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1.
Chemical recycling of polyamide waste in water was studied using 0.5 L high pressure autoclave at temperatures of 150, 200,
210, 220,230 and 240 °C and at various pressures of 100, 200, 300, 400, 500, 600 and 700 psi (pound per square inch). Viscosity
average molecular weight of the polyamide waste sample was determined by Ostwald method and recorded as 1.928 × 103. The reaction was found to be first order with velocity constant in order of 10−2 min−1. The velocity constant and percent conversion of depolymerization reaction at 240 °C and 700 psi pressure were recorded as
2.936 × 10−2 min−1 and 99.99% respectively. The velocity constant was obtained on the basis of measurement of amine value. Kinetic and thermodynamic
parameters such as energy of activation, frequency factor, enthalpy of activation were found to be 10.6 kJ mole−1, 0.3719 min−1 and 6.3 kJ mole−1 respectively, at the optimum conditions for maximum depolymerization of polyamide waste. 相似文献
2.
Hydrolytic depolymerization of polyamide waste in water was studied using 0.5 L high pressure autoclave at temperatures of
235, 240, 245, 250 °C and at autogenious pressure 480, 500, 520, and 600 psi (pound per square inch).The reaction rate constant,
energy of activation, enthalpy of activation, entropy of activation and equilibrium constant were calculated from the experimental
data obtained. The maximum depolymerization (59.2%) of polyamide waste into monomer caprolactum was obtained at 250 °C and
600 psi pressure. The reaction rate constant was obtained on basis of measurement of amine value and residual weight. The
depolymerization reaction was found to be pseudo first order with reaction rate constant of the order of 10−3 min−1. The enthalpy, entropy and free energy of activation were recorded as 85.75, −0.1354 and 156.59 kJ mol−1 respectively at the experimental conditions for maximum depolymerization of polyamide waste. The thermodynamic equilibrium
constant for this hydrolysis reaction was found to be 2.3 × 10−16. 相似文献
3.
4.
Solidification of sewage sludge has been actively investigated in Japan and Europe since the 1970s. Most previous studies
have focused on only the mechanical aspects of potential alternative cover soil made using sewage. Most solidification processes,
however, suffer from severe odor problems because of the high alkalinity of the material. The objectives of this study are
to develop a cost-effective solidifying agent for conversion of sewage sludge in order to reduce the odor generation, as an
alternative to the conventional cement lime-based solidifying agent, and to demonstrate its applicability in the field experimentally.
Field test results showed compressive strength well above the 1.0 kg/cm2 criterion for landfill cover soil in Korea. Also, the permeability coefficient was far below the 5 × 10−5 cm/s design criterion for landfill cover soil. Even in harsh weather conditions, such as in winter and summer, the compressive
strength was increased. In addition, the permeability was decreased from 3.45 × 10−6 cm/s to 4.78 × 10−7 cm/s, and from 2.27 × 10−6 cm/s to 3.62 × 10−7 cm/s, at 7 days after placement in January and August, respectively. It can therefore be postulated that the proposed solidification
process is an appropriate alternative for production of daily landfill cover material. Concerning the odor problem, 5 min
of mixing of sewage with TS103, one of the proprietary agents used in this work, was sufficient to suppress the concentration
of ammonia emitted to below 10 ppm. Considering all of these experimental field test results, it is expected that the proposed
method could be a competitive approach for manufacture of alternative landfill cover material. 相似文献
5.
A. L. S. Schneider D. D. Silva M. C. F. Garcia V. H. Grigull L. P. Mazur S. A. Furlan G. F. Arag?o A. P. T. Pezzin 《Journal of Polymers and the Environment》2010,18(3):401-406
The environmental impact caused by the disposal of plastics has motivated the development of biodegradable materials. Recent
studies showed that supplementation with oleic acid (OA) in cultures producing poly(3-hydroxybutyrate), P(3HB), increased
the polymer productivity. However only few studies have shown the properties and biodegradation profile of the polymer obtained.
