Characterization of Tensile Properties of Cola lepidota Fibers

Plant fibers are being increasingly explored for their use in engineering polymers and composites, and many works have described their properties, especially for flax and hemp fibers. Nevertheless, the availability of plant fibers varies according to the geographical location on the planet. This study presents the first work on the mechanical properties of a tropical fiber extracted from the bast of Cola lepidota (CL) plant. After a debarking step, CL fibers were extracted manually by wet-retting. The tensile properties are first identified experimentally at the fibers scale, and the analysis of the results shows the great influence of the cross-section parameters (diameter, intrinsic porosities) on these properties. Tensile properties of CL fibers are also predicted by the impregnated fiber bundle test (IFBT). At this scale of bundles, a hackling step, which reduces shives and contributes to the parallelization of the fibers within bundles, improves tensile properties predicted by IFBT. The comparison with the properties of plant fibers given in the literature shows that CL fibers have tensile properties in the same range as kenaf, flax or hemp fibers.

Thin-layer studies on surface functionalization of polyetherimide: Hydrolysis versus amidation

Among the high-performance and engineering polymers, polyimides and the closely related polyetherimide (PEI) stand out by their capability to react with nucleophiles under relatively mild conditions. By targeting the phthalimide groups in the chain backbone, post-functionalization offers a pathway to adjust surface properties such as hydrophilicity, solvent resistance, and porosity. Here, we use ultrathin PEI films on a Langmuir trough as a model system to investigate the surface functionalization with ethylene diamine and tetrakis(4-aminophenyl)porphyrin as multivalent nucleophiles. By means of AFM, Raman spectroscopy, and interfacial rheology, we show that hydrolysis enhances the chemical and mechanical stability of ultrathin films and allows for the formation of EDC/NHS-activated esters. Direct amidation of PEI was achieved in the presence of a Lewis acid catalyst, resulting in free amine groups rather than cross-linking. When comparing amidation with hydrolysis, we find a greater influence of the latter on material properties. Graphic abstract

Biomaterials and Their Applications in Dentistry - A Literature Review

With an estimated 20 million individuals possessing an implanted medical device, biomaterials are now commonly used in medicine and dentistry. Today, biomaterials are widely used in dentistry. Biomaterials are widely used in dentistry. They are divided into four general categories of polymers, ceramics, metals and composites. A variety of dental biomaterials have been developed as clinical needs of dental patients has increased. Newly developed dental biomaterials should be physically stable and biocompatible for their own purposes in oral environment. The extensive use of biomaterials, however, remains a relatively recent concept and dates back to the 1950s. This has contributed to a paradigm shift in the design of biomedical devices over the past 25 years, from being biologically inactive to fully incorporated. By exploring the rationale and clinical demand that have guided both the developments in clinically applied devices and those at the research and development level, this mini review highlights the production and application of biomaterials. Relevant areas of current research activities are addressed and some of the criteria. KEY WORDS Biomaterials, Dental, Tissue Engineering, Polymers, Stem Cell Research

Effects of Reprocessing on Acrylonitrile–Butadiene–Styrene and Additives

Acrylonitrile-butadiene-styrene (ABS) is one of the most extensively used engineering polymers and analysing the chemical structure changes during processing and recycling is extremely important. Hence, in this study, an ABS resin was processed using a torque rheometer at different temperatures and for different numbers of cycles. Pyrolysis gas chromatography mass spectrometry (Py-GC/MS) was used to study the effects of the processing parameters on additives. Fourier transform infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance (1H NMR) spectroscopy, and gel permeation chromatography (GPC) were used to analyse the structural changes in the resin. GPC results showed that after processing at 290 °C using the torque rheometer, large size soluble polymeric components increased. The increase in the large size soluble polymeric components after processing at 290 °C was probably related to the crosslinking reactions in the grafted polybutadiene (PB). Furthermore, chemical analysis of the ABS resin samples after multiple extrusion cycles in a twin-screw extruder indicated that reprocessing considerably affected the ABS resin.

An overview on the influence of process parameters through the characteristic of 3D-printed PEEK and PEI parts

Fused Filament Fabrication (FFF) technology is increasingly applied in automotive, aerospace and medical applications. FFF is one of the most widely used additive manufacturing techniques to manufacture thermoplastics or their composites. FFF enables improvement in both cycle time and total cost of product development. Such improvements are achieved through the quick manufacture of functional prototypes enable real-world product development and testing. While the benefits of FFF are undeniable, its use in demanding applications is hindered by materials properties. The used commodity and standard polymers actually exhibit low to medium thermal and mechanical properties. To overcome this limitation, the aerospace industry looks for high-performance thermoplastics to obtain plastic parts strong enough to be used as a replacement for metal. Recent developments in FFF equipment now enable engineering polymers, such as Polyether ether ketone (PEEK) and Polyether imide (PEI), to be utilized for parts with increased mechanical and thermal properties. Thus, this article reviews and discusses the properties and the printing parameters of PEEK and PEI produced by FFF.