1,721,025 research outputs found
Compatibilization strategies and analysis of morphological features of poly(butylene adipate-co-terephthalate) (PBAT)/poly(lactic acid) PLA blends: A state-of-art review
No full textPBAT is a compostable biopolyester, potentially obtainable from renewable resources, of great commercial interest. Thanks to its lower price, ease in processability and especially high ductility PBAT will very likely emerge in the next few years as the preeminent flexible bioplastic, ahead of contenders such as polybutylene succinate (PBS) or polycaprolactone (PCL) and it will likely become one of the most important biodegradable plastics, alongside PLA, which stays the major biopolymer for rigid applications. PBAT is often blended with PLA, a rigid bio-based polymer, that lends stiffness. PLA is a very rigid material with low impact resistance, it is, therefore, complementary to PBAT in the design of high performance and multi-functional biodegradable plastics. Despite the great and increasing interest of the market in PBAT, to date a general overview of the scientific literature which critically explores potentials of PBAT, with focus on design of engineered PBAT/PLA blends, is missing. The present works aims at filling this gap, laying the basis to create a link between fundamental research on PBAT and industrial applications. A general overview of the market and of the state of the art of PBAT based blends is herein provided, focusing on PBAT/PLA blends and possible compatibilization strategies. This work aims to achieve a double target: scientific and social. The scientific target is to summarize the main design criteria used in the conception of engineered plastics based on PBAT blends with PLA, revealing their implementation secrets and strategic aspects. The social target is to develop a useful guide for sector technicians, policy makers and stakeholders to promote the use of biodegradable materials instead of conventional plastics in an even wider range of applications, in order to significantly reduce the environmental impact of plastic products
Advances in design and manufacturing of environmentally friendly and biocide-free antifouling/foul-release coatings: replacement of fluorinate species
No full textAmphiphilic coatings are nowadays described as the most promising strategy for the achievement of an effective and eco-friendly antifouling marine paint, based on a physical principle. Nevertheless, most of the preparations imply the introduction of fluorinate chemicals for the formation of the hydrophobic moieties, which are potentially toxic for the marine environment in the case of an accidental release. The present work evaluates the possibility of removing fluorinate species for the implementation of such coatings and their replacement with analogous long-alkyls. In particular, this work presents an easily implementable procedure for the manufacturing of an amphiphilic system that exploits the reactivity of a commercially available –OH-rich hybrid polysiloxane resin. The resin was first modified through sol–gel chemistry that was used in the grafting of a silane-bearing hydrophobic long-alkyl chain, while the introduction of the hydrophilic moieties was conducted contextually to the curing process, through the reaction with a commercially available PEG-ilate isocyanate hardener. The effective persistence of the amphiphilic character with respect to the replacement of the fluorinate silane by the alkylsilane was ensured by the measurement of the hysteresis contact angle. The effectiveness of the persistence of the antifouling/foul-release properties was assessed through testing against the adhesion and deposition of egg white, as a proteinaceous probe, Mytilus edulis (mussel) and Ulva intestinalis (algae). All the tests indicated that the amphiphilic coating prepared from long-alkyl silane performed even better than fluorinate silane-containing samples in this hybrid coating system resulting from the fusion of a xerogel and a resin. The results suggested that the use of a long alkyl silane was an effective alternative to the use of potentially noxious fluorinate silanes, with advantages that boost the ecological benefits and also include the performance of the coating
Cast extrusion of low gas permeability bioplastic sheets in PLA/PBS and PLA/PHB binary blends
No full textBinary blends based on polylactic acid (PLA) and other biodegradable polyesters from renewable sources (namely, polybutylene succinate (PBS) and poly-3-hydroxybutyrate (PHB)) were prepared by reactive compounding extrusion. The achieved polymeric compounds were reprocessed by cast extrusion to manufacture the corresponding bioplastic sheets. Three different binary blends, one of which also including tocopherol, an oxygen scavenger, were investigated to ensure high-barrier of the bioplastic sheets to oxygen permeation. Physical, mechanical and chemical properties of the bioplastic sheets were, therefore, comparatively evaluated by differential scanning calorimetry, infrared spectroscopy, tensile tests and gas permeability. The experimental results showed a remarkable improvement in the oxygen barrier properties, especially on sheets manufactured in the PLA/PHB binary blend, without negatively affecting their thermo-mechanical response. Based on experimental evidences, the PLA/PHB binary blend is found to be extremely promising for the development of bio-based and biodegradable polymeric materials with low oxygen permeation, that is, for the development of suitable alternatives to conventional and highly pollutant oil-based plastics
Extrusion blow molding of environmentally friendly bottles in biodegradable polyesters blends
