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Piezoelectric composite films for energy harvesting devices
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Production of fully natural-based boards from hemp fibers and rice husk particles. Investigation on morphology, mechanical properties, thermal, hydrothermal and photo-thermal ageing
No full textIn the present study, two different crop by-products (namely, hemp long fibers and rice husk particles)
have been used to produce natural-based boards (fiber- and particleboards) by using corn starch as
binder in order to have the consistence and strength required for internal panels and furniture.
A simple and economic transformation process based on the use of hot compression molding has been
employed. Mixing fibers or particles with binder has been carried out by simple impregnation in a
water solution. Long fibers as well as small particles might be processed with the same machine
avoiding any health and pollution problems.
Fully green boards have been obtained and characterized in terms of morphology, moisture
absorbance and mechanical properties (assessed by both dynamic-mechanical thermal analysis and
tensile tests). In addition, the influence of different relative humidity levels on composite modulus has
been investigated. Long fibers have proven to be capable of sustaining approximately double loading
with respect to articles.
Furthermore, the prepared boards have been subjected to three different accelerated aging conditions:
namely, i) high temperature (thermal ageing); ii) high temperature combined with humidity and iii)
high temperature in the presence of UV radiations (photo-thermal ageing). After these tests both
boards have maintained good mechanical properties, with a restrained reduction of their storage
modulus (lower than 20% with respect to the prepared materials)
Recent Advances in Biochar Polymer Composites
Get PDF“Biochar” (BC) is the solid residue recovered from the thermal cracking of biomasses in an oxygen-poor atmosphere. Recently, BC has been increasingly explored as a sustainable, inexpensive, and viable alternative to traditional carbonaceous fillers for the development of polymer-based composites. In fact, BC exhibits high thermal stability, high surface area, and electrical conductivity; moreover, its main properties can be properly tuned by controlling the conditions of the production process. Due to its intriguing characteristics, BC is currently in competition with high-performing fillers in the formulation of multi-functional polymer-based composites, inducing both high mechanical and electrical properties. Moreover, BC can be derived from a huge variety of biomass sources, including post-consumer agricultural wastes, hence providing an interesting opportunity toward a “zero waste” circular bioeconomy. This work aims at providing a comprehensive overview of the main achievements obtained by combining BC with several thermoplastic and thermosetting matrices. In particular, the effect of the introduction of BC on the overall performance of different polymer matrices will be critically reviewed, highlighting the influence of differently synthesized BC on the final performance and behavior of the resulting composites. Lastly, a comparative perspective on BC with other carbonaceous fillers will be also provided
Rheological, mechanical, thermal and electrical properties of UHMWPE/CNC composites
Get PDFIn this work, composites of ultra high molecular weight polyethylene (UHMWPE) and various loadings of cellulose nanocrystals (CNCs) were prepared exploiting different methods. Besides, the microstructure, rheological, mechanical, thermal and electrical properties of the obtained materials were thoroughly investigated. As far as the mechanical behavior of the formulated systems is concerned, CNC-reinforced composites exhibited improved values of Young’s modulus and yielding strength with respect to the unfilled UHMWPE. In particular, the maximum value of ultimate tensile strength was achieved for the systems containing 0.1 wt% of CNCs, and then progressively decreased with increasing the particle loading. As assessed by XRD and DSC analyses, CNC-containing composites showed higher crystallinity degree as compared to the unfilled UHMWPE, suggesting a nucleating effect of embedded CNCs. Morphological and rheological analyses demonstrated that the preparation method involving a solution mixing step is more effective than dry method in promoting the achievement of a peculiar morphology, in which the embedded particles are preferentially located in the interfacial region between UHMWPE grains. Finally, electrical and thermal measurements documented that UHMWPE/CNC composites obtained by solution mixing showed slightly higher thermal conductivity and lower volume resistivity in comparison with the composites prepared by dry method, highlighting that the proper selection of the processing method plays a key role in determining the material final performances
Study of the adhesive properties versus stability/aging of hernia repair meshes after deposition of RF activated plasma polymerized acrylic acid coating
