Publications by authors named "Koon-Yang Lee"

The mechanical performance of mixed plastic waste from shredder residue is hindered by brittleness and catastrophic failure, limiting its potential applications. In this study, the mechanical properties of mixed plastic is enhanced by reinforcement with rayon fibers through a wet powder impregnation process to leverage the fiber's ductility and entanglement. However, mixed plastic remains poorly dispersed in water during the composite manufacturing, resulting in poorly consolidated composite, which further deteriorates the mechanical properties of mixed plastic from 1.

View Article and Find Full Text PDF

Empty fruit bunch (EFB), an abundant lignocellulosic residue from the palm oil milling process, is typically discarded on open land or used as mulch. In this work, a simple method that mimics a papermaking process, was developed to upcycle EFB into higher value fibreboard without the need for any polymeric binders. The cellulose network from pulp fibres was utilised to hold the otherwise loose EFB fibres together to produce a rigid EFB fibreboard.

View Article and Find Full Text PDF
Article Synopsis
  • Melt blending of immiscible polymer blends from industrial mixed plastic waste leads to poor mechanical performance due to brittleness and stress concentration points.
  • Conversely, a more heterogeneous mixed plastic blend with larger single polymer domains shows better ductility and improved fracture toughness under tension.
  • The study suggests that utilizing mixed plastic waste instead of melting them can enhance their mechanical properties, making them more suitable for engineering applications and reducing landfill waste.
View Article and Find Full Text PDF

Cellulose nanopaper is a material structure that possesses high mechanical performance and is widely regarded as a promising 2D reinforcement for polymer matrix composites. This work explores the use of low grammage bacterial cellulose (BC) nanopaper as reinforcement for poly(acrylated urethane) interlayer adhesive to increase the impact performance of multilayer acrylic composites. The BC nanopaper is impregnated with an acrylated urethane resin and laminated between acrylic sheets to create BC/acrylic composites consisting of one, three, and five layers of BC nanopaper-reinforced poly(acrylated urethane) interlayer adhesive(s).

View Article and Find Full Text PDF

Environmental concerns are driving interest in postpetroleum synthetic textiles produced from microbial and fungal sources. Bacterial cellulose (BC) is a promising sustainable leather alternative, on account of its material properties, low infrastructure needs and biodegradability. However, for alternative textiles like BC to be fully sustainable, alternative ways to dye textiles need to be developed alongside alternative production methods.

View Article and Find Full Text PDF

Ineffective sorting of post-consumer plastics remains one of the major obstacles in the recycling of plastics. Consequently, these highly heterogeneous, mixed post-consumer plastics will end up in landfill or have to be incinerated as repurposing them directly would lead to a polymer blend with inferior quality for many end-uses. In this work, we demonstrate the use of carbon fibers (CFs) to practically upgrade the mechanical properties of mixed plastics, adding value to them.

View Article and Find Full Text PDF
Article Synopsis
  • Hydrogels made from TEMPO-oxidised cellulose nanofibrils (TOCNs) are usually weak and unstable in water unless they are modified, making it difficult to produce sturdy films from them.
  • This study introduces a method to create strong, water-stable TOCN hydrogels through the oxidation of bacterial cellulose (BC) nanopaper, eliminating the need for added chemicals or crosslinking.
  • The oxidation process significantly increases the hydrogels' swelling abilities and water retention, allowing for easy production of thick, self-standing TOCN films merely by drying the treated hydrogels.
View Article and Find Full Text PDF

Bacteria proficient at producing cellulose are an attractive synthetic biology host for the emerging field of Engineered Living Materials (ELMs). Species from the genus produce high yields of pure cellulose materials in a short time with minimal resources, and pioneering work has shown that genetic engineering in these strains is possible and can be used to modify the material and its production. To accelerate synthetic biology progress in these bacteria, we introduce here the tool kit (KTK), a standardized modular cloning system based on Golden Gate DNA assembly that allows DNA parts to be combined to build complex multigene constructs expressed in bacteria from plasmids.

