共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
Huizhen Zhao Tianqiang Wang Xiuli Zhao Yu Liu Jianyuan Hao 《Journal of Polymers and the Environment》2013,21(2):405-414
Two different polymerization routes, one-step and two-step bulk ring-opening polymerizations of d,l-lactide (LA) and p-dioxanone (PDO) monermers using stannous octoate [Sn(Oct)2]/n-dodecanol as the initiating system, were employed to synthesize poly(d,l-lactide-co-p-dioxanone) P(LA-co-PDO) random and segmented copolymers with different compositions and chain microstructure. For the two-step copolymers, the average sequence lengths of the lactidyl (LLA) and dioxanyl (LPDO) units calculated from the 1H-NMR spectra were much longer than those values for the one-step copolymers with the same LA/PDO feed ratio. Corresponding to this difference in microstructure, the two-step copolymers were semi-crystalline even when the PDO content was as low as 14.5 mol%, while the one-step copolymers were completely amorphous with PDO content below 60.6 mol%. However, irrespective of polymerization route, both types of copolymers displayed a single glass transition temperature that was in a linear relation with composition. The decrease of maximum decomposition temperature of the copolymers was in accordance with the decrease of LPDO value. The mechanical and degradation properties of the copolymers were significantly affected by both the polymerization route and the chemical composition as well. In conclusion, the properties of P(LA-co-PDO) copolymers could be adjusted conveniently to meet specific applications by changing the composition and microstructure of the copolymers via different polymerization routes. 相似文献
3.
Du?ica Ili? Ivan S. Risti? Ljubi?a Nikoli? Mihajlo Stankovi? Goran Nikoli? Ljiljana Stanojevi? Vesna Nikoli? 《Journal of Polymers and the Environment》2012,20(1):80-87
In this work was described poly(d,l-lactide) microwave synthesis using tin(II) 2-ethylhexanoate initiated ring-opening polymerization. Polymerization was performed
at 100 °C with monomer to initiator molar ratio ([M]/[I]) of 5,000 in 30 min. The achieved number average molar mass of obtained
polymers (determined by gel permeation chromatography) was 102,320 g/mol, with the polydispersion index, Q, 2.80. Structural characterization was performed by FT-IR spectroscopy followed characteristic bands. For applicative purposes
the obtained polymer was purified during the procedure of microsphere preparation. Biodegradable microspheres prepared from
poly(d,l-lactide) have been widely studied in recent years and have become well established controlled drug delivery systems. In this
work microspheres were loaded with allyl thiosulfinate (allicin) and its transforments products (ajoene and vinyldithiine),
as pharmacological active substances. The morphology of the microspheres was analyzed using a scanning electron microscope.
Allicin was synthesized by acid oxidation of allyl disufide and purification of obtained products by liquid–liquid extraction
with diethyl ether. Obtained allicin, purity 73%, was transformed using microwave in acetone solution, at solvent boiling
temperature, for 5 min. For the quality and quantity analysis of allicin and its transformation process was used LC/MS chromatography.
(E)- and (Z)-ajoene were detected at retention time 3.1 and 3.3 min, respectively, whence 3-vynil-4H-1,2-dithiine and 2-vynil-4H-1,3-dithiine
were detected at 4.3 and 4.8 min, respectively. Retention time of allicin was 2.93 min, according to liquid chromatography
results. HPLC method was used for assessment of pharmaceutical substances (alicine and alicine transforments) releasing from
microspheres at room temperature in solutions with different pH (pH = 3 and pH = 8) for 24 h. 相似文献
4.
