pinecone/core-2020-05-10-deduplication huggingface dataset:
Surface modification of calcium carbonates studied by inverse gas chromatography and the effect on mechanical properties of filled polypropylene

Inverse gas chromatography (IGC) has been used to characterize the surfaces of a pure calcitic calcium carbonate as well as samples that had been treated with sodium polyacrylate and/or stearic acid. The dispersive components of the surface free energy for the pure material agreed well with related literature data. Polar contributions to the surface interactions with a range of probes were determined. The results show that-the surface treatments reduced the polarities of the surfaces and that modification with stearic acid produced a non-polar, low-energy surface. Some mechanical properties of the polypropylene composites containing the modified calcium carbonates were found to correlate well with the filler surface energies
Mechanical and dynamic mechanical properties of nylon 66/montmorillonite nanocomposites fabricated by melt compounding

Nylon 66 nanocomposites were prepared by melt compounding of nylon 66 with organically modified montmorillonite (MMT). The organic MMT was pre-modified with about 14 wt% of ammonium surfactant, much lower than the 35-46 wt% in most commercial organic MMT powders. Transmission electron microscope observation indicated that the MMT layers were well exfoliated in nylon 66 matrix.\ud
Dynamic mechanical analysis confirmed the constraint effect of exfoliated MMT layers on nylon 66 chains, which benefited the increased storage modulus, increased glass transition temperature and reduced magnitude of alpha relaxation peak. The effects of organic MMT loading levels on reinforcement and fracture behaviour of the nanocomposites were evaluated using tensile and three-point bending tests.\ud
The addition of the organic MMT clearly increased Young’s modulus and tensile strength but decreased ductility and fracture toughness of nylon 66
Green composites of organic materials and recycled post-consumer polyethylene

Addition of organic fillers to post‐consumer recycled plastics can give rise to several advantages. First of all, the cost of these fillers is usually very low, the organic fillers are biodegradable contributing to an improved environmental impact and, last but not least, some mechanical and thermomechanical properties can be enhanced. Organic fillers are not widely used in the plastic industry although their use is increasing. Bad dispersion into the polymer matrix at high‐level content and poor adhesion with the matrix are the more important obstacles to this approach. In this work various organic fillers have been used with a post‐consumer plastic material originating from films for greenhouses. The properties of these green composites have been compared with those of materials filled with a conventional inorganic filler. The organic fillers cause slightly worse processability, due to an increase of viscosity, an enhancement of the rigidity and of the thermomechanical resistance similar to that measured for the inorganic filler, while a reduction of the impact strength is observed. Copyright © 2004 Society of Chemical Industry
Preparation of aqueous anionic poly(urethane-urea) dispersions. Influence of the structure and molecular weight of the macrodiol on the dispersion and polymer properties

Aqueous poly(urethane‐urea) dispersions were prepared by the prepolymer mixing technique, without any organic solvent, using two aliphatic diisocyanates (α,α,α′,α′‐tetramethyl‐1,3‐xylylene diisocyanate and isophorone diisocyanate) and various macrodiols, in conjunction with a fixed proportion of emulsifying agent (dimethylol propionic acid, neutralised with triethylamine) and the same chain extender (1,2‐ethylene diamine). The properties of both the dispersions and the dried polymer films were characterised as a function of the two main parameters studied in this investigation, viz the structure of the macrodiols and their molecular weight, in order to establish criteria leading to optimised performances in terms of dispersion stability, particle size, and polymer film properties
Methacryloxyethyl phosphate-grafted expanded polytetrafluoroethylene membranes for biomedical applications

Expanded Poly (tetrafluoroethylene) (ePTFE) membranes were modified by graft copolymerization with methacryloxyethyl phosphate (MOEP) in methanol and 2-butanone (also known as methyl ethyl ketone MEK) at ambient temperature using gamma irradiation.  The effect of dose rate (0.46 and 4.6 kGy/h), monomer concentration (1-40%) and solvent were studied and the modified membranes were characterised by weight increase, X-ray photoelectron spectroscopy (XPS), Fourier Transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). XPS was used to determine the % degree of surface coverage using the C-F (ePTFE membrane) and the C-C (MOEP graft-copolymer) peaks. Grafting yield as well as surface coverage were found to increase with increasing monomer concentration and were significantly higher for samples grafted in MEK than in methanol solution. SEM images showed distinctly different surface morphologies for the membranes grafted in methanol (smooth) and MEK (globular) indicating phase separation of the homopolymer in MEK. We propose that in our system, the non-solvent properties of MEK for the homopolymer play a more important role than solvent chain transfer reactions in determining grafting outcomes
Vapour sorption studies of polymer-solution thermodynamics using a piezoelectric quartz crystal microbalance

