Thermal Decomposition of Cross-linked Polybutadiene and its Copolymers

Polybutadiene and two copolymers containing butadiene and styrene have been cross-linked by thermal processes, by the use of initiators in solution, and by intimately mixing an initiator with the polymer and then heating this blend. The most efficient cross-linking process is the use of an intimate blend of the initiator and polymer. Most cross-linking processes lower the onset temperature of degradation, presumably because chain scission reactions occur simultaneously with cross-linking, while also increasing the fraction of non-volatile residue which is produced. It is believed that the density of cross-links is responsible for the increased yield of non-volatile residue

Thermal Decomposition and Combustion of γ-irradiated Polyamide 6 Containing Phosphorus Oxynitride or Phospham

Polyamide 6 (PA-6) containing the fire retardants phosphorus oxynitride ((PON)m) or phospham ((PN2H)n) was exposed to 60Co-γ-rays (absorbed dose: 1.0–4.0 MGy). The irradiation led to crosslinking of the polymer which caused an increase in the char yield and a decrease in the flammability of the polymer. The combustion behavior was strongly affected by irradiation: dripping was totally prevented in the case of system PA-6/(PN2H)n and strongly retarded in the case of system PA-6/(PON)m. The thermal stability of the system PA-6/(PN2H)n decreased with increasing absorbed dose whereas the thermal stability of the system PA-6/(PON)m did not change

Thermal degradation of Cross-Linked Polyisoprene and Polychloroprene

Polyisoprene and polychloroprene have been cross-linked either in solution or in solid state using free radical initiators. In the comparable experimental conditions higher cross-linking density was observed in the solid state process. Independent of the cross-linking method, polychloroprene tended to give a higher gel content and cross-link density than does polyisoprene. Infrared characterization of the cross-linked materials showed cis-trans isomerization occurred in the polyisoprene initiated by benzoyl peroxide, whereas no isomerization was found in the samples initiated by dicumyl peroxide. Polyisoprene does not cross-link by heating in a thermal analyzer, whereas polychloroprene easily undergoes cross-linking in such conditions. Infrared spectroscopy showed that in the case of polyisoprene, rearrangements occur upon heating which lead to the formation of terminal double bonds, while polychloroprene loses hydrogen chlorine which leads to a conjugated structure. There is apparently some enhancement of the thermal and thermal oxidative stability of polyisoprene because of the cross-linking. Cross-linked polychloroprene is less thermally stable than the virgin polymer. Cross-linking promotes polymers charring in the main step of weight loss in air, which leads to enhanced transitory char

The effect of gas phase flame retardants on fire effluent toxicity

Standard industry formulations of flame retarded aliphatic polyamides, meeting UL 94 V-0, have been burned under controlled conditions, and the yields of the major asphyxiants, carbon monoxide (CO) and hydrogen cyanide (HCN) have been quantified. Although both the combination of aluminium phosphinate and melamine polyphosphate, and the combination of brominated polystyrene and antimony oxide, inhibit combustion reactions in the gas phase, this study shows that the phosphorus causes a much smaller increase in the CO and HCN yields than antimony-bromine. The mechanisms of CO and HCN generation and destruction are related to the flame inhibition reactions. Both CO and HCN form early in the flame, and the OH radical is critical for their destruction. Crucial, in the context of the flame inhibition mechanism, is the observation that the phosphorus system reduces the H and O radical concentrations without a corresponding decrease in the OH radical concentration; conversely, the bromine system reduces all three of the key radical concentrations, H, O and OH, and thus increases the fire toxicity, by inhibiting decomposition of CO and HCN. Moreover, while the phosphorus flame retardant is effective as an ignition suppressant at lower temperatures (corresponding to early flaming), this is effect “switches off” at high temperatures, minimising the potential increase in fire toxicity, once the fire develops. Since flame retardants are most effective as ignition suppressants, and at the early stages of flaming combustion, while most fire deaths and injuries result from toxic gas inhalation from more developed fires, it is clearly advantageous to have an effective gas phase flame retardant which only causes a small increase in the toxic product yield

SYSTEMIC INFLAMMATORY RESPONSE SYNDROME (SIRS) IN SURGICAL TREATMENT OF NONSPECIFIC PURULENT DISEASES OF SPINE

Main clinical syndromes of non-specific purulent diseases of spine are neurological, including pain (vertebrogenous) syndrome and syndrome of systemic inflammatory response. All patients were divided into two groups: 1st - control group (50 patients with non-specific purulent diseases of spine without syndrome of systemic inflammatory response), 2nd - main group (70 patients with non-specific purulent diseases with syndrome of systemic inflammatory response). Main indications for the operation were surgical decompression of neurovascular formations of spine canal and. sanation of suppurative focus in vertebras. Complex approach to the treatment of septic patients by optimization of surgical tactics and. choice of susceptible antibacterial therapy allows to achieve positive outcomes of surgical treatment in most cases

