Search Results (37)

This paper presents the development of two solutions for sandwich panels composed of a thin-layer alkali-activated composite (AAc) layer and a thicker insulation layer, formed by extruded polystyrene foam or expanded cork agglomerate (panels named AP_XPS or AP_ICB, respectively). The AAc combined ceramic waste from clay bricks and roof tiles (75%) with ladle furnace slag (25%), activated with sodium silicate. The AAc layer was further reinforced with polyacrylonitrile (PAN) fibers (1% content). The mechanical behavior was assessed by measuring the uniaxial compressive strength of cubic AAc specimens, shear bond strength, pull-off strength between the AAc layer and the insulation material, and the flexural behavior of the sandwich panels. The thermal performance was characterized by heat flux, inner surface temperatures, the thermal transmission coefficient, thermal resistance, and thermal conductivity. Mechanical test results indicated clear differences between the two proposed solutions. Although AP_XPS panels exhibited higher tensile bond strength values, the AP_ICB panels demonstrated superior interlayer bond performance. Similar findings were observed for the shear bond strength, where the irregular surface of the ICB positively influenced the adhesion to the AAc layer. In terms of flexural behavior, after the initial peak load, the AP_XPS exhibited a deflection-hardening response, achieving greater load-bearing capacity and energy absorption capacity compared to the AP_ICB. Finally, thermal resistance values of 1.02 m² °C/W and 1.14 m² °C/W for AP_ICB and AP_XPS were estimated, respectively, showing promising results in comparison to currently available building materials. Full article

The physicochemical and sensory properties of wines are influenced by several factors, starting in the vineyard and evolving during the winemaking stages. After bottling, variables such as bottle position, closure type, storage temperature, and storage time shape wine characteristics. In this study, red wines stored for approximately 0.5 and 3 years with natural cork, micro-agglomerated cork stoppers, and screw cap closures were analyzed. Various techniques were employed to investigate changes during bottle storage, including the determination of volatile components by comprehensive gas chromatography-mass spectrometry with time-of-flight analyzer (GC × GC-ToFMS), phenolic profile by ultra-high-performance liquid chromatography, coupled with tandem mass spectrometry (UHPLC-DAD-MSⁿ), general physicochemical parameters, the oxygen transfer rate of cork stoppers, and sensorial analysis performed by a trained panel. The results revealed that the type of closure created distinct environments within the bottles, slightly influencing both sensory attributes and chemical evolution of the red wines. These findings highlight the value of combining diverse analytical techniques to reveal closure-driven differences, with volatile compound profiling emerging as the most sensitive methodology. Additionally, this study emphasizes that differences modulated by the wine–closure pairing, which become more pronounced during storage, can serve as an oenological tool in the construction of a wine’s identity. Full article

The building sector is responsible for major environmental impacts. Utilising bio-based raw materials, such as bio-aggregates, in concrete production could address to this environmental challenge. While the physical and mechanical properties of various bio-based concretes have been explored, research on their microstructure and resistance to extreme conditions is limited. Cork is a light, renewable and biodegradable material. Cork industries produce a considerable number of solid wastes, among them is granulated cork with bark (GCB) that is not adequate to produce agglomerated cork. To reduce this waste volume, it is possible to use GCB as a bio-based aggregate in the production of concrete for applications in non-structural precast elements that are lighter and/or have thermal properties. The influence of GCB on the microstructure and resistance to extreme conditions of concrete for non-structural use is presented here. Concrete mixes with GCB are compared with a concrete mix made with natural aggregates (RC). Replacements of 20% and 30% of natural aggregate (2–5 mm) by GCB were considered. The microstructure shows the good integration of the GCB in the cement matrix. Freeze–thaw and wet–dry cycle tests do not affect the variation in mass and compressive strength of concrete mixes with GCB in comparison to RC mixes, although they do affect its visual appearance and microstructure somewhat. Concrete mixes with GCB present a greater variation in mass and compressive strength, 30% for RC mix and 43–49% for concrete mixes with GCB, under high temperatures. Concrete mixes with GCB did not show spontaneous combustion. Full article

