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Alkyl ketene dimers (AKDs) are known to efficiently react with cellulose with a dual polarity in their structure: a polar component and a nonpolar component. AKD of three different carbon chain lengths, 4, 10, and 16 carbons have been synthesized, and thermomechanical pulp (TMP) fibers were modified by them. The modification of TMP fibers with AKD resulted in an increased water contact angle, showing the presence of the AKDs on the TMP fibers and a new carbonyl peak in the IR spectra, suggesting modification of the TMP fibers with AKD groups. Calculating the Hansen solubility parameters of AKD and AKD conjugated to TMP in polypropylene (PP) indicates improved compatibility, especially of longer chain AKD and TMP AKD. The rheological studies of the composites showed that the AKD with the longest carbon chain decreases the melt viscosity of the PP‐TMP‐AKD composite, which combined with the shape and the color of the extruded composite filaments indicates improved flow properties and reduced stress build up during processing. The research findings demonstrate the ability of AKD to enhance the dispersibility and compatibility of natural fibers with PP. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • An automated HS-GC technique was developed to determine the MP of AKD wax. • The methanol was chose as the tracer compound in this work. • The MP of AKD was measured by plotting the methanol signal vs. the temperature. • This novel concept is universal and can be used to many related applications. Abstract This study demonstrated a novel method for determining the melting point (MP) of industrial grade alkyl ketene dimer (AKD) wax by an automated headspace gas chromatographic (HS-GC) technique, in which methanol was used as the tracer. It was based on measuring the GC signal of methanol released from an aqueous solution during the temperature increasing. When the temperature of AKD MP reached, the AKD granules floated on the surface aqueous solution was liquidized and completely isolated the methanol transfer from the solution to the headspace. Thus, a transition point, corresponding to the MP of AKD wax, was observed when plotting the GC signal of methanol vs. the temperature. The results showed that the method has a good measurement precision (RSD < 0.68%) and accuracy (the relative differences were < 7.16%, compared to a reference method). The present method is simple, accurate and particularly suitable to be used in the batch sample testing. This new measurement concept can be also adopted to many related applications. [ABSTRACT FROM AUTHOR]

Abstract: To expand the application of nanofibrillated cellulose (NFC), the increase of its hydrophobicity is considered to be critical. In the present work, hydrophobic NFC powder was prepared through chemical modification with alkyl ketene dimer (AKD). The results showed that when modifying the original NFC with an AKD loading of 0.7 g/g (based on dry cellulose) at 110 °C for 6 h, the AKD graft yield of approximately 40% (based on initial cellulose mass) was successfully achieved. The Fourier transform infrared spectroscopy and X-ray diffraction analysis showed that the grafting reaction mainly occurred on the fibre surface and the nanocrystal structure of cellulose was preserved after chemical modification. The thermogravimetric analysis results indicated the thermal stability increased with increasing the AKD graft yield. Scanning electron microscopy observations indicated that no significant differences in fibril morphology before and after AKD modification. Water contact angle measurements of the films produced from original and AKD-modified NFC powders demonstrated the significant increase in hydrophobicity of NFC after modification with AKD. Moreover, the hydrophobicity of AKD-modified NFC increased with increasing AKD graft yield.Graphical abstract: [ABSTRACT FROM AUTHOR]

This paper reports on an ionic-liquid assisted headspace gas chromatographic (HS-GC) for the determination of the content of alkyl ketene dimer (AKD) in its latex samples, in which the GC system was equipped with a thermal conductivity detector (TCD). The method was based on the AKD hydrolysis conducted in 1-butyl-3-methylimidazolium chloride (ionic-liquid) added medium at 100 °C for 10 min in a closed headspace sample vial, and the measured CO 2 (the resulting product of the hydrolysis) by HS-GC. The results showed that the present method has a good measurement precision (RSD <2.3%) and accuracy (recoveries from 96 − 105%), and the limit of quantitation (LOQ) is 0.9%. The present method is very suitable to be used for the routine check of AKD content in its latex sample in mill applications. The study also showed that the content of AKD in the tested commercial latex samples were in the range of 3.5–12%. [ABSTRACT FROM AUTHOR]

Here we present a method to manufacture peptide-concentrating MALDI-plates with alkyl ketene dimer (AKD) as a new superhydrophobic coating. The fabrication of the hydrophobic plates included application of AKD by airbrush, and negative contact printing to generate the concentration sites. Deposited sample droplets were contained within the prestructured sites, and self-adjusted onto the site if slightly misplaced. No AKD contamination was observed, and the plates could easily be cleaned and regenerated. The S/N values for four model peptides was about twice as high compared with a standard steel plate and a commercial concentration plate. [ABSTRACT FROM AUTHOR]

In order to produce dry and hydrophobic microfibrillated cellulose (MFC) in a simple procedure, its modification with alkyl ketene dimer (AKD) was performed. For this purpose, MFC was solvent-exchanged to ethyl acetate and mixed with AKD dissolved in the same solvent. Curing at 130 °C for 20 h under the catalysis of 1-methylimidazole yielded a dry powder. Scanning electron microscopy of the powder indicated loss in nanofibrillar structure due to aggregation, but discrete microfibrillar structures were still present. Water contact angle measurements of films produced from modified and unmodified MFC showed high hydrophobicity after AKD treatment, which persisted even after extraction with THF for 8 h. The hydrophobized MFC was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance and X-ray analysis. In summary, strong indications for the presence of AKD on the surface of MFC before and after extraction with solvent were found, but only a very small amount of covalent β-ketoester linkages between the modification agent and cellulose was revealed. [ABSTRACT FROM AUTHOR]

