A strategy of precipitated calcium carbonate (CaCO3) fillers for enhancing the mechanical properties of polypropylene polymers

Biomimetic Use of Food-Waste Sources of Calcium Carbonate and Phosphate for Sustainable Materials-A Review

Natural and renewable sources of calcium carbonate (CaCO3), also referred to as "biogenic" sources, are being increasingly investigated, as they are generated from a number of waste sources, in particular those from the food industry. The first and obvious application of biogenic calcium carbonate is in the production of cement, where CaCO3 represents the raw material for clinker. Overtime, other more added-value applications have been developed in the filling and modification of the properties of polymer composites, or in the development of biomaterials, where it is possible to transform calcium carbonate into calcium phosphate for the substitution of natural hydroxyapatite. In the majority of cases, the biological structure that is used for obtaining calcium carbonate is reduced to a powder, in which instance the granulometry distribution and the shape of the fragments represent a factor capable of influencing the effect of addition. As a result of this consideration, a number of studies also reflect on the specific characteristics of the different sources of the calcium carbonate obtained, while also referring to the species-dependent biological self-assembly process, which can be defined as a more "biomimetic" approach. In particular, a number of case studies are investigated in more depth, more specifically those involving snail shells, clam shells, mussel shells, oyster shells, eggshells, and cuttlefish bones.

From Waste to Value Added Products: Manufacturing High Electromagnetic Interference Shielding Composite from End-of-Life Vehicle (ELV) Waste

The use of plastics in automobiles is increasing dramatically due to their advantages of low weight and cost-effectiveness. Various products can be manufactured by recycling end-of-life vehicle (ELV) plastic waste, enhancing sustainability within this sector. This study presents the development of an electromagnetic interference (EMI) shield that can be used for protecting electronic devices in vehicles by recycling waste bumpers of ethylene propylene diene monomer (EPDM) rubber from ELVs. EPDM waste was added to a unique combination of 40/60: PP/CaCO3 master batch and conductive nanofiller of carbon nanotubes using an internal melt mixing process. This nanocomposite was highly conductive, with an electrical conductivity of 5.2×10-1S·cm-1 for 5 vol% CNT in a 30 wt% EPDM/70 wt% PP/CaCO3 master batch and showed a high EMI shielding effectiveness of 30.4 dB. An ultra-low percolation threshold was achieved for the nanocomposite at 0.25 vol% CNT. Waste material in the composite improved the yield strain by about 46% and strain at break by 54% in comparison with the same composition without waste. Low cost and light-weight fabricated composite from ELV waste shows high EMI SE for application in electronic vehicles and opens a new path to convert waste to wealth.

Balancing the Strength-Impact Relationship and Other Key Properties in Polypropylene Copolymer-Natural CaSO4 (Anhydrite)-Filled Composites

To develop novel mineral-filled composites and assess their enhanced properties (stiffness, a good balance between mechanical strength and impact resistance, greater temperature stability), a high-impact polypropylene copolymer (PPc) matrix containing an elastomeric discrete phase was melt mixed with natural CaSO4 β-anhydrite II (AII) produced from gypsum rocks. First, in a prior investigation, the PPc composites filled with AII (without any modification) displayed enhanced stiffness, which is correlated with the relative content of the filler. The tensile and impact strengths dramatically decreased, especially at high filling (40 wt.%). Therefore, two key methods were considered to tune up their properties: (a) the ionomeric modification of PPc composites by reactive extrusion (REx) with zinc diacrylate (ZA), and (b) the melt mixing of PPc with AII surface modified with ethylenebis(stearamide) (EBS), which is a multifunctional processing/dispersant additive. The properties of composites produced with twin-screw extruders (TSEs) were deeply assessed in terms of morphology, mechanical, and thermal performance, including characterizations under dynamic mechanical solicitations at low and high temperatures. Two categories of products with distinct properties are obtained. The ionomeric modification by Rex (evaluated by FTIR) led to composites characterized by remarkable thermal stability, a higher temperature of crystallization, stronger interfacial interactions, and therefore noticeable mechanical properties (high tensile strength (i.e., 28 MPa), increased stiffness, moderate (3.3 kJ/m2) to good (5.0 kJ/m2) impact resistance) as well as advanced heat deflection temperature (HDT). On the other hand, the surface modification of AII with EBS facilitated the dispersion and debonding of microparticles, leading to composites revealing improved ductility (strain at break from 50% to 260%) and enhanced impact properties (4.3-5.3 kJ/m2), even at high filling. Characterized by notable mechanical and thermal performances, high whiteness, and a good processing ability, these new PPc-AII composites may be tailored to meet the requirements of end-use applications, ranging from packaging to automotive components.

