Alkyl Ketene Dimer Research Articles

Spreading Behavior of Water Droplets on Fractal Agar Gel Surfaces

Agar gels with hierarchical rough surfaces, referred to as "fractal agar gels," were prepared to model biological surfaces coated with mucus. Agar gels with rough surfaces of fractal dimension D = 2.2 were synthesized by transferring a fractal surface structure of alkylketene dimer (AKD). The rough structure accelerated the spreading of water droplets and induced the appearance of a wicking front. The mechanism of acceleration of the spreading on fractal surfaces based on a semiquantitative theoretical model was also clarified.

Analysis of printing and writing papers by using direct analysis in real time mass spectrometry

A quick and direct method for identifying organic components of papers in library and archival collections with minimal destructive sampling is needed for preservation, forensic, and general purposes. Direct analysis in real time mass spectrometry (DART-MS) is used for characterizing 16 reference papers of known manufacture in terms of their pulp composition and pitch contaminants. Unique mass spectra are obtained from bleached kraft, chemithermomechanical, and stone groundwood pulp papers in real time without extractions, derivatizations, chromatographic separations, and other time- and chemical-consuming sample preparations. Phytosteroids are volatilized from bleached hardwood kraft but not from bleached softwood kraft papers, which differentiates the two of them. The kraft papers are in turn differentiated from chemithermomechanical pulp papers by lignin-derived thermolyis products: syringyl products arise from hardwood, but guaiacyl and coumaryl products arise from softwood, chemithermomechanical pulp papers. Stone groundwood papers contain a number of extractives that are volatilized, which serve to differentiate them from all the other papers. Papers that contain rosin vs. alkyl ketene dimer (AKD) sizings are immediately differentiated. The DART-MS methodology is fast and simple, and the spectra are repeatable. Microsamples as small as ∼10 μg tweezed from the paper surface may be analyzed. These benchmark spectra are the prelude to further applications of DART-MS in paper research and the beginning of the development of a searchable library of DART-MS spectra of printing and writing papers by the Library of Congress.

ALKYL OLEATE SUCCINIC ANHYDRIDE AS A NEW MODIFICATION OF INTERNAL PAPER SIZING AGENT

There are two common synthetic sizing agents which are used in neutral-alkaline paper making: alkyl ketene dimer (AKD) and alkenyl succinic anhydride (ASA). However both show many disadvantages on application. Using alkyl oleate enabled us to improve the performance of the sizing chemicals. Two alkyl oleate succinic anhydride: methyl and ethyl oleate succinic anhydrides have been prepared, converted to aqueous emulsion and used in sizing of paper hand sheets at laboratory scale. The sizing performance of each was compared with that of the commercial sizing agents.

Influence of addition of bulking promoter on AKD-sizing performance

Paper density, tensile index, sizing degree, and other properties of the handsheets were measured in term of addition level of bulking promoters and alkyl ketene dimer (AKD). Bulking promoters had clear bulking effects, and in subsequent addition of the AKD, the sheet density was further decreased slightly. Although the density of the handsheet decreased from 0.64 to 0.61 g/cm3 when 0.2% AKD was added with the 0.8% bulking promoter, tensile strength decreased from 20.3 to 19.8 Nm/g. The addition of AKD led to suppression of the decrease in the tensile index. The bulking promoter may also have potential to give sizing effects to the paper sheet as well as the increase in paper thickness. When 0.05% AKD was added together with 0.8% of bulking promoter, the sizing degree of the handsheet was 25.6 seconds, and it was almost the same, 27.3 seconds, as the addition of 0.1% AKD only. AKD retention in the handsheet was determined by pyrolysis-gas chromatography (Py-GC). The addition of the bulking promoter contributed to AKD retention in the handsheet regardless of the sizing degree. Wetting characteristics of the handsheet were determined by contact angle measurements. Surface free energy, γ s , of the handsheet as calculated from the contact angle decreased as the level of AKD addition increased.

