Polypropylene Pellets Research Articles

VOC removal from automotive waste by supercritical CO2 extraction

This study investigated the reduction of volatile organic compounds (VOCs) from waste polypropylene (PP) from automobile bumpers by supercritical carbon dioxide (scCO2) extraction. The scCO2 extraction was performed with varying temperatures, pressures, and times in the range of 313–353 K, 10–25 MPa, and 1–6 h, respectively. At 333 K, 25 MPa, and 6 h, highly efficient removal of xylene, styrene, and total VOCs were observed, with removal percentages of >98 %. Optimal condition for VOC removal using scCO2 based on response surface methodology was determined to be 313 K, 10 MPa, and 2.17 h. No differences in size and color were observed in the scCO2-treated PP pellets. Moreover, VOC removal using scCO2 did not induce noticeable changes in the chemical and thermal properties of the treated PP samples. This result demonstrated that scCO2 extraction is a promising method for the VOC removal from automobile plastic waste.

Use of a nanoplastic carrier for assessing the aquatic toxicity of an organo-phosphite polymer additive

This work reports the production of nanoplastics (NPs) from polypropylene (PP) free of the antioxidant Irgafos® 168 (IRG) and alkane oligomers (ALK). PP pellets were milled into a powder with particle sizes in the 100–500 μm range. Additives and oligomers were removed using dichloromethane, and the powder exposed to UV irradiation, followed by filtration through 1 μm filters. PP suspensions, free of antioxidant and oligomers, were reloaded with IRG and ALK to their original commercial concentrations. This approach allowed testing the aquatic toxicity of IRG at concentrations compromised by water solubility limits. Toxicity assays using the cladoceran Daphnia magna with 24–48 h immobilization of neonates as endpoint showed toxicity for NPs containing IRG, with EC20 (48 h) in the 1.8–3.5 mg/L range, that corresponded to IRG exposure <1.2 μg/L. Suspensions of PP containing ALK, but not IRG, exhibited low toxicity (EC20 > 20 mg/L). The results allowed estimating the toxicity of IRG with a EC50 value of 3.3 ± 1.1 μg/L. Assays with different proportions of IRG and its oxidized form showed no differences. This work demonstrated the aquatic toxicity of IRG, for which there were no previous data, and developed a method for testing the toxicity of non-polar additives without being limited by their solubility.

Gamma‐ray‐induced modification of poly(ethylene terephthalate) and polypropylene solid materials with halogen‐containing olefins for X‐ray CT image contrast enhancement

AbstractIt is known that X‐ray CT of organic polymer materials usually provides low‐contrast images because of the low X‐ray absorption of these materials. In this paper, we describe a new method to enhance the contrast of X‐ray CT images of organic polymer materials. We demonstrate that gamma‐ray irradiation of poly (ethylene terephthalate) (PET) fibers in dichloromethane containing 2‐bromoethyl methacrylate, 2‐chloroethyl methacrylate, or 4‐bromostyrene results in the grafting of halogen‐containing oligomeric chains onto the PET fibers. Focused ion beam scanning electron microscopy (FIB‐SEM) and time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) analyses revealed a homogeneous distribution of bromine atoms within the 2‐bromoethyl methacrylate‐modified PET fibers, not only on the surface. This uniform incorporation translated to a significant improvement in X‐ray CT image contrast compared with pristine fibers. Similar treatment of polypropylene pellets also enhanced the contrast of their X‐ray CT images. This is a new simple and effective method to enhance the X‐ray CT image contrast and potentially applicable to various polymer materials including polymer composites and porous polymer materials, readily allowing the observation of their 3D microstructures finely.

