Simultaneously improving toughness and UV-resistance of polylactide/titanium dioxide nanocomposites by adding poly(ether)urethane

A new strategy for the preparation of polylactic acid composites with UV resistance, light conversion, and antibacterial properties

A novel rare earth complex, Eu(IAA)2(phen)2 (EuIP), was synthesized by solution-based synthesis method. Then, EuIP and polylactic acid (PLA) were melt-blended at 190 °C to obtain a multifunctional PLA/EuIP composite. The incorporation of EuIP provided PLA/EuIP composites with good light conversion ability. Under UV irradiation, PLA/EuIP composites converted the absorbed UV light into red light. Moreover, the PLA/1.0EuIP composite exhibited excellent light transmittance of 88 % in the visible region and showed strong red emission under UV light. After UV irradiation for 96 h, the molecular weights and mechanical properties of neat PLA decreased dramatically. Interestingly, the molecular weights and mechanical properties of PLA/EuIP composites did not deteriorate after 96 h of UV irradiation. The reason was that EuIP could absorb UV light and utilize the absorbed energy to emit red fluorescence. Furthermore, PLA/EuIP composites showed good antibacterial activities against E. coli and S. aureus. In addition, in vitro cell experiments showed that PLA/EuIP composites was suitable for the growth of murine breast cancer (4 T1) cells. Besides, enzymatic degradation testing also proved that PLA/EuIP composites had good biodegradability. This work provides an ingenious design strategy for the preparation of PLA/EuIP composites possessing light conversion ability, UV resistance, and antibacterial properties.

Melt blending of poly(lactic acid) with biomedically relevant polyurethanes to improve mechanical performance

Minimally invasive surgery procedures are of utmost relevance in clinical practice. However, the associated mechanical stress on the material poses a challenge for new implant developments. In particular PLLA, one of the most widely used polymeric biomaterials, is limited in its application due to its high brittleness and low elasticity. In this context, blending is a conventional method of improving the performance of polymer materials. However, in implant applications and development, material selection is usually limited to the use of medical grade polymers. The focus of this work was to investigate the extent to which blending poly-l-lactide (PLLA) with low contents of a selection of five commercially available medical grade polyurethanes leads to enhanced material properties. The materials obtained by melt blending were characterized in terms of their morphology and thermal properties, and the mechanical performance of the blends was evaluated taking into account physiological conditions. From these data, we found that mixing PLLA with Pellethane 80A is a promising approach to improve the material's performance, particularly for stent applications. It was found that PLLA/Pellethane blend with 10% polyurethane exhibits considerable plastic deformation before fracture, while pure PLLA fractures with almost no deformation. Furthermore, the addition of Pellethane only leads to a moderate reduction in elongation at yield and yield stress. In addition, dynamic mechanical analysis for three different PLLA/Pellethane ratios was performed to investigate thermally induced shape retention and shape recovery of the blends.

The Aging of Polymers under Electromagnetic Radiation

Polymeric materials degrade as they react with environmental conditions such as temperature, light, and humidity. Electromagnetic radiation from the Sun's ultraviolet rays weakens the mechanical properties of polymers, causing them to degrade. This study examined the phenomenon of polymer aging due to exposure to ultraviolet radiation. The study examined three specific objectives, including the key theories explaining ultraviolet (UV) radiation's impact on polymer decomposition, the underlying testing procedures for determining the aging properties of polymeric materials, and appraising the current technical methods for enhancing the UV resistance of polymers. The study utilized a literature review methodology to understand the aging effect of electromagnetic radiation on polymers. Thus, the study concluded that using additives and UV absorbers on polymers and polymer composites can elongate the lifespan of polymers by shielding them from the aging effects of UV radiation. The findings from the study suggest that thermal conditions contribute to polymer degradation by breaking down their physical and chemical bonds. Thermal oxidative environments accelerate aging due to the presence of UV radiation and temperatures that foster a quicker degradation of plastics.

