The Normal Force Characteristic of a Novel Magnetorheological Elastomer Based on Butadiene Rubber Matrix Compounded with the Self-Fabricated Silly Putty

In this paper, a novel magnetorheological elastomer (MRE) was prepared by dispersing carbonyl iron particles (CIPs) into a composite matrix compounded by butadiene rubber (BR) and self-fabricated Silly Putty. The rate-sensitive and magneto-induced characteristics of normal force were experimental investigated to discuss the working mechanism. The results demonstrated that the normal force increased with the compression rate and the mass fraction of boron-silicon copolymer added to the composite matrix due to the formation of the more and more B-O cross bonds which could be blocked in the C-C cross-linked network of BR. Meanwhile, the magneto-induced normal force was positively correlated with the applied magnetic field strength and the compression strain due to the decreased gap between the centers of soft magnetic particles and the increased particle intensity of magnetization. Moreover, the magneto-induced normal force continued to enhance with the increase of compression strain because the CIP chains fixed in the C-C cross-linked network could bend to a radian and CIP chains in B-O cross-linked network could rupture to form more stable and intensive short-chain structures. Besides, a simplified model was deduced to characterize the mechanism of the generation of the magneto-induced normal force. Furthermore, the normal force varied stably with the oscillatory shear strain (less than 9%) at different magnetic induction intensities and suddenly reduced when the applied oscillatory shear strain was more than 9%.

Impact of Carbon Particle Character on the Cement-Based Composite Electrical Resistivity

Electroconductive cement-based composites are modern materials that are commonly used in many industries such as the construction industry, among others. For example, these materials can be used as sensors for monitoring changes in construction, grounding suspension, and resistance heating materials, etc. The aim of the research presented in this article is to monitor the impact of carbon particle character on cement-based electroconductive composites. Four types of graphite were analyzed. Natural and synthetic types of graphite, with different particle sizes and one with improved electrically conductive properties, were tested. For the analysis of the electrical conductivity of powder raw materials, a new methodology was developed based on the experience of working with these materials. Various types of graphite were tested in pure cement paste (80% cement, 20% graphite) as well as in a composite matrix, which consisted of cement (16.8%), a mixture of silica sand 0–4 mm (56.4%), graphite filler (20.0%) ground limestone (6.7%) and super plasticizers (0.1%). The resistivity and physical-mechanical properties of the composite material were determined. Furthermore, the resistivity of the test samples was measured with a gradual decrease in saturation. It may be concluded that graphite fillers featuring very fine particles and high specific surface are most suitable and most effective for creating electrically conductive silicate composites. The amount, shape and, in particular, the fineness of the graphite filler particles thus creates suitable conditions for the creation of an integrated internal electricity-conductive network. In the case of the use of a coarse type of graphite or purely non-conductive fillers, the presence of an electrolyte, for example, in the form of water, is necessary to achieve a low resistivity. Samples with fine types of graphite fillers achieved stable resistivity values when the sample humidity changed. The addition of graphite fillers caused a large decrease in the strength of the samples.

On PVC-PP composite matrix for 4D applications: Flowability, mechanical, thermal, and morphological characterizations

Thermoplastics such as; polyvinyl chloride (PVC) and polypropylene (PP) have applications in different sectors such as; automobile, aerospace, biomedical, textile etc. due to cost-effectiveness, biodegradability, high mouldability, easy availability and good mechanical properties. The shape memory performances of these thermoplastics are crucial for extending the four-dimensional (4D) printing applications. But hitherto little has been reported on flowability, mechanical, thermal, morphological and shape memory properties of PVC-PP composite. In this study, twin-screw compounding has been employed on PVC and PP thermoplastics (in single and blended form) to prepare feedstock filaments for fused filament fabrication (FFF). The investigations have been made for flowability (melt flow index (MFI), mechanical (tensile strength and elongation), thermal (melting point) morphological, Fourier transform infrared spectroscopy (FTIR) analysis, and shape memory effect on different feedstock filaments (prepared with neat PVC, 75%PVC-25%PP, 50%PVC-50%PP, 25%PVC-75%PP, and neat PP). The results have been supported by fracture analysis of photomicrographs obtained from scanning electron microscopy (SEM). The results of the study suggested that tensile strength was maximum for 50%PVC-50%PP (23.57 MPa) and minimum for neat PP (8.89 MPa). Further percentage shape recovery was observed maximum for neat PVC and minimum for neat PP.

Rheological behavior of the composite matrix Diglycidylether of bisphenol-A (DGEBA/wt% blast furnace slag (BFS)

This paper reports experiments on the rheological behavior of DGEBA epoxy resin filled with blast furnace slag nanoparticles. The study of the variation of stress and viscosity as a function of shear rate is emphasized. The purpose of this study is to investigate the rheological behavior of DGEBA loaded with blast furnace slag (BFS), the selected mixtures cannot exceed 10% in wt%, given the fineness of grinding which SSB= 44.5 m2.g-1. We tested the compositions of DGEBA/%wt blast furnace slag (BFS) at filling ratios of (10, 20, 30, 40 and 50%). Viscosity and shear stress as a function of temperature and filler rate were investigated. In this study, formulations were developed to test the best compositions with favorable rheological behavior for better processing of these matrices.