The low-percolation-threshold conductive networking structure is indispensable for the high performance and functionalization of conductive polymer composites (CPCs). In this work, conductive carbon black (CCB)-reinforced ultrahigh-molecular-weight polyethylene (UHMWPE)/polypropylene (PP) blend with tunable electrical conductivity and good mechanical properties was prepared using a high-speed mechanical mixing method and a compression-molded process. An interconnecting segregated hybrid CCB–polymer network is formed in electrically conductive UHMWPE/PP/CCB (UPC) composites. The UPC composites possess a dense conductive pathway at a low percolation threshold of 0.48 phr. The composite with 3 phr CCB gives an electrical conductivity value of 1.67 × 10^–3 S/cm, 12 orders of magnitude higher than that of the polymeric matrix, suggesting that CCB improves both the electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) of the composite at the loading fraction over its percolation threshold. The composite with 15 phr CCB presents an absorption-dominated electromagnetic interference shielding effectiveness (EMI SE) as high as 27.29 dB at the X-band. The composite also presents higher tribological properties, mechanical properties, and thermal stability compared to the UP blend. This effort provides a simple and effective way for the mass fabrication of CPC materials with excellent performance.

Tuning the high properties of segregated conductive polymer materials (CPCs) by incorporating nanoscale carbon fillers has drawn increasing attention in the industry and academy fields, although weak interfacial interaction of matrix-filler is a daunting challenge for high-loading CPCs. Herein, we present a facile and efficient strategy for preparing the segregated conducting ultra-high molecular weight polyethylene (UHMWPE)-based composites with acceptable mechanical properties. The interfacial interactions, mechanical properties, electrical properties and electromagnetic interference (EMI) shielding effectiveness (SE) of the UHMWPE/conducting carbon black (CCB) composites were investigated. The morphological and Raman mapping results showed that UHMWPE/high specific surface area CCB (h-CCB) composites demonstrate an obviously interfacial transition layer and strongly interfacial adhesion, as compared to UHMWPE/low specific surface area CCB (l-CCB) composites. Consequently, the high-loading UHMWPE/h-CCB composite (beyond 10 wt% CCB dosage) exhibits higher strength and elongation at break than the UHMWPE/l-CCB composite. Moreover, due to the formation of a densely stacked h-CCB network under the enhanced filler-matrix interfacial interactions, UHMWPE/h-CCB composite possesses a higher EMI SE than those of UHMWPE/l-CCB composites. The electrical conductivity and EMI SE value of the UHMWPE/h-CCB composite increase sharply with the increasing content of h-CCB. The EMI SE of UHMWPE/h-CCB composite with 10 wt% h-CCB is 22.3 dB at X-band, as four times that of the UHMWPE/l-CCB composite with same l-CCB dosage (5.6 dB). This work will help to manufacture a low-cost and high-performance EMI shielding material for modern electronic systems.

A major challenge in waste rubber (WR) industry is achieving a high sol fraction and high molecular weight of recycled rubber at the same time. Herein, the WR from the shoe industry was thermo-mechanically ground via the torque rheometer. The effect of grinding temperature and filling rate were systematically investigated. The particle size distribution, structure evolution, and morphology of the recycled rubber were explored by laser particle size analyzer, Fourier transform infrared spectroscopy (FTIR), sol fraction analysis, gel permeation chromatography (GPC), differential scanning calorimeter (DSC), and scanning electron microscope (SEM). The results indicate that the thermo-mechanical method could reduce the particle size of WR. Moreover, the particle size distribution of WR after being ground can be described by Rosin’s equation. The oxidation reaction occurs during thermal-mechanical grinding. With the increase of the grinding temperature and filling rate, the sol fraction of the recycled WR increases. It is also found that a high sol fraction (43.7%) and high molecular weight (35,284 g/mol) of reclaimed rubber could be achieved at 80 °C with a filling rate of 85%. Moreover, the obtained recycled rubber compound with SBR show a similar vulcanization characteristics to pure SBR. Our selective decomposition of waste rubber strategy opens up a new way for upgrading WR in shoe industry.

Chloride-induced corrosion of reinforcing steel is a major cause of durability deterioration in reinforced concrete, whereas the efficiency of layered double hydroxides (LDHs) is often limited by agglomeration in cementitious systems. This study investigated a NO2-intercalated LDH/montmorillonite composite (NO2-LDHs@MMT) as a multifunctional additive for improving chloride resistance and corrosion protection, with NO2-LDHs as a reference. Rapid chloride migration (RCM), open-circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and Tafel polarization were combined with a coupled chloride transport-corrosion model. Both additives reduced chloride migration, but NO2-LDHs@MMT showed the stronger effect. At 2 wt.% of binder, the chloride migration coefficient decreased from 14.3 × 10−12 to 8.3 × 10−12 m2/s, corresponding to a 41.95% reduction. Under electrically accelerated chloride ingress, the 2 wt.% NO2-LDHs@MMT specimen maintained a more positive OCP (−0.279 V vs. SCE at 162 h), a much higher charge-transfer resistance (3010 kΩ·cm2), and a markedly lower corrosion current density (0.0312 × 10−5 A·cm−2) than the blank specimen, yielding an inhibition efficiency of 99.5%. The coupled model reproduced the measured corrosion current with a simulated-to-measured ratio of 0.918-0.97 and predicted lower chloride accumulation, thinner corrosion products, and less damage during 300 d exposure. The improved performance of NO2-LDHs@MMT is associated with chloride capture, better LDH dispersion, and a larger effective interaction interface provided by MMT.

The damage process of a component/structure results from the continuous evolution and accumulation of material deterioration. A higher degree of damage indicates a more severe structural condition. This study investigated the seismic damage behavior of unsymmetrical steel-reinforced concrete (USRC) columns through low cyclic loading tests conducted on eight specimens. The height range corresponding to the most unfavorable damage section of the columns was examined. The correlation between the damage evolution of single- and multi-point concrete materials and the plastic development of components was established using embedded piezoelectric transducers and the stress transformation damage factor. The average concrete compression damage factor in the most unfavorable damage section was adopted as the overall damage evaluation index of the components, enabling the development of a “material-section-component” multilevel damage evaluation correlation. The evaluation results were in good agreement with those of the classic Park-Ang model. The findings provide valuable insights for structural damage assessment following seismic events.