Many studies have explored using natural fibers from biomass as reinforcement in thermoplastics. However, a key challenge in developing these composites is achieving effective interfacial adherence between the hydrophilic natural fibers and hydrophobic polymer matrix. Additionally, excessive or insufficient amounts of fiber and compatibilizer can lead to composite failure due to poor dispersion, inadequate interfacial bonding, or fiber agglomeration. In this work, banana fibers at 10, 20, and 30 wt

Graphene (GP) belongs to a class of structured carbon compounds with outstanding properties that address its application in energy storage devices, water filtration, biomedical fields, and so on. To take advantage of its high thermal conductivity, this work was thought to study the effect of GP on the rotational molding and properties of linear low-density polyethylene (LLDPE). First, the better molding conditions were determined by different internal peak air temperatures. Once chosen, LLDPE was enriched with a masterbatch containing GP at different contents. Significant energy savings in the rotational process were achieved by addition of GP to LLDPE. Through the drop dart impact test, the presence of GP improved the impact strength. This finding was endorsed by the calorimetric measurement, which revealed a decrease in the LLDPE degree of crystallinity. The melt flow rate showed a slight variation with the GP content. The presence of the GP did not change the rheologic behavior of the composites. Even in very low content, WAXD and Raman spectroscopy revealed the presence of GP in the composites. Thermal conductivity of the composites increased when GP was added to LLDPE which could explain the energy savings in the composites' processing and their impact property. As a consequence, the increment of thermal conduction affected the cooling rate of LLDPE chains, leading to some extent to the amorphization of the polymer matrix.

This work explores the use of low-value packaging film-based waste mixed plastics (wMP) and carbon nanotubes (CNT) to produce value-added composites. The performance of the composites is assessed through mechanical testing, UV ageing, and electrical conductivity measurement. Reinforcing wMP with 5 wt% CNT increased the tensile strength and tensile modulus by 46 % and 23 %, respectively. There were similar increases in flexural modulus (53 %), compressive strength (131 %), and compressive modulus (89 %) compared to unreinforced wMP. UV ageing for 500 h had no measurable effect on unreinforced wMP but decreased the flexural modulus of wMP/5 wt% CNT by 23 %. An average electrical conductivity of 1.65 x 10-2 S/m was measured for wMP/CNT, with unreinforced wMP showing no measurable electrical conductivity, as expected. This research provides valuable scientific insights into the application of mixed waste plastics in composites, aiding the creation of a more circular economy for plastic waste and leading to second-generation products with a wide range of potential applications.

This study verified the possibility of recycling polyethylene-based composites with up to 40% of lignocellulosic reinforcement after 5 cycles of compression molding, milling and extrusion. Two forms of filler from the same plant species, Arundo donax L., were studied, namely, fibers and shredded aerial parts of the plant. The properties of composites were assessed at each processing step, finding that the reprocessing affects to more extend the particulate filler than the fibrous one; the lower particle size resulted in lowered tensile properties. However, despite the fiber size reduction, as aspect ratio is not drastically diminished, the better dispersion of the fibers in the matrix counteracts the negative effects of their shorter size. Impact properties are improved with the recycling, possibly due to the increased homogeneity of the samples, which is also translated into a higher density (and lower porosity). The thermomechanical stability of the fiber composites is higher than for the shredded ones. The reduction in size of the fillers is reflected in the lowered viscosity obtained after the reprocessing. The fibers continue stiffening the matrix after the 5 reprocessing cycles, where the milled material acts more as a filler, reducing tensile properties, although showing a good flexural behavior.

