Increase In Melting Temperature Research Articles

Influence of Process Parameters on the Morphologies of Micro-Injection Molded Polyformaldehyde Parts

Abstract The morphologies of micro-injection molded parts are influenced by the process parameters. In this paper, the influence of injection speed, mold temperature and melt temperature on the morphologies of micro-injection molded polyformaldehyde (POM) parts with different thicknesses were investigated by a single factor experimental method; the morphological structure of the parts was characterized by polarized light microscopy. The scale effect on the crystallization behavior and internal morphology of micro-injection POM parts was analyzed. The results indicated that the scale effect had a great influence on the hierarchical morphology in the thickness direction of the parts. The micro-parts with a thickness of 1.0 mm showed a skin-core structure including the skin layer, fine grain layer, oblate spherulite, and spherulite core layer, and the micro-parts with a thickness of 0.2 mm showed a skin-core structure with the skin layer, fine grain layer, and the spherulite core layer, and a larger thickness ratio of the spherulite core layer. As injection speed, mold temperature and melt temperature increase, the fine grain layer gradually disappears and the size of core spherulite tends to become larger, the thicknesses of the skin layer of all the micro-parts decrease and that of the 0.2 mm micro-parts decreases significantly.

Network connectivity and dissolution properties of sodium calcium phosphate glasses

Glasses of xCaO∙(80-x)P2O5·20Na2O system (0 ≤ x ≤ 30% mol %) with constant Na2O content were studied in order to evidence both structural and dissolution properties determined by CaO addition. Transparent vitreous samples were obtained in the investigated composition range. Thermal analysis evidenced the increase of both crystallisation and melting temperatures with CaO content. The relative mass loss of samples in simulated body fluid progressively increased with the extent of P2O5 substitution by CaO. The dissolution properties could be explained in relation with the structural changes concerning the PO4 units connectivity as pointed out by DTA and FTIR analysis.

High Pressure Thermodynamic Properties of Some Poly-Aromatic Hydrocarbons

We have measured the thermal behavior of four poly-aromatic hydrocarbons (PAHs) using high pressure gas flow DSC methods up to ∼7000 kPa. We have shown that there is a linear increase in melting temperature (T m) and heat of fusion () with increasing pressure for all materials studied (naphthalene, anthracene, pyrene, and phenanthrene). As part of the study we have developed in-house protocols to perform these rigorous measurements and we make recommendations to others who will utilize similar equipment which will ensure reliability and repeatability for the measurements performed using high pressure DSC methods.

Structure and properties of bio‐based polyamide 109 treated with superheated water

AbstractThe structure and properties of bio‐based polyamide 109 (PA109) after treatment with superheated water (140 °C ≤ T ≤ 280 °C) were investigated and characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, wide‐angle X‐ray diffraction, scanning electron microscopy and small‐angle X‐ray scattering. Below 170 °C, the hydrothermal treatment was considered to be a physical process, which exerted an annealing effect on PA109. It led to an increase in melting temperature, lamellar thickness and crystallinity, while the macromolecular structure, crystal structure and the order of crystalline regions were not affected. Above 170 °C, complete melting/dissolution of PA109 occurred with partial hydrolysis. Due to the high temperature and long reaction time, the hydrolysis reaction became more and more prominent, and the resin was completely hydrolyzed into oligomers at 280 °C. Also, above 170 °C, the hydrothermal treatment was accompanied by a chemical process and the melting temperature and molecular weight decreased progressively. Notably, the crystal structure was not altered, but the degree of perfection of crystals and the order of crystalline regions were broken, especially above 200 °C. The hydrolytic degradation reaction was significantly affected by temperature, while both time and the water to polyamide ratio were secondary factors which influenced it to a minor extent. The process could be considered as a typical nucleophilic substitution reaction which takes place step by step inducing the molecular weight to decrease gradually. Overall, this study provides a ‘green’ route for the processing, recycling and treatment of environmentally friendly polyamides based on hydrothermal treatment technology. © 2019 Society of Chemical Industry