Get PDFIn order to confer adhesive properties to commercial polypropylene (PP) meshes, a surface plasma-induced deposition of poly-(acrylic acid) (PPAA) is performed. Once biomaterials were functionalized, different postdeposition treatments (i.e. water washing and/or thermal treatments) were investigated with the aim of monitoring the coating degradation (and therefore the loss of adhesion) after 3 months of aging in both humid/oxidant (air) and inert (nitrogen) atmospheres. A wide physicochemical characterization was carried out in order to evaluate the functionalization effectiveness and the adhesive coating homogeneity by means of static water drop shape analysis and several spectroscopies (namely, FTIR, UV-Visible and X-ray Photoemission Spectroscopy). Themodification of the adhesion properties after post-deposition treatments aswell as aging under different storage atmospheres were investigated by means of Atomic Force Microscopy (AFM) used in Force/Distance (F/ D) mode. This technique confirms itself as a powerful tool for unveiling the surface adhesion capacity as well as the homogeneity of the functional coatings along the fibers. Results obtained evidenced that post-deposition treatments are mandatory in order to remove all oligomers produced during the plasma-treatment, whereas aging tests evidenced that these devices can be simply stored in presence of air for at least three months without a meaningful degradation of the original properties
Structure–property relationships in polyethylene based films obtained by blow molding as model system of industrial relevance
No full textA method for the study of structure–property relationships of polyethylene (PE)-based films of potential use in food packaging has been set up. The approach has been demonstrated in the case of films obtained by blow-molding using model mixtures of two different polyethylenes, namely a metallocene-made grade of linear low density polyethylene (mLLDPE) and a low density polyethylene (LDPE). We show that physical properties important for numerous applications of these films, such as water vapor and oxygen permeability, toughness and stress strength, are related to the molecular structure and structural and morphological parameters of the blends, in particular, thickness of amorphous layers in lamellar stacks, lamellar thickness, lamellar twisting, and degree and type of branching
All Natural High-Density Fiber- and Particleboards from Hemp Fibers or Rice Husk Particles
Get PDFIn the present study, long hemp fibers and rice husk particles have been used for producing all natural-based boards for building, automotive and in-door furniture, employing a simple and economic transformation process (namely, compression molding). In order to have the required consistence and mechanical strength, cornstarch was employed as binder. By this way, fiber- and particleboards have been prepared and characterized in terms of morphology, mechanical properties (flexural modulus and strength). The influence of different relative humidity levels on composite storage modulus and heat deflection temperatures has been investigated, as well. Long fibers turned out to be capable of sustaining approximately three times the load with respect to particles in standard conditions. Thermal, hygro- and photo stability of the above materials have been investigated under three ageing conditions: namely, (i) high temperature (thermal ageing), (ii) humidity plus high temperature (hygro-thermal ageing) and (iii) UV radiations (photo ageing). Regardless of the experimental ageing conditions adopted, fiberboards have shown good mechanical stability with a modest decrease of storage modulus (<20%) with respect to the values before exposure
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Mechanical, electrical, thermal and tribological behavior of epoxy resin composites reinforced with waste hemp-derived carbon fibers
Get PDFShort hemp fibers, an agricultural waste, were used for producing biochar by pyrolysis at 1000°C. The so-obtained hemp-derived carbon fibers (HFB) were used as filler for improving the properties of an epoxy resin using a simple casting and curing process. The addition of HFB in the epoxy matrix increases the storage modulus while damping factor is lowered. Also, the incorporation of HFB induces a remarkable increment of electrical conductivity reaching up to 6 mS/m with 10 wt% of loading. A similar trend is also observed during high frequency measurements. Furthermore, for the first time wear of these composites has been studied. The use of HFB is an efficient method for reducing the wear rate resistance and the friction coefficient (COF) of the epoxy resin.
Excellent results are obtained for the composite containing 2.5 wt% of HFB, for which COF and wear rate decrease by 21% and 80%, respectively, as compared with those of the unfilled epoxy resin. The overall results prove how a common waste carbon source can significantly wide epoxy resin applications by a proper modulation of its electrical and wear properties
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