Shadpour Mallakpour Fatemeh Zeraatpisheh Mohammad R. Sabzalian 《Journal of Polymers and the Environment》2012,20(1):117-123
In this paper we studied the synthesis of biodegradable optically active poly(ester-imide)s containing different amino acid
residues in the main chain. These pseudo-poly(amino acid)s were synthesized by polycondensation of N,N′-(pyromellitoyl)-bis-l-tyrosine dimethyl ester as a diphenolic monomer and two chiral trimellitic anhydride-derived diacid monomers containing s-valine and l-methionine. The direct polycondensation reaction of these diacids with aromatic diol was carried out in a system of tosyl
chloride (TsCl), pyridine (Py) and N,N′-dimethylformamide (DMF) as a condensing agent. The structures and morphology of these polymers were studied by FT-IR, 1H-NMR, powder X-ray diffraction, field emission scanning electron microscopy (FE-SEM), specific rotation, elemental and thermogravimetric
analysis (TGA) techniques. TGA profiles indicate that the resulting PEIs have a good thermal stability. Morphology probes
showed these polymers were noncrystalline and nanostructured polymers. The monomers and prepared polymers were buried under
the soil to study the sensitivity of the monomers and the obtained polymers to microbial degradation. The high microbial population
and prominent dehydrogenase activity in the soil containing polymers showed that the synthesized polymers are biologically
active and microbiologically biodegradable. Wheat seedling growth in the soil buried with synthetic polymers not only confirmed
non-toxicity of polymers but also showed possibility of phyto-remediation in polymer-contaminated soils. 相似文献
5.
Romeu Casarano Denise F. S. Petri Michael Jaffe Luiz H. Catalani 《Journal of Polymers and the Environment》2010,18(1):33-44
A new aliphatic block copolyester was synthesized in bulk from transesterification techniques between poly((R)-3-hydroxybutyrate)
(PHB) and poly(isosorbide succinate) (PIS). Additionally, other two block copolyesters were synthesized in bulk either from
transesterification reactions involving PHB and poly(l-lactide) (PLLA) or from ring-opening copolymerization of l-lactide and hydroxyl-terminated PHB, as result of a previous transesterification reactions with isosorbide. Two-component
blends of PHB and PIS or PLLA were also prepared as comparative systems. SEC, MALDI-TOF mass spectrometry (MALDI-TOFMS), 1H and 13C NMR spectroscopy, WAXD, solubility tests, and TG thermal analysis were used for characterization. The block copolymer structures
of the products were evidenced by MALDI-TOFMS, 13C NMR, and WAXD data. The block copolymers and the corresponding binary blends presented different solubility properties,
as revealed by solubility tests. Although the incorporation of PIS sequences into PHB main backbone did not enhance the thermal
stability of the product, it reduced its crystallinity, which could be advantageous for faster biodegradation rate. These
products, composed of PHB and PIS or PLLA sequences, are an interesting alternative in biomedical applications. 相似文献
6.
Treatment of discarded oil in supercritical carbon dioxide for preparation of carbon microspheres 总被引:1,自引:0,他引:1
Binxing Yu Xiangkai Kong Lingzhi Wei Qianwang Chen 《Journal of Material Cycles and Waste Management》2011,13(4):298-304
Carbon microspheres with diameter of 1–10 μm were prepared by treatment of waste oil in a supercritical carbon dioxide (scCO2) system. The structure and morphology of the products were characterized by X-ray diffraction, field-emission scanning electron
microscopy, and Raman spectrometry. It is shown that the products consist of graphite microspheres with relatively low graphitization.
The yield of solid products increased from 26.8 wt% to 42.2 wt% as the reaction temperature was raised from 530°C to 600°C.
Spheres with multilayer structure could be obtained by means of subsequent vacuum annealing of the carbon microspheres at
1500°C. The formation mechanisms of carbon microspheres in the scCO2 system and the influence of vacuum annealing on the structure are discussed in detail. 相似文献
7.
Six strains of Pseudomonas were tested for their abilities to synthesize poly(hydroxyalkanoate) (PHA) polymers from crude Pollock oil, a large volume
byproduct of the Alaskan fishing industry. All six strains were found to produce PHA polymers from hydrolyzed Pollock oil
with productivities (P; the percent of the cell mass that is polymer) ranging from 6 to 53% of the cell dry weight (CDW).
