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Polymer Samples (polymer + sample)

Distribution by Scientific Domains

Polymers and Materials Science	84%
Chemistry	15%

Selected Abstracts

Isotactic polypropylene solidification under pressure and high cooling rates.

POLYMER ENGINEERING & SCIENCE, Issue 11 2000
A master curve approach
Solidification in industrial processes very often involves flow fields, high thermal gradients and high pressures: the development of a model able to describe the polymer behavior becomes complex. Recently a new equipment has been developed and improved to study the crystallization of polymers when quenched under pressure. An experimental apparatus based on a modified, special injection moulding machine has been employed. Polymer samples can be cooled at a known cooling rate up to 100°C/s and under a constant pressure up to 40 MPa. Density, Micro Hardness (MH), Wide angle X-ray diffraction (WAXD), and annealing measurements were then used to characterize the obtained sample morphology. Results on one iPP sample display a lower density and a lower density dependence on cooling rate for increasing pressure. Micro hardness confirms the same trend. A deconvolution technique of WAXD patterns is used to evaluate the final phase content of samples and to assess a crystallization kinetics behavior. A master curve approach to explain iPP behavior under pressure and high cooling rates was successfully applied on density results. On the basis of this simple model it is possible to predict the final polymer density by superposition of the effect of cooling rate and the effect of pressure in a wide range of experimental conditions. [source]

Liquid Chromatography of Synthetic Polymers under Limiting Conditions of Insolubility III

MACROMOLECULAR SYMPOSIA, Issue 1 2007
Application of Monolithic Columns
Abstract Summary Performance was evaluated of silica based commercial monolithic rod-like columns in liquid chromatography of synthetic polymers under limiting conditions of enthalpic interactions (LC LC). LC LC employs the barrier effect of the pore permeating and therefore slowly eluting small molecules toward the pore excluded, fast eluting macromolecules. Phase separation (precipitation) barrier action was applied in present study. The barrier was created either by the narrow pulse of an appropriate nonsolvent injected into the column just before the sample solution (LC LC of insolubility , LC LCI) or by the eluent itself. In the latter case, the polymer sample was dissolved and injected in a good solvent (LC LC of solubility , LC LCS). In LC LCI, polymer species cannot break thru the nonsolvent zone while in LC LCS they cannot enter eluent, which is their precipitant. Therefore, polymer species keep moving in the zone of their original solvent. Macromolecules eluting under the LC LC mechanism leave the column in the retention volume (VR) roughly corresponding to VR of the low molar mass substances and can be efficiently separated from the polymer species non-hindered by the barrier action. The known advantages of monoliths were confirmed. From the point of view of LC LCI and LC LCS the most important quality of monolithic columns represents their excellent permeability, which allows both working at high flow rates and injecting very high (in the range of 5%) sample concentrations. Monolithic column tolerate also extremely high molar mass samples (M>10,000 kg,·,mol,1). On the other hand, the mesopores (separation pores) of the tested monoliths exhibited rather small volume and wide size distribution. These shortcomings partially impair the permeability advantage of monoliths because in order to obtain high LC LC separation selectivity a tandem of several monolithic columns must be applied. Presence of large mesopores also reduces applicability of monolithic columns for molar masses below about 50 kg,·,mol,1 because VRs of polymers eluted behind the barrier are similar to that of freely eluting species. The non- negligible break-thru phenomenon was observed for the very high polymer molar masses largely eluting behind the barrier. It is assumed that the fraction of very large mesopores present in the monoliths or association/microphase separation of macromolecules may be responsible for this phenomenon. This is why the presently marketed SiO2 monolithic columns are mainly suitable for the fast purification of the LC LC eluting macromolecules from the polymeric admixtures non-hindered by the barrier-forming liquid. Still, monolithic columns have large potential in the LC LCI and LC LCS procedures provided size (effective diameter) of the mesopores can be reduced and their volume increased. [source]

Effect of Concentration Gradient on the Morphology Development in Polymer Solutions Undergoing Thermally Induced Phase Separation

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 7 2007
Bai Tao Jiang
Abstract Anisotropic porous polymeric materials fabricated from the phase separation method via spinodal decomposition are used in various practical engineering applications. We studied the formation of anisotropic porous polymeric materials numerically, by imposing an initial linear concentration gradient across a model polymer solution. The initial concentration gradient is placed at three different regions of the polymer sample for comparison purposes. All the simulation results are in good agreement with published experimental observations, which are reported from the applications of porous polymeric membranes. The structure development shows that an anisotropic porous morphology forms when an initial linear concentration gradient is applied to the model polymer solution. [source]

