Concentration Of Double Bonds Research Articles

Electron beam irradiation as a straightforward way to produce tailorable non-biofouling poly(2-methyl-2-oxazoline) hydrogel layers on different substrates

Uncontrolled accumulation of proteins and cells on implantable materials often leads to failure of their performance in vivo. The idea presented in this paper is the use of electron beam irradiation as a widely applicable, cost-effective, and defined method to produce non-biofouling hydrogel coatings to improve the biocompatibility and in vivo performance of implantable materials. Statistical copolymers poly[2-methyl-2-oxazoline-co-2-(3-butenyl)-2-oxazoline]s were deposited on different substrates and irradiated with beta radiation of different radiation doses (2–100 kGy). In the bulk state experiments, we found that the higher content of crosslinkable 3-butenyl units and a higher radiation dose resulted in more efficient crosslinking. Similarly, the irradiation of coatings demonstrated the high impact of the concentration of 3-butenyl units on crosslinking efficiency. Accordingly, the concentration of crosslinkable double bonds in the copolymer is crucial for the stability and homogeneity of the formed hydrogel layer. Stable and uniform hydrogel layers with thicknesses in the micrometer range were prepared from a 5 wt% copolymer solution. Depending on the preparation conditions, the hydrogel layers showed excellent non-biofouling properties with a low number of adherent cells. In addition, stiffness was dependent on the degree of crosslinking, and can thus be tailored for specific application in living tissue.

Highly sensitive photopolymer for holographic data storage.

The insufficient photosensitivity of conventional organic recording materials such as phenanthraquinone-doped poly(methyl methacrylate) (PQ/PMMA) significantly limits the recording speed in holographic data storage. Accelerating the formation of free radicals using the photosensitizer PQ during the photoreaction process and increasing the C = C double bond concentration of the matrix are effective methods for improving the photosensitivity. Using the above methods, we doped PQ/PMMA with the co-photoinitiator triethanolamine and co-monomer acrylamide to improve the photosensitivity of the material. Compared with the original PQ/PMMA material, the photosensitivity was increased by 10 times, and the diffraction efficiency was increased by 20%. The role of each doping component was studied by characterization and analysis. In addition, the introduction of the cross-linking agent N,N'-methylene-bisacrylamide, having high sensitivity, reduced the shrinkage of the material. We verified the application of the new material in a collinear system, and its high sensitivity showed its great potential for holographic data storage.

1H NMR-based analytical method: A valid and rapid tool for the epoxidation processes

The present work aims to propose a 1H NMR-based method for a rapid determination of conversion, yield, and selectivity in the epoxidation of organic substrates. Several experiments were carried out on different substrates and analyzed with both the proposed 1H NMR method and the volumetric traditional ones for a useful comparison. The results obtained with the traditional methods were deeply studied to find a mathematical correlation between the absolute analytical error and the double bond or oxirane ring concentration. The same was done for the conversion and yield derived from the analytical determinations. Finally, the results obtained with the proposed 1H NMR-based method on the epoxidation of methyl-oleate, as a model molecule, were compared with the results obtained by the traditional methods. A good agreement was obtained between the two classes of methods validating the proposed 1H NMR method.

Synthesis of Hydrogenated Natural Rubber Having Epoxide Groups Using Diimide.

