Macromolecular Symposia最新文献

This study presents a short overview of the main 3D polymer composite items that are fabricated by extrusion and stereolithography printing. By coupling polymers traditionally used in additive manufacturing, such as PEGDA, and polymers of biomedical interest, such as PVA, with carbon nanostructures, such as nanodiamond and graphene nanoplates, and conductive polymers, such as PEDOT and PANI, it has been possible to produce objects with specific functional properties exploited for fabricating scaffolds for cell growth and proliferation as well as soft electrodes for developing organic compounds sensing devices and electrocardiogram monitoring systems under real-time conditions.

A numerical procedure to simulate the curing process of polymer-based composites is proposed. This model is applied to a carbon-epoxy composite at a micromechanical level to predict residual stress at the end of the process and the evolution of the most important process parameters. A finite element model is written in the Ansys APDL environment and comprises two moduli that must be solved consecutively: the thermal–kinetical and structural modules. At each timestep, first thermal/kinetics problem is solved, then the temperature and degree of conversion profile results are used to calculate the viscoelastic properties, allowing the calculation of residual stress.

Fiber reinforced polymers boast exceptional mechanical performance coupled with low material density. Over recent decades, their usage has been steadily increasing and is poised to accelerate in the future. These materials typically have a lifespan of around 25–30 years, so at present time lots of tons of polymer composites are next to their end of life and this volume continues to grow. Currently, a significant portion of these materials is either incinerated or landfilled, resulting in substantial environmental impacts. Numerous studies have aimed to identify optimal recycling approaches, one of which involves solvolysis: the chemical dissolution of the polymer matrix. In this study, a solvolysis method has been devised and refined to effectively recover carbon fibers from composites while minimizing property degradation. The process begins with the identification of a suitable solvolysis fluid, specifically an aqueous sulfuric acid solution. Subsequently, key solvolysis parameters including solution concentration, temperature, residence time, and fluid agitation are meticulously optimized. The chemical and morphological impacts of this process are thoroughly examined using Fourier-transform infrared spectroscopy analysis and scanning electron microscope observations.

Essential oil loaded edible films are good alternatives of petroleum-based polymer packaging materials for extending the shelf-life of perishable fruits. This work studies the influence of grapeseed oil concentration on the physical and antioxidant properties of chitosan-based edible films. The multicomponent films are softer and more stretchable than the pure chitosan films. An increase in the oil concentration increases the antioxidant activity and the hydrophobicity of the films, which is expressed in a decrease in the affinity for water uptake and a change in their surface energy. The surface color and the transparency of the films are optimal at low oil concentration. The evaluated physical and physicochemical properties show the potential of these films to reduce the food waste.

The work describes the preparation of bio-based precursor carbon fibers (CFs) by a solvent-free process. Fibers from lignin, cellulose acetate, and triacetin as plasticizer are successfully obtained by melt-spinning showing a potential alternative to traditional precursor fibers from petroleum produced by wet-spinning. Thermal, morphological, and structural properties of precursor fibers are studied. In particular, precursor fibers present glass transition temperatures lower than neat polymers, indicating the feasibility of using melt-spinning due to an enhanced softening. Two stabilization thermal treatments with fast or slow heating are adopted to prepare the precursor fibers for carbonization. The CF yield achieves 32% for the materials at high lignin content.

This work investigates the effects of spermidine (SPD) on the properties of hemp-based biopolymers developed in the absence or presence of glycerol (GLY). The mechanical properties of the biopolymer show that the tensile strength and Young's module significantly increase when the film is prepared with SPD alone (10 mm). However, the GLY plasticized films with the same concentration of 10 mm SPD have the highest elongation at break compared to the other films. The film moisture content, water solubility, and swelling ratio improve by the incorporation of SPD, resulting in the development of more hydrophobic biopolymers. However, the hydrophobicity and barrier properties to gases and water vapor of the biopolymers are higher when prepared with SPD alone.

Magnesium doped hydroxyapatite nanoparticles in dextran matrix (7MgHApDx) with average size diameter of 18.2 ± 0.5 nm are synthesized by co-precipitation. The surface morphology and shape of 7MgHApDx particles are established by scanning electron microscopy (SEM). The stability that is evaluated by ultrasound measurements and zeta potential reveals a good stability. More than that, the functional groups present in the studied samples are identified by Fourier transform infrared spectroscopy studies. The antimicrobial properties of 7MgHApDx suspensions are determined against Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, and Candida albicans ATCC 10231 microbial strains.

A type of foamed plastic insulation that improves thermal performance while maintaining the original durability by adding fillers with low radiation rates in foamed plastic insulation is investigated. The thermal conductivity of extruded polystyrene foam (XPS) adding graphite is reduced by 14% compared to without graphite additives. The study investigates that mechanism by comparing the properties of XPS and XPS containing graphite (graph XPS) through the gas isotherm method and 3D imaging analysis by X-ray CT. First, the specific surface area of the insulation's resin is examined through the gas isotherm method using N2, H₂O, and CO₂. The results confirmed that graph XPS has a more increased specific surface area than XPS. Second, the internal structure of the insulation and its strut/pore distribution is confirmed through X-ray CT, which showed an increase in surface area with a thinning of the strut. The improved thermal performance due to the addition of graphite may contribute to an increase in the surface area of the insulation.

The paper consists of a preliminary design and analysis of a lightweight composite backing structure for a side deployable solid mesh reflector intended for telecom application in the Ka-Band. As the entire antenna reflector must withstand the forces related to the launching loads, the focus is addressed to the stiffness of the composite backing structure, so that the reflective metallic mesh will not be affected during launching phase, thus with no influence over the possible deformation of the mesh and on its radio frequency performance. It is shown that the proposed concept withstands the imposed launching requirements with a compromise on mass properties.

In order to face the environmental concern about the use of traditional fossil-based monomers for the production of thermosetting resins, herein this study reports the synthesis of bio-based materials from waste cooking oil (WCO). In this context, this study explores the epoxidation-acrylation strategy for the synthesis of the starting functionalized oil for the production of thermosetting resins composed of only WCO-derived monomers or in combination with terpenic comonomers such as limonene and myrcene. Furthermore, employing myrcene as comonomer produces thermosetting resins that reveal the best properties in terms of mechanical strength if compared to the homopolymer ones.