Fast Drying Research Articles

Incrustation of wet dirt on glass surfaces through convective drying

The macroscopic and microscopic structural patterns formed during the convective drying of aqueous suspensions of dirt (mixture of dust, salt and water) on glass surfaces are investigated. The effects of dust size distribution, convective airflow temperature and velocity on the morphology of the deposited dust aggregates and salt crystals are studied. The critical removal forces necessary to leave behind a clean surface is experimentally determined. Drying at high temperature would cause a strong evaporation rate gradient leading to formation of salt rings and “cauliflower growths”, while drying at low temperature results in large individual crystals. The critical removal forces also correlate to these deposition patterns with the more raised structures requiring the lowest removal force. The strongest adhesive contacts are observed for samples with smoother morphology. The latter usually forms at high level of salt supersaturation (fast drying) in the presence of dust particles.

Synthesis and characterization of castor oil-based branched polyols from renewable resources and their polyurethane-urea coatings

The chemical modifications of castor oil (CO) to develop branched polyols and their polyurethane-urea coatings have been investigated. For this purpose, castor oil-based branched polyols (COBPs) were synthesized from CO by modifying with succinic anhydride followed by reaction with hydroxyl group moieties like petrochemical-based pentaerythritol, trimethylolpropane and bio-based glycerol. The COBPs were characterized by using Fourier transform infrared, 1H and 13C nuclear magnetic resonance spectroscopies, gel permeation chromatography and differential scanning calorimetry. These COBPs were further urethanized with isophorone diisocyanate at OH/NCO ratio of 1:1.6 to get the isocyanate-terminated polyurethane prepolymers. The surplus isocyanate groups of the prepolymer were cured with atmospheric moisture at ambient temperature condition to form uniform film with fast surface drying. The thermo-mechanical, viscoelastic and swelling properties were evaluated for the cured coating films. Properties have been discussed from the viewpoint of branched network and also the urethane segment present in the structure. The glass transition temperatures of the coating films were found to be in the range of 32–64°C. The modified castor oil coating films show better thermo-mechanical and viscoelastic properties in comparison with control (unmodified castor oil) coating films. This work delivers an effective and promising way to synthesize branched moieties in plant oil-based high performance coatings.

Impact of fast and slow desiccation on Garcinia imberti seed and seedling vigour

Garcinia imberti Bourd. endemic to the southern Western Ghats is classified as endangered by the IUCN (2018). The seeds as the sole means of propagation with initial moisture content (MC) of 62.8% are sensitive to desiccation. Studies on the responses of the seed to drying require ascertaining of the critical moisture content (CMC) as a basic requisite for germplasm conservation. Responses of G. imberti seeds to fast drying with activated silica gel (25 ± 2 °C, 6 ± 1% RH) and to slow drying under laboratory conditions (28 ± 2°C, 60 ± 2% RH) were evaluated for seed and seedling vigour. When the MC was reduced to 56% by 48 hours of slow drying or 6 hours of fast drying, 75 to 90% normal seedlings were produced respectively. In the case of fast dried seed (6 hours), seed associated parameters except mean germination time showed peak values with maximum germination and enhanced root length. Below the CMCs of 16.4 and 26.3% (fast and slow drying respectively), half of the tested seeds become non viable. Thus for germplasm conservation the present study proposes 6 hour’s of fast drying to retain viability and normal seedling development of G. imberti.

Thickness Characterization Toolbox for Transparent Protective Coatings on Polymer Substrates.

