DSC Investigations Research Articles

Block phosphorus-containing poly(trimethylene terephthalate) copolyester via solid-state polymerization: Reaction kinetics and sequential distribution

Phosphorus-containing flame-retardant monomer entitled 9,10-dihydro-10-[2,3-di(hydroxycarbonyl)propyl]-10-phospha-phenanthrene-10-oxide (DDP) was first esterified with 1,3-propane diol, then incorporated in poly(trimethylene terephthalate) (PTT) chain via solid-state polymerization (SSP) at 200 °C. Reaction kinetics of incorporation was studied choosing 30 wt% DDP content as representative example. The reaction rate constant kf was calculated to be 1.68 h−1. The intrinsic viscosity increased with the increase of tssp, and decreased with the increase of DDP content. The sequence distribution of resulted copolyester was also analyzed with 1H NMR. Results suggested that all of the samples possess block chemical structure, and the degree of randomness increased with the increase of transesterification. For the transesterification reaction occurs only in amorphous phase of the material, the copolyester exhibited greater tendency to form block constitution when increasing DDP content. DSC investigation further confirmed the non-random constitution of the resulted copolyester.

Microstructure and Thermal Analysis of Mg-Al-Ca-Sr Alloys

The paper presents results of DSC and microstructural investigations of Mg-6Al-1Ca-1Sr-0.3Mn (ACJ611) and Mg-8Al-3Ca-1Sr-0.2Mn (ACJ831) magnesium alloy in as cast condition. The microstructure of this alloy consists of aluminum in magnesium solid solution and two types of eutectic: α-Mg+Al2Ca and α-Mg+Al3Mg13Sr. The liquidus temperature of ACJ611 magnesium alloy is 613°C. The eutectic reactions L α-Mg+Al2Ca and Lα-Mg+Al3Mg13Sr occurs at 510°C and 502°C temperatures, respectively. The increase of aluminum and calcium content increases the volume fraction of Al2Ca phase, decreases the liquidus temperature and slightly increases the temperature of eutectic reactions.

Self-Limited to Parabolic Grain Growth Kinetics in Metal Oxide Thin Films

Distinctive microstructure engineering of amorphous to nanocrystalline electroceramic thin films is of high relevance for integration in low to high temperature operating MEMS-devices. Up to now, kinetic rules of nucleation, crystallization and grain growth of precipitation-based ceramic thin films are unknown. In this study, general rules for the crystallization and grain growth kinetics of a pure single-phase metal oxide thin film with only one kind of cation, i.e. ceria, made by spray pyrolysis from a precursor with one single organic solvent is discussed [1,. The near-and long range disorder is studied via Raman, DSC investigation of crystallization enthalpy, XRD, SEM and TEM for amorphous to fully crystalline state. These 400 nm thick-thin films were dense, crack-free and amorphous directly after deposition on a sapphire substrate. Briefly, above deposition temperature crystallization sets in with respect to temperature and persists over a broad temperature range from 400 to 950°C. In this regime, biphasic amorphous-crystallien films exist and grain growth proceeds simultaneously to crystallization. Isothermal grain growth studies showed that after short dwell times of 10-20h stable microstructures established following self-limited grain growth law [. In this state, driving force for the crystallization is the reduction of free enthalpy for phase transformation and interface diffusion prevails. A transition to classical grain curvature-driven parabolic grain growth kinetics appeared once the material reached the fully crystalline state for average grain sizes larger than 140 nm and higher annealing temperatures. Volume diffusion was then activated in addition to the interface diffusion. It was found that once crystallized the material shows independent on processing route equal XRD density and microstrain, as well as Raman characteristics. However, dependent on processing conditions i.e. choice of organic and, according, deposition temperature of the film amorphous states vary and affect strongly crystallization and grain growth history for the biphasic films.