Epoxidized natural rubber (ENR) with 50% mol of epoxide groups was synthesized using performic acid generated from the reaction of formic acid/hydrogen peroxide in latex form followed by hydrogenation using diimide generated from hydrazine (N2H4) and hydrogen peroxide (H2O2) with boric acid (H3BO3) as a catalyst. The resulting products (hydrogenated epoxidized natural rubber, HENR) were characterized by proton nuclear magnetic resonance spectroscopy (1H-NMR), gel testing, transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The effects of reaction parameters such as N2H4 amount, H2O2 amount, H3BO3 amount, gelatin amount, reaction time, and reaction temperature on the percentage of hydrogenation degree and gel content were investigated. The transmission electron micrographs of the particles confirmed a core/shell structure consisting of a highly unsaturated concentration region as the core encapsulated by a low carbon–carbon double bond concentration region as the shell, which indicated that the rubber particle seemed to be modified from the outer layer to the center of the rubber particle. Overall, the data showed that an increase in the amount of the individual chemicals, reaction time, and temperature increased the hydrogenation degree. However, a higher level of gelatin retarded an increase in the percentage of hydrogenation degree. As the hydrogenation degree increased, the gel content increased due to the ether linkage and the crosslinking reaction triggered through hydroxyl radicals. From DSC measurements, the glass transition temperatures of hydrogenated products increased above those of original rubbers. The thermal stability of hydrogenated products was improved, demonstrated by a decomposition temperature shift to a higher temperature than ENR, as shown by the results from the thermogravimetric analysis. Therefore, the hydrogenated ENR (HENR) exhibited good thermal stability, which could extend the applications of ENR in the automotive and oil industries.

Indicators of the Condition of Newborn Calves after Difficult Labor Syndrome

Difficult Labor Syndrome is recorded in 37.9 % of newborn calves. Newborn calves assessed on the Apgar scale of 2 points, are assigned to the cluster class born after easy labor, 1 point – after moderate labor and 0 points for difficult labor. The characteristic features of newborn calves after light birth are the manifestation of statistical functions and free movement. In newborn calves born with moderate and severe labor severity, weakly expressed motor-food reflexes are manifested. Visible mucous membranes are pale in color. Breathing is slow and shallow. Heart sounds are weak, the pulse is arrhythmic, slowed down with a decrease in the pulse wave. Decrease in glucose concentration, increase in total bilirubin level by 1.9 times with moderate severity of labor and 2.5 times with severe course of labor. An excess of creatinine contributes to the liborilization of the function of eosinophils, as a result, a symptom develops due to sensitization of the body. The activity of gamma-lutamyl transpeptidase in newborn calves after the Difficult Labor Syndrome in one hour increases 18.6 times, the activity of alkaline phosphatase during this period increases 1.5 times, aspartate aminotransferase and alanine aminotransferase - 1.6 times, lactate dehydrotransferase - 1.3 times. The most significant increase in the first 24 hours is the activity of γ-glutamyl transferase. At the age of one day, it exceeds the initial one by 95.6 times. The studies carried out indicate that the concentration of double bonds in the blood of newborn calves after the Difficult Labor Syndrome is marked by an increase of 20.46 % with an average severity of labor and 34.13 % with a severe course of labor when compared with a mild severity of labor. The level of diene conjugates in the blood of newborn calves with mild labor severity in comparison with moderate labor severity was statistically significantly increased (p <0.05), and 1.87 times with severe labor (p <0.01). The concentration of intermediate products of ketodienes and conjugated trienes in the blood of newborn calves with mild labor severity was statistically significantly increased by 1.75 times compared with moderate labor severity and 3.54 times with severe labor (p <0.01). Reduced glutathione is among the considered indicators of the least sensitivity (26.0 %) and specificity (43.0 %) in newborn calves after the Difficult Labor Syndrome.

Oxidative stress in suyagny sheep at the end of gestation, as a factor in pathogenesis development of eclampsia