Ultrasonic micro-injection moulding: characterisation of interfacial friction by varying feedstock shape and high-speed thermal imaging for microneedle feature replication

This study explores the interfacial friction in ultrasonic micro-injection moulding by using different polymer feedstock shapes, characterisation of micromoulding melts through thermal imaging and assessing microneedle feature replication. Industry standard polypropylene pellets and discs with different thicknesses were used for varying the amount of interfacial friction during sonication. High-speed thermal imaging and tooling containing sapphire windows were used to visualise the melt characteristics. Moulded products were characterised using laser-scanning confocal microscopy to quantify microneedle replication. The study demonstrates that (i) the interfacial area for the different feedstock shapes affects the heating in ultrasonic micro-injection moulding significantly, (ii) disc-shaped feedstocks result in initially higher flow front velocities and exhibit dominance of viscoelastic heating over interfacial friction and (iii) industrial pellet feedstocks provide a good combination interfacial friction and viscoelastic heating and more viscosity reduction in overall leading to better microreplication efficiency. The results presented could have a significant impact on the process development of ultrasonic micro-injection moulding where process repeatability can be improved by controlling the interfacial friction. The research provides an essential contribution to the development of this process, where interfacial frictional heating can be tailored specifically for miniature functional components, offering improved precision and reduced energy use when compared with conventional methods.

Multi-functionalization and recycling of basalt fibre/polypropylene laminated composites based on mixed plain-woven fabric and related interfacial decorations

The development of laminated composites of thermoplastic polypropylene (PP)/continuous basalt fabric is limited by poor mutual infiltration and weak interfacial interactions between the matrix and fabric, as well as the intrinsic flammability and susceptibility of the PP matrix to ultraviolet (UV) aging. To solve the above shortcomings in a high-efficiency manner, a multi-functional transition layer was constructed between the PP matrix and long basalt fibres (LBFs) based on a hybrid plain-woven fabric composed of LBFs weft yarns and PP warp yarns. After hot-laminating these hybrid plain-woven prepregs, the mechanical performance of the resultant laminates was optimised and strengthened by selecting the compositions of the multi-functional transition layers (comprising flexible alkyl glycidyl ether chains, various rigid inorganic nanoparticles, or a flexible-rigid hybrid layer). Among these different transition layers, the interface between the LBFs-g-MWCNTs-OH and the PP matrix presented better mutual infiltration due to the lower interfacial energy, stronger mechanical engagement effect derived from the rougher fibre surface, and higher interfacial modulus. Therefore, the fewer structural defects and more effective transfer of the applied load at the interface caused the tensile strength/modulus and flexural strength/modulus of the related hybrid weaving laminates (HWLs) to reach 278.1 MPa/31.8 GPa and 264.2 MPa/12.4 GPa, respectively. The rigid interfaces formed by the deposited nanoparticles also accelerated heat transfer from the matrix to the fibre and the absorption of UV-light inside composite, then improving the flame-retardancy and anti-UV aging performances of the corresponding HWLs. Finally, recyclability evaluations indicated that the waste LBFs-g-SiO2/PP HWLs can be used as anti-UV aging and flame-retardant agents to fabricate new modified PP pellets with multiple functions.

Deciphering the seasonal dynamics of microplastic morphotypes and associated co-contaminants along the northwest coast of India

In the present study, the northwest coast of India, bordering the Arabian Sea, was selected to evaluate the microplastic (MP) abundance. This is the first study to emphasize the effects of different seasons on MP distribution. The collected MPs were dried, segregated, and evaluated based on their morphotype, size, color, and polymer type. A total of 1756.6, 7326.6, and 202 particles/kg of sand were estimated in the pre-monsoon, monsoon and post-monsoon seasons, respectively, with a dominance of polypropylene (PP) type of plastic in the pre-monsoon and high-density polyethylene (HDPE) in monsoon and post-monsoon seasons. HDPE and PP collected MPs during the monsoon season were further characterized for associated contaminants. Metal absorbance was detected using SEM-EDX mapping and ICP-MS. The presence of organic compounds (OCs) was analyzed using GC-MS. MPs exhibit distinct associations with metals, among which the HDPE pellet morphotype exhibits a higher range of metal adsorption. Total 61 different OCs were associated with MPs. The HDPE pellets contained the highest amounts of hydrophobic organic compounds. PP pellets were found to contain triglycerides, fatty aldehydes, and alkaloids, along with HOCs. Among morphotypes, pellet forms of MPs were found to adsorb more contaminants. These co-contaminants infiltrate the study area through sewage runoff and shoreline debris deposition, subsequently interacting with MPs. Furthermore, the MP diversity was studied by employing the MP diversity integrated index, which suggests that most of the MP diversity was observed in the pre-monsoon period. The pollution load index employed an MP risk assessment, which presented a low degree of MP contamination. In contrast, the polymer hazard index was calculated as 21650.3 in post-monsoon, placing the area under the extreme danger category. It is evident from the data that the types of MP is more important than their number. Thus, MP morphotypes have importance in the adsorption of co-contaminants.