This research investigated the influence of OA concentration on the biodegradation of the P(3HB) obtained from cultures of
Cupriavidus necator. The crystallinity of the casting films determined by differential scanning calorimetry (DSC) was reduced from 70% (0 g L−1 of OA) to 52% (3.0 g L−1 of OA). A reduction of 11 °C in the melting temperature was observed with 3.0 g L−1 of OA. The kinetic of biodegradation was: 3.0 > 1.5 > 0.9 > 0.3 > 0 g L−1 of OA. 相似文献
6.
Shin-ichi Sakai Yasuhiro Hirai Hirofumi Aizawa Shizuko Ota Yasuhiro Muroishi 《Journal of Material Cycles and Waste Management》2006,8(1):56-62
Atmospheric emissions of deca-brominated diphenyl ether (DBDE) in Japan were estimated based on the material flow of DBDE
products and their emission factors. In 2002, the demand for DBDE in Japan was 2200 ton/year and the stock level was about
60 000 ton. The DBDE flow into the waste stream was estimated to be about 6000 ton/year and the flow out through second-hand
product exports was more than 700 ton/year. Home appliance recycling facilities dismantle and crush domestic wastes containing
about 600 ton of DBDE annually. Material recycling of crushed plastics is not commonly practiced as yet. Emission factors
from plastics processing (2 × 10−9–1 × 10−7), textile processing (9 × 10−7), home appliance recycling (8 × 10−9–5 × 10−6), and waste incineration (1 × 10−7–2 × 10−6) were estimated using field measurement data. The DBDE emission rate through house dust during the service life of final
products (2 × 10−7–9 × 10−7 per year) was estimated using the DBDE concentration in dust and the amount of dust in used televisions. Emission factors
from previous studies were also used. The estimated total DBDE emission was 170–1800 kg/year. These results suggest the necessity
of characterizing emissions during the service life of products, which is essential information for formulating an appropriate
e-waste recycling strategy. 相似文献
7.
Mohammad Taghi Taghizadeh Reza Abdollahi Naser Sadeghpour Orang 《Journal of Polymers and the Environment》2012,20(1):208-216
The degradation of chitosan by means of ultrasound irradiation and its combination with homogeneous photocatalysis (photo-Fenton)
was investigated. Emphasis was given on the effect of additive on degradation rate constants. 24 kHz of ultrasound irradiation
was provided by a sonicator, while an ultraviolet source of 16 W was used for UV irradiation. To increase the efficiency of
degradation process, degradation system was combined with Fe(III) (2.5 × 10−4mol/L) and H2O2 (0.020–0.118 mol/L) in the presence of UV irradiation and the rate of degradation process change from 1.873 × 10−9−6.083 × 10−9 mol1.7 L s−1. Photo-Fenton process led to complete chitosan degradation in 60 min with the rate increasing with increasing catalyst loading.
Sonophotocatalysis in the presence of Fe(III)/H2O2 was always faster than the respective individual processes. A synergistic effect between ultrasound and ultraviolet irradiation
in the presence of Fenton reagent was calculated. The degraded chitosans were characterized by X-ray diffraction (XRD), gel
permeation chromatography (GPC) and Fourier transform infrared (FT-IR) spectroscopy and average molecular weight of ultrasonicated
chitosan was determined by measurements of intrinsic viscosity of samples. The results show that the total degree of deacetylation
(DD) of chitosan change, partially after degradation and the decrease of molecular weight led to transformation of crystal
structure. A negative order for the dependence of the reaction rate on total molar concentration of chitosan solution within
the degradation process was suggested. Results of this study indicate that the presence of catalyst in the reaction medium
can be utilized to reduce molecular weight of chitosan while maintaining the power of irradiated ultrasound and degree of
deacetylation. 相似文献
8.
