to increase the DSC system temperature, a recently proposed method uses an additional run on the already reacted sample as the blank. The method assumes that the blank system is in equilibrium during the whole run; it neglects the potential for secondary reactions in the blank run, which may affect the results. This work assesses the effect of such an assumption on the final enthalpy results by performing additional re-runs on the same specimen and adopting longer isothermal segments to push the system composition closer to equilibrium. The study of HTC of cellulose at 250°C demonstrates that the thermal contribution of reactions in the second run is negligible compared to the primary HTC effects in the first run and within the experimental error. A deeper investigation of the thermal effect during re-runs shows that the biggest effect of reactions in such runs is to change the system composition rather than a direct exothermicity. Further, the exothermic activity disappears after 12 hours, suggesting that the sample has reached thermal equilibrium.

Experimental study on the in-situ combustion retorting of domanik oil shale

Oil shale is a critical strategic resource with enormous reserves. In-situ combustion technology offers great potential for the development of oil shale reserves. In this study, the combustion behavior and kinetics of Domanik oil shale were investigated using High Pressure Differential Scanning Calorimetry. Additionally, the thermal behavior of the oil shale during combustion was studied by using a self-designed Porous Medium Thermo-Effect Cell. Furthermore, the stability of the combustion front and the upgrading effect of the combustion process were investigated with Visual Combustion Tube, and the produced oil was analyzed to evaluate its quality. The results showed that the combustion process of oil shale is characterized by two reaction stages. The oil shale was found to form enough coke residue during the oxidation reactions to allow for stable propagation of a combustion front. The produced oil was of better quality compared to the naturally produced bitumen in oil shale, which indicates that the combustion process had a good upgrading effect. The findings of this study provide a better understanding of the in-situ upgrading process of kerogen and provide significant knowledge about the combustion mechanism of oil shale for its potential development using the in-situ combustion technology.

Quantitative Structure-Property Relationship (QSPR) of Plant Phenolic Compounds in Rapeseed Oil and Comparison of Antioxidant Measurement Methods

Natural antioxidants are known for their ability to scavenge free radicals and protect oils from oxidation. Our aim was to study the structural properties such as the number of hydroxyl groups and Bors criteria of phenolic substances leading to high antioxidant activity in oil in order to analyze common trends and differences in widespread in vitro antioxidant assays. Therefore, 20 different phenolic substances were incorporated into rapeseed oil and were measured using pressurized differential scanning calorimetry (P-DSC) and the Rancimat method. The Bors criteria had the highest influence on the antioxidant effect in rapeseed oil, which is why myricetin (MYR), fulfilling all Bors criteria, reached the highest result of the flavonoids. In the Rancimat test and P-DSC, MYR obtained an increase in oxidation induction time (OIT) of 231.1 ± 44.6% and 96.8 ± 1.8%, respectively. Due to differences in the measurement parameters, the results of the Rancimat test and P-DSC were only partially in agreement. Furthermore, we compared the results to in vitro assays (ABTS, DPPH, FC and ORAC) in order to evaluate their applicability as alternative rapid methods. These analysis showed the highest correlation of the oil methods with the results of the DPPH assay, which is, therefore, most suitable to predict the antioxidant behavior of oil.

Thermodynamic Characterization of Grease Oxidation–Thermal Stability via Pressure Differential Scanning Calorimetry

This study investigates and characterizes, via thermodynamic laws, a widely employed standard for measuring oxidation-thermal stability of lubricating greases—ASTM 5483—based on first-order chemical kinetics, using pressure differential scanning calorimetry (PDSC). Steps and active mechanisms in the controlled test are analyzed and modeled using energy and entropy transformations. Applying the degradation-entropy generation (DEG) theorem, oxidation induction time is related to accumulated oxidation entropy and entropy transfer by mass flow to obtain characteristic degradation coefficients. These DEG coefficients are calibrated using available measured data from the literature and subsequently used to predict induction times at various temperatures. DEG elements—trajectories, planes, and domain—presented here consistently characterized all greases studied. Results show that the high-pressure entropy transfer by oxygen mass flow in the final step of the ASTM 5483 procedure is the primary contributor to oxidation induction time, verifying the significance of this process in accelerating antioxidant depletion, which would otherwise take months to years under atmospheric conditions. DEG-predicted induction times at various temperatures are compared to induction times predicted by the first-order chemical kinetics model, revealing a close match. The new DEG model is also herein used to predict induction times at atmospheric pressure, whereas the first-order kinetics model is independent of pressure and limited to the specific conditions in ASTM 5483. The DEG approach has useful implications for the accelerated and unaccelerated evaluation of grease oxidation stability and grease useful life.