View Article and Find Full Text PDF

Engineered living materials (ELMs) based on bacterial cellulose (BC) offer a promising avenue for cheap-to-produce materials that can be programmed with genetically encoded functionalities. Here we explore how ELMs can be fabricated in a modular fashion from millimetre-scale biofilm spheroids grown from shaking cultures of Komagataeibacter rhaeticus. Here we define a reproducible protocol to produce BC spheroids with the high yield bacterial cellulose producer K.

View Article and Find Full Text PDF

Thermoplastic elastomers benefit from high elasticity and straightforward (re)processability; they are widely used across a multitude of sectors. Currently, the majority derive from oil, do not degrade or undergo chemical recycling. Here a new series of ABA triblock polyesters are synthesized and show high-performances as degradable thermoplastic elastomers; their composition is poly(cyclohexene--phthalate)--poly(ε-decalactone)--poly(cyclohexene--phthalate) {PE-PDL-PE}.

View Article and Find Full Text PDF

Nanocellulose is typically stored and transported as a gel with a nominal solid content of up to 5 wt.-% to avoid interfibril hornification, i.e.

View Article and Find Full Text PDF

Nanocellulose network in the form of cellulose nanopaper is an important material structure and its time-dependent mechanical response is crucial in many of its potential applications. In this work, we report the influences of grammage and strain rate on the tensile response of bacterial cellulose (BC) nanopaper. BC nanopaper with grammages of 20, 40, 60 and 80 g m were tested in tension at strain rates ranging from 0.

View Article and Find Full Text PDF

The ever-increasing demand for carbon fibre reinforced polymers (CFRP) and stringent environmental legislation have driven the research into recycling and reusing the CFRP waste. This paper presents a mechanical recycling process of CFRP and the application of the recyclates as reinforcement for epoxy foams. The CFRP was mechanically processed using a jet mill.

View Article and Find Full Text PDF

Carbon dioxide/epoxide copolymerization is an efficient way to add value to waste CO and to reduce pollution in polymer manufacturing. Using this process to make low molar mass polycarbonate polyols is a commercially relevant route to new thermosets and polyurethanes. In contrast, high molar mass polycarbonates, produced from CO, generally under-deliver in terms of properties, and one of the most widely investigated, poly(cyclohexene carbonate), is limited by its low elongation at break and high brittleness.

View Article and Find Full Text PDF

The structural component of fungal cell walls comprises of chitin covalently bonded to glucan; this constitutes a native composite material (chitin-glucan, CG) combining the strength of chitin and the toughness of glucan. It has a native nano-fibrous structure in contrast to nanocellulose, for which further nanofibrillation is required. Nanopapers can be manufactured from fungal chitin nanofibrils (FChNFs).

View Article and Find Full Text PDF

Greener alternatives to synthetic polymers are constantly being investigated and sought after. Chitin is a natural polysaccharide that gives structural support to crustacean shells, insect exoskeletons, and fungal cell walls. Like cellulose, chitin resides in nanosized structural elements that can be isolated as nanofibers and nanocrystals by various top-down approaches, targeted at disintegrating the native construct.

View Article and Find Full Text PDF

Cellulose nanofibers are often explored as biobased reinforcement for the production of high-performance composite materials. In this work, we fabricated transparent poly(methyl methacrylate) (PMMA) composites consisting of two-dimensional and three-dimensional bacterial cellulose (BC) nanofiber networks. Three different composite designs consisting of 1 vol % BC loading were fabricated and studied: (i) composites with a three-dimensional BC nanofiber network embedded uniformly throughout the PMMA matrix; (ii) sandwich-structured construction consisting of three-dimensional BC-PMMA sandwiched between two neat PMMA sheets; and (iii) dried and well-consolidated two-dimensional BC nanofiber network embedded in a PMMA matrix.