M. A. Diab A. Z. El-Sonbati D. M. D. Bader M. Sh. Zoromba 《Journal of Polymers and the Environment》2012,20(1):29-36
N-(Methylphenylmethylidenyl) chitosan (MPMC) polymer was synthesized by chemical modification of chitosan. The chemical structure
of the modified polymer was characterized by IR, 1H NMR and elemental analysis. Thermogravimetric reveals that the thermal stability of chitosan polymer is greater than MPMC
polymer. The activation energies of thermal degradation of chitosan and MPMC polymers determined using Arrhenius relationship.
Thermal degradation of MPMC polymer was studied and the products of degradation were identified by GC–MS technique. It seems
that the mechanism of degradation of MPMC polymer is characterized by elimination of low-molecular weight radicals. Combination
or recombination of H· or OH− with these radicals and random scission mechanism along the backbone chain are the main source of the degradation products. 相似文献
9.
Christopher Thellen Megan Coyne Danielle Froio Margaret Auerbach Carl Wirsen Jo Ann Ratto 《Journal of Polymers and the Environment》2008,16(1):1-11
A series of polyhydroxyalkanoates (PHA), all containing 1% nucleating agent but varying in structure, were melt-processed
into films through single screw extrusion techniques. This series consisted of three polyhydroxybutyrate (PHB) and three polyhydroxybutyrate-valerate
(PHBV) resins with varying valerate content. Processing parameters of temperature in the barrel (165–173 °C) and chill rolls
(60 °C) were optimized to obtain cast films. The gel-permeation chromatography (GPC) results showed a loss of 8–19% of the
polymer’s initial molecular weight due to extrusion processing. Modulated differential scanning calorimetry (MDSC) displayed
glass transition temperatures of the films ranging from −4.6 to 6.7 °C depending on the amount of crystallinity in the film.
DSC data were also used to calculate the percent crystallinity of each sample and slightly higher crystallinity was observed
in the PHBV series of samples. X-ray diffraction patterns did not vary significantly for any of the samples and crystallinity
was confirmed with X-ray data. Dynamic mechanical analysis (DMA) verified the glass transition trends for the films from DSC
while loss modulus (E′) reported at 20 °C showed that the PHBV (3,950–3,600 MPa) had the higher E′ values than the PHB (3,500–2,698 MPa) samples. The Young’s modulus values of the PHB and PHBV samples ranged from 700 to
900 MPa and 900 to 1,500 MPa, respectively. Polarized light microscopy images revealed gel particles in the films processed
through single-screw extrusion, which may have caused diminished Young’s modulus and tensile strength of these films. The
PHBV film samples exhibited the greatest barrier properties to oxygen and water vapor when compared to the PHB film samples.
The average oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) for the PHBV samples was 247 (cc-mil/m2-day) and 118 (g-mil/m2-day), respectively; while the average OTR and WVTR for the PHB samples was 350 (cc-mil/m2-day) and 178 (g-mil/m2-day), respectively. Biodegradation data of the films in the marine environment demonstrated that all PHA film samples achieved
a minimum of 70% mineralization in 40 days when run in accordance with ASTM 6691. For static and dynamic incubation experiments
in seawater, microbial action resulting in weight loss as a function of time showed all samples to be highly biodegradable
and correlated with the ASTM 6691 biodegradation data. 相似文献
10.