Properties of superhydrophobic paper treated with rapid expansion of supercritical CO2 containing a crystallizing wax

Paper samples were rendered superhydrophobic with Alkyl Ketene Dimer using (1) Airblasting with cryo ground micro particles, (2) crystallizing from organic solvents and (3) spraying with Rapid Expansion of Supercritical Solutions (RESS) technique. The papers were characterized using Scanning Electron Microscopy, contact angle to water measurements and X-ray Photoelectron Spectroscopy (XPS). Advancing contact angles were in the region of 150°–160° and receding contact angles were in the region of 110°–130°. Diagrams showing the drop base diameter vs. the contact angle when water is pumped into, and then withdrawn from, a sessile drop show that a stick slip pattern is present in the advancing phase for a non coated internally sized paper. Papers rendered superhydrophobic with the RESS technique showed a much less pronounced stick slip pattern in the advancing phase but still a stick slip pattern in the receding phase.

Rupture of thin films formed during droplet impact

Rupture of liquid films formed during droplet impact on a dry solid surface was studied experimentally. Water droplets (580±70 μm) were photographed as they hit a solid substrate at high velocities (10–30 m s −1 ). Droplet–substrate wettability was varied over a wide range, from hydrophilic to superhydrophobic, by changing the material of the substrate (glass, Plexiglas, wax and alkylketene dimer). Both smooth and rough wax surfaces were tested. Photographs of impact showed that as the impact velocity increased and the film thickness decreased, films became unstable and ruptured internally through the formation of holes. However, the impact velocity at which rupture occurred was found to first decrease and then increase with the liquid–solid contact angle, with wax showing rupture at all impact velocities tested. A thermodynamic stability analysis combined with a droplet spreading model predicted the rupture behaviour by showing that films would be stable at very small or at very large contact angles, but unstable in between. Film rupture was found to be greatly promoted by surface roughness.

PF-bonded particleboards from AKD-modified chips

Alkyl ketene dimer (AKD) was used as a hydrophobic agent for PF-bonded particleboards. In contrast to conventionally used paraffin, AKD can be covalently bonded to the chip surface by esterification with wood hydroxyl groups. FTIR analyses before and after toluene extractions indicated that only a small amount of the applied AKD is chemically bonded. Wettability studies on veneer strips suggested that particularly the bonded AKD accounts for the surface hydrophobicity.

Characterization and structural investigation of fractal porous-silica over an extremely wide scale range of pore size

We have succeeded in creating Menger sponge-like fractal body, i.e., porous-silica samples with Menger sponge-like fractal geometries, by a novel template method utilizing template particles of alkylketene dimer (AKD) and a sol-gel synthesis of tetramethyl orthosilicate (TMOS). We report here the first experimental results on characterization and structural investigations of the fractal porous-silica samples prepared with various conditions such as calcination temperature and packing condition of the template particles. In order to characterize the fractal porous-silica samples, pore volume distribution, porosity and specific surface area were measured over an extremely wide scale from 1 nm to 100 μm by means of mercury porosimetry, 1H NMR cryoporometry, nitrogen gas adsorption experiments together with direct evaluations of cross-sectional fractal dimension D cs, and size limits of D cs. We have found that the pore volume distribution and specific surface area of the fractal porous-silica samples can be discussed in terms of different fractal porous structures at different scale regions.

Procedural influence on the properties of particleboards made from AKD modified chips

Wood chips were treated with alkyl ketene dimer (AKD) using three different processes to impart water resistance to particleboards. In the first process, AKD was blended with UF resin. Thickness swelling and water uptake after a 24 h immersion period (20 and 69%) were lower than in the control boards (28 and 81%) but were higher than in the paraffin references (10 and 22%). In process 2, AKD and UF resin were sprayed separately on the chips resulting in a greater reduction of thickness swelling (15%) and water uptake (49%) than in process 1. Paraffin references revealed a thickness swelling and water uptake of 7 and 25%, respectively. An extension of the pressing time in processes 1 and 2 did not increase water repellence. In process 3, particleboards were made from AKD-treated chips that were cured at 130 °C (24 h) prior to gluing. They showed a thickness swelling of 7% and a water uptake of 25%, whereas particleboards with paraffin exhibited levels of 8 and 29%. The thickness swelling and water uptake of boards with AKD increased when the curing time was reduced from 24 to 12 to 6 h (130 °C). Changing the curing temperature from 130 to 100 °C (12 h) had no effect on board properties. The IB of boards made from pre-cured chips with AKD (24 h/130 °C) was 44% lower than in controls and 35% lower than in paraffin references. This indicates that AKD impedes the adhesion.

