A Study on the Density of Agglomerates Prepared from Cork Wastes

The density of black regranulate (BR) of cork and of black agglomerate (BA) and composite agglomerate (CA) prepared fromsuch a waste by different methods was investigated. The preparation of the agglomerates was undertaken by controlling thespecimen thickness for BA and the particle size for BR and the binder dosage for CA. The mass changes produced in theoven-drying treatment at 376.15 K of the agglomerates and in their subsequent stabilization under ambient conditions werealso analyzed. The density was determined by standard methods. For BR, the bulk density first decreased and then increasedwith decreasing particle size. It was much lower than the apparent density of the agglomeration products of cork. Although toa lesser extent, the density was also lower for BA than for CA. It was higher for the smaller thickness specimens of BA. In thecase of CA, the density followed the same variation trends as for BR. Furthermore it increased significantly with the increasein resin dosage. This resulted in a not     

陶瓷粉末中团聚体结构表征的研究

团聚体结构通常用团聚系数来表征,团聚系数(AF)被定义为:团聚体的平均尺寸与基本颗粒尺寸之比值。每个团聚体都由实体部分—基本颗粒,空心部分—基本微粒之间的空隙两部分构成。团聚系数只表征了团聚体与构成它的基本微粒之间的关系。因而定义另一参数来表征团聚体结构中的空隙部分是非常有必要的。本文提出“孔系数”这一参数。孔系数(PF)被定义为:每克粉料中聚团内的气孔数与聚团数中之比值。PF 值由PF=(ρ_αV_pD~3/8r~3)×10~9推导。各种不同的氧化锆粉末是在不同热处理条件下处理氢氧化物而得到的。孔系数是根据离心沉降分析、压汞测孔的结果,经分析计算而得出。在粉末锻烧过程中,随着煅烧温度的提高和保温时间的延长(煅烧温度一定)孔系数降低。这种变化趋势可以经 TEM 观察到的结果得以证明。     

Elucidation of the capillarity-promoted sintering of silver nanoparticles produced by a spark ablation vapor source

Through the spark ablation method, high purity, spherical silver nanoparticles (Ag NPs) with a size of 5 ± 3 nm are prepared. A solvent-assisted sintering method is developed to modulate the sintering structure and properties of the as-prepared Ag NPs. The effects of the solvents terpineol, polyethylene glycol-200, 1,2-propanediol, and ethylene glycol are explored. The results show that treatment with ethylene glycol causes the shear strength of the sintered Ag NPs at 180, 220, 260, and 300 °C to significantly improve from 0, 3.7, 22.1, and 64.6 MPa to 37.1, 56.1, 76.6, and 93.1 MPa respectively. Additionally, the size and number of voids in the sintered structure are significantly reduced. From the perspective of the capillary pressure induced by the solvent during sintering, a correlation between low solvent wettability and small agglomerate size of the Ag NPs is revealed, which reasonably explains the structure and properties of the sintered Ag NPs that were treated with different solvents. The spark ablation and solvent-assisted sintering methods provide a new approach for the fabrication and structure–property design of metal NPs for electronic applications.     

Shear-induced APAP de-agglomeration

Context: Active pharmaceutical ingredient agglomerates can generate many solid product regulatory compliance issues. Objective: To study the effects of shear rate, strain, type of excipient, and grade of acetaminophen (APAP) on the process of APAP de-agglomeration. Materials and Methods: A shear-controlled environment is used to expose six different blends that consist of one of three APAP grades and one of two possible types of excipient to 10 different combinations of shear rate and strain. APAP agglomerates are sifted and weighed. Results: Finer APAP grades lead to blends with more APAP agglomerates and type of excipient only affects the de-agglomeration process for the finest APAP grade. De-agglomeration proceeds mainly as a function of strain with a minor contribution toward further de-agglomeration when larger shear rates are used. Discussion: When mechanical stress (which us proportional to shear rate) overcomes interparticle forces, de-agglomeration occurs. Higher shear rates (and stress) contribute slightly to further APAP de-agglomeration. Extended exposure to stress (strain) reduces the size and the number of agglomerates. Blends with finer APAP present more agglomerates, particularly after low strain exposure. Conclusions: This article presents a useful method for formulation and process development. Exposing blends to higher shear rates and especially to strain mitigates APAP agglomeration in blends. Finer APAP presents more agglomerates and the type of excipient used affects the degree of APAP agglomeration.     