The thickness characterization of transparent protective coatings on functional, transparent materials is often problematic. In this paper, a toolbox to determine the thicknesses of a transparent coating on functional window films is presented. The toolbox consists of a combination of secondary ion mass spectrometry and profilometry and can be transferred to other transparent polymeric materials. A coating was deposited on designed model samples, which were characterized with cross-sectional views in transmission and in scanning/transmission electron microscopy and ellipsometry. The toolbox was then used to assess the thicknesses of the protective coatings on the pilot-scale window films. This coating was synthesized using straightforward sol-gel alkoxide chemistry. The kinetics of the condensation are studied in order to obtain a precursor that allows fast drying and complete condensation after simple heat treatment. The shelf life of this precursor solution was investigated in order to verify its accordance to industrial requirements. Deposition was performed successfully at low temperatures below 100 °C, which makes deposition on polymeric foils possible. By using roll-to-roll coating, the findings of this paper are easily transferrable to industrial scale. The coating was tested for scratch resistance and adhesion. Values for the emissivity (ε) of the films were recorded to justify the use of the films obtained as infrared reflective window films. In this work, it is shown that the toolbox measures similar thicknesses to those measured by electron microscopy and can be used to set a required thickness for protective coatings.

Drying characteristics of hui ink at 25 °C and 35 °C

Temperature and humidity are the main factors affecting the drying of Hui ink. For the experiment, fresh Hui ink billets from two big ink industries were selected. We tried to find the fast and efficient drying conditions of Hui ink and calculate effective diffusion coefficient by performing manual control of temperature and relative humidity (RH). Several dry kinetic models were fitted. A constant temperature incubator was utilized for temperature control, while humidification and dehumidification were implemented accordingly for RH control. Setups of 25 °C and 35 °C were designed, and a relative humidity of 60%, 65%, 70%, and 75% was applied for each temperature. The process of ink drying was recorded, and the drying effect of Hui ink was estimated through expert decision. The appropriate drying temperature and humidity of the Jinbuhuan(J) and Huangshansongyan(H) ink billets from Lao Hu Kai Wen Ink Industry are at (31.99 ± 1.41) °C and (55.84 ± 10.38)% RH, whereas those of the Songyantanhei(ST), Chunyouyan(CY), and Quansongyan(QS) ink billets from Ju Mo Tang Ink Industry are at (23.70 ± 2.19) °C and (60.56 ± 2.16)% RH or (34.56 ± 2.37) °C and (59.16 ± 6.38)% RH; Initial moisture content of Hui ink has great influence on the water loss in the drying process; The effective diffusion coefficient of the ink lump ranges from 8.41538E-07 to 1.95891E-06 m2·s−1, and increases mainly with the temperature’s rising; Logarithmic model fits best of the chosen models.

Acrylic white paint of industrial sector for cool roofing application: Experimental investigation of summer behavior and aging problem under Mediterranean climate

The paper proposes a complete experimental characterization of an acrylic white paint, widespread in the field of household appliances or automotive sector. This paints has been already studied by means of in-lab tests; results have suggested that it is suitable for cool roof application.In this study, the results of a measurement campaign are discussed; it has been carried out by means of test-room of the University of Sannio, in Benevento city, under Mediterranean climatic conditions starting from the summer 2016 until the summer 2017. In detail, the in-field monitoring concerns: all data for describing indoor and outdoor climatic conditions; the measure of solar reflectance at start and after one year from paint’s application; the indoor and outdoor surface temperatures, the heat flux; optical investigations in visual and infrared field. The proposed paint has been compared with a commercial cool roof product and with a polished aluminum varnish in term of improvement respect to traditional dark bituminous membrane. Also the in-field aging effect is studied to compare degradation of proposed paint and commercial cool paint.Data elaborations bring to interesting conclusions; first of all, the in-field performance of acrylic paint is comparable to cool product and it is better than aluminum paint. Proposed product shows very fast drying, good gloss and appearance, lower application time and positive economic analysis. However, the aging is faster with in-field reduction of solar reflectance of around 20–25%. It could be due to application technique and to adopted product to favor the adhesion. This makes suitable other researches also for evaluate the application of a protective gloss that could assure greater durability than traditional product.