Two strains, P. oleovorans NRRL B-778 (P = 27%) and P. oleovorans NRRL B-14682 (P = 6%), synthesized poly(3-hydroxybutyrate) (PHB) with number average molecular weights (Mn) of 206,000 g/mol and 195,000 g/mol, respectively. Four strains, P. oleovorans NRRL B-14683 (P = 52%), P. resinovorans NRRL B-2649 (P = 53%), P. corrugata 388 (P = 43%), and P. putida KT2442 (P = 39%), synthesized medium-chain-length PHA (mcl-PHA) polymers with Mn values ranging from 84,000 g/mol to 153,000 g/mol. All mcl-PHA polymers were primarily composed of 3-hydroxyoctanoic acid (C8:0) and 3-hydroxydecanoic acid (C10:0) amounting to at least 75% of the total monomers present. Unsaturated monomers were also present in the mcl-PHA polymers at concentrations between 13% and 16%, providing loci for polymer derivatization and/or crosslinking.
Mention of trade names or commercial products in this article is solely for the purpose of providing specific information
and does not imply recommendation or endorsement by the U.S. Department of Agriculture. 相似文献
8.
Randal L. Shogren Kenneth M. Doll J. L. Willett Graham Swift 《Journal of Polymers and the Environment》2009,17(2):103-108
l-Aspartic acid was thermally polymerized in the presence of d-sorbitol with the goal of synthesizing new, higher molecular weight water soluble and absorbent copolymers. No reaction occurred
when aspartic acid alone was heated at 170 or 200 °C. In contrast, heating sorbitol and aspartic acid neat or with ammonium
hydroxide gave a mixture of water soluble and insoluble copolymers of polysuccinimide and sorbitol. In the presence of phosphoric
acid, sorbitol aspartate ester copolymers having both water soluble and highly swollen gel components were formed. These results
indicate that polysaccharides such as sorbitol can readily react to form copolymer ester/amides with aspartic acid and such
copolymers may have utility as biodegradable water soluble and swellable polyampholytes. 相似文献
9.
Atsuyoshi Nakayama Norioki Kawasaki Ioannis Arvanitoyannis Seiichi Aiba Noboru Yamamoto 《Journal of Polymers and the Environment》1996,4(3):205-211
Biodegradable polyesters were synthesized by ring-opening copolymerization of -butyrolactone (BL) and its derivatives withl-lactide (LLA). Although tetraphenyl tin was the main catalyst used, other organometallic catalysts were used as well.1H and13C NMR spectra showed that poly(BL-co-LLA)s were statistical and that their number-average molecular weights were as high as 7×104. The maximum BL content obtained from copolymerization BL/LLA was around 17%. TheT
m andT
g values of the copolymers showed a gradual depression with an increase in BL content. NoT
m was obtained for the copolymers containing more than 13 mol% BL. The biodegradability of the copolyesters was evaluated by enzymatic hydrolysis and nonenzymatic hydrolysis tests. The enzymatic hydrolysis was carried out at 37°C for 24 h using lipases fromRhizopus arrhizus andR. delemar. Hydrolyses by both lipases showed that an increase in BL content of the copolymer resulted in enhanced biodegradability. Nonenzymatic accelerated hydrolysis of copolymers at 70°C was found to increase proportionally to their exposure time. The hydrolysis rate of these copolymers was considerably faster than that of PLLA. The higher hydrolyzability was recorded for the BL-rich copolymers. The copolymerization of -methyl--butyrolactone (MBL) or -ethyl--butyrolactone (EBL) with LLA resulted in relatively LA-rich copolymers. 相似文献
10.