Surface treatment of indomethacin agglomerates with eudragit

Indomethacin is a widely used anti-inflammatory drug with serious side-effects. This drug was used as a model drug for the coating of agglomerates with a permeable film (Eudragit NE). The agglomeration of the crystals increased the flowability of the bulk crystals. The coating further improved the flowability, and also the uniformity of the mass of the filled capsules. The coating film also influenced the wetting of the samples. The coating decreased the surface free energy and therefore reduced the adhesion forces between both the dry and the wet particles. The modification of the flow properties and the even capsule filling can be explained by this phenomenon. Since coating film does not dissolve in the artificial gastric juice, the dissolution test was performed only in the artificial intestinal juice. The dissolution of indomethacin from the coated sample was changed significantly. Accordingly, coating of the crystals can be performed in order to protect the mucosa of the gastrointestinal tract or to promote the preparation of solid dosage form.     

Computer vision and robotic manipulation for automated feeding of cork drillers

The production of cork stoppers is currently a process in rapid evolution. Where in the past hand labor was common, today we observe increasing attempts to introduce technologies that increase the productivity of production lines. One these example are automated cork drillers that produce thousands of cork stoppers per hour. In order to harness this increase in productivity to its full potential, it must the followed by other processes in the production line upstream of the driller, as for example the feeding of the latter.This article presents the application of computer vision techniques that extract information of cork strips that move on a conveyor belt, to obtain automated feeding of a cork driller using a robotic manipulator. Image Processing extracts information regarding the strip position and orientation, and also which side of the strip is visible. Thus the strip is consistently placed in the driller in order to extract stoppers from the best quality cork. The segmentation of the cork strips is obtained by background subtraction. To estimate the strip visible surface, we apply Machine Learning techniques that enable a robust classification given a set of features extracted from the cork texture.In the experiences carried out, we were able to obtain 100% classification rate with a test dataset of more than a hundred cork strips.     

Cork agglomerates as an ideal core material in lightweight structures

The experiments carried out in this investigation were oriented in order to optimize the properties of cork-based agglomerates as an ideal core material for sandwich components of lightweight structures, such as those used in aerospace applications. Static bending tests were performed in order to characterize the mechanical strength of different types of cork agglomerates which were obtained considering distinct production variables. The ability to withstand dynamic loads was also evaluated from a set of impact tests using carbon-cork sandwich specimens. The results got from experimental tests revealed that cork agglomerates performance essentially depends on the cork granule size, its density and the bonding procedure used for the cohesion of granulates, and these parameters can be adjusted in function of the final application intended for the sandwich component. These results also allow inferring that optimized cork agglomerates have some specific properties that confirm their superior ability as a core material of sandwich components when compared with other conventional materials.     

CorkSTFμfluidics – A novel concept for the development of eco-friendly light-weight energy absorbing composites

CorkSTFμfluidics are environmentally friendly composites consisting of a laminar sheet of compacted micro-agglomerated cork engraved with a network of microchannels by laser and filled with a concentrated aqueous solution of cornstarch (shear thickening fluid). Thus the mechanical properties of these composites will result from the combination of the mechanical properties of the micro-agglomerated of cork and the enhanced shear thickening response of the STF flowing through the network of microchannels. In this work we have performed low velocity impact tests using a drop weight testing machine in order to asses the improvement of these composites with regards to the micro-agglomerated of cork alone. A numerical analysis was also performed and allowed to understand how shear thickening behavior is triggered by the appropriate combination microchannels’ size and the inlet velocity. Thus, for the 60P/40S/M sample, the peak force was larger than the one given by the cork sheets without engraved microchannel nor STF.     

