Search results for "polymers"
showing 10 items of 3567 documents
Resource or waste? A perspective of plastics degradation in soil with a focus on end-of-life options.
2018
‘Capable-of-being-shaped’ synthetic compounds are prevailing today over horn, bone, leather, wood, stone, metal, glass, or ceramic in products that were previously left to natural materials. Plastic is, in fact, economical, simple, adaptable, and waterproof. Also, it is durable and resilient to natural degradation (although microbial species capable of degrading plastics do exist). In becoming a waste, plastic accumulation adversely affects ecosystems. The majority of plastic debris pollutes waters, accumulating in oceans. And, the behaviour and the quantity of plastic, which has become waste, are rather well documented in the water, in fact. This review collects existing information on pla…
Modification of EVOH copolymers with e-caprolactone: synthesis and compatibilization effects in PE/PVC blends
2001
Polyethylene-polycaprolactone graft copolymers with different chemical structures (i.e. different number and length of PCL grafts and molecular weight of PE backbone) were synthesized from various EVOH copolymers and e-caprolactone, using Aluminum isopropoxide as catalyst, and were tested for their compatibilizing capability in PE/PVC blends. PE and PCL segments in the graft copolymers were found completely immiscible, while PCL segments of the graft copolymers were found completely miscible with PVC. When graft copolymers were added to PE/PVC blends they proved to be good agents for the dispersion of PVC phase in the PE matrix. SEM showed also improved adhesion between the dispersed PVC ph…
Oxazoline functionalization of polyethylenes and their blends with polyamides and polyesters
2001
The compatibilization of blends of polyamide-6 (PA6) with linear low density polyethylene (LLDPE) and of poly(ethylene terephthalate) (PET) with high density polyethylene (HDPE), by functionalization of the polyethylenes with oxazoline groups was investigated. Chemical modification of LLDPE and HDPE was carried out by melt free radical grafting with ricinoloxazoline maleinate. Blends preparation was made either with a two-steps procedure comprising functionalization and blending, and in a single step in which the chemical modification of polyethylene with the oxazoline monomer was realized in situ, during blending. The characterization of the products was carried out by FTIR spectroscopy an…
Oxazoline-containing compatibilizers for polyamide/SAN and polyamide/ABS blends
2002
Polyamide (PA) and acrylonitrile/butadiene/styrene copolymer (ABS) may appear as a mixture in the recycled plastic stream. The incompatibility of these blends results in a blend with poor mechanical properties. The aim of this work is to partially convert the nitrile groups of the acrylonitrile/styrene copolymer (SAN) into oxazoline groups by reaction with aminoethanol (AE). Such modified SAN (SAN-m) can react with the amine or carboxylic acid end groups of PA, and therefore used as compatibilizers for blends of PA with ABS. SAN-m was found to reduce the SAN-domain size in the PA/SAN-blends. The initial acrylonitrile content of SAN-m had a strong influence on the degree of conversion into o…
Improving the efficiency of light-emitting diode based on a thiophene polymer containing a cyano group
2007
Abstract We report on the overall improvement of a single layer organic light-emitting diode device based on poly{[3-hethylthiophene]-co-3-[2-( p -cyano-phenoxy)ethyl]thiophene} or namely PTOPhCN. This polymer was recently developed by adding a cyano group as a side-chain substituent of the thiophenic backbone onto the main polymer chain and showed promising results for light-emitting diode devices. Using an improved device layout, bright red electroluminescence was obtained at 4 V and showed a luminance of about 400 cd/m 2 at 8 V with current densities in the order of 6000 A/m 2 .
On the nature of macroradicals formed upon radiolysis of aqueous poly(N-vinylpyrrolidone) solutions
2020
In this work we have explored the nature of macroradicals formed upon radiolysis of aqueous poly(N-vinylpyrrolidone) (PVP) solutions using pulse radiolysis, density functional theory (DFT) and literature data. On the basis of literature data on site-specific kinetics of hydrogen abstraction from simple amides and spectra corresponding to specific radical sites on the same amides we have assessed the distribution of H-atom abstraction by `OH radicals from different positions on the pyrrolidone ring and the polymer backbone. Pulse radiolysis experiments performed at different doses per pulse and different PVP concentrations demonstrate that the H-abstracting radiolysis products are not quanti…
Effect of high power ultrasound on physical–chemical properties of polypropylene films aimed for food packaging: structure and surface features
2019
International audience; Biaxially oriented polypropylene (BOPP) coated with acrylic/polyvinylidene chloride (BOPPAcPVDC) and biaxially oriented coextruded polypropylene (BOPPcoex) films have been treated with high power ultrasound (HPUS) while submerged in water. Polymer structure and the surface morphology changes were noticed, and obtained results were correlated with the physical properties of tested materials. In anticipation of sonochemically enhanced reactions, physical–chemical profile of film samples was determined using thermogravimetric analysis, differential scanning calorimetry, Fourier-transform infrared spectroscopy, UV spectrophotometry and environmental scanning electron mic…
P(HPMA)-block-P(LA) copolymers in paclitaxel formulations: Polylactide stereochemistry controls micellization, cellular uptake kinetics, intracellula…
2012
In order to explore the influence of polymer microstructure and stereochemistry in biological settings, the synthesis, micellization, cellular fate and the use in paclitaxel formulations of poly(N-(2-hydroxypropyl)-methacrylamide)-block-poly(L-lactide) (P(HPMA)-block-P(LLA)) and poly(N-(2-hydroxypropyl)-methacrylamide)-block-poly(DL-lactide) block copolymers (P(HPMA)-block-P(DLLA)) were studied. To this end, P(HPMA)-block-P(lactide) block copolymers and their fluorescently labeled analogues were synthesized. The polymers exhibited molecular weights M-n around 20,000 g/mol with dispersities (D=M-w/M-n) below 1.3. In addition, the solution conformation of this new type of partially degradable…
Unprecedented layered coordination polymers of dithiolene group 10 metals: Magnetic and electrical properties
2016
One-pot reactions between Ni(ii), Pd(ii) or Pt(ii) salts and 3,6-dichloro-1,2-benzenedithiol (HSC6H2Cl2SH) in KOH medium under argon lead to a series of bis-dithiolene coordination polymers. X-ray analysis shows the presence of a common square planar complex [M(SC6H2Cl2S)2]2- linked to potassium cations forming either a two-dimensional coordination polymer network for {[K2(μ-H2O)2(μ-thf)(thf)2][M(SC6H2Cl2S)2]}n [M = Ni (1) and Pd (2)] or a one-dimensional coordination polymer for {[K2(μ-H2O)2(thf)6][Pt(SC6H2Cl2S)2]}n (3). In 3 the coordination environment of the potassium ions may slightly change leading to the two-dimensional coordination polymer {[K2(μ-H2O)(μ-thf)2][Pt(SC6H2Cl2S)2]}n (4) …
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…