Degradation Of PC Research Articles

Development of hybrid composites reinforced with biocarbon/carbon fiber system. The comparative study for PC, ABS and PC/ABS based materials

A PC/ABS blend was used to prepare hybrid composites reinforced with the use of a biocarbon/carbon fiber (BC/CF) system. The purpose of using blends of this type was to reduce the degradation of PC during the blending processes, which turned out to be effective already at 40% ABS in the blend structure. TGA analysis and rheological measurements confirmed that the addition of ABS in the matrix structure allowed reduction of PC hydrolytic degradation. The decrease in DTG peak value for the PC/20BC composite is even 50 °C, whereas for the ABS/20BC sample the peak values were the same as reference pure ABS. Izod tests showed that the impact resistance for ABS/BC composites was more than twice as high as PC/BC materials, 37 J/m to 13 J/m respectively. For PC/ABS composites, the addition of ABS in the structure also served to improve impact resistance. The main purpose of the hybridized reinforcement application was the reduction of thermal expansion in the material and homogenization of the fibrous CF structures. For reference PC/20CF samples the difference in CLTE values is over 1000%, while for PC/20(BC-CF) hybrid composites it is reduced below 300%. Detailed analysis of the expansion characteristics, carried out by TMA methodology, showed significant improvement in the isotropy of hybrid materials, which was also confirmed by structural observations. The improvement of process stability as well as excellent thermomechanical parameters indicates that biocarbon can be an excellent additive for standard fibrous reinforcement, limiting the phenomenon of structure anisotropy.

Degradación in situ del pastizal Chilliwar Festuca dolichophylla una alternativa para alimentación animal

The objective was to evaluate the kinetics of degradation in the first compartment (C1) of llamas of the dry matter(DM) of forage F. dolichophylla harvested at 3, 6, 9, 12 and 15 weeks of growth during two seasons (rainy and dry ).The degradation kinetics of crude protein (PC), neutral detergent fiber (NDF) and acid detergent fiber (ADF) wereevaluated only in the rainy season. In situ degradation was described by the equation of Orskov et al., (1980) D = a +b (1-exp-ct). A completely randomized block design with a 2 x 5 factorial arrangement was used for the MS. The rate (c) 3.24% h-1, intercept of the curve (a) 22.22%, and the degradation potential of MS (a + b) 91.32%, were notaffected (P> 0.05) by the time, age and interaction. However, the effective DM degradation (estimated with a flowrate of k = 2% h-1) was affected (P 0.05) by the age of growth. However, the potentialand effective degradation (k = 2% h-1) was influenced by the age of growth, ranging from 97.7 to 90.1%, 86.0 to80.8%, and from 72.4 to 71.9% from 3 to 15 weeks of increase. The effective degradation of PC, NDF and ADF wasaffected (P <0.05) by the age of growth, decreasing from 88.6 to 63%, 63.5 to 57.1%, and from 51.7 to 40.3% from3 to 15 weeks of growth. It is concluded that the accelerated degradation of the protein at early hours, and lowdegradation of cell walls causes an imbalance in the availability of protein and absence of energy.

Polycomb Protects H3K27me3 from Active Demethylation by Utx

Maintenance of cellular identity is a critical developmental process depending on the proper transmission of epigenetic information over cell generations. H3K27me3, controlled by the Polycomb group (PcG) proteins, represents such an epigenetic mark and is correlated to long-term and heritable gene silencing. However, H3K27me3 is also found at many inducible or cell cycle regulated genes, implicating an involvement in more dynamic processes. The chromodomain of Polycomb (Pc) binds the methyl moiety of H3K27 and anchors the PRC1 complex involved in nucleosome compaction. We adapted an Auxin-based degron system to deplete Pc during Drosophila development. The fast degradation of Pc results in the rapid removal of the H3K27me3 mark by the de-methylase Utx and in consequence in the rapid upregulation of Hox genes. This result shows that the chromodomain actively protects the methyl mark, inhibiting removal by Utx, hence, allowing for a much more dynamic regulation of PcG target genes.

