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701.
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
702.
Candice DeLeo Caio Augusto Pinotti Maria do Carmo Gonçalves Sachin Velankar 《Journal of Polymers and the Environment》2011,19(3):689-697
Plasticized starch (PLS) is a renewable, degradable, and inexpensive polymer, but it suffers from poor mechanical properties.
The mechanical properties can be improved by blending PLS with polyolefins, nonetheless, at high PLS content, the mechanical
properties remain poor. Here we show that addition of clay can greatly improve the mechanical properties of PLS/polypropylene
blends at high starch content. Unmodified and organically modified montmorillonite clays, MMT and Cloisite 30B respectively,
were added to blends of glycerol-plasticized starch and polypropylene, compatibilized using maleated polypropylene. TEM indicates
that MMT is well dispersed in the PLS phase of the blends, while Cloisite 30B is located both within the PLS phase as well
as at the interface between PLS and PP. At high PLS content, the addition of clay increased the tensile strength and tensile
modulus by an order of magnitude, while reducing the ultimate elongation only slightly. Such improvements are attributable
to both the addition of clay as a reinforcing component, as well as to the change in the two phase morphology due to addition
of clay. 相似文献
703.
Poly-β-hydroxybuyrate (PHB) is a carbon—energy storage material which is accumulated as intracellular granule in variety of
microorganism under nutrient starved conditions. Solid PHB is a biodegradable thermoplastic polymer and is utilizable in various
ways similar to many conventional plastics. Ralstonia eutropha (Alcaligenes sp.), a gram negative bacteria accumulates PHB as insoluble granules inside the cells when nutrients other than carbon are
limited. In this report effort has been made to analyze PHB granule synthesis inside Alcaligenes sp. NCIM 5085 by transmission electron microscopy and qualitative estimation of PHB was carried out by fourier transform
infrared spectroscopy which provide better precision compared to other conventional techniques previously applied for PHB
determination. Maximum PHB concentration of 2.20 ± 0.40 g/L and cell biomass of 3.42 ± 0.20 g/L was obtained after 48.0 h
of fermentation. Leudking-Piret equation deduced mixed growth associated product formation which varies from earlier reports. 相似文献
704.
K. Abdel Tawab M. M. Magida Sayeda M. Ibrahim 《Journal of Polymers and the Environment》2011,19(2):440-446
Blends of water—soluble polymers based on Poly vinyl alcohol (PVA) and Polyethylene glycol (PEG) have been prepared by the
solution casting technique. The effect of various doses of γ-radiation on the structural properties of PVA/PEG polymer blends
with all its compositions has been investigated. From the visual observation of all the blend compositions, it was found that,
the best compatibility of the blend is up to 40% PVA/60%PEG. The structure–Property behavior of all the prepared blends before
and after γ-irradiation was investigated by IR Spectroscopy, thermogravimetric analysis (TGA), mechanical properties and Scanning
electron microscope (SEM). The gel content and the swelling behavior of the PVA/PEG blends were investigated. It was found
that the gel content increases with increasing irradiation dose and PVA concentration in the blend. Swelling percent increased
as the composition of PEG increased in the blend. The results obtained by FTIR analysis and SEM confirm the existence of possible
interaction between PVA and PEG homopolymers. TGA of PVA/PEG blend, before and after γ-irradiation, showed that the unirradiated
and irradiated PVA/PEG blends are more stable against thermal decomposition than pure PVA. Improvement in tensile mechanical
properties of PVA/PEG blends was occurred. 相似文献
705.
Mojtaba Taran Elham Azizi Shahein Taran Nadia Asadi 《Journal of Polymers and the Environment》2011,19(3):750-754
In this study the possibility of poly (3-hydroxybutyrate) production from glycerol was investigated and optimized by Halorcula sp. IRU1, a novel archaea isolated from Urmia lake, Iran in batch experiments. Using Taguchi methodology, three important
independent parameters (glycerol, yeast extract and KH2PO4) were evaluated for their individual and interactive effects on poly (3-hydroxybutyrate) production. It was shown that the
glycerol concentration was the most significant factor affecting the yield of poly (3-hydroxybutyrate). The optimum factor
levels were a glycerol concentration of 8% (v/v), yeast extract 0.8% (w/v) and KH2PO4 0.002% (w/v). The predicted value obtained for poly (3-hydroxybutyrate) production under these conditions was about 81.87%.
We can conclude that Haloarcula sp. IRU1 has a high potential for synthesis of poly (3-hydroxybutyrate) from glycerol. 相似文献
706.
Altaf H. Basta Houssni El-Saied Jerrold E. Winandy Ronald Sabo 《Journal of Polymers and the Environment》2011,19(2):405-412
Investigations have continued for production high performance agro-based composites using environmentally acceptable approaches.
