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1.
Ana-Maria Pan?Vasile Gherman Paula Sfîrloag?Geza Bandur Liliana-Marinela ?tefanMarcel Popa Lucian-Mircea Rusnac 《Polymer Testing》2012,31(3):384-392
This paper presents the thermal stability and biodegradability testing of new glycopolymers obtained by copolymerization of a novel D-mannose based oligomer with 2-hydroxypropyl acrylate and 2-hydroxypropyl methacrylate. The thermal analysis of these glycopolymers was investigated by thermogravimetry and the glass transition temperature was determined by DSC. While the acrylate derived glycopolymer has values of the glass transition temperature below 0 °C, the methacrylate derivative has positive values, above 50 °C. The biodegradation studies of the glycopolymers were carried out in a liquid medium, using pure cultures of two microorganisms, Zymomonasmobilis and Trichodermareesei. The weight losses of the new plastic materials were significant (almost 40%) and the best results were assessed for the 2-hydroxypropyl acrylate glycopolymer in the presence of both Z. mobilis and T. reesei. Microscopy showed that both microorganisms were present on the surface of the new glycopolymers and developed small colonies while modifying their surface. The changes inside the morphology of the polymeric materials structure were drastic and were studied via SEM analysis. 相似文献
2.
To investigate the nm-size dependence of structural and thermal properties for AgI, the formation of composites between AgI
and porous silica with controlled pore diameters of 10, 15, 30, and 50 nm was examined. The introduction of AgI within the
micropores of the porous silica was performed successfully by a salt-bridge precipitation method with using AgNO3 and KI aqueous solutions. The AgI formed within the micropores was identified to be β/γ-AgI, independent of the pore size
of 10-50 nm, by powder X-ray diffractometry. In differential scanning calorimetry, the composites showed thermal anomaly at
around 150°C on heating due to the phase transition from β/γ -AgI to α -AgI as in the case of bulk crystalline AgI (T
trs=147°C). However, the transition temperature from α-AgI to β/γ -AgI on cooling decreased remarkably with the decrease of the
pore size from 50 to 10 nm. The result indicates the possibility for AgI particles with diameter less than 10 nm to exist
as α -AgI even below 100°C.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
Y. Hadef J. Kaloustian A. Nicolay H. Portugal 《Journal of Thermal Analysis and Calorimetry》2008,93(2):553-560
The Medical Commission of the International Olympic Committee forbids the use of anabolic androgenic steroids, β-agonists,
stimulant and narcotic compounds to improve athletic performance. In this work, we evaluated the thermal stability of 17 compounds
by the use of the DSC for their potential GC-MS analysis either under free form or under TMS derivative form. In DSC, esterified
and unesterified anabolic steroids were characterized by a true melting peak, followed by a large exothermic peak at about
251–316°C due to oxidative degradation. They could be analysed by GC-MS mainly under TMS derivatives. Hydroxylated and unhydroxylated
stimulant compounds (xanthines) seemed to be more stable at high temperature. As unhydroxylated xanthines were not silylated
with BSTFA - TMCS, their GC analysis would be done under their free forms. TMS derivatisation of albuterol hemisulfate and
codeine phosphate is preferable. In our conditions, to analyse by GC-MS all 17 doping compounds in the same GC-MS run, the
optimal silylation temperature and best column initial temperature were determined at both 60°C. 相似文献
4.
R. Pena A. Chauvet J. Masse J. P. Ribet J. L. Maurel 《Journal of Thermal Analysis and Calorimetry》1998,53(1):71-85
The physicochemical characterization of the solid-state enantiomers and racemate of efaroxan hydrochloride (C13H17N2O+Cl-,
M=252.5 g mol-1) was performed by thermoanalytical methods (differential scanning calorimetry, thermogravimetry and thermomicroscopy)
and spectral methods (infrared spectrometry and X-ray diffractometry).
The efaroxan enantiomers and racemate were shown to be unstable near the melting point. At the beginning of the decomposition,
a loss of hydrogen chloride was observed. However when sealed pans were used, the compounds decomposed at higher temperature,
allowing a precise evaluation of the melting enthalpies by means of differential scanning calorimetry. The nature of the racemate
and its thermal stability were assessed by evaluating its free formation enthalpy. An enantiotropic solid-solid transformation
(II→I) was noted for the racemate; the reverse process (I→II) follows zero-order kinetics.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
The aim of this study was to evaluate the drug-polymer interaction in polymeric microsphere formulations containing diltiazem hydrochloride (DH). The microspheres were successfully prepared by solvent evaporation technique using two different polymer types, Eudragit®RS 100 and ethylcellulose. The existence of a possible interaction between DH and the polymers was investigated by using DSC and XRD. The DSC curves and XRD patterns indicated that there was no interaction between DH and the polymers. The peak area calculations in the DSC curves of F1- and F2-coded microsphere formulations showed that DH was dispersed, not dissolved, in the ethylcellulose polymer matrix, while it partly dissolved in the Eudragit®RS 100 polymer matrix. 相似文献
6.
