1,720,974 research outputs found
Bio-based PA5.10 for Industrial Applications: Improvement of Barrier and Thermo-mechanical Properties with Rice Husk Ash and Nanoclay
Full text linkComposites consisting of renewable PA5.10 were obtained from melt compounding with a modified clay (CL) and/or a
by-product obtained from the combustion of rice husk (RHA). Two different industrialized lab-scale machines were used
to obtain the final shape: a film extrusion machine and an injection moulding apparatus. The industrial application requirements
for polyamides generally need good barrier properties and high thermo-mechanical strength. Considering the barrier
properties, the CL was able to decrease the oxygen permeability to less than half with respect to neat PA5.10. DMTA
demonstrated that the addition of RHA caused a consistent enhancement (+ 46 °C) in the heat deflection temperature (HDT)
compared to the neat PA5.10 matrix, increasing the possible areas of interest. Furthermore, the simultaneous presence of
RHA and CL provided the best result reaching an extraordinary HDT of 131 °C. A complete discussion taking into account
the morphology, crystallinity and filler-matrix adhesion evaluation was reported as well as comparison of performances with
other bio-PAs composites. These two fillers can therefore be used separated or together combined in PA5.10 for functional
purposes in a sustainable scenario
Layer-by-Layer nanostructured interphase produces mechanically strong and flame retardant bio-composites
No full textIn this manuscript, the Layer-by-Layer technique is used to modify the surface of flax fabrics using a quad-layer architecture (QL) prior to their assembly in polylactic acid biocomposites. The aim is to produce nanostructured interphases capable of conferring flame retardancy while maintaining mechanical properties. Only 2.5 QL significantly improve the flame retardancy and fire safety of the prepared composites as demonstrated by LOI values of 25.3%, considerably reduced flame spread rates and the substantial reduction in peak of heat release rate (−33%) and maximum average rate of heat emission (−30%) during cone calorimetry. Mechanical testing showed improved modulus and limited reductions in flexural strength. These results make the approach developed in this manuscript very attractive in the design of advanced biocomposites with optimized fire retardancy and mechanical properties
Is it possible to mechanical recycle the materials of the disposable filtering masks?
Full text linkIn a singular period, such as during a pandemic, the use of personal protective masks can become mandatory for all citizens in many places worldwide. The most used device is the disposable mask that, inevitably, generates a substantial waste flow to send to incineration or landfill. The article examines the most diffused type of disposable face mask and identifies the characteristic of the constituent materials through morphological, chemical, physical, and thermal analyses. Based on these investigations, a mechanical recycling protocol with different approaches is proposed. Advantages and disadvantages of the different recycling solutions are discussed with considerations on necessary separation processes and other treatments. The four solutions investigated lead to a recycling index from 78 to 91% of the starting disposable mask weight. The rheological, mechanical, and thermo-mechanical properties of the final materials obtained from the different recycling approaches are compared with each other and with solutions present on the market resulting in materials potentially industrially exploitable
Synthesis and characterization of a novel star polycaprolactone to be applied in the development of graphite nanoplates-based nanopapers
No full textThe work was focused on the synthesis and characterization of a polymer designed with suitable features to be applied in the development of graphite nanoplates (GNP)-based nanopapers, prepared by using a solution blending approach, followed by filtration, drying and pressing treatments. Indeed, the polymer was tailored to possess: i) pyrenic functionalities, potentially capable of interacting with the graphite surface; ii) a star shape to promote the formation of a physical networking among the GNP layers; iii) arms made of a semicrystalline biopolymer, namely polycaprolactone (PCL), to obtain a mechanically robust and sustainable system. The polymer structure, synthesized by applying a three-step procedure, was validated by IR and 1H NMR measurements. The presence of the pyrenic end groups turned out to decrease the crystallinity of the polymer, compared to the starting PCL with hydroxylic and carboxylic functionalities, while significantly increasing its thermal stability at high temperature. The star shape structure of the synthesized PCL, together with its pyrene functionality, allowed introducing into the nanopapers structure a greater amount of polymer than that which can be inserted by using a high-molecular weight linear PCL. Moreover, GNP was found to promote significantly the pyrenic-PCL crystallization, acting as a nucleating agent. The strong interaction between the functionalized PCL and GNP delivered nanopapers exhibiting remarkable thermomechanical stability, up to well above the PCL melting temperature, coupled with noticeable heat spreading performance. Indeed, the developed nanopapers, being also based on a biopolymer, represent novel promising high performance and sustainable materials
