Dynamical Mechanical Thermoanalysis of High Performance Reinforced Materials Influences and Problems

A sensitive method to characterize the thermomechanical behaviour of fiber reinforced composites is the dynamic mechanical thermoanalysis (DMTA) method. A Round-Robin-test with five different institutes was conducted to determine the role of the fiber orientation, processing conditions, test apparatus, the mode of loading, and the matrix materials on the determination of the glass transition temperature (T_g). The result shows that the DMTA is a suitable method to analyze T_g of long fiber composites. However, some major problems have to be taken into consideration: - A direct comparison of results from different DMTA-systems is not possible - The real temperatures in the specimens deviate from the temperatures displayed by the DMTA measuring system - There is no clear and common evaluation method for the glass transition temperature. This revised version was published online in August 2006 with corrections to the Cover Date.     

Comparison of three methods for fractionation and enrichment of low molecular weight proteins for SELDI-TOF-MS differential analysis

In most diseases, the clinical need for serum/plasma markers has never been so crucial, not only for diagnosis, but also for the selection of the most efficient therapies, as well as exclusion of ineffective or toxic treatment. Due to the high sample complexity, prefractionation is essential for exploring the deep proteome and finding specific markers.In this study, three different sample preparation methods (i.e., highly abundant protein precipitation, restricted access materials (RAM) combined with IMAC chromatography and peptide ligand affinity beads) were investigated in order to select the best fractionation step for further differential proteomic experiments focusing on the LMW proteome (MW inferior to 40,000 Da). Indeed, the aim was not to cover the entire plasma/serum proteome, but to enrich potentially interesting tissue leakage proteins. These three methods were evaluated on their reproducibility, on the SELDI-TOF-MS peptide/protein peaks generated after fractionation and on the information supplied.The studied methods appeared to give complementary information and presented good reproducibility (below 20%). Peptide ligand affinity beads were found to provide efficient depletion of HMW proteins and peak enrichment in protein/peptide profiles.     

Sums Over States of the Atoms and Singly and Doubly Charged Ions of Rare-Earth Elements

The sums over states of the atoms and singly and doubly charged ions of rare-earth elements that are required for a theoretical study of thermochemical processes in high-temperature plasma spectral sources are calculated in the temperature range 2500–12,000 K.     

Synthesis and Characterization of Liquid Crystal with Lower Temperature of Phase Change of meso-tetra-(4-n-lauroyloxyphenyl)porphyrin

Metalloporphyrincomplexeshavebeenextensivelystudiedinmanyfunctionalchemistrytieldssuchasphoto-eletronicconversionnon-linearoptics,biomimeticstudiesandcatalyticefttcts.TOourknowledge,thefirstliquidcrystallineporphyrinwassynthesizedbyGoodbyelall.In1987,Greggetapreportedthesynthesisandtheliquidcrystallinepropertiesofaseriesofporphyrinoctanolesters.In1987,Greggelal3synthesizedoctakis(0-hydroxyethyl)porphyrin.In1991,tetrakis(4-n-lauroylphenyl)porphyrinwaspreparedbyShimizuetal#.In1994,5.15-disubs…     

High pressure,high temperature reaction vessel for extremely corrosive media

Abstract

A fully automated high temperature (800 deg C) high pressure (1000 bar) reaction vessel for extremely corrosive media is depicted.     

Soluble polybenzimidazoles with intrinsic porosity: Synthesis,structure, properties and processability

We have explored two novel comonomers, namely, 4,16‐dicarboxyl[2.2]paracyclophane and 5,5′,6,6′‐tetraamino‐3,3,3′,3′‐tetramethyl‐1,1′‐spirobi[indane], for the synthesis of co‐polybenzimidazoles (co‐PBIs) with intrinsic porosity. Both these monomers possess twisted structures that can lead to “awkward” macromolecular shapes that cannot pack efficiently. The consequences of introducing these two monomers on the structure and properties of PBIs are reported. The random copolymers synthesized are amorphous and possess glass transition temperatures (T_gs) greater than 400 °C. T_g decreases with increasing comonomer content indicating an increase in fractional free volume. The copolymers have low surface area. TEM and BET measurements show evidence of mesopore formation. The copolymers show significant carbon dioxide adsorption. Single chain molecular dynamics simulation of 24‐mer repeat units shows intramolecular void spaces arising as a result of distorted polymer chain with reduced conformational mobility. These studies define a new synthetic strategy for “bottoms‐up” synthesis of PBIs with intrinsic porosity. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1046–1057     

Synthesis of gradient copolymers with simultaneously tailor‐made chain composition distribution and glass transition temperature by semibatch ATRP: From modeling to application