Binder migration during drying of lithium-ion battery electrodes: Modelling and comparison to experiment

The drying process is a crucial step in electrode manufacture that may lead to spatial inhomogeneities in the distribution of the electrode components resulting in impaired cell performance. Binder migration during the drying process, and the ensuing poor binder coverage in certain regions of the electrode, can lead to capacity fade and mechanical failure (e.g. electrode delamination from the current collector). A mathematical model of electrode drying is presented which tracks the evolution of the binder distribution, and is applicable in the relatively high drying rates encountered in industrial electrode manufacture. The model predicts that constant low drying rates lead to a favourable homogeneous binder profiles, whereas constant high drying rates are unfavourable and result in accumulation of binder near the evaporation surface and depletion near the current collector. These results show strong qualitative agreement with experimental observations and provide a cogent explanation for why fast drying conditions result in poorly performing electrodes. Finally, a scheme is detailed for optimisation of a time-varying drying procedure that allows for short drying times whilst simultaneously ensuring a close to homogeneous binder distribution throughout the electrode.

Enhanced bioactivity of a rapidly-dried sol-gel derived quaternary bioglass

Novel quaternary (67Si-24Ca-10Na-8P) glass powders were successfully synthesised by sol-gel followed by two alternative drying schedules, conventional drying (CD) and an innovative fast drying (FD) process (200 times quicker). The glasses were thermally stabilised at 550 °C, and then characterised by different complementary techniques. The samples showed very similar silica network structures, with the FD one having slightly lower degree of polymerisation than the CD sample. This less polymerised, more open, network structure exhibited an improved bioactivity in simulated body fluid (SBF), probably also due to the apparent presence of poorly crystalline HAp in the stabilised glass powder. In contrast, the CD glass exhibited an unwanted secondary crystalline silica phase. Both glasses showed excellent biomineralisation upon immersion in SBF, being more pronounced in the case of FD with clear evidence of HAp formation after 4 h, while equivalent signs in the CD samples were only noticed after longer immersion periods between 8 h and 1 week.

Dry-air drying at room temperature - a practical pre-treatment method of tree leaves for quantitative analyses of phenolics?

In ecological experiments, storage of plant material is often needed between harvesting and laboratory analyses when the number of samples is too large for immediate, fresh analyses. Thus, accuracy and comparability of the results call for pre-treatment methods where the chemical composition remains unaltered and large number of samples can be treated efficiently. To study if a fast dry-air drying provides an efficient pre-treatment method for quantitative analyses of phenolics. Dry-air drying of mature leaves was done in a drying room equipped with dehumifier (10% relative humidity, room temperature) and results were compared to freeze-drying or freeze-drying after pre-freezing in liquid nitrogen. The quantities of methanol-soluble phenolics of Betula pendula Roth, Betula pubescens Ehrh., Salix myrsinifolia Salisb., Picea abies L. Karsten and Pinus sylvestris L. were analysed with HPLC and condensed tannins were analysed using the acid-butanol test. In deciduous tree leaves (Betula, Salix), the yield of most of the phenolic compounds was equal or higher in samples dried in dry-air room than the yield from freeze-dried samples. In Picea abies needles, however, dry-air drying caused severe reductions in picein, stilbenes, condensed tannin and (+)-catechin concentrations compared to freeze-drying. In Pinus sylvestris highest yields of neolignans but lowest yields of acetylated flavonoids were obtained from samples freeze-dried after pre-freezing. Results show that dry-air drying provides effective pre-treatment method for quantifying the soluble phenolics for deciduous tree leaves, but when analysing coniferous species, the different responses between structural classes of phenolics should be taken into account.

