Hybrid biocomposites from polypropylene, sustainable biocarbon and graphene nanoplatelets

Investigation of Far Infrared Emission and UV Protection Properties of Polypropylene Composites Embedded with Candlenut-Derived Biochar for Health Textiles

Far infrared radiation (FIR) within the wavelength range of 4-14 μm can offer human health benefits, such as improving blood flow. Therefore, additives that emit far infrared radiation have the potential to be incorporated into polymer/fabric matrices to develop textiles that could promote health. In this study, biochar derived from candlenuts and pyrolyzed with activated carbon (AC) was incorporated into polypropylene (PP) films and investigated for its potential as a health-promoting textile additive. The properties of biochar were compared with other far infrared (FIR) emitting additives such as hematite, Indian red ochre, and graphene. The addition of biochar increased FIR emissivity to 0.90, which is 9% higher than that of pristine PP. Additionally, biochar enhanced UV and near-infrared (NIR) blocking capabilities, achieving an ultra-protection factor (UPF) of 91.41 and NIR shielding of 95.85%. Incorporating 2 wt% biochar resulted in a 3.3-fold higher temperature increase compared to pristine PP after 30 s of exposure to an FIR source, demonstrating improved heat retention. Furthermore, the ability to achieve the lowest thermal effusivity among other additives supports the potential use of biochar-incorporated fabric as a warming material in cold climates. The tensile properties of PP films with biochar were superior to those with other additives, potentially contributing to a longer product lifespan. Additionally, samples with red ochre exhibited the highest FIR emissivity, while samples with hematite showed the highest capacity for UV shielding.

Thermomechanical Properties of Virgin and Recycled Polypropylene-High-Density Polyethylene Blends

This paper provides evidence and discusses the variability in the thermomechanical behaviour of virgin and recycled polypropylene/high-density polyethylene blends without the addition of other components, which is sparse in the literature. Understanding the performance variability in recycled polymer blends is of critical importance in order to facilitate the re-entering of recycled materials to the consumer market and, thus, contribute towards a circular economy. This is an area that requires further research due to the inhomogeneity of recycled materials. Therefore, the thermal and mechanical properties of virgin and recycled polypropylene/high-density polyethylene blends were investigated systematically. Differential scanning calorimetry concludes that both the recycled and virgin blends are immiscible. Generally, recycled blends have lower overall crystallinity and melting temperatures compared with virgin blends while, remarkably, their crystallisation temperatures are compared favourably. Dynamical mechanical analysis showed little variation in the storage modulus of recycled and virgin blends. However, the alpha and beta relaxation temperatures are lower in recycled blends due to structural deterioration. Deterioration in the thermal and mechanical properties of recycled blends is thought to be caused by the presence of contaminants and structural degradation during reprocessing, resulting in shorter polymeric chains and the formation of imperfect crystallites. The tensile properties of recycled blends are also affected by the recycling process. The Young's modulus and yield strength of the recycled blends are inferior to those of virgin blends due to the deterioration during the recycling process. However, the elongation at break of the recycled blends is higher compared with the virgin blends, possibly due to the plasticity effect of the low-molecular-weight chain fragments.

PVC containing silver nanoparticles with antimicrobial properties effective against SARS-CoV-2

Poly (vinyl chloride) (PVC) is commonly used to manufacture biomedical devices and hospital components, but it does not present antimicrobial activity enough to prevent biofouling. With the emergence of new microorganisms and viruses, such as Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) that was responsible for the global pandemic caused by Coronavirus Disease 2019 (COVID-19), it is evident the importance of the development of self-disinfectant PVC for hospital environments and medical clinics where infected people remain for a long time. In this contribution, PVC nanocomposites with silver nanoparticles (AgNPs) were prepared in the molten state. AgNPs are well-known as antimicrobial agents suitable for designing antimicrobial polymer nanocomposites. Adding 0.1 to 0.5 wt% AgNPs significantly reduced Young's modulus and ultimate tensile strength of PVC due to the emergence of microstructural defects in the PVC/AgNP nanocomposites, but the impact strength did not change significantly. Furthermore, nanocomposites have a higher yellowness index (YI) and lower optical bandgap values than PVC. The PVC/AgNP nanocomposites present virucidal activity against SARS-CoV-2 (B.1.1.28 strain) within 48 h when the AgNP content is at least 0.3 wt%, suitable for manufacturing furniture and hospital equipment with self-disinfectant capacity to avoid secondary routes of COVID-19 contagion.