K. Mészáros Szécsényi M. Arnold K. Tomor F. F. Gaál 《Journal of Thermal Analysis and Calorimetry》1995,44(2):419-430
The thermal behavior of different fly ashes from the electrical precipitators of various pulverized carbon fuel-fired boilers was investigated by means of simultaneous TG, DTG, DTA and EGA analysis. The carbon and sulfur contents of the samples were determined by gastitrimetry. The compositions of the samples were examined by X-ray diffraction. The quantitative oxide analysis of the ashes was carried out by means of a classical method. 相似文献
7.
Barbara Marciniec M. Stawny Magdalena Hofman M. Naskrent 《Journal of Thermal Analysis and Calorimetry》2008,93(3):733-737
The study has been undertaken to check the effect of ionising radiation on the physical and chemical properties of florfenicol,
an antibiotic of a wide range of antibacterial activity. The solid-state samples were subjected to an electron beam generated
by accelerator corresponding to the doses of 25, 100 and 400 kGy, and the effect of the exposure was analysed by the methods
not requiring changes in the state (with no preliminary treatment), such as SEM, DSC, FTIR, XRD, EPR and HPLC.
Florfenicol irradiated with a dose of 25 kGy has not changed the form or colour, however, a small increase in intensity of
some absorption bands in the FTIR spectrum and of some peaks in the XRD pattern, a decrease in the melting point by 0.6°C,
the appearance of free radicals and a loss in the FF content within the error of the method (0.91%) have been observed. After
irradiation with greater doses (100 and 400 kGy) the changes have intensified, yellow discolouration appeared and the loss
of FF content has increased to 6.39%. As follows from the results, the compound studied in solid-state undergoes radiolysis
after e-beam irradiation in the doses ≥25 kGy, but lower doses (15–20 kGy) can be applied for its decontamination or sterilization
with no adverse effect on its physico-chemical properties. 相似文献
8.
Riko Ozao Hiroshi Ogura Moyuru Ochiai Sadao Tsutsumi 《Journal of Thermal Analysis and Calorimetry》1997,49(2):961-970
How a DSC result is influenced by the particle size distribution of a powder sample is shown, and a simple and optimal method to be included in a routine DSC analysis (e.g., purity determination) to improve the reliability of the analysis is proposed. In case of-Al2O3 powder, most reliable heat capacity data can be obtained by preparing a powder with a self-similar particle size distribution with a distribution constant of 0.7, and by compressing it under a pressure of 1.5 MPa for a duration of 5 min or longer.This work is partially supported by the Research Fund of North Shore College of SONY Institute. R.O. wishes to express her gratitude to the support. 相似文献
9.
M. Sh. Lvova E. I. Kozlov I. A. Wishnevezkaya 《Journal of Thermal Analysis and Calorimetry》1993,40(2):405-411
DSC was used together with other methods of pharmaceutical analysis (spectrophotometry, thin-layer chromatography) to estimate the quality and standardization of two drugs—lipoic acid (polymerization upon melting, purity) and progesterone (melting temperature, polymorphism). 相似文献
10.
Katarzyna Michalik Zofia Drzazga Anna Michnik M. Kaszuba 《Journal of Thermal Analysis and Calorimetry》2007,88(2):401-404
A thermal
and kinetic analysis of two protease inhibitors: nelfinavir mesylate and atazanavir
sulfate, were carried out to find their thermal stability. DSC curves of both
drugs showed exothermic transition. This observed process resulted in two
steps. Obtained apparent activation energy pointed at low stability of studied
protease inhibitors in water solutions. 相似文献
11.