Planar aqueous electrode technique for polymer impedance spectroscopy

POLYMER ENGINEERING & SCIENCE, Issue 3 2009
T. Bai
In this article, we develop an aqueous electrode technique that can adapt to complex sample geometries while maintaining perfect contact between the electrodes and the measured sample. In contrast to surface deposited electrodes, the aqueous electrode technique measures the ionic conduction of the polymer sample instead of the inherent dielectric properties of the polymer. Polymer ionic conduction is often related to the polymer thermodynamic state, which itself is closely linked to many other polymer properties. As such, the aqueous electrode method provides an approach to conduct in situ monitoring of polymer samples subjected to degradation; changes in the impedance provide an indication of polymer sample degradation. This article presents the aqueous electrode setup and discusses experimental results obtained using it. Changes in the impedance response of PVC and polyimide films due to moisture absorption, ionic conduction, pinholes, chemical degradation, and temperature are presented. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers [source]

A thermally stimulated depolarization current study of polymers in the glass transition region

POLYMER ENGINEERING & SCIENCE, Issue 1 2001
Joseph S. Sedita
The low-frequency dielectric properties of a number of polymers, composites and blends have been studied using a thermally stimulated depolarization current (TSDC) apparatus that was designed and constructed in-house. The TSDC technique can be used to determine the glass transition of a polymer sample. This TSDC glass transition temperature has been shown to be very similar to that obtained from differential scanning calorimetry (DSC). The actual difference between these two values depends on the heating rates used with each technique, however. TSDC data can also be combined with AC dielectric data to produce a data set, which possesses a very wide frequency range. Finally, individual TSDC relaxation peaks can be fit with the Williams-Walts distribution function to obtain an estimate of their distributions. This is especially useful when studying polymer blends, but could also be utilized in the study of other systems. [source]

Distributive mixing profiles for co-rotating twin-screw extruders

ADVANCES IN POLYMER TECHNOLOGY, Issue 3 2001
Gifford Shearer
Distributive mixing was experimentally measured during polymer melt blending along the length of a co-rotating twin-screw extruder. A mixing limited interfacial reaction between two reactive polymer tracers was employed to gain direct evidence of the generation of interfacial area. Model reactions were performed to validate this novel experimental method. In particular, the conversion was a direct indicator of the interfacial area available for the reaction. Specially designed sampling ports were used to obtain polymer samples along the length of the extruder during its continuous operation. The mixing capabilities of conveying sections and kneading blocks were compared over a wide range of operating conditions. In conveying sections, distributive mixing was controlled by the fully filled fraction. The mixing in kneading blocks depended on the combination of the operating conditions and the stagger angle. © 2001 John Wiley & Sons, Inc. Adv Polym Techn 20: 169,190, 2001 [source]

Preparation of ultra-high-molecular-weight polyethylene and its morphological study with a heterogeneous Ziegler,Natta catalyst

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
G. H. Zohuri
Abstract Ultra-high-molecular-weight polyethylene (PE) with viscosity-average molecular weight (Mv) of 3.1 × 106 to 5.2 × 106 was prepared with a heterogeneous Ziegler,Natta MgCl2 (ethoxide type)/TiCl4/triethylaluminum catalyst system under controlled conditions. The optimum activity of the catalyst was obtained at a [Al]/[Ti] molar ratio of 61 : 1 and a polymerization temperature of 60°C, whereas the activity of the catalyst increased with monomer pressure and decreased with hydrogen concentration. The titanium content of the catalyst was 2.4 wt %. The rate/time profile of the catalyst was a decay type with a short acceleration period. Mv of the PE obtained decreased with increasing hydrogen concentration and polymerization temperature. The effect of stirrer speeds from 100 to 400 rpm did not so much affect the catalyst activity; however, dramatic effects were observed on the morphology of the polymer particles obtained. A stirrer speed of 200 rpm produced PE with a uniform globulelike morphological growth on the polymer particles. The particle size distributions of the polymer samples were determined and were between 14 and 67 ,m. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Synthesis, characterization, and electrical properties of diazophenylene bridged Co, Ni, Cu, Ce, and Er phthalocyanine polymers