No full textIncreasing awareness of the environmental impact of oil-relying plastic materials is prompting Academia and manufacturing industry to develop eco-friendly materials and alternative technological solutions. Blown bottles and containers represent a significant share of the worldwide plastic market and great environmental concern is arising about their disposal. Generally, blown plastic bottles are made of three different materials: (i) a cap manufactured from High Density Polyethylene (HDPE), (ii) a bottle body manufactured from Polyethylene Terephthalate (PET), (iii) a label manufactured from printed Low Density Polyethylene (LDPE). The disposal of blown bottles requires, therefore, the separation of the different materials and, then, their individual recovery. An eco-friendly alternative to multi-material blown bottles is the development of a bottle entirely made from a biodegradable polymeric blend, designed to be suitable for manufacturing both the cap, the bottle body and the label. In this framework, the present manuscript deals with the design and development of novel biodegradable blends based on bio-based polyesters. The blends are herewith specialized for extrusion blow molding of the bottle body, although they could be further customized for both the cap and the label. Twin-screw co-rotating extrusion of the compounds, extrusion blow molding of the compounds for bottle manufacturing and the evaluation of the thermo-physical and mechanical properties of the bottles are hereinafter reported. The novel polymeric blends are found to be suitable for extrusion blow molding of the bottle body, also exhibiting valuable performances in terms of mechanical strength and impact resistance as well as protection against gas permeation and light transmission
Study of binary PLA/PBSA and ternary blends PLA/PCL/PBSA for the manufacturing of single dose strips
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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
Design, development and first validation of “biocide-free” anti-fouling coatings
No full textNew antifouling (AF) coatings were designed and manufactured exploiting the proven foul-release (FR) properties of amphiphilic systems and comparing them with fully hydrophobic and hydrophilic systems. The novel strategy implied a simple synthesis route that involves exclusively the chemistry of polyurethanes. The system was indeed constituted by a corrosion resistant polysiloxane-polyester hybrid resin as binder, rich in highly reactive hydroxyl groups that make the polymer associable to the polyol of a polyurethane couple. Hydrophilic and hydrophobic moieties were introduced in the form of lateral chains of isocyanate hardeners. The system resulted easily implementable due to the combination of commercially available raw materials and the rapid kinetic of the reaction. This method was used to prepare amphiphilic, as well as fully hydrophilic and hydrophobic systems, which were spray coated on construction steel samples. The coating wettability was analysed on all samples through the measurement of wetting hysteresis, highlighting the amphiphilic behaviour of the formulations. The highest amphiphilic character was detected on the hydrophilic reference sample, probably due to the highest mobility of PEG-ilate chains under this configuration. Anti-fouling properties were determined by the evaluation of the retention rate of two alive Mediterranean marine organisms, Mytilus Edulis and Ulva Intestinalis, on the surface of samples. A further test was carried out to evaluate the AF/FR properties against a natural protein probe, namely egg white. The test carried out with natural organisms proved the suitability of all the proposed strategies to the implementation of effective AF/FR marine paints. The egg white test assessed that the highest efficiency in AF/FR activity was detained by the fully hydrophobic systems. The observation of the surface of the samples by SEM in back scatter modality revealed that the chemical patterning of the hydrophobic scenario could play a significant role in the development of such behaviour
Design, manufacturing and testing of anti-fouling/foul-release (AF/FR) amphiphilic coatings
No full textIn this study, innovative strategies for the manufacturing of anti-fouling/foul-release (AF/FR) coatings based on the implementation of amphiphilic surfaces by the chemistry of silanes and polyurethanes were evaluated. The newly developed process for the synthesis of amphiphilic resins involved the introduction of hydrophobic functionalities by the sol-gel reaction of a fluorinate-alkyl bearing silanes (FTSi). Conversely, the introduction of hydrophilic PEG-ilate functionalities was alternatively implemented by the sol-gel reaction with PEG-ilate silanes (PEGSi) or PEG-ilate isocyanates. These synthesis processes were possible thanks to the adoption of a peculiar hydroxyl-rich hybrid resin, consisting in a polysiloxane resin modified by polyester domains. Manufacturing of the formulations was a rapid process (shorter than 3 h), and easily implementable thanks to the sole use of commercially available raw materials. The synthesis did not require any special technical arrangement such as reflux conditions, autoclave or inert atmosphere. The effectiveness of the synthesis was evaluated by FTIR analysis, while the amphiphilic character of the surfaces was ensured by wettability test against water. AF/FR properties were tested under severe conditions using a protein test probe (i.e., the so called “egg white” test) that well simulates the substances secreted by the bio-fouling organisms to adhere. All the samples tested showed amphiphilic character, with most of them featuring excellent AF/FR properties
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