Enhancing hydrogen storage performance via optimizing Y and Ni element in magnesium alloy

Magnesium-based hydrogen storage materials are considered as one of the most promising candidates for solid state hydrogen storage due to their advantages of high hydrogen capacity, excellent reversibility and low cost. In this paper, Mg91.4Ni7Y1.6 and Mg92.8Ni2.4Y4.8 alloys were prepared by melting and ball milling. Their microstructures and phases were characterized by X-ray diffraction, scanning electron microscope and transmission electron microscope, and hydrogen absorbing and desorbing properties were tested by the high pressure gas adsorption apparatus and differential scanning calorimetry (DSC). In order to estimate the activation energy and growth mechanism of alloy hydride, the JMAK, Arrhenius and Kissinger methods were applied for calculation. The hydrogen absorption content of Mg92.8Ni2.4Y4.8 alloy reaches 3.84 wt.% within 5 min under 350 ℃, 3 MPa, and the maximum hydrogen capacity of the alloy is 4.89 wt.% in same condition. However, the hydrogen absorption of Mg91.4Ni7Y1.6 alloy reaches 5.78 wt.% within 5 min, and the maximum hydrogen absorption of the alloy is 6.44 wt.% at 350 ℃ and 3 MPa. The hydrogenation activation energy of Mg91.4Ni7Y1.6 alloy is 25.4 kJ/mol H2, and the enthalpy and entropy of hydrogen absorption are -60.6 kJ/mol H2 and 105.5 J/K/mol H2, separately. The alloy begins to dehydrogenate at 210 ℃, with the dehydrogenation activation energy of 87.7 kJ/mol H2. By altering the addition amount of Ni and Y elements, the 14H-LPSO phase with smaller size and ternary eutectic areas with high volume fraction are obtained, which provides more phase boundaries and catalysts with better dispersion, and there are a lot of fine particles in the alloy, these structures are beneficial to enhance the hydrogen storage performance of the alloys.

Application of Chromatographic and Thermal Methods to Study Fatty Acids Composition and Positional Distribution, Oxidation Kinetic Parameters and Melting Profile as Important Factors Characterizing Amaranth and Quinoa Oils

Amaranth and quinoa are classed as pseudocereals that do not belong to the grass family, meaning they are not technically a grain. Both of them are seeds with tremendous nutritional value; compared to other cereals, they contain much more fat. The aim of the study was to present the parameters characterizing thermal properties of amaranth and quinoa oils, such as: oxidation induction time, oxidation kinetic parameters, and melting profile. In isolated oils, the peroxide value, oxidative stability by the Rancimat test (in 120 °C) and the pressure differential scanning calorimetry (PDSC) method (at 100, 110, 120, 130, 140 °C), fatty acids composition, and their distribution between the triacylglycerol positions were determined. The kinetic parameters of the oxidation process (activation energy, pre-exponential factor, and reaction rate constants) were calculated using the Ozawa–Flynn–Wall method and the Arrhenius equation. To measure the melting profile, the differential scanning calorimetry (DSC) method was used. Both types of seeds are a good source of unsaturated fatty acids. Induction time of oxidation suggests that amaranth oil may have better resistance to oxidation than quinoa oil. The melting characteristics of the oils show the presence of low-melting triacylglycerol fractions, mainly containing unsaturated fatty acids, which means that a small amount of energy is required to melt the fats.

Thermal characteristics of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate in contact with nitrocellulose/nitroglycerine under continuous heat flow

Dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) and nitrocellulose/nitroglycerine (NC/NG) possess good energy properties, which were widely used in propellants, explosives and pyrotechnics. They are easy to contact with each other during their application and storage. However, their thermal characteristics under continuous heat flow have not been reported yet. Therefore, it is of great practical significance to study the thermal properties of TKX-50/NC/NG (mixture of TKX-50 and NC/NG). In this paper, the thermal characteristics and pressure behaviors of TKX-50/NC/NG, TKX-50 and NC/NG were characterized by high pressure differential scanning calorimetry (HPDSC) and adiabatic scanning calorimetry (ASC). The results showed that TKX-50 and NC/NG can promote each other to decompose under continuous heat flow, especially the thermal decomposition which affected by gases generation and heat feedback was more violent in the confined space. The decomposition peak temperature of TKX-50/NC/NG shifted to low temperature when the heat loss was ignored and the removal of decomposition gas was suppressed. The possible decomposition mechanism of TKX-50/NC/NG was speculated. It was considered that the intermediate products of TKX-50 and NC/NG decomposition under thermal stimulation would react with each other, which promoted TKX-50/NC/NG decomposition in one step at lower temperature. Thus, TKX-50 has high reactivity and high potential risk after contact with NC/NG under continuous heat flow. TKX-50 is not suitable for application with NC/NG. This study provides a reference for the structural design of nitrogen rich explosives and further broadens the researchers’ understanding of the application of TKX-50.

