Cellulose Particles Research Articles

Photocatalytic H2 production from water splitting employing depolymerized cellulose through LiCl activation as sacrificial agent

We report a facile approach of depolymerizing cellulosic biomass by a physical pressing intensified inorganic salt hydrolysis (PIISH) process, in which inorganic ion (e.g. Li+) as an activation agent can be drilled into the outlayers of cellulose particles so as to break down the hydrogen bonds in cellulose, and the fragments detached from bulk cellulose could be further converted to glucose or other soluble carbohydrates by in situ formed LiOH or HCl catalyzed hydrolysis. The particle size, morphology and surface structure of microcrystalline cellulose are markedly changed which have been observed by a series of physicochemical characterization of PIISH treated cellulose. The cellulose depolymerization was related to the applied pressure and the type of inorganic ions, and about 4.5% cellulose was converted into glucose using LiCl salt at 20–30 MPa pressing. Platinized TiO2 prepared by different approaches has been characterized and screened for photocatalytic H2 production utilizing the cellulose decomposed products as sacrificial agents under UV light irradiation. The apparent quantum efficiencies in 5 h and 35 h for H2 production under 365 ± 10 nm irradiation are about 6.12% and 2.36%. This facile approach has been applied for depolymerizing cellulosic biomass resources for solar driven H2 production.

Epoxy biocomposites-based chemically treated coffee dystrophy and castor oil

An agro-waste such as coffee beans has been used to generate cellulose particles. Coffee roast which is brown in color, was treated with 6% sodium chlorite solution, followed by alkali treatment. This chemically treated mass was subjected to acid treatment with 20% sulfuric acid. Cellulose microwhiskers were released. These micro particles were examined by an X-ray diffractometer (XRD). X-Ray diffraction study of these white cellulose particles and the residue showed a highly crystalline nature of the cellulose particles. The fourier transform infrared (FTIR) spectra were carried out to further investigate any structural changes after chemical treatment. The spectra of the treated powder showed lesser peak intensity at 1630 cm−1. This peak is related to the aromatic ring of lignin. Thus, indicating that the removal of aromatic rings of lignin and polysaccharides after hydrolysis process, simultaneously increases degree of crystallinity. Composites of epoxy resin with a conventional amide-type hardener reinforced with renewable materials were investigated in the presence of castor oil (CO). The renewable material was extracted from coffee beans using various chemical agents. The extracted renewable material has been incorporated into epoxy resin. The composites were evaluated by FTIR to check any interactions. The remarkable hint is the increased intensity of the peak located at 3941 cm−1 being assigned to the –NH2 of the amine cured epoxy. The increment in the intensity is being attributed to the enhanced degree of interaction between the multifunctional CO and the amine cured epoxy resin as mentioned earlier. Tests of tensile and impact strength properties were carried out and Izod impact was determined at room temperature. It has been found that the incorporation of CO has significantly increased the elongation at break. The impact resistance of the composites with CO has significantly increased as compared to the control and the samples without CO. Scanning electron microscopy (SEM) images were taken to assess the effects of reinforcement and homogenization of the composites. It was noticed that the incorporation of the CO has turned the topography of the samples to a smooth surface with respect to rugged phase of the samples without CO.

Fouling characteristics of microcrystalline cellulose during cross-flow microfiltration: Insights from fluid dynamic gauging and molecular dynamics simulations

