bluuebunny/crossref_metadata_2025_split huggingface dataset:
R&D status of biodegradable polymers in Korea
Authors: Kim Soo Hyun , Kim Young Ha 
Published: March 2011

AbstractSeveral companies have developed inherently biodegradable plastics based on starch and foam for loose‐fill packaging material was the representing case. It is water soluble, but the change of the resilience and volume is less than several % when it is laid open at 32 °C, RH 70%. Starch‐based polyvinylalcohol, aliphatic polyester, polycaprolactone biodegradable polymers were developed also. The PET fiber manufacturing companies have developed aliphatic polyester biodegradable plastics based on diol (butanediol, ethylene glycol) and diacid (succinic acid, adipic acid). The polymers have shown good mechanical properties and processibilities. They have succeeded to apply for injection, films, sheets, extrusion coatings, filaments, non‐woven products, foams, and blow molding and lead this area in Korea. Polyhydroxybutyrate(PHB) and its copolymer were the first biodegradable polymer introduced in Korea. The gene cloning and recombinant technology was succeeded to produce PHB and PHB/V by E‐coli and to yield the higher productivity than before. Lactic acid production and direct condensation polymerization of lactic acid is also being developed.
Biodegradation of PVA‐based formulations
Authors: Chiellini Emo , Corti Andrea , D'Antone Salvatore , Solaro Roberto 
Published: March 2011

AbstractInvestigation of the biodegradability of water soluble poly(vinyl alcohol) (PVA) based blown films was carried out under different lab‐scale environmental conditions. In particular respirometric tests were utilized in order to evaluate the biodegradability of PVA films in composting, in modified Sturm test and in soil burial simulation tests. Several microbial inocula present in river water, mature compost, forest and farm soils as well as sewage sludge from municipal and paper mill wastewater treatments plants were utilized for the relevant tests. A mixed PVA‐degrading microbial culture was obtained by a common enrichment procedure by using sewage sludge from paper mill as inoculum; this culture was tentatively utilized for the isolation of single PVA‐degrading microorganisms. As a first result we can stress that significant biodegradation extent in fairly low incubation time can be obtained only in the presence of acclimated microbial populations such as those deriving from paper mill sewage sludge, in liquid cultures. Nevertheless separation of single degrading microbial species was impossible most likely due to the establishment of symbiotic or commensal interactions between the single components of the PVA‐degrading mixed cultures. On the other hand, limited mineralization rates were recorded in solid cultures in the presence of soil or compost. Finally, a mechanism of degradation of polymer chains unlike random or unzipping was suggested in the presence of either PVA‐degrading mixed culture and its filtrate by means of viscometric determinations of molecular weight within the time.
Chemoenzymatic synthesis of biodegradable polymers containing glucobiose branches
Authors: Kitagawa Masaru , Chalermisrachai Panpaka , Fan Hong , Tokiwa Yutaka 
Published: March 2011

AbstractPolymerizable sugar esters including glucobiose were synthesized from maltose or trehalose and divinyl adipate using enzyme in DMF. 13C NMR data showed that 6'‐position of maltose and mono‐6‐position of trehalose were esterified. Further, these glucobiose esters was polymerized with azo‐initiator to give the corresponding polymers.
Direct condensation polymerization of lactic acid
Authors: Kim Soo Hyun , Kim Young Ha 
Published: March 2011

AbstractIn order to synthesize the higher molecular weight poly(lactic acids) by direct condensation polymerization of lactic acid, dipentaerythritol was used as a chain branching agent. Poly(lactic acids) of high molecular weight, 67000(Mn), was obtained by using antimony trioxide catalyst with good color. This poly(lactic acids) showed Tg of 54.8 °C, Tm of 147 °C and cold crystallization temperature of 115 °C. The polymer could be melt processed into transparent films. Tensile modulus of 311 Kg/ mm2, tensile strain of 21% and tensile strength of 12.41 Kg/ mm2 were obtained for film collected at 400%/min and drawn 4 times.
Effect of additives on gelatinization, rheological properties and biodegradability of thermoplastic starch
Authors: Yu L. , Christov V. , Christie G. , Gray J. , Dutt U. , Harvey T. , Halley P. , Coombs S. , Jayasekara R. , Lonergan G. 
Published: March 2011