Ivan S. Ristić Ljiljana Tanasić Ljubiša B. Nikolić Suzana M. Cakić Olivera Z. Ilić Radmila Ž. Radičević Jaroslava K. Budinski-Simendić 《Journal of Polymers and the Environment》2011,19(2):419-430
Different synthesis methods were applied to determine optimal conditions for polymerization of (3S)-cis-3,6-dimethyl-1,4-dioxane-2,5-dione (l-lactide), in order to obtain poly(l-lactide) (PLLA). Bulk polymerizations (in vacuum sealed vessel, high pressure reactor and in microwave field) were performed
with tin(II) 2-ethylhexanoate as the initiator. Synthesis in the vacuum sealed vessel was carried out at the temperature of
150 °C. To reduce the reaction time second polymerization process was carried out in the high pressure reactor at 100 °C and
at the pressure of 138 kPa. The third type of rapid synthesis was done in the microwave reactor at 100 °C, using frequency
of 2.45 GHz and power of 150 W at the temperature of 100 °C. The temperature in this method was controlled via infrared system
for in-bulk measuring. The solution polymerization (with trifluoromethanesulfonic acid as initiator) was possible even at
the temperature of 40 °C, yielding PLLA with narrow molecular weight distribution in a very short period of time (less than
6 h). The obtained polymers had the number-average molecular weights ranging from 43,000 to 178,000 g mol−1 (polydispersity index ranging from 1 to 3) according to the gel permeation chromatography measurements. The polymer structure
was characterized by Fourier transform infrared and NMR spectroscopy. Thermal properties of the obtained polymers were investigated
using thermogravimetry and differential scanning calorimetry. 相似文献
11.
Rajendram Thivyatharsan H. A. Y. R. Gunarathna Benedict Francis Antony Basnayake Periyathamby Kuruparan 《Journal of Material Cycles and Waste Management》2012,14(1):27-37
The objective of the study was to develop a low cost and environmentally friendly liner system for a landfill bioreactor to
harness energy from waste. The landfill bioreactor test cell was constructed and evaluated for performance under dry tropical
conditions of Sri Lanka. The research was carried out from March 2009 to September 2010. The clay-waste polyethylene-clay
composite liner system was developed and permeability was tested. The permeability values of the liner under both saturated
and unsaturated conditions at the high estimated hydraulic head of 86.2 cm were in between 6.3 × 10−8 and 2.6 × 10−8 cm/s. The permeability of the liner under waste filled condition varied between 2.17 × 10−9 and 8.15 × 10−9 cm/s, which satisfies the standard permeability value. Thus, the results were below the minimum requirement at very high
estimated leachate head. After loading the test cell, leachate and permeate characteristics were analyzed for 273 days, from
January 2010 to September 2010. The study showed the relationships among various parameters including pH, electrical permeability,
chemical oxygen demand, biological oxygen demand, ammonia, nitrate, phosphate, total solids, volatile solids, total suspended
solids and volatile suspended solids. The results of the analysis indicated that there are significant differences in the
values of leachate and permeate parameters. The permeate parameters had values very much lower than those of leachate. It
reveals that the clay-waste polyethylene-clay composite liner system reduced the concentration of these parameters when the
leachate passed through the liner. The biofilm formed in waste polyethylene within the liner may have degraded most of organic
materials found in the leachate when it passed through the liner. Therefore, the clay-waste polyethylene-clay composite liner
system can be applied for full scale landfill bioreactors, particularly for Asian developing countries, due to better performance
and more environmentally friendly characteristics. 相似文献
12.
W. S. Chow S. G. Tan Z. Ahmad K. H. Chia N. S. Lau K. Sudesh 《Journal of Polymers and the Environment》2014,22(1):140-147
In this study, bio-thermoset from epoxidized soybean oil (ESO) was prepared in the presence of methylhexahydrophthalic anhydride curing agent and 2-ethyl-4-methylimidazole catalyst. The crosslink densities of the synthesized ESO are ranged from 0.109 × 10?3 to 0.308 × 10?3 mol/cm3. The ESO bio-thermosets were exposed to the soil-burial test for 8 months. Weight change and morphology of the degraded ESO specimens were assessed. It was found that the weight loss of ESO was governed by the materials compositions, crosslink density and the soil-burial exposure time. The 3 mm thickness ESO bio-thermosets with crosslink density of 0.109 × 10?3 mol/cm3 had fully biodegraded after soil-burial for 6 months. In addition, 16S rDNA sequencing was carried out to identify the soil microorganisms. It was suggested that Comamonas sp., Bacillus sp., Streptomyces sp. and Acinetobacter sp. are the possible soil microbes that degrade the ESO bio-thermosets in the compost soil environment. 相似文献
13.