Recent studies have demonstrated that gradient copolymers exhibit unique thermal properties. Although these properties can be determined by copolymer composition, other factors such as chain and sequence lengths and their distributions can also influence them. Accordingly, the synthesis of gradient copolymers requires simultaneously tailor‐made chain structure and thermal properties. In this work, we carried out a systematic study on the preparation of poly(methyl methacrylate‐grad‐2‐hydroxyethyl methacrylate) [poly(MMA‐grad‐HEMA)] with synchronously tailor‐made chain composition distribution and glass transition temperature (T_g) through semibatch atom transfer radical polymerization. First, a comprehensive model for simultaneously predicting gradient copolymer microstructure and T_g was presented using the concept of pseudo‐kinetic rate coefficients and Johnston equation. The model was validated by comparing simulation results with the classical reference data. Furthermore, the model was used to guide the experimental synthesis of the poly(MMA‐grad‐HEMA) gradient copolymers potentially as excellent damping material. The thermal properties of these gradient copolymer samples were evaluated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Effect of low-temperature processing on dry film photoresist properties for flexible electronics

This study presents the mechanical characterization of the dry film photoresist PerMX and its adhesion properties when laminated onto Kapton® E (PI) and Melinex® ST506 (PET). Additionally, the processing temperature, the adhesion strength, and the neutral plane position are investigated and optimized. A relatively low-temperature (85 °C) process is developed to protect the integrity of the polymers with low glass transition temperature and reduce the thermal mismatch stress. Reduction in processing temperature led to a decrement in the adhesion strength. To counteract this unwanted effect, surface treatments (oxygen plasma) are performed on the polymer surface before lamination. Using the latter techniques, adhesion of PerMX to PET (hard bake: 1 h at 85 °C) is increased from 0.07 to 0.26 N mm⁻¹ (variation of 270%). Finally, the mechanical robustness is investigated and increased by tuning the position of the neutral plane, after 50,000 bending cycles and a radius of curvature of 2.5 mm. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Molecular weight effects on gelation and rheological properties of konjac glucomannan–xanthan mixtures

Fractions of konjac glucomannan (KGM) with various viscosity‐average molecular weights (M_v) ranging from 4.00 × 10⁵ to 2.50 × 10⁶ were prepared by hydrolysis degradation in hydrochloride acid/ethanol. Effect of M_v of KGM on the critical gelation temperature (T_gel) determined by Winter–Chambon criterion and the elasticity of KGM/xanthan mixed gels, a kind of binary gel formed by synergistic gelation, were investigated by dynamic viscoelastic measurements. It was shown that the value of T_gel of the gel was shifted to a higher temperature and the gel strength was enhanced when M_v of KGM was increased. The critical M_v (1.91 × 10⁶) was observed, above which the T_gel and elasticity of the mixed gels showed no or slight increase. It was suggested that T_gel and elasticity of KGM/xanthan mixed gels mainly depend on the structure of junction zones driven by the strong interaction between KGM and xanthan, which was gradually improved with increasing M_v of KGM. It was found that the critical strain and yield stress of the mixed gels increased monotonically with the increasing M_v of KGM. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 313–321, 2010     

Approach to thermal properties and electronic polarizability from average single bond strength in ZnOBi2O3B2O3 glasses

The glass transition temperature (T_g), density, refractive index, Raman scattering spectra, and X-ray photoelectron spectra (XPS) for xZnO-yBi₂O₃-zB₂O₃ glasses (x=10-65, y=10-50, z=25-60 mol%) are measured to clarify the bonding and structure features of the glasses with large amounts of ZnO. The average electronic polarizability of oxide ions (α_O2−) and optical basicity (Λ) of the glasses estimated using Lorentz-Lorenz equation increase with increasing ZnO or Bi₂O₃ content, giving the values of α_O2−=1.963 Å³ and Λ=0.819 for 60ZnO-10Bi₂O₃-30B₂O₃ glass. The formation of BOBi and BOZn bridging bonds in the glass structure is suggested from Raman and XPS spectra. The average single bond strength (B_MO) proposed by Dimitrov and Komatsu is applied to the glasses and is calculated using single bond strengths of 150.6 kJ/mol for ZnO bonds in ZnO₄ groups, 102.5 kJ/mol for BiO bonds in BiO₆ groups, 498 kJ/mol for BO bonds in BO₃ groups, and 373 kJ/mol for BO bonds in BO₄ groups. Good correlations are observed between T_g and B_MO, Λ and B_MO, and T_g and Λ, proposing that the average single bond strength is a good parameter for understanding thermal and optical properties of ZnOBi₂O₃B₂O₃ glasses.