Volume 45, Issue 6

This work systematically studies the high strain rate impact behavior of shear thickening fluid (STF) treated carbon fiber-reinforced polymer (CFRP) composites. Two STFs were synthesized, with concentration of 15 wt% and 20 wt%, respectively. The findings shown that STF can considerably enhance the stress response and energy absorption performance of CFRP, and both exhibit obvious strain rate effects. With the rise in the concentration of STF, the peak stress and energy absorption further increase, reaching 32 % and 178 % of their maximum values, respectively. Additionally, the incorporation of 15 wt% STF significantly improved CFRP’s energy absorption efficiency, outperforming pure CFRP by factors of 1.62, 1.85, and 3.35 at various high strain rates. At a 20 wt% STF concentration, these values escalated to 2.75, 2.70, and 3.41, respectively. It is crucial to highlight that the observed enhancements are limited to high strain rate impacts. In contrast, under low strain rate conditions, STF reduces CFRP’s peak stress and energy absorption due to its lubricating effect. Consequently, CFRP-STF composites are more appropriate for environments with higher and faster impact loading, e.g. vehicle collisions and military applications.

Dynamic covalent bonds exhibit excellent reversibility, high sensitivity and flexible designability among all dynamic covalent bonds. Herein, a dynamically covalent cross-linked polymer (CPPHEA) with triazolinedione (TAD)-indole adducts as cross-linking points was constructed, and the CPPHEA˗6 % exhibits good mechanical properties (51 MPa). In addition, the in-situ relaxation fluorescence spectroscopy was used to characterize the dynamic behavior of C–N bonds in force-reversible polymer networks. Overall, our strategy provides a strong basis for the development of covalent crosslinked polymer materials while enhancing mechanical strength and ductility, which is difficult to achieve with conventional chemical approaches.

Polymer nanocomposites (PNCs) have emerged as advanced materials for several crucial applications such as packaging, electronics, pharmaceuticals, construction and transportation. This review work explores the integration of various dispersible nanostructures or nanofillers in the polymeric matrix, and the resultant properties of the nanocomposites specially with respect to packaging applications. With an improved combination of mechanical, thermal, optical and barrier properties along with reduced environmental impact with biodegradable polymers, these PNCs offer durable and sustainable packaging solutions. A comprehensive summary of the recent research work on the preparation and relevant properties of eco-friendly and biodegradable polymer nanocomposites, is presented here with an emphasis on commercial applications. The versatility, enhanced functionalities, and potential for sustainable packaging render the PNCs as valuable materials in the packaging industry. Nanomaterials such as metal oxides, ceramics, carbon based, polymers and hybrids have been summarized for their exclusive characteristics including surface area, magnetic behavior, optical properties, and catalytic activity. These nanofillers dispersed in various polymeric structures have been reported in a wide range of industrial and environmental applications. The diverse combinations of the nanofillers and the polymers are utilized to fabricate the PNCs with desirable characteristics.

Rubber materials, known for their excellent physical and mechanical properties, are widely used in products such as tires, shock absorbers, and conveyor belts. However, most rubbers have a low limiting oxygen index (LOI) and are considered flammable materials, which limit their application in certain fields. Preparing rubber materials with good flame retardancy has become a key research topic. This paper mainly discusses the intrinsic flame retardancy, inorganic filler flame retardancy, nano-technology flame retardancy, and polymer flame retardancy from the aspects of chemical grafting and physical blending. It summarizes the research progress in the field of flame-retardant rubber over the past five years and predicts the research trends of flame-retardant rubber materials.

New category of aromatic polyurethanes with improved thermal stability was prepared. For this purpose, a diol with preformed silicon and ester units was synthesized through reaction of diphenylsilanediol with terephthaloyl chloride in 2:1 mol ratio. After characterization, the diol was reacted with methylene diphenyl diisocyanate and also toluene diisocyanate to prepare related polyurethanes. The polymers were characterized and their properties including molecular weight, viscosity, solubility, crystallinity, thermal behavior and stability, and flame retardancy were investigated and compared. The presence of silicon and ester units, as well as phenylation of backbone led to preparation of new aromatic polyurethanes with improved thermal stability and flame retardancy. The glass transition temperatures of polyurethanes were 132 and 153 °C, and 10 % weight losses were about 265 and 292 °C. Methylene diphenyl diisocyanate-based polymer revealed higher thermal stability and flame retardancy, but lower solubility in comparison to toluene diisocyanate-based polyurethane. Enhancing thermal stability and flame retardancy of polyurethanes is a pathway for extending their applications in modern industries.

This study investigates the impact of sodium alginate (SA) as a biopolymer on the consistency, compaction and consolidation characteristics of soil, specifically for use as a drainage barrier in soil stabilization applications. The research indicates that increasing sodium alginate concentrations in the soil raises the liquid limit (LL) by 51 % and plastic limit (PL) by 30 %, suggesting an interaction between clay particles and the admixture. To enhance the stability of SA, the optimum quantity of SA of 0.75 % was treated with calcium chloride, leading to the synthesis of calcium alginate (CA) using two methods: solvent casting process and hardening method. The study examines the role of cross-linking agents like calcium chloride in enhancing the stability of soil treated with SA for use as a drainage barrier in liner/cover systems. The hydraulic conductivity of untreated and treated soil met the US EPA requirement of 10 −9  cm/s for a low-permeability soil liner. But the SCP-treated sample exhibited more stable hydraulic movement than the others. Also the compression index was increased by 0.012-fold for SCP method when compared with untreated soil, indicating changes in pore space tightness. SEM and FTIR studies were performed to evaluate the efficacy of CA at the microstructural level.