Response of Polypropylene Composites Reinforced with Natural Fibers: Impact Strength and Water-Uptake Behaviors

Composites from polypropylene (PP) reinforced with hemp strands (HS) are prepared in the current work with the aim of deepening on the influence of this reinforcement on the impact performance of these specific composites. Despite all the research conducted in this field, the effect of this natural reinforcement on the absorbed energy during crack formation and propagation is not fully tackled in previous research works. From the methodology and samples' geometry, the results concluded that the quality of the interface has a noticeable role in the impact resistance of these materials. The interface strength, fiber dispersion and fiber pullout are the main contributors to crack formation, whereas fiber pullout is the main one responsible for crack propagation. Maximum values of absorbed energy were found for PP composites comprising 20-30 wt% of HS and 8 wt% of the coupling agent for the un-notched samples, whereas maximum absorbed energy values corresponded to PP composites with 40 wt% of HS and 4 wt% of coupling agent for the notched samples. The water-absorption behavior in different humid environments is also examined. From the kinetic study, the water diffusion followed a Fickean behavior showing low-diffusion coefficients, increasing with fiber content. This systematic investigation represents a contribution to the analysis of the potential of reinforcing conventional polymers with natural materials, as a strategy towards more sustainable development.

Bio-Polypropylene and Polypropylene-based Biocomposites: Solutions for a Sustainable Future

Polypropylene (PP) is among the most widely used commodity plastics in our everyday life due to its low cost, lightweight, easy processability, and exceptional chemical, thermo-mechanical characteristics. The growing awareness on energy and environmental crisis has driven global efforts for creating a circular economy via developing sustainable and eco-friendly alternatives to traditional plastics produced from fossil fuels for a variety of end-use applications. This review paper presents a brief outline of the emerging bio-based PP derived from renewable natural resources, covering its production routes, market analysis and potential utilizations. This contribution also provides a comprehensive review of the PP-based biocomposites produced with diverse green fillers generated from agro-industrial wastes, with particular emphasis on the structural modification, processing techniques, mechanical properties, and practical applications. Furthermore, given that the majority of PP products are currently destined for landfills, research progress on enhancing the degradation of PP and its biocomposites is also presented in light of the environmental concerns. Finally, a brief conclusion with discussions on challenges and future perspectives are provided.

The effect of surface nucleation modulation on the mechanical and biocompatibility of metal-polymer biomaterials

The deployment of hernia repair patches in laparoscopic procedures is gradually increasing. In this technology, however, understanding the new phases of titanium from the parent phase on polymer substrates is essential to control the microstructural transition and material properties. It remains a challenging area of condensed matter physics to predict the kinetic and thermodynamic properties of metals on polymer substrates from the molecular scale due to the lack of understanding of the properties of the metal-polymer interface. However, this paper revealed the mechanism of nucleation on polymer substrates and proposed for the first record a time-dependent regulatory mechanism for the polymer-titanium interface. The interconnection between polymer surface chain entanglement, nucleation and growth patterns, crystal structure and surface roughness were effectively unified. The secondary regulation of mechanical properties was accomplished simultaneously to satisfy the requirement of biocompatibility. Titaniumized polypropylene patches prepared by time-dependent magnetron sputtering technology demonstrated excellent interfacial mechanical properties and biocompatibility. In addition, modulation by low-temperature plasma metal deposition opened a new pathway for biomaterials. This paper provides a solid theoretical basis for the research of titanium nanofilms on medical polypropylene substrates and the medical industry of implantable biomaterials, which will be of great value in the future.

Development of a New Type of Flame Retarded Biocomposite Reinforced with a Biocarbon/Basalt Fiber System: A Comparative Study between Poly(lactic Acid) and Polypropylene

A new type of partially biobased reinforcing filler system was developed in order to be used as a flame retardant for polylactic acid (PLA) and polypropylene (PP)-based composites. The prepared materials intended for injection technique processing were melt blended using the novel system containing ammonium polyphosphate (EX), biocarbon (BC), and basalt fibers (BF). All of the prepared samples were subjected to a detailed analysis. The main criterion was the flammability of composites. For PLA-based composites, the flammability was significantly reduced, up to V-0 class. The properties of PLA/EX/BC and PLA/EX/(BC-BF) composites were characterized by their improved mechanical properties. The conducted analysis indicates that the key factor supporting the effectiveness of EX flame retardants is the addition of BC, while the use of BF alone increases the flammability of the samples to the reference level. The results indicate that the developed materials can be easily applied in industrial practice as effective and sustainable flame retardants.