Shahla Ataei Rosiyah Yahya Seng Neon Gan 《Journal of Polymers and the Environment》2011,19(2):540-545
The kinetic behavior of polyesterification of the alkyd resins synthesized using glycerol and phthalic anhydride modified
with oleic acid from the palm oil at temperatures between 120 and 240 °C was studied. Three alkyds having oleic acid contents
of 28, 40, and 65% were prepared by employing fatty acid method. The extent of the polyesterification reaction and average
degree of polymerization were monitored by determining the acid number of the aliquot of the reaction mixture at various intervals
of time and by measuring the volume of water evolved. Kinetic studies revealed that initial reaction rates followed a second-order
kinetics up to certain limit and thereafter deviations were observed. The extent of reaction varied from 77.4 to 86.3% before
deviation for all the three samples and exhibited a considerable degree of conversion. The second-order rate constants calculated
from the linear part were found to be of the order of 10−5 g (mg KOH)−1 min−1. Molecular weight of the alkyd samples was determined by GPC; number average molecular weight of the alkyds ranged from 980
to 2,070. 相似文献
14.
Water transport in polylactic acid (PLA), PLA/ polycaprolactone copolymers, and PLA/polyethylene glycol blends 总被引:1,自引:0,他引:1
Georgette L. Siparsky Kent J. Voorhees John R. Dorgan Kevin Schilling 《Journal of Polymers and the Environment》1997,5(3):125-136
Polylactic acid (PLA) is a hydrolytically degradable aliphatic polyester, and water vapor permeability may have a significant
influence on the rate of degradation. A method is devised to use bags prepared from PLA films and filled with molecular sieves
to determine the water vapor permeability in the polymer, its copolymers with caprolactone, and blends with polyethylene glycol.
The “solution-diffusion” model is used to determine the permeability parameters. These include the solubility coefficient,S, a measure of the equilibrium water concentration available for hydrolysis and the diffusion coefficient,D, which characterizes the rate of water vapor diffusion into the film under specific conditions. Values ofS andD at 50‡C and 90% relative humidity ranged from 400 × 10-6 to 1000 × 10-6 cm3 (STP)/(cm3 Pa) and 0.20 × 10-6 to 1.0 × 10-6 cm2/s, respectively. TheS andD coefficients were also measured at 20 and 40‡C and compared to those of other polymers. The degree of crystallinity was found
to have little influence on the measured permeability parameters. The heat of sorption, δHS, and the activation energy of diffusion, ED, were used to show that the permeability process is best described by the “water cluster” model for hydrophobic polymers.
Finally, the diffusion coefficient is used to compare the rate of water diffusion to the rate of water consumption by ester
hydrolysis. Results indicate that hydrolytic degradation of PLA is reaction-controlled. 相似文献
15.
Ahmed Abdel-Megeed Mourad A. M. Aboul-Soud Rudolf Mueller Fredua Agyeman Rudolf Salem S. Al-Deyab 《Journal of Polymers and the Environment》2010,18(4):617-625
A gram-negative psychrophilic bacterium, with potential for biodegradation of long-chain n-alkanes was isolated from ice samples collected in Spitzbergen, Denmark. On the basis of results of biochemical and morphological
tests and sequence analysis of 16S rRNA, the strain was identified as Pseudomonas
frederiksbergensis. In this work, a short-chain NAD+-dependent alcohol dehydrogenase (alcDH) (Accession number: AAR13804) from the P.