Modification of Talc and Mechanical Properties of Polypropylene-Modified Talc Composite Drawn Fibers

A large amount of the polypropylene (PP) produced worldwide is used in the form of fibers. In this work, a new modification route for talc and PP is investigated, which is based on the in situ polymerization of a silane–siloxane monomer mixture on the surface of talc particles or PP pellets, respectively. The obtained modified talc and PP samples were used for the development of PP-talc composite drawn fibers. Tensile tests, thermogravimetry (TGA), and X-ray diffraction (XRD) were used for the characterization of the materials. It was observed that such a modification procedure resulted in the exfoliation of some talc particles. Enhanced tensile strength was observed for composite drawn fibers of a low talc content (1% with respect to PP) and a low modifier content (2% with respect to talc), while co-aggregation of talc and silicone may occur at high silicone and talc contents, resulting in the inferior mechanical performance of the corresponding composites. It was concluded that the produced silicone polymer simultaneously acts as a modifier, antioxidant, and compatibilizer. The proposed modification route is promising and should be further optimized.

Laboratory Measurements of Pyrene and Acenaphthene Partition into Microplastics

Microplastics are a major environmental issue. In marine systems, these break down into small fragments that may lodge within organisms, but they behave as vectors for chemicals when pollutants such as metals, polycyclic aromatic hydrocarbons (PAHs), pesticides, and pharmaceuticals are absorbed by the particles. The rate and extent of uptake of organic compounds onto microplastics is dependent on a range of factors such as the sites available on the surface, the type of plastic, and the compound being sorbed, with hydrophobicity an important property. Laboratory experiments determined the uptake of pyrene and acenaphthene (and sometimes phenanthrene) onto pellets of polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyoxymethylene (POM), polypropylene (PP) and polystyrene (PS). The kinetics of uptake in the experiments reveals half-lives ~10 h. The extent of partition onto the plastic pellets was similar for pyrene and phenanthrene, though lower for acenaphthene. This was not surprising because the octanol-water distribution coefficient of acenaphthene is about an order of magnitude smaller than that of pyrene, suggesting it is less hydrophobic. The PAHs are distributed most strongly into PP but only weakly into PVC. The fragmentation and oxidation of microplastics means that they sorb increasing amounts of organic material as they age.

Evaluation of the Thermal Stability and Micro-Modification Mechanism of SBR/PP-Modified Asphalt.

To evaluate the thermal stability of composite polymer-modified asphalt, thermoplastic elastomer styrene-butadiene rubber (SBR)/polypropylene (PP) pellets were prepared using a hot-melt blending technique, with butyl rubber powder and waste polypropylene pellets as raw materials. The effects of different evaluation indexes on the thermal stability of SBR/PP-modified asphalt were investigated using a frequency scan test and a multi-stress creep recovery (MSCR) test, and the compatibility of SBR/PP particles with asphalt was studied using the Cole-Cole diagram and microstructure images. The tests show that, firstly, the performance grade (PG) classification of asphalt can be improved by adding an SBR/PP thermoplastic elastomer to enhance the adaptability of asphalt in high- and low-temperature environments, and the evaluation separation index can reflect the high-temperature storage stability of composite-modified asphalt more reasonably. Additionally, the larger the rubber-to-plastic ratio the worse the high-temperature thermal stability of composite-modified asphalt. Moreover, the addition of additives to the composite particles can promote the SBR/PP particles in the asphalt to be more uniformly dispersed, forming a more desirable microstructure and improving the thermal stability of composite-modified asphalt. Ultimately, the semicircular curve of the Cole-Cole diagram can reflect the compatibility characteristics of the two-phase structure of SBR/PP-modified asphalt, which can be used as an auxiliary index to evaluate the compatibility of polymer-modified asphalt.