Giuseppe Impallomeni Salvatore P. P. Guglielmino Santina Carnazza Annamaria Ferreri Alberto Ballistreri 《Journal of Polymers and the Environment》2000,8(2):97-102
The ability of Pseudomonas aeruginosa ATCC 27853 to grow and synthesize polyhydroxyalkanoates (PHAs) using Tween 20 as the sole carbon source was investigated. Tween 20 could support cell growth and PHA production. The polymer produced from Tween 20 was compared with those produced from its major free fatty acids components: lauric (C12), myristic (C14), and palmitic (C16) acids. Gas-chromatographic analysis of methanolyzed samples and 13C-Nuclear Magnetic Resonance (NMR) showed that the PHAs obtained are composed of even carbon atoms 3-hydroxyalkanoates ranging from C6 to C14, with C8 and C10 as the predominant components. The nature of the carbon sources used had little influence on the composition, but was found to be important in determining the average molecular weight, shorter chain fatty acids yielding higher molecular weight products. Fast Atom Bombardment-Mass Spectrometry (FAB-MS) of partially pyrolyzed samples, coupled to statistical analysis, showed that these PHAs are random copolymers. 相似文献
11.
There is a wide range of applications where calcium phosphate and hydroxyapatite (HA) are used as biomaterials, e.g. as synthetic
bone grafts, coating on metal prostheses (like hip endoprostheses or dental implants) and drug carriers. In the study, the
design and synthesis of composites based on poly(vinyl alcohol-co-lactic acid)/hydroxyapatite (PVA-co-LA/HA) with potential
for biomedical applications, they are presented. The hydroxyapatite particles were surface-grafted with l(+)-lactic acid in the presence of manganese acetate as catalyst, resulting in modified hydroxyapatite (HAm) with improved capacity of bonding, respectively for the preparation of the composite based on PVA-co-LA/HAm. FT-IR spectra further confirmed the existence of PLA polymer on the surface of HA particles. In synthesis of PVA-co-LA copolymer
the different molar ratios PVA/LA (2/1, 1/1, 1/2), toluene/water: 1/2 (as azeotrope solvent mixture) and manganese acetate
as catalyst, were used. The composite materials were synthesized in situ with 10 wt% HA, and respectively HAm (reported to PVA and lactic acid components). The composite materials were characterized by FTIR spectroscopy, thermal analyses
(DSC, DTG), 1H-NMR spectroscopy, particle size distribution and zeta potential. 相似文献
12.
Masahiro Funabashi Fumi Ninomiya Edgar Dulay Flores Masao Kunioka 《Journal of Polymers and the Environment》2010,18(2):85-93
The evaluation method of biomass carbon ratio of polymer composite samples including organic and inorganic carbons individually
was investigated. Biodegradable plastics and biobased plastics can have their mechanical properties improved by combining
with inorganic fillers. Polymer composites consisting of biodegradable plastics and carbonate were prepared by two different
methods. Poly(lactic acid) (PLA) composite was prepared by synthesis from l-lactide with catalyst and calcium carbonate (CaCO3) powders from lime. Poly(butylene succinate) (PBS) composite was prepared by hot-pressing the mixture of PBS powder and CaCO3 powders from oyster shells. The mechanical properties of composite samples were investigated by a tensile test and a compression
test using an Instron type mechanical tester. Tensile test with a dumbbell shape specimen was performed for PBS composite
samples and compression test with a column shape specimen for PLA composite samples. Strength, elastic modulus and fracture
strain were obtained from the above tests. Biomass carbon ratio is regulated in the American Standards for Testing and Materials
(ASTM). In ASTM standards on biomass carbon ratio, it is required that carbon atoms from carbonates, such as CaCO3, are omitted. Biomass carbon ratio was evaluated by ratio of 14C to 12C in the samples using Accelerator Mass Spectrometry (AMS). The effect of pretreatment, such as oxidation temperature and
reaction by acid, on results of biomass carbon ratio was investigated. Mechanical properties decrease with increasing CaCO3 content. The possibility of an evaluation method of biomass carbon ratio of materials including organic and inorganic carbons
was shown. 相似文献
13.
N. Mithil Kumar K. Varaprasad K. Madhusudana Rao A. Suresh Babu M. Srinivasulu S. Venkata Naidu 《Journal of Polymers and the Environment》2012,20(1):17-22
Poly (l-aspartic acid-citric acid) green copolymers were developed using thermal polymerization of aspartic acid (ASP) and citric
acid (CA) followed by direct bulk melt condensation technique. Antibacterial properties of copolymer of aspartic acid based
were investigated as a function of citric acid content. This study is focused on the microorganism inhibition performance
of aspartic acid based copolymers. Results showed that inhibition properties increase with increasing citric acid content.