A quartz crystal microbalance was used as the basis of a vapour sorption apparatus to measure thermodynamic interaction parameters of polystyrene, poly(4-chlorostyrene) and poly(methyl methacrylate) with a number of solvents. The apparatus was shown to give rapid and reliable results by comparison with literature results for poly(dimethyl siloxane). Measurements of activity coefficients and Flory-Huggins interaction parameters were correlated with the solution behaviour of the components and revealed some hitherto unreported effects of the solution concentration in polar systems
Characterisation of enzymatically oxidised lignosulfonates and their application on lignocellulosic fabrics

The ‘double function’ of laccase, from the ascomycete Myceliophthora, to depolymerise/polymerise lignin was studied in this work. A lignosulfonate (LS) compound was oxidised by enzymatic action and several techniques were applied to measure the polymeric changes obtained. This study was focused on the attachment level of the oxidised LS at the flax surface.

RESULTS: Modified solutions were studied in terms of surface charge. Zeta potential values obtained showed an increase of polymerisation after several days of incubation. The change in molecular weight after LS polymerisation was detected using gel permeation chromatography. An increase of 1700 Da was achieved. Fourier transform infrared and UV-visible spectroscopy techniques were applied and the results showed an increase of the degree of polymerisation. The colour strength of flax fabrics incubated with oxidised LS solutions was also measured and an increase of K/S (K, absorption coefficient; S, scattering coefficient) after enzymatic oxidation was observed.

CONCLUSION: The oxidised lignin products obtained show good potential for use in natural surface modification of textile materials containing flavonoids. These findings have important practical implications for lignocellulosic fibre coloration, where new polymers can replace harsh chemicals in the textile industry. Copyright © 2009 Society of Chemical Industr
Polymeric coatings for photostability enhancement of poly(p-phenylene vinylene) derivative films

Poly(p-phenylene vinylene) (PPV) derivatives are an important class of conjugated polymers, known for their applications as electroluminescent materials for light-emitting devices and sensors. These derivatives are highly susceptible to photodegradation by the combined action of oxygen and light. Here, the use of various commercial polymers as protective coatings against the photodegradation of PPV derivatives was explored. Cast films of two similar PPV derivatives, poly[(2-methoxy-5-n-hexyloxy)-p-phenylene vinylene] and poly[2-methoxy-5-(2-ethylhexyloxy)-p-phenylene vinylene], were submitted to photodegradation by exposure to white light under atmospheric conditions in order to verify if the type of side chain (linear or branched) had an effect on the photodegradation. No significant differences in the photodegradation behaviour between the two polymers were noticed. The following commercial polymers were tested as protective coatings for the PPV derivative cast films: 99 and 80% hydrolysed poly(vinyl alcohol) (PVA) and starch. The best results were achieved using coatings of 99% hydrolysed PVA, which increased about 700 times the time necessary for complete degradation of the PPV derivative films. The results show the effectiveness of this coating in minimizing and, possibly, controlling the effects of the photodegradation of PPV derivative films, which can be useful in many applications, e.g. oxygen sensors.FAPESPCNPqInstituto Multidisciplinar de Materiais Poliméricos (IMMP)/MCT
An electrospun polycaprolactone–collagen\ud
membrane for the resurfacing of cartilage\ud
defects

