Cork Powder Research Articles

A Simple Method To Improve Cork Powder Waste Adsorption Properties: Valorization as a New Sustainable Wine Fining Agent

Cork powder, an abundant, natural, and cheap byproduct of the cork stopper industry was explored, either in its natural form or after improvement of their adsorption properties by simple physicochemical treatments, as a new sustainable wine fining agent for removing negative volatile phenols (VPs), responsible for one of the most frequent and widespread aroma defects in red wine known as “Brett character”. Cork adsorptive performance improvement by removal of cork extractives, air removal, and ethanol impregnation allowed us to obtain 41% to 62% of 4-ethylphenol (4-EP) and 50% to 53% of 4-ethylguaiacol (4-EG) removal from red wine. Performance of the optimized cork powder on removing the negative sensory phenolic defect and recovery of the positive fruity and floral sensory attributes was not significantly different from activated carbon and chitosan, two of the most efficient treatments currently available. Optimized cork powder can be a good solution for VPs removal without impacting negatively on wine ...

Optimization of phosphate removal from aqueous solution using activated carbon supported zero-valent iron nanoparticles: application of RSM approach

In this study, activated carbon (AC) prepared from cork powder was used in synthesis of AC stabilized nano-zero-valent iron (AC/NZVI) composite and evaluated phosphate (PO43−) removal efficiency from aqueous solution. The as-obtained AC/NZVI was characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) and X-ray diffraction (XRD) analysis. Response surface methodology based on a three-level, three-factor, Box–Behnken design (B.B.D.) has been employed for determination of optimal combination of three significant process factors or variables such as temperature, solution pH and AC/NZVI dose, for maximum removal of PO43− from aqueous solution. Based on B.B.D. experimental design, a limited number of experiments were performed in a cost-effective manner at initial PO43− concentration of 211 mg L−1 as a fixed input parameter. A statistically validated quadratic model was developed to predict the responses in the form PO43− removal capacity from aqueous solution and adequacy of the model was evaluated using regression analysis and analysis of variance. The model predicted maximum PO43− removal capacity of the AC/NZVI was 152.12 mg g−1 under the optimal condition of process variables (temperature 60 °C, pH 3.5, and AC/NZVI dose 0.4 g L−1) which was strictly closer to the experimental value (151.10 mg g−1) obtained in batch experiment under the same optimize condition of process variables. The result of the study inferred that all three factors had a significant impact on removal of PO43−.

Larch tannin-based rigid phenolic foam with high compressive strength, low friability, and low thermal conductivity reinforced by cork powder

Phenolic foam (PF) has recently been spotlighted because of their excellent flame resistance, low smoke emission, and low production costs. However, PF is mainly prepared from petroleum-based products, and it exhibits poor mechanical strength and high friability. In this study, larch tannin-based rigid phenolic foams (LTPFs) and cork powder was used as filler to prepare cork powder-reinforced LTPFs (CLTPFs). The chemical structure, cell morphology, compressive mechanical properties, friability, thermal properties, and flame retardancy of the foams were evaluated. The results indicated that the LTPFs showed inferior cell morphology, compressive strength and thermal properties, high friability and high flame retardancy as compared with the neat PF. LTPF10 presented the maximal limiting oxygen index (LOI) of 47.8%. As compared with the unreinforced LTPFs, CLTPFs possessed excellent cell morphology, high compressive strength, low thermal conductivity, low friability, and good thermal properties. At a cork powder dosage of 1 wt%, the compressive strength and modulus of CLTPFs increased by 14.84% and 16.18%, respectively; the pulverization ratio and thermal conductivity of CLTPFs decreased by 18.4% and 32.29%, respectively, as compared with those of the LTPF. In addition, the introduction of cork powder improved the thermal stability of LTPFs. The LOI values of the CLTPFs were slightly lower than those of LTPFs. LTPF reinforced with 1 wt% cork powder exhibited the best combination of the features.

Expanded perlite/cork fillers applied to aerospace insulation materials.

Insulations for rocket motors such as Flexible Thermal Protections (FTPs) and Rigid Thermal Protection (RTPs) act as thermal barriers against the hyperthermal environment from the solid propellant combustion. FTPs present dual function: to extend RTPs performance, and to attenuate the propellant contraction. FTPs used in the Brazilian Space Program have asbestos in their composition since the 70´s; however, they are hazardous for human health. In this context, a mixture of Expanded Perlite (PExp) and Cork Powder (CP) was investigated as a replacement for asbestos. Results showed reduction about 21 % in density and an increase of 13 % in the ablative properties. The low mechanical properties not interfere in this type of FTP due to your function of attenuate the propellant contraction.

