Preparation and characterization of Pickering foams by mechanical frothing and emulsion templating
Vol. 18., No.3., Pages 282-295, 2024
DOI: 10.3144/expresspolymlett.2024.20
DOI: 10.3144/expresspolymlett.2024.20
GRAPHICAL ABSTRACT

ABSTRACT
In this study, Pickering foamed emulsions have been prepared using β-cyclodextrin (β-CD), and d-limonene as a surfactant and an oil phase, respectively. The incorporation of β-CD/d-limonene inclusion complexes (ICs) in specific proportions (1:1, 1:3, and 1:5) to water phase, which is a polymer matrix composed of a mixture of polyvinyl alcohol (PVA) and psyllium husk (PSH) by mechanical frothing at high speed, and air bubbles have been formed in oil in water (o/w) emulsions. Ecofriendly bio-based foams have been developed in this method. Scanning Electron Microscope (SEM) analysis showed PVA/PSH Pickering foams usually open porous morphologies and the addition of d-limonene increases the amount of porosity from 43 to 49%. Although the resulting foams indicated similar thermal degradation profile, the presence of d-limonene in foams increased thermal stability. The surfaces of foams have a hydrophilic property with contact angles values lower than 80°. The tensile strength of foams decreased from 170 to 100 kPa due to the increased porosity. All foams indicated antibacterial activity to Staphylococcus aureus (S. aureus) with 9–12 mm zone inhibition. The incorporation of d-limonene into foams surprisingly decreased the cell viability. In brief, our findings show that the Pickering foams can be beneficial for wound healing applications.
RELATED ARTICLES
Jiazheng Sun, Zhengyu Liao, You-Yong Wang, Yushan Zou, Jinhong Li, Zesheng Xu, Yongming Song
Vol. 19., No.10., Pages 979-993, 2025
DOI: 10.3144/expresspolymlett.2025.74
Vol. 19., No.10., Pages 979-993, 2025
DOI: 10.3144/expresspolymlett.2025.74

Wood–plastic composite (WPC) is an environmentally friendly and cost-effective materials, while the high density and suboptimal mechanical properties of traditional WPC limit their broader applications. In this study, a wood fiber/polypropylene composite foam (WPCF) is fabricated via chemical foaming enabled by Nano-polytetrafluoroethylene (PTFE). Compared with the unmodified wood fiber/polypropylene composite foam, our developed WPCF demonstrates a 37.69% increase in cell density and a 29.45% decrease in cell size with uniform cell distribution. The fine cell structure of WPCF is attributed to the improved crystallization and suitable viscoelastic behavior due to the addition of nano-PTFE. As a result, WPCF demonstrates superior mechnical performance. When the PTFE content was 1 wt%, WPCF shows a tensile strength of 9.41 MPa, a flexural strength of 22.63 MPa, and a improved impact strength of 5.27 kJ/m2, which is 47.65, 33.12, and 76.23% higher than those of unmodified WPCF. Given to the mechanical robustness and low density of WPCF, the as-prepared high-performance wood fiber/polypropylene composite foam is a promising alternative as a green and sustainable material to traditional wood in construction, furniture, and packaging sectors.
Guilherme Ribeiro de Carvalho, Rafael Affonso Netto, Camila Delarmelina, Marta Cristina Teixeira Duarte, Liliane Maria Ferrareso Lona
Vol. 19., No.7., Pages 686-696, 2025
DOI: 10.3144/expresspolymlett.2025.52
Vol. 19., No.7., Pages 686-696, 2025
DOI: 10.3144/expresspolymlett.2025.52