A polycaprolactone (PCL)–collagen electrospun mesh is proposed as a novel alternative to the conventional periosteal graft in\ud
autologous chondrocyte implantation. This is the first known attempt in designing a cartilage resurfacing membrane using a\ud
mechanically resilient PCL mesh with a weight-average molecular weight of 139 300 that is enhanced with bioactive collagen.\ud
PCL–collagen 10, 20 and 40% electrospun meshes (Coll-10, Coll-20 and Coll-40) were evaluated and it was discovered that\ud
the retention of surface collagen could only be achieved in Coll-20 and Coll-40. Furthermore Coll-20 was stiffer and stronger\ud
than Coll-40 and it satisfied the mechanical demands at the cartilage implant site. When seeded with mesenchymal stem cells\ud
(MSCs), the cells adhered on the surface of the Coll-20 mesh and they remained viable over a period of 28 days; however, they\ud
were unable to infiltrate through the dense meshwork. Cell compatibility was also noted in the chondrogenic environment as\ud
the MSCs differentiated into chondrocytes with the expression of Sox9, aggrecan and collagen II. More importantly, the mesh\ud
did not induce a hypertrophic response from the cells. The current findings support the use of Coll-20 as a cartilage patch, and\ud
future implantation studies are anticipated
Recent advances in Solid-State Organic Lasers

Review paperInternational audienceOrganic solid-state lasers are reviewed, with a special emphasis on works published during the last decade. Referring originally to dyes in solid-state polymeric matrices, organic lasers also include the rich family of organic semiconductors, paced by the rapid development of organic light emitting diodes. Organic lasers are broadly tunable coherent sources are potentially compact, convenient and manufactured at low-costs. In this review, we describe the basic photophysics of the materials used as gain media in organic lasers with a specific look at the distinctive feature of dyes and semiconductors. We also outline the laser architectures used in state-of-the-art organic lasers and the performances of these devices with regard to output power, lifetime, and beam quality. A survey of the recent trends in the field is given, highlighting the latest developments in terms of wavelength coverage, wavelength agility, efficiency and compactness, or towards integrated low-cost sources, with a special focus on the great challenges remaining for achieving direct electrical pumping. Finally, we discuss the very recent demonstration of new kinds of organic lasers based on polaritons or surface plasmons, which open new and very promising routes in the field of organic nanophotonics
Investigation of polymerization of benzoxazines and thermal degradation characteristics of polybenzoxazines via direct prolysis mass spectrometry

Cataloged from PDF version of article.Polymerization of benzoxazines and thermal degradation mechanisms of polybenzoxazines were investigated using the direct pyrolysis mass spectrometry (DP-MS) technique. The benzoxazine structures were based on phenol and aniline and on bisphenol-A and methylamine or aniline. Polymerizations of the benzoxazines were carried out by curing them at elevated temperatures without addition of initiator or catalyst. DP-MS data showed the presence of chains generated by opposing polymerization reaction pathways indicating quite complex structures for the polybenzoxazines under investigation. Thermal decomposition of polybenzoxazines was started by the cleavage of methylamine or aniline linkages. It was determined that polybenzoxazines based on phenol were more stable than the corresponding bisphenol-A-based polybenzoxazines, while those based on methylamine were more stable than the corresponding polybenzoxazines incorporating aniline. Thus, it can be concluded that the presence of bulky groups decreased the extent of crosslinking which in return decreased the thermal stability. © 2012 Society of Chemical Industry
A facile synthesis of mixed soft-segmented poly(urethane-imide)-polyhedral oligomeric silsesquioxone hybrid nanocomposites and study of their structure-transport properties

The structure–transport properties of mixed soft-segmented poly(urethane-imide) (MSPUI) membranes and their
microstructures were investigated. Polypropylene glycol, polycaprolactone diol and bis(3-aminopropyl)-terminated
polydimethylsiloxane were used as the soft segments in the membrane synthesis via a three-step polymerization reaction.
The chemical structures of the MSPUI membranes were characterized using attenuated total reflectance Fourier transform
infrared spectroscopy. Morphology and surface properties of the membranes were studied using scanning electron and
atomic force microscopy techniques. Surface energy measurements indicated the enrichment of the hydrophobic soft segment
in the membranes. The amorphous nature of the polymers was analysed using wide-angle X-ray diffraction. The effect
of morphology on the permeability and selectivity of the membranes is discussed. Finally, membrane structure–transport
property relationships were correlated.Department of Science and Technology, New Delhi (no. SR/S1/PC-45/2011). The CSIRhttp://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1097-0126hb201
Polymer opals as novel photonic materials