The fouling behaviour of microcrystalline cellulose (MCC) particles on polyethersulfone (PES) membranes was investigated using fluid dynamic gauging (FDG) and molecular dynamics (MD) simulations. Experimental cross-flow microfiltration (MF) of a dilute MCC suspension at 400 mbar transmembrane pressure using 0.45 μm PES membranes revealed an estimated fouling layer thickness of 616 ± 5 μm for both fouled and re-fouled membranes at an applied shear stress of 37 ± 2 Pa. A decline in pure water flux was observed after each membrane cleaning and flushing procedure, indicating that highly resilient layers were formed close to the membrane surface. A possible explanation for the formation of resilient cellulose layers was obtained through MD simulations of the free energy profiles, which predicted deep energy minima at close interparticle separations of the cellulose–cellulose and cellulose–PES systems. The consequence of this energy minima is that attractive and repulsive forces are in balance at a specific distance between the particles, suggesting high binding energy at close interparticle distances. This implies that a certain force is needed to remove the layer or redisperse the cellulose particles. MD simulations also suggested that contributions made by repulsive hydration forces negatively influenced the adsorption of cellulose particles onto the PES membrane. These results highlight how experimental FDG measurements, when complemented with MD simulations, can provide insights into the fouling behaviour of an organic model material during cross-flow filtration.

Spray-dried microfibrillated cellulose particles as texture modifier in liquid foods and their effect on rheological, tribological and sensory properties

Microfibrillated cellulose (MFC) has potentisal to be used as clean label texture modifier in foods due to its structural and mechanical properties. These properties deteriorate upon drying of MFC dispersions due to aggregation of the microfibrils. In this study dried MFC particles were prepared by spray-drying MFC dispersions in a surplus of maltodextrin to prevent hornification. The aim of this study was to evaluate the effect of MFC particle concentration and MFC:maltodextrin ratio of dried MFC powders on rheological, tribological and sensory texture properties of liquid foods. Scanning Electron Microscopy demonstrated that after spray-drying, MFC powders with polydisperse particle size distribution were obtained (1–30 μm). Upon suspension of spray-dried MFC powder in water, maltodextrin dissolved in the aqueous continuous phase whereas spherical MFC networks retained their shape and co-existed in a mixture with individual fibrils. Spray-dried MFC powders were added to skimmed milk and tomato soup at different concentrations. With increasing concentration of dried MFC particles, shear viscosity, consistency index K, storage and loss modulus of skimmed milks and tomato soups increased whereas flow index n decreased. Addition of spray-dried MFC particles to milks and soups significantly (p < 0.05) increased sensory thickness and creaminess. Milks displayed similar tribological properties irrespective of MFC particle concentration, which was presumably caused by exclusion of the MFC network from the tribological gap. Rheological properties, thickness and creaminess increased more effectively upon addition of low MFC:maltodextrin particles compared to particles with high MFC:maltodextrin ratio. We conclude that spray-dried microfibrillated cellulose particles can be used as thickener or fat replacer in liquid foods.

Solid particles surface-modified with beta-cyclodextrin for sustained release of flavor

Beta-cyclodextrin (β-CD) has promising applications in many fields based on its hydrophobic cavity at the central of the cyclic molecule, which can form inclusion complex with specific molecule via a host-guest interaction. However, the water solubility of β-CD limits its application. Herein, attempts have been made to graft β-CD onto two kinds of solid particles while retaining the function of β-CD, so as to expand its application. First, SiO 2 nanoparticles were modified with silane coupling agent KH-560 to offer epoxy groups. Then, the epoxy groups of the modified SiO 2 and the hydroxyl groups of β-CD were simultaneously esterified by a dicarboxylic acid of succinic acid in a non-toxic solvent medium to obtain the β-CD modified SiO 2 (SiO 2 @β-CD). On the other hand, microcrystalline cellulose (MCC) particles were also modified with β-CD (MCC@β-CD) through co-esterification of their hydroxyl groups with succinic acid. The syntheses were monitored by Fourier transform infrared (FT-IR) spectroscopy, and the obtained materials were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The degrees of β-CD modification for the particles have been measured and analyzed to optimize the synthesis conditions. The results indicate that the degree of β-CD modification for the SiO 2 @β-CD is relatively low, but the material exhibits over 60 ºC elevation of the thermal stability. In comparison, the degree of β-CD modification for MCC@β-CD reached as high as 422 mg/g. Due to the much higher content of β-CD, the synthesized MCC@β-CD was employed to load a flavor compound of D-limonene, and its sustained release was investigated to suggest the potential of the β-CD modified particles.