AbstractEffect of additives on the starch gelatinization was governed by the processing conditions. The order‐disorder transition of starch in water can occur in more than one way and the effect of polar additives on gelatinization can also be in more than one way. The additives appear to be plasticising thermoplastic starches, resulting in improving rheological properties. The thermoplastic starches with the additives are all biodegradable although the rates of biodegradability are slightly different.
Studies on degradation of PET in mechanical recycling
Authors: Frounchi Masoud 
Published: March 2011

AbstractPET Poly(ethylene terephthalate) was processed repeatedly in a twin extruder. Effect of reprocessing on molecular structure of PET was evaluated in terms of reduction in molecular weight and mechanical properties. This study shows that weight‐average molecular weight Mw drops more notably compared with mechanical properties. Mechanical blending of virgin polymer with recycled PET was studied. The results of mechanical testings indicate that there is only slight loss in mechanical properties. The results suggest that mechanical recycling is a suitable method for recycling of PET for economic and environmental purposes.
Molecular mobility, structural organization and complexing properties of copolymer macromolecules
Authors: Anufrieva Elizaveta V. , Gromova Raisa A. , Kirsh Yurii E. , Krakovyak Mark G. , Yanul Natalya A. , Lushchik Vanda B. , Pautov Vladimir D. , Sheveleva Tamara V. 
Published: March 2011

AbstractIntramolecular mobility, an intramolecular structure formation, and complexing properties of VP‐VC (N‐vinylpyrrolidone and N‐vinylcaprolactame) copolymer macromolecules with a low content of the “hinge” VP units in aqueous solutions upon heating, phenol or SDS (sodium dodecyl sulfate) adding were studied by luminescence. The data obtained show that a slight modification of a polymer chain structure with the aid of the “hinge” units inclusion leads to a considerable change in structural and complexing properties of the copolymers.
Molecular dynamics in nanostructured polyimide‐silica hybrid materials and their thermal stability
Authors: Bershtein Vladimir A. , Egorova Larisa M. , Yakushev Pavel N. , Georgoussis George , Kyritsis Apostolos , Pissis Polycarpos , Sysel Petr , Brozova Libuse 
Published: March 2011

AbstractMolecular motion and thermal stability in two series of nanophase‐separated polyimide‐silica (PI‐SiO2) hybrid networks with chemically bound components were studied. The hybrids were prepared via a sol‐gel process and differed in PI structure and chain length, and in SiO2 content ranging from 10 to 50 wt.%. Differential scanning calorimetry, laser‐interferometric creep rate spectroscopy, dielectric relaxation spectroscopy, thermally stimulated depolarization current techniques, and thermogravimetry were used covering, on the whole, the ranges of 100–900 K and 10−3‐109 Hz. Silica domains influenced PI dynamics in two opposite directions. Loosened segmental packing in chains confined to nanovolumes resulted mainly in rise of small‐scale motion below β‐relaxation region, while anchoring of chain ends to ‘rigid walls’ caused, contrarily, a partial or total suppression of segmental motion above Tβ, especially drastically at the temperatures close to and within glass transition. The latter resulted in a large change in thermal stability, e.g., 2.5‐fold increasing of the apparent activation energy of thermooxidative degradation, and more than 100° rise of predicted long‐term thermal stability for the hybrids as compared to that for PI.
The comparison of relaxation events with spectroscopic properties of polymer composites with fibrillar dopings on the basis of low density polyethylene and polypropylene
Authors: Mamedov Shaval V. , Alekperov Vilayet A. , Ozcanh Yesim 
Published: March 2011

AbstractIn this study, the mechanical and electrical degradation properties of the composites of polypropylene (PP)+PP fibers, low‐density polyethylene(LDPE)+PP fiber, and PP+fiber glass have been investigated and the validity of Zhourkov's thermofluctuation theory has been shown.
Alternative theory of hydrodynamic interactions in polymer solutions
Authors: Borodin Igor P. , Khazanovich Teodor N. 
Published: March 2011