This work explores the use of low-value film-based waste mixed plastics (wMP) from packaging and waste glass fibres (wGF) to produce value-added composites. The study involves producing thermoplastic prepregs with wMP and wGF, manufacturing laminates via compression moulding, optimising wGF content, analysing the interface and assessing the performance of the laminates through mechanical testing. The results indicate that adding 12-26 vol% wGF to unreinforced wMP leads to significant improvements in tensile strength (over 300%), tensile modulus (-570%), flexural modulus (-7 80%), compressive strength (-350%), and compressive modulus (over800%) compared to unreinforced wMP. The significance of having 2-D dispersion of short fibres with partial orientation compared to the more conventionally used 3-D dispersion of short fibres is discussed. The research provides valuable scientific insights into the application of mixed waste materials in composites, aiding the creation of a more circular economy for plastic waste and leading to new composite products.

Giant reed (Arundo donax L.) is a plant species with a high growth rate and low requirements, which makes it particularly interesting for the production of different bioproducts, including natural fibers. This work assesses the use of fibers obtained from reed culms as reinforcement for a high-density polyethylene (HDPE) matrix. Two different lignocellulosic materials were used: i) shredded culms and ii) fibers obtained by culms processing, which have not been reported yet in literature as fillers for thermoplastic materials. A good stress transfer for the fibrous composites was observed, with significant increases in mechanical properties; composites with 20% fiber provided a tensile elastic modulus of almost 1900 MPa (78% increase versus neat HDPE) and a flexural one of 1500 MPa (100% increase), with an improvement of 15% in impact strength. On the other hand, composites with 20% shredded biomass increased by 50% the tensile elastic modulus (reaching 1560 MPa) and the flexural one (up to 1500 MPa), without significant changes in impact strength. The type of filler is more than its ratio; composites containing fibers resulted in a higher performance than the ones with shredded materials due to the higher aspect ratio of fibers.

Solidification models are key during simulation of several industrial processes involving thermoplastics. For simplicity, crystallinity is often not considered within these models, despite it being responsible for the phase transition. Several advanced methods, which consider crystallinity as the onset of solidification have been proposed in literature however, these have primarily been applied to classical homopolymers such as polypropylene (PP). The focus of this study is to develop a model that can capture the rheological response observed during the transition from liquid‐like to solid‐like behavior in injection molding grade polyetheretherketone (PEEK) due to crystallinity. Isothermal rheological experiments are performed alongside dynamic scanning calorimetry (DSC) characterization to correlate relative crystallinity to the apparent increase in viscosity. The model is extended to nonisothermal processes through the incorporation of the Nakamura model. Nonisothermal crystallization rheology experiments are performed and compared with a simulation of the oscillating rheometer process for validation. The modeled viscosity response and crystallization half‐time reproduced the experimental data with sufficient accuracy at low cooling rates, with an error of less than 5% up to cooling rates of 20°C min−1. This shows that the method is an accurate means of obtaining the rheological response during crystallization in a numerical simulation.

Rotational molding advantages include the production of a hollow part with no welding lines, either of small or big sizes, with no internal stresses and good surface details. However, the process is limited by the long cycle times, and its related high energy consumption. Different strategies can be followed to reduce such energy use. This work assesses the use of pressure inside the molds during the densification and cooling stages, finding reductions in overall cycle time of approximately 20%, because of the reduction in the heating time required but also to the increased cooling rate. The influence of such an approach on the production of composites with reed fibers has also been assessed, finding a similar trend towards cycle time reductions. The rotomolded samples’ thermomechanical and rheological behavior were determined, finding that viscosity was not affected due to the incorporation of air during the moldings; besides, the homogeneity of the composites increased due to the mold pressurization. The parts obtained show good aesthetics and good thermomechanical behavior along the entire temperature range studied, and particularly for 10% composites; higher fiber ratios should be prepared via melt compounding. Therefore, the mold pressurization allows us to reduce both oven and cooling times, which can be translated into an increase in productivity and a decrease in energy consumption, which are undeniably related to the increase in the products’ sustainability and cost.