PREPARATION AND RHEOLOGICAL CHARACTERIZATION OF CELLULOSE-CHITOSAN HYDROGEL FOR EXTRUSION 3D PRINTER

The application of three-dimensional (3D) printing in tissue engineering is becoming prominent nowadays. A big obstacle for this technology is the selection of proper ink material. Chitosan hydrogel is an established biocompatible material that can be used as tissue scaffolds, and it has the rheology necessary for processing via extrusion type 3D printer. However, chitosan still has degradation and swelling limitations. Hence, chitosan hydrogel blends were incorporated with cellulose particles and were prepared as ink material. The hydrogels were successfully synthesized via thermo-responsive sol-gel method. Fourier transform infrared spectroscopy (FT-IR) analysis showed that the gelation of hydrogels formed a semi-interpenetrating network of ionically crosslinked chitosan and cellulose particles. Rheological tests have shown that the hydrogels exhibited shear thinning property necessary for printing. However, high cellulose amounts caused clogging during printing, and the presence of water limited the structural rigidity of the printed product. Besides this, it was found that the addition of cellulose was able to increase swelling, decrease degradation rate, and decrease gelation time, but the effect is not significant for any of these three properties.

The Response of Duckweed Lemna minor to Microplastics and Its Potential Use as a Bioindicator of Microplastic Pollution.

Biomonitoring has become an indispensable tool for detecting various environmental pollutants, but microplastics have been greatly neglected in this context. They are currently monitored using multistep physico-chemical methods that are time-consuming and expensive, making the search for new monitoring options of great interest. In this context, the aim of this study was to investigate the possibility of using an aquatic macrophyte as a bioindicator of microplastic pollution in freshwaters. Therefore, the effects and adhesion of three types of microplastics (polyethylene microbeads, tire wear particles, and polyethylene terephthalate fibers) and two types of natural particles (wood dust and cellulose particles) to duckweed Lemna minor were investigated. The results showed that fibers and natural particles had no effect on the specific growth rate, chlorophyll a content, and root length of duckweed, while a significant reduction in the latter was observed when duckweed was exposed to microbeads and tire wear particles. The percentage of adhered particles was ten times higher for polyethylene microbeads than for other microplastics and natural particles, suggesting that the adhesion of polyethylene microbeads to duckweed is specific. Because the majority of microplastics in freshwaters are made of polyethylene, the use of duckweed for their biomonitoring could provide important information on microplastic pollution in freshwaters.

Biodegradation of poly(lactic acid)/regenerated cellulose nanocomposites prepared by the Pickering emulsion approach

Poly(lactic acid)/regenerated cellulose nanocomposites have been prepared by the Pickering emulsion approach. The composites contained 0, 0.5, 1.0, 1.5, 2.0 and 3.0 wt% nanocellulose. Plates compression molded from the composites were degraded enzymatically by Proteinase K with the daily change of the degradation medium. The results confirmed the excellent catalyzing effect of Proteinase K. The enzymatic degradation catalyzed by Proteinase K is very fast, considerable amount of lactic acid forms even in one day. The daily change of the medium allows the complete degradation of composite samples within one week. Degradation rate determined in this way is an average value; the rates are different each day. The effect of nanocellulose on the rate of degradation is quite complex. Overall degradation rate first increases from around 0.5%/h for the neat PLA to a maximum value of 0.8%/h at 0.5 wt% RC content and then decreases with increasing cellulose content back to around 0.5%/h as the amount of RC increases from 0.5 to 3 wt%, because of increased crystallinity and the formation of a network from the cellulose particles, which hinder the penetration of enzyme molecules into areas of the specimen degraded already. Composite structure changes considerably with increasing regenerated cellulose content, larger aggregates form leading to accelerated degradation.