Physical mechanisms responsible for the water‐induced degradation of PC61BM P3HT photovoltaic thin films

ABSTRACTWe show that [6,6]‐phenyl‐C61‐butyric acid methyl ester (PC61BM) at the surface of thin film blends of poly(3‐hexylthiophene) (P3HT):PC61BM can be patterned by water. Using a series of heating and cooling steps, water droplets condense onto the blend film surface. This is possible due to the liquid‐like, water swollen layer of poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate. Breath pattern water deformation and subsequent drying on the film surface results in isolated PC61BM structures, showing that migration of PC61BM takes place. This was confirmed by selective wavelength illumination to spatially map the photoluminescence from the P3HT and PC61BM. Within a device, redistribution of the surface PC61BM into aggregates would be catastrophic, as it would markedly alter device performance. We also postulate that repeated volume change of the poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate layer by water swelling may be, in part, responsible for the delamination failure mechanism in thin film solar cells devices. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 141–146

Preparation and Characterization of a Tertiary Nanocomposite from Polycarbonate and Epoxy Resin

An epoxy prepolymer based on diglycidyl ether of bisphenol-A was modified with poly(bisphenol A carbonate) (PC) by a reactive blending process at high temperature in the presence of alumina nanoparticles. Cure kinetics of the copolymer network was investigated by dynamic and isothermal differential scanning calorimetry (DSC). Two kinetic models of n-th order and Sestak-Berggren (SB) equations were used to estimate the kinetic parameters. Curing characteristics of the nanocomposite blend was further interpreted using the advanced isoconversional method of Vyazovkin. FT-IR results show that presence of nanoalumina may promote the degradation of PC and reactions between epoxy and PC that occur in 200°C. Results from SEM analysis revealed that the nanoparticle may enhance the adhesion property of the blend by reducing the number and size of cracks on the fracture surface. It was shown by XRD measurements that an ultrasonicated dispersion process is an effective approach to homogeneous dispersion of nanoalumina into PC-DGEBA blend.

Effect of a Novel Phosphorus and Silicon System on Flame Retardancy and Thermal Degradation of PC

The novel phosphine was used with a silicon resin to impart flame resistancy to polycarbonate. Combustion behaviors and thermal degradation properties of flame retardancy PC have been assayed by limiting oxygen index, vertical burning test and thermogravimetric analysis. Dynamic rheological of FR-PC was also examined. Flame retardant consisted of 80 wt.% PPPO and 20 wt.% silicon resin possesses excellent flame retardancy for PC. LOI value of FR-PC is 33.0% and passes UL-94 V-0 rating. SEM revealed that the char yield as well as char properties have direct effects on the flame retardancy.

Non-isothermal degradation kinetics for polycarbonate/ polymethylphenylsilsesquioxane composites

AbstractThe thermal degradation behaviors of PC/PMPSQ (polymethylphenylsilsesquioxane) systems were investigated by thermogravimetric analysis (TGA) under non-isothermal conditions in nitrogen atmosphere. During non-isothermal degradation, Kissinger and Flynn-Wall-Ozawa methods were used to analyze the thermal degradation process. The results showed that a remarkable decrease in activation energy ( E ) was observed in the early and middle stages of thermal degradation in the presence of PMPSQ, which indicated that the addition of PMPSQ promoted the thermal degradation of PC. Flynn-Wall-Ozawa method further revealed that PMPSQ significantly increased the activation energy of PC thermal degradation in the final stage, which illustrated that the PMPSQ stabilized the char residues and improved the flame retardancy of PC in the final period of thermal degradation process

Thermal degradation behaviours of flame-retardant polycarbonate containing potassium diphenyl sulfonate and polymethylphenylsilsesquioxane

