Two series of polymer blends based on post-consumer polypropylene (rPP) and tire rubber crumbs (Trc) under the trademark ECOPLASTOMER® PP70 with a mutual ratio of components 70/30 wt%, containing 10, 20, and 30 wt% of flame retardants, have been prepared using a twin-screw extruder. The influence of commercially available silane-treated alumina trihydrate (ATH-sil) with the eco-friendly system based on melamine phosphate (MP), aluminum hydroxide (AC), and peanut shells (PS), used as flame retardant agents, on the mechanical, thermal, and flammability properties of polymer blends was assessed – the incorporation of ATH-sil results in the appearance of peaks related to OH groups in the Fouriertransform infrared spectroscopy (FTIR) spectra. Similar observations are made for the MP/AC/PS system. differential scanning calorimetry (DSC) analysis revealed that using the selected flame retardants did not impact the melting and crystallization temperatures of the polymer. Tensile strength experienced a minor decrease, particularly in compositions containing more than 20 wt% of the flame retardants, while hardness remained unaffected by their share. Both flame retardants reduced the flammability of the modified polypropylene/rubber powder blends, and the most favorable outcomes were achieved with ATH-sil; however, only when employed at a minimum of 30 wt%. The formulated MP/AC/PS system proved more adept at reducing flammability and smoke emissions at lower flame retardant levels (up to 20 wt%).

editorial

Polyimide (PI) fiber is a promising and high-performance polymer fiber with high temperature resistance and low density; however, much energy is needed during the thermal imidization process.Here, PI fiber with excellent mechanical properties and high-temperature resistance was fabricated via the dry-jet wet spinning method for polyamic acid (PAA) precursor fiber, followed by stretching and thermal imidization reaction at a lower temperature.With the increase of the stretching ratio, the mechanical properties of the PI fiber increase significantly.When the stretching was twice as long, the tensile strength and initial modulus of the fiber were as high as 6.23 and 114.13 cNdtex -1 , respectively.Fourier transform infrared results revealed that all samples were completely imidized at 260 C.The resulting PI fibers exhibit only 5% weight loss at 539.53 C, and its limiting oxygen index (LOI) can reach up to 32.6%, showing excellent high temperature resistance and flame-retardant properties as well as commendable mechanical performance, which compare favorably with those of other imidization methods.

Dynamic cross-linked networks (DCNs) endow thermoset rubber with self-healability and recyclability to extend its lifetime and alleviate environmental pollution.However, the contradiction between high self-healing and mechanical properties in DCNs rubber is always difficult to be resolved.Herein, we used boronic ester (BO) and Diels-Alder dynamic covalent bonds (DA) to synthesize polybutadiene-based dual networks rubber (PB-BO-DA) via thiol-ene reaction.This approach achieved a tensile strength of 16.46 MPa and 99% self-healing efficiency, facilitated by extensive intermolecular interactions (- packing and N-B coordination) and fully dynamic cross-linking.In addition, multiple dynamic cross-linked networks (MDCNs) polybutadiene-based rubber also show excellent shape memory ability and recyclability.This strategy might open a helpful pathway to fabricate intelligent multifunctional polymers with high strength and high self-healing efficiency.

This study investigated the properties of the natural rubber (NR) foam filled with azodicarbonamide (ADC) blowing agents by combination to various ratios of epoxidized NR (ENR) for flexible foam applications.Compound operation was prepared with an open two-roll mill and the production was fabricated by compression molding.The study elucidated properties related to crosslinking behaviors, mechanical and dynamic properties, elasticity, abrasion, weathering resistance, and sound absorption efficiency.The ENR and ADC concentrations affected the tensile testing and also the durability properties of the NR/ENR.The NR and ENR foam of 60/40 filled with 10 phr of ADC demonstrated good properties across various parameters, showing acceptable tensile properties, abrasion resistance, and QVA light resistance.Additionally, the presence of a closed-cell structure in the blends reduced crack propagation in the NR matrix during aging, improving weathering resistance.The absorption coefficient increased with higher ADC content, being optimal at 15 phr, due to the lower density and higher porosity of the opened-cell material, which enhances its ability to interact more effectively with incoming energy at 1600 and 6400 Hz.The findings encourage the use of ENR for blending in NR for improved ENR and ADC concentrations since dipole-dipole interaction from ENR-ADC caused ADC dispersability, providing complexed foam structures for force expansion and aslo sound wave absorption.