This study investigates the flexural behavior of three sandwich panels composed of an agglomerated cork core and skins made up of cross-ply [0,90]₂ flax or glass layers with areal densities of 100 and 300 g/m². They are designated by SF100, SF300, and SG300, where S, F, and G stand for sandwich material, flax fiber, and glass fiber, respectively. The three sandwich materials were fabricated in a single step using vacuum infusion with the liquid thermoplastic resin Elium^®. Specimens of these sandwich materials were subjected to three-point bending tests at five span lengths (80, 100, 150, 200, and 250 mm). Each specimen was equipped with two piezoelectric sensors to record acoustic activity during the bending, facilitating the identification of the main damage mechanisms leading to flexural failure. The acoustic signals were analyzed to first track the initiation and propagation of damage and, second, to correlate these signals with the mechanical behavior of the sandwich materials. The obtained results indicate that SF300 exhibits 60% and 49% higher flexural and shear stiffness, respectively, than SG300. Moreover, a comparison of the specific mechanical properties reveals that SF300 offers the best compromise in terms of the flexural properties. Moreover, the acoustic emission (AE) analysis allowed the identification of the main damage mechanisms, including matrix cracking, fiber failure, fiber/matrix, and core/skin debonding, as well as their chronology during the flexural tests. Three-dimensional micro-tomography reconstructions and scanning electron microscope (SEM) observations were performed to confirm the identified damage mechanisms. Finally, a correlation between these observations and the AE signals is proposed to classify the damage mechanisms according to their corresponding amplitude ranges. Full article

The industrial landscape has revealed two trends: increased competitiveness and a greater demand for sustainable solutions. Materials with cork in their composition are an appealing solution, since they guarantee the desired mechanical characteristics while contributing to the prevention of environmental degradation. Given the change in external factors, there has been a substantial rise in energy costs. Thus, it is essential to optimize processes, with the aim of reducing the consumption of resources, such as electricity. This project was developed at a company that manufactures cork blocks, sheets, and rolls. Regarding blocks, a critical operation of this line is the high-frequency heating, being the bottleneck of this work center. With the critical variables previously identified, planned experiments were conducted based on DOE’s full factorial methodology. Two out of four products revealed inputs with statistical significance. With these results, a reduction in parameters was implemented in the factors and interactions that showed no statistical significance. Finally, average and amplitude control charts, based on the SPC methodology, were applied to solidify and guarantee the quality of the agglomerated blocks, with the parameter changes already introduced. The company benefited from this study by having a significant reduction in its energy consumption. Full article

Due to their extraordinary qualities, including fire resistance, excellent crashworthiness, low thermal conductivity, permeability, non-toxicity, and reduced density, cellular materials have found extensive use in various engineering applications. This study uses a finite element analysis (FEA) to model the dynamic compressive behaviour of agglomerated cork to ascertain how its material density and stress relaxation behaviour are related. Adding the Mullins effect into the constitutive modelling of impact tests, its rebound phase and subsequent second impact were further examined and simulated. Quasi-static and dynamic compression tests were used to evaluate the mechanical properties of three distinct agglomerated cork composite samples to feed the numerical model. According to the results, agglomerated cork has a significant capacity for elastic rebound, especially under dynamic strain rates, with minimal permanent deformation. For instance, the minimum value of its bounce-back energy is 11.8% of the initial kinetic energy, and its maximum permanent plastic deformation is less than 10%. The material’s model simulation adequately depicts the agglomerated cork’s response to initial and follow-up impacts by accurately reproducing the material’s dynamic compressive behaviour. In terms of innovation, this work stands out since it tackles the rebounding phenomena, which was not previously investigated in this group’s prior publication, either numerically or experimentally. Thus, this group has expanded the research on cork materials’ attributes. Full article

Façades give the first impression of a structure, reflecting the overall aesthetic appeal, architectural styles, cultural influences, and technological advancements. Emphasis on sustainability is increasing, with a shift towards eco-friendly and energy-saving materials, triggered by decreasing the environmental impact of construction. Cork is a green competitive material for various engineering and design applications due to its biological formation, sustainable production and a portfolio of properties including low density, impermeability, viscoelastic behaviour and high thermal insulation that derive from its cellular and chemical features. This work presents cork materials used in building façades and their properties, also giving information on cork production and processing into cork-based products as a review of the existing published research, while also identifying knowledge gaps and further research needed. Historical examples of cladding of constructions with raw cork are given, while the contemporary innovative use of cork façades was triggered by some designs of well-known architects with outdoor application of expanded cork agglomerates. Examples of different historical and contemporary constructions were assembled and critically assessed by the authors. The aim is to give integrated information of cork as a natural, renewable and sustainable material to raise the interest of designers, architects and engineers to explore cork, blending aesthetics with environmental responsibility, targeting a more sustainable and resilient built environment. Full article