Improved dissolution rate and bioavailability of fenofibrate pellets prepared by wet-milled-drug layering

Objective: The objective of this study is to investigate the wet-milled-drug layering process which could significantly improve the dissolution rate and oral bioavailability of fenofibrate pellets.Methods: Fenofibrate was milled with HPMC-E5 to prepare a uniform suspension in the micrometer and nanometer range, and this suspension was then layered on to sugar spheres to form the pellets (F1, F2).Results: The particle size was significantly reduced (from 1000 µm to 1–10 µm and 400 nm) but the fenofibrate in suspension retained its crystallinity from the results of DSC and PXRD investigations. The dissolution rate of F1-F2 and Antara® capsules was 55.47 %, 61.27 % and 58.43 %, respectively, in 0.01 mol/L SDS solution over 60 min. In addition, F1, F2, and Antara® capsules were given orally to 6 beagle dogs to determine the bioavailability. The Cmax of F1, F2 (8.21 ± 2.55 and 9.33 ± 2.37 μg/mL)and the AUC(0−t) of F1, F2 (152.46 ± 78.89 and 172.17 ± 67.58 μg/mL·h)were higher than those of Antara® (6.02 ± 3.34 μg/mL and 89.82 ± 46.46 μg/mL·h) and, F1, F2 reached their Cmax earlier than Antara® (F1: 2.0 ± 1.1 h; F2: 1.8 ± 1.2 h; Antara®: 6.0 ± 8.9 h).Conclusion: These results show that the wet-milled-drug layering technique is a powerful method to improve the dissolution rate and the bioavailability of fenofibrate.

CD and DSC Investigation of Individual and Complex Influence of Meso-Tetra(4-Oxiethylpyridil) Porphyrin (TOEPyP4) and Its Zn-Complex on DNA

CD spectra of (DNA-TOEPyP4) + ZnTOEPyP4, (DNA-ZnTOEPyP4) + TOEPyP4, and DNA + (TOEPyP4-ZnTO- EPyP4) complexes have been studied. It is shown that CD spectra of these triple complexes significantly differ from the DNA-TOEPyP4 and DNA-ZnTOEPyP4 double complex spectra, and they are not sum of these double complexes. Especially some strong differences in CD spectra of the triple and double complexes were observed when both porphyrins were added simultaneously into the DNA solution. In this case, ZnTOEPyP4 revealed a dominant influence on CD spectrum form. Zn-porphyrin also caused a strong intensity of positive band at 416 nm and a negative band at 437 nm when it was added into solution containing the DNA-TOEPyP4 complex. On the basis of obtained data, it was supposed that the observed significant changes in CD spectra of triple complexes were connected to an altered DNA conformation initiated by intercalation of porphyrin TOEPyP4 into GC-rich sites. The melting process analysis of the double complexes was carried out. The mechanisms of individual and joint influence of the porphyrins on DNA, and influence of binding modes on stability of these complexes are also discussed.

Effect of 2,2‐dimethyl malonate on the volume shrinkage control of the CaCO3/unsaturated polyester resin composites

AbstractShrinkage is critical to the unsaturated polyester resin (UPR) composite materials. Shrinkage influences the surface appearance, thus leading to warpage, internal cracks, and depression on the surface of the composite materials' products. Some studies and technologies have been conducted to controll the shrinkage. In this study, we presented 2,2‐dimethyl malonate as an anti‐shrinkage agent, which was different from the previous thermoplastic macromolecular agents. The shrinkage level of the CaCO3/UPR matrix dropped to zero with 12% 2,2‐dimethyl malonate by mass of UPR. The bending strength of CaCO3/UPR matrix with 2,2‐dimethyl malonate was also higher than that with the same adding amount of commercial thermoplastic agents at the low‐shrinkage level (below 0.25%) and the micro‐shrinkage level (below 0.08%). A reaction including two stages was proposed on the supporting of DSC and FTIR investigations. From the analysis results, we deduced that the first stage of the reaction was the esterification between 2,2‐dimethyl malonate and UPR, which did not occur in the UPR containing general thermoplastic anti‐shrinkage agent, and the second stage was restraining the cross polymerization of UPR, same to the reaction processes of general macromolecular anti‐shrinkage agents. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

DSC investigation of the polystyrene films filled with fullerene

Abstract Polystyrene composite films with different content of C60 + C70 fullerene mix have been obtained from o-xylene solutions. The mass fraction of fullerene was varied from 0.01 to 0.1 mass%. The glass transition temperatures and specific heat capacities in range of 293–423 K have been determined for the films by DSC method. The plasticization of the polymer is observed in thermal properties of the films under influence of small fullerene additions. The values of Tg and CP decrease and thermal coefficient of heat capacity b increase as fullerene content increases up to 0.02 mass%. The effect of interaction between polymer and fullerene molecules on thermal properties becomes evident at higher fullerene content in range from 0.02 to 0.1 mass%. At this the values of Tg and CP increase and b coefficient decrease with increasing content of fullerene. Concentration dependence of CP and b values is less steep for polymer composite films in elastic state at temperatures above Tg. Molecular interactions in t...