Micronized cellulose particles from mechanical treatment and their performance on reinforcing polypropylene composite

Micronized cellulose particles from mechanical treatment and their performance on reinforcing polypropylene composite

Metal sulfate-catalyzed methanolysis of cellulose at high solid loadings: Heterogeneous degradation kinetics and levulinate synthesis

Increasing efforts have been devoted to the production of bio-based chemicals from high solid content of renewable biomass to pursue optimal process efficiency and economics. In this study, the preparation of methyl levulinate (ML) by metal sulfate-catalyzed methanolysis from high solid content of cellulose was investigated. When the cellulose loading was 15%, 38.67% of ML yield can be obtained under the optimum reaction conditions. Al2(SO4)3 can be reused more than five times while maintaining high activity in the process. The characterization of cellulose particles confirmed that cellulose particles shrunk over the reaction time. The heterogeneous degradation kinetics of high solid content of cellulose in methanol could be explained by a shrinking core model. High solid loadings led to a decrease of the reaction rate constants of methanolysis. Using cellulose with a small particle size can improve the methanolysis reaction rate. The study also proposed comprehensive reaction pathways for ML production from high solid content of cellulose. To elucidate the methanolysis mechanism, an assessment of density functional theories for the calculation of glucose methanolysis at the molecular level is presented. All these results can inspire the development of ML synthesis technology through methanolysis from renewable biomass with high solid loadings.

The effect of periodate oxidation, tert-butanol treatment, and starch addition in improving melt dispersion of cellulosic fillers in PBAT

Dispersion in the melt is a very serious issue that affects properties of composites based on cellulosic fillers as these materials tend to form agglomerates. The aim of this study is to test the efficiency of various methods to improve the dispersion of cellulosic fillers in PBAT polymer. First, periodate oxidation treatment was carried out on the fillers in an attempt to reduce the amount of hydroxyl groups responsible of the agglomeration of cellulosic fillers in composite materials. Secondly, as several studies have demonstrated the positive effect of using tert-butanol (TB) as a freeze-drying medium for preventing the aggregation of cellulosic particles, this method was tested to produce composites with reduced amount of agglomerates. Finally, the addition of a third component as a compatibilizer which has a similar chemical structure to cellulose such as starch was also tested. No significant improvement of mechanical properties was noticed in using TB as a freeze-drying medium or with periodate oxidation treatment on the cellulosic fillers at least in improving dispersion in PBAT composites. However, the addition of starch as a compatibilizer has proved its effectiveness through the creation of a percolating network and a better dispersion of the fillers in the polymer matrix.

Model of Processive Catalysis with Site Clustering and Blocking and Its Application to Cellulose Hydrolysis.

Interactions between particles moving on a linear track and their possible blocking by obstacles can lead to crowding, impeding the particles' transport kinetics. When the particles are enzymes processively catalyzing a reaction along a linear polymeric substrate, these crowding and blocking effects may substantially reduce the overall catalytic rate. Cellulose hydrolysis by exocellulases processively moving along cellulose chains assembled into insoluble cellulose particles is an example of such a catalytic transport process. The details of the kinetics of cellulose hydrolysis and the causes of the often observed reduction of hydrolysis rate over time are not yet fully understood. Crowding and blocking of enzyme particles are thought to be one of the important factors affecting the cellulose hydrolysis, but its exact role and mechanism are not clear. Here, we introduce a simple model based on an elementary transport process that incorporates the crowding and blocking effects in a straightforward way. This is achieved by making a distinction between binding and non-binding sites on the chain. The model reproduces a range of experimental results, mainly related to the early phase of cellulose hydrolysis. Our results indicate that the combined effects of clustering of binding sites together with the occupancy pattern of these sites by the enzyme molecules play a decisive role in the overall kinetics of cellulose hydrolysis. It is suggested that periodic desorption and rebinding of enzyme molecules could be a basis of a strategy to partially counter the clustering of and blocking by the binding sites and so enhance the rate of cellulose hydrolysis. The general nature of the model means that it could be applicable also to other transport processes that make a distinction between binding and non-binding sites, where crowding and blocking are expected to be relevant.

