Properties of elastomers crosslinked by bisglycidyl ether of 2,2-bis(p-hydroxyphenyl)-1,1,1-trichloroethane

Chlorobisphenolic epoxy resins in crystalline form, e.g., bisglycidyl ether of 2,2-bis(p-hydroxyphenyl)-1,1,1-trichloroethane (BGECBP) and the system sulfur–N-cyclohexyl-2-benzothiazolesulfonamide were used as crosslinking agents for vulcanization of butadiene–styrene and butadiene–acrylonitrile rubber. The density of crosslinking was determined by the equilibrium swelling method and on the basis of the Mooney-Rivlin equation which gives the relation between stress and elongation. The dynamic properties, namely, G′ and G″ and mechanical loss factor δ, were determined. On the basis of these results, mechanisms for the crosslinking reaction were advanced, the activation energy was determined, and comparisons between crosslinking rates by different systems were made. It was found that vulcanizates crosslinked by BGECBP possess higher heat aging resistance and lower glass transition temperatures in comparison with those crosslinked by means of sulfur in the presence of N-cyclohexyl-2-benzothiazolesulfonamide.     

Comparison of nitrogen bases generated via HCl precipitation and ion exchange chromatography

Nitrogen base fractions were prepared from a heavy coal-derived liquid via two commonly accepted laboratory procedures and partially characterized. Significant differences in the composition of the two fractions suggest strongly that extreme caution should be exercised in interpreting and comparing the results of base characterization studies in which different base isolation procedures are used.     

Inhibition of radical polymerization in solvent‐based systems (security of solvent‐based radical polymerization of PSA‐acrylic in a plant reactor)

This article shows the influence of some chain‐transfer agents as inhibitors for acrylic solvent‐based polymerization. These chain‐transfer agents can offer significant advantages, as outlined below. The following chain‐transfer agents were studied to stop or slow down the polymerization process in the case of a runaway: n‐dodecyl mercaptan, trimethylolpropane‐trimercaptoacetate, phenothiazine, diphenylphenylen diamine, cuprum oxide, isopropanol, toluene, and carbon tetrachloride. Synthesized pressure‐sensitive adhesive based on acrylic polymers and containing 2‐ethylhexyl acrylate, methyl acrylate, and acrylic acid were used for the production of self‐adhesives with high cohesion. The polymerization was accomplished in ethyl acetate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1354–1357, 2003     

Photocrosslinking of solvent-based acrylic pressure-sensitive adhesives (PSA) by the use of selected photoinitiators type I

This study investigated the photocrosslinking of solvent-based acrylic pressure-sensitive adhesives (PSA) containing selected photoinitiators type I, known as α-cleavage photoinitiators. Photocrosslinking of PSA, especially of acrylic PSA, is well established crosslinking process using the UV radiation technology. UV-initiated crosslinking of acrylic PSA allows the synthesis of the wide range of UV-crosslinkable PSA with the interesting features. Especially, the important balances of properties such as adhesive and cohesive strength which are typically critical for the application performance can be achieved by this technology. The selection of suitable photoinitiator plays an important role to obtain the optimum properties of acrylic PSA including tack, peel adhesion, and shear strength. In this study, the investigations on different saturated conventional photoinitiators of type I for solvent-based PSA were carried out. The effects of photoinitiator concentration, UV crosslinking time and UV dose on the tack, peel strength, and shear strength were explored in detail for guiding the choice of photoinitiators to fabricate advanced PSA for industrial usage.     

The Effect of Long-Lasting Swimming on Rats Skeletal Muscles Energy Metabolism after Nine Days of Dexamethasone Treatment

This study investigates the effect of Dexamethasone (Dex) treatment on blood and skeletal muscle metabolites level and skeletal muscle activity of enzymes related to energy metabolism after long-duration swimming. To evaluate whether Dex treatment, swimming, and combining these factors act on analyzed data, rats were randomly divided into four groups: saline treatment non-exercise and exercise and Dex treatment non-exercised and exercised. Animals in both exercised groups underwent long-lasting swimming. The concentration of lipids metabolites, glucose, and lactate were measured in skeletal muscles and blood according to standard colorimetric and fluorimetric methods. Also, activities of enzymes related to aerobic and anaerobic metabolism were measured in skeletal muscles. The results indicated that Dex treatment induced body mass loss and increased lipid metabolites in the rats’ blood but did not alter these changes in skeletal muscles. Interestingly, prolonged swimming applied after 9 days of Dex treatment significantly intensified changes induced by Dex; however, there was no difference in skeletal muscle enzymatic activities. This study shows for the first time the cumulative effect of exercise and Dex on selected elements of lipid metabolism, which seems to be essential for the patient’s health due to the common use of glucocorticoids like Dex.     