AbstractThe model is presented for coarse grained dynamics of macromolecules in dilute solutions. The coarse graining is achieved by dividing the polymer chain into subchains, consisting of many monomers, and spatial averaging over lengths that are large compared to the mean‐square end‐to‐end distance of subchains and small compared to macromolecule size. Kinetic equations of the model are derived from first principles of statistical mechanics under the assumption that subchain center of mass positions and solvent flow velocity field are the only slow variables of the system. In this approach hydrodynamic interactions result from the intercomponent friction forces between polymer and solvent instead of boundary conditions on the bead surfaces as in traditional theories. The integrodifferential diffusion equation is obtained for steady flows with the kernel involving the Oseen tensor multiplied by equilibrium distribution in the space of the subchain center of mass positions.
Computer modelling of structure and dynamics of C‐50 n‐paraffin crystal, hexagonal phase of C‐50 crystal and ethylene/propylene statistical copolymers
Authors: Oleinik Eduard , Karmilov Ilya , Shenogin Sergei , Kalashnikov Alexander , Mazo Michael , Balabaev Nikolai , Chvalun Sergei 
Published: March 2011

Abstract3D crystal of n‐paraffin C‐50 was created by computer molecular dynamics method. The crystal consists of 48 chain molecules containing 48 ‐CH2‐groups and two ‐CH3 end groups each. Constant temperature‐constant pressure calculations, spatially periodic boundary conditions, integration step 0.001 ps were used. Chemical bonds were treated as absolutely rigid, bond angles bending were treated trough U(θ)=½Kθ(θ‐θ0)2 function and torsion rotations trough Uφ=Cφ/2[1+Zφ(3cos3(φ)‐2cos(φ))] function. Non‐bonded interactions were represented as truncated and shifted L‐D 6–12 potential function. All atoms were introduced explicitly. At 200K and 36 ps of relaxation we got computer C‐50 crystal with orthorhombic symmetry (o‐phase) and cell parameters a=7,416Å, b=4,723Å, c=2,625Å and density ρ=1,014 g/cm3 which are close to known from literature. Heating of the crystal up to 450K have shown thermal expansion along all crystallographic axes well coinciding with known experiment. At 400K the system posses transition to hexagonal phase (h‐phase). At 450K the crystal melts, but high orientation of chain axes still exists in the system. Analysis of rotational and translation mobility of h‐phase at 400K have shown that all chains undergo fast rotation around chain axes for angles about 200–3600 during 15 ps. Quenching of the h‐phase to 200K decrease the rotation amplitude up to ±12° corresponding to vibrations. The same type vibration motions (around chain axes) exists in o‐phase at 200K. Replacing of some H‐atoms in chains of initial crystal by ‐CH3 groups gave us the possibility to mimic Ethylene/Propylene copolymers. In this work we have created only random E/P copolymers with propylene (PP) units content up to 20%. At constant temperature (200K) increase of PP units in the copolymer produce a disordering initially perfect C‐50 crystal. The process goes anisotropically: long range order becomes violated along b‐direction of the initial crystal at [PP]=3,5% and along a‐direction pronounced order still exists at [PP]=10%. Analysis of structural alterations which appear in the system upon introduction of chemical defects (‐CH3 groups) was done by calculations of local volumes (Vloc) of each site containing three chain carbon atoms with the closest neighbours from the surrounding chains. Increase of [PP] concentration in copolymer increases Vloc and broaden it up considerably. The result shows broad distribution of crystalline cell sizes in copolymers. Local volumes of cells containing ‐CH3 groups might be larger or smaller than mean Vloc value. Some conclusions about conformation defects in chains appearing due to “copolymerisation” (appearing of PP‐units in chains) are drawn.
New conformations and new types of helix sense reversals and defects in the chains of nonchiral poly(alkyl isocyanates)
Authors: Lukasheva Natalia V. , Niemela Satu , Neelov Igor M. , Darinskii Anatolii A. , Sundholm Franciska , Cook Robert 
Published: March 2011

AbstractMolecular mechanics studies of helix sense reversals and defects of the regularity in the helices of the same sense in the chains of poly(alkylisocyanates) were performed. The effect of medium was studied by using different values of the dielectric constant. Additionally to the reversals between the helix mirror images (MI) considered in the literature new types of reversals have been investigated. These reversals connect the helices having backbone torsion angles not only with opposite signs but also with inverse angle values (MII). For the MI reversals we report in addition to the small angle break conformations known from literature the discovery of new conformations of similar energy but with large angle breaks. Large angle reversals can be responsible for up to 50% of the chain persistence length in non‐polar solvents. In vacuum MII reversals and defects have energies higher than MI reversals because of the strong electrostatic repulsion. At ϵ = 3.5 some defects have energy even lower that that of MI reversals.
The anharmonic character of Tg and Tm transition
Authors: Hlaváček B. , Křesálek V. , Souček J. 
Published: March 2011