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007
Cemil Alkan
Abstract In this research, diazophenylene bridged metal-phthalocyanine (Pc) polymers were produced from diazonium salt of 1,4-diaminophenylene and presynthesized 1,8,15,22-tetraamino metal-Pcs. 1,8,15,22-Tetraamino metal-Pc complexes of Co, Ni, Cu, Ce, and Er were obtained by reducing 1,8,15,22-tetranitro metal-Pc complexes synthesized from 3-nitrophthalic anhydride, urea, metal salt, and ammonium molybdate catalyst. Complexes and polymers were characterized by Fourier transform infrared (FTIR), ultraviolet,visible (UV,vis), and X-ray powder diffraction spectroscopes. X-ray analysis of the polymers showed that there were short-range orientations in the polymers. Thermal analysis of the complexes and the polymers were done by differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA) at a heating rate of 10°C min,1 under nitrogen atmosphere. Ash analysis was performed to determine the metal content of the polymers. Viscosimetry and ebullioscopy measurements of the soluble part of the polymers were done for molecular weight analysis of the soluble part in tetrahydrofuran (THF) at 25°C. Four-probe conductivity measurements on isothermal conditions revealed that the polymer samples showed 104 fold increases in their electrical conductivities when doped with iodine. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source]

Development of an efficient route to hyperbranched poly(arylene ether sulfone)s

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2005
Patrick Himmelberg
Abstract A two-step route to an AB2 monomer that underwent polymerization via nucleophilic aromatic substitution to afford hyperbranched poly(arylene ether sulfone)s (HB PAES) was developed. The synthesis of 3,5-difluoro-4,-hydroxydiphenyl sulfone (4) was accomplished by the reaction of 3,5-difluorophenylmagnesium bromide with 4-methoxyphenylsulfonyl chloride, followed by deprotection of the phenol group with HBr in acetic acid. The polymerization of 4 in the presence of 3,4,5-trifluorophenylsulfonyl benzene or tris(3,4,5-trifluorophenyl)phosphine oxide as a core molecule afforded HB PAES with number-average molecular weights ranging from 3400 to 8400 Da and polydispersity index values ranging from 1.5 to 4.8. The presence of cyclic oligomeric species, formed by an intramolecular cyclization process, was a contributing factor to the relatively low molecular weights. The degree of branching (DB) of the HB PAES samples was estimated by a comparison of the 19F NMR spectra of the polymer samples with those of a series of model compounds, and DB values ranging from 0.51 to 0.70 were determined. The glass-transition temperatures for the HB PAES samples were in the range of 205,222 °C, as determined by differential scanning calorimetry. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43:3178,3187, 2005 [source]

Poly[1-(trimethylgermyl)-1-propyne] and poly[1-(trimethylsilyl)-1-propyne] with various geometries: Their synthesis and properties

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2003
V. S. Khotimsky
Abstract The polymerization of 1,2-disubstituted acetylenes [1-(trimethylgermyl)-1-propyne and 1-(trimethylsilyl)-1-propyne] initiated by Nb- and Ta-based catalytic systems was studied within a wide temperature range (,10 to +80 °C) with solvents (cyclohexane, CCl4, toluene, anisol, and n -chlorobutane) with variable dielectric constants (2.023,7.390). Conditions ensuring the synthesis of poly[1-(trimethylsilyl)-1-propyne] (PTMSP) containing 20,80% cis units and poly[1-(trimethylgermyl)-1-propyne] (PTMGP) containing 3,65% cis units were determined. The PTMSP and PTMGP samples were amorphous, exhibited a two-phase structure characterized by the presence of less ordered regions and regions with an enhanced level of ordering, and differed in solubility. A correlation was found between the cis/trans ratio and the morphology, the geometrical density of PTMSP and PTMGP films, and the gas permeability of the polymers. The gas permeability and solubility behavior of PTMSP and PTMGP were examined in terms of the molecular characteristics of the polymer samples (the thermodynamic Kuhn segment and the Kerr electrooptic effect). It was demonstrated that the gas permeability, as well as the solubility of the polymers, was defined by their supramolecular ordering, which depended on the lengths of continuous sequences composed of units of analogous microstructures and on the flexibility of macrochains. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2133,2155, 2003 [source]