The study investigates the use of repurposed milled carbon fibre (mCF) as reinforcement for polyamide 66 (PA66) in gear applications, addressing environmental and cost concerns of virgin carbon fibres. Neat PA66 and PA66 composites reinforced with mCF, glass fibres (GF), and carbon fibres (CF), with and without polytetrafluoroethylene (PTFE), were injection moulded and evaluated for microstructure (fibre length), thermal, mechanical, surface, and tribological properties, as well as gear performance under VDI 2736 guidelines. CF reinforced composites showed the highest modulus and tensile strength, followed by mCF and GF. PTFE reduced modulus and strength in binary composites. All reinforced composites significantly lowered the coefficient of friction (COF) and wear rate compared to neat PA66, with mCF showing the most notable improvements. PTFE slightly improved tribological performance only for GF (wear) and CF (COF) composites. In gear testing, binary composites outperformed neat PA66, with CF performing best, followed by mCF and GF. Ternary composites had slightly lower performance than their binary equivalents. Correlation analysis showed that gear performance is closely linked to structural integrity. Failure analysis revealed higher crack susceptibility in mCF reinforced gears due to shorter fibre length. The findings highlight mCF reinforced PA66 as a sustainable, cost-effective material for durable polymer gears.

Polyhydroxybutyrate (PHB) is a polymer with great application potential; however, its brittleness and low mechanical strength restrict its use in many fields.This study investigated a strategy to overcome the mechanical limitations of PHB by blending it with polycaprolactone (PCL) and producing nanocomposites with non-functionalized carbon nanotubes (CNT) and functionalized ones (f-CNT).The effect of blend composition and the addition of f-CNT were studied in hotpressed specimens.In PHB/30PCL blends, a reduction in the overall crystallinity degree was observed, while in PHB/10PCL the crystallinity maintained close to neat PHB.In PHB/10PCL nanocomposites, no significant change was registered, but in PHB/30PCL with f-CNT, the crystallinity degree increased and achieved values comparable to PHB.Differential scanning calorimetry suggested that f-CNT had a higher impact in PCL crystallinity in formulations of PHB/30PCL.Scanning electron microscopy showed that in these formulations, f-CNT were preferably located at the interface of PHB/PCL, while in PHB/10PCL the particles were mainly located in PHB.In general, the blends suffered with a reduction in elastic modulus and strength, especially for PHB/30PCL formulation.

Thermoplastic natural rubber (TPNR) is widely used across industries due to its unique blend of elasticity and processability. Thermoplastic vulcanizates (TPVs) based on thermoplastic polyurethane (TPU) offer excellent mechanical properties and flexibility, yet often require enhanced elasticity and durability. Blending TPU with natural rubber (NR) is promising; however, phase incompatibility reduces mechanical strength and thermal stability. To address this, epoxidized NR (ENR) was employed as a compatibilizer in TPU/NR blends. ENR’s hydrocarbon backbone interacts with crosslinked NR, while epoxy groups enhance adhesion with TPU. Incorporating 3 phr of ENR significantly improved crosslinking, increased tensile strength by 41.1%, enhanced stress relaxation, and lowered the glass transition temperatures of both TPU and NR phases in the TPU/NR blends. These effects are attributed to improved chemical bridging between TPU and NR. However, excess ENR disrupts phase compatibility, causing polymer entanglement and reduced strength. Optimizing ENR content is essential for developing high-performance TPU/NR blends. Printability was demonstrated using the material extrusion additive manufacturing (MEx-AM) fused deposition modeling (FDM), showing potential for flexible applications like splints and medical devices.

editorial

Curcumin (CRC) is a natural active principle with important anti-inflammatory, antioxidant, antibacterial, and antitumor properties but has some limitations, such as poor bioavailability, low water solubility, and rapid metabolism. To preserve CRC’s benefits and eliminate its limitations, novel CRC-loaded core-shell electrospun nanofibers were designed. The nanofibers were prepared by co-axial electrospinning method using poly(vinyl alcohol)/CRC as core and poly(vinyl alcohol)/sodium alginate as shell. Polymer coating protects the CRC, increasing its stability. The swelling degree of CRCloaded nanofibers at pH 5.4 was around 326% higher than at pH 7.4 (297%) due to the repulsions of the anion-anion COO–groups. The release efficiency of CRC at pH 7.4 was 81%, while at pH 5.4 was about 96%. In the first 6 h, there was a slower release of CRC from the nanofibers in both acidic and slightly alkaline environments. Nanofibers showed good hemocompatibility, the values being between 2.36–3.22% after the first 90 min of contact, and after 180 min of treatment, the degree of erythrocyte lysis was between 3.78 and 4.93%. Cell viability assay on V79-4 Chinese hamster fibroblasts demonstrated that treatment with free CRC led to a value of 39% whereas for CRC-loaded nanofibers, the cell viability value increased to 59.66%. The results of the present study indicated that CRC-loaded electrospun nanofibers can have great potential for biomedical applications.