The children’s toy market is increasingly dominated by products that rely heavily on visual appeal. This article presents the development of ‘bumpi’, a cork toy specially developed for young children who experience visual impairments or blindness. Research was conducted about these children’s needs and the existing assistive products for them in the market. This research revealed that they often face developmental challenges, including delays in achieving key milestones such as crawling and walking, which happens because blind and visually impaired children are less confident to moving and exploring. A significant gap in the market for toys and assistive devices for blind young children was identified. Bumpi aims to fill such a gap. It is designed to stimulate and foster the earlier development of motor skills in children between one and five years old, leading to greater independence. This toy enhances sensory experiences through touch and sound to stimulate children’s urge to move. The toy set includes a puzzle-like mat, a toy cart that follows a predefined path, building blocks for constructing a ramp, and sensory balls that emit sounds when they move. Agglomerated cork, chosen for its unique properties such as lightness, durability and its hypoallergenic nature, is the primary material used. Furthermore, it is not only safe and comfortable for children to handle but also offers great stimulation to their senses. In addition, this is a sustainable material that offers several benefits for the toy industry. Full article

The beekeeping sector is increasingly focused on creating optimal and natural environments for honeybees to reduce dependence on external factors, especially given progressively hotter summers. Improving hive thermal conditions can enhance bee wellbeing and production. While pinewood hives are predominant, some have started using insulating materials like polystyrene. However, many synthetic materials, despite their excellent insulation properties, are incompatible with organic food production, requiring alternative solutions. This study compares the thermal insulation properties of various natural materials, including white and black agglomerated cork, wood fibres, and rock mineral wool. These materials are potentially compatible with organic food production. Additionally, the research evaluates cost-effective sensor networks to monitor bioclimatic variables in real time. Lab tests using a Langstroth-type hive with a controlled heat source were conducted, monitoring temperature and humidity inside and outside the hive. The results revealed that all selected materials provided similar thermal insulation, superior to a hive without insulation. This finding suggests that using natural materials can enhance hive thermal comfort (i.e., the material’s ability to maintain a stable internal temperature), thereby improving honeybee wellbeing and productivity in a manner compatible with organic food production. Full article

Agglomerated cork is a natural cork that has gone through a process of crushing and pressing using heat and binders. One of its applications is thermal insulator in construction. The design of these materials is becoming an essential part of building. The raw materials currently used to make insulators consume a large amount of energy, which has created the need to increase the use of renewable and ecological resources such as plant fibers to reduce the environmental problems generated. The objective of this study was to determine the different properties of experimental particleboard panels made from cork and Canary Island date palms without using any binder at minimum energy consumption. The produced cork–palm boards (density of 850 kg/m³, reached a MOR 8.83 N/mm², MOE 794.5 N/mm², and IB 0.38 N/mm²) are higher values than the traditional cork particleboards with UF made from cork. The thermal conductivity values obtained 0.069 to 0.096 W/m·K are higher than cork boards with UF. Ecological boards that can be used as rigid thermal insulators in the construction industry have been achieved to improve the mechanical properties of the traditional agglomerated cork. Full article

This pilot investigation identifies the influence that changing the process variables of curing pressure, curing temperature, and mix ratio of a polyurethane/agglomerated cork matrix has on the mechanical properties of energy absorption, Young’s modulus of elasticity, and spring stiffness in safety helmets intended for micro-transport riders. The results are compared to expanded polystyrene, a material commonly used in micro-transport helmets. Mechanical testing of the various samples found that, over the range tested, curing pressure had no effect on any of the mechanical properties, while increasing amounts of resin caused a stiffer structure, and increasing curing temperature led to increased energy absorption. Consistent with the elastic modulus findings, all polyurethane/agglomerated cork test samples demonstrated higher median levels of spring stiffness, ranging from 7.1% to 61.9% greater than those found for expanded polystyrene. The sample mixed at a 1.5:1 binder/cork ratio and cured at 40 °C displayed the closest spring stiffness to EPS. While the mechanical properties of the eco-friendly polyurethane/agglomerated cork matrix did not match those of expanded polystyrene, the difference in performance found in this study is promising. Further investigation into process variables could characterise this more ecologically based matrix with equivalent energy-absorbing and structural characteristics, making it equivalent to currently used expanded polystyrene and suitable for use in micro-transport helmets. Full article