In Vitro Degradation of Trimethylene Carbonate Based (Co)polymers

MACROMOLECULAR BIOSCIENCE, Issue 9 2002
Ana Paula Pêgo
Abstract Trimethylene carbonate (TMC) was copolymerized with D,L -lactide (DLLA) or with , -caprolactone (CL), and the degradation of melt-pressed solid copolymer films in phosphate-buffered saline at pH 7.4 and 37,°C was followed for a period of over two years. The parent homopolymers were used as reference materials. The degradation profile of TMC-DLLA- and TMC-CL based copolymers was similar and was best described by autocatalyzed bulk hydrolysis, preferentially of ester bonds. The hydrolysis rates varied by two orders of magnitude, depending on polymer composition and physical characteristics under the degradation conditions. TMC-DLLA copolymers degraded faster than the parent homopolymers. The copolymers lost their tensile strength in less than five months, after which mass loss occurred. Copolymers with 50 or 80 mol-% of TMC underwent total degradation in eleven months. For TMC-CL copolymers, a slow and gradual decrease in molecular weight and deterioration of the mechanical performance was observed. These copolymers maintained suitable mechanical properties for seventeen months or longer. Chain scission in the semicrystalline copolymers resulted in an increase in crystallinity. In comparison with the CL homopolymer, the introduction of a small amount of TMC (10 mol-%) significantly reduced the increase in crystallinity during degradation. Poly(TMC) specimens were dimensionally stable and showed a negligible decrease in molecular weight. A 60% decrease in the initial tensile strength of the polymer samples was observed after two years. [source]

Morphological and Physical Properties of Triblock Copolymers of Methyl Methacrylate and 2-Ethylhexyl Methacrylate

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 9 2006
Hormoz Eslami
Abstract Summary: Triblock copolymers of methyl methacrylate (MMA) and 2-ethylhexyl methacrylate (EHMA) [that is, poly(MMA,EHMA,MMA)] were prepared by an emulsion atom-transfer radical polymerization. The relationships of their structural, morphological, and physical properties were investigated. The latex particles had core-shell morphologies and the block copolymers experienced phase separation. Small latex particles with a low number of cores could deform and wet silicon-wafer surfaces, but the deformation of large latex particles was restricted by the internal two-phase morphology of the particles. Latex casting produced continuous pinhole-free films, in which hard poly(MMA) (PMMA) cores of different latex particles merged and provided interparticle connections. The morphology of solution-cast films depended on block composition, solvent type, and film thickness. For all the prepared polymer samples, thick films cast in toluene had poly(EHMA) (PEHMA) materials at air surface, whereas those cast in tetrahydrofuran had a sponge-like PMMA surface structure. Thin toluene-cast films from P(MMA,EHMA,MMA) with the block degrees of polymerization () 200,930,200 showed spherical PMMA domains and those from 380,930,380 yielded a protruded worm-like PMMA structure. The copolymer materials were coated on a glass surface for peeling tests. The films gave good hot-melt adhesion properties when the of the PEHMA block was over 600. The peeling strength depended on the lengths of both PEHMA and PMMA blocks. The P(MMA,EHMA,MMA) sample with of 310,930,310 yielded the highest peeling strength of 7.4 kgf,·,inch,1. The developed material is demonstrated to be a good candidate for a solvent-free, hot-melt, pressure-sensitive adhesives for special-purpose applications such as medical tapes and labels. [source]

Sorption and Diffusion of Propylene and Ethylene in Heterophasic Polypropylene Copolymers

MACROMOLECULAR SYMPOSIA, Issue 1 2007
Michael Bartke
Abstract Summary: Sorption experiments of ethylene and propylene in different polypropylene powder samples, both homopolymer and heterophasic copolymers with different rubber content, have been carried out in a high-pressure magnetic suspension balance at 10 bars pressure and 70,°C. The gross solubilities measured can be well correlated with the rubber content of the polymer samples. Solubility of ethylene and propylene in the rubber phase differ from solubility in the amorphous fraction of the homopolymer, especially the concentration ratio of propylene to ethylene differs significantly between rubber phase and amorphous fraction of the homopolymer. From the slope of monomer uptake, information on kinetics of mass-transfer can be gained. No significant differences were observed in terms of mass-transfer for ethylene and propylene. With increasing rubber content, effective diffusion coefficients increased slightly. By combined sorption studies with powder samples and compressed films, information about both effective diffusion coefficients and the effective length scale of diffusion could be gained. It could be shown, that the particle radius is not the characteristic length of diffusion in the studied powder samples. Mass transfer of nearly all samples could be described by a constant diffusion length of 120 to 130 µm, independently on particle size. This indicates that the effective scale of diffusion in polymer particles is in between microparticle and macroparticle scale used in classical particle modeling. [source]

Real-life applications of the MULVADO software package for processing DOSY NMR data

MAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2006
R. Huo
Abstract MULVADO is a newly developed software package for DOSY NMR data processing, based on multivariate curve resolution (MCR), one of the principal multivariate methods for processing DOSY data. This paper will evaluate this software package by using real-life data of materials used in the printing industry: two data sets from the same ink sample but of different quality. Also a sample of an organic photoconductor and a toner sample are analysed. Compared with the routine DOSY output from monoexponential fitting, one of the single channel algorithms in the commercial Bruker software, MULVADO provides several advantages. The key advantage of MCR is that it overcomes the fluctuation problem (non-consistent diffusion coefficient of the same component). The combination of non-linear regression (NLR) and MCR can yield more accurate resolution of a complex mixture. In addition, the data pre-processing techniques in MULVADO minimise the negative effects of experimental artefacts on the results of the data. In this paper, the challenges for analysing polymer samples and other more complex samples will also be discussed. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Cluster secondary ion mass spectrometry of polymers and related materials,

MASS SPECTROMETRY REVIEWS, Issue 2 2010
Christine M. Mahoney
Abstract Cluster secondary ion mass spectrometry (cluster SIMS) has played a critical role in the characterization of polymeric materials over the last decade, allowing for the ability to obtain spatially resolved surface and in-depth molecular information from many polymer systems. With the advent of new molecular sources such as , , , and , there are considerable increases in secondary ion signal as compared to more conventional atomic beams (Ar+, Cs+, or Ga+). In addition, compositional depth profiling in organic and polymeric systems is now feasible, without the rapid signal decay that is typically observed under atomic bombardment. The premise behind the success of cluster SIMS is that compared to atomic beams, polyatomic beams tend to cause surface-localized damage with rapid sputter removal rates, resulting in a system at equilibrium, where the damage created is rapidly removed before it can accumulate. Though this may be partly true, there are actually much more complex chemistries occurring under polyatomic bombardment of organic and polymeric materials, which need to be considered and discussed to better understand and define the important parameters for successful depth profiling. The following presents a review of the current literature on polymer analysis using cluster beams. This review will focus on the surface and in-depth characterization of polymer samples with cluster sources, but will also discuss the characterization of other relevant organic materials, and basic polymer radiation chemistry. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 29:247,293, 2010 [source]

Planar aqueous electrode technique for polymer impedance spectroscopy

Shear stress nucleation in microcellular foaming process

POLYMER ENGINEERING & SCIENCE, Issue 6 2002
Lee Chen
The effect of shear stress on the foaming process has been studied using the Foaming Process Simulator developed previously. The polymer samples were saturated with gas in the test chamber. A rotor was used to apply shear stress to the polymer samples. Foams were obtained by releasing the pressure quickly. Polystyrene, filled and unfilled, was used as the material. The cell density was analyzed with a scanning electron microscope. It was found that the cell density was significantly increased by introducing shear stress. The higher the shear stress, the more significant the effect. A cell stretch model has been developed to explain the cell nucleation enhancement with shear stress. The nucleation sites are stretched under the shear stress. The stretched nuclei are much easier to expand for cell formation owing to their larger surface areas and non-spherical shapes. The model prediction shows the same tendency of the effect of shear stress observed in the experiment. The key issue with shear stress nucleation is the transformation of mechanical shear energy into surface energy. [source]

Nanostructuring polymers with cyclodextrins,

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 2-3 2005
Cristian C. Rusa
Abstract Bulk solid polymer samples formed by the coalescence of guest polymer chains from their inclusion compounds (ICs) formed with host cyclodextrins (CDs) can result in significant reorganization of their phase structures, morphologies, and even chain conformations from those more commonly produced from randomly-coiled, entangled polymer solutions and melts. When the cyclic host CDs are threaded by polymer chains to form crystalline polymer-CD-ICs, the guest polymers become highly extended due to the narrow host CD diameters (,5, 7, and 9 Å for , -, , -, and , -CDs) and are segregated from neighboring guest polymer chains by the CD-IC channel walls. As a consequence, when polymer-CD-IC crystals are treated with CD solvents that do not dissolve the guest polymers or are treated with amylase enzymes, the resulting coalesced bulk polymer samples often display properties distinct from those of normally produced bulk samples of the same polymers. In this article the CD-IC processing of polymers to generate novel polymer microstructures and morphologies are described, to control the phase separation of immiscible blocks in block copolymers, and to form well-mixed intimate blends of two or more polymers that are normally incompatible. The thermal and temporal stabilities of polymer samples coalesced from their ICs formed with CDs will also be mentioned, and it is suggested that the range of polymer properties can be greatly expanded by their CD-IC processing. Copyright © 2005 John Wiley & Sons, Ltd. [source]