AbstractPotassium diphenyl sulfonate (KSS) and polymethylphenyl silsesquioxane (PMPSQ) were proved to be effective flame retardants for PC by the LOI test and UL-94 measurements. The thermal degradation behaviours were investigated by TGA and flame-retardant mechanism of KSS/PMPSQ/PC system was studied by the kinetic analysis methods including Kissinger method and Flynn- Wall-Ozawa method. The results showed that the activation energies of flameretardant PC (FRPC) were lower than that of pure PC at lower degree of conversion, which indicated that the KSS and PMPSQ both promoted the thermal degradation of PC in the early and middle stages. Flynn-Wall-Ozawa method further revealed that the addition of the flame retardant PMPSQ increased the activation energy of FRPC thermal degradation in the final stage, which illustrated that the PMPSQ stabilized the char residues and improved the flame retardancy of FRPC in the thermal degradation. Therefore, the improved flame-retardant behaviours of KSS and PMPSQ on PC were achieved.

Studies on the thermal stability and degradation kinetics of Pd/PC nanocomposites

AbstractEffect of heating rate, Pd content, and synthesis method on the thermal stability of the ex situ and in situ Palladium/polycarbonate (Pd/PC) nanocomposites was investigated. TEM images revealed discrete Pd nanoclusters of about 5 and 15 nm sizes for 1 and 2 vol % ex situ nanocomposites, respectively. However, agglomerated Pd nanoclusters were noticed in the in situ samples, irrespective of the Pd content. The ex situ Pd/PC nanocomposites showed high onset temperature (Ti) for thermal degradation of PC than the in situ and pure PC samples. Pd content and heating rates were found to have a positive influence on the Ti and Tm (temperature at the maximum degradation rate occurs) of the Pd/PC nanocomposites. Thermal degradation of the PC was found to follow the first‐order kinetics in the Pd/PC nanocomposites. The activation energies associated with the degradation were determined by using the Kissinger method. These activation energies are used to construct the Master decomposition curve (MDC) and weight–time–temperature (α–t–T) plots that describe the time‐temperature dependence of the PC pyrolysis in the Pd/PC nanocomposites. These constructed α–t–T plots were validated with the data from isothermal measurements. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Comprehensive two-dimensional liquid chromatography and hyphenated liquid chromatography to study the degradation of poly(bisphenol A)carbonate

Size exclusion chromatography (SEC), gradient polymer elution chromatography (GPEC) and liquid chromatography at critical conditions (LC-CC) have been developed and applied to observe chemical changes in poly(bisphenol A)carbonate (PC) due to hydrolytic degradation. Especially LC-CC appeared to be very successful to observe differences in functionality of PC as result of hydrolytic degradation. Observed differences due to degradation could be identified by (semi) on-line coupling to matrix assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The differences in functionality could be attributed to the formation of different end-groups, i.e. OH end-groups. In addition, comprehensive two-dimensional liquid chromatography (2D-LC) has been applied successfully to study the hydrolytic degradation of PC. LC-CC × SEC showed that the formation of PC with different end-groups occurred over the whole molecular mass range. This information could not be obtained with the separate liquid chromatographic techniques, thereby illustrating the added value of 2D-LC.

Dynamics of lipase catalyzed enzymatic degradation of poly(bisphenol‐A carbonate)

AbstractPoly(bisphenol‐A carbonate) (PC) was degraded in solution at various temperatures (26–70°C) by different lipases, Candida Rugosa (CR), Hog Pancreas (HP), Lipolase (LL), and Novozyme (NV), in various solvents. The degradation of PC was monitored using gel permeation chromatography (GPC). The molecular weights of oligomers obtained were around ∼1,400 irrespective of the lipases used. Continuous distribution kinetics was proposed to determine the rate coefficients of the polymers and deactivation of the enzyme. The FTIR analysis of the polymer before and after degradation showed that there is large reduction of carbonate linkages and generation of hydroxyl and acidic groups in the broken chains. The optimal temperatures for HP and other lipases were 50 and 60°C, respectively. HP showed higher degradation activity at lower temperatures and the overall degradability of the lipases was in the order of LL &gt; CR &gt; NV &gt; HP. The effect of viscosity and polarity of the solvents on the degradation of the polycarbonate was also investigated. While the degradation rate decreased with viscosity, it increased with polarity for the solvents. © 2003 Wiley Periodicals, In6c. J Appl Polym Sci 91: 2391–2396, 2004