Transparent and High Gas Barrier Films of Cellulose Nanofibers Prepared by TEMPO-Mediated Oxidation

Softwood and hardwood celluloses were oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation. The TEMPO-oxidized cellulose fibers were converted to transparent dispersions in water, which consisted of individual nanofibers 3-4 nm in width. Films were then prepared from the TEMPO-oxidized cellulose nanofibers (TOCN) and characterized from various aspects. AFM images showed that the TOCN film surface consisted of randomly assembled cellulose nanofibers. The TOCN films prepared from softwood cellulose were transparent and flexible and had extremely low coefficients of thermal expansion caused by high crystallinity of TOCN. Moreover, oxygen permeability of a polylactic acid (PLA) film drastically decreased to about 1/750 by forming a thin TOCN layer on the PLA film. Hydrophobization of the originally hydrophilic TOCN films was achieved by treatment with alkylketene dimer. These unique characteristics of the TOCN films are promising for potential applications in some high-tech materials.

Generation of superhydrophobic paper surfaces by a rapidly expanding supercritical carbon dioxide–alkyl ketene dimer solution

Superhydrophobic alkyl ketene dimer (AKD) layers were successfully produced on top of untreated paper surfaces by a rapid expansion of supercritical CO 2 solution (RESS) process. The new method resulted in a degree of hydrophobicity, as measured by contact angles of water droplets on AKD surfaces, dramatically higher, up to 173°, compared to a conventional method consisting in melting AKD granules directly on the paper substrate, giving contact angles of around 109°. Experiments were conducted to investigate the effects of varying pre-expansion pressure (100–300 bar), pre-expansion temperature (40 and 60 °C) and spraying distance (10 and 50 mm) on the properties of the treated surfaces. The surfaces were analyzed regarding AKD particle size, surface morphology and hydrophobicity with the aid of scanning electron microscopy (SEM) and contact angle measurements. The average AKD particle size after RESS processing was between 1 and 2 μm depending upon the experimental conditions used, being slightly smaller when using higher pre-expansion pressure and temperature as well as shorter spraying distance.

A surface study of cellulose fibres impregnated with alkyl ketene dimers via subcritical and supercritical carbon dioxide

Impregnation of Alkyl Ketene Dimers (AKD) into filter paper substrates was investigated using subcritical and supercritical carbon dioxide (scCO 2) over a range of operating conditions, in order to assess the possibility of this novel technique as an alternative method of sizing for the paper industry. The key findings were that AKD was uniformly distributed within the paper matrix at five times greater than the concentration observed via conventional means, and that sizing development (i.e., a contact angle >90° for water on the substrate) occurred at a similar rate to that of other more conventional techniques. It is believed that lower quantities of AKD could be used with this technique, reducing the overall quantity of AKD required for a particular level of sizing.

Super Water-Repellent Fractal Surfaces of a Photochromic Diarylethene Induced by UV Light

Photochromic diarylethene forms super water-repellent surfaces upon irradiation with UV light. Microfibril-like crystals grow on the solid diarylethene surface after UV irradiation, and the contact angle of water on the surface becomes larger with increasing surface roughness with time. The fractal analysis was made by the box-counting method for the rough surfaces. There are three regions in the roughness size having the fractal dimension of ca. 2.4 (size of roughness smaller than 5 µm), of ca. 2.2 (size of roughness between 5–40 µm), and of ca. 2.0 (size of roughness larger than 40 µm). The fractal dimension of ca. 2.4 was due to the fibril-like structures generated gradually by UV irradiation on diarylethene surfaces accompanied with an increase in the contact angle. The surface structure with larger fractal dimension mainly contributes to realizing the super water-repellency of the diarylethene surfaces. This mechanism of spontaneous formation of fractal surfaces is similar to that for triglyceride and alkylketene dimer waxes.

Use of alkyl ketene dimer (AKD) for surface modification of particleboard chips

The study objective was to impart urea-formaldehyde (UF) bonded particleboards higher and longer-lasting hydrophobicity than that resulting from conventionally used paraffin. Alkyl ketene dimer (AKD) is a paper sizing agent that can theoretically esterify wood compounds and result in a surface modification. Particles were 1) impregnated with an aqueous AKD-solution and cured at 130 °C prior to gluing, or 2) sprayed with a mixture of AKD-solution and UF-resin in a single step. Boards with and without paraffin wax were used as controls. Thickness swelling after 2, 24, and 48 h immersion was decreased by 90, 62, and 59% when the chips were impregnated with AKD in comparison to untreated control boards. Water uptake after 2, 24, and 48 h was reduced by 91, 75, and 60%. AKD-impregnation with subsequent curing decreased the internal bond strength by 53%, indicating that AKD impedes the adhesion. The mixture of AKD and UF-glue did not result in considerable hydrophobicity. Increased methyl/methylene and carbonyl bands in FTIR-spectra after toluene-extraction suggest that AKD partially formed ester bonds at the wood surface.