Development and properties of advanced composites based on cork and nanometric silicon carbide-filled phenolic resin

This paper presents the obtaining of advanced materials based on cork powder as reinforcement and phenolic resin (PR) with silicon carbide (nSiC) nanofiller as matrix with potential applications in aerospace industry. Three formulations were obtained: one control sample PR/cork with no nanofiller, two nanofilled samples with 1 and 2 wt% nSiC loadings into the resin. The materials were tested by flexural and compressive mechanical tests to determine their strength and stiffness, to determine their friction coefficient by tribological tests, to determine their thermal decomposition behaviour by TG-DSC analysis and to evaluate their thermal behaviour by thermal shock tests when subjected to extreme temperature directly from room temperature. The material structure was analysed by SEM visualizing the fracture cross-section after mechanical testing. The test results illustrate that silicon carbide nanoparticles improve flexural and compressive strength, but also stiffness and friction coefficient, delay thermal decomposition onset and improve thermal shock resistance. All these sustain the PR/nSiC/cork materials as potential advanced materials candidates for thermal protection applications.

A new configuration for bar adsorptive microextraction (BAμE) for the quantification of biomarkers (hexanal and heptanal) in human urine by HPLC providing an alternative for early lung cancer diagnosis

In this paper, a remodeling of the bar adsorptive microextraction (BAμE) technique is proposed with impregnation of the derivatization reagent on the surface of the adsorptive bar containing a biosorbent material. The derivatization reagent was 2,4-dinitrophenylhydrazine (DNPH), which was adsorbed on the surface of the bar containing cork powder as the extractor phase for the determination of two aldehydes (hexanal and heptanal) which are known as lung cancer biomarkers in human urine samples. The derivatization reaction and the extraction occurred simultaneously on the surface of the bar (length 7.5 mm) under acidic conditions. The method optimization was carried out by univariate and multivariate analysis. The optimal conditions for the method were a DNPH to aldehydes ratio of 40:1, buffer solution of pH 4.0, extraction time of 60 min and liquid desorption of 10 min in 100 μL of acetonitrile. The aldehydes were analyzed by HPLC-DAD with a simple and fast (6 min) chromatographic run. The limits of detection (LODs) for hexanal and heptanal were 1.00 and 0.73 μmol L−1, respectively. The relative recoveries in urine samples ranged from 88 to 111% with relative standard deviations (RSDs) being less than 7%. The method developed is of low cost and can be successfully used for the quantification of these two lung cancer biomarkers in human urine samples, potentially providing an early diagnosis of lung cancer.

Cork Liquefaction for Polyurethane Foam Production

Cork is one of the most important forest products in Portugal. The cork processing industry is highly resource-efficient, and the only residue is cork powder, which is too small for agglomerate production. This work studied the usage of cork powder for the production of added-value products via polyol liquefaction. Liquefactions were performed in a reactor using a mixture of polyethylene glycol (PEG 400) and glycerol as solvents, which were catalyzed by the addition of sulphuric acid. Several cork-to-solvent ratios, reaction temperatures, and reaction times were tested. Polyurethane foams were prepared by combining polyol mixtures with a catalyst, surfactant, blowing agent, and polymeric isocyanate. Mechanical tests of the produced foams were conducted, and compressive modulus of elasticity and compressive stress at 10% deformation were determined. The results show that the best conditions for obtaining high liquefaction yields are as follows: 160 °C for 1 h; glycerol-to-PEG 400 ratio of 1:9; cork-to-solvent ratio of 1:6; and 3% H2SO4 catalyst addition. The Fourier Transform Infrared (FTIR) spectra indicated that the lignocellulosic fractions of the cork were more selectively dissolved during acidified polyol liquefaction than the suberin. With liquefied cork powder using these optimized conditions, it is possible to produce polyurethane foams with desired properties.

Cork Plastic Composite Optimization for 3D Printing Applications

Among natural fillers, cork has been acknowledged as a suitable alternative of other cellular materials that are widely employed in engineering applications due to their low conductivity to heat, noise and vibration, high abrasion resistance and flexibility, high compressibility ratio, among other characteristics [1]. The eco-friendly features of natural fillers based composites make them a very promising and sustainable solution to large markets mainly if additive manufacturing technologies, such as 3D printing, are used [2]. Through 3D printers, engineers, designers and architects can create design and decor products with a free complexity of geometry. In this research work, plastic matrices of HDPE – obtained from conventional suppliers – were reinforced with different ratios of cork waste and natural cork powders – obtained from cork transformation industries – to find the optimum mixture for 3D printing. The effects of cork powders content in the plastic on the morphological, physical and mechanical properties of the composites were investigated through the density, optical microscopy, wettability, thermal analysis and tensile testing. Cork-based composites were processed by an extrusion system, and the mixture of polymer, adhesive and fillers is discussed. The results show that the addition of pure cork and cork waste can be processed with polymers such as HDPE, having adequate physical and mechanical properties.