Thermal analysis of black powder 总被引:5,自引:0,他引:5
Turcotte R. Fouchard R. C. Turcotte A.-M. Jones D. E. G. 《Journal of Thermal Analysis and Calorimetry》2003,73(1):105-118
While there is abundant literature describing the factors affecting the performance and the mechanical sensitivity of black
powder, only a few papers are devoted to its thermal properties. Previous work indicated that no exothermic reactions were
observed below 300°C in an inert gas environment. In the present work a variety of thermal techniques (DSC, TG, simultaneous
TG-DTA-FTIR-MS, ARC, HFC) has been used to study the thermal decomposition of black powder. Exothermic reactions were observed
at temperatures as low as 230 and 140°C in inert and oxidizing atmospheres, respectively. The latter exothermic reaction is
due to sulfur oxidation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
Thermal analysis of the rice and by-products 总被引:2,自引:0,他引:2
J. A. Amorim S. A. Eliziário D. S. Gouveia A. S. M. Simőes J. C. O. Santos M. M. Conceiçăo A. G. Souza M. F. S. Trindade 《Journal of Thermal Analysis and Calorimetry》2004,75(2):393-399
The thermogravimetry (TG) is a technique used in the quality control of foods. In this work the moisture and ash contents
in the rice and by-products (bran and husk), the thermal stability and the gelatinization process by conventional, thermogravimetric
and calorimetric methods were studied. The moisture and ash contents obtained by TG and conventional methods did not present
significant differences. The rice presented higher starch content, while the bran presented higher protein content. The thermogravimetric
data presented the following thermal stability order: rice>bran>husk. The calorimetric curves indicated the gelatinization
of the starch. The kinetic parameters were compatible.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
J. D. Menczel M. Jaffe C. K. Saw T. P. Bruno 《Journal of Thermal Analysis and Calorimetry》1996,46(3-4):753-771
Poly(2-methylpentamethylene terephthalamide) (Nylon M5T) is a new high temperature aromatic polyamide developed by Hoechst Celanese. In this paper thermal properties of Nylon M5T chips, as well as as-spun and drawn fibers were studied by DSC, DMA, hot stage microscopy and WAXS.T
g of the fully amorphous Nylon M5T is 143°C when measured by DSC;T
g increases with crystallinity to 151°C. The temperature dependence of the solid and melt specific heat capacities has also been determined. The heat capacity increase at the glass transition of the amorphous polymer is 103.9 J °C–1 mol–1.T
g by DMA for the as-spun fiber is 155°C, for a drawn fiber is 180°C. Three secondary transitions were observed by DMA in addition to the glass transition. These correspond to a local mode relaxation of the methylene groups at –120°C, onset of rotation of the amide-groups at –65°C and the onset of the rotation of the phenylenegroups (at 63°C). The crystallinity of Nylon M5T strongly depends on the rate of cooling from the melt. The isothermal crystallization data are melt temperature dependent: two-dimensional crystallization takes place when the samples are crystallized from higher melt temperatures, and this phase changes into a spherulitic structure during cooling to room temperature. Spherulitic crystallization occurs when lower melt temperatures are used. This polymer has three crystal forms as indicated by DSC, DMA and WAXS data. The crystal to crystal transitions are clearly visible when amorphous samples are heated in the DSC, or the DMA curves of as-spun fibers are recorded. It is experimentally shown that a considerable melting of the lower temperature crystal forms takes place during the crystal to crystal transitions. The equilibrium melting point as measured by the Hoffman-Weeks method, has been determined to be 339°C.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthday 相似文献
14.
K. H. Ip B. H. Stuart P. S. Thomas A. S. Ray 《Journal of Thermal Analysis and Calorimetry》2008,92(1):97-100
Thermal analysis has been employed in a study of the degradation of heritage Sydney sandstone used in St Mary’s Cathedral
in Sydney, Australia. TG and DSC have been used to characterise the clay components removed from weathered and unweathered
sandstone. Two types of kaolin clays — kaolinite and its polymorph, dickite — have been identified. A higher amount of dickite
present in the clay of weathered sandstone indicates that a kaolinite-to-dickite transformation occurs upon weathering. XRD
hot stage analysis was also used to demonstrate the presence of a more thermally stable polymorph of the kaolinite. 相似文献
15.
Recognition of active ingredients in tablets by chemometric processing of X-ray diffractometric data
The paper presents an approach to use Partial Least Squares Discriminant Analysis (PLS-DA) on X-ray powder diffractometry (XRPD) dataset to build a model which recognizes a presence (or absence) of particular drug substance (acetaminophen) in unknown mixture (OTC tablet). The dataset consisted of 33 XRPD signals, measured for 12 pure substances and 21 tablets containing them in different quantitative and qualitative ratios, along with unknown excipients. The model was built with an external validation dataset chosen by Kennard-Stone algorithm. The RMSECV value was equal to 0.3461 (87.8% of explained variance) and external predictive error (RMSEP) was equal to 0.3123 (86.2% of explained variance). The result suggests that small but properly prepared training datasets give ability to construct well-working discriminant models on XRPD signals. 相似文献
16.