Analysis of the results of medical examination of pregnant sheep 30...15...5 days before the expected term of lambing showed that in the urine of 12.11% of ewes, the concentration of ketone bodies in the blood plasma was 1.43 times higher than the physiological norm. In addition, there is a tendency to decrease the buffer bases to 18.41±1.53 mmol/l, as well as the glucose content below 2.12 ± 0.12 mmol/l. At the same time, the ratio of VN/ ACAS is up to 1.47 ± 0.12 mmol / L. It was found that the albumin fraction of proteins decreased by 1.51 times. Edema in the abdominal wall and underbelly, 9.5% lack of reaction to external stimuli, 15.0% decreased appetite, 10.0% jaundice of mucous membranes and 9.0% of sheep had a comatose state were found in 15.0% of animals. In a clinical study in sheep with eclampsia, hypertension over 136.1 mmHg and the presence of protein in urine over 3.2 g/l were recorded. These symptoms indicated classic signs of eclampsia, which occurred depending on the condition of sick animals in atypical and typical forms of manifestation. In animals with typical clinical signs of eclampsia, an increase in the level of diene conjugates was found to be 1.87 times, and the concentration of ketodiene intermediates and conjugated trienes was 1.75 times, the concentration of stable nitric oxide metabolites was 38.0%, and the vitamin E content decreased by 13.1%. At the same time, there was a 20.46% increase in the concentration of double bonds in the atypical form of eclampsia. In the blood plasma of patients with eclampsia of pregnant ewes, the activity of superoxide dismutase (1,736±0.37 units) is lower than in the comparison group (2,146±0.56 mmol/l). The obtained material of this work should be taken into account in the future when studying the problem of complicated pregnancy in the last stages of gestation in sheep and when developing therapeutic and preventive measures to ensure the long-term functioning of the reproductive potential and obtaining a viable newborn offspring.

Volume shrinkage and conversion rate of Al2O3 ceramic stereolithography suspension polymerised by ultraviolet light

The volume shrinkage and conversion rate are important factors determining the defect generation and accuracy control of green parts in ceramic stereolithography. In this study, a specific laser reflection method with coverslips and real-time Fourier-transform infrared (RT-FTIR) spectroscopy were used to determine the effects of the double-bond concentration, monomer ratio, photoinitiator, and incident light intensity on the real-time volume shrinkage and conversion rate. A slurry with a lower double-bond concentration obtained by using a solvent exhibited a smaller shrinkage. The shrinkage law for pure resin wasn't applicable owing to the ceramic particles. The mixing of ethoxylated pentaerythritol tetraacrylate (PPTTA) and 1,6-hexanediol diacrylate in suitable ratios promoted the conversion. In addition, the PPTTA could regulate the overall shrinkage. The photoinitiator had a small effect on the shrinkage. A high light intensity increased shrinkage significantly, while the conversion rate determined the shrinkage at a low light intensity.

МЕТАБОЛИЧЕСКИЕ ИЗМЕНЕНИЯ В ОРГАНИЗМЕ ОВЕЦ НА ПОСЛЕДНИХ СРОКАХ ГЕСТАЦИИ ПРИ ОСЛОЖНЕНИИ СУЯГНОСТИ ЭКЛАМПСИЕЙ

During the prophylactic examination at the last stages of gestation, 27.691.79% of pregnant ewes were diagnosed with eclampsia of varying severity: arterial hypertension (BP 136.1 ± 2.85 mm Hg), proteinuria (protein content in urine more than 3 0±0.49 g/l), edema and coma. In urine, an increase in the concentration of ketone bodies above the physiological norm by 2.3 times, their fractions of AcAc and BH - by 5.9 and 1.5 times, respectively, was noted. In the blood, a decrease in buffer bases to 18.41 ± 1.53 mmol/l, a glucose concentration to 2.12 ± 0.12 mmol/l, a BH/AcAc coefficient to 1.47 ± 0.12 mmol/l were established. There was an increase in the concentration of the intermediate product of lipid peroxidation in the blood by 43.0%, the concentration of stable nitric oxide metabolites - by 38.0%, vitamin C - by 24.1%. The content of vitamin E decreased by 13.1%, and the concentration of double bonds increased by 20.46% with an atypical form of eclampsia and by 34.13% with the appearance of a typical form of eclampsia. The level of diene conjugates increased by 1.87 times. The concentration of intermediate products of ketodienes and conjugated trienes is increased by 1.75 times in comparison with the atypical form of the course of eclampsia and by 3.54 times with its typical course. In pregnant ewes, the activity of oxidized glutathione is increased (2.879 ± 0.32 µmol/l), and superoxide dismutase (1.736±0.37 arb. units) is lower than in the comparison group (2.146±0.56 µmol/l). Consequently, the metabolic parameters that are traditionally used in the diagnostic algorithm in pregnant sheep with metabolic stress with symptoms of eclampsia in some cases are less sensitive and specific than the indicators of the system "lipid peroxidation - antioxidant protection". In the future, the material obtained in this work should be taken into account when studying the problem of eclampsia in pregnant sheep, as a concept for the development of impaired functioning of the lipid peroxidation-antioxidant protection system in this metabolic pathology.