In this study, a new plastic film with antiviral and antibacterial properties was developed using modified cassava starch with glycidyltrimethylammonium chloride (GTMAC) and reinforced by crystalline nanocellulose (CNC), called Q-CS/CNC. For comparison, a control film (Q-CS) was produced without the addition of CNC. Elemental analysis revealed a degree of substitution (DS) of 0.552, indicating the replacement of the OH groups of starch by the NR4+ groups of GTMAC during the quaternization reaction. The addition of CNC resulted in significant increases (p < 0.05) of 38.9, 38.2, and 43.1% in thickness, opacity, and water vapor permeability measurements, respectively, compared to Q-CS. Incorporating CNC also contributed to an increase of 43.6% in tensile strength and 109% in stiffness but slightly decreased thermal stability. The Q-CS/CNC film demonstrated efficacy by inactivating 99% of the coronavirus in 1 min and inhibiting the growth of Staphylococcus aureus and Escherichia coli. This action is attributed to the electrostatic interaction of quaternary amino groups, grafted onto starch, with the phospholipid membrane of microorganisms, resulting in the inactivation of these microorganisms. Therefore, these results highlight the potential use of Q-CS/CNC film as antimicrobial packaging, especially against coronavirus.
Lilla Bubenkó, Násfa Németh, Sára Frey, Tamás Molnár, Károly Belina, Orsolya Viktória Semperger
Vol. 19., No.7., Pages 726-735, 2025
DOI: 10.3144/expresspolymlett.2025.55
Vol. 19., No.7., Pages 726-735, 2025
DOI: 10.3144/expresspolymlett.2025.55

Biocomposites have recently received more attention because of raising environmental awareness and the drive toward sustainable technologies. The most common biodegradable polymer is poly(lactic acid) (PLA), which has an excellent balance of physical and rheological properties, but there is some limit to its usage. PLA properties can be improved by adding different types of fibers or fillers that come from agricultural waste. In this study, corn cob and lavender stem were used to reinforce PLA without any coupling agent, and the properties of the composites were investigated. The melt flow rate (MFR) values decreased with the corn cob content and increased with the addition of lavender stem. Mechanical tests showed that the tensile and flexural modulus of the composites increased and the strengths decreased with the reinforcement material content. The rigidness of PLA slightly decreased with the addition of fillers. There was no significant effect on the thermal properties. The unremarkable improvement of the reinforcement was due to the lack of appropriate adhesion of the two phases. The structure of the compounds was found to be homogenous on the scanning electron microscopy (SEM) micrographs. The incorporation of corn cob and lavender stem can reduce the production cost of materials.
Viktória Kunsági, Péter Széplaki, Márton Tomin
Vol. 19., No.7., Pages 706-725, 2025
DOI: 10.3144/expresspolymlett.2025.54
Vol. 19., No.7., Pages 706-725, 2025
DOI: 10.3144/expresspolymlett.2025.54

In this study, we investigated the influence of processing parameters on the cellular structure and density of specimens fabricated using in-situ foam 3D printing. First, we conducted a comprehensive analysis to examine how the combined effects of printing temperature and speed influence the four key stages of the foaming process: gas dissolution, cell nucleation, cell growth, and stabilization. By evaluating the structural characteristics of the printed foams, we identified the dominant mechanisms governing each stage. Next, we explored the effect of nozzle diameter, an aspect previously unexamined in the literature. We found that smaller nozzle diameters promote higher cell density due to enhanced pressure drop and shear-induced nucleation, resulting in a 36.78% reduction in density and a 60.31% increase in cell density when using a 0.4 mm nozzle instead of 0.8 mm (at 240°C, 60 mm/sec). Finally, we fabricated functionally graded four-layer structures by adjusting the printing temperature for each layer to control porosity distribution. To evaluate the mechanical performance of these graded structures, we performed three-point bending and drop-weight impact tests, allowing us to assess how layer order influences mechanical properties. Our results showed that proper layer sequencing can increase flexural strength by up to 69.35% and improve perforation energy by more than 94.82% compared to homogeneous structures.
Seisuke Ata, Takumi Ono, Motonari Shibakami
Vol. 19., No.6., Pages 628-635, 2025
DOI: 10.3144/expresspolymlett.2025.47
Vol. 19., No.6., Pages 628-635, 2025
DOI: 10.3144/expresspolymlett.2025.47

This study demonstrated, for the first time, the successful formation of porous paramylon esters, which were made from euglenoid polysaccharide known as paramylon and short-chain fatty acids, through supercritical CO2 processing. By maintaining a constant ester functional group attached to the paramylon and varying its proportion, distinct porous structures were selectively produced. Solubility parameter estimations indicated that changes in esterification had no significant effect on the solubility of the paramylon esters used in the experiment. Thus, these structural differences are likely attributed to variations in the viscoelastic properties of paramylon esters under supercritical CO2 conditions. Furthermore, thermal conductivity measurements revealed reductions of up to 20%. Intriguingly, substantial decreases in thermal conductivity were observed even at low foaming ratios, achieved through precise control of the porous structure.