Ingestion of microplastics and textile cellulose particles by some meiofaunal taxa of an urban stream

Microplastics (MPs) and textile cellulose are globally pervasive pollutants in freshwater. In-situ studies assessing the ingestion of MPs by freshwater meiofauna are few. Here, we evaluated MP and textile cellulose ingestion by some meiofaunal taxa and functional guilds of a first-order stream in the city of Florence (Italy) by using a tandem microscopy approach (fluorescence microscopy and μFTIR). The study targeted five taxa (nematodes, oligochaetes, copepods, ephemeropterans and chironomids), three feeding (scrapers, deposit-feeders, and predators), and three locomotion (crawlers, burrowers, and swimmers) guilds. Fluorescent particles related to both MPs and textile cellulose resulted in high numbers in all taxa and functional guilds. We found the highest number of particles in nematodes (5200 particles/ind.) and deposit-feeders (1693 particles/ind.). Oligochaetes and chironomids (burrowers) ingested the largest particles (medium length: 28 and 48 μm, respectively), whereas deposit-feeders ingested larger particles (medium length: 26 μm) than scrapers and predators. Pellets were abundant in all taxa, except for Chironomidae. Textile cellulose fibers were present in all taxa and functional guilds, while MP polymers (EVA, PET, PA, PE, PE-PP) differed among taxa and functional guilds. In detail: EVA and PET particles were found only in chironomids, PE particles occurred in chironomids, copepods and ephemeropterans, PA particles were found in all taxa except in nematodes, whereas particles made of PE-PP blend occurred in oligochaetes and copepods. Burrowers and deposit-feeders ingested EVA, PET, PA, PE and PE-PP, while crawlers and scrapers ingested PE and PA. Swimmers and predators ingested PE, PA and PE-PP. Our findings suggest a pervasive level of plastic and textile cellulose pollution consistent with an urban stream which propagates in the meiofaunal assemblage of the stream ecosystem.

EFFECT OF FIBRILLATION ON THE ABILITY OF CELLULOSE FIBERS TO SUPPRESS THE AGGREGATION OF QUINACRIDONE

Quinacridone is a red–violet pigment often used as a coloring agent. However, the aggregation of quinacridone needs to be resolved to avoid undesirable color changes. Cellulose nanofibers are a potential candidate for novel pigment dispersants, due to their ability to inhibit aggregation. In this study, the effect of the degree of fibrillation of cellulose fibers on their performance as dispersants was investigated. Four types of highly fibrillated cellulose particles (HFCPs) were prepared using a disk mill and a high-pressure homogenizer. The degree of fibrillation was evaluated using specific surface area measurements, scanning electron microscopy, and gravitational sedimentation analysis. Fibrillation of cellulose was found to increase its adsorption capacity toward quinacridone. Even partly fibrillated celluloses successfully inhibited the aggregation of quinacridone. Color measurements of the quinacridone–cellulose suspensions indicated that, although fibrillation of cellulose improves the chroma of the suspensions, excess fibrillation causes a decrease in the chroma.

Separation of Microplastic Particles from Sewage Sludge Extracts Using Magnetic Seeded Filtration