EFFECT OF GAMMA IRRADIATION ON THE CROSSLINKING PROCESS OF NITRILE- BUTADIENE RUBBER WITH TRIAZINE AND MALEIC COMPOUNDS

The effect of γ-irradiation on the crosslinking process of nitrile butadiene rubber (NBR) with the participation of 4-dichloro 6-diethylamino-simmtriazine (DChDEAST) and 2,4- dimethylphenyl maleimide (DMPhM) was investigated. The molecular structure of the binary systems NBR + DChDEAST and NBR + DMPhM was determined by Fourier spectroscopy. Fourier transform infrared spectroscopy (FTIR) was used to determine the molecular structure of binary composite systems NBR + DChDEAST and NBR + DMPhM. The relative concentration of double bonds was predicted by determining its absorption by the optical density at the maximum absorption (967, 912 and 750 cm-1 ). It was found that at radiation doses above 250 kGy, the the number of crosslinks in irradiated blends were 1.05 × 104 and 0.66 × 104 mol /cm3 , respectively. The sensitizing effects of triasine and maleic compounds in radiation-chemical processes was investigated as well. Comprehensive studies of the structure and spatial network parameter of crosslinked NBR showed that the introduction of low molecular weight triazine and maleimide compounds increase the radiation-chemical yield (Gc) and this process also affect to increase the number of crosslinked molecules (1/Mnτ) and molecular weight of elastomers in turn.

Yellow Triazine as an Efficient Photoinitiator for Polymerization and 3D Printing under LEDs

AbstractThe search for new efficient photoinitiators for polymerization under the illumination of visible light is under extensive investigation due to their wide application in 3D printing. 2‐(4‐Methoxystyryl)‐4,6‐bis(trichloromethyl)‐1,3,5‐triazine (yellow triazine, R‐Cl) alone or the R‐Cl/additive systems have been indicated as promising photoinitiating systems in the free radical polymerization at 405 nm in our previous study. Here, further investigation of R‐Cl in the polymerization of a series of difunctional (meth)acrylate monomers is described. The effect of monomers on the polymerization performance is elucidated. The interplay of functional group, double bond concentration, and fluidity determines the polymerization rate and final conversions. Remarkably, R‐Cl shows better photoinitiating ability than well‐known commercial photoinitiator bisacylphosphine oxide in the polymerization of bis‐GMA/TEGDMA blend and EB605 under LED at 400 nm. The optimum concentrations of R‐Cl in the photopolymerization of TetEGDA and DPGDA monomers are revealed, the results of which are used to guide the 3D printing of DPGDA.

Quantitative detection of double bonds in hyaluronic acid derivative via permanganate ion reduction

The detection of double bonds in polymers exploited as scaffold materials, e.g. hyaluronic acid (HA) derivatives, is crucial for their further applications. The quantity variations of unsaturated units significantly affect the photoinduced crosslinking degree responsible for the mechanical properties of scaffolds. We demonstrate a simple, selective and rapid quantitative method that enables the detection of double bond moieties in polymers. The approach is based on a reaction with potassium permanganate which is spectrophotometrically confirmed. The effect of glycidyl methacrylate concentration and various reaction catalysts introduced at the stage of HA modification, as well as the change of double bond concentration over time, has been investigated using the proposed method. In addition, the developed quantitative method can be utilized for rapid and efficient detection of unreacted double bonds after photopolymerization as a tool for monitoring conversion over time.

Development and Investigation of Lanthanum Sulfadiazine with Calcium Stearate and Epoxidised Soyabean Oil as Complex Thermal Stabilizers for Stabilizing Poly(vinyl chloride).