Engineering Polypropylene-Calcium Sulfate (Anhydrite II) Composites: The Key Role of Zinc Ionomers via Reactive Extrusion

Polypropylene (PP) is one of the most versatile polymers widely used in packaging, textiles, automotive, and electrical applications. Melt blending of PP with micro- and/or nano-fillers is a common approach for obtaining specific end-use characteristics and major enhancements of properties. The study aims to develop high-performance composites by filling PP with CaSO₄ β-anhydrite II (AII) issued from natural gypsum. The effects of the addition of up to 40 wt.% AII into PP matrix have been deeply evaluated in terms of morphology, mechanical and thermal properties. The PP-AII composites (without any modifier) as produced with internal mixers showed enhanced thermal stability and stiffness. At high filler loadings (40% AII), there was a significant decrease in tensile strength and impact resistance; therefore, custom formulations with special reactive modifiers/compatibilizers (PP functionalized/grafted with maleic anhydride (PP-g-MA) and zinc diacrylate (ZnDA)) were developed. The study revealed that the addition of only 2% ZnDA (able to induce ionomeric character) leads to PP-AII composites characterized by improved kinetics of crystallization, remarkable thermal stability, and enhanced mechanical properties, i.e., high tensile strength, rigidity, and even rise in impact resistance. The formation of Zn ionomers and dynamic ionic crosslinks, finer dispersion of AII microparticles, and better compatibility within the polyolefinic matrix allow us to explain the recorded increase in properties. Interestingly, the PP-AII composites also exhibited significant improvements in the elastic behavior under dynamic mechanical stress and of the heat deflection temperature (HDT), thus paving the way for engineering applications. Larger experimental trials have been conducted to produce the most promising composite materials by reactive extrusion (REx) on twin-screw extruders, while evaluating their performances through various methods of analysis and processing.

Gradient Micropillar Array Inspired by Tree Frog for Robust Adhesion on Dry and Wet Surfaces

The strong adhesion on dry and wet surfaces and the durability of bioinspired hierarchical fibrillar adhesives are critical for their applications. However, the critical design for the strong adhesion normally depends on fine sub-micron structures which could be damaged during repeat usage. Here, we develop a tree frog-inspired gradient composite micropillars array (GP), which not only realizes a 2.3-times dry adhesion and a 5.6-times wet adhesion as compared to the pure polydimethylsiloxane (PDMS) micropillars array (PP), but also shows excellent durability over 200 repeating cycles of attachment/detachment and self-cleaning ability. A GP consists of stiffer tips and softer roots by incorporating gradient dispersed CaCO₃ nanoparticles in PDMS micropillar stalks. The modulus gradient along the micropillar height facilitates the contact formation and enhances the maximum stress during the detaching. The study here provides a new design strategy for robust adhesives for practical applications in the fields of robotics, electronics, medical engineering, etc.

