Search results for "plastics"
showing 10 items of 2724 documents
Characterisation of films and nanopaper obtained from cellulose synthesised by acetic acid bacteria
2016
Bacterial cellulose (BC) samples were obtained using two culture media (glucose and glucose+fructose) and two bacteria (Komagataeibacter rhaeticus and Komagataeibacter hansenii). Nanopaper was obtained from the BC through oxidation and both were studied to determine the impact of culture media and bacteria strain on nanofiber structure and mechanical properties. AFM and SEM were used to investigate fibre dimensions and network morphology; FTIR and XRD to determine cellulose purity and crystallinity; carboxyl content, degree of polymerisation and zeta potential were used to characterise nanofibers. Tensile testing showed that nanopaper has up to 24 times higher Young's modulus (7.39GPa) than…
Tracer aroma compound transfer from a solid and complex-flavored food matrix packed in treated papers or plastic packaging film.
2007
The objective of this work was to study the transfer of four aroma compounds (ethyl butyrate, ethyl hexanoate, cis-3-hexenol, and benzaldehyde) from a solid and complex-flavored food matrix (sponge cake) toward and through packaging films placed in indirect contact during storage in accelerated aging conditions (38 °C and 86% relative humidity gradient). The efficiency of treated papers relative to that of standard paper and plastic as barrier was tested. Before storage, aroma compound volatility in the sponge cake was measured, and similar values were found between aroma compounds, due to the fat content of the sponge cake. Whatever the aroma compound, permeability values during storage we…
Grafting of hyperbranched polymers: From unusual complex polymer topologies to multivalent surface functionalization
2013
Abstract In this feature article, the grafting of hyperbranched polymers to different substrates is reviewed. Both grafting onto macromolecules with different topologies (homogeneous grafting) and the resulting complex polymer architectures containing highly branched segments as well as their applications are discussed. In the second part grafting of hyperbranched polymers on surfaces, i.e., planar surfaces and spherical particles (heterogeneous grafting), with respect to specific applications, such as bio-repellent surfaces or soluble carbon nanotubes is described. In all cases, the one-step synthesis and the resulting highly branched topology of the hyperbranched building blocks is benefi…
Functional Adhesion of Pectin Biopolymers to the Lung Visceral Pleura
2021
Pleural injuries and the associated “air leak” are the most common complications after pulmonary surgery. Air leaks are the primary reason for prolonged chest tube use and increased hospital length of stay. Pectin, a plant-derived heteropolysaccharide, has been shown to be an air-tight sealant of pulmonary air leaks. Here, we investigate the morphologic and mechanical properties of pectin adhesion to the visceral pleural surface of the lung. After the application of high-methoxyl citrus pectin films to the murine lung, we used scanning electron microscopy to demonstrate intimate binding to the lung surface. To quantitatively assess pectin adhesion to the pleural surface, we used a custom ad…
Effect of a filler on the dielectric properties of an epoxy resin
1983
The effect of aluminum hydroxide upon the dielectric properties of an epoxy resin has been studied in a wide frequency and temperature range. An interfacial polarization effect, known as the Maxwell–Wagner–Sillars polarization is evidenced for the filled resin, which shows a higher permittivity, a higher dielectric loss, and a β transition with a larger relaxation time. The glass transition temperature is, on the contrary, mostly unaffected by the presence of the filler.
Noninvasive monitoring of polymer curing reactions by dielectrometry
2011
A microwave sensor system for the noninvasive monitoring of the curing process of a thermoset material placed inside a metallic mold is described. The microwave sensor is designed as an open-ended coaxial resonator with a curved surface adapted to the mold inner shape. The analysis of the microwave resonator comprises a recently developed method for deembedding the effect of coupling network in overcoupled resonators, so the range of permitted measurements encompass both low and high dielectric losses of polymeric materials. Results show that noninvasive, continuous monitoring of the microwave dielectric properties of the thermoset material can be performed in real time, allowing one to che…
Development and characterization of xyloglucan-poly(vinyl alcohol) hydrogel membrane for Wireless Smart wound dressings
2018
Abstract Hydrogel-based smart wound dressings that combine the traditional favourable properties of hydrogels as skin care materials with sensing functions of relevant biological parameters for the remote monitoring of wound healing are under development. In particular, lightweight, ultra-high frequency radiofrequency identification (UHF RFID) sensor are adjoined to xyloglucan-poly(vinyl alcohol) hydrogel films to battery-less monitor moisture level of the bandage in contact with the skin, as well as wireless transmit the measured data to an off-body reader. This study investigates the swelling behavior of the hydrogels in contact with simulated biological fluids, and the modification of th…
Interfaces in polymer blends
2000
We investigate the structure and thermodynamics of interfaces in dense polymer blends using Monte Carlo (MC) simulations and self-consistent field (SCF) calculations. For structurally symmetric blends we find quantitative agreement between the MC simulations and the SCF calculations for excess quantities of the interface (e.g., interfacial tension or enrichment of copolymers at the interface). However, a quantitative comparison between profiles across the interface in the MC simulations and the SCF calculations has to take due account of capillary waves. While the profiles in the SCF calculations correspond to intrinsic profiles of a perfectly flat interface the local interfacial position f…
Characteristic Length Scales and Radial Monomer Density Profiles of Molecular Bottle-Brushes: Simulation and Experiment
2010
Extensive Monte Carlo simulations are presented for bottle-brush polymers under good solvent conditions, using the bond fluctuation model on the simple cubic lattice. Varying the backbone length (from Nb = 67 to Nb = 259 effective monomers) as well as the side chain length (from N = 6 to N = 48), for a physically reasonable grafting density of one chain per backbone monomer, we find that the structure factor describing the total scattering from the bottle-brush provides an almost perfect match for some combinations of (Nb, N) to experimental data of Rathgeber et al. [J. Chem. Phys. 2005, 122, 124904], when we adjust the length scale of the simulation to reproduce the experimental gyration r…
Semiflexible Macromolecules with Discrete Bond Angles Confined in Nanoslits: A Monte Carlo Test of Scaling Concepts
2013
Single semiflexible polymer chains confined in a planar slit geometry between parallel nonadsorbing repulsive walls a distance D apart are studied by Monte Carlo simulations of a lattice model, for the case of good solvent conditions. The polymers are modeled as self-avoiding walks on the simple cubic lattice, where every 90° kink requires a bending energy eb. For small qb = exp(−eb/kBT) the model has a large persistence length lp (given by lp ≈ 1/(4qb) in the bulk three-dimensional dilute solution, in units of the lattice spacing). Unlike the popular Kratky–Porod model of worm-like chains, this model takes both excluded volume into account and approximates the fact that bond angles between…