AbstractThe idea of anharmonic oscillations has been extended to explain the glass transition or melting point. All ideas of free volume, vacancy transport, etc., have been respected but are treated as minor phenomena relative to harmonic‐anharmonic vibration transition. A simple model of coupled oscillators is studied. It is shown that coupled anharmonic oscillators can produce vibrations on entirely different levels of amplitudes, which explains the highly different coefficients of thermal expansion and cp values for solid and liquid states. At higher temperatures, for polymers in the rubber‐like zone, the theory of anharmonic coupled oscillators brings certain justification for the theories of De Gennes, Doi and Edwards or Rouse. The solid‐liquid transition seems to be connected on microlevel mainly with the enlargement of vibrational amplitudes of monomer or dimer units in polymer chain as the temperature increases.
Heterogeneity of crystalline structure of injection‐moulded and drawn isotactic polypropylene studied by DSC
Authors: Kratochvil J. , Kotek J. , Sikora A. , Raab M. 
Published: March 2011

AbstractDifferential scanning calorimetry (DSC) was used to characterize crystalline structure of injection‐moulded specimens of isotactic polypropylene and corresponding materials prepared by solid‐state drawing at various temperatures. It was shown that the DSC can assess the differences between individual specimens and structural gradients and heterogeneities within one typical test piece. In particular, relative proportions of the crystalline α and β modifications in different locations of an injection‐moulded specimen and structural transformation in the neck shoulder could be established. Variations of the crystalline structure along the edge of drawn specimens were interpreted as a record of temperature and stress fluctuations in the propagating neck shoulder.
Mechanical properties of recycled polymers
Authors: La Mantia Francesco Paolo 
Published: March 2011

AbstractModifications of structure and morphology of the polymers induced by the thermomechanical stress (or by the presence of water for some polymers) during reprocessing can cause a drastic deterioration of mechanical properties of the recycled material. The property ‐ reprocessing relationships are an important tool to determine not only the properties of the recycled polymers but also the strategies to use (processing conditions, stabilizers, fillers, compatibilizers, etc) in order to obtain recycled polymers with good mechanical properties. In this work, typical behaviour of some mechanical properties as a function of the number of reprocessing operations is discussed and correlated with their structure and morphology. The influences of the type of apparatus and of the processing conditions are also considered.
Lignocellulose ‐ polymer composites
Authors: Mansour Olfat , El‐Hady Bothina Abd , Ibrahim Samir K. , Goda Magda 
Published: March 2011

AbstractWater hyacinth and its mechanical pulps were used as lignocellulose to produce composites together with polystyrene or urea‐formaldehyde resins. The bending strength of the composites increased with increasing concentration of the resin. The temperatures of the treatment of water hyacinth to obtain the pulps affect the strength and densities of the composites. This may be attributed to the behavior of lignin at temperatures higher than 135°C. The composites produced using urea‐formaldehyde resins showed slight increase in bending strengths compared with those produced using polystyrene, which may be attributed to the ability of formaldehyde to make crosslinks with the free OH groups of cellulose and hemicellulose. Contrary to water hyacinth, the use of ground palm leaves together with 10% urea‐formaldehyde resin produced composite with high density and low bending strength, while the ground water hyacinth failed. The pulp from palm leaves when processed into composites using 10% urea‐formaldehyde resin show bending and densities affected by its preparation and by the amount of the composite mixture to be pressed. Hence the type of the substrate defined the type of the polymers or resin used to obtain composites with proper mechanical properties. The effect of the pressure used to produce composites from ground palm leaves or their pulp together with polystyrene was investigated. Linear relationships between the bending strength and pressure were obtained, the bending strength and densities increasing with increasing pressure. Thus, the increased pressures enhance mechanical properties of the composites.
Conformational transformations in chiral polythiophene derivatives aggregated in polymethacrylate matrices: Experiments and molecular dynamics simulations
Authors: Bjornholm Thomas , Brostow Witold , Schaumburg Kjeld , Shibaev Peter V. , Sinani Vladimir , Vinokur Rostislav 
Published: March 2011