Microplastic particles (MP) are efficiently retained in wastewater treatment plants and enriched in sewage sludge. For monitoring MP contents in wastewater systems, sewage sludge is thus well suited, but also requires an isolation of MP from the sludge matrix, as other sewage sludge components may interfere with the MP identification and quantification. Although organic matter in sludge samples can be removed through acid and enzymatic digestion procedures, cellulose - mainly from toilet paper - remains in the digests, due to its high chemical resistivity and similar density to MP. We apply the separation concept of magnetic seeded filtration to isolate MP through selective hetero-agglomeration with magnetic seed particles. MP and cellulose differ in their hydrophobic properties and we investigate to what extent these differences can be exploited to selectively form MP-magnetite hetero-agglomerates in the presence of cellulose. These hetero-agglomerates are subsequently separated using a magnet. Five MP types (Polyethylene terephthalate (PET), polypropylene (PP), low density polyethylene (LDPE), polyvinyl chloride (PVC) and polystyrene (PS)) and cellulose particles were mixed in different combinations with both hydrophilic and hydrophobic (silanized) magnetite particles. PET, PP, LDPE and PS only poorly agglomerated with pristine (hydrophilic) magnetite, but efficiently formed hetero-agglomerates with hydrophobic magnetite and were successfully removed from suspensions (80−100%). PVC agglomerated more efficiently with pristine than with hydrophobic magnetite and cellulose only agglomerated to a limited extent with either hydrophilic or hydrophobic magnetite, resulting in a high process selectivity. Results from experiments conducted at different ionic strengths and with hydrophilic and hydrophobic magnetite suggests that the agglomeration process was dominated by hydrophobic interactions. Enzymatic and oxidative treatment of the MP only marginally affected the separation efficiencies and (treated) MP spiked to sewage sludge extracts were successfully recovered using magnetic seeded filtration.

Dynamic and Static Assembly of Sulfated Cellulose Nanocrystals with Alkali Metal Counter Cations.

Sulfate groups on cellulose particles such as cellulose nanocrystals (CNCs) provide colloidal stability credit to electrostatic repulsion between the like-charged particles. The introduction of sodium counter cations on the sulfate groups enables drying of the CNC suspensions without irreversible aggregation. Less is known about the effect of other counter cations than sodium on extending the properties of the CNC particles. Here, we introduce the alkali metal counter cations, Li+, Na+, K+, Rb+, and Cs+, on sulfated CNCs without an ion exchange resin, which, so far, has been a common practice. We demonstrate that the facile ion exchange is an efficient method to exchange to any alkali metal cation of sulfate half esters, with exchange rates between 76 and 89%. The ability to form liquid crystalline order in rest was observed by the presence of birefringence patterns and followed the Hofmeister series prediction of a decreasing ability to form anisotropy with an increasing element number. However, we observed the K-CNC rheology and birefringence as a stand-out case within the series of alkali metal modifications, with dynamic moduli and loss tangent indicating a network disruptive effect compared to the other counter cations, whereas observation of the development of birefringence patterns in flow showed the absence of self- or dynamically-assembled liquid crystalline order.

Synthesis and Effect of Nanocellulose Obtained from East Java Kenaf Fiber on Mechanical Properties of Polyurethane Foam Composites as Strong and Lightweight Materials

Cellulose is a fascinating biopolymer and sustainable raw material. Cellulose particles with at least one dimension in the nanoscale are referred to as nanocellulose. Kenaf fiber is a natural fiber used in this study because it has high mechanical properties and strong interface adhesion with polymers so it provides superior properties to other natural fibers. Polyurethane (PU) foam is widely used as a core layer in sandwich composite construction to produce a lightweight material. This study presents a synthesis of cellulose nano-fibrils (CNF) extracted from East Java, Indonesia based kenaf fibers, an analysis of the effect of adding CNF as a filler and a reinforcement in PU foam composites, and a formulation of PU-CNF foam composite that provided the best mechanical properties as strong and lightweight materials in structural applications. The CNF extraction from kenaf fiber started by fiber pre-treatment including alkalization and bleaching, then mechanical treatment with an Ultra Fine Grinder to produce CNF suspension. The weight variations of CNF in PU foam were 0, 3, 5, 7, and 10 wt%. PU-CNF composite fabrication using the in-situ polymerization method. CNF characterization included TEM, XRD, and FT-IR. TEM results on CNF show that the CNF diameter is in the range of 40-70 nm. The functional group from the FT-IR results showed that the pre-treatment process on kenaf fiber was successful in reducing the lignin and hemicellulose content. XRD results showed that the CNF crystallinity was 75.22%. The PU-CNF foam composite characterization included a compressive test, 3-point bending test, and SEM. The PU foam composite with 3 wt% CNF reinforcement is the best composite which has the optimum value from the results of the compression test and the 3-point bending test. The compressive strength value increased by 20.01%, from 236.997 kPa to 284.434 kPa, the compressive modulus value increased by 29.21% from 5.67 MPa to 7.32 MPa, and the 3-point bending strength value increased 28.29% from 572.24 to 734.15 kPa. All the results expected to support that CNF was a potential reinforcement material with a high surface area for a wide variety of applications.

