V INTERNATIONAL CONFERENCE ON TIMES OF POLYMERS (TOP) AND COMPOSITES
1255(2010); http://dx.doi.org/10.1063/1.3455579View Description Hide Description
Studies of thermal and fire‐resistant properties of the polypropylene/multi‐walled carbon nanotube composites (PP/MWCNT) prepared by means of melt intercalation are discussed. The sets of the data acquired with the aid of non‐isothermal TG experiments have been treated by the model kinetic analysis. The thermal‐oxidative degradation behavior of PP/MWCNT and stabilizing effect caused by addition of MWCNT has been investigated by means of TGA and EPR spectroscopy.
The results of cone calorimetric tests lead to the conclusion that char formation plays a key role in the mechanism of flame retardation for nanocomposites. This could be explained by the specific antioxidant properties and high thermal conductivity of MWCNT which determine high‐performance carbonization during thermal degradation process.
Comparative analysis of the flammability characteristics for PP‐clay/MWCNT nanocomposites was provided in order to emphasize the specific behavior of the nanocomposites under high‐temperature tests.
Elasticity and Inelasticity of Hard‐Phase Reinforced Polyurethane Elastomers: From Sensitivity to Chemical and Physical Structure to Time Dependent Phenomena1255(2010); http://dx.doi.org/10.1063/1.3455661View Description Hide Description
A study was made of how aspects of the constitutive responses of polyurethane elastomers vary with composition: the hard segment, soft segment and chain extender were varied systematically in a family of 18 segmented copolyurethane elastomers. Results were related to microstructural changes, on the basis of evidence from x‐ray scattering (SAXS and WAXS). Inelastic effects were most pronounced when the hard segment crystallized, and when the phase segregation was least pronounced. Large variations were found in the responses to first loading to a given strain. Tensile modulus and work input increased significantly with degree of hard phase crystallinity, but were independent of degree of phase separation. First cycle hysteresis was found to increase with reduced phase separation. A quantitative correlation was found between the magnitude of the Mullins effect and the fractional energy dissipation by hysteresis under cyclic straining, giving a common relation that was approached by all the materials studied. The results provide new insight into the physical origin of inelastic effects in reinforced elastomers, to assist with the development of physically‐based constitutive models.
1255(2010); http://dx.doi.org/10.1063/1.3455672View Description Hide Description
This work deals with a study of stabilizers extraction by ethanol‐cyclohexane mixtures simulating ethanol based biofuels. It appears that the extractive power of cyclohexane is considerably stronger then ethanol one. In other words, from this point of view, ethanol based biofuels are less aggressive than a pure hydrocarbon.
1255(2010); http://dx.doi.org/10.1063/1.3455546View Description Hide Description
This article deals with degradation mechanism of three aromatic polymers submitted to γ‐rays in air at 60° C. measurements and GPC results indicated that thin samples (thickness lower than 200 μm) undergo mostly chain scission whereas sol gel analysis and rheometric measurements showed that thicker ones undergo mainly crosslinking. Both results are explained by oxygen diffusion control of oxidation resulting in the formation of a superficial oxidized layer experimentally observed by μATR InfraRed in which oxidative processes orientate rather to chain scission than crosslinking. Experimental results also allowed discussing relative oxidative stability, sensitivity of to chain scission concentration, and crosslinking mechanism (Y or H).
1255(2010); http://dx.doi.org/10.1063/1.3455557View Description Hide Description
For modern application in microoptics the refractive index of polymers can be adjusted in a certain range by the addition of electron‐rich organic dopants. As an unwanted side‐effect a pronounced plasticizing occurs. In this work the addition of a crosslinker (divinylbenzene) to the unsaturated polyester matrix, doped with phenanthrene for refractive index adjustment, allows for a successful suppression of the plasticizing effect measured after polymerization. Even at high phenanthrene concentrations the glass transition temperature of the initial polymer could be almost retained. An increase of the polymers refractive index from 1.5684 up to a value of 1.6425 could be achieved.
Multiblock polyurethanes in biomedical applications: fine tuning of degradation and biomimetic properties1255(2010); http://dx.doi.org/10.1063/1.3455567View Description Hide Description
Biodegradable and biostable soft segment based polyurethanes (PURs) were synthesized as new polymers for medical applications. Poly(ε‐caprolactone) (PCL) was chosen as macrodiol for biodegradable PURs for its biodegradability and biocompatibility properties. Polydimethylsiloxane (PDMS) and polytetramethylenoxide (PTMO) were selected as macrodiols for biostable PURs because of their high hydrolysis resistance. 1,6‐Diisocyanatohexane (HDI) was used as diisocyanate component producing non toxic metabolytes. 1,4‐Cyclohexane dimethanol (CDM), a peptide‐based diammine and a lysine ethyl ester with grafted RGD peptide sequence are the chain extenders. The latter shows biomimetic properties able to promote material cellular adhesion. Chemical and mechanical characterizations of the obtained polymers highlight their suitability for applications in the cardiovascular field.