Transforming polypropylene waste into transparent anti-corrosion weather-resistant and anti-bacterial superhydrophobic films

The global pollution crisis arising from the accumulation of plastic in landfills and the environment necessitates addressing plastic waste issues. Notably, polypropylene (PP) waste accounts for 20% of total plastic waste and holds promise for hydrophobic applications in the realm of recycling. Herein, the transparent and non-transparent superhydrophobic films made from waste PP are reported. A hierarchical structure with protrusions is induced through spin-casting and thermally induced phase separation. The films had a water contact angle of 159° and could vary in thickness, strength, roughness, and hydrophobicity depending on end-user requirements. The Bode plot indicated enhanced corrosion resistance in the superhydrophobic films. Antibacterial trials with Escherichia coli and Staphylococcus aureus microbial solutions showed that the superhydrophobic film had a significantly lower rate of colony-forming units compared to both the transparent surface and the control blank sample. Moreover, a life cycle assessment revealed that the film production resulted in a 62% lower embodied energy and 34% lower carbon footprint compared to virgin PP pellets sourced from petroleum. These films exhibit distinctiveness with their dual functionality as coatings and freestanding films. Unlike conventional coatings that require chemical application onto the substrate, these films can be mechanically applied using adhesive tapes on a variety of surfaces. Overall, the effective recycling of waste PP into versatile superhydrophobic films not only reduces environmental impact but also paves the way for a more sustainable and eco-friendly future.

Impact of Hybrid Biomass Fillers on the Physico-Mechanical and Degradation Properties of Utility Polymers

The impact of cassava peel-rice husk hybrid fillers on the physico-mechanical and degradation properties of utility polymers were studied. Fine powders of cassava peel and rice husk of 75µm mesh size were homogeneously mixed at the ratio of 1:1 to form the hybrid filler. The virgin crystalline pellets of Low-Density Polyethylene and Polypropylene were filled with varying weight percentages (5, 10, 15, and 20) of the hybridized filler and the composites produced via the injection moulding technique at 288oC. The mechanical properties were studied according to ASTM standards. The surface morphological properties and thermal properties were studied with Scanning Electron Microscope and Differential Scanning Calorimeter respectively. The results of the mechanical properties showed improved tensile strength, compression strength and hardness as the filler load increases till optimum filler load was attained, while the percentage elongation at break decreased with increase in filler load. The shear modulus was found to be irregular. The creep behaviour with the PP composites was irregular but linear with LDPE composites. The solvent imbibition showed no increase in water, but less than 1% increase in toluene. The DSC result showed the hybrid filler had positive impact on LDPE composite but no effect on PP composite. The micrographs showed improved properties as the filler loading increases. Biodegradation test in soil revealed a reduction in the mass of the composites after a 6- month burial period indicating that the composite is degradable and eco- friendly. From the results, the cassava peel-rice husk hybrid filler can be employed in formulation of polymers where strength, water resistance and biodegradability is required such as plastic tiles. Thus, it is suggested that agro-wastes such as cassava peel and rice husk could be used as fillers in production of degradable plastics as they are accessible, cheap, easy to use and eco-friendly.