Lanthanum sulfadiazine (LaSD) was synthesized from sulfadiazine and lanthanum nitrate using water as solvent under alkaline conditions, and was used as a novel rare earth thermal stabilizer to stabilize poly(vinyl chloride) (PVC). The structure of LaSD was characterized by elemental analysis (EA), Fourier transform infrared spectroscopy (FTIR) and thermo- gravimetric analysis (TGA). The influence of lanthanum sulfadiazine with calcium stearate (CaSt2) and epoxidized soybean oil (ESBO) on stabilizing PVC was studied by using the Congo red test, oven discoloration test, UV-vis spectroscopy and thermal decomposition kinetics. The results showed that the addition of LaSD as a thermal stabilizer can significantly improve the initial whiteness and long-term stability of PVC. In addition, the synergies between LaSD, ESBO, and CaSt2 can provide outstanding improvement in the long-term thermal stability of PVC. When the ratio of LaSD/ESBO/CaSt2 is 1.8/0.6/0.6, its thermal stability time is 2193 s which is the best state for stabilizing PVC. Furthermore, comparing the reaction energy (Ea) and the variations in the conjugate double bond concentration in PVC samples, the order of thermal stability of PVC was PVC/LaSD/ESBO/CaSt2 > PVC/LaSD/ESBO > PVC/LaSD. The thermal stability mechanism of LaSD on PVC was studied by the AgCl precipitation method and FTIR spectrum. The results showed that the action of LaSD on PVC was achieved through replacing unstable chlorine atoms and absorbing hydrogen chloride.

FTIR-ATR spectroscopy as a diagnostic tool in the diagnosis of hypercholesterolemia induced by cholesterol-rich diet in rats

Clinical Diagnosis is the process that identifies a possible disease or disorder that can be diagnosed through analysing specific components with multiple techniques and procedures that identifies the internal physiological changes. FTIR-ATR is a non-invasive, reagent-free diagnostic tool which can be rapidly and simultaneously analyze several components in the biological fluids and organs and which can be employed in analyzing the biomolecules. Hypercholesterolemia was induced in albino rats by feeding the animals with the regular diet supplemented with 1% cholesterol and 0.5 % cholic acid saturated with coconut oil for 6 weeks. End of induction study, experimental animals were sacrificed for biochemical and FTIR- ATR spectral analysis. Experimental serum samples were analyzed immediately for spectral recordings in the Mid IR region of 4000-450 cm-1. The intensity of the olefinic =CH bond (3012 cm−1) can be used as an index of relative concentration of double bonds in the lipid structure from unsaturated lipids. The C=O stretching at 1740 cm−1 monitor the glycerol backbone near the aqueous part of the lipids. Results on biochemical variations obtained with both these methods were compared. Based on results obtained the study suggest that the FTIR-ATR technique might be an additional technique to know more details at molecular levels in the diagnostic sector. Further, this technique could be standardised for routine utility in disease diagnosis and management in the medicinal field.

Biobased Acrylate Photocurable Resin Formulation for Stereolithography 3D Printing

To facilitate the ongoing transition toward a circular economy, the availability of renewable materials for additive manufacturing becomes increasingly important. Here, we report the successful fabrication of complex shaped prototypes from biobased acrylate photopolymer resins, employing a commercial stereolithography apparatus (SLA) 3D printer. Four distinct resins with a biobased content ranging from 34 to 67% have been developed. All formulations demonstrated adequate viscosity and were readily polymerizable by the UV-laser-based SLA process. Increasing the double-bond concentration within the resin results in stiff and thermally resilient 3D printed products. High-viscosity resins lead to high-resolution prototypes with a complex microarchitecture and excellent surface finishing, comparable to commercial nonrenewable resins. These advances can facilitate the wide application of biobased resins for construction of new sustainable products via stereolithographic 3D printing methods.

Evolution, Development and Function of Vertebrate Cone Oil Droplets.