Blends of polycarbonate and ethylene-1-octylene copolymer

The mechanical properties and morphology of polycarbonate/ethylene-1-octylene copolymer (PC/POE) binary blends and PC/POE/ionomer ternary blends were investigated. The tensile strength and elongation at break of the PC/POE blends decreased with increasing the POE content. The impact strength of the PC/POE blends showed less dependence on thickness than that of PC. And the low-temperature impact strength of PC was modified effectively by addition of POE. The morphology of the PC/POE blends was observed by scanning electron microscope. The PC/POE weight ratio had a great effect on the morphology of the PC/POE blends. For the PC/POE (80/20)/ionomer ternary blends, low content (0.25 and 0.5 phr) of ionomer could increase the tensile properties of PC/POE (80/20) blend and had little effect on the impact strength. And 0.5 phr ionomer made the dispersed domain distribute more uniformly and finely than the blend without it. But with high content of ionomer, the degradation of PC made the mechanical properties of the blends deteriorate. Blending PC and ionomer proved the degradation of PC, and the molecular weight decreased with increasing the ionomer content.

Thermal and themoxidative degradation processes in poly(bisphenol a carbonate)

Progress in the study of thermal and thermoxidative decomposition processes of poly(bisphenol a carbonate) (PC) was obtained by Matrix assisted laser description ionization time of flight (MALDI-TOF) and FAB mass spectroscopic techniques. PC samples were subjected to thermal degradation (under inert atmosphere) heating at 300, 350, 400 and 450 °C. The MALDI mass spectra of the pyrolysis residues obtained at 300 °C showed only a progressive reduction of the abundance of cyclic oligomers and an increase of the molar mass of the PC sample most likely due to post-condensation polymerisation reactions. At 350 °C the occurrence of an extensive hydrolysis reaction producing phenol groups was observed. PC chains terminated with phenol groups together with chains bearing phenyl and isopropenyl end groups were observed at 400 °C. Condensed aromatic compounds such as xanthones were also detected in the MALDI spectra of PC samples heated at 400 °C, and they became the most intense species at 450 °C. The FAB-MS spectrum of the pyrolysis residue obtained at 400 °C subjected to a selective and exhaustive aminolysis reaction showed the presence of compounds containing several consecutive xanthone units. These units undergo cross-linking processes, leading to a graphite-like charred residue (insoluble), as the temperature increases. The thermoxidative degradation of PC carried out heating the samples in air at 300 °C for 30, 60, 90, 120, 150 and 180 min produced a reduction of the PC molar mass. The MALDI mass spectra of thermally oxidised PC samples at 300 °C for 90 and 180 min showed the presence of PC chains terminated with methyl-ketone, phenyl and phenol groups, most likely formed by the oxidative degradation of the isopropilidene bridge of bisphenol A units. The presence of dehydrogenated structures containing biphenyl linkage may account for the insoluble residue produced in these conditions.

The role of calcium ions in freezing injuries of winter oilseed rape leaves. Effects of calcium channel blockers and mimesis by calcium ionophore

Calcium ionophore A23187 allowing for a calcium ion influx from an apoplast to a cytoplasm, mimicked symptoms of the frost-induced injuries in winter oilseed rape leaves, as estimated by the conductivity method. Both calcium ionophore and freezing treatment induced degradation of phosphatidylcholine. On the other hand lanthanum and gadolinum ions as well as verapamil, the inhibitors of calcium ion channels, decreased the degree of the frost-induced injuries. Lanthanum ions prevented the frost-induced degradation of PC. It is proposed that freezing alters the functioning of calcium ion channels which results in calcium ion influx into a cytosol. This in turn may lead to a degradation of cell membranes.