Characterization of obtained copolymers was carried out with the help of infrared absorption spectra (FTIR), x-ray diffraction
(XRD), differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA). The antibacterial activity of copolymers
against bacteria like E-coli, Bacillus and pseudomonas was investigated. The copolymers showed excellent antimicrobial activities
against three types of microorganisms. Overall studies indicated that the above copolymers possess a broad wound dressing
activity against above three types of bacteria and may be useful as antibacterial agents. 相似文献
14.
Daniela Djikanovi? Jasna Simonovi? Aleksandar Savi? Ivan Risti? Danica Bajuk-Bogdanovi? Aleksandar Kalauzi Suzana Caki? Jaroslava Budinski-Simendi? Milorad Jeremi? Ksenija Radoti? 《Journal of Polymers and the Environment》2012,20(2):607-617
In a plant cell wall, lignin is synthesized from several monomeric precursors, combined in various ratios. The variation in monomer type and quantity enables multifunctional role of lignin in plants. Thus, it is important to know how different combinations of lignin monomers impact variability of bond types and local structural changes in the polymer. Lignin model polymers are a good model system for studies of relation between variations of the starting monomers and structural variations within the polymer. We synthesized lignin model polymers from three monomers, CF??based on coniferyl alcohol and ferulic acid in monomer proportions 5:1 and 10:1 (w/w), CP??based on coniferyl alcohol and p-coumaric acid in proportion 10:1 (w/w) and CA??based on pure coniferyl alcohol. We studied structural modifications in the obtained polymers, by combining fluorescence microscopy and spectroscopy, FT-IR and Raman spectroscopy, in parallel with determination of polymers?? molecular mass distribution. The differences in the low M w region of the distribution curves of the 10:1 polymers in comparison with the CA polymer may be connected with the increased content of C=C bonds and decreased content of condensed structures, as observed in FT-IR spectra and indicated by the analysis of fluorescence spectra. The 5:1 CF polymer contains a different type of structure in comparison with the 10:1 CF polymers, reflected in its simpler M w distribution, higher homogeneity of the fluorescence emitting structures and in the appearance of a new high-wavelength emission component. We propose that this component may originate from ??-conjugated chains, which are longer in this polymer. The results are a contribution to the understanding of the involvement of structural variations of lignin polymers in the cell wall structural plasticity. 相似文献
15.
Rodica Lipsa Nita Tudorachi Cornelia Vasile Aurica Chiriac Anca Grigoras 《Journal of Polymers and the Environment》2013,21(2):461-471
Modified natural polymers have been gaining increasing scientific interest for many years. In this study carboxymethyl starch (CMS) was grafted with L(+)-lactic acid (LA) in different molar ratios CMS/LA (1/36, 1/22 and 1/12), resulting carboxymethyl starch-g-poly(lactic acid) (CMS-g-PLA) copolymers. The grafting reaction was carried out by solution polycondensation procedure in toluene and stannous 2-ethyl hexanoate Sn(Oct)2 as catalyst was utilized. Poly(lactic acid) (PLA) was synthesized in the same conditions with the copolymers for comparative analyses of the physico-chemical and thermal properties. The copolymers and PLA were structurally and morphologically characterized by FT-IR, 1H-NMR spectroscopy, WAXD and SEM analyses, taking CMS as reference. The molecular weight of the copolymers, CMS and PLA were determined, using a dynamic light scattering technique. The thermal behavior of the products was studied by DSC and TG-DTG analyses. The CMS-g-PLA graft copolymers exhibited lower Tg and thermal stability than pure CMS. 相似文献
16.
17.