Liberation of plastic nanoparticles and organic compounds from three common plastics in water during weathering under UV radiation-free conditions

A 620-day batch experiment was conducted to examine the generation of nano-sized plastic particles and migration of organic compounds derived from plastic additives and impurities during the weathering of three common plastic types in water with and without reactive oxygen species. The results show that the amount of nanoplastics plus organic compounds liberated from the tested plastic films, as indicated by total organic carbon, was in the following decreasing order: PET >PP > ABS. Hydroxyl radical generated from Fenton-like reaction significantly enhanced the generation of nanoplastics and release of organic compounds from the weathered plastic films via oxidative degradation. Over 30 organic compounds including potentially toxic organic pollutants originated from plastic additives and impurities were detected. There was a marked difference in the plastic nanoparticle size distribution between the deionized water and the water containing reactive oxygen species. The strong oxidizing capacity of hydroxyl radical resulted in rapider disintegration of the coarser nanoparticles (>500 nm) into the finer nanoparticles (<500 nm) and allowed complete decomposition of the nanoplastics with a size <50 nm or even <100 nm. Elevated level of Ca was detected on the surfaces of the ABS and PP nanoparticles. PP- and PET-derived nanoplastics contained heavy metal(loid)s while no heavy metal(loid)s was detected for the ABS nanoparticles. PET nanoparticles had a stronger capacity to bind S- and N-containing organic ligands compared to the other two plastic nanoparticles. The nanoplastics generated from the weathering were irregular in shape, which means that they had larger specific area compared to spherical engineered nanoplastics.

E-waste dismantling as a source of personal exposure and environmental release of fine and ultrafine particles

Electronic waste (WEEE; from TV screens to electric toothbrushes) is one of the fastest growing waste streams in the world. Prior to recycling, e-waste components (metals, wood, glass, etc.) are processed by shredding, grinding and chainsaw cutting. These activities generate fine and ultrafine particle emissions, containing metals as well as organics (e.g., flame retardants), which have high potential for human health impacts as well as for environmental release. In this work, release of fine and ultrafine particles, and their exposure impacts, was assessed in an e-waste recycling facility under real-world operating conditions. Parameters monitored were black carbon, particle mass concentrations, ultrafine particles, and aerosol morphology and chemical composition. Potential health impacts were assessed in terms of cytotoxicity (cell viability) and oxidative stress (ROS) on <2 μm particles collected in liquid suspension. Environmental release of WEEE aerosols was evidenced by the higher particle concentrations monitored outside the facility when compared to the urban background (43 vs.11 μgPM2.5/m³, respectively, or 2.4 vs. 0.2 μgCa/m³). Inside the facility, concentrations were higher in the top than on the ground floor (PM2.5 = 147 vs. 78 μg/m³, N = 15.4 ∗ 104 vs. 8.7 ∗ 104/cm³, BC = 12.4 vs. 7.2 μg/m³). Ventilation was a key driver of human exposure, in combination with particle emissions. Key chemical tracers were Ca (from plastic fillers) and Fe (from wiring and other metal components). Y, Zr, Cd, Pb, P and Bi were markers of cathode TV recycling, and Li and Cr of grinding activities. While aerosols did not evidence cytotoxic effects, ROS generation was detected in 4 out of the 12 samples collected, associated to the ultrafine fraction. We conclude on the need for studies on aerosol emissions from WEEE facilities, especially in Europe, due to their demonstrable environmental and human health impacts and the rapidly growing generation of this type of waste.

Generation of micro(nano)plastics and migration of plastic additives from Poly(vinyl chloride) in water under radiation-free ambient conditions

A batch experiment was conducted to observe the liberation of micro- and nano-sized plastic particles and plastic additive-originated organic compounds from poly(vinyl chloride) under radiation-free ambient conditions. The weathering of PVC films in deionized water resulted in isolated pockets of surface erosion. Additional ^●OH from Fenton reaction enhanced PVC degradation and caused cavity erosion. The detachment of plastic fragments from the PVC film surfaces was driven by autocatalyzed oxidative degradation. Over 90% of micro-sized plastic particles were <60 μm in length. The detached plastic fragments underwent intensified weathering, which involved strong dehydrochlorination and oxidative degradation. Further fragmentation of micro-sized particles into nano-sized particles was driven by oxidative degradation with complete dehydrochlorination being achieved following formation of nanoplastics. 20 organic compounds released from the PVC films into the solutions were identified. And some of them can be clearly linked to common plastic additives. In the presence of additional ^●OH, the coarser nanoplastic particles (>500 nm) tended to be rapidly disintegrated into finer plastic particles (<500 nm), while the finest fraction of nanoplastics (<100 nm) could be completely decomposed and disappeared from the filtrates. The micro(nano)plastics generated from the PVC weathering were highly irregular in shape.

