Chitosan microparticles loaded with essential oils having in view leather applications

Chitosan is a biopolymer attracting considerable attention for diverse applications due to its unique properties like biodegradability, biocompability, non-toxicity and antimicrobial activity. It is obtained by the partial N-deacetylation of chitin, which is the second most abundant polysaccharide in nature, next to cellulose. Chitosan is a viable base material for functional coatings development, namely due to its antimicrobial activity. This characteristic is especially useful for footwear applications that constitute products prone to microbial attack. In this context, developing antimicrobial coatings to be used in footwear components in direct contact with the feet are of great interest, both at industrial level (reducing possibility of material deterioration and quality loss), as well as, from the consumer’s point of view (decrease of skin infections and minor unpleasant odours). Following our previous work, where leather impregnation with chitosan was studied at laboratorial level with quite promising results, and having in view the final application (footwear leather components), where the antimicrobial effect must need to be enhanced, we have developed the idea of microencapsulate different essential oils, with recognized antimicrobial activity like lemon, oregano, eucalyptus and pine. These chitosan-based microparticles, loaded with the chosen essential oil are intended to be applied conjunctly with the chitosan coating process previously studied. Microencapsulation will ensure that the loaded core material will be progressively released, reinforcing the antimicrobial durability and effectiveness of the final product.COMPETE, QREN and EU within the project QREN-ADI-1585-ADVANCEDSHO

Chitosan-based leather functional coatings with improved antimicrobial properties

Among the interesting biological activities that have been ascribed to chitosan, the antimicrobial activity is probably the one that generates the higher number of applications. Developing antimicrobial coatings for footwear components to be used in direct contact with the feet is of great interest; both at industrial level (reducing the possibility of material deterioration and quality loss) and from the consumer’s point of view (decreasing skin infections and minimizing unpleasant odours). One weakness of this application is addressed to the durability and efficiency of the product antimicrobial activity, since it is directly associated with the availability of the positively charged R–NH3 + groups that are depleted during use

Chitosan as an antimicrobial agent for footwear leather components

In the footwear industry, microorganisms’ growth can pose problems of material deterioration with associated unpleasant smell and generate possible infections in susceptible individuals. Generally, footwear presents high relative humidity conditions that enable the growth of bacteria and fungi. Additionally, leather itself and some tannery agents such as oils and greases, provide a substrate where microorganisms can grow. In the foot, microtraumas caused by ingrown nails, abrasions and lacerations can allow microbial invasion through epidermis, resulting in skin infection. In this work, the applicability of chitosan functional coatings to leather was tested, with the purpose to develop new base materials to produce footwear components. The leather treated with chitosan was then studied for its antibacterial properties against 3 different bacteria.COMPETE, QREN and EU (project QREN-ADI-1585-ADVANCEDSHOE)

Valorization of lignin side-streams into polyols and rigid polyurethane foams—a contribution to the pulp and paper industry biorefinery

Valorization of industrial low-value side-streams are of great interest, contributing to boosts in the circular economy. In this context, lignin side-streams of the pulp and paper industry were oxypropylated to produce biobased polyols and tested in the synthesis of rigid polyurethane (RPU) foams. E. globulus lignins, namely a lignin isolated from an industrial Kraft black liquor and depolymerized lignins obtained as by-products of an oxidation process, were used. RPU foams, synthesized with 100% lignin-based polyols and using a 1.1 NCO/OH ratio, were characterized concerning apparent density, morphology, thermal conductivity, thermal stability, and heat release rate (HRR). Foams containing the lignin-based polyols presented densities varying from 44.7 to 112.2 kg/m3 and thermal conductivity in the range of 37.2–49.0 mW/mK. For the reference foam (sample produced with 100% wt. Daltofoam TP 32015 polyol), values of 70.9 kg/m3 and 41.1 mW/mK were obtained, respectively. The achieved results point out the viability of using the generated lignin-based polyols at 100% content in RPU foams, mainly when depolymerized lignins are used. Moreover, fire retardancy was favored when the lignin-based polyols were introduced. The proposed strategies can contribute to establishing the integrated pulp and paper biorefinery concept where material synthesis (polyols and RPU foams) can be combined with chemical production (vanillin and syringaldehyde).Foundation for Science and Technology (FCT, Portugal) and FEDER under Program PT2020 for financial support to CIMO (UIDB/00690/2020), and to UIDB/50020/2020 of the Associate Laboratory LSRE-LCM—funded by national funds through FCT/MCTES (PIDDAC); national funding by FCT, PI, through the institutional scientific employment program contract for Isabel P. Fernandes. This work was carried out under the Project No. 33969 Bioblocks—Design of biobased products from renewable lignocellulosic sources as precursors for the bioindustry of chemical synthesis and biomaterials—financed by FEDER through the Operational Program for Competitiveness Factors (POFC) and QREN. To COST Action LignoCOST (CA17128) supported by COST (European Cooperation in Science and Technology).info:eu-repo/semantics/publishedVersio

