Multicomponent polysaccharide alginate-based bioinks

3D-Bioprinting has seen a rapid expansion in the last few years, with an increasing number of reported bioinks. Alginate is a natural biopolymer that forms hydrogels by ionic cross-linking with calcium ions. Due to its biocompatibility and ease of gelation, it is an ideal ingredient for bioinks. This review focuses on recent advances on bioink formulations based on the combination of alginate with other polysaccharides. In particular, the molecular weight of the alginate and its loading level has an impact on materials performance, as well as the loading of the divalent metal salt and its solubility, which affects the cross-linking of the gel. Alginate is often combined with other polysaccharides that can sigificantly modify the properties of the gel, and can optimise alginate for use in different biological applications. It is also possible to combine alginate with sacrificial polymers, which can temporarily reinforce the 3D printed construct, but then be removed at a later stage. Other additives can be formulated into the gels to enhance performance, including nanomaterials that tune rheological properties, peptides to encourage cell adhesion, or growth factors to direct stem cell differentiation. The ease of formulating multiple components into alginate gels gives them considerable potential for further development. In summary, this review will facilitate the identification of different alginate-polysaccharide bioink formulations and their optimal applications, and help inform the design of second generation bioinks, allowing this relatively simple gel system to achieve more sophisticated control over biological processes

Natural Rubber and Rubber Blend Nanocomposites

Natural rubber (NR) is representative biomass polymer and the effective uses are strongly contributed to sustainable society. This chapter presents the innovative and advanced rubber nanocomposites with polystyrene-encapsulated silica nanohybrids (PS-nSiO2) subsequently used as a nanofiller for NR and NR/styrene butadiene rubber (NR/SBR). The PS-nSiO2 were prepared via ‘in situ' differential microemulsion polymerization. The core-shell nanohybrids of PS-nSiO2 were achieved with an average diameter of 40 nm using a smaller amount of surfactant, compared to microemulsion polymerization method. Moreover, the effects of the NR and NR/SBR filled with PS-nSiO2 nanohybrids on the mechanical properties, thermal stability, flammability and morphology are also discussed. The results indicated that the encapsulation of nSiO2 with PS can provide not only the well-dispersion of nanoparticles in the rubber matrix but also the synergistic properties of two components from the polymer and the inorganic nanoparticles by improving mechanical properties, thermal stability and flammability of rubber nanocomposites. </jats:p

Use of Carbon Nanotube and Nanosilica as Reinforcement Nanofillers in NR/SBR Blended Latex

The blended latex of natural rubber (NR) and styrene butadiene rubber (SBR) at dry weight ratio of 80/20 (NR/SBR) was reinforced with a very low loading level of either carbon nanotube (CNT) or nanosilica (nano-SiO2) (0.1-0.4 phr). The CNT and nano-SiO2 were compounded with NR/SBR rubber blend and other chemicals necessary for vulcanization in the latex state. The obtained nanocomposite latex was cast into thin sheet on a glass mold and then cured in an oven at 80°C for 3 h. The cured samples were subjected to the tensile, dynamic mechanical and thermal tests. The results revealed that the nanofillers have improved their tensile strength, modulus at 300% strain, dynamic mechanical properties and thermal stability but reduced the elongation at break. It was also observed that at similar nanofiller loadings the reinforcing effects of CNT are more noticeable than that of nano-SiO2.</jats:p

Effects of Carbon Black and Carbon Nanotube on Mechanical and Thermal Properties of 80NR/20SBR Composites

This work aims to investigate the effects of carbon black (CB) and carbon nanotube (CNT) on mechanical properties and thermal behaviors of natural rubber (NR)/styrene butadiene rubber (SBR) blend at NR/SBR weight ratio of 80/20. CB loadings from 3-9 phr and CNT with 0.1-0.4 phr loadings were used as fillers in this study. The composites were prepared by latex compounding method. The specimens were examined for their tensile and dynamic mechanical properties and thermal stability using the universal testing machine, dynamic mechanical analyzer and thermal gravimetric analyzer, respectively. The tensile strength and modulus of the composites were improved as a result of the incorporation of CB and CNT. Dynamic mechanical analysis showed that the CB and CNT filled composites possessed high stiffness and low damping characteristics. Thermal stability of the composites was also proved to be better than the unfilled-rubber blend.</jats:p

Superabsorbent cellulose-based hydrogels cross-liked with borax

AbstractCellulose, the most abundant biopolymer on Earth, has been widely attracted owing to availability, intoxicity, and biodegradability. Environmentally friendly hydrogels were successfully prepared from water hyacinth-extracted cellulose using a dissolution approach with sodium hydroxide and urea, and sodium tetraborate decahydrate (borax) was used to generate cross-linking between hydroxyl groups of cellulose chains. The incorporation of borax could provide the superabsorbent feature into the cellulose hydrogels. The uncross-linked cellulose hydrogels had a swelling ratio of 325%, while the swelling ratio of the cross-linked hydrogels could achieve ~ 900%. With increasing borax concentrations, gel fraction of the cross-linked hydrogels increased considerably. Borax also formed char on cellulose surfaces and generated water with direct contact with flame, resulting in flame ignition and propagation delay. Moreover, the cross-linked cellulose-based hydrogels showed antibacterial activity for gram-positive bacteria (S. aureus). The superabsorbent cross-linked cellulose-based hydrogels prepared in this work could possibly be used for wound dressing, agricultural, and flame retardant coating applications.</jats:p

Effects of Carbon Nanotube on Tensile and Dynamic Mechanical Properties of NR/SBR and NR/XSBR Nanocomposites Prepared by Latex Compounding

In this study, natural rubber/styrene butadiene rubber (NR/SBR) and NR/carboxylated styrene butadiene rubber (NR/XSBR) nanocomposites with carbon nanotube (CNT) were prepared by a latex compounding method. The dry weight ratio of either NR/SBR or NR/XSBR was fixed to 80/20 and the CNT loading in each blend was varied from 0.1 to 0.4 phr. The nanocomposite latices were cast into sheets on a glass mold and then cured at 80°C for 3 h. The tensile properties (tensile strength, modulus at 300% strain, elongation at break) and dynamic mechanical properties (storage modulus, loss tangent) of the vulcanizates were then evaluated. The results showed that the addition of CNT at a very loading could enhance the tensile strength, modulus at 300% strain and storage modulus of these two rubber bends in a dose dependent manner, except that the tensile strength peaked at an optimum filler level, declining at higher filler loadings, whilst the elongation at break deteriorated. Moreover, the tensile strength and modulus at 300% strain of the NR/XSBR nanocomposites appeared to be higher than those of the NR/SBR nanocomposites at the same CNT loadings.</jats:p