To distinguish colors, the nervous system must compare the activity of distinct subtypes of photoreceptors that are maximally sensitive to different portions of the light spectrum. In vertebrates, a variety of adaptations have arisen to refine the spectral sensitivity of cone photoreceptors and improve color vision. In this review article, we focus on one such adaptation, the oil droplet, a unique optical organelle found within the inner segment of cone photoreceptors of a diverse array of vertebrate species, from fish to mammals. These droplets, which consist of neutral lipids and carotenoid pigments, are interposed in the path of light through the photoreceptor and modify the intensity and spectrum of light reaching the photosensitive outer segment. In the course of evolution, the optical function of oil droplets has been fine-tuned through changes in carotenoid content. Species active in dim light reduce or eliminate carotenoids to enhance sensitivity, whereas species active in bright light precisely modulate carotenoid double bond conjugation and concentration among cone subtypes to optimize color discrimination and color constancy. Cone oil droplets have sparked the curiosity of vision scientists for more than a century. Accordingly, we begin by briefly reviewing the history of research on oil droplets. We then discuss what is known about the developmental origins of oil droplets. Next, we describe recent advances in understanding the function of oil droplets based on biochemical and optical analyses. Finally, we survey the occurrence and properties of oil droplets across the diversity of vertebrate species and discuss what these patterns indicate about the evolutionary history and function of this intriguing organelle.

Volume shrinkage and abrasive wear properties of crosslinked Poly(ester-urethane-acrylate)/MMA copolymer: Effect of chain length

ABSTRACTThe current study deals with the preparation of novel crosslink transparent poly(ester-urethane-acrylate)/methyl methacrylate (TPEUMA) copolymers and the effect of hydroxyl terminated aromatic polyester (PEs) was also investigated. The properties of TPEUMA were investigated in terms of double bond concentration, polymerization shrinkage, abrasive wear analysis and chemical resistance. The volume shrinkage decreased due to the significant reduction in the concentration of double bonds. The first two effects reflect in lowering the abrasive wear resistance properties at room temperature, while the larger chain length between crosslink decreases the hardness. Decrease in polymerization shrinkage shows more condensed microstructure which was revealed by the abrasive wear rate of TPEUMAs due to hydrogen bonding near to crosslink point. Increase in the chain length of PEs, decreases the glass transition temperature of TPEUMA copolymer which results in loose microstructure. Worn surface were studied using scanning electron microscope to give insight on the wear mechanism of TPEUMA crosslink. It can be suggested from the present study that this copolymer can be used for a broad range of optical applications.

The role of molecular structure on impact resistance and bending strength of photocured urethane-dimethacrylate polymer networks

The objective of this study was to investigate the influence of molecular structure on impact resistance (an) and bending strength (σ) of photocured urethane-dimethacrylate polymer networks. Urethane-dimethacrylate (UDMA) monomers were synthesized through reaction of oligoethylene glycol monomethacrylate (OEGMMA) with diisocyanate (DI). OEGMMA varied within the length of the oligooxyethylene chain, which consisted of one to four oxyethylene units. DI varied in chemical character: aliphatic, cycloaliphatic or aromatic. The molecular structure of UDMA polymers was characterized by X-ray powder diffraction, which allowed the calculation of the d-spacing (d) and dimensions of microgel agglomerates (D). The measurements of the polymerization shrinkage were used for the determination of the degree of conversion (DC), whereas the concentration of double bonds was used as a measure of the crosslink density (q). It was found that all structural parameters depend on the UDMA chemical structure. The increasing length of the oligooxyethylene chains caused the decrease in d and q, in contrast to the increase in D and DC. The DI chemical character caused the increase in the DC and q accordingly: symmetrical cycloaliphatic or aromatic < asymmetrical cycloaliphatic and aromatic < substituted aliphatic < linear aliphatic. The compact packing and high DC in polymers derived from aliphatic DIs gave rise to the decrease in d and the increase in D. The non-planar conformation of cycloaliphatic DIs emerged in high d as well as D. The planar conformation of aromatic DIs resulted in the decrease in d as well as D. The study indicated that mechanical behavior of UDMA polymer networks can be explained in terms of the structural parameters. DC and q appeared to be the main factors determining both mechanical properties of poly(UDMA)s. The an was also shown to be affected by d. Particularly high linear correlations were found on a semi-logarithmic scale for the DC and d with an. an increased as the DC increased, whereas d decreased.