Synthesis and Thermal Properties of Linear Amphiphilic Diblock Copolymers of l-Lactide and 2-Dimethylaminoethyl Methacrylate

A well-defined series of nine poly(l-lactide)-b-(2-dimethylaminoethyl methacrylate) (PLLA-b-PDMAEMA) linear diblock copolymers with low polydispersity were prepared by ring-opening polymerization of LLA using 4-isopropylbenzyl alcohol and tin octoate as the initiating system, conversion of the OH-terminated PLLA into Br-terminated macroinitiators (5, 13, and 19 kg/mol), followed by atom transfer radical polymerization of DMAEMA (to obtain one-half, equal, and twice the molecular weight of each PLLA block). Compositional analysis and molecular weight characterization were done using NMR, SEC–LS, TGA, polarimetry, and PDMAEMA quaternization/precipitation to test for residual PLLA homopolymer. DSC investigations indicate that low molecular weight amorphous PLLA or PDMAEMA blocks (less than or equal to ca. 5000 g/mol) are miscible in the second block. Compared to the parent PLLA homopolymers, PLLA crystallization in the block copolymers is significantly retarded, whereas the degree of crystallinity is only mildly affected and melting points are reduced only for the low molecular weight miscible blocks.

DSC investigations of the surface layer of an aged polypropylene/wood composite

DSC investigations of the surface layer of an aged polypropylene/wood composite

LDPE/EVA/PCR/MWNT nanocomposites: Radiation crosslinking and physicomechanical characteristics

AbstractNanocomposites of low‐density polyethylene (LDPE)/ethyl vinyl acetate (EVA)/poly(chloroprene) rubber (PCR) blends and multiple walled carbon nanotubes (MWNT) were prepared in different compositions by melt mixing. The nanocomposites were subjected to different radiation doses and efficacy of radiation crosslinking and physic‐mechanical characteristics were analyzed in detail. Gel content and crosslinking density increased with dose and with the MWNT fraction in the nanocomposites. The elastic modulus of the nanocomposite increased, while elongation at break exhibited downward trend with radiation dose. Micromechanical modeling of elastic modulus indicated presence of agglomeration in the matrix. Bulk density of the nanocomposites increased with the addition of MWNT while the melt flow index of the nanocomposites decreased sharply. DSC, XRD and TGA investigations revealed the peculiarity of the MWNT led nucleation in LDPE/EVA/PCR/MWNT nanocomposites. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Latent ruthenium initiators containing fluoro aryloxide ligands

A new ligand, methyl 2,3,5,6-tetrafluoro-4-oxybenzoate (C 8H 3F 4O 3), combining an electron withdrawing group (C 6F 4) to tune the reactivity with an anchor group (CO 2Me) for immobilization on supports, was used to prepare four new ruthenium initiators, viz. Ru(C 8H 3F 4O 3) 2( CHPh)(3-Br–C 5H 5N)(H 2IMes) and Ru(C 8H 3F 4O 3) 2XL, where X = C,N-( CHCH 2CH 2-2-C 5H 4N) and L = P i Pr 3, PCy 3 or H 2IMes. The new ligand greatly reduced the reactivity of the ruthenium centre at room temperature. The 1H NMR and DSC investigation for the ROMP of norbornene dicarboximide monomers clearly demonstrated that the Ru(C 8H 3F 4O 3) 2XL initiators were inactive at room temperature and required elevated temperatures for their activation.

TEM and DSC Investigation of the Recovery of a Recycled Aluminum Processed by Equal Channel Angular Extrusion

TEM investigation was performed on a recycled aluminum processed by Equal Channel Angular Extrusion. The aluminum contains many inclusions which were identified to be rich in iron and silicon.This has a substantial effect in dragging recovery. ECAE was performed via routes B and C using a die formed by two channels characterized by the well defined angles =90° and  = 90°. The evolution of the microstructure seems to be similar whether using route B or C. a high dislocation density was introduced since the first passage together with a high density of Frank dislocation loops. The latter are due to a by-passing of inclusions by cross-slip mechanism. Weak beam experiments enable us to investigate the early stages of recovery consisting in the formation of dislocation walls and few dislocation cells. A partial arrangement of dislocations was observed since the first passage through the die. The formation of dislocation cells began already before annealing and progresses at more elevated temperatures. The substantive recovery seems to push recrystallization process to high temperatures. By contrast, DSC investigations show a significant difference: The amount of energy deduced from the area of the peak relative to recrystallization is higher when using route C.