1255(2010); http://dx.doi.org/10.1063/1.3455578View Description Hide Description
Cooling rate of semicrystalline thermoplastic (PEEK) based composite parts has been assessed by means of a thermal flow model. Cold tool thermoforming was found suitable for thin parts, but the use of a preheated tool is suggested. Cooling rate is critical for automated lay‐up; consequently the optimization of this technique requires the use of a complex apparatus, able to provide both heating of the part during lay‐up and a control of the cooling rate. Alternatively a modified cooling rate vs. crystallinity behavior of the material must be achieved.
1255(2010); http://dx.doi.org/10.1063/1.3455589View Description Hide Description
The interlaminar toughening of a carbon ‐fibre reinforced composite by incorporation of electrospun polyvinylidene fluoride (PVDF) nanofibrous membranes was explored in this work. The nanofibres were electrospun directly onto commercial pre‐impregnated carbon fibre materials under optimised conditions and PVDF was found to primarily crystallise in its β phase polymorphic form. There is strong evidence from DMTA analysis to suggest that a partial miscibility between the amorphous phases of the PVDF nanofibres and the epoxy exists. The improved plastic deformation at the crack tip after inclusion of the nanofibres was directly translated to a 57% increase in the mode II interlaminar fracture toughness (in‐plane shear failure). Conversely, the fracture toughness in mode I (opening failure) was slightly lower than the reference by approximately 20%, and the results were interpreted from the complex micromechanisms of failure arising from the changes in polymorphism of the PVDF.
1255(2010); http://dx.doi.org/10.1063/1.3455600View Description Hide Description
The effect of the resin/hardener ratio on the strain recovery kinetics of various post‐yield deformed epoxy resins is investigated in isothermal tests and in thermally stimulated recovery tests. Recovery is seen to take place following a two‐stage process, in which the different stages can be distinguished on the time and temperature scales. These two recovery contributions are differently affected by the resin/hardener ratio and by the applied deformation.
1255(2010); http://dx.doi.org/10.1063/1.3455611View Description Hide Description
Amphiphilic diblock and triblock copolymers were synthesized from poly(ethylene glycol) (PEG) and ‐Boc‐L‐tryptophan. A number of reaction conditions were investigated in order to achieve optimum yield and maximum chain extension for the newly formed block copolymers. Characterization of the novel copolymers was evaluated by means of 1D and 2D solution state nuclear magnetic resonance (NMR), infrared (IR) spectroscopy and size exclusion chromatography (SEC). The 2D NMR investigation of the block copolymers provided evidence to suggest that protonation of the nitrogen atoms present along the newly formed peptide back bone was occurring when the solvent environment was under acidic conditions.
Studying the effect of adsorbent dosage on the removal of Arsenic from aqueous solution by using polyaniline nanocomposite1255(2010); http://dx.doi.org/10.1063/1.3455622View Description Hide Description
In this study, the effect of dose of polymer on the removal of arsenic from aqueous solution by using polyaniline nanocomposite was studied. The conductive polyaniline was prepared using ammonium peroxy disulfate as an oxidant at room temperature. The results indicate that the polyaniline are able to remove arsenic from aqueous media. The chemical structure of obtained product was determined by FTIR spectroscopy.
1255(2010); http://dx.doi.org/10.1063/1.3455632View Description Hide Description
Electrospinning and Melt blowing are the most commonly used processes to produce microfibers from extruded polymer solution or melt. The present study deals with the dynamic modeling of the instabilities and related processes during producing microfibers. A bead‐viscoelastic element fiber model is employed in modeling three‐dimensional paths of the fiber whipping in the processes of electrosping and melt blowing. The mathematical model provides a reasonable representation of the previous published predicted and experimental data.
Computational Protocols for Viscoelastic Material Property Characterizations without the Use of Poisson’s Ratios1255(2010); http://dx.doi.org/10.1063/1.3455643View Description Hide Description
The objective of this work is to present the numerical implementation for the alternative determination of vis‐coelastic material properties without using Poisson’s ratios as presented in –. The presented method is based on the 3‐D generalized constitutive relations viscoelastic materials with hereditary integrals. The numerical procedures are based on experiments using photogrammetric and tensile testing instrumentation, which provide stress data in the 1‐D loaded direction and strains in both longitudinal (loaded) and transverse directions. Measurements and data analyses include both starting transient and steady‐state loading conditions. The paper presents the implementation of solutions for the linear case, where the relaxation time values are prescribed according to to the scheme presented in  and . Convergence of the Prony series representations is evaluated.