Mechanical behavior analysis of polypropylene composites with waste PET felt fibers

AbstractThe utilization of plastic waste is another way to protect the ecology and reduce plastic pollution, which researchers and industries have been effectively focusing on for the last decade. Polyethylene terephthalate felt (PETf) is a packaging material abundantly utilized in the automotive sector and is released as waste, and its popularity as an industrial waste necessitates attention to proper disposal. Therefore, the current study utilized waste PETf as a reinforcement (5–15 wt%) for a polypropylene (PP) matrix using various molding approaches, in light of the higher aspect ratio of the fibers. In the first approach, the fibers were extracted from PETf through a mechanical process, and various percentages of PET felt fibers (PETff) were extruded with PP pellets, followed by injection molding. Second, PETf was directly laid on a PP sheet and processed by compression molding. The tensile strength, tensile modulus, and morphological and spectral properties of the fabricated composites were evaluated. Morphological and spectral analyses explain the distribution and interaction of the fibers in the PP matrix. The 10%PETff enhanced the tensile strength and modulus of PP by 37.3% and 52.15%, respectively. Conversely, the 1.5% malic anhydride‐g‐PP (MAPP)‐PP/PETf composites showed similar tensile behavior, with values of approximately 41.53 MPa and 1.6 GPa. In addition, the tensile strength significantly increased by 35.75% with the addition of MAPP. Overall, the current study demonstrates a well‐structured research design that effectively employs waste PETf as reinforcement for PP composites. The mechanical strength of these composites makes them highly versatile and renders them suitable for a wide range of applications, from automotive packaging to the manufacturing of high‐performance automotive components.Highlights Utilized waste PET as reinforcement for manufacturing of PP composite. PET and PP interacted in a self‐reinforcing manner. Injection and compression molding techniques used for PET/PP composites. Repurposing waste PET by compression molding is eco‐friendly practices. PET fibers significantly improved mechanical properties of PP composites.

Enhancement of Polypropylene 3D-Printed Structures via the Addition of SiC Whiskers and Microwave Irradiation.

We report on enhancing the mechanical and structural characteristics of polypropylene (PP) three-dimensional (3D)-printed structures fabricated via fused filament fabrication (FFF) by employing composite PP-based filament with subsequent microwave (MWV) treatment. The composite filament contained a minute (0.9 vol %) fraction of silicon carbide whiskers (SiCWs) and was prepared via melt blending of PP pellets with SiCW using an extruder. The surface of the whiskers was modified with trimethoxy(octadecyl) silane to improve compatibility between the polar SiCW and nonpolar PP matrix. We employed SiCWs in composite filament because of the whiskers' high thermal conductivity and ability to generate heat locally under MWV irradiation. Indeed, we were able to conduct the heating of printed parts by MWV without sacrificing the structural integrity and improving the overall adhesion between the 3D-printed polymer layers. Our modeling captures an extent of heating upon MWV irradiation observed in our experiments. In general, utilization of the composite PP/SiCW filament significantly improved the printed parts' mechanical characteristics and sintering level compared to those made from pure PP filament. Specifically, after the MWV treatment, the adjusted (for density) storage modulus of the PP/SiCW material was just ∼20% lower than that for the PP sample obtained by conventional compression molding. After the MWV irradiation, Young's modulus, yield stress, and toughness of the printed structures were increased by ∼65, 53, and 55%, respectively. We attribute the improvement of mechanical properties via MWV treatment to enhancing the entanglement level at the weld.

Development of Nano-Sized Copper-Deposited Antimicrobial Air Filters Using a Mixed Melt-Blown Process.

Air purification devices, such as air purifiers, provide fresh air by filtering out airborne pollutants, dust, and other harmful substances using various filter systems. While air filters are generally effective in filtering pollutants such as dust, they encounter a challenge when filtering harmful microorganisms such as mites, bacteria, mold, and viruses. These microorganisms, which are present in public transport and public indoor spaces, tend to proliferate on the surface of the filter media, eventually reintroducing themselves into the air or causing unpleasant odors. To address this issue, herein, copper particles were prepared as one masterbatch and deposited on polypropylene (PP) pellets through plasma vacuum deposition to effectively filter dust and microorganisms and prevent their growth on the surface of the filter media. After adding 3-10 wt.% of the masterbatch to conventional PP pellets to fabricate a filter media, the distribution of copper on the surface of the filter media was observed through a scanning electron microscope. To verify the safety and effectiveness of the antimicrobial material, the filter media containing antimicrobial particles was tested using Escherichia coli (E. coli) and Staphylococcus aureus through a filter emission test.