Sinterization and hydration of synthesized cement clinker doped with sulfates

This paper aims to evaluate the influence of three kinds of sulfates from the green production of cement on its sintering and hydration. The properties of clinker and hydration were monitored by thermogravimetric and differential thermal analysis (TG–DTA), X-ray diffraction, X-ray fluorescence and isothermal conduction calorimeter. Results indicate that gypsum lowers the decomposition temperature of CaCO3 and all these Sulfates will enhance the solid-phase reaction but increase melting temperature. Sulfates reduce the content of C3S, but K2SO4 and 2CaSO4·K2SO4 is conducive to the formation of β-C2S. The hydration induction period is shortened by the sulfates. K2SO4 and 2CaSO4·K2SO4 improve the early hydration of clinker, but gypsum may lightly reduce the hydration reactivity of clinker in acceleration period. 2CaSO4·K2SO and K2SO can significantly accelerate the compressive strength development of cement clinker before 3 d; by contrast, gypsum is detrimental for that. The precipitation of hydration products (CH and C–S–H) in clinker with sulfates is more than that of clinker without sulfates at 9 h. K2SO4 can accelerate the hydration of clinker without forming ettringite.

The Effect of Melting Temperature on Coloration of TiO2–BaO–SiO2 Glass

TiO2–BaO–SiO2 glass have been prepared by melt quenching method. The enhancement of glass coloration was observed as melting temperature increase. UV-Vis-NIR spectrophotometer reveals the change of glass transmittance. And the Ti2p3/2 and O1s XPS results shows that Ti ions exist in the Ti3+ and Ti4+ state in glass, Ti3+ proportion increased as melting temperature increasing, while more fourfold coordination [TiO4] tetrahedron appeared as the substitute of sixfold coordination [TiO6] octahedron. According to the analytic results, we demonstrate that the lack of free oxygen in glass at high melting temperature cause the decrease of the valence and coordination for Ti, and the strong absorption of Ti3+ and [TiO4] enhances the coloration of glass.

Sepiolite / poly-3-hydroxyoctanoate nanocomposites: Effect of clay content on physical and biodegradation properties

Vinlytrimethoxy silane (VTMS) was grafted onto the pristine sepiolite. This VTMS containing sepiolite (VTMS-g-Sep) was used to prepare sepiolite/poly-3-hydroxyoctanoate (Sep/PHO) nanocomposites sheets by melt blending technique. Fourier transform infrared (FTIR) spectroscopy showed the formation of siloxane linkages in nanocomposites. Wide angle x-ray diffraction analysis indicated the formation of new crystal in nanocomposites. Thermal analysis demonstrated an increase in melting temperature of nanocomposite sheets. An increase of 1.4 and 16 folds in tensile strength and elongation at break of Sep/PHO nanocomposites was observed in comparison to PHO alone. The degradation studies of Sep/PHO nanocomposite were carried out both under in-vitro conditions and soil. Scanning electron microscopy showed the formation of agglomerates, grooves, and pits on the surface of Sep/PHO nanocomposite sheets buried in soil. FTIR analysis of the Sep/PHO nanocomposite sheets buried in soil showed a decrease in the intensities of the characteristic absorption bands at 2948 cm−1 (anti-symmetric stretching vibrations of the CH bonds) and 1730 cm−1 (carbonyl CO stretching vibration). While, intensities of absorption bands at 3670–3070 cm−1 (OH stretching vibrations) and 1050–1150 cm−1 (CO bending vibration) were increased after 90 days of soil burial.

Characterization of Microchannel Replicability of Injection Molded Electrophoresis Microfluidic Chips.

Microfluidic chips have been widely applied in biochemical analysis, DNA sequencing, and disease diagnosis due to their advantages of miniaturization, low consumption, rapid analysis, and automation. Injection molded microfluidic chips have attracted great attention because of their short processing time, low cost, and mass production. The microchannel is the critical element of a microfluidic chip, and thus the microchannel replicability directly affects the performance of the microfluidic chip. In the current paper, a new method is proposed to evaluate the replicability of the microchannel profile via the root mean square value of the actual profile curve and the ideal profile curve of the microchannel. To investigate the effects of injection molding parameters (i.e., mold temperature, melting temperature, holding pressure, holding time, and injection rate) on microchannel replicability, a series of single-factor experiments were carried out. The results showed that, within the investigated experimental range, the increase of mold temperature, melt temperature, holding pressure, holding time, and injection rate could improve microchannel replicability accuracy. Specifically, the microchannels along the flow direction of the polymer melt were significantly affected by the mold temperature and melt temperature. Moreover, the replicability of the microchannel was influenced by the distance from the injection gate. The effect of microchannel replication on electrophoresis was demonstrated by a protein electrophoresis experiment.