1255(2010); http://dx.doi.org/10.1063/1.3455653View Description Hide Description
The work described here, is aiming to the development of an optimum design for a spider die used for the extrusion of high density polyethylene (HDPE) tubes. For this purpose, a computational fluid dynamics (CFD) based model using the generalized Newtonian approach was employed, to investigate pressure drop, flow and temperature uniformity in the die.
In‐situ Monitoring of Polymer Crystallization by Polarization‐Sensitive Optical Coherence Tomography1255(2010); http://dx.doi.org/10.1063/1.3455658View Description Hide Description
The use of polarization‐sensitive optical coherence tomography for monitoring the progress of a classical shear experiment in a slit die leads to new insights in the mechanisms of polymer crystallization. For the first time it is possible to get both depth and time resolved information on the development of different layers as a result of the processing conditions. By additionally measuring the transmitted light the method is at the same time fully compatible to conventional birefringence measurements. Microscopic analysis of the extruded stripes completes the description of the crystallization process.
Virus Sorbents Based on Polyaniline Interpolymer Complexes, Composites and their Sorption Properties1255(2010); http://dx.doi.org/10.1063/1.3455659View Description Hide Description
Complexes between influenza viruses proteins and antibodies to them create the precipitation lines in polyaniline (PAn) films which were detected by polarization optical microscopy after coating the film from the top the eutectic mixture of nematic liquid crystals MBBA:EBBA. Polyaniline and it’s composites interact as sorbents with influenza human and bird viruses apart from antigenic properties of surface proteins as well as with bacteriophage T4‐D. The sorption of virions occurred in different solutions in the temperature range (8–25 ° C) during 15–60 min. After contact with sorbent the HA titers of influenza virus in solutions were decreased in 4 −2048 times. The immobilized influenza viruses were able to interact with homological antibodies from immune sera in solution.
1255(2010); http://dx.doi.org/10.1063/1.3455660View Description Hide Description
Membranes based on PVdF‐HFP have been prepared by solution‐casting methode. Lithium perchlorate and lithium trifluoromethane sulfonate were used as lithium salts, and ethylene carbonate and a mixture of ethylene and propylene carbonate (1:1 wt. %) as plasticizers. The ionic conductivity was determined by means of impedance spectroscopy. The Nyquist plot was fitted with a general equivalent circuit. The ionic conductivity increases to plastificizer content. The membrane consisting of 50 w% PVdF‐HFP, 35 w% and 15 w% has the highest conductivity with a value of at room temperature.
1255(2010); http://dx.doi.org/10.1063/1.3455662View Description Hide Description
The immobilization of an oligopeptide, mimicking the adhesion sequence of fibronectin, on the surface of polymer films prepared by electrospinning was investigated by XPS spectroscopy. Films of polycaprolactone (PCL) and poly(l‐lactide‐caprolactone) [P(LLA‐CL)] were prepared by electrospinning onto aluminium substrates. A modified adhesion peptide containing a photoreactive group was immobilized on the surface of the polymer nanofibers by incubation in peptide solution and subsequent UV irradiation. XPS analysis yield evidence of successful peptide immobilization on the polymer surface; the amount of immobilized peptide increases with the concentration of the mother solution.
1255(2010); http://dx.doi.org/10.1063/1.3455663View Description Hide Description
In this study, a comprehensive laboratory test on 100 mm diameter HDPE 100 polyethylene flexible pipe buried in quartz sand is described. The laboratory test was performed in a 40 mm thick plexiglass‐fronted test tank which replicated a classical trench section in field conditions. The polyethylene flexible pipe was positioned against the glass with its longitudinal axis perpendicular to the glass. This allowed direct observation of the backfill‐pipe interactions and pipe performance under surcharge loads. Three high definition photogrammetric cameras were taken photogrammetric images through the glass allowing the discrete measurement and image processing of the deformation patterns of the polyethelene pipe conduit during the pipe installation and incremental surcharge loading. Vertical loads were applied in increments of 10 kPa to 150 kPa using air pressure membranes. According to the test results, it is understood that the installation technique and backfill properties have an important effect on circumferential strains, performance and deformation characteristics of polyethelene HDPE pipe. It was also observed that close‐range image processing is a very simple and appropriate method for measuring three dimensional pipe deformations under various conditions.