Effects of Titanium-Silica Oxide on Degradation Behavior and Antimicrobial Activity of Poly (Lactic Acid) Composites

A mixed oxide of titania-silica oxides (Ti_xSi_y oxides) was successfully prepared via the sol-gel technique from our previous work. The use of Ti_xSi_y oxides to improve the mechanical properties, photocatalytic efficiency, antibacterial property, permeability tests, and biodegradability of polylactic acid (PLA) was demonstrated in this study. The influence of different types and contents of Ti_xSi_y oxides on crystallization behavior, mechanical properties, thermal properties, and morphological properties was presented. In addition, the effect of using Ti_xSi_y oxides as a filler in PLA composites on these properties was compared with the use of titanium dioxide (TiO₂), silicon dioxide (SiO₂), and TiO₂SiO₂. Among the prepared biocomposite films, the PLA/Ti_xSi_y films showed an improvement in the tensile strength and Young's modulus (up to 5% and 31%, respectively) in comparison to neat PLA films. Photocatalytic efficiency to degrade methylene blue (MB), hydrolytic degradation, and in vitro degradation of PLA are significantly improved with the addition of Ti_xSi_y oxides. Furthermore, PLA with the addition of Ti_xSi_y oxides exhibited an excellent antibacterial effect on Gram-negative bacteria (Escherichia coli or E. coli) and Gram-positive bacteria (Staphylococcus aureus or S. aureus), indicating the improved antimicrobial effectiveness of PLA composites. Importantly, up to 5% Ti_xSi_y loading could promote more PLA degradation via the water absorption ability of mixed oxides. According to the research results, the PLA composite films produced with Ti_xSi_y oxide were transparent, capable of screening UV radiation, and exhibited superior antibacterial efficacy, making them an excellent food packaging material.

Developing a cerium lactate antibacterial nucleating agent for multifunctional polylactic acid packaging film

With the rapid development of the packaging industry, people have high requirements for the functionality of packaging materials. As a representative biodegradable packaging material, polylactic acid (PLA) still has some problems. Multifunctional additives in PLA are an effective modification method. In this paper, cerium lactate (Ce-LA) was synthesized by a precipitation method and integrated into PLA to prepare a functional PLA composite. The results showed that Ce-LA not only significantly improved the crystallinity but also imparted antibacterial ability to PLA. When the concentration of Ce-LA was 0.9 %, the crystallinity of PLA reached 39.35 %, which was 77 % higher than that of pure PLA. When the addition of Ce-LA was 1.8 %, the antibacterial rates of PLA against Staphylococcus aureus and Escherichia coli reached 93 % and 85 %, respectively. This study provides a beneficial solution for the development of PLA packaging materials with high crystallinity and antibacterial properties.

Effect of ultrahigh-pressure treatment on the functional properties of poly(lactic acid)/ZnO nanocomposite food packaging film

BACKGROUND

Our living environment is being increasingly polluted by petroleum-based plastics and there is an increasing demand for biodegradable food packaging. In this study, the effect of various ultrahigh-pressure (UHP) treatments (0, 200 and 400 MPa) on the microstructure and thermal, barrier and mechanical properties of poly(lactic acid) (PLA)/ZnO nanocomposite films was studied.

RESULTS

The film-forming solution was processed using UHP technology. The crystallinity, strength and stiffness of the composite film after UHP treatment increased. In addition, barrier property analysis showed that the UHP treatment significantly (P < 0.05) reduced the oxygen permeability and water vapor permeability (WVP) coefficient of the PLA/ZnO nanocomposite film. Furthermore, the WVP value of the film treated at 400 MPa (50 g kg^-1 nano-ZnO content) was the lowest and reduced by 47.3% compared with that of pure PLA film. The improvement in these properties might be due to the interaction between nano-ZnO and PLA matrix promoted by UHP treatment.

CONCLUSIONS

Therefore, the application of UHP technology on the film-forming solution could improve the crystallinity and functional properties of the nanocomposite film, and has great potential in the production of food packaging films with ideal functions. © 2021 Society of Chemical Industry.