The Combination of Intestinal Alkaline Phosphatase Treatment with Moderate Physical Activity Alleviates the Severity of Experimental Colitis in Obese Mice via Modulation of Gut Microbiota,Attenuation of Proinflammatory Cytokines,Oxidative Stress Biomarkers and DNA Oxidative Damage in Colonic Mucosa

Inflammatory bowel diseases (IBD) are commonly considered as Crohn’s disease and ulcerative colitis, but the possibility that the alterations in gut microbiota and oxidative stress may affect the course of experimental colitis in obese physically exercising mice treated with the intestinal alkaline phosphatase (IAP) has been little elucidated. Mice fed a high-fat-diet (HFD) or normal diet (ND) for 14 weeks were randomly assigned to exercise on spinning wheels (SW) for 7 weeks and treated with IAP followed by intrarectal administration of TNBS. The disease activity index (DAI), grip muscle strength test, oxidative stress biomarkers (MDA, SOD, GSH), DNA damage (8-OHdG), the plasma levels of cytokines IL-2, IL-6, IL-10, IL-12p70, IL-17a, TNF-α, MCP-1 and leptin were assessed, and the stool composition of the intestinal microbiota was determined by next generation sequencing (NGS). The TNBS-induced colitis was worsened in obese sedentary mice as manifested by severe colonic damage, an increase in DAI, oxidative stress biomarkers, DNA damage and decreased muscle strength. The longer running distance and weight loss was observed in mice given IAP or subjected to IAP + SW compared to sedentary ones. Less heterogeneous microbial composition was noticed in sedentary obese colitis mice and this effect disappeared in IAP + SW mice. Absence of Alistipes, lower proportion of Turicibacter, Proteobacteria and Faecalibacterium, an increase in Firmicutes and Clostridium, a decrease in oxidative stress biomarkers, 8-OHdG content and proinflammatory cytokines were observed in IAP + SW mice. IAP supplementation in combination with moderate physical activity attenuates the severity of murine colitis complicated by obesity through a mechanism involving the downregulation of the intestinal cytokine/chemokine network and oxidative stress, the modulation of the gut microbiota and an improvement of muscle strength.     

EPR Study of CO Adsorption onto CoZSM-5 Zeolite: Evidence for Spin Crossover upon Coordination and |z2, 2A1〉 Ground State

Adsorption of CO onto dehydrated cobalt-exchanged ZSM-5 zeolite was studied by CW-EPR techniques. It is shown that the reversible formation of a low spin carbonyl ¹{Co(CO) _n }⁷ adduct upon addition of carbon monoxide at p _CO>50–60 Torr involves significant change in the spin state of Co²⁺ from S=3/2 to 1/2. The spin Hamiltonian parameters of the adduct g _x =2.222, g _y =2.184, g _z =2.011, |A _x |=3.8 mT, |A _y |=3.2 mT, |A _z |=7.9 mT were determined by a computer simulation and further discussed in terms of the possible ground state and molecular structure. It is shown that the ¹{Co(CO) _n }⁷ cage complex exhibits a C_2v symmetry with |z ²,²A₁ ground state.     

Thermal stability of poly(2-ethylhexyl acrylates) used as plasticizers for medical application

This article discusses thermal analysis of different molecular weight poly(2-ethylhexyl acrylates) synthesized by radical polymerization of 2-ethylhexyl acrylate. The main aim of this work was to investigate the thermal properties and degradation process of synthesized acrylic homopolymers and forming of thermal degradation products during their pyrolysis. As investigated method pyrolysis combined with gas chromatography was used. Poly(2-ethylhexyl acrylates) are used as plasticizers for pressure-sensitive adhesives applied in medical area.     

A Process for Cf/SiC Composites Using Liquid Polymer Infiltration

A continuous carbon fiber/silicon carbide matrix composite material has been produced by a low-cost process. In this process the space in a two-dimensional carbon fiber preform is filled with a SiC powder by a pressure infiltration method. High particle packing densities are achieved within the fiber preform in this way. The compact body is heat-treated at 400°C to form a porous framework, which is then infiltrated with a liquid preceramic polymer, Ceraset^TM SN. Subsequently the infiltrated polymer is pyrolyzed in argon at 1300°C. The microstructure of the final composite is characterized, and mechanical properties of these composites are discussed.