Non‐isothermal crystallization kinetics of cork‐polymer composites for injection molding

ABSTRACTThe non‐isothermal crystallization behavior of cork–polymer composites (CPC) based on polypropylene (PP) matrix was studied. Using differential scanning calorimetry (DSC), the crystallization behavior of CPC with 15 wt % cork powder at different cooling rates (5, 10, 15, and 20 °C/min) was studied. The effect of a coupling agent based on maleic anhydride was also analyzed. A composite (PPg) containing polypropylene grafted maleic anhydride (PPgMA) and PP was prepared for comparison purposes. Crystallization kinetic behavior was studied by Avrami, Ozawa, Liu, and Kissinger methods. The Ozawa method fails to describe the behavior of these composites. Results show that cork powder surface acts as a nucleating agent during non‐isothermal crystallization, while the addition of PPgMA decreases the crystallization rate. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44124.

Recycling the Cork Powder in a PVC-Based Composite Material: Combined Effect on Physico-Mechanical and Thermal Properties

Abstract A large amount of cork powder (CP) produced by cork industry ended up in landfills, they are the result of the crushing of natural floor (bark) cork oak, hence the need to recycle these wastes to prevent environmental problems. To this end, the work is to combine the powdered cork recovered with a thermoplastic material to provide a cork based composite (CPC) having physico-mechanical characteristics and thermal very interesting. Several formulations of composite materials based on PVC (as matrix), cork powder (as a charge) and a PVC-g-MA coupling agent, have been the subject of experimental study to evaluate the physical-mechanical and thermal properties. To investigate the combined effect of cork powder and PVC-g-MA on composite properties, the samples were manufactured by varying the content of PC (30 %, 40 % and 50 %) with two PVC-g-MA concentrations. Improving the stability of PVC which is accentuated in the presence of the coupling agent. In addition, it was found that the incorporation of the coupling agent has enabled the elimination of the adverse effect of cork powder, improving the tensile strength. The composite obtained in this study yielded some promising properties, even if building strategies to achieve greater strength and rigidity could beings needed for specific applications.

A novel solid cylindrical composite material made of agglomerated cork inserts and silicone rubber resin during the flattening process

Present research work introduces a novel composite material consists of agglomerated cork inserts as the stiffener particles and silicone rubber as the resin and uses it as an energy absorber during lateral flattening process under the quasi-static lateral loading in the form of solid cylinder by the experimental method. Solid cylindrical composite specimens were manufactured with different agglomerated cork insert conditions consist of different insert shapes of cylindrical and cubic, different diameters and heights of cylindrical insert, and various insert densities. Also, some composite specimens were produced with two different insert patterns of arranged and random and with two different agglomerated cork insert mass fractions that called MAX and MIN conditions. Furthermore, the composite specimens were manufactured with three different specimen diameters. All the samples were laterally compressed between two rigid platens and their energy absorptions were investigated. Also, effects of all the above mentioned parameters were discussed. In addition, spring-back rates of the samples were studied to investigate probability of using the introduced composite as both of reversible and irreversible energy absorbers. Experiments show that in the MAX condition, composite specimens with cylindrical inserts have higher specific absorbed energy respect to the specimens with cubic inserts and with cork powder.

Natural polymeric water-based adhesive from cork liquefaction

Herein we disclose a novel formulation of two components water-based adhesive from a natural source, which is designed to glue lignocellulosic surfaces, mainly cork and wood. It is based on the aqueous extraction of liquefied cork, which results from the polyhydric alcohol acid-catalyzed liquefaction of cork dust or granules. The vacuum concentration of the referred extract leads to the first adhesive component, which is then mixed and homogenized with the second one, a curing aliphatic compound. The addition of “cork powder” to the adhesive formulation creates a stable adhesive with good shear strength values. Thus, a methodology for the valorization of cork dust, a hazardous waste, is here outlined.