This work aims at demonstrating the potential benefits of using a mineral waste from quarries as a filler of polypropylene (PP) products obtained by rotational molding. A polypropylene matrix was dry blended with the ignimbrite dust (mainly composed of silica and alumina) in ratios up to 30% weight, obtaining well consolidated parts in all cases. However, it can be observed that, as expected, the parts with higher loadings result in a higher number of defects due to the air release hindering. The viscosity of the obtained blends was determined by oscillatory rheometry, finding that the incorporation of up to 30% of the mineral dust is not significantly affecting the viscous behavior of the material. Furthermore, the low particle size of the filler allows for a good distribution inside the PP matrix, obtaining a homogeneous material with good dispersion. The increased amount of ignimbrite results in improved storage modulus, meaning that the filler, even in dust format, is able to stiffen the matrix at high loadings (over 20%). However, increased ratios of filler also result in a lower adhesion between the filler and the matrix and reduced homogeneity of the blend.

Nitric oxide (NO) may be a simple compound but it plays a vital role as a signalling molecule in many different pathological and physiological pathways in our bodies. Among its many attributes, it is a potent antimicrobial agent with activity against biofilms. It also triggers vasodilation and prevents thrombus formation. Clinicians are keen to exploit NO, as exogenous delivery has the potential to offer many varied advanced therapies mimicking natural processes. Its gaseous nature however, makes it difficult to handle, and the biological response to NO is concentration and location dependant. In addition, NO has a very short half-life. To be effective, therefore, NO must be delivered directly to the target cells at the correct concentration for the desired effect. We have previously demonstrated that metal organic framework (MOF) materials offer the ability to adsorb, store and release NO from framework metal sites by a moisture exchange mechanism. Furthermore, on formulating these MOF powders into polymer matrices via solvent casting techniques, we have shown that we can load these MOF/polymer composites with NO and control the delivery of NO from the film surface. In our most recent work, we have advanced to using extrusion methods to produce MOF containing polymer tubing, using medical grade polymers that are currently utilised in catheter manufacture. The challenges associated with designing new materials for medical device applications is a balance between controlled, consistent delivery (dosage), toxicology and suitable form of the material. In this poster, we show how the physical characteristics of the tube, the NO release profile and biocompatibility vary with MOF loading levels. Using in vitro assays, we demonstrate that release of NO from the extruded composites can deliver anti-microbial activity, prevent blood platelet aggregation and induce vascular relaxation. Our results prove that we can prevent three pressing clinical challenges related to catheterisation – infection, thrombosis and vascular/arterial spasm.

The incorporation of materials different from the polymer within the rotational molding process usually results in lowered mechanical properties, where impact strength is of particular concern. In order to overcome this issue, multilayer structures of virgin polyethylene (PE) and banana fiber composites were prepared to determine the impact of the different layers on the performance of the final part. Cycle time has been studied to identify the influence of the addition of fibers in the process. The tensile, flexural and impact properties have been analyzed, finding improvements in Young’s modulus of up to 13%, although at the expense of significant decreases in impact strength. A reduction in the fiber size due to the pulverization process was observed, which affected the rheological and mechanical behavior of the composite. The beneficial effects of working in multiple layers have been demonstrated in this work, where composites with up to 5% of banana fiber have been produced in two-layer structures. Finally, the need to add neat polyethylene in the external layer is also highlighted as a way to counteract the reductions in mechanical properties, particularly for flexural elastic modulus and tensile strength, and this also helps with the drop in impact behavior to a lower extent.

In this work, we designed and fabricated a multifunctional nanocomposite system that consists of chitosan, raspberry-like silver nanoparticles, and graphene oxide. The room temperature atmospheric pressure microplasma (RT-APM) process provides a rapid, facile, and environmentally-friendly method for introducing silver nanoparticles into the composite system. Our composite can achieve a pH controlled single and/or dual drug release. Under pH 7.4 for methyl blue loaded on chitosan, the drug release profile features a burst release during the first 10 h, followed by a more stabilized release of 70–80% after 40–50 h. For fluorescein sodium loaded on graphene oxide, the drug release only reached 45% towards the end of 240 h. When the composite acted as a dual drug release system, the interaction of fluorescein sodium and methyl blue slowed down the methyl blue release rate. Under pH 4, both single and dual drug systems showed a much higher release rate. In addition, our composite system demonstrated strong antibacterial abilities against E. coli and S. aureus, as well as an excellent photothermal conversion effect under irradiation of near infrared lasers. The photothermal conversion efficiency can be controlled by the laser power. These unique functionalities of our nanocomposite point to its potential application in multiple areas, such as multimodal therapeutics in healthcare, water treatment, and anti-microbials, among others.