AbstractChiral derivatives of poly(3‐(S‐3',7'‐dimethyloctyl)thiophene) embedded in either poly(methyl methacrylate) (PMMA) or poly(butyl methacrylate) (PBMA) were studied by polarization optical microscopy, UV absorption and circular dichroism (CD) spectroscopy as well as simulated using the Molecular Dynamics procedure. CD spectra change on heating to mirror spectra; for PMMA‐containing blends the changes in heating/cooling cycles are reversible. The signs of CD spectra depend on free volume, the packing of side groups in particular. Since in the melt there are no restrictions on the positions of the chiral groups, those groups appears with equal probabilities at any locations with respect to the thiophene ring. By contrast, in clusters restrictions imposed by other alkyl chains result in positioning of chiral methyl groups preferentially on the left or right sides of the thiophene rings. The consequence is the formation of right or left twists in molecular backbones.
Compatibility of a statistical copolymer p(EMA‐CO‐MMA) with PS and PMMA
Authors: Schubert Dirk W. , Pannek Michael , Müller Axel H. E. 
Published: March 2011

AbstractThe compositions of coexisting phases and the interface widths in blends of a statistical copolymer of poly(ethylmethacrylate — co — methylmethacrylate) (P(EMA1,x‐co‐MMAx)) and a deuterated polystyrene (PS(D)) as well as a deuterated poly(methylmethacrylate) (PMMA(D)) have been investigated by neutron reflectometry (NR). Interaction parameters are calculated from the compositions of coexisting phases and the interface width values. Utilizing a novel two dimensional scheme for graphical representation of the interaction parameters, the results are in very good agreement with studies on the interaction parameters for PS/PMMA, PS/PEMA and PEMA/PMMA blends. In particular, XEMA/MMA deduced from a NR experiment on a P(EMA‐block‐MMA(D)) diblock copolymer fits excellent into the scheme.
Oriented crosslinked polyethylene pipes by a novel extrusion method
Authors: Järvenkylä Jyri , Johansson Bengt , Ek Carl‐Gustaf , Palmlöf Magnus , Ahjopalo Lisbeth , Kuutti Lauri , Pietilä Lars‐Olof , Neway Bereket , Gedde Ulf W. 
Published: March 2011

AbstractCrosslinking and stretching (2.5 times along the circumferential direction) of the molten polymer during extrusion produced pipes with dominantly circumferential orientation and a lower degree of axial chain orientation. Differential scanning calorimetry (crystallinity and crystal thickness), density measurements (crystallinity), X‐ray diffraction (c‐axis orientation), infrared dichroism measurements (crystalline and amorphous chain orientation) and contraction measurements (molecular draw ratio) assessed the microstructure of the pipe material. The mechanical properties of the oriented material were assessed by uniaxial tensile tests. The orientation was biaxial with the main orientation in the circumferential direction and a lesser orientation in the axial direction. The maximum degree of circumferential orientation was obtained at the inner wall of the pipe. The lower degree of crosslinking of the core material allowed slippage of chains during the stretching of the molten polymer and it is suggested that this is the cause of the lower degree of orientation of the core material. The oriented pipe material exhibited a 5‐10% higher degree of crystallinity and higher crystal thickness than conventionally crosslinked material. The tensile modulus and the tensile strength of the oriented, cross‐linked material was greater along the axial direction than along the circumferential direction. The circumferential and axial moduli for the oriented, crosslinked pipe were greater than the corresponding moduli of the non‐oriented cross‐linked pipe material. Another pipe based on crosslinked PE that were first circumferentially stretched 2.5 times and later axially stretched 10 times (in the molten state) showed, despite the fact that it exhibited pronounced axial orientation almost a balanced tensile modulus (4.3±0.2 GPa) in the axial‐circumferential plane. Atomistic modelling showed that the orientational dependence of the density of the amorphous phase is small.
Study of dye diffusion in fibers by laser scanning confocal microscopy
Authors: Song Ye , Srinivasarao Mohan , Tonelli Alan 
Published: March 2011

AbstractThe diffusion of a fluorescent dye in nylon 66 fibers was studied by using a laser scanning confocal microscope (LSCM) and by a conventional method. The diffusion coefficients were determined by both methods and they were in close agreement. The study of dye diffusion in fibers by LSCM is simple, quick and also able to provide high resolution images of fiber cross‐sections and 3D images of the dye distribution in fibers. To our knowledge this is the first report of using a LSCM to study dye diffusion in polymeric fibers.