Synthetic opals, based on self-assembled arrays of core-shell (bead/matrix) polymer microparticles, are a promising platform for next generation bulk-scale photonic structures, coatings, fibres and sensors. This perspective article highlights recent work in this area, ranging from characterization and application, to advances in more fundamental understanding of structural color effects. These advances include visco-elastically-tuned symmetry breaking, the observation of anisotropic optical scattering, and the study of polymer opals as an analogue to the intrinsically disordered, low refractive-index contrast systems associated with opals seen in nature.authorsversionPeer reviewe
Examining the preparation and characterization of coatings based on linear aromatic terpoly(methoxy-cyanurate-thiocyanurate)s

Two series of terpoly(methoxy-cyanurate-thiocyanurate)s based on thiodiphenol and dithiodiphenyl sulphide, and dihydroxydiphenylether and dithiodiphenyl ether, are prepared in good yield and purity, and fully characterised. Most of the resulting polymers, formed at room temperature using phase transfer catalysis, can be cast into films with good resilience and thermal stability. Two series of terpoly(methoxy-cyanurate-thiocyanurate)s based on thiodiphenol and dithiodiphenyl sulfide and on dihydroxydiphenyl ether and dithiodiphenyl ether, were prepared in good yield and purity and fully characterized. Most of the resulting polymers, formed at room temperature using phase transfer catalysis, can be cast into films with good resilience and thermal stability (some examples suffer practically no mass loss when held isothermally at 190 °C and only display appreciable losses when held continuously at 225 °C). Char yields of 53%-61% are achieved in nitrogen depending on backbone structure. Some problems were encountered with solubility, particularly with copolymers, which limited molecular weight analysis, but values of Mn = 8000-13000 g mol-1 were obtained for the polymers based on thiodiphenol and dithiodiphenyl sulfide, and Mn = 5000-13000 g mol-1 for the polymers based on dihydroxydiphenyl ether and dithiodiphenyl ether. DSC reveals polymerization exotherms with maxima at 184-207 °C (ΔHp = 43-59 kJ mol-1), which are believed to be due to isomerization of the cyanurate to the isocyanurate (activation energies span 159-195 kJ mol-1). Molecular simulation shows that diphenylether and diphenylsulfide display very similar conformational energy surfaces and would therefore be expected to adopt similar conformations, but the diphenylsulfide offers less resistance to deformations that increase the proximity of the two phenyl rings and results in more resilient films. © 2013 Society of Chemical Industry
Biopolymer nanocomposites based on poly(hydroxybutyrate-co-hydroxyvalerate) reinforced by a nonionic organoclay

International audienceIn this study, a nanocomposite based on a biodegradable polymer poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) reinforced by triethylene glycol mono-n-decyl ether (C10E3) nonionic organoclay (C10E3-Mt) was prepared. The morphology and the thermal and mechanical properties of PHBV/C10E3-Mt were compared with those of PHBV nanocomposites prepared using commercial organically modified montmorillonite Cloisite® 30B (OMt) and raw montmorillonite (Mt). Nanocomposites with 3 wt % nanoparticles were obtained by melt processing. The high level of dispersion with improved interfacial interactions between OMt and polymer led to an increase in the thermal stability and modulus of PHBV. However, this nanocomposite presented a lower strain before fracture, typical of brittle behavior. The transmission electron microscopy (TEM) and wide angle X-ray diffraction (WAXD) results revealed a significant increase in the interlayer spacing of clay for the PHBV/C10E3-Mt nanocomposite, which was favored by the wide expansion of the platelets of the starting nonionic organoclay. This characteristic of C10E3-Mt, together with its hydrophobic behavior, allowed its easy incorporation in the PHBV matrix, thus improving the processing and maintaining a high modulus with increased material toughness
Non-toxic luminescent carbon dot/poly(dimethylacrylamide) nanocomposite reagent for latent fingermark detection synthesized via surface initiated reversible addition fragmentation chain transfer polymerization

