No abstract

Glass fiber (GF) composites are one of the significant challenges in recycling thermoset materials. After pyrolysis, the glass fibers lack sufficient strength and show poor matrix compatibility. Here we have investigated a series of multifunctional silane and silazane agents for surface modification of recycled glass fibers that provide a combination of hydrophobic properties and residual reactive groups on the surface. This allowed testing of interfacial effects from the surface modification as well as a potential synergistic compatibilization using maleated PP (MAPP). The treated GFs were used to prepare new polypropylene (PP) composites by multiple extrusion steps, resulting in a series of composites where the dispersion efficiency was attributed mainly to the surface chemistry and compatibilization effects. The amino-silane modifications of the recycled fibers resulted in further improvements in the mechanical properties of the PP composites in comparison with the hydrophobized GFs. Moreover, synergistic effects from the addition of MAPP were observed with scanning electron microscopy. The results clearly demonstrate that the surface modifications were effective and good alternatives to currently used methods.

No abstract

Agglomerations effects of graphene‐based nanofillers are often reported in the literature to be the main reason on the deterioration of the mechanical properties, especially at high filler loadings. In our study, we focused on the correlated effects of plasma‐treated graphene nanofillers on the curing reaction and mechanical properties of an epoxy matrix. Specifically, we explored the effect of dispersion state, planar size, filler content, surface functionalization and stoichiometric ratio on the epoxy curing process. The surface of the treated graphene nanofillers were studied in detail by X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy and X‐ray diffraction (XRD). The results indicated greater presence of oxygen containing groups with the crystallinity to be unaffected after the plasma process. Dynamic Mechanical Analysis (DMA) was used to assess the changes in both the Tg and the mechanical properties of graphene‐epoxy nanocomposites. Rheological and microscopic data showed that a well‐dispersed material was achieved at high filler loadings with the use of calendaring and plasma functionalization. Although, a well‐dispersed material was achieved on the bulk composite, no further mechanical reinforcement was observed at high filler loadings. The adsorption of epoxy groups onto the graphene nanofillers' surface, leading to a stoichiometric imbalance between the epoxy chains and hardener molecules, was proposed to explain the results.

Although polymer nanocomposites have attracted much attention, their bulk application is limited due to poor manufacturing scalability while maintaining organized microstructures. Active assembly of nanoparticles using magnetic fields is a promising nano-manufacturing method, as it allows control of alignment direction, is inexpensive, non-damaging, scalable and allows organization of fillers by inter-particle motions. This paper describes the design of an automated image capture and magnetic control system to study the alignment of magnetic graphene nanoparticles in an epoxy matrix by applying a low magnetic field (∼100 mT) and by the automatic image capture of magnetization effects through an optical microscope. This system can continuously observe the alignment process, providing more accurate information about the behavior of the nanoparticle orientation compared to a manual method that only allowed observation of the sample after the experiment had been conducted. A better understanding of nanoparticle alignment could lead to the development of composites with oriented carbon-based nanoparticle structures.