New Poplar-Derived Biocomposites via Single-Step Thermoforming Assisted by Phosphoric Acid Pretreatment

One-step thermoforming represents an effective approach to preparing glue-free biocomposites. This study aimed to produce glue-free biocomposites with high-temperature resistance and mechanical properties using phosphoric acid pretreatments combined with thermoforming. Due to the hot-moulding process, the cell wall was destroyed, which allowed the fibres to adhere closely together. Most hemicelluloses were hydrolysed through pretreatment with phosphoric acid, and the contact area between the cellulose and lignin was significantly increased. The biocomposites prepared by ball milling demonstrated remarkable flexural strength (49.03 MPa) and tensile strength (148.23 MPa). Moreover, they had excellent thermal stability, with the maximum temperature for pyrolysis rate at 374 °C, which was much higher than that of poplar (337 °C). In addition, the material released no formaldehyde during the preparation process, which is in line with the concept of green production.

Pyrolysis of low-value waste switchgrass: Physicochemical characterization, kinetic investigation, and online characterization of hot pyrolysis vapours

The present study is dedicated to physicochemical characterization, kinetic, thermal degradation behaviors, and online characterization of vapour products through Py-GC-MS and TGA-FTIR. The feasibility study was attained via proximate, ultimate, fibre analysis, and extractive analysis, whereas Vyazovkin (VM), Ozawa-Flynn-Wall (OFW), Kissinger-Akahira-Sunose (KAS), Coats-Redfern (CR), and Distributed Activation Energy Model (DAEM) were employed for kinetics exploration. The feasibility study showed its tremendous ability to be used as pyrolysis feedstock. TGA-FTIR documented the maximum release of CO₂ (26.22%), carbonyls (25.04%), and hydrocarbons (15.93%). Further, kinetic investigation of SWG documented an increased trend of activation energy against progressive conversion. The apparent average activation energy from KAS, OFW, DAEM, and VM was found to be 126.03, 137.54, 130.33, 134.26 kJ mol^-1, respectively. Also, kinetics reaction mechanisms are exposed to the multi-nature of decomposition of biomass. Furthermore, the Py-GC-MS investigation established increased hydrocarbons (6.49-11.54%) and reduced oxygen-containing products (24.17-17.27%) with an increased temperature.

Value-Added Bio-carbon Production through the Slow Pyrolysis of Waste Bio-oil: Fundamental Studies on Their Structure-Property-Processing Co-relation

The present work addresses the transformation of bio-oil into valuable biocarbon through slow pyrolysis. The biocarbons produced at three different temperatures (400, 600, and 900 °C), 10 °C min^-1 heating rate, and 30 min holding time were tested for their surface morphology, thermal stability, elemental composition, functionality, particle size, and thermal and electrical conductivity. The physicochemical study of bio-oil showed substantial carbon content, higher heating value, and lower nitrogen content. Also, the Thermogravimetric analyzer-FourierTransform Infrared Spectroscopy (TGA-FTIR) study of bio-oil confirmed that the majority of gases released were hydrocarbons, carbonyl products, ethers, CO, and CO_2, with a minor percentage of water and alcohol. Overall, it was found that the pyrolysis temperature has the dominant role in the yield and properties of biocarbon. The physicochemical characterization of biocarbon showed that the higher temperature based pyrolyzed biocarbon (600 and 900 °C) improved the properties in terms of thermal stability, thermal conductivity, graphitic content, ash content, and carbon content. Furthermore, the elemental and Energy-Dispersive Spectroscopy study of biocarbon confirmed the substantial depletion in oxygen and hydrogen at a higher temperature (600 and 900 °C) than the lower temperature based pyrolyzed biocarbon (400 °C). Additionally, the purest form of the biocarbon is found at a higher temperature (900 °C) with higher thermal stability and carbon content. The study of the surface morphology of biocarbon revealed that the higher temperature (600 and 900 °C) biocarbon showed larger and harder particles than the lower temperature biocarbon (400 °C); however, the electrical conductivity of biocarbon decreased, whereas thermal conductivity increased, with an increase in the pyrolysis temperatures. Moreover, the particle size analysis of biocarbon confirmed that most of the particles were found in the range of 1 μm. The increased thermal stability, carbon content, and graphitic content and the lower ash content endorse biocarbon as an excellent feedstock for carbon-based energy storage materials.