Here, non-toxic luminescent carbon nanoparticles, namely carbon dots (C-dots), were facilely synthesized via a one-pot hydrothermal route. Raman, Fourier transform infrared, fluorescence, carbon NMR and X-ray photoelectron spectroscopies revealed that the C-dots possessed a graphitic-like core with an oxidized surface. The oxidized surface of the C-dots allowed for functionalization of the C-dots with a 2-methyl-2-[(dodecylsulfanylthiocarbonyl)sulfanyl]propanoic acid chain transfer agent. Poly(N,N-dimethylacrylamide) (p(DMA)) was then grafted from the C-dot surface via surface initiated reversible addition fragmentation chain transfer (RAFT) polymerization. The resulting luminescent C-dot/polymer nanocomposite, C-dot/p(DMA), was analyzed using UV−visible and fluorescence spectrometry verifying that the functionalized surface was responsible for the C-dots' luminescence. This C-dot/p(DMA) nanocomposite was water soluble and was used as a solution for the luminescent detection of latent fingermarks deposited on non-porous aluminium foil substrates
Small and large scale segmental motion in polymers: Estimating cooperativity length by ordinary relaxation experiments

We derive a suitable expression for estimating the size of the cooperatively rearranging regions (CRRs) in supercooled polymer melts by fitting data worked out by ordinary relaxation experiments carried out in isothermal conditions. As an example, the average CRR size in poly(n-butyl methacrylate) in proximity to the glass transition temperature is derived from a stress relaxation experiment performed by means of an atomic force microscopy setup. Good agreement is found with results in the literature derived from measurements of temperature fluctuations (the so-called Donth method). The temperature dependence of the CRR size is explored for poly(butadiene); in this case the segmental relaxation function is derived through a novel method for the analysis of the efficiency with which free induction decay echoes are refocused in 1H NMR experiments. It is found that the CRR size increases upon cooling. The results derived from the analysis of the NMR data are found to be in satisfactory agreement with those worked out from broadband dielectric spectroscopy data in the literatur
Yield stress distribution in injection-mouldedglassy polymers

A methodology for structural analysis simulations is presented that incorporates the distribution of mechanical propertiesalong the geometrical dimensions of injection-moulded amorphous polymer products. It is based on a previously developedmodelling approach, where the thermomechanical history experienced during processing was used to determine the yield stressat the end of an injection-moulding cycle. Comparison between experimental data and simulation results showed an excellentquantitative agreement, both for short-term tensile tests as well as long-term creep experiments over a range of strain rates,applied stresses, and testing temperatures. Changes in mould temperature and component wall thickness, which directly aﬀectthe cooling proﬁles and, hence, the mechanical properties, were well captured by the methodology presented. Furthermore, itturns out that the distribution of the yield stress along a tensile bar is one of the triggers for the onset of the (strong) localizationgenerally observed in experiments.Spanish Government (Ministry of Sci-ence and Innovation, Ministry of Economy and Competitiveness)through grant numbers RYC-2010-07171 and DPI2011-25470This is the peer reviewed version of the following article: Verbeeten, W. M., Kanters, M. J., Engels, T. A. and Govaert, L. E. (2015), Yield stress distribution in\ud
injection-moulded glassy polymers. Polym. Int., 64(11): 1527–1536, which has been published in final form at http://dx.doi.org/10.1002/pi.4898. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archivin
Microwave-crosslinked Bio-based Starch/Clay aerogels

Foam-like robust starch/sodium montmorillonite (Na+-MMT) aerogels were fabricated through a freeze-drying process. Glutaraldehyde (GL) was used to crosslink the starch aerogels with the assistance of radiation supplied by a domestic microwave oven. The chemical reaction between GL and starch was analysed using Fourier transform infrared spectroscopy and water swelling tests. The microstructures and mechanical properties of the resultant crosslinked starch aerogels changed with GL concentration. By incorporating 5% (w/w) GL, the specific compressive modulus and absorbed energy increased by 2.4 and 3.3 times, respectively. In regard to starch/clay aerogel composites, Na+-MMT clay played the role of reinforcement. Moreover, clay addition created more porous structures and hence decreased the thermal conductivity of the aerogels. The biodegradability of the aerogels was studied using a homemade micro-respirometer. The starch aerogels exhibited higher biodegradability than poly(vinyl alcohol)-based ones and their corresponding films.Peer ReviewedPostprint (author's final draft