Reliable online measurement of population dynamics for filamentous co‐cultures

Understanding population dynamics is a key factor for optimizing co-culture processes to produce valuable compounds. However, the measurement of independent population dynamics is difficult, especially for filamentous organisms and in presence of insoluble substrates like cellulose. We propose a workflow for fluorescence-based online monitoring of individual population dynamics of two filamentous microorganisms. The fluorescent tagged target co-culture is composed of the cellulolytic fungus Trichoderma reesei RUT-C30-mCherry and the pigment-producing bacterium Streptomyces coelicolor A3(2)-mNeonGreen (mNG) growing on insoluble cellulose as a substrate. To validate the system, the fluorescence-to-biomass and fluorescence-to-scattered-light correlation of the two strains was characterized in depth under various conditions. Thereby, especially for complex filamentous microorganisms, microbial morphologies have to be considered. Another bias can arise from autofluorescence or pigments that can spectrally interfere with the fluorescence measurement. Green autofluorescence of both strains was uncoupled from different green fluorescent protein signals through a spectral unmixing approach, resulting in a specific signal only linked to the abundance of S. coelicolor A3(2)-mNG. As proof of principle, the population dynamics of the target co-culture were measured at varying inoculation ratios in presence of insoluble cellulose particles. Thereby, the respective fluorescence signals reliably described the abundance of each partner, according to the variations in the inocula. With this method, conditions can be fine-tuned for optimal growth of both partners along with natural product formation by the bacterium.

Detection of Cellulose Particles in Transformer Oil Based on Transport of Intensity Equation

Cellulose particles are among the aging products of the insulating paper that are used in power transformers. Too many cellulose particles can cause transformer accidents. Traditional research and detection methods that are used for this problem generally focus on the number and length information of cellulose particles, and it is usually difficult to quantitatively describe the spatial shape of cellulose particles. However, the shape of cellulose particles is also one of the factors affecting the safety of transformer insulation. In this paper, we successfully extracted quantitative information of the spatial shape of cellulose particles in transformer oil using an image processing technique and the transport of intensity equation, providing a new novel approach for the study and detection of the shape of cellulose particles in transformer oil.

Effect of particle characteristics and foaming parameters on resulting foam quality and stability

In this study, the effects of ten different food-grade particles on bubble quality and stabilization of particle-stabilized food foams in batch and continuous foaming with and without polyglycerol ester (PGE) as an emulsifier were investigated. Particle properties, such as contact angle and porosity, and varying process parameters, such as shear rate and gas fraction, were assessed with respect to their impact on bubble size x50,0, bubble size distribution width and drainage.The smallest bubble size x50,0 in foams without PGE could be achieved with banana powder (88 μm), calcium carbonate (89 μm) and microcrystalline cellulose (79 μm) particles. In comparison, the smallest size in the reference without particles were 105 μm. Combining the use of particles with PGE further reduced bubble size by up to 57% and drainage by up to 100%. Increasing the shear rate from 4922 s−1 (35 μm) to 9844 s−1 (14 μm) resulted in smaller mean bubble sizes and significantly narrower bubble size distributions whereas no distinct correlation between gas fraction and resulting bubble size was found.This study shows that using suitable particles in combination with an optimized foaming process promotes both bubble quality and the stability of foams.