A Salt Bridge between α4 and α5 Helices Drives Differences in Flexibility and Potency of Inhibition among Regulator of G‐protein Signaling (RGS) Proteins

Regulators of G‐protein Signaling (RGS) proteins accelerate the rate of GTP hydrolysis, decreasing G‐protein signaling. Because there are many RGS isoforms with distinct tissue expressions, selective inhibition of RGS action may allow improved tissue specificity over global GPCR agonist application. RGS inhibitors discovered to date act by covalent modification of cysteine residues, and are specific for RGS4. However, single‐cysteine RGS mutants vary widely in their potency of inhibition by thiadiazolidinone (TDZD) inhibitors, with RGS19 being most potently inhibited. We have previously demonstrated a correlation between RGS protein flexibility and potency of inhibition by TDZDs. We hypothesized that differences in a salt bridge‐forming residue between the α4 and α5 helices drives differences in flexibility and potency of inhibition among RGS proteins.An acidic residue on the α4 helix that takes part in an α4‐α5 salt bride network is shared by RGS4 and RGS8 (D90 and E84 respectively), but not by RGS19 (L118). Upon mutation of RGS19 to induce formation of this salt bridge (L118D), the protein became 7°C more stable than WT, as measured by DSF. A mutation that removed this salt bridge in other isoforms caused an increase in melt temperature of 5°C in RGS4 (D90L) and a decrease in melt temperature of 8°C in RGS8 (E84L). Hydrogen‐deuterium exchange was used to evaluate the flexibility of mutant proteins. The α4 helix, which contains the mutation site, was found to be protected from deuterium exchange on addition of a salt bridge (RGS19 L118D), but have higher exchange compared to WT in both mutants where a salt bridge was removed (RGS4 D90L and RGS8 E84L). Changes in the α4 salt bridge‐forming residue also induced changes in the potency of inhibition of Gα binding by TDZD inhibitor CCG‐50014. RGS19 L118D had a lower potency of inhibition than WT RGS19, while mutations at RGS4 D90L and RGS8 E85L increased potency of inhibition compared to WT proteins. Together, these results show that differences in an α4 salt bridge‐forming residue are responsible for flexibility differences among RGS isoforms, and demonstrate a causal relationship between RGS protein flexibility and potency of TDZD inhibitors.Support or Funding InformationNSF grant 1507588This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effect of injection compression process parameters on residual stress of products based on numerical simulation

With the maximum residual stress of Mises-Hencky as the index, a numerical model for injection compression molding of the disc was established by CAE software. The process parameters of 7 factors including mold temperature, melt temperature, pressure holding time were analyzed by orthogonal experiment. Effect of key process parameters on residual stress was studied by single factor method finally. The results show that effect of mold temperature on residual stress was greatest, followed by melt temperature, compression delay time and compression speed, the residual stress decreases with the increase of mold temperature and melt temperature, increases with the increase of compression delay time, and the effect of compression speed on residual stress is not obvious.

A biophysical insight into structural and functional state of human serum albumin in uremia mimic milieu.

In chronic kidney diseases (CKD), uremic toxins accumulate in the blood plasma of patients and interact with human serum albumin (HSA) and thus impaired its role as carrier protein. Present study shows in vitro effect of carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF), indoxyl sulfate (IS), indole-3 acetic acid (IAA), and hippuric acid (HA) with human serum albumin (HSA) at pathological concentrations. HSA bind with CMPF, IS and IAA at both of its binding sites with high affinity (order of 105 to 106 M-1) and low affinity (order of 103 to 105 M-1). Under pathological concentrations CMPF, IS, IAA and HA induce marked secondary structural alterations in HSA as observed by FTIR and CD measurements. Differential scanning calorimetry results show an increase in melting temperature (Tm) of HSA under mimicked pathological condition. Furthermore, hydrolase activity of HSA decreases in presence of CMPF, IS, IAA and HA as of their binding in vicinity of active site.

Features of a control blade degradation observed in situ during severe accident conditions in boiling water reactors

ABSTRACT In the present paper, new results using in situ video are presented regarding boiling water reactor (BWR) control blade degradation up to 1750 K at the beginning of a nuclear severe accident. Energy-dispersive X-ray spectrometry (EDS) mapping indicated stratification of the absorber blade melt with formation of a chromium and boride-enriched layer. High-content-B- and C-containing material with increased melting temperature acted like a shielding and was found to prevent further relocation of control blade claddings. The interacted layers around the B4C-granules prevented direct steam attack of residual B4C. The results provide new insights for understanding of the absorber blade degradation mechanism under reducing conditions specific to Fukushima Dai-Ichi Unit 2 resulting from prolonged steam starvation.