frederiksbergensis was cloned and transformed in E. coli BL21 (3DE) competent cells. The alcDH activity was highest in the crude extract of cells induced with 1.0 mM IPTG. The recombinant
alcDH enzyme was purified to 93.4% homogeneity using three consecutive purification steps including ammonium sulphate, Q-Sepharose
Fast Flow column and gel filtration chromatography employing Superdex 200 10/30 HR column. Enzyme enrichment and yield levels
of 31.4 folds and 25.5%, respectively, were achieved. While the subunit molecular mass of the enzyme was determined on SDS-PAGE
to be ~38 kDa, the aggregated native form of the enzyme had a molecular mass of ~238 kDa by gel filtration analysis. Reaction
conditions optima for the recombinant alcDH were determined with propan-1-ol as the substrate. While the optimum pH was 9,
the optimum temperature was 35 °C. The alcDH enzyme exhibited moderate thermal stability with half-lives of 150 min at 55 °C,
27 min at 65 °C and 8 min at 75 °C. Results for kinetic parameters indicated that the apparent K
m value for alcDH with propan-1-ol as the substrate was found to be 1.42 mM and the V
max value was 0.63 mmol mg−1 min−1. Experimental evidence revealed that the recombinant alcDH exhibited a wide range of substrate specificity, with higher levels
of specific activity for aliphatic alcohols as compared to secondary alcohols. Taken together, the present study highlights
the potential of alcDH as a member of cold-adapted enzymes in several key biotechnological applications including environmental
bioremediation and biotransformations. It is envisaged that, with the ongoing screening of microorganisms and metagenomes,
directed evolution approaches and the subsequent overexpression of recombinant proteins, more enzymes will be found that are
suitable for bioremediation purposes. 相似文献
16.
Tara Sankar Pathak Jung-Ho Yun Se-Jong Lee Dae-Jin Baek Ki-Jung Paeng 《Journal of Polymers and the Environment》2010,18(1):45-56
Alginates, extracted from algae are linear unbranched polymers containing β-(1→4)-linked d-mannuronic acid (M) and α-(1→4)-linked l-guluronic acid (G) residues. The conversion of alginic acid into the metal alginate is confirmed using FTIR spectroscopy.
Asymmetric and symmetric stretching of free carboxyl group present in metal alginate occurs almost at the same position in
various solvent compositions. Total intrusion volume of metal alginate prepared in propanol (0.0742 mL/g) is greater compared
to those in ethanol (0.0648 mL/g) and methanol (0.0393 mL/g) as solvent. Surface morphology as well as porosity and pore size
distribution of metal alginate are greatly influenced by solvent. It can be seen from thermal analysis results that calcium
alginate prepared using different solvent compositions started decomposing at 100 °C, but rapid degradation started around
200 °C. The results showed a stepwise weight loss during thermal sweep, indicating different types of reactions during degradation.
First and second step of rapid degradation was situated around 200–300 and 300–550 °C, respectively; whereas the final step
is situated around 550–650 °C. The trend of degradation was similar for all the solvents, although the amount of final residue
varied from one solvent to another. At the same time, lower thermal stability was also observed with higher heating rates.
Additionally, a kinetic analysis was performed to fit with TGA data, where the entire degradation process has been considered
as three consecutive first order reactions. 相似文献
17.
M. N. Satheesh Kumar Zahira Yaakob Siti Maimunah Siddaramaiah S. R. S. Abdullah 《Journal of Polymers and the Environment》2010,18(4):539-544
The kinetics of polyesterification of glycerol, phthalic anhydride and jatropha oil leading to the formation of alkyd resins
were studied. A series of alkyd resins having different amount of jatropha oil viz., 40–80% have been prepared by employing
two stage alcoholysis-polyesterification process. The extent of reaction and average degree of polymerisation were calculated
from the end group analysis of the reaction mixture withdrawn at regular intervals of time. The initial reaction rates followed
the second order kinetics and thereafter deviations were observed. An appreciable degree of conversion was noticed from the
extent of the reaction which lies in the range of 49.5–62.5%. The average degree of polymerisation calculated in the region
of deviation from second order suggested the occurrence of chain branching at relatively shorter intervals along the polymer
chain. The second order rate constants were found to be of the order of 10−5 g (mg KOH)−1 min−1. 相似文献
18.