Ocean Deacidification Technologies for Marine Aquaculture

The increase in partial pressure of CO2 in the oceans directly affects the productivity and survival of coastal industries and ecosystems. For marine aquaculture, the decreased alkalinity of seawater results in reduced availability of carbonates for marine organisms to build their shells, leading to decreased aquaculture quality and productivity. The industry has been implementing recirculating aquaculture systems (RASs) to reduce CO2 in feedwaters, but recent interest in ocean-based CO2 capture has led to additional strategies that may be relevant. The new methods in addition to CO2 removal offer capture options for enhanced aquaculture sustainability. Here, we review and compare early-stage and commercially available technologies for deacidification of seawater and their suitability for aquaculture. Most methods considered rely on a voltage-induced pH swing to shift the carbonate/bicarbonate equilibrium toward the release of CO2, with subsequent capture of the released CO2 as a gas or as solid mineral carbonates. The modular design and distributed deployment potential of these systems offers promise, but current demonstrations are limited to bench scale, highlighting the need for sustained research and development before they can be implemented for marine aquaculture.

Comparative Reinforcement Effect of Achatina fulica Snail Shell Nanoparticles, Montmorillonite, and Kaolinite Nanoclay on the Mechanical and Physical Properties of Greenpoxy Biocomposite

This study investigated the comparative reinforcement effect of Achatina fulica snail shell nanoparticles, montmorillonite, and kaolinite nanoclay on greenpoxy. Greenpoxy nanocomposites of snail shell nanoparticles, montmorillonite, and kaolinite nanoclay were developed separately, with the nanofiller content ranging from 1 to 3% by weight. Specimens of the nanocomposites with different percentage weights of the nanoparticles were prepared using the resin casting method. Mechanical properties, such as the tensile strength, stiffness, hardness, and impact strength, and water absorption properties of the specimens were evaluated experimentally. It was observed that the incorporation of nanoparticles improved the mechanical properties of pure greenpoxy irrespective of the percentage weight, source, and type of reinforcement. Significantly, the loading of 1 wt.% of snail shell nanoparticles offered superior properties in most cases. Protein fibers and high-concentration calcium carbonate in snail shell nanoparticles, uniform dispersion, and excellent matrix/snail shell nanoparticle adhesion provided a strong structure, resulting in the high strength, stiffness, and decreased water uptake of the composites. The superior properties observed in snail shell nanoparticle composites suggest that this naturally sourced nanofiller can be used as a potential substitute for montmorillonite and kaolinite clays.

Synchronously Strengthen and Toughen Polypropylene Using Tartaric Acid-Modified Nano-CaCO3

In order to overcome the challenge of synchronously strengthening and toughening polypropylene (PP) with a low-cost and environmental technology, CaCO₃ (CC) nanoparticles are modified by tartaric acid (TA), a kind of food-grade complexing agent, and used as nanofillers for the first time. The evaluation of mechanical performance showed that, with 20 wt.% TA-modified CC (TAMCC), the impact toughness and tensile strength of TAMCC/PP were 120% and 14% more than those of neat PP, respectively. Even with 50 wt.% TAMCC, the impact toughness and tensile strength of TAMCC/PP were still superior to those of neat PP, which is attributable to the improved compatibility and dispersion of TAMCC in a PP matrix, and the better fluidity of TAMCC/PP nanocomposite. The strengthening and toughening mechanism of TAMCC for PP involves interfacial debonding between nanofillers and PP, and the decreased crystallinity of PP, but without the formation of β-PP. This article presents a new applicable method to modify CC inorganic fillers with a green modifier and promote their dispersion in PP. The obtained PP nanocomposite simultaneously achieved enhanced mechanical strength and impact toughness even with high content of nanofillers, highlighting bright perspective in high-performance, economical, and eco-friendly polymer-inorganic nanocomposites.