Abstract Aiming to further plastics recycling via rotational moulding plastics processing, blends of virgin and recycled polyethylene sourced from post-consumer plastics were developed. Three different kinds of recycled high density polyethylene – from bottles, pipes and mixed household waste – were compounded with virgin medium density polyethylene in an extruder. The ideal amount of recyclate was chosen based upon the impact resistance of different contents (25, 50 and 75%) of recycled plastic with the 50/50 blend found to have the best performance. Compression-moulded and rotationally-moulded samples were analysed through falling dart impact test, flexural test, melt flow rate and differential scanning calorimetry analysis. The impact results of the compression-moulded samples showed an increase in the impact resistance of the blends with a higher melt flow index and lower degree of crystallinity. The rotationally-moulded specimens displayed much lower impact resistance than the pure virgin plastic and a 20–30% reduction in the flexural moduli, which were ascribed to the crystalline structure of the part and issues in the blends’ rotomoulding process. It was concluded that blending virgin and recycled polyethylene for rotational moulding can be an effective way to further plastics recycling inside the Circular Economy context.

Achieving ultra-high thermal conductivity while maintaining the electrical insulation of polymers is highly desirable for many applications such as thermal management and packaging. In this work, polyethylene/boron nitride nanoplatelets (PE/BNNP) nanocomposite film was produced through melt processing followed by uniaxial stretching. Microstructural analysis reveals that the stretched composite film features a co-continuous network structure which consists of oriented lamellae bridged by both stretched polymer chains and aligned BNNPs along the stretching direction. The resulting film exhibit a metal-like thermal conductivity as high as 106 W m(-1) K-1 and it is believed that the unique network structure has enabled efficient phonon transfer across the film, resulting in superior thermal transporting performance. This work shines a light on the design and scalable manufacturing of high performance functional polymer-based composites for future thermal management applications.

Vaginal rings (VRs) are currently marketed for contraceptive or hormone regulation purposes, and in-vestigationally, have been widely reported for delivery of antiretrovirals to reduce HIV transmission. To date, there is no national or international standard for the mechanical testing and minimum performance characteristics of any VR based products. Here, we describe a series of mechanical tests examining the durometer hardness, static and dynamic compression response, tensile properties and twist resistance of vaginal rings. The tests were conducted on currently marketed VRs and a number of the International Partnership for Microbicides' (IPM) investigational VR formulations. With wider application in the field, the tests described herein could form the basis for a more standardised approach to the mechanical testing of VRs.

Composites of recycled carbon fiber (CF) with up to 30 wt % loading with polyethylene (PE) were prepared via melt compounding. The morphology of the composites and the degree of dispersion of the CF in the PE matrix was examined using scanning electron microscopy, and revealed the CF to be highly dispersed at all loadings and strong interfacial adhesion to exist between the CF and PE. Raman and FTIR spectroscopy were used to characterize the surface chemistry and potential bonding sites of recycled CF. Both the Young's modulus and ultimate tensile stress increased with increasing CF loading, but the percentage stress at break was unchanged up to 5 wt % loading, then decreased with further successive addition of CF. The effect of CF on the elastic modulus of PE was examined using the Halpin-Tsai and modified Cox models, the former giving a better fit with the values determined experimentally. The electrical conductivity of the PE matrix was enhanced by about 11 orders of magnitude on addition of recycled CF with a percolation threshold of 7 and 15 wt % for 500-mu m and 3-mm thick samples. (c) 2007 Wiley Periodicals, Inc.