Biomechanical properties of aquatic plants: The effect of test conditions

AbstractFour aquatic plants (i.e.,Potamogeton pectinatusL.,Potamogeton crispusL.,Myriophyllum spicatumL., andCeratophyllum demersumL.) that commonly grow in European lowland rivers and lakes and exhibit a variety of morphologies and differences in the internal structures of their stem cross sections were selected to investigate the influence of initial conditions on biomechanical tests. A new method of sample testing in wet conditions is proposed and employed using a bench‐top testing machine. The obtained biomechanical characteristics, such as breaking strain, force, and stress; Young's modulus; flexural strain; flexural rigidity; and flexural modulus are presented and discussed. Even when fresh specimens were kept in water before testing in air, their biomechanical parameters were sensitive to fast drying. If the turgor pressure was not maintained in dry tests, specimen stiffness was not preserved and the measured biomechanical properties deviated from those observed in wet conditions. Approximately 43% of the three‐point bending tests and 20% of the tension tests showed significant differences between dry and wet conditions in all considered plant species. Bending tests for both conditions performed onP. pectinatusL. andP. crispusL. showed the highest differences in flexural rigidity values, reflecting the adaptation of these plants to changing hydraulic conditions. Stem resistance to tension forces in terms of Young's modulus was found to be different for wet and dry conditions only forP. pectinatusL. Overall, it was revealed that plants constantly submerged in water tend to be stiffer than plants exposed to dry conditions.

Investigation of non-linear drying shrinkage for end-restrained shotcrete of varying thickness

Tunnels in hard, jointed rock are commonly reinforced with shotcrete (sprayed concrete) applied directly on the irregular rock surface. The thickness for such linings can be as small as 50 mm, which result in a fast drying. The resulting shrinkage of the restrained lining is a well-known phenomenon, which leads to cracking. The installation of drainage systems also results in an end-restrained shotcrete lining that is more prone to shrinkage cracking. The drying process is a complex problem that depends on multiple factors such as cement content, porosity and ambient air conditions (i.e. temperature, relative humidity and wind speed). Two numerical models capable of capturing the structural effects of drying shrinkage were compared in this study. It was found that inclusion of non-linear drying shrinkage is important for accurately describing crack initiation in an end-restrained shotcrete slab. The best fit to the experimental data was obtained when the rate of drying was described as a non-linear decreasing function.

Effects of Hasten Drying and Storage Conditions on Properties and Microstructure of Konjac Glucomannan-Whey Protein Isolate Blend Films

Impact of drying process and storage conditions on properties of konjac glucomannan (KGM) and whey protein isolate (WPI) blend films was investigated. Hundred grams of film solution contained 0.4 g KGM, 3.8 g WPI and 1.5 g glycerol. During drying process, air velocity was varied to produce fast drying (3 h) and slow drying (15 h) in tray dryers under 50 °C. The high air velocity resulted in a significant higher drying rate in fast drying than low air velocity in slow drying. Drying curves from both processes were well-fitted with Page model and Henderson and Pabis model (R2 ≥ 0.98). Fast drying improved transparency and mechanical properties without impairing color, solubility or water vapor permeability (WVP). Fast-dried film had less surface roughness and contained larger protein clusters. It also had greater melting enthalpy of protein aggregates, implying stronger networks. For stability study, fast-dried film was stored at 4-35 °C for 24 days. Transparency decreased over time. Overall mechanical properties have improved during storage. Color, solubility and WVP did not significantly change over time at all conditions (p > 0.05). Microstructure of aged films was relatively similar to that of the freshly prepared film. Overall, the fast-dried KGM-WPI film exhibited reasonable storage stability.

Fast drying of cut tobacco in drop tube reactor and its effect on petroleum ether tobacco extracts

ABSTRACTEntrained flow drying is an important fast drying tool in tobacco industry. This study used a drop tube reactor (DTR) as an entrained flow dryer to investigate drying process of flue-cured cut tobacco. Lab-scale cold and hot DTRs were set up to obtain drying kinetics for three types of cut tobacco using different drying gases and temperatures. The effective diffusion coefficients of cut tobacco in DTRs were compared with those in a general cylinder dryer. Moreover, the effects of different drying gases and temperatures on petroleum ether extract content were investigated. The results showed that the effective diffusion coefficients of cut tobacco in the DTRs were between 2.296 × 10−8 and 8–6.244 × 10−8 m2/s, which are two orders of magnitude higher than those in the cylinder dryer. Compared to hot air as a drying medium, superheated steam improved the effective diffusion coefficient of cut tobacco. The petroleum ether tobacco extract had a higher retention ratio when the superheated steam was used in the DTRs. An increase in the drying temperature resulted in a lower retention of the petroleum ether tobacco extract.