The use of bio-based additives (lignin, starch and cellulose) in thermoplastic polyuretane formulations to enhance the biodegradability of footwear components

Thermoplastic polyurethanes (TPUs) are one of the most widely used polymeric materials. They can be used in an extensive range of applications, including automotive, footwear, interior design, adhesives, coatings, textile and biomedical. In what concerns the footwear sector, it is estimated that TPU based components represent about 60% of the whole European production of footwear components [1]. On the other hand, the use of a wide variety of additives in TPU formulations (e.g. pigments, coatings and fillers) limits the possibility of recycling. In such scenario, biodegradable polymers could offer an excellent solution to the environment hazard posed by the conventional materials [2]. Therefore, given the widespread use of TPUs and associated waste management problems, it makes sense to invest on the development of more biodegradable and environmental compatible solutions. For this purpose, the incorporation of bio-based and biodegradable additives is being studied in the last years [2-4]. The incorporation of a biodegradable compound, even at a low content in a TPU formulation, can promote biodegradation. It will constitute a preferential site for microorganisms’ attack thus favouring biodegradation initiation and progression. In this work, a base TPU used in the footwear industry was modified by compounding with three biobased additives (lignin, starch and cellulose). Biodegradability of the resulting materials was evaluated in agar plate tests against the fungi Aspergillus niger ATCC16404, the gram negative bacteria Pseudomonas aeruginosa ATCC9027 and an association of both (consortium). In a second phase soil tests have been also performed.info:eu-repo/semantics/publishedVersio

Development of a prototype to access biodegradability of TPU shoe soles under controlled conditions

In the last years, the increasing problems posed by waste management have stimulated the interest in developing more sustainable and bio-based solutions for the footwear industry, including the use of biodegradable materials. As part of the NEWALK project, the objective of this work consisted in optimizing and implementing a respirometry system prototype. Besides evaluating different variables, two different approaches for measuring the evolved CO2 were assayed. Compared to manual titration, the use of conductivity offers the advantage of an automatic continuous monitoring.info:eu-repo/semantics/publishedVersio

Evaluation of the almond shell oxypropylation process trough the surface response methodology

The efficiency of an oxypropylation process depends on several variables and operating conditions, which may not be generalized due to the diverse nature of subtracts. In lignocellulosic biomasses, the content of each fraction (lignin, cellulose and hemicellulose) can differ, as well as, the crystalline organization, which may limit reagent’s access to biomass. Also, the hydroxyl content can vary among biomasses; high values demand higher amounts of reactants, namely catalyst content, and more severe reaction conditions. Therefore, owing to biomass variability, selection of the operating conditions for oxypropylation their optimization is a key issue. In this context, one-factor-at-a-time approaches are commonly used to optimize processes; but it is well-known that optimal operating conditions or interactions between variables cannot be predicted by this simplistic method. Both problems may be overcome by employing the response surface methodology (RSM).info:eu-repo/semantics/publishedVersio

Screening of different microorganisms for their biodegradation capacity regarding polyester-based thermoplastic polyurethanes

and bio-based solutions in shoe manufacturing, including the use of biodegradable materials. As a first step towards the proposal of such solutions, in this work different microorganisms were screened for their intrinsic capacity to degrade a base TPU. The biodegradability was tested using the agar plate method against different bacteria, fungi and a consortium of both. The most promising results, corresponding to higher weight-loss percentages of the TPU sample, were obtained using the consortium of Pseudomonas aeruginosa and Aspergillus niger. These best conditions were thereafter applied to TPU samples compounded with biobased additives.info:eu-repo/semantics/publishedVersio

Analysis of the oxypropylation process of a lignocellulosic material, almond shell, using the response surface methodology (RSM)

info:eu-repo/semantics/publishedVersio

Thunderstorm and Lightning Characteristics Associated With Sprites in Brazil

A study of the thunderstorm and cloud-ground lightning characteristics associated with sprite events observed in Brazil is presented. The study is based on ground and aircraft sprite observations with high sensitivity intensified CCD cameras of six different thunderstorms, GOES satellite infrared images, radar and lightning network data. A total of eighteen transient optical events were recorded at three different days in 2002 and 2003, sixteen of which exhibited vertical structures typically associated with sprites. Four thunderstorms were associated with two different cold fronts, one with a Mesoscale Convective System, and one was a local isolated thunderstorm. The sprites occurred during time periods when the percentage of positive flashes was higher than the average percentage for the storm lifetime. The lightning associated with the sprite events was all positive flashes with a mean peak current higher than the mean value for all flashes in the storms