The synthesis of monodispersed M-CeO2/SiO2nanoparticles and formation of UV absorption coatings with them

CeO₂/polymer nanoparticles have drawn considerable attention for their excellent UV absorption properties. However, many challenges still exist in the successful incorporation of ceria into the polymer matrix for the easy agglomeration and photocatalytic activity of CeO₂ nanoparticles. Herein, we address these issues by constructing three-layer structured nanoparticles (M-CeO₂@SiO₂) and incorporating them into a polymer matrix through a mini-emulsion polymerization process. During this process, small-sized nano-ceria became uniformly anchored on the surfaces of monodisperse silica particles first, and then the particles were coated with an MPS/SiO₂ shield. The morphology and dispersion of the nanoparticles were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The performance of the hybrid films was characterized using UV-vis absorption spectroscopy (UV-vis) and water contact angle (WCA) measurements. Results showed that the M-CeO₂@SiO₂ nanoparticles exhibited a three-layer structure with a mean diameter of 360 nm, and they possess good compatibility with acrylic monomers. After the addition of M-CeO₂@SiO₂, hybrid films exhibited enhanced UV absorption capacity as expected, accompanied by an obvious improvement in hydrophobicity (the water contact angle increased from 84.2° to 98.2°). The results showed that the hybrid films containing M-CeO₂@SiO₂ particles possess better global performance as compared with those containing no particles.

Herein, we report the synthesis of monodispersed M-CeO₂/SiO₂ nanoparticles and their use in the construction of a UV absorption coating.

Interactive effects of solar UV radiation and climate change on material damage

Solar UV radiation adversely affects the properties of organic materials used in construction, such as plastics and wood.

Meat packaging solutions to current industry challenges: A review

Many advances have occurred in the field of smart meat packaging, and the potential for these to be used as tools that respond to challenges faced by industry is exciting. Here, we review packaging solutions to several immediate concerns, encompassing dark cutting, purge and yield losses, product traceability and provenance, packaging durability, microbial spoilage and safety, colour stability, environmental impacts, and the preservation of eating quality. Different active and intelligent packaging approaches to each of these were identified and are discussed in terms of their usefulness - to processors, retailers and/or consumers. From this, it became apparent that prior to selecting a packaging solution, industry should first define their criteria for success (e.g. How much purge is too much? What is a reasonable shelf-life to facilitate product turnover? Is the customer willing to pay for this?), and understand that packaging is not the sole solution, but acts as part of a holistic response to these issues.

Environmental effects of ozone depletion, UV radiation and interactions with climate change: UNEP Environmental Effects Assessment Panel, update 2017

The Environmental Effects Assessment Panel (EEAP) is one of three Panels of experts that inform the Parties to the Montreal Protocol. The EEAP focuses on the effects of UV radiation on human health, terrestrial and aquatic ecosystems, air quality, and materials, as well as on the interactive effects of UV radiation and global climate change. When considering the effects of climate change, it has become clear that processes resulting in changes in stratospheric ozone are more complex than previously held. Because of the Montreal Protocol, there are now indications of the beginnings of a recovery of stratospheric ozone, although the time required to reach levels like those before the 1960s is still uncertain, particularly as the effects of stratospheric ozone on climate change and vice versa, are not yet fully understood. Some regions will likely receive enhanced levels of UV radiation, while other areas will likely experience a reduction in UV radiation as ozone- and climate-driven changes affect the amounts of UV radiation reaching the Earth's surface. Like the other Panels, the EEAP produces detailed Quadrennial Reports every four years; the most recent was published as a series of seven papers in 2015 (Photochem. Photobiol. Sci., 2015, 14, 1-184). In the years in between, the EEAP produces less detailed and shorter Update Reports of recent and relevant scientific findings. The most recent of these was for 2016 (Photochem. Photobiol. Sci., 2017, 16, 107-145). The present 2017 Update Report assesses some of the highlights and new insights about the interactive nature of the direct and indirect effects of UV radiation, atmospheric processes, and climate change. A full 2018 Quadrennial Assessment, will be made available in 2018/2019.