Jemma L. Rowlandson

We report a comprehensive study of the dynamic mechanical properties of polyborosiloxane (PBS) tested using uniaxial compression, shear rheometry, compression DMA, impact loading, and vibrational transmissibility on a commercially available PBS formulation. We report properties for varying orders of magnitude in strain rate and as a function of strain amplitude wherever possible to quantify performance limits of PBS for different loading cases. We observe that in addition to undergoing a viscous to viscoelastic transition, PBS also experiences an increase in damping at sufficiently high strains within the viscoelastic regime, suggesting that losses arising from chain interactions in the polymer backbone decrease the effectiveness of the reversible B:Si in storing elastic energy at high strain rates for a given PBS formulation. Further, our results suggest that the onset of damping increase depends on the strain as well as the strain rate, with transitions occurring at 0.18 s–1, 1.48 s–1, and between 50 and 150 s–1 for strains of 0.03%, 0.7%, and 15%, respectively. These results inform the use of PBS for energy dissipation applications such as impact and vibration damping, as well as serving as a benchmark to aid in cross-comparison of other application-driven work with comparatively limited mechanical test campaigns.

We report a comprehensive study of polyborosiloxane (PBS) dynamic mechanical properties tested using uniaxial compression, shear rheometry, compression DMA, impact loading, and vibrational transmissibility for a commercially available PBS formulation. We report properties for varying orders of magnitude of strain rate and as a function of strain amplitude wherever possible to quantify performance limits of PBS for different loading cases. We observe that in addition to undergoing a viscous to viscoelastic transition, PBS also experiences an increase in damping at sufficiently high strains within the viscoelastic regime, suggesting that losses arising from chain interactions in the polymer backbone decrease the effectiveness of the reversible B:Si in storing elastic energy at high strain rate for a given PBS formulation. Further, our results suggest the onset of damping increase is dependent on the strain as well as the strain rate, with transitions occurring at 0.18 s-1, 1.48 s-1, and between 50-150 s-1 for strains of 0.03%, 0.7%, and 15%, respectively. These results inform the use of PBS for energy dissipation applications such as impact and vibration damping, as well as serve as a benchmark to aid in cross comparison of other applications-driven works with comparatively limited mechanical test campaigns.

Biomass derived carbon as a promising class of sustainable porous materials for hydrogen storage.

Rigid polyurethane (PU) foams are widely used in engineering applications. This is underpinned by their multiscale and hierarchical structure, characterized by a nanometric segmented PU morphology and a closed-pore microstructure which determine the macroscopic material response. This work correlates the macroscopic behavior of rigid polyurethane foams derived from castor oil with their nanomorphological (in the crystalline domains) evolution upon compression. Molecular dynamics (MD) simulations were used to model the behavior of the PU chains in an ellipsoidal closed-pore structure, as well as the foam’s mechanical properties and X-ray diffractogram. Macro-scale experimental and MD simulation results were correlated using the Nagy model to account for strain rate effects. Synchrotron wide-angle X-ray scattering (WAXS) measurements were performed on the foams before and after compression, with the results compared with simulated diffractograms. A shift in the interplane spacing in the semicrystalline phase of the hard PU segments was observed upon compression, indicating a change in the nanostructure resulting from macroscopic mechanical loading.

Sustainable agriculture will play a key role in ensuring food security for the rising global population. Controlled and precision delivery of agrochemicals, such as herbicides and pesticides, plays a critical role in sustainable agriculture. Recently, porous metal-organic frameworks (MOFs) have shown promising results for controlled agrochemical delivery. Because of their low toxicity and biocompatibility, iron-based metal-organic frameworks (Fe-MOFs) are highly suitable for applications in agriculture over many other MOFs. In this study, two iron-based MOFs, MIL-101(Fe) and NH₂-MIL-101(Fe), and their biodegradable polymer composites were studied for controlled herbicide delivery. Two herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid (MCPA), were postsynthetically loaded into these two Fe-MOFs and incorporated into a biodegradable polycaprolactone (PCL) matrix to form composite membranes for ease of handling and delivery. MIL-101(Fe) showed loading capacities of 18.06 and 21.51 wt %, respectively, for 2,4-D and MCPA, while for NH₂-MIL-101(Fe), the loading capacities for the same herbicides were 26.61 and 23.32 wt %. Despite high loading capacity, both MOFs showed a certain degree of degradation during herbicide loading. The release of 2,4-D and MCPA from MIL-101(Fe) and NH₂-MIL-101(Fe) and their PCL composites were studied using UV-visible spectroscopy over a nine-day period. NH₂-MIL-101(Fe) and its PCL composite demonstrated slower and more controlled release profiles of the herbicides compared to MIL-101(Fe) and its composites. The results were also corroborated by computational studies, which showed stronger interactions of the herbicides with NH₂-MIL-101(Fe).

This review provides an overview of porous carbon materials and their hydrogen storage properties with insight on strategic improvement by structural and chemical modifications and current trends of using machine learning and lifecycle assessment.

The ecological and economic benefits of mycelium composites offer a promising opportunity for supporting sustainable development in Africa. This study focuses on assessing the environmental impact of mycelium composites for building and construction (MCBs) by conducting a life cycle assessment (LCA) in the context of Africa. It is demonstrated that the potential environmental impact of MCBs is substantially influenced by the use and source of electrical power for autoclaves, incubators, and ovens, making the culturing and post-processing phases the major environmental hotspots. The impact of MCB production is also relative to the energy mix of specific countries, being higher in countries that rely on fossil fuel energy (e.g., South Africa) and lower in those that rely more on renewable sources (e.g., Democratic Republic of the Congo, DRC). Furthermore, the impact of MCB production is found to be sensitive to travel distance, suggesting that situating production facilities closer to agricultural, agro-industrial, and/or forestry waste sources could be more beneficial than interregional sourcing, for example. It is also demonstrated that MCBs have the potential to be a more ecologically sustainable alternative to some conventional construction materials (e.g., concrete) over an entire life cycle. Based on the insights obtained from this LCA, some recommendations have been proposed to address potential environmental repercussions pre-emptively and proactively: this is particularly important for nations, mainly in the Global South, that exhibit low resilience to climate change due to limited economic resources. Furthermore, with the rapid expansion of mycelium composite technology, there is a need to increase awareness about its potential environmental impact and, ultimately, to mitigate its potential contribution to pressing environmental concerns (e.g., global warming and climate change). Consequently, this study also adds to the existing body of literature on LCA studies, delineating key factors for consideration in future LCA studies and providing guidance for the sustainable establishment and expansion of this technology.