Morphology of C6 Glioma Cells on a Water-Repellent Fractal Alkyl Ketene Dimer Surface

In many in vitro cultures, cells may change their morphology, probably caused by adherence to the surface of the culture dish. Since a fractal alkyl ketene dimer (AKD) surface provides super water-repellency with a contact angle of 174° , we considered that it might provide an improved surface environment for the growth and differentiation of cells by preventing intimate adhesion. C6 glioma cells which were selected to test the effects of the fractal surface, were cultured on a conventional surface, a smooth AKD surface or a fractal AKD surface. On the conventional and smooth AKD surfaces, cells developed bipolar or multipolar shapes with enlarged cell bodies and neurite-like processes. In contrast, cells cultured on the fractal AKD surface presented fine filopodium-like processes like protoplasmic astrocytes in vivo, and higher morphological complexity was revealed by fractal analysis. Reconstruction of three-dimensional shape indicated that cells on the fractal surface were globular, whereas those on the conventional surface were rather flat. Our results suggest that C6 glioma cells on a fractal AKD surface show features of natural astrocytes with their elaborate morphology. The fractal surface thus may provide a new and natural culture environment for experimental assessment of glial structure and function.

Spontaneous Formation of Super Water-Repellent Fractal Surfaces in Mixed Wax Systems

Alkylketene dimers (AKDs) and triglyceride waxes form fractal surfaces spontaneously and show super water-repellent property. Spontaneous formation of fractal structures on their surfaces takes place when the meta-stable crystalline phase of the waxes transforms to the thermodynamically stable form of crystal. The triglyceride waxes form the meta-stable alpha-phase in whole specimen when solidified from their melt. In the case of AKD, on the other hand, only a small portion of the specimen solidifies in the meta-stable form of crystal. The surface of the AKD, however, becomes fractal in the whole part. We have, thus, examined the fractal structure formation in the mixed wax systems in which one wax forms fractal surfaces and the other one does not. In the stearic acid/tristearin mixed system as a typical one, the super water-repellent fractal surfaces form in the higher composition region of tristearin than that of the eutectic point in their mixture.

PET recyclable polymer for making paper washbowls

A paper washbowl made from recycled newspaper that can hold hot soapy water (70o C) for a mini-mum of 4 h was successfully developed by using EvCote® PGLR-25 added into the fiber slurry before the bowl was formed. We also studied other variables such as furnish, size (rosin and alkyl ketene dimer), and retention aids. In addition to the EvCote® PGLR-25, the results showed that the retention aid and rosin both are important ingredients in the fiber formulation.

Fractal Materials and Their Functional Properties

Fractal, a mathematical concept, has been utilized to develop some functional materials by the present author and his coworkers. Fractal surfaces show super water- and even oil-repellent property due to their very large surface area. In order to realize the super water-repellent fractal surfaces some waxes (alkylketene dimer and triglycerides) were employed. These waxes interestingly form the fractal surfaces spontaneously. The formation mechanism of the fractal structures on the wax surfaces has been made clear. The waxes which form the fractal surfaces have a meta-stable crystalline phase when solidified from their melts, and then transform to the thermodynamically stable crystal. During this phase transition process, the wax surfaces become fractal. For practical applications in future, durable super water-repellent and highly oil-repellent fractal surfaces have been synthesized by the electrochemical polymerization of an alkylpyrrole and the coating them with a fluorinated alkylsilane-coupling agents. In the final part of this article, the creation of a fractal body, not the surfaces, with a novel template method is mentioned. Such a fractal body is expected to show some interesting and unique functional properties.

Influence of Fillers on Sizing Efficiency and Hydrolysis of Alkyl Ketene Dimer

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Alkyl Ketene Dimer (AKD) sizing – a review

Over the years, there have been great efforts to try to develop cellulose reactive sizing agents. The assumption in these developments have been that the covalent linkage allows permanent attachmen ...