Preparation, Thermal Properties and Thermal Reliability of Form-Stable Paraffin/Polypropylene Composite for Thermal Energy Storage 总被引:1,自引:0,他引:1
This study is focused on the preparation, characterization, and determination of thermal properties and thermal reliability
of paraffin/polypropylene (PP) composite as a novel form-stable phase change material (PCM) for thermal energy storage applications.
In the composite, paraffin acts as a PCM when PP is operated as supporting material. The composites prepared at different
mass fractions of paraffin (50, 60, 70, 80, and 90 w/w%) by solution casting method were subjected to leakage test by heating
the composites over the melting temperature of the PCM. The paraffin/PP composite (70/30 w/w%) is found as the maximum paraffin
containing composite and was characterized using Fourier transform infrared spectroscopy, optic microscopy, differential scanning
calorimetry (DSC), and thermal gravimetric analysis (TGA) techniques. DSC analysis indicated that the form-stable paraffin/PP
composite melts at 44.77–45.52 °C and crystallizes at 53.55–54.80 °C. It has latent heats of 136.16 and −136.59 J/g for melting
and crystallization, respectively. These thermal properties make it potential PCM for latent heat thermal energy storage (LHTES)
purposes such as solar space heating applications. Accelerated thermal cycling tests indicated that the form-stable PCM had
good thermal reliability. TGA also showed that the form-stable PCM degrades in two distinguishable steps and had good chemical
stability. 相似文献
19.
Tara Sankar Pathak Jin San Kim Se-Jong Lee Dae-Jin Baek Ki-Jung Paeng 《Journal of Polymers and the Environment》2008,16(3):198-204
Alginic acid and metal alginates are prepared from fresh algae using extraction method. A FTIR spectrum indicates that alginic
acid is converted into the metal alginate. Comparing calcium and cobalt alginates, asymmetric stretching of free carboxyl
group of calcium alginate at 1630 cm−1 is shifted to 1585 cm−1 in cobalt alginate, due to the change of charge density, radius and atomic weight of the cation, creating a new environment
around the carbonyl group. The strong exothermic peak of alginic acid in DSC thermogram indicates the decomposition of biopolymer,
whereas strong exothermic peak of metal alginate in DSC thermogram attributed to the decomposition of biopolymer and formation
of respective carbonate. Based on DSC study, the decomposition of cobalt alginate occurs at higher temperature comparing to
those of sodium and calcium alginate, which may conclude into the higher stability of cobalt alginate. TGA results reveal
that, cobalt alginate is more stable than calcium and sodium alginate at 300 °C temperature. Surface morphology (at same magnification),
as well as porosity (%) and pore size distribution results change with metals present in different metal alginates. 相似文献
20.
In the present work, polylactic acid, PLA, samples were degraded by hydrothermal treatment, and then their molecular weights,
crystallinity, surface charges and compositions, were determined, respectively, by using viscometry, 1H NMR, Differential Scanning Calorimetry (DSC), microelectrophoresis and Infra Red spectroscopy methods. The viscometry and
1H NMR data indicate that the molecular weight, of the polymer, decreases after the hydrothermal treatment. However, the crystalline
fractions of the PLA samples, as obtained from the DSC and X-ray data, were not altered after the hydrothermal treatment.
Furthermore, the zeta potential data, as determined by microelectrophoresis, show for both non-degraded and degraded PLA,
an increase of the polymer surface charge density with the pH of the aqueous phase. However, at acidic pH values, the surface
charge density for the degraded PLA was higher as compared to the non degraded one. These differences in surface charge densities
of the PLA samples were confirmed by Infrared study, according to which the spectra of degraded polymer show the appearance
of carboxyl groups occurring at 1,600 cm−1 at the polymer surface. 相似文献