Effect of Heat Treatment Conditions on Microstructure and Infrared Transmission Property of Germanate Oxyfluoride Glass-Ceramics

Germanate oxyfluoride glass in CaF2/BaF2-AlF3-SiO2-GeO2 was prepared by melt quenching technique and subsequently converted to glass-ceramics with microstructures comprised nano-crystallites in a residual glass matrix by two-step heat treatments process. DSC, XRD, SEM and IR transmission investigations were used to determine structural characteristics and optical property of the prepared germanate oxyfluoride glass-ceramics. The influences of heat treatment conditions on crystallization behaviors and infrared transmission were discussed. The results show that crystal phase in the glass-ceramics is only Ge2Al6O13 and the crystal size is about 20nm-80nm when treated temperature ranges from 900 oC to 960oC. Good transparency is exhibited in visible light band to midinfrared band (5.0um) when treated temperature is low than 940 oC.

Thermodynamic and structural characterization of Liposomal-Locked in-Dendrimers as drug carriers

A new Liposomal-Locked in-Dendrimer (LLD) formed by DPPC–DPPG and PAMAM 3.5 incorporating the anticancer drug DOX was studied by means of spectroscopic and DSC investigations. Multilamellar Lipid Bilayers were also considered for the sake of comparison. The results were in line with a picture of phase separation between DPPC–DPPG lipids and dendrimer that promotes the stability of the liposome membrane and the cooperativity of the relevant gel-to-liquid-crystal transition, which is enhanced in the presence of the dendrimer and the drug. As a result, the inner core of the liposome contained large amounts of dendrimer–DOX complex and was protected by a very stable membrane. This view was given a more general validation through investigations performed with other types of dendrimers, namely PG1 and PG2. The thermodynamic interpretation of the DSC data allowed a better understanding of the physico-chemical factors that justify this behaviour that makes these LLDs very promising as a new class of Modulatory Liposomal Controlled Release System (MLCRS) that could lead to drug formulations with higher safety and efficacy profiles.

A DSC investigation on the changes in pore structure of skin during leather processing

Leather processing involves many unit operations that modify the physical, chemical and biological properties of the raw skin/hide of an animal. One such major variation is brought to pore structure and size, which determines the breathing property of skin. Understanding this property is essential to improve the end use of the leather matrix. Thermoporometric technique has been used in this study to bring out the influence of various process steps on the pore size distribution of skin. Marked changes in the depression of freezing point are observed for each process. Scanning electron microscopy study reveals the morphological changes in the grain and cross-section of the skin during leather processing. Understanding and predictions of pore structure changes at various stages of leather processing would benefit: (a) in process control, (b) analysis of cost benefit ratio and (c) strategic planning and transport. Thus, this study aids in better understanding of the pore structure of skin to improve the functional properties of the leather.

DSC and Microstructural Investigations of the Elektron 21 Magnesium Alloy

The paper presents the results of DSC and microstructural investigations of Elektron 21 magnesium alloy in as cast condition and after solution hardening. Elektron 21 is a magnesium based casting alloy containing neodymium and gadolinium for used to at 200°C in aerospace application. The solution heat treatment was performed at 520°C/8h/water. Ageing treatment was performed at different temperatures 200, 250, 300 and 350°C, then quenched in air. The microstructure of Elektron 21 in as cast condition consists of primary solid solution α -Mg grains with eutectic α-Mg + Mg3(Nd,Gd) phase and regular precipitates of MgGd3 phase. After DSC investigations three exothermal signals has been observed. First exothermal signal at ~170÷245°C assigned to an undifferentiated formation of the metastable phases β” and β’ and the second one at ~280°C corresponded to the formation of a stable β (Mg3Nd) phase. The last signal at ~300°C was connected to the formation of Mg41Nd5 phase. Regular precipitates of MgGd3 phase have been also observed. TEM investigation confirmed that the Elektron 21 alloy precipitate from the solid solution according to the sequence of the following phases: α–Mgβ”β’β(Mg3Nd)Mg41Nd5