Experimental and numerical evaluations on the energy penalty of reflective roofs during the heating season for Mediterranean climate

During the cooling season, the beneficial effects of cool colors and cool paints are multiple and undebatable. Really, it is not well-know their impact during the heating season, when a heated external surface could be useful in order to reduce the heat losses.This paper, by means of experiments and numerical simulations, investigates the effect of high-reflective and high-emissive coatings on the building energy performance in Mediterranean climate. Four coatings are used; among these, an acrylic white paint of household appliances or automotive sector has been tested since it is characterized by very fast drying, good adhesion directly to different type of materials, greater durability than traditional paints and lower costs.The experiments have been carried out by using the test-room of the University of Sannio; the results of wintertime monitoring campaign are presented. By means of simulations, using as case study a typical office building, the effect of combination of roof reflectivity, roof technology and insulation thickness is discussed.Research results can support design strategies for optimizing the yearly energy performance of the building, reducing environmental impacts but these also demonstrate the performance of unconventional cool material, as the acrylic paint, with a lower aging and maintenance needs.

Survival of Amazonian Tadpoles Under Harsh Water-Limiting Conditions

Abstract. Tadpoles of some anuran species are known to survive out of water, but information is scarce or nonexistent for most species. We experimentally tested the survival ability of Amazonian tadpoles of six species out of water in conditions that simulated pond drying. Specifically, we tested the hypothesis that tadpoles typical of habitats subject to fast drying would have higher capacity to survive without free water. We found higher survival rates for some species that usually occur in temporary ponds and the lowest one for a species from perennial ponds. However, we also found species from temporary ponds and streams with intermediate tolerance to desiccation. Tadpole survival differed among species and increased in function of body mass but was not related to the probability of each species being subject to periods without water in their habitats. Therefore, we reject the hypothesis that tadpole survival in the absence of water is a simple function of the probability of ponds drying.

Alternative Manufacturing Concepts for Solid Oral Dosage Forms From Drug Nanosuspensions Using Fluid Dispensing and Forced Drying Technology

Flexible manufacturing technologies for solid oral dosage forms with a continuous adjustability of the manufactured dose strength are of interest for applications in personalized medicine. This study explored the feasibility of using microvalve technology for the manufacturing of different solid oral dosage form concepts. Hard gelatin capsules filled with excipients, placebo tablets, and polymer films, placed in hard gelatin capsules after drying, were considered as substrates. For each concept, a basic understanding of relevant formulation parameters and their impact on dissolution behavior has been established. Suitable matrix formers, present either on the substrate or directly in the drug nanosuspension, proved to be essential to prevent nanoparticle agglomeration of the drug nanoparticles and to ensure a fast dissolution behavior. Furthermore, convection and radiation drying methods were investigated for the fast drying of drug nanosuspensions dispensed onto polymer films, which were then placed in hard gelatin capsules. Changes in morphology and in drug and matrix former distribution were observed for increasing drying intensity. However, even fast drying times below 1 min could be realized, while maintaining the nanoparticulate drug structure and a good dissolution behavior.