Calcium Carbonate as Functional Filler in Polyamide 12-Manipulation of the Thermal and Mechanical Properties

Adjusting the thermal response properties of a polymeric compound can significantly improve the usability in a selective laser-sintering process. As previously shown, combining a precise amount of coarse and narrow size distribution fine calcium carbonate fillers results in a potential optimization of the thermal properties of a polyamide 12 matrix. Additionally, up to 60% of the normally associated lost ductility can be re-gained by surface modification, thus functionalizing the filler. To optimize the functionality further this study combines a precisely defined particle size ratio of fillers adopting a specially selected surface modification using amino hexanoic acid. Morphology of the carbonate filler was also investigated. The range of effect of each parameter on the thermal response and mechanical properties was studied. The results show that the thermal properties have large potential to be optimized, without reducing the ductility significantly, by adjusting the morphology and size ratio of coarse and fine filler particles. The compound properties were demonstrated using a twin-screw extruder, indicating the potential for producing a preparate composite for additive manufacturing.

The Influence of Nano CaCO3 on Nucleation and Interface of PP Nano Composite: Matrix Processability and Impact Resistance

Polypropylene (PP) is a commodity material that has been increasingly used in different industries in the past two decades due to its versatile properties when enhanced with additives. Homo polypropylene, in general, has weak mechanical properties and limited chemical resistance; thus, using a different type of fillers to adjust such properties to fit the required applications opened a large market for this commodity. Understanding the interface constituent between the polymer matrix and the added filler and the nucleation behavior is a key to fine control of the enhancement of PP properties. In this study, PP was incorporated with nano calcium carbonate (CaCO₃) at 2 and 5 wt% in the presence of maleic anhydride (MAH) to overcome the weak interface due to low polymer polarity. The mix was compounded in a twin screws extruder at a temperature range of 180–200 °C ; then, the prepared samples were left to dry for 24 h at 25 °C. Nuclear Magnetic Resonance (NMR) was used to study the interface adhesion of the nanofiller and the curved revealed that at 2% of nano CaCO₃ PP structure remained the same and the nano experienced good adhesion to the polymer matrix. The mechanical impact resistance results showed a real enhancement to the polymer matrix of the nanocomposite by 37%. Moreover, DSC results showed a faster crystallinity rate due to the nanofiller acting as a nucleating agent and rheology tests indicated that low content of nano additive (2%) has better processability behavior, with suitable viscosity complex values at high frequencies.

Nanocomposite Polymer Electrolytes of Sodium Alginate and Montmorillonite Clay

Nanocomposite polymer electrolytes (NPEs) were synthesized using sodium alginate (Alg) and either sodium (SCa-3-Na⁺)- or lithium (SCa-3-Li⁺)-modified montmorillonite clays. The samples were characterized by structural, optical, and electrical properties. SCa-3-Na⁺ and SCa-3-Li⁺ clays’ X-ray structural analyses revealed peaks at 2θ = 7.2° and 6.7° that corresponded to the interlamellar distances of 12.3 and 12.8 Å, respectively. Alg-based NPEs X-ray diffractograms showed exfoliated structures for samples with low clay percentages. The increase of clay content promoted the formation of intercalated structures. Electrochemical Impedance Spectroscopy revealed that Alg-based NPEs with 5 wt% of SCa-3-Na⁺ clay presented the highest conductivity of 1.96 × 10⁻² S/cm², and Alg with 10 wt% of SCa-3-Li⁺ showed conductivity of 1.30 × 10⁻² S/cm², both measured at 70 °C. From UV-Vis spectroscopy, it was possible to infer that increasing concentration of clay promoted a decrease of the samples’ transmittance and, consequently, an increase of their reflectance.