РЕЗУЛЬТАТЫ ИЗУЧЕНИЯ ИЗОТИПОВ ОБЩИХИММУНОГЛОБУЛИНОВ У БОЛЬНЫХ СИФИЛИСОМ

The investigation of the level of common immunoglobulins in 59 patients with Lues and 23 patients with seroresistent Lues revealed some peculiarities that depend on both the clinical form and duration of the infection process as well as the presence of an associated specific affection of the central nervous system. Clinical sings typical for secondary Lues of the skin and mucus membranes are accompanied by intensified synthesis of the proinflammatory isotypes lgМ and IgG3 in the blood. Early hidden Lues is associated with formation of the antiinflammatory IgA isotype. An increased antibody formation is typical for early types of Lues whereas immunoglobulin levels in late types of the disease are normal. In case of a luetic affection of the central nervous system a decreased production of IgM is revealed.Анализ содержания изотипов общих иммуноглобулинов у 59 больных сифилисом и 23 пациентов с наличием серорезистентности выявил особенности, зависящие от клинической формы заболевания и длительности инфекционного процесса, а также ассоциации с развитием специфического поражения ЦНС. Клинические проявления, характерные для вторичного сифилиса кожи и слизистых оболочек, сопровождаются повышенным синтезом в сыворотке крови провоспалительных изотипов lgМ и IgG3, ранний скрытый сифилис - образованием противовоспалительного изотипа IgA. Усиленное антителообразование присуще ранним формам сифилиса, при поздних формах заболевания уровень иммуноглобулинов не отличается от нормальных величин. При сифилитическом поражении нервной системы выявляется сниженная продукция IgM

Solution and gel "prontosan" in local treatment of different purulent wounds

In open prospective concurrent controlled study on 21 patients (experimental Qroup) explored characteristics of solution and gel ’Prontosan’ in local treatment of different purulent wounds and ulcers, in comparison with 3% H202 solution and water-soluble antibacterial ointments on 30 patients (control group). Detected beneficial effects of solution and gel ‘Prontosan’ in local treatment of different pu-rulent wounds and ulcers owing to acceleration of cleansing and shortening wound healing, decreasing of pain syndrome. Did not registered any side effects of local using of solution and gel 'Prontosan' on patients with different purulent wounds and ulcers.В открытом проспективном контролируемом исследовании у 21 пациента с гнойными ранами и язвами различного происхождения для очищения ран в перевязочной и местного лечения под повязкой применены раствор и гель «Пронтосан» в сравнении с 3% раствором перекиси водорода и антибактериальными мазями на гидрофильной основе (30 больных). Выявлено, что раствор и гель «Пронтосан» эффективны при местном лечении гнойных ран и язв различного происхождения за счет ускорения их очищения, сокращения сроков заживления, снижения интенсивности местного болевого синдрома. Местное применение раствора и геля «Пронтосан» хорошо переносится и не вызывает побочных эффектов у пациентов с гнойными ранами и язвами различной этиологии

Features of healing of purulent wounds in patients with chronic liver diseases

The purpose of the study is to show the effect of chronic liver damage of various origins on the healing of purulent wounds.Цель исследования – показать влияние хронического поражения печени различного происхождения на заживление гнойных ран

The Effect of Zn-Al-Hydrotalcites Composited with Calcium Stearate and β-Diketone on the Thermal Stability of PVC

A clean-route synthesis of Zn-Al-hydrotalcites (Zn-Al-LDHs) using zinc oxide and sodium aluminate solution has been developed. The as-obtained materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The effects of metal ions at different molar ratios on the performance of hydrotalcites were discussed. The results showed that the Zn-Al-hydrotalcites can be successfully synthesized at three different Zn/Al ratios of 3:1, 2:1 and 1:1. Thermal aging tests of polyvinyl chloride (PVC) mixed with Zn-Al-LDHs, calcium stearate (CaSt2) and β-diketone were carried out in a thermal aging test box by observing the color change. The results showed that Zn-Al-LDHs can not only enhance the stability of PVC significantly due to the improved capacity of HCl-adsorption but also increase the initial stability and ensure good-initial coloring due to the presence of the Zn element. The effects of various amounts of Zn-Al-LDHs, CaSt2 and β-diketone on the thermal stability of PVC were discussed. The optimum composition was determined to be 0.1 g Zn-Al-LDHs, 0.15 g CaSt2 and 0.25 g β-diketone in 5 g PVC

Synthesis and Flammability Testing of Epoxy Functionalized Phosphorous-Based Flame Retardants

Several potential new phosphorus-containing flame retardant molecules were evaluated for heat release reduction potential by incorporation of the molecules into a polyurethane, generated from methylene diphenyl diisocyanate and 1,3-propane diol. The heat release reduction potential of these substances was evaluated using the pyrolysis combustion flow calorimeter (PCFC). The polyurethanes were prepared in the presence of the potential flame retardants via solvent mixing and copolymerization methods to qualitatively evaluate their potential reactivity into the polyurethane prior to heat release testing. The functionality of the flame retardants was epoxide based that would potentially react with the diol during polyurethane synthesis. Flammability testing via PCFC showed that the heat release reduction potential of each of the flame retardants was structure dependent, with phosphates tending to show more effectiveness than phosphonates in this study, and alkyl functionalized phosphorus groups (phosphate or phosphonate) being more effective at heat release reduction than cyclic functionalized groups