Lipid Fraction Properties of Homemade Raw Cat Foods and Selected Commercial Cat Foods

The purpose of the present study was to characterize lipid fraction extracted from five self-prepared and seven commercial cat foods using gas chromatography (GC) and pressurized differential scanning calorimetry (PDSC) techniques. Self-prepared food recipes were composed using BARFny kalkulator, software dedicated for balancing cat diets, and prepared on the basis of fresh raw meat and offal. Extracted fat fractions were compared qualitatively and quantitatively with literature data for the fat of whole prey items to check the main assumptions of the software used. The fatty acid (FA) composition and distribution were determined using GC. The PDSC method was used for the determination of the oxidative stability of extracted fats. The obtained results indicate that self-prepared cat foods contained a high level of essential fatty acids (EFA) but low oxidative stability, especially for those with significant amounts of polyunsaturated FA. The FA profile and oxidative stability were examined for four dry and three wet commercial cat foods. It was found that their omega-6 to omega-3 ratio was beneficial reaching 5.3:1 to 10.1:1, despite the low amount of EFA. The longer induction time was determined for fats extracted from commercial cat foods than for self-prepared ones, which indicate their higher oxidative stability.

Two sides of thermal stability of energetic liquid: Vaporization and decomposition of 3-methylfuroxan

Analysis of thermal behavior of liquids is often accompanied by vaporization. In an extreme case, the calorimetric (DSC) experiment reveals the only endothermic evaporation instead of the more valuable thermal decomposition. 3-Methylfuroxan (MMF) is an energetic monosubstituted 1,2,5-oxadiazole N-oxide that shows the above behavior. We investigate the sample mass and confinement effects and show that the pressure DSC allows observing thermal decomposition of target compound at 2.0 MPa. Advanced model-fitting kinetic analysis reveals two global stages, the first of which is a competition between the noncatalytic reaction and autocatalytic one, whereas the second global stage is a second-order reaction. Analysis of MMF thermolysis in solution in dibutyl phthalate shows the activation energy for noncatalytic reaction to be 145.4 ± 1.7 kJ mol−1. To resolve the gas decomposition products in experiments at 0.1 MPa pressure, where the evaporation is abundant, a gas chromatography–mass spectrometry coupled with thermal analyzer was used. Among the gases that are consistent with a furoxan ring rupture by CC and NO bonds (HNCO, CH3CN), we detect CH3COCN that retains CC bond. The formation of geminal cyanonitro compound in the course of thermolysis is proposed to explain the composition of the gas reaction products. Overall, with the range of thermal analysis tools (DSC, PDSC, GC–MS/TGA, thermokinetic modeling) we performed a detailed analysis of thermal transformations of unexplored simple monosubstituted furoxan. The applied methodological approaches could be transferred to other molecular liquids.

High pressure differential scanning calorimetry of poly(lactic acid) in presence of CO2 up to 100 MPa

For the processing of sustainable polymers with compressed CO2 to produce innovative products, knowledge of the thermodynamic properties of the polymer-CO2 system is essential. In this work, the thermal behaviour of three different poly(lactic acid) (PLA) grades, 2003D, 3251D and 8052D, from NatureWorks was determined experimentally using high pressure differential scanning calorimetry (HP-DSC) at CO2 pressures up to 100 MPa. After the HP-DSC had been extensively calibrated using potassium, sodium and indium, the thermal transition temperatures of the biopolymers were determined as a function of CO2 pressure. The melting and crystallization temperatures of the PLA grades were found to be up to 84 K lower in the presence of CO2. In addition, the crystallinity of the three biopolymers was investigated. It was shown that the degree of crystallinity was dependent on both the melting temperature and the CO2 pressure. In fact, a striking parabolic dependency which is also correlated with D-lactide content and molar mass was observed.

Synthesis and antioxidant properties of a novel arylamine antioxidant

AbstractA novel oil‐soluble arylamine antioxidant N1,N2‐diphenylethane‐1,2‐diamine (ND) was successfully synthesized, and the potential antioxidant behavior of which had never been reported before. The structure of ND was characterized via nuclear magnetic resonance (1H NMR, 13C NMR) and electron ionization mass spectrometry. The antioxidant performance of ND and its synergistic effect with 2,6‐di‐tert‐butyl‐4‐methylphenol (BHT) in di‐2‐ethylhexyl sebacate were evaluated by pressurized differential scanning calorimetry, thermogravimetry analysis, and hot oil oxidation test. All the results indicated that the synthesized antioxidant ND exhibited outstanding antioxidant performance and showed prominent synergistic effect with BHT in ester base oil. Furthermore, the probable synergistic anti‐oxidative effect between ND and BHT was discussed, which was mainly induced by the formation of a fresh BHT radical and the regeneration of ND antioxidant.