A fungal mycelium templates the growth of aragonite needles

Fungi live within diverse environments and survive well under extreme conditions that are usually beyond the tolerance of most other organisms. In different environments fungi are known to induce precipitation of a wide range of minerals. Various species of fungi have been shown to facilitate calcium carbonate mineralization. Here, inspired by examples of needle-fiber calcite formed via fungus-induced biomineralization typically observed in soils and sediments, we utilized inactivated fungus to synthetically induce precipitation of CaCO3 needles. To our knowledge, the feasibility of growing aragonitic needles within fungal mycelium in vitro has not been previously demonstrated. The needles we obtained were curved, displayed hexagonal facets, and demonstrated high-aspect ratios close to 60. The size and shape of these synthetic needles matched those of the mycelium of the natural fungus. Utilizing high-resolution characterization techniques, we studied the morphology and the micro- and nanostructures of the aragonitic needles. Our findings showed that even inactivated fungal mycelium, if present in the crystallization environment, can serve as a template for the formation of high-aspect ratio fibers and can stabilize metastable polymorphs.

Formation and Emissions of Volatile Organic Compounds from Homo-PP and Co-PP Resins during Manufacturing Process and Accelerated Photoaging Degradation

Volatile organic compounds (VOCs) from polypropylene (PP) seriously restricts the application of PP in an automotive field. Herein, the traceability of VOCs from PP resins during manufacturing process and accelerated photoaging degradation was clarified on basis of an accurate characterization method of key VOCs. The influence of PP structures on changing the accelerated photoaging degradation on the VOCs was systematic. The VOCs were identified by means of Gas chromatography (GC) coupled with both a hydrogen flame ion detector (FID) and a mass spectrometry detector (MSD). Results showed that both the molecular structure of PP and the manufacturing process affected the species and contents of VOCs. In addition, the photoaging degradation of PP resulted in a large number of new emerged volatile carbonyl compounds. Our work proposed a possible VOC formation mechanism during the manufacturing and photoaging process. VOCs from PP resins were originated from oligomers and chain random scission during thermomechanical degradation. However, β scission of alkoxy radical and Norrish tape I reactions of ketones via intermediate transition were probably the main VOCs formation routes towards PP during photoaging degradation. This work could provide scientific knowledge on both the accurate traceability of VOCs emissions and new technology for development of low-VOCs PP composites for vehicle.

The study of fly ash filler behaviour in the polymer matrix of polyethyleneterephthalate

The purpose of the investigation was to study the behavior of mechanically activated fly ash filler containing carbon in a polymer matrix of polyethylene terephthalate (PET). By means of the methods of optical and electron microscopy the change of physical and chemical properties of fly ash after intensive grinding in planetary mills of centrifugal type was considered. The research showed that mechanically activated filler, in contrast to its non-activated analog, structures the polymer matrix and provides improving the characteristics of the composite material.

Are functional fillers improving environmental behavior of plastics? A review on LCA studies

The use of functional fillers can be advantageous in terms of cost reduction and improved properties in plastics. There are many types of fillers used in industry, organic and inorganic, with a wide application area. As a response to the growing concerns about environmental damage that plastics cause, recently fillers have started to be considered as a way to reduce it by decreasing the need for petrochemical resources. Life cycle assessment (LCA) is identified as a proper tool to evaluate potential environmental impacts of products or systems. Therefore, in this study, the literature regarding LCA of plastics with functional fillers was reviewed in order to see if the use of fillers in plastics could be environmentally helpful. It was interesting to find out that environmental impacts of functional fillers in plastics had not been studied too often, especially in the case of inorganic fillers. Therefore, a gap in the literature was identified for the future works. Results of the study showed that, although there were not many and some differences exist among the LCA studies, the use of fillers in plastics industry may help to reduce environmental emissions. In addition, how LCA methodology was applied to these materials was also investigated.