Mucolipidosis type IV: abnormal transport of lipids to lysosomes.

Mucolipidosis type IV (MLIV) is a lysosomal storage disorder in which various phospholipids and gangliosides accumulate. The cause of this storage has not yet been identified. Loading experiments in cultured fibroblasts with radioactive phosphatidylcholine ([14C]PC) labelled either in the acyl groups or in the choline residue, indicated increased retention of this lipid in the lysosomes of these patients. Chase experiments in intact fibroblasts, on the other hand, indicated normal degradation and discharge of the radioactive PC in MLIV lysosomes. This was further supported by measurements of the degradation of [14C]PC by isolated lysosomes which indicated normal breakdown of PC in MLIV. Cultured fibroblasts from Hunter (MPSII) patients, which contain enlarged and numerous lysosomes, did not store [14C]PC when compared to normal controls, indicating that the storage of this lipid in MLIV is not a secondary phenomenon caused by the presence of enlarged and numerous lysosomes in these cells. Incubation of [14C]PC at 18 degrees C limits the endocytosis process only up to early endosomes. This temperature did not yield increased retention of [14C]PC in MLIV, indicating that accumulation occurs only after the PC reached late endosomes or the lysosomes. The data indicate that PC as well as other phospholipids and gangliosides accumulate in MLIV apparently owing to a defect in the endocytosis process of membranous components. This defect apparently leads to excessive transportation of these macromolecules into lysosomes rather than their recycling to the plasma membrane. The endocytosis of membrane components is different from receptor-mediated endocytosis which is not affected in MLIV. Once the membrane macromolecules reach the lysosomes in MLIV they are normally catabolized and normally discharged. This may explain the heterogeneity of the stored materials in MLIV. The normal catabolism of macromolecules in the lysosomes is reflected in the minor deterioration in the clinical manifestations of these patients.

REDISTRIBUTION AND VIRUS INACTIVATION EFFICACY OF A SILICON PHTHALOCYANINE IN RED BLOOD CELL CONCENTRATES AS A FUNCTION OF DELIVERY VEHICLE

The silicon phthalocyanine, HOSiPcOSi(CH3)2(CH2)3N(CH3)2 (Pc 4), is a new photosensitizer that can inactivate lipid-enveloped viruses in red blood cell concentrates (RBCC) upon exposure to red light. Because Pc 4 is insoluble in water, it was delivered either as an emulsion in saline and cremophor EL (CRM) or as a solution in dimethyl sulfoxide (DMSO). In RBCC, Pc 4 added in either vehicle distributed between the plasma and red blood cells (RBC) in a ratio of 4:6, similar to the ratio of these components in RBCC 3:7 (i.e. a hematocrit of 70%). Light exposure did not affect this distribution and caused only marginal degradation of Pc 4 at a light dose that inactivates > 5 log10 vesicular stomatitis virus (VSV). Among human plasma proteins, Pc 4 bound mainly (about 70%) to lipoproteins and to a lesser extent to albumin and lower molecular weight proteins when delivered in DMSO. When delivered in CRM, distribution between lipoproteins and albumin became more even. Among the lipoproteins Pc 4 bound almost exclusively to very low-density lipoproteins (VLDL) when delivered in DMSO and to both VLDL and low-density lipoproteins when added in CRM. The rate of VSV inactivation was independent of the delivery vehicle but there was less RBC damage, as measured by hemolysis during storage, when Pc 4 was added in CRM. These results indicate that using CRM as emulsifier can enhance the specificity of Pc 4-induced photochemical decontamination of RBCC for transfusion.