Preparation of a Cation Exchanger from Cork Waste：Thermodynamic Study of the Ion Exchange Processes

An ion exchanger was prepared by sulfonation of cork-waste chars. The exchange properties of the resultant material were characterized using Na+, Ca2+ or Fe3+ aqueous solutions. The content of metal ions in the solutions were determined by atomic absorption spectrometry. On the basis of the results obtained, the chemical equilibrium and its thermodynamic aspects related to the ion exchange process were studied. It was found that equilibrium constant K varies by the order: Na+0 and △5°>0, with -△G° following the sequence: Ca2+>Na+>Fe3+.     

Cork–polymer biocomposites: Mechanical,structural and thermal properties

This work addresses to the preparation of biocomposites resulting from the combination of different biodegradable aliphatic polyesters with cork (30 wt.%). The lignocellulosic biomass with closed cellular structure was compounded with poly(L-lactic acid) (PLLA), polyhydroxybutyrate-co-hydroxyvalerate (PHBV), poly-ε-caprolactone (PCL) and starch-poly-ε-caprolactone (SPCL) blend using a twin-screw extruder prior to injection moulding into tensile samples. The physico-mechanical and thermal properties of the matrices and the bio-based cork composites were investigated. This study shows that the addition of cork contributes to produce lightweight materials using PLLA and PHBV matrices and promotes an increase on the stiffness of PCL. The fracture morphology observations showed good physical cork–matrix bonding with absence of voids or cavities between cork and the bio-based polyesters. Cork increases the crystallinity degree of the biocomposites. These findings suggest that the cork–polymer biocomposites are a viable alternative to develop more sustainable composite materials, such as automotive interior parts and bio-based caps for wine bottles as it has been shown as proof-of-concept.     

Mechanical properties of cork: Effect of hydration

Cork is known to exhibit low permeability to liquids and gases, imputrescibility and good mechanical properties, with a remarkable elasticity. These properties make this material particularly interesting for sealing wine. We focused in this study on the compression properties of cork along the radial and tangential direction at 25 °C under atmospheric pressure when cork is stored in various relative humidity environments, from 0% to 100%.The direction of compression significantly affected the Young’s modulus, with a higher value for the radial direction. This corresponds to the orientation of the lenticels which reinforce the rigidity of the material when the strain is applied along their growth direction. More surprising is the effect of water sorption in cork on its mechanical property. Both radial and tangential directions exhibit the same behavior when the relative humidity is increasing. First the Young’s modulus is constant up to 50% relative humidity (RH) with mean values around 37 MPa and 22 MPa for radial and tangential directions, respectively. Then, above this point, the increase in water content leads to a decrease in material rigidity which is attributed to water clusters formations. For high moisture contents, the anisotropy of cork is reduced: Young’s moduli are of 10.5 MPa and 6.6 MPa for radial and tangential orientations, respectively.Differential scanning calorimetry and dynamic mechanical thermal analysis (DMTA) allowed to identify a glass transition temperature (T_g) in cork over a broad range of temperatures, depending on the moisture content and giving a T_g-midpoint from −8 °C to 3 °C. Moreover, a secondary transition was observed by DMTA at approximately −80 °C, for 50% RH.     

Prediction of mechanical strength of cork under compression using machine learning techniques

In this study, the accuracy of mathematical techniques such as multiple linear regression, clustering, decision trees (CART) and neural networks was evaluated to predict Young’s modulus, compressive stress at 30% strain and instantaneous recovery velocity of cork. Physical properties, namely test direction, density, porosity and pore number, as well as test direction were used as input. The better model was achieved when a classification problem was performed. Only compressive stress at 30% strain can be predicted with neural networks with an error rate of about 20%. The prediction of Young’s modulus and instantaneous recovery velocity led to unacceptably high error rates due to the heterogeneity of the material.     