Extrusion Based 3D Printing of Sustainable Biocomposites from Biocarbon and Poly(trimethylene terephthalate)

Three-dimensional (3D) printing manufactures intricate computer aided designs without time and resource spent for mold creation. The rapid growth of this industry has led to its extensive use in the automotive, biomedical, and electrical industries. In this work, biobased poly(trimethylene terephthalate) (PTT) blends were combined with pyrolyzed biomass to create sustainable and novel printing materials. The Miscanthus biocarbon (BC), generated from pyrolysis at 650 °C, was combined with an optimized PTT blend at 5 and 10 wt % to generate filaments for extrusion 3D printing. Samples were printed and analyzed according to their thermal, mechanical, and morphological properties. Although there were no significant differences seen in the mechanical properties between the two BC composites, the optimal quantity of BC was 5 wt % based upon dimensional stability, ease of printing, and surface finish. These printable materials show great promise for implementation into customizable, non-structural components in the electrical and automotive industries.

Sustainable Biocomposites from Recycled Bale Wrap Plastic and Agave Fiber: Processing and Property Evaluation

Plastic recycling to make sustainable materials is considered one of the biggest initiatives toward a greener environment and socioeconomic development. This research aims to investigate the properties of a blend of recycled bale wrap linear low-density polyethylene (rLLDPE) and polypropylene (PP) (rLLDPE/PP 50:50 wt % matrix), which was further reinforced with 25 wt % agave fiber prepared by injection-molding. Different ratios of a combined industrial compatibilizer (maleic anhydride-grafted PP/PE) were used (1-3 wt %), which were compared with a synthesized compatibilizer made from maleic anhydride-PP/rLLDPE in terms of mechanical and thermomechanical properties of the biocomposites. Incorporation of the compatibilizer in the composite improved the interfacial adhesion between the hydrophobic matrix and the hydrophilic agave fiber, which further increased the mechanical properties and heat deflection temperature of the composite. Scanning electron microscopy showed enhanced compatibility and adhesion between the fiber and the matrix by inclusion of 2 wt % compatibilizer. The synthesized compatibilizer-blended composite showed better mechanical properties than the industrial one, which indicates the potential application of this composite (around 62% recycled material) in the manufacture of packaging materials and commodity products.

Thermoformed Containers Based on Starch and Starch/Coffee Waste Biochar Composites

Biodegradable containers support zero-waste initiatives when alternative end-of-life scenarios are available (e.g., composting, bio digestion). Thermoplastic starch (TPS) has emerged as a readily biodegradable and inexpensive biomaterial that can replace traditional plastics in applications such as food service ware and packaging. This study has two aims. First, demonstrate the thermoformability of starch/polycaprolactone (PCL) as a thermoplastic material with varying starch loadings. Second, incorporate biochar as a sustainable filler that can potentially lower the cost and enhance compostability. Biochar is a stable form of carbon produced by thermochemical conversion of organic biomass, such as food waste, and its incorporation into consumer products could promote a circular economy. Thermoformed samples were successfully made with starch contents from 40 to 60 wt.% without biochar. Increasing the amount of starch increased the viscosity of the material, which in turn affected the compression molding (sheet manufacturing) and thermoforming conditions. PCL content reduced the extent of biodegradation in soil burial experiments and increased the strength and elongation at break of the material. A blend of 50:50 starch:PCL was selected for incorporating biochar. Thermoformed containers were manufactured with 10, 20, and 30 wt.% biochar derived from waste coffee grounds. The addition of biochar decreased the elongation at break but did not significantly affect the modulus of elasticity or tensile strength. The results demonstrate the feasibility of using starch and biochar for the manufacturing of thermoformed containers.