Properties of graphene-related materials controlling the thermal conductivity of their polymer nanocomposites
Full text linkDifferent types of graphene-related materials (GRM) are industrially available and have been exploited for thermal conductivity enhancement in polymers. These include materials with very different features, in terms of thickness, lateral size and composition, especially concerning the oxygen to carbon ratio and the possible presence of surface functionalization. Due to the variability of GRM properties, the differences in polymer nanocomposites preparation methods and the microstructures obtained, a large scatter of thermal conductivity performance is found in literature. However, detailed correlations between GRM-based nanocomposites features, including nanoplatelets thickness and size, defectiveness, composition and dispersion, with their thermal conductivity remain mostly undefined. In the present paper, the thermal conductivity of GRM-based polymer nanocomposites, prepared by melt polymerization of cyclic polybutylene terephtalate oligomers and exploiting 13 different GRM grades, was investigated. The selected GRM, covering a wide range of specific surface area, size and defectiveness, secure a sound basis for the understanding of the effect of GRM properties on the thermal conductivity of their relevant polymer nanocomposites. Indeed, the obtained thermal conductivity appeares to depend on the interplay between the above GRM feature. In particular, the combination of low GRM defectiveness and high filler percolation density was found to maximize the thermal conductivity of nanocomposites
Thermal and UV aging of polypropylene stabilized by wine seeds wastes and their extracts
No full textA commercial tannin wine seed extract powder (T), a seed polyphenol extract (Sext) and virgin wine seeds wastes (Se) have been mixed with polypropylene (PP) and tested as long-term stabilizers. Their stabilizing activity has been compared with that of a synthetic antioxidant commonly used within PP (Irganox 1010). Each sample has been subject to both UV and thermal aging. The PP-based films photo-oxidation has been followed through the C=O formation over the aging time by FT-IR. The PP-based tensile specimens have been oven aged and the mechanical properties loss has been investigated monitoring the variation of the elongation at break. Melt Flow Index (MFI) measures and Different Scanning Calorimetry analysis have been conducted on thermally aged samples. At the same time, wine derived additives have been characterized in terms of total polyphenol content, FT-IR and UV/VIS spectra meanwhile catechin and gallic acid have been quantified by LC-MS. Experimental results have evidenced the ability of all the wine derived additives to withstand both to thermal and UV long-term degradation. In particular, wine seeds extracts exhibit the best results in terms of stabilization (even better than Irganox 1010) without compromising the PP mechanical, thermal, morphological and rheological properties
Thermal and UV aging of polypropylene stabilized by wine seeds wastes and their extracts
Full text linkA commercial tannin wine seed extract powder (T), a seed polyphenol extract (Sext) and virgin wine seeds wastes (Se) have been mixed with polypropylene (PP) and tested as long-term stabilizers. Their stabilizing activity has been compared with that of a synthetic antioxidant commonly used within PP (Irganox 1010). Each sample has been subject to both UV and thermal aging. The PP-based films photo-oxidation has been followed through the C=O formation over the aging time by FT-IR. The PP-based tensile specimens have been oven aged and the mechanical properties loss has been investigated monitoring the variation of the elongation at break. Melt Flow Index (MFI) measures and Different Scanning Calorimetry analysis have been conducted on thermally aged samples. At the same time, wine derived additives have been characterized in terms of total polyphenol content, FT-IR and UV/VIS spectra meanwhile catechin and gallic acid have been quantified by LC-MS. Experimental results have evidenced the ability of all the wine derived additives to withstand both to thermal and UV long-term degradation. In particular, wine seeds extracts exhibit the best results in terms of stabilization (even better than Irganox 1010) without compromising the PP mechanical, thermal, morphological and rheological properties
Designing 3D printable polypropylene: Material and process optimisation through rheology
Full text linkA polypropylene-based material has been formulated to be suitable for fused deposition modelling (FDM). In fact, the high volumetric shrinkage and the rheological behaviour are main problems whereby polypropylene (PP) is not commonly used as a 3D printing filament. Experimental results have evidenced how material modifications have a strong impact on rheological behaviour, providing critical features that permit and improve material printability. An optimised 20 wt% talc filled heterophasic PP copolymer has been developed. The peculiar properties of the materials have been assessed by thermal characterisation and rheological analysis. Several process parameters (extrusion temperature, screw speed, cooling conditions) have been evaluated in order to obtain a proper filament. Finally, a model part has been printed using different settings to check printing quality by morphological analysis
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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