Biomimetic cork-based CeO2 ecoceramics for hydrogen generation using concentrated solar energy

Naturally occurring and sustainable materials can be used as a template to create biomimetic/biomorphic ceramics, known as Ecoceramics (environmentally conscious ceramics). In this work, cork was chosen as template to produce novel ceria (CeO2) ecoceramics, for applications in water splitting for H2 production via direct concentrated solar thermochemical fuel production (TCFP). The cork powder was pyrolised at 900°C and the resulting carbon skeleton was infiltrated with an aqueous CeO2 precursor, and then heated at 1000°C for 2h to produce the ecoceramic. The cellular structure of the cork was maintained, with hexagonal cell dimensions of 20-30μm in diameter, but the grains were nanoscale at ≤100nm. XRD data confirmed that CeO2 was the only crystalline phase obtained. An important feature was that, while the rectangular side walls were maintained to hold the three-dimensionally ordered macroporous (3DOM) cellular cork structure, the rear hexagonal walls were pierced repeatedly through the structure, unlike in the original cork structure, which will allow gasses such as H2 to permeate well into the structure, greatly increasing the reactive area available for catalysis. The next step will be to test the capabilities of both the regular, porous 3DOM structure and the nanoscale grains for thermochemical water splitting to produce hydrogen under direct concentrated solar energy.

Cork waste in cement based materials

Abstract Cork is a natural material that has always been associated to mankind having huge potential and many uses. The cork industry worldwide consumes more than 280,000 t of cork a year. However, about 20% to 30% of the raw cork received at the processing units is rejected, mainly as cork dust. Finding useful applications for the rejected cork may have important economic and environmental implications. Trying to combine the advanced technology of self-compacting concrete and use of this waste from the cork industry, this study concerns the possibility of using cork powder as a substitute for fines in mixtures of self-compacting concrete. An experimental program was carried out to assess the behavior of this material in the mixture and define properties in terms of strength and durability of self-compacting concrete containing cork powder. It was found that it is possible to use an abundant waste material from the cork industry, cork powder, as fines in Self Compacting Concrete resulting in a good strength level (C 30/37) and suitable durability for common applications.

Magnetic wood-based biomorphic Sr3Co2Fe24O41 Z-type hexaferrite ecoceramics made from cork templates

Ecoceramics (environmentally conscious ceramics) are biomimetic/biomorphic ceramics, which use a naturally occurring and sustainable material as a template for their unique morphology and structure. Usually woods (or lignocellulosics) are used, due to the inherent cellular nature of their microstructures. The wood is pyrolised and the resulting carbon skeleton impregnated with a fluid, and this is then heated to combust the carbon template and convert the fluid precursor into a ceramic, while maintaining the structure of the original natural template. For the first time, ecoceramics have been made from cork, a totally sustainable wood that is harvested without harming the tree. Also for the first time, ecoceramics have been made of soft magnetic Z-type hexaferrites, in this case the room temperature multiferroic strontium Z ferrite Sr3Co2Fe24O41 (SrZ). Cork powder was pyrolised at 1000°C, infiltrated with an aqueous sol–gel SrZ precursor, and then heated at 1200°C/2h to produce the ecoceramic. The cellular structure of the cork was maintained, with a small reduction in the hexagonal cell dimension to 10μm diameter, but the cell walls remained 1–2μm thick, of a similar magnitude to the hexaferrite grain size. Both magnetic and XRD data agreed that there was a small portion of the SrW phase present in these ecoceramics as well, and the magnetic loop showed a magnetically soft ecoceramic with Ms=59.5Am2kg−1 (at 3T), and a low Hc of 16kAm−1.

Sonication as a foremost tool to improve cork liquefaction

A comparative study on conventional and ultrasound liquefaction of cork powder was conducted. Ultrasounds as an alternative energy source for the liquefaction of cork powder proved towards a kinetic study that ultrasounds can be applied for the development of a cleaner and faster liquefaction approach. The procedure herein disclosed was highly proficient in the conversion of this by-product from cork industry into polyols. A pseudo-first order reaction model was applied showing that ultrasound increased the speed of the reaction up to 4.5 times when compared with that from the conventional method. Micrographs also revealed that ultrasounds leaded to small particles and agglomerates of the residues which indicates that large molecular structures are not form during liquefaction since a short reaction time is needed. The fast and clean reaction allied with the low energy input needed for this approach led to an affordable technique for the conversion of cork into valuable biopolyols, biooils, or biofuel.