Varga M. Mulas G. Cocco G. Molnár Á. 《Journal of Thermal Analysis and Calorimetry》1999,56(1):305-310
Amorphous PdZr, PdCuZr and PdCuSi alloy ribbons and powders are characterized by DSC, XRD and XPS in the as-received state
and after treatments with oxygen, hydrogen or dilute hydrogen fluoride solution. Zr-containing alloys are shown to undergo
substantial structural changes resulting in palladium enrichment on their surface, whereas no apparent changes in the bulk
structure are found for PdCuSi. Catalytic activity and selectivity of the pretreated samples were tested in the hydrogenation
of phenylacetylene.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
《Arabian Journal of Chemistry》2014,7(2):189-195
The aim of this paper was to describe the temperature effect on the stability and the thermophysical properties of azithromycin (AZ). First, the density, the heat capacity and the solubility of original (commercial) AZ were determined. Second, the original samples were heated at 50 °C and 80 °C and their PLM, DSC, TGA and XRD data were compared to those of the original AZ. According to our results, the original AZ was a dihydrate which converted to anhydrate when heated up to 80 °C. The dehydration induced a change of crystal habit while the crystalline lattice remained unchanged. 相似文献
18.
The potential of near infrared (NIR) spectroscopy for the characterization of polymorphs in the active principle of a commercial formulation prior to and after the manufacturing process was assessed. Polymorphism in active principles is extremely significant to the pharmaceutical industry. Polymorphic changes during the production of commercial pharmaceutical formulations can alter some properties of the resulting end-products. Multivariate curve resolution-alternating least squares (MCR-ALS) methodology was used to obtain the “pure” NIR spectrum for the active principle without the need to pretreat samples. This methodology exposed the polymorphic transformation of Dexketoprofen Trometamol (DKP) in both laboratory and production samples obtained by wet granulation. No polymorphic transformation, however, was observed in samples obtained by direct compaction. These results were confirmed using by X-ray powder diffractometry (XRD) and differential scanning calorimetry (DSC) measurements. Pure crystalline polymorphs of DKP were available in the laboratory but amorphous form was not, nevertheless the developed methodology allows the identification of amorphous and crystal forms in spite of the lack of pure DKP. 相似文献
19.
Marciniec B. Kozak M. Wachowski L. Ogrodowczyk M. 《Journal of Thermal Analysis and Calorimetry》2003,73(2):473-485
The effect of ionising radiation (15-100 kGy) on the physico-chemical properties of 6 steroid derivatives in solid state (Hydrocortisone,
Hydrocortisone acetate, Prednisolone, Prednisolone acetate, Dexamethasone and Fludrocortisone acetate) was studied by differential
scanning calorimetry (DSC), differential thermal analysis (DTA), scanning electron microscopy (SEM), UV spectrophotometry,
high-performance liquid chromatography (HPLC), X-ray powder diffraction and polarimetry. DSC and DTA results revealed that
the irradiated compounds undergo phase transitions at lower temperatures, show lower melting points and lower enthalpy of
the melting process their non-irradiated analogues. The results of HPLC measurements proved a loss in the active substance
content after irradiation ranging from 0.5 to 2.88%. No significant effect of irradiation was detected by the UV spectrophotometry
or polarimetry in the course of the UV spectrum, absorbancy or optical rotation, as well as in the SEM photographs and X-ray
patterns. For some compounds studied a correlation was found between the irradiation dose and the shifts in DSC curves and
the loss of content determined by the HPLC method. Similar, but not so much pronounced relations were established in or earlier
studies of the derivatives of nitroimidazole and 1,4-dihydropyridine. In general the results have shown relatively high radiochemical
stability of the compounds studied and have proved that the DSC method is a sensitive detector of irradiation-caused changes
in drugs in solid phase.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
For many applications poly(styrene) must
be treated to reduce its flammability. This is usually done by incorporating
a flame retardant additive, usually an organohalogen compound, into the formulation
as the polymer is being processed. A potentially very efficient way of introducing
flame retardance would be to incorporate a suitable structural unit directly
into the polymer. This can be done by using 2,4,4,5,5-pentaphenyl-1,3,2-dioxaphospholane
as an initiator for styrene polymerization. The strained carbon–carbon
bond of the phospholane undergoes homolysis at moderate temperatures to generate
a diradical which initiates polymerization. The resulting polymer contains
an O–P–O unit in the mainchain. Thermogravimetry indicates that
the thermal stability of the polymer is quite comparable to that of poly(styrene)
generated by conventional methods. 相似文献