B-factor Guided Proline Substitutions in Chromobacterium violaceum Amine Transaminase: Evaluation of the Proline Rule as a Method for Enzyme Stabilization.

Biocatalysis is attracting interest in the chemical industry as a sustainable alternative in large‐scale chemical transformations. However, low operational stability of naturally evolved enzymes is a challenge and major efforts are required to engineer protein stability, usually by directed evolution. The development of methods for protein stabilization based on rational design is of great interest, as it would minimize the efforts needed to generate stable enzymes. Here we present a rational design strategy based on proline substitutions in flexible areas of the protein identified by analyzing B‐factors. Several proline substitutions in the amine transaminase from Chromobacterium violaceum were shown to have a positive impact on stability with increased half‐life at 60 °C by a factor of 2.7 (variant K69P/D218P/K304P/R432P) as well as increased melting temperature by 8.3 °C (variant K167P). Finally, the presented method utilizing B‐factor analysis in combination with the proline rule was deemed successful at increasing the stability of this enzyme.

A Phenol-containing α-Diimine Ligand for Nickel- and Palladium-Catalyzed Ethylene Polymerization

A phenol-containing dibenzhydryl-based α-diimine ligand bearing hydroxy group on para-position of aniline moiety was designed, synthesized, and investigated in Ni- and Pd-catalyzed ethylene polymerization. The Ni complex bearing hydroxy groups resulted in not only high polyethylene molecular weight (Mn up to 1.5 × 106), but also significantly increased melting temperature (Tm up to 123 °C) and greatly decreased branching density (33/1000C) versus the Ni catalyst bearing OMe group on para-position of aniline moiety. This is consistent with the hypothesis that the deprotonation of the phenol moiety generated a phenoxide bearing strong electrondonating O− substituent by methylaluminoxane (MAO) cocatalyst. The Pd complexes bearing hydroxy groups exhibited similar catalytic properties to those of the Pd catalyst bearing OMe groups did.

Interactions between a Bioflavonoid and G-Quadruplex DNA at the Ensemble and Single-Molecule Level

G-Quadruplex (GQ) DNA has garnered the attention of the scientific community due to its role in important biological processes like telomerase activity inhibition, regulation of gene expression and genomic stability. This has triggered studies on understanding the interactions of GQ with small molecules of therapeutic significance. We have studied the interactions of bioflavonoid kaempferol (3,4',5,7-tetrahydroxyflavone, KF), known for its anti-cancer properties, with a c-myc promoter-based GQ at the ensemble and single-molecule level. The binding constant (Kb) is estimated using steady state and time-resolved fluorescence measurements. Upon binding no structural perturbation of GQ is observable from the circular dichroism (CD) data. However, an increase in melting temperature of GQ upon binding suggests stabilization of the DNA structure by the ligand, an observation substantiated by the ensemble FRET experiments. Fluorescence correlation spectroscopy (FCS) measurements, which probe the interactions at the single-molecule level, reveal a progressive increase in the diffusion time of KF with increase in the amount of GQ confirming the binding event. The rate constants of the association (k+) and dissociation (k-) processes have been estimated from the FCS time profiles. The nature of the binding interactions and possible binding site of KF in GQ have been determined from the molecular docking studies. The above findings are expected to enhance our understanding of flavonoid-GQ DNA interactions for development of therapies involving quadruplex DNA.

Maturation and rejuvenation of a silicic magma reservoir: High-resolution chronology of the Kneeling Nun Tuff

Knowledge of the conditions of magma storage prior to volcanic eruptions is key to their forecasting, yet little is known about how melt compositions, crystallinity and intensive parameters within individual magma reservoirs evolve over time. To address this, we studied the Kneeling Nun Tuff, a voluminous (>900 km3) deposit of an Eocene caldera-forming eruption from the Mogollon–Datil volcanic field in New Mexico, USA. Whole-rock, feldspar and amphibole compositions were combined with zircon trace-element geochemistry and precise isotope dilution-thermal ionisation mass spectrometry (ID-TIMS) U–Pb zircon crystallisation ages to arrive at a detailed, time-resolved record of chemical and physical changes within the voluminous, upper-crustal (∼2.2 kbar) magma reservoir. Chemical compositions and zircon ages from the Kneeling Nun Tuff and from co-magmatic clasts hosted within it reveal prolonged (>1.5 million years) growth and maturation of the magma reservoir that was heterogeneous in terms of temperature, melt composition and crystallinity. This protracted storage at a dominant crystallinity in excess of 50% culminated in a period of ca. 50 ky of increase in recharge heat supply and related homogenisation, decrease in crystallinity to 40–50%, and potential increase in average melt temperature, leading up to eruption at 35.299 ± 0.039 Ma. Sampling of co-magmatic lithic clasts derived from early-cooled domains of the reservoir shows that the long, million year-scale maturation time is shared across all erupted domains of the magmatic system, irrespective of their final cooling history. This study provides key observations from a natural system against which thermal and mechanical models of upper-crustal magma reservoir construction can be validated.