This study examines the role of adding amide-containing biopolymers during synthesis of urea–formaldehyde (UF) on properties
of adhesive produced, especially its adhesion potential. The environmental performance of UF-resin synthesized in the presence
of modified amide-containing biopolymer was evaluated by evaluating the free-HCHO of both adhesive (during processing) and
of the eventual engineered composite product. Also, the benefits of this synthesis-modified adhesive in enhancing the bondability
of sugar-cane fibers used in engineered composite panels was evaluated and compared to using UF-resin. The results obtained
show that, static bending of the produced composites varied from 27.7 to 33.13 N/mm2 of modulus of rupture (MOR) and from 2860 to 3374 N/mm2 of Modulus of Elasticity (MOE); while for internal bond (IB) it’s varied from 0.64 to 0.866 N/mm2. Based on the ANSI and EN Standards modified UF-based agro composites produced meet the performance requirements for high
grade particleboards with respect to static bending strength. These agro-based composite also tested out as having free-HCHO
values of ~13 mg/100 g board. 相似文献
707.
Amir Nourbakhsh Abdollah Hosseinzadeh Farshid Basiji 《Journal of Polymers and the Environment》2011,19(4):908-911
The study was carried out to investigate the effects of filler content and two different compatibilizing agents (Eastman G-3003
and G-3216) on the mechanical properties of polypropylene reinforced with corn stalk and wood flour. In the sample preparation,
three levels of filler loading (30, 40 and 50 wt%) and one level of compatibilizing agent content (2.5 wt%) were used. For
overall trend, with addition of both grades of the compatibilizing agents, tensile and flexural properties of the composites
significantly improved, as compared with the pure PP. Tensile and flexural properties reach a maximum at 40 wt% filler content
and gradually decrease with a further increase in wood particle content. The composites treated with G-3003 gave better results
in comparison with G-3216. This could be caused by the high melt viscosity of G-3003. In general, corn stalk flour filled
composites showed superior mechanical properties. 相似文献
708.
Guang Yang Bo Yang Chao Yuan Weiwei Geng Haizhou Li 《Journal of Polymers and the Environment》2011,19(1):146-151
The effects of manufacturing parameters on mechanical properties of medium density fibreboard (MDF) bonded with modified soy
protein-based glue were studied to find an appropriate manufacture technology. Physical properties of MDF made with different
amount of wax emulsion were measured. Results indicated that water repellent had no obvious influence on physical properties
of soy protein-based MDF boards. The fiberboards bonded with soy protein-based glue showed stronger water resistance properties
than those bonded with urea–formaldehyde (UF) resins. Furthermore, the soy protein-based MDF boards had good quality [25.2%
24 h soak thickness swell (TS), 29.9 MPa modulus of rupture (MOR), 3130 MPa modulus of elasticity (MOE)], which met requirements
of Chinese national standard. Practical processing parameters were obtained by orthogonal experiment, i.e., glue content 8.0%,
hot-press temperature 200 °C, and hot-press time 150 s. 相似文献
709.
Starch nanocomposites have been prepared using mineral clay. Montmorillonite, kaolin and a surface-modified montmorillonite
by dimethyl (hydrogenated tallow alkyl) ammonium cation were used. Starch-g-PCL nanocomposites have been prepared with graft
polymerization through in situ ring-opening polymerization of ε-caprolactone in the presence of starch, Sn(Oct)2 (Tin(II) 2-ethyl hexanoate) as an initiator/catalyst and silicate layers. In fact, the related composites were prepared in
solution method, bulk polymerization and in situ polymerization methods with introducing the mineral clay. The effect of kind
of clay on d-spacing of silicate layers was investigated and the obtained nanocomposites were analyzed using X-ray diffraction.
The obtained compounds were characterized by Fourier transform infrared (FT-IR). Morphology of the prepared nanocomposites
was investigated using scanning electron microscopy and DSC enhanced the study of thermal behaviour of the prepared composite
compounds. 相似文献
710.
Sung-Won Yoo Young Keun Cho Sang-Hwa Jung Kwang-Myung Lee Seung-Jun Kwon 《Journal of Material Cycles and Waste Management》2017,19(2):694-711
In South Korea, nine million tons of fly ash (FA) are annually produced and approximately 70 % is reutilized for industrial demand. For the prompt reuse and insufficient reclamation site, quality control of FA which is main productive construction material from coal ash is very important. Assessed Pozzolanic-activity Index (API) test which needs only 2 days for evaluation of pozzolanic reaction is currently considered as an alternative of activity index measurement. This paper aims for an applicability of API test for prompt quality control and investigation of domestic FA properties. For the work, FAs from two different power plant types are prepared, and quality tests are carried out based on Korean Standards (KS) methods and API method. Lots of test results are compared with those from API and K-value test for FA with age of 7 days–1 year. From the test results for FA aged 1 year, API results are evaluated to be closely related with those from activity index and K-value, and the correlations are improved with increasing ages regardless of plant types. The applicability of API test is verified and the reduced period of FA quality evaluation can accelerate prompt use and the related process of FA. 相似文献