Kinetics of the epoxidation of soybean oil with H2O2 catalyzed by phosphotungstic heteropoly acid in the presence of polyethylene glycol

In this work, the kinetics of “in situ” epoxidation of soybean oil with H2O2 (30% w/w), catalyzed by phosphotungstic heteropoly acid [π‐C5H5N(CH2)15CH3]3[PW4O16] (PHA) phase transfer catalyst and polyethylene glycol (PEG) as interfacial agent in dichloroethane, were investigated at 40, 50, 60, and 70°C. Assuming that the epoxidation reaction occurred in the pseudo‐homogeneous catalytic system and the side reaction of epoxy ring cleavage was negligible, the results appeared that the epoxidation reaction of soybean oil in the presence of PEG was a second‐order with respect to double bond concentration and a first‐order to the H2O2 concentration. The corresponding apparent activation energy (42.12 kJ/mol) was lower than that of PHA alone (49.23 kJ/mol), indicating that PEG could decrease the activation energy and speed up the epoxidation reaction of soybean oil.Practical applications: An environmentally friendly catalyst is eagerly needed to produce peroxided soybean oil for low yield and to prevent polluting the environment through the epoxidation of soybean oil with peracid. Phosphotungstic heteropoly acid phase transfer catalyst and polyethylene glycol improve the conversion and selectivity of the epoxidation reaction of soybean oil, and enhance its production efficiency.The activation energy of the soybean oil epoxidation reaction with H2O2 catalyzed by phosphotungstic heteropoly acid (PHA) in the presence of polyethylene glycol (PEG) was lower than that of PEG alone, accounting for the results showing that the epoxy group band of the former (PHA + PEG) appeared quicker than the latter (PHA) in IR spectra.

Development of a predictive model for choosing cure agents for elastomer blends

ABSTRACTIn elastomer blends with either polarity differences or unbalanced double bond concentration, cure agents have a preferential partition to one of the phases, with a tendency of having overcure in one phase and undercure in the other. To achieve proper vulcanization and improved performance in the final product, it is essential to have a correct balance between solubility and miscibility of each of the various cure agents in the elastomer blend composite. Cure agents with varying polarities and various reactivities have different crosslinking densities in the rubber compound. A homogeneous crosslinking density leads to superior mechanical properties. The method presented in this work includes a new tool based on a genetic optimization algorithm for assessing the partitioning of cure agents in different elastomers and their blends. The quantitative data allowed for a series of analyses of the solubility of the cure agents in the elastomer mixtures of different phases and was validated by correlation with their physico–chemical and mechanical properties of the resulting blend. This is an important tool for planning a cure system in rubber blends and to avoid incorrect partitioning of cure agents and consequent uneven curing of the final compound. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41929.

Reducing of on Polymerization Shrinkage by Application of UV Curable Dental Restorative Composites

Abstract This manuscript describes dental compositions contain in-organic fillers, multifunctional methacrylates and photoinitiators. The main problem by application and UV curing process is the shrinkage of photoreactive dental materials during and after UV curing process. Total shrinkage of UV curable dental composites is a phenomenon of polymerization shrinkage, typical behavior for multifunctional methacrylates during polymerization process. The important factors by curing of dental composites are: kind and concentration of used methacrylates, their functionality, double bond concentration, kind and concentration of added photoinitiator and UV dose. They are investigated UV-curable dental compositions based on 2,2-bis-[4-(2-hydroxy-3-methacryxloyloxypropyl)phenyl]propane (Bis-GMA) and containing such multifunctional monomers as 1,3-butanediol dimethacrylate (1,3-BDDMA), diethylene glycol dimethacrylate (DEGDMA), tetraethylene glycol dimethacrylate (T3EGDMA), trimethylolpropane trimethacrylate (TMPTMA), polyethylene glycol 200 dimethacrylate (PEG200DA). Reduction of polymerization shrinkage of dental compositions is at the moment a major problem by dental technology.