G. Yuan D. Chen L. Yin Z. Wang L. Zhao J.Y. Wang 《Waste management (New York, N.Y.)》2014,34(6):1045-1050
In this research a gas–liquid fluidized bed reactor was developed for removing chlorine (Cl) from polyvinyl chloride (PVC) to favor its pyrolysis treatment. In order to efficiently remove Cl within a limited time before extensive generation of hydrocarbon products, the gas–liquid fluidized bed reactor was running at 280–320 °C, where hot N2 was used as fluidizing gas to fluidize the molten polymer, letting the molten polymer contact well with N2 to release Cl in form of HCl. Experimental results showed that dechlorination efficiency is mainly temperature dependent and 300 °C is a proper reaction temperature for efficient dechlorination within a limited time duration and for prevention of extensive pyrolysis; under this temperature 99.5% of Cl removal efficiency can be obtained within reaction time around 1 min after melting is completed as the flow rate of N2 gas was set around 0.47–0.85 Nm3 kg?1 for the molten PVC. Larger N2 flow rate and additives in PVC would enhance HCl release but did not change the final dechlorination efficiency; and excessive N2 flow rate should be avoided for prevention of polymer entrainment. HCl is emitted from PVC granules or scraps at the mean time they started to melt and the melting stage should be taken into consideration when design the gas–liquid fluidized bed reactor for dechlorination. 相似文献
18.
Ring-opening polymerization of cyclic esters (-caprolactone, -valerolactone, and l-lactide) onto liquefied biomass (LB) was conducted to obtain the polyester-type polyol and to regulate the characteristics of LB. IR and 1H-NMR spectra of the obtained polyol showed that the polymerization was successfully conducted in the presence of acid catalyst, which is used in liquefaction. The molecular weight (Mw), hydroxyl value, and viscosity were controllable by changing the reaction conditions. Polyester-type polyurethane foams with a wide range of properties were prepared from the obtained polyol with the appropriate combinations of foaming agents. 相似文献
19.
Xiaojun Wang Sili Chen Xiaoyang Gu Kaiyan Wang 《Waste management (New York, N.Y.)》2009,29(4):1354-1358
Mature landfill leachate is typically non-biodegradable. A combination process was developed that includes coagulation, Fenton oxidation, and biological aerated filtering to treat biologically-produced effluent. In this process, coagulation and Fenton oxidation were applied in order to reduce chemical oxygen demand (COD) organic load, and enhance biodegradability. Poly-ferric sulfate (PFS) at 600 mg l?1 was found to be a suitable dosage for coagulation. For Fenton oxidation, an initial pH of 5, a total reaction time of 3 h, and an H2O2 dosage of 5.4 mmol l?1, with a (H2O2)/n(Fe2+) ratio of 1.2 and two-step dosing were selected to achieve optimal oxidation. Under these optimal coagulation and Fenton oxidation conditions, the COD removal ratios were found to be 66.67% and 56%, respectively. Following pretreatment with coagulation and Fenton oxidation, the landfill leachate was further treated using a biological aerated filter (BAF). Our results show that COD was reduced to 75 mg l?1, and the color was less than 10 degrees. 相似文献
20.
The degradation products of polymers are identifiable by chromatography. The degradation product patterns (or fingerprints) formed depend on the type of polymer, the degradation mechanism(s), and also the type of additive present in the material. The chromatographic fingerprint of biotically aged degradable low-density polyethylene (i.e., LDPE+starch+prooxidant) shows, in particular, the absence of low molecular weight carboxylic acids, which suggests an assimilation of these carboxylic acids by the microorganisms. The degradation products of natural polymers are usually intermediates that are used again in the anabolic cycles. It is possible to transfer the terminology from the natural polymers, where the catabolism of natural polymers consists of three stages, and apply this also to the degradable synthetic polymers. During stage I the natural polymers degrade to their major building blocks (e.g., amino acids, glycerol, hexoses, pentoses, etc.), during stage II these products are collected and converted to a smaller number of even simpler molecules [e.g., acetyl-coenzyme A (CoA)]. In stage III, finally, the acetyl-CoA enters the citric acid cycle, where energy is gained in parallel with the release of CO2 and H2O.Presented at the international workshop,Polymers from Renewable Resources and their Degradation, Stockholm, Sweden, November 10–11, 1994. 相似文献