Cork: Sustainability and New Applications

Cork is a strategic material used in multiple applications and its use has accompanied mankind since the days of Ancient Egypt. The cork oak forests are extremely well adapted to the semi-arid regions of south- ern Europe and northern Africa (west- ern Mediterranean). These forests help to prevent the advance of desertification, improve water penetration into the soil and hydrological regulation, promote soil conservation, and being the perfect habi- tat for many animal and vegetables species. Consequently, these forests promote biodi- versity (Pereira, 2007; Gil, 2011, 2014). the extraction. During the tree lifetime in operation, an average cork oak produces about four times more cork bark than the cork tree would produce if it were not sub- ject to stripping. The sum of the various layers of cork produced and harvested is greater than the single layer of cork pro- duced if there was no extraction during the life of a tree (Gil, 1998, 2011). Related to environmental aspects of the transformation of the cork raw mater- ial, it can be mentioned the production of expanded cork agglomerate. The man- ufacture of this cork product only uses superheated steam, using generators fueled with cork waste, not introducing any other products not exclusively cork, and giving up agglomeration based on resins of the cork itself. So, this is a completely nat- ural and ecological product. In addition, in the processing of this and other cork products an important residue is produced, cork powder. This powder is commonly burned to produce steam and/or power used in the factories themselves, given the high energy content of this material. Also, all other industrial cork wastes are reused or valorized in another way (Gil, 1998). So, there is really no wasted cork.

Microwave-assisted Liquefaction of Cork - From an Industrial Waste to Sustainable Chemicals

Cork wastes and by-products were used as raw materials to access sustainable biopolyols in a fast and clean manner. Contributing for the mitigation of a residue recorded as industrial residues in the European waste catalogue and hazardous waste list reducing, therefore, its environmental impact. Cork powder resulting from the cork industry as a waste and/or by-products with no commercial value was subjected to liquefaction in 2-ethyl hexanol/DEG in the presence of p-toluene sulfuric acid. Microwave radiation was used as the heating source. Pulsed microwaves from 150-300 W power were applied for 5-20 min. This alternative energy source was successfully applied leading to a high conversion of cork powder into liquid biopolyols. The efficiency of liquefaction increased with higher microwave power and shorter reaction time. This study evidenced that cork powder can be liquidized via microwave. ATR experiments indicated that microwave led to a more intense oxidized cleavage of the lignocellulosic material and more extensive liquefaction reaction when compared to the conventional procedure.

Removal of methyl orange from aqueous solution via adsorption on cork as a natural and low-coast adsorbent: equilibrium, kinetic and thermodynamic study of removal process

In this study, the cork powder was used as adsorbent to remove methyl orange (MO) from aqueous solutions by adsorption. Batch experiments were conducted to study the effect of reaction parameters on the adsorption of the dye such as: contact time, initial concentrations of solution, adsorbent dosage, solution pH, and temperature; consequently, optimum condition of adsorption was obtained. The surface properties and structure of cork were measured by some techniques including: Scanning electron microscope, Fourier transform infrared spectrometry, point of zero charge, and Boehm titration method. Adsorption capacity of cork for MO is 16.66 mg g−1 at 298 K under the optimum condition of pH of 2, cork dosage of 5.00g l−1, particle size of d<0.08 mm, and contact time of 240 min. The kinetic data obtained from different experiments were analyzed using three kinetic models namely pseudo-first-order, pseudo-second-order, and Elovich kinetics models. Among the kinetics models studied, the pseudo-second-order model was the best applicable model to describe the adsorption of MO onto cork. Freundlich and Langmuir models were used to analyze the obtained experimental data. In comparison, Langmuir model was understood to be a better fit for the experimental data than Freundlich model. The value of Gibbs free energy of adsorption (ΔG°) was found to be −14.96 kJ mol−1; the negative value indicated the spontaneity of the adsorption process of MO onto cork. The values of (ΔH°) and (ΔS°) were found to be −11.71 kJ mol−1 and −10.93 J mol−1 K−1, respectively. The thermodynamics parameters indicated that the adsorption of MO onto cork was spontaneous and exothermal.

Functionalized cork-polymer composites (CPC) by reactive extrusion using suberin and lignin from cork as coupling agents

High density polyethylene (HDPE) and cork powder were compounded in a co-rotating twin-screw extruder to obtain cork-polymer composites (CPC) with improved properties. Benzoyl peroxide (BPO) was used as initiator agent, and suberin or lignin isolated from cork enhanced filler-matrix bonding and promoted mechanical reinforcement with environmental benefits. The novel composites were characterised in terms of dimensional stability, evolution of morphology, thermal and mechanical properties and their performance was compared with that of composites containing polyethylene-grafted maleic anhydride (PE-g-MA) as coupling agent. As expected, composites with coupling agent present higher mechanical properties, lower water uptake and thickness swelling variation. Suberin acts as plasticizer with antioxidant benefits, while lignin works as a coupling agent, improving tensile modulus and maximum strength. Increasing lignin content does not improve the mechanical properties but improves thermal stability.