Properties of new cork–polymer composites: Advantages and drawbacks as compared with commercially available fibreboard materials

Cork powder (50 wt.%) was mixed with polypropylene (PP) or polyethylene (PE) by pultrusion aiming to prepare cork-based composites. In a further step, samples were produced by compression moulding using the compounded composites. Bending strength, impact resistance, hardness, dimensional stability, thermal and acoustic properties of the developed cork–polymer composites (CPC) were determined and compared with commercially available products namely medium density fibreboard (MDF) and high density fibreboard (HDF). It was found that the CPC have good dimensional stability, lower water uptake, a better acoustic insulation performance and similar behaviour in terms of hardness and fire resistance when compared with both MDF and HDF. However, the mechanical strength is inferior comparing with both commercial materials based on fibres. It was also observed that addition of cork improved the flexural modulus, impact resistance and hardness on the developed CPC. Thus, the herein described CPC materials showed important characteristics to be considered as good candidates to be applied in the design of flooring and construction systems.     

四种氧化锆细粉制造工艺的特点和粉料性能

以氧氯化锆(ZrOCl_(?)·8H_2O)为原料,选择了四种工艺(热分解法、溶液蒸发分解法(EDS 法)、沉淀—分解法、尿素法)制造氧化锆细粉,并进行了对比研究。四种工艺制备的氧化锆粉料的比表面都>20m~2/g,其中以沉淀—分解法所制得的粉料最细。四法制备的粉料都有明显的团聚结构,其中 EDS 法制得粉料的团聚体为空心球,其余三种粉料的团聚体为形状不规则的实心体。用沉淀—分解法制取的粉料中的团聚体最坚固,而尿素法制备的粉料中的团聚结构较易破坏。用沉淀—分解法制备易保证粉料的纯度,而 EDS 法则因废气腐蚀设备而易带进杂质。     

静力称量法测量重液密度计

本文介绍静力称量法测量重液密度计的测量原理和方法,并与直接比较法测量结果进行了比较。静力称量法测量重液密度计可以节约测量成本,提高测量效率,避免环境污染及有毒液体对工作人员的侵害。     

Effect of moisture content on curing kinetics of agglomerate cork

The curing process of Toluene 2,4-DiIsocyanate (TDI) pre-polymer with granulate cork is significantly affected by the cork moisture content since the reaction of isocyanate is highly sensitive to water. Two types of moisture are considered: the moisture contained inside the granulate cork, residual moisture, and the moisture intentionally sprayed over the granules of cork, added moisture. This study analyses the curing kinetics of TDI and granulate cork mixtures containing added moisture using Differential Scanning Calorimetry (DSC), and the reaction rate increase associated with the added moisture content (AMC). The underlying objective of this work is to reduce the time needed to obtain agglomerate cork stoppers through AMC increase.     

Ozone and membrane filtration based strategies for the treatment of cork processing wastewaters

The degradation of the pollutant organic matter present in the cork processing wastewater was studied by combining chemical treatments, which used ozone and some Advanced Oxidation Processes, and membrane filtration procedures. Two schemes were conducted: firstly, a single ozonation stage followed by an UF stage; and secondly, a membrane filtration stage, using different MF and UF membranes, followed by a chemical oxidation stage, where ozone, UV radiation, and the AOPs constituted by ozone plus UV radiation and ozone plus hydrogen peroxide, were used. The membrane filtration stages were carried out in tangential filtration laboratory equipment, and the membranes used were two MF membranes with pores sizes of 0.65 and 0.1microm, and three UF membranes with molecular weights cut-off of 300, 10, and 5kDa. The effectiveness of the different stages (conversions in the chemical procedures and rejection coefficients in the membrane processes) were evaluated in terms of several parameters which measure the global pollutant content of the wastewater: COD, absorbance at 254nm, tannins content, color, and ellagic acid. In the ozonation/UF combined process the following removals were achieved: 100% for ellagic acid and color, 90% for absorbance at 254nm, more than 80% for tannins, and 42-57% for COD reduction. In the filtration/chemical oxidation combined process, 100% elimination of ellagic acid, more than 90% elimination in color, absorbance at 254nm and tannins, and removal higher than 80% in COD were reached, which indicates a greater purification power of this combination.