In the wine bottling process, thermoplastics are commonly used to manufacture the crown of cork stoppers. The production of agglomerated cork stoppers generates a type of waste called cork powder (CoP) in large volumes with known properties but which are still underutilized. At present, although there are many agrocomposites available with additives such as natural fibers or solid residues from agricultural products, there are no studies describing the formation of these agrocomposites from petroleum-derived synthetic plastics combined with cork dust as a reinforcement for the polymeric matrix. The present study describes a novel agrocomposite, which has been obtained by mixing polypropylene-type materials, as they are some of the most widely used and versatile thermoplastics, with cork dust, which is a waste product obtained from the cork industry. The composite is obtained directly, without the need for grafting, adhesive polymers, or coupling agents. A superior mechanical performance compared to the unprocessed polymer was highlighted in the test results, thus evidencing the reinforcing function played by the waste in the polymer matrix. Therefore, this novel agrocomposite could be a promising alternative to replace some petroleum-derived synthetic plastics, which are currently experiencing high demand. The use of this new agrocomposite is well aligned with sustainability strategies, the principles of the circular economy, and oriented towards the fulfilment of the Sustainable Development Goals required by the European Union, considering that it contributes (a) to recycling agricultural waste that would otherwise be difficult to recover and valorize; (b) to the reduction in the CO₂ footprint; and (c) to promoting the use of high-quality secondary raw materials. Full article

Cork composites are byproducts from wine stopper production, resulting from the agglomeration of cork granules with a thermoset resin. The resulting compound is a versatile and durable material with numerous industrial applications. Due to its unique properties, such as low-density, high-strength, excellent energy absorption, and good thermal and acoustic insulators, cork composites find room for application in demanding industries such as automotive, construction, and aerospace. However, agglomerated cork typically has a polyurethane matrix derived from petrochemical sources. This study focuses on developing eco-friendly porous polyurethane biocomposites manufactured with the used cooking oil polyol modified with cork. Since cork and polyurethane foam are typically used for impact shock absorption, the manufactured samples were subjected to impact loading. The assessment of crashworthiness is performed through 100 J impact tests. A finite element numerical model was developed to simulate the compression of these new composites under impact, and the model validation was performed. The highest specific absorbed energy was obtained for petrochemical polyol composites with the 3% addition of natural or modified cork. The research conducted in this study showcased the feasibility of substituting certain petrochemical components used for the synthesis of the polyurethane matrix with ecological waste vegetable oil components. Full article

Insulation materials are fundamental for decreasing energy losses and guaranteeing thermal and acoustic comfort in buildings, which may significantly contribute to decreasing the energy consumption related with poor thermal building conditions. These insulation materials should have a low susceptibility to biological degradation agents to decrease the risks of degradation of other construction materials, as well as decrease possible health risks related with the development of noxious biological degradation agents regarding indoor air quality, for example, or decrease possible structural risks posed by those agents. The present study aimed at evaluating the susceptibility of several insulation materials to mold growth and subterranean termites’ attack. Insulation materials, including expanded polystyrene (EPS), mineral wool (MW), and expanded cork agglomerate (ICB), were tested against mold development, using maritime pine as a control. Three types of inoculations were made: (1) natural indoor inoculation; (2) artificial inoculation using Aspergillus niger and Penicillium funiculosum; and (3) artificial inoculation using Aureobasidium pullulans. The susceptibility of the insulation materials referred to, plus wood/glass fiber (WGF), was evaluated for two subterranean termite species: Reticulitermes grassei and Reticulitermes flavipes. The expanded cork agglomerate showed a higher susceptibility to molds than the other insulation materials tested. The remaining materials revealed a good performance, showing no growth or traces of growth of molds. All the materials tested showed susceptibility to subterranean termites, with both species being able to cross them to obtain access to the wood. However, wood/glass fiber showed a negative effect, which translated into lower survival rates and attack degrees of the wood. Some tested materials showed a good resistance to the development of biological degradation agents, namely an organic material (coconut fiber), a composite of organic and inorganic materials (WGF), and an inorganic material (EPS). These results indicate that it is possible to pursue the development of innovative and effective insulation materials with a low susceptibility to biological degradation agents, regardless of their organic or inorganic origin. Full article

Flavour scalping in wine is a well-known phenomenon that is defined as the sorption of flavour compounds on wine closures. While the impact of closure type was the object of several studies, no research has addressed the impact of wine closure permeability on flavour scalping. For that purpose, the adsorption of volatile sulphur compounds (VSCs) on four micro-agglomerated wine cork closures was investigated by soaking them in model and Shiraz wines for 7 days. From a kinetic point of view, most of the VSCs were quickly scalped after 1 h of soaking, and this effect increased after 6 h until reaching a plateau. Most importantly, no significant impact of the closure on the kinetics and adsorption rates of the VSCs was found. As to the quantitative aspects, VSC sorption on closures accounted for 1% to 5% of the initial VSCs present in the wines only, meaning that the impact was negligible under oenological conditions. Full article