Novel biodegradable form stable phase change materials: Blends of poly(ethylene oxide) and gelatinized potato starch

AbstractNovel biodegradable form stable phase change materials were obtained in a process involving potato starch gelatinization in water/poly(ethylene oxide) (PEO) solution. DSC and microscopic investigations revealed that the presence of the starch considerably changes PEO phase transition behavior–in the blends solid–solid phase transition for PEO/starch 1 : 3 and 1 : 1 w/w has been observed; for PEO/starch blend 3 : 1 w/w solid–solid phase transition with a partial melting of PEO unbounded through hydrogen bonds with starch has been detected. The heat of phase transition depends on the strength of hydrogen bonds between PEO and starch. The intermolecular interactions were evidenced by FTIR analysis, which showed considerably shift of the stretching vibration bands of both the OH group (proton‐donor group) from starch and PEO. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

DSC and spectroscopic investigation of human serum albumin adsorbed onto silica nanoparticles functionalized by amino groups

Human serum albumin (HSA) adsorbed onto silica nanoparticles modified by 3-aminopropyltriethoxysilane (APTES) and polyethyleneimine (PEI) was investigated by differential scanning calorimetry, IR spectroscopy, and photon correlation spectroscopy. The structural alterations of the protein molecules induced from adsorption process were estimated on the basis of temperatures of denaturation transition (T d) of the protein in free (native) and adsorbed form. It was found that adsorption of the protein onto the APTES-modified silica nanoparticles results in an increase in the temperature of denaturation transition from 42 to 47.4 °C. HSA adsorbed onto the PEI-modified silica nanoparticles unfolds extensively.

Micro-XRD and temperature-modulated DSC investigation of nickel–titanium rotary endodontic instruments

Objectives Employ Micro-X-ray diffraction and temperature-modulated differential scanning calorimetry to investigate microstructural phases, phase transformations, and effects of heat treatment for rotary nickel–titanium instruments. Methods Representative as-received and clinically used ProFile GT and ProTaper instruments were principally studied. Micro-XRD analyses (Cu Kα X-rays) were performed at 25 °C on areas of approximately 50 μm diameter near the tip and up to 9 mm from the tip. TMDSC analyses were performed from −80 to 100 °C and back to −80 °C on segments cut from instruments, using a linear heating and cooling rate of 2 °C/min, sinusoidal oscillation of 0.318 °C, and period of 60 s. Instruments were also heat treated 15 min in a nitrogen atmosphere at 400, 500, 600 and 850 °C, and analyzed. Results At all Micro-XRD analysis regions the strongest peak occurred near 42°, indicating that instruments were mostly austenite, with perhaps some R-phase and martensite. Tip and adjacent regions had smallest peak intensities, indicative of greater work hardening, and the intensity at other sites depended on the instrument. TMDSC heating and cooling curves had single peaks for transformations between martensite and austenite. Austenite-finish ( A f) temperatures and enthalpy changes were similar for as-received and used instruments. Heat treatments at 400, 500 and 600 °C raised the A f temperature to 45–50 °C, and heat treatment at 850 °C caused drastic changes in transformation behavior. Significance Micro-XRD provides novel information about NiTi phases at different positions on instruments. TMDSC indicates that heat treatment might yield instruments with substantial martensite and improved clinical performance.

Bis(glycine) lithium nitrate – A new non-centrosymmetric crystal: X-ray structure, vibrational spectra and DSC investigations

A new complex of glycine with lithium nitrate in the molecular ratio 2:1 (bis(glycine) lithium nitrate; abbreviated as BGLiN) was obtained. Its crystal belongs to the Pca2 1 space group of the orthorhombic system; Z = 4. The lattice parameters are as follows: a = 10.224(12), b = 5.0343(6) and c = 17.051(2) Å. The structure is built up of the layers being parallel to the ab crystallographic plane. The lithium cations are surrounded by four oxygen atoms deriving from the glycine zwitterions. The structure and vibrational spectra (IR and Raman) of the title crystal are discussed with respect to one other and to those of glycine lithium nitrate (GLiN) and glycine sodium nitrate (GNaN) crystals. The DSC investigations do not show any low temperature phase transition (till ca. 110 K) neither for the BGLiN nor the GLiN crystals. At high temperatures the discontinuous weak phase transition followed by the melting is observed for both these complexes.