ABSTRACT
We successfully prepared butyl rubber (IIR)/polypropylene (PP) thermoplastic vulcanizate (IIR/PP-TPV) for shock-absorption devices by dynamic vulcanization (DV) using octyl-phenolic resin as a vulcanizing agent and studied the morphological evolution and properties during DV. We found that the damping temperature region of the IIR/PP-TPV broadened with the disappearance of the glass transition temperature (Tg) in the PP phase, which is ascribed to the improvement of compatibility between the IIR and PP with increasing DV time. As DV progresses, the size of the dispersed IIR particles and the PP crystalline phase decreases, leading to the formation of a sea-island morphology. After four cycles of recycling, the retention rates of tensile strength and elongation at break of the IIR/PP-TPV reached 88% and 86%, respectively. The size of the IIR cross-linking particles in the IIR/PP-TPV becomes larger after melt recombination, and the continuous PP phase provides excellent recyclability. Significantly, the prepared IIR/PP-TPV exhibits excellent recyclability, high elasticity, and good damping property.
ABSTRACT
Silicon (Si), a high-capacity lithium-ion battery anode material, has aroused wide attention. Its further practical application has been limited by its huge volume change during the cycle. To reduce this defect, the double cross-linked product of glycinamide hydrochloride modified poly(acrylic acid) (PAG) and epoxidized natural rubber (ENR) was developed as a water-based binder to obtain sufficient elasticity and a sufficiently strong adhesive force. Due to the double cross-linked structures in the system, the binder was enabled to effectively disperse and transfer the stress generated by the volume expansion of the Si particles and keep the integrity of the electrode during the cycle, thus obtaining excellent cycle performance. When the current density was 1 A g-1, PE55 (PAG: ENR = 1:1 cross-linked polymer) electrode still achieved a specific capacity of 2322.2 mAh g-1 after 100 cycles of constant current charge and discharge, and PE55 binder exhibited excellent bonding properties (4.45 N) and mechanical properties (stress: 5.51 MPa, strain: 87.4%). The comparison of poly(acrylic acid) (PAA) electrodes suggests that the introduction of elastic polymer and the construction of double cross-linked structures can increase the stability of Si anodes.
ABSTRACT
In this paper, a reduced graphene oxide/polypropylene (rGO/PP) dielectric composite with high dielectric constant and low dielectric loss at a low filler content was prepared via constructing a segregated moderately-reduced graphene network by encapsulation of GO on PP latex particles and subsequent in situ reduction of GO by hydrazine hydrate. GO/PP latex was prepared through artificial PP latex preparation in the presence of GO based on the solution-emulsification technique. As the emulsification proceeded, GO could self-assemble to become encapsulated on the surface of PP latex particles composed of PP and maleic-anhydride-grafted-PP because of the hydrogen bonding interaction between maleic-anhydride-grafted-PP and GO nanosheets. After reduction, the rGO encapsulated PP latex particles were obtained, and after coagulation and hot pressing, a segregated graphene network was achieved at a low content of rGO, demonstrated by TEM images. The dielectric constant at 1 kHz obviously increased from 3.28 for PP to 55.8 for the composite with 1.5 wt% rGO. The dielectric loss of the composite was retained at a low value (1.04). This study provides a new simple and effective strategy for preparing high-performance dielectric composites with high dielectric constant and low dielectric loss, facilitating the wide application of dielectric materials.
ABSTRACT
Effective edge oxidation of graphene with high structural integrity is highly desirable yet technically challenging for most practical applications. In this work, we have developed a green and facile strategy to obtain edge-oxidized graphene with good dispersion stability and high electrical conductivity by exploiting high edge reactivity of highly conductive multi-layer graphene and oxidizing radicals (SO4 -Ë) generated from sodium persulfate (Na2S2O8) with ferrous ion (Fe2+) activation. Owing to high structural integrity of pristine graphene and effective edge oxidation, the obtained edge-oxidized graphene exhibited excellent dispersion stability and satisfactory electrical conductivity (i.e. ≥240 S cm-1). Moreover, the oxidation degree of pristine graphene can be well controlled by adjusting treatment time. The obtained edge-oxidized graphene is expected to find a variety of applications in many fields of anti-static films, energy storage materials, flexible sensors and high-performance nanocomposites.