View Article and Find Full Text PDF

Bacteriophage (phage) have attractive advantages as delivery systems compared with mammalian viruses, but have been considered poor vectors because they lack evolved strategies to confront and overcome mammalian cell barriers to infective agents. We reasoned that improved efficacy of delivery might be achieved through structural modification of the viral capsid to avoid pre- and postinternalization barriers to mammalian cell transduction. We generated multifunctional hybrid adeno-associated virus/phage (AAVP) particles to enable simultaneous display of targeting ligands on the phage's minor pIII proteins and also degradation-resistance motifs on the very numerous pVIII coat proteins.

View Article and Find Full Text PDF

In this research article, wood based microfibrillated cellulose (MFC) was studied to gain a better understanding of the process of dependent network formation. Networking potential and obtained properties of the produced dimensional structures could be controlled using opted processing routes. The fabricated dimensional structure, using freeze-drying (FD) is a highly open and porous network (98% porosity) compared to slightly tight, dense and less porous network produced after pressing at 200kN (96% porosity), followed by vacuum-filtered (VF) networks (33% porosity).

View Article and Find Full Text PDF

Sargassum in the Caribbean region has affected the livelihood of several coastal communities due to the influx of large quantities of the seaweed in recent times. This article seeks to explore how waste Sargassum natans can be utilized to produce sodium alginate. The novelty in this research lies in the optimization process, whereby multistage extraction and precipitation were investigated over commonly used single stage processing, in an effort to maximize both yield and purity.

View Article and Find Full Text PDF
Article Synopsis
  • - Cellulose nanopapers are being increasingly recognized for various applications, including as reinforcements in nanocomposites, substrates for printed electronics, and filters for water treatment, with mechanical properties being crucial for their effectiveness.
  • - These nanopapers can be made by filtering a nanocellulose suspension and then consolidating it with heat, while previous studies have shown that adjusting the fibril size or modifying the fibrils can enhance mechanical properties.
  • - This research demonstrates that blending different grades of nanocellulose, such as bacterial cellulose and softwood pulp-derived cellulose nanofibrils, can lead to improved mechanical characteristics like stiffness and toughness due to synergistic effects.
View Article and Find Full Text PDF

Basic adsorption of hydrophobic polymers from aprotic solvents was introduced as a platform technology to modify exclusively the surfaces of cellulose nanopapers. Dynamic vapor sorption demonstrated that the water vapor uptake ability of the nanopapers remained unperturbed, despite strong repellency to liquid water caused by the adsorbed hydrophobic polymer on the surface. This was enabled by the fact that the aprotic solvents used for adsorption did not swell the nanopaper unlike water that is generally applied as the adsorption medium in such systems.

View Article and Find Full Text PDF

The constituent nanofibrils of bacterial cellulose are of interest to many researchers because of their purity and excellent mechanical properties. Mechanisms to disrupt the network structure of bacterial cellulose (BC) to isolate bacterial cellulose nanofibrils (BCN) are limited. This work focuses on liquid-phase dispersions of BCN in a range of organic solvents.

View Article and Find Full Text PDF
Article Synopsis
  • - This study focuses on creating and analyzing composite materials made from bacterial cellulose (BC) mixed with gelatin, revealing an uneven distribution of BC within the gelatin matrix through advanced imaging techniques.
  • - The composites exhibit varying levels of transparency and UV opacity, with a 10% BC addition causing a reduction in light transmittance of about 35% for visible light and 40% for UV light.
  • - Mechanical properties of the composites were assessed using Raman spectroscopy, showing two linear stress-strain relationships and different effective Young's moduli, suggesting potential applications for these materials in UV protective food coatings.
View Article and Find Full Text PDF

Developing nanomaterials that are effective, safe, and selective for gene transfer applications is challenging. Bacteriophages (phage), viruses that infect bacteria only, have shown promise for targeted gene transfer applications. Unfortunately, limited progress has been achieved in improving their potential to overcome mammalian cellular barriers.

View Article and Find Full Text PDF