Aptamer-induced thermofluorimetric protein stabilization and G-quadruplex nucleic acid staining by SYPRO orange dye

Serendipitously discovered nucleic acid staining by SYPRO Orange dye utilized to demonstrate proteins thermal stabilization (increase in melting temperature,Tm) as a function of increased DNA aptamer binding affinity (decrease in dissociation constant,Kd).

Melt Shear Rheology and pVT Behavior of Polypropylene / Multi-Walled Carbon Nanotube Composites

In this study, capillary rheological tests were performed on polypropylene filled with multi-walled carbon nanotubes (PP/MWCNT) to determine the melt flow curves and pressure-Volume-Temperature (pVT) diagrams. Based on the experimental data, master viscosity curves were constructed using the time-temperature-superposition principle and the Cross and Carreau-Winter models, while the pVT data were fitted to the Tait equation in both liquid and solid states. Results show that the melt shear viscosity decreases with increasing melt temperature and shear rate and increases with MWCNT wt.%. All composites display shear-thinning behavior in the range of medium to high shear rates. The specific volume of PP/MWCNT composite decreases with increasing MWCNT wt.% and pressure and increases with increasing temperature.

The effect of bioactive glass nanoparticles on polycaprolactone/chitosan scaffold: Melting enthalpy and cell viability

Bioactive glass nanoparticles were synthesized by sol–gel method. The composite nanofiber of the polycaprolactone/Chitosan/bioactive glass scaffolds for tissue engineering is successfully fabricated by electrospinning technology. Transmission electron microscope analysis showed that the synthesized nanoparticles had a spherical shape and uniform structure. The results of scanning electron microscope and atomic force microscope revealed that the electrospun fibers had a smooth and uniform morphology, and the average diameter of electrospun nanofibers decreased with increase in the bioactive glass nanoparticles. Also, surface roughness significantly increased by adding nano-bioactive glass loading. Functional and mineral groups of scaffold materials were confirmed by Fourier transform infrared and energy dispersive X-ray tests. The presence of bioactive glass into the scaffold, hydrophilicity, melting temperature, and cell proliferation increases. Furthermore, the nanoparticles reduce the melting enthalpy of the membrane by changing the polymer molecular structure. Following the reduction of enthalpy, Gibbs free energy is also decreased and the reactivity of nano-bioactive glass in the polymeric chain increases. In order to evaluate the cytotoxicity of polycaprolactone/Chitosan/bioactive glass nanofibers, human gingival fibroblast cells were cultured. Attachment and proliferation of the human gingival fibroblast cells on polycaprolactone/Chitosan/bioactive glass scaffolds were significantly better than the polycaprolactone/Chitosan composite. We expect electrospun scaffold containing polycaprolactone/Chitosan/bioactive glass is promising for cartilage regeneration.

A novel crucible-less inert gas atomisation method of producing titanium powder for additive manufacturing

ABSTRACTA novel low-cost gas atomisation technology producing spherical titanium powder (wire induction heating gas atomisation, WIGA) has been developed for additive manufacturing. Combined with the gas atomisation principle, the characteristics of WIGA were analysed. The effects of the gas pressure, metal temperature and the wire-feeding speed on the particle size of the titanium powder were studied. The results indicated that the decreases in mass median particle diameter (D50) and the increases in efficiency of fine size powders occurred with the increase in gas atomisation pressure and melting temperature and with the decrease of wire-feed speed. The optimum parameters are that the main gas pressure (P0) is 4.0 MPa, the degree of superheat of the metal melt is 350°C and the wire-feed speed is 50 mm s−1. On the condition, the D50 of titanium powder was 40.2 μm and powder morphology was spherical. Satellites rarely existed on the surface of particles.