Intertwined synergistic abiotic and biotic degradation of polypropylene pellets in marine mesocosms

The accumulation of plastic waste in the oceans has caused growing concern for its effects on marine life. The interactions of plastics with environmental factors have been linked to fragmentation to micro- and nanoparticles with different properties and consequences, but the mechanism of fragmentation has not been fully understood yet. In this work, we investigate the combined effect of marine communities and ultraviolet (UV) radiation towards the degradation of virgin and artificially weathered polypropylene (PP) pellets after a long-term incubation period in marine mesocosms. The surface chemical alterations and deterioration of the polymer, in conjunction with the attachment and evolution of marine bacterial communities, the development of biofilm and exopolymeric substances (EPS), as well as the colloidal properties (zeta-potential and hydrodynamic diameter) of the mesocosms were studied. The surface area of both types of pellets decreased over time, despite no concrete weight change being observed. Cell growth, EPS production and colloid particle size were correlated to the loss of area. Therefore, we propose that surface area could be effectively monitored, instead of weight loss, as an alternative indicator of polymer degradation in biodegradation experiments. Changes in the chemical structure of the polymer, in addition to the evolution of the biological factors, implied that a complex degradation process alternated between two phases: an abiotic phase, when UV irradiation contributes to the deterioration of the polymer surface layers and a biotic phase, when marine communities degrade the weathered polymer surface to reveal the underlying layer of virgin polymer. Finally, microscopic particles, produced as a result of the decrease in pellet area, promoted the aggregation of colloidal particles. The role and impacts of these colloidal particles in marine ecosystems are yet as unidentified as that of micro- and nano-sized plastic particles and call for further investigation.

Long-Lasting Electret Melt-Blown Nonwoven Functional Filters Made of Organic/Inorganixc Macromolecular Micron Materials: Manufacturing Techniques and Property Evaluations.

Melt-blown nonwoven fabrics for filtration are usually manufactured using polypropylene, but after a certain time period the middle layer of the mask may have a reduced effect on adsorbing particles and may not be easily stored. Adding electret materials not only increases storage time, but also shows in this study that the addition of electret can improve filtration efficiency. Therefore, this experiment uses a melt-blown method to prepare a nonwoven layer, and adds MMT, CNT, and TiO2 electret materials to it for experiments. Polypropylene (PP) chip, montmorillonite (MMT) and titanium dioxide (TiO2) powders, and carbon nanotube (CNT) are blended and made into compound masterbatch pellets using a single-screw extruder. The resulting compound pellets thus contain different combinations of PP, MMT, TiO2, and CNT. Next, a hot pressor is used to make the compound chips into a high-poly film, which is then measured with differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The optimal parameters are yielded and employed to form the PP/MMT/TiO2 nonwoven fabrics and PP/MMT/CNT nonwoven fabrics. The basis weight, thickness, diameter, pore size, fiber covering ratio, air permeability, and tensile property of different nonwoven fabrics are evaluated in order to have the optimal group of PP-based melt-blown nonwoven fabrics. According to the results of DSC and FTIR measurements, PP and MMT, CNT, and TiO2 are completely mixed, and the melting temperature (Tm), crystallization temperature (Tc) and endotherm area are changed accordingly. The difference in enthalpy of melting changes the crystallization of PP pellets, which in turn changes the fibers. Moreover, the Fourier transform infrared (FTIR) spectroscopy results substantiate that PP pellets are well blended with CNT and MMT, according to the comparisons of characteristic peaks. Finally, the scanning electron microscopy (SEM) observation suggests that with