In this study, we employed nanocrystalline cellulose (NCC) as an efficient dispersant to perpare alkyl ketene dimer (AKD) emulsion. The particle size and zeta potential of AKD/NCC emulsion were measured, which were approximately 5 μm and −50 mV, respectively. The surface-sized paper possessed multiple barriers properties. The air permeability of surface-sized paper was 0.29 μm/Pa s and the sizing degree reached 42 s when the amount of sizing was 12.58 g/m 2 with a 96.83% decrease and a 40.00%, increase, respectively. Furthermore, the mechanical properties were optimal when the amount of sizing was about 8 g/m 2 . AKD/NCC emulsion acted as a good reinforcing agent in surface-sized paper. [ABSTRACT FROM AUTHOR]

Highlights: [•] This is the first time to report AKD as a coupling agent for WPCs. [•] AKD has been demonstrated as an effective coupling agent for WPCs. [•] AKD is much cheaper than the common coupling agent, MAPP. [ABSTRACT FROM AUTHOR]

Abstract: In this work, three different methods were used to determine the phase behavior of alkyl ketene dimer (AKD) in supercritical carbon dioxide (SC-CO2). Rough values for the total solubility of AKD in SC-CO2 were obtained. The solubility ranges from 1 to 14mg AKD/g CO2 at temperatures from 40 to 80°C and pressures from 10 to 30MPa. A significant increase in solubility was observed in the region above 50°C and 20MPa. A region of improved solubility was found, without the presence of a cross-over pressure point. The fact that different solubility methods gave different results was discussed and the importance of data interpretation was highlighted. 1H NMR and MALDI-TOF MS analyses were utilized to chemically characterize the AKD wax. Its special behavior and the influence of data interpretation on the design of a RESS process were discussed. [Copyright &y& Elsevier]

Abstract: Superhydrophobic alkyl ketene dimer (AKD) layers were successfully produced on top of untreated paper surfaces by a rapid expansion of supercritical CO2 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 (100–300bar), pre-expansion temperature (40 and 60°C) and spraying distance (10 and 50mm) 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 2μm depending upon the experimental conditions used, being slightly smaller when using higher pre-expansion pressure and temperature as well as shorter spraying distance. [Copyright &y& Elsevier]

Abstract: The production of a hydrophobic starch microcellular foam (SMCF) through the addition of an alkyl ketene dimer (AKD) would be a bio-based material with valuable properties for many applications in which high specific surface area, low density and water resistance is important. Pigments for paper and coatings are a potential application. An emulsion of AKD and cooked corn starch was made by mixing AKD with cooked starch at 50°C under a high rate of shear. The effects of reaction temperature, starch concentration and pH on the reaction of AKD with starch and the resulting microcellular foam structure were studied. The starch/AKD foam particles were characterized by scanning electron microscope (SEM), elemental analysis to determine extent of reaction, thermogravimetric analysis (TGA), brightness, particle size and water swellability. The apparent viscosity of the starch solution was shown to have a linear relationship with the particle size and the brightness of the particles. The particles under all conditions had a very high brightness. The AKD was able to impart a significant hydrophobicity to the particles relative to starch alone but the water resistance was not great enough to preserve the porous structure when wetted. [Copyright &y& Elsevier]

Abstract: The possibility of delivering hydrophobization (or sizing) effect to cellulose fibre via AKD and ASA vapours was investigated using a novel method. Alkyl ketene dimer (AKD) and alkenyl succinic acid anhydride (ASA) are two of widely used hydrophobization chemicals in papermaking industry. It has been reported that sizing effect could be delivered by the vapourization and re-deposition mechanism under papermaking condition. Such a conclusion was reached in previous studies by measuring the level of hydrophobicity acquired by cellulose or glass surface after being exposed to the vapours of these AKD or ASA. In this work we investigated the possibility of vapour sizing by analyzing the chemical compositions of the vapours of AKD and ASA at typical papermaking temperatures. Our results suggest that the vapour of ASA has the same composition as the ASA liquid. However, the vapour of AKD is dominated by fatty acids (which are the initial materials for AKD synthesis). The actual AKD concentration in the vapour phase is below the detection limit of FTIR. These results indicate that cellulose hydrophobization via vapour is possible with ASA, but not practically possible for AKD. [Copyright &y& Elsevier]

Abstract: Water borne alkyl ketene dimer (AKD) dispersions have been investigated by means of optical microscopy and NMR diffusometry (NMR-D). In two different formulations, different amounts of entrapped water in pores with different sizes are obtained, which can be compared to a water-in-oil-in-water (w/o/w) dispersion. It is shown that the amount of entrapped water inside the AKD particles can conveniently be measured with the NMR-D technique. The pore size is however not obtained correctly from the NMR-D experiment. Due to the small size of the water pores, the pore size is underestimated when measured with NMR-D. This effect is investigated in more detail by Brownian dynamic simulations from which a correction factor is obtained that allows a more correct value of the pore size from NMR-D measurements. When the pore size is too small to be observed by optical microscopy, typically below 0.5μm, NMR diffusometry combined with Brownian dynamic simulations are shown to be a rapid and reliable tool for quantifying the porosity in these types of systems. [Copyright &y& Elsevier]