Experimental investigation on drying performance of an existed enclosed fixed frequency air source heat pump drying system

As the quick development of industry drying technology, different heat pump drying systems were proposed in recent decades. Enclosed heat pump drying system was considered as the most widely used system. For an existed enclosed fixed frequency heat pump drying system, drying time could be decreased by increasing air temperature at inlet of drying chamber. However, as a fundamental problem, system drying performance influenced by air flow ratio was not tested and reported in open literatures. Therefore, basing on adding an air bypass duct, drying performance of an enclosed system was experimental investigated in this study, with 15 mm thickness fresh carrot chips used. Furthermore, qualitatively and quantitatively comparisons and discussions on experimental results were conducted. A whole drying process were firstly divided into three stages by different water content ratios, preheating stage at 98–100%, fast drying stage at 20–98%, and later drying stage at 0–20%, respectively. For the inlet air temperature of drying chamber is fixed at 40 °C, material drying time for water content ratio reaching 20% could be effectively decreased as much as 42 min, or 15.0%, by the strategy of hot air bypassed. After the drying time shortened, the calculated energy consumption for compressor was also decreased from 4.27 kWh for AFR at 1.0 to 3.63 kWh for AFR at 0.6. Contributions of this study can guide low temperature material drying process. Clearly, system control optimization and energy saving were both expected.

An easy drying schedule for Tectona grandis through vacuum press drying

Drying experiments were conducted on 25 mm thick samples of Tectona grandis with the aim of evolving a drying schedule under vacuum press drying. The experiments were conducted under eleven different combinations of water temperature and pressure level inside the chamber. The results were analysed to understand which combination resulted in highest percentage moisture content (MC) reductions from different initial MC ranges above and below the fibre saturation point of the species. Based on this, a simple schedule was formulated for drying planks of this timber. No serious drying degrades could be observed in the samples in spite of taking them through different drying cycles. It was found by applying this schedule that 25 mm thick samples of teak could be dried to around 7.6 % MC levels from around 24 % initial MC effectively in three steps. The study illustrated the usefulness of vacuum press drying technique in fast drying of teak.

Corrosion protection by organic coatings containing polyaniline salts prepared by oxidative polymerization

The aim of this work was to describe polyaniline salts synthesized and to assess the mechanical and anticorrosion properties of alkyd resin-based coating materials pigmented with them, in dependence on the pigment volume concentration and type. Polyaniline salts were prepared by oxidative polymerization in the solutions of inorganic (hydrochloric, phosphoric, and sulfuric) and organic (p-toluenesulfonic and 5-sulfosalicylic) acids. Polyaniline salts were characterized by thermal analysis and spectroscopic methods. Electrical conductivity was also measured by the van der Pauw method, and the molecular weight of the polyaniline was determined by gel permeation chromatography. Furthermore, the particle size of the solid salts was measured, and the morphology was studied by scanning electron microscopy. Subsequently, the parameters required to formulate pigmented organic coatings, i.e., density and critical pigment volume concentration were determined. A soybean oil-based fast drying alkyd resin of medium oil length was used as the binder for the organic coating material. Organic coatings containing the polyaniline salts at pigment volume concentrations 0%, 1%, 5%, 10%, and 15% were formulated and subjected to a standard accelerated cyclic corrosion tests. The organic coatings (paint films) were also subjected to mechanical tests and to the electrochemical test by potentiodynamic polarization studies.

The influence of calcium and zirconium based secondary driers on drying solvent borne alkyd coatings

Cobalt based driers are the most commonly used primary catalysts in alkyd coatings as they promote fast drying and lead to hard coatings. However, several studies have suggested potential reclassification of cobalt-based alkyd driers. Therefore, cobalt based driers are being replaced by alternatives, e.g. based on iron or manganese. In practice primary driers (Co, Mn, or Fe) are used in combination with secondary driers (e.g. Ca, Zr) to enhance drying of the film. Coating formulators aim for a high drying speed and hardness development. However, each combination of primary and secondary driers leads to a different oxidative drying pattern resulting in variations in the crosslink density and hardness development. In this study we have systematically investigated the effect of two secondary driers, Calcium (Ca) and Zirconium (Zr), on curing behavior when added to different primary driers (Co, Mn, and Fe) using a high spatial resolution NMR set-up. As expected, we observed increased drying speed and higher crosslink densities when adding these secondary driers. While calcium showed to promote the front speed, zirconium showed to increase the measured crosslink density. The behavior seems to be generic as this was seen for all three the primary driers.