Fourier transform infrared spectroscopy investigations of polybenzimidazole/poly(bisphenol-A carbonate) blends

Abstract The results of a Fourier transform infrared spectroscopy (FTi.r.) study of the blend formed by poly(2,2′-m-phenylene)-5,5′-bibenzimidazole (PBI) and poly-[2,2-propane-bis(4-phenyl carbonate)] (PC) are discussed. The spectral features observed in the NH stretching and carbonyl stretching regions of all the compositions investigated have been interpreted in terms of hydrogen bonding interactions occurring between the NH groups of PBI and the CO groups of PC. Qualitative as well as quantitative information about these interactions has derived. The FTi.r. results indicate a high degree of molecular mixing between the two components at all blend compositions. A spectroscopic study as a function of temperature of a single blend composition ( 50 50 wt % ) is also reported. A quantitative analysis of the carbonyl region in the spectra yielded information about the onset temperature of large scale molecular mobility. A strong catalytic effect of PBI on the thermal degradation of PC was observed and is also discussed.

Catabolism of rat surfactant disaturated phosphatidylcholines during incubation of alveolar lavage materials in vitro at 37°C

Incubation of rat alveolar lavage materials in vitro at 37°C results in degradation of the endogenous surfactant disaturated phosphatidylcholines (disaturated PC). When exogenous dipalmitoylphosphatidylcholine (DPPC) vesicles are incubated with lavage materials, there is catabolism of the DPPC. The degradation process is temperature- and Ca 2+-dependent and has a pH optimum of 6.5–7.0. The products formed during catabolism of [ 3H]palmitate- and [ 14C]choline-labeled disaturated PC are free palmitate and water-soluble choline products. No lysophosphatidylcholines are formed. Measurements of lactate dehydrogenase levels in lavage fluid, use of more gentle lavage techniques, use of Ca 2+, Mg 2+ and protein in the lavage medium, and measurements of bacterial contamination all suggest that enzymes are neither released into pulmonary lavage fluid via cellular damage nor are bacterial in origin. Degradation of surfactant disaturated PC does not occur during incubation of lavage materials from rabbits, mice or guinea pigs. These results suggest that phospholipases and / or lysophospholipases are present in rat alveolar lavage materials. Possible origins of these enzymes are discussed.

Phosphatidylcholine and 4-methylumbelliferyl phosphorylcholine hydrolysis by purified placental sphingomyelinase.

We present evidence which indicates that highly purified placental acid sphingomyelinase hydrolyses [14C]phosphatidylcholine [( 14C]PC) and the synthetic phosphodiester 4-methylumbelliferyl phosphorylcholine (4-MUPC). Hydrolysis was achieved by phospholipase C phosphodiesterase action. Of the several detergents tested, sodium taurocholate alone was necessary for PC hydrolysis, while 4-MUPC was hydrolysed independent of any detergent requirement. The pH optima for the reactions were 4.6-4.8 for PC hydrolysis and 4.8-5.0 for 4-MUPC hydrolysis. As with sphingomyelin hydrolysis, degradation of both PC and 4-MUPC was inhibited by 5'-, 3'-, and 2'-AMP, 5'-AMP being the most effective of the three. Furthermore, the phosphodiesterase activity against PC and 4-MUPC copurified with sphingomyelinase from human placenta and cross-reacted with a specific anti-sphingomyelinase monoclonal antibody, strongly indicating identity of the phosphodiesterases. This explains phospholipase C deficiency in sphingomyelinase-deficient Niemann-Pick disease cells.

Stabilization of polycarbonate

The inhibiting activity of several organo-phosphorus stabilizers in thermal oxidation of polycarbonate (PS) prepared from 4,4′-dihydroxydiphenyl-2,2-propane was investigated by DTA and TGA according to absorption kinetics of oxygen, molecular weight variation and by UV spectroscopy. Many phosphites examined efficiently inhibit processes of degradation of PC in air at fairly high degrees of polymer conversion. With low degrees of conversion none of the stabilizers studied have a marked effect on DTA and TGA curves, absorption kinetics of oxygen and molecular weight variation. However, these stabilizers vary markedly in their effect on yellowing of PC in the initial period of oxidation. Some views are expressed concerning the possible mechanism of action of organo-phosphorus stabilizers.