Strong Polyamide-6 Nanocomposites with Cellulose Nanofibers Mediated by Green Solvent Mixtures

Thermally Conductive and Electrically Insulating Polymer-Based Composites Heat Sinks Fabricated by Fusion Deposition Modeling

This study explores the potential of novel boron nitride (BN) microplatelet composites with combined thermal conduction and electrical insulation properties. These composites are manufactured through Fusion Deposition Modeling (FDM), and their application for thermal management in electronic devices is demonstrated. The primary focus of this work is, therefore, the investigation of the thermoplastic composite properties to show the 3D printing of lightweight polymeric heat sinks with remarkable thermal performance. By comparing various microfillers, including BN and MgO particles, their effects on material properties and alignment within the polymer matrix during filament fabrication and FDM processing are analyzed. The characterization includes the evaluation of morphology, thermal conductivity, and mechanical and electrical properties. Particularly, a composite with 32 wt% of BN microplatelets shows an in-plane thermal conductivity of 1.97 W m-1 K-1, offering electrical insulation and excellent printability. To assess practical applications, lightweight pin fin heat sinks using these composites are designed and 3D printed. Their thermal performance is evaluated via thermography under different heating conditions. The findings are very promising for an efficient and cost-effective fabrication of thermal devices, which can be obtained through extrusion-based Additive Manufacturing (AM), such as FDM, and exploited as enhanced thermal management solutions in electronic devices.

Improvement in the Thermomechanical Properties and Adhesion of Wood Fibers to the Polyamide 6 Matrix by Sequential Ball Milling Technique

The engineering thermoplastics industry has largely limited the use of natural fiber reinforcements due to their susceptibility to low-onset thermal degradation and water absorption. Therefore, in order to utilize these economically viable and environmentally friendly materials effectively through common composite fabrication methods such as hot pressing, safeguarding them from thermal degradation becomes essential. This work presents a viable industrially technique called sequential ball milling for processing unbleached softwood kraft pulp fibers (PF) with an engineering thermoplastics polyamide 6 (PA6) with high melting temperatures (>220 °C). An additional eco-friendly modification step that employs ball milling and cellulose nanocrystal (CNC) has been implemented in this study to enhance the mechanical properties of the composites. Special attention is given to fine-tuning key variables, such as milling duration and PF particle size, to produce optimal composites. Leveraging the ability of sequential ball milling to evenly distribute pulp fibers into PA6, a 160% increase in Young's modulus was achieved with the incorporation of 30 wt % PF. Importantly, the introduction of a 5 wt % CNC modifying agent elevated Young's modulus to 4.3 GPa, marking a 187% improvement over unmodified PA6. Diverse techniques, including rheological analyses, thermomechanical evaluations, morphological examinations, and assessments of moisture absorption, were utilized to validate the efficiency of the suggested processing approach and the modification phase.

Direct milling: Efficient, facile, and green method for processing fibrillated cellulose/polymeric nanocomposites with boosted thermomechanical and rheological performance

Bringing biobased nanomaterials into polymer manufacturing is essential to enhance polymers' properties and address the challenges posed by plastic waste. Using polymers such as polyamide 6 (PA6) in advanced industries, e.g., automotive sector, has been impeded as a direct consequence of their inability to meet the required mechanical properties. Herein, we utilize bio-based cellulose nanofibers (CNFs) to enhance the properties of PA6 by green processing, with no footprint on the environment. We address the issue of the dispersion of the nanofillers in polymeric matrices and demonstrate direct milling (cryo-milling and planetary ball milling) to facilitate a thorough integration of the components. Nanocomposites incorporating 1.0 wt% CNF, processed by pre-milling followed by compression molding, are shown to possess a storage modulus of 3.8 ± 0.2 GPa, Young's modulus of 2.9 ± 0.2 GPa, and ultimate tensile strength of 63 ± 3 MPa (all measured at room temperature). To show the superiority of direct milling in achieving these properties, other frequent approaches used to disperse CNF in polymers, such as solvent casting and hand mixing, are meticulously investigated and compared for the performance of their resulting specimens. The ball-milling method is demonstrated to provide PA6-CNF nanocomposites with excellent performance, better than solvent casting, with no associated environmental concerns.

Preparation and Characterization of Non-Crimping Laminated Textile Composites Reinforced with Electrospun Nanofibers

This research investigated the use of electrospun nanofibers as reinforcing laminates in textiles to enhance their mechanical properties for use as smart and technical textile applications. Crimping plays a crucial role in textiles. Because of crimp, fabrics have extensibility, compressibility, and improved quality. Although crimping is inevitable for fabrics used in smart textiles, it is also a disadvantage as it could weaken the fibers and reduce their strength and efficiency. The study focused on preparing laminated textile composites by electrospinning a polyacrylonitrile (PAN) polymer onto textile fabric. The research examined the effect of electrospun nanofibers on the fabric by using a tensile testing machine and scanning electron microscopy. The results revealed that the prepared laminated textile was crimp-free because of the orientation of the nanofibers directly electrospun on the fabric, which exhibited perfect bonding between the laminates. Additionally, the nanofiber-reinforced composite fabrics demonstrated a 75.5% increase in the elastic moduli and a 20% increase in elongation at breaking. The study concluded that the use of electrospun nanofibers as laminates in textile composites could enhance the elastic properties, and prepared laminated composites will have the advantages of nanofibers, such as crimp-free elastic regions. Furthermore, the mechanical properties of the laminated textile composite were compared with those of the micromechanical models, providing a deeper understanding of the behavior of these laminated composites.

Synthesis, Properties and Applications of Polymeric Nanomaterials

The term "polymeric nanomaterials" is commonly used for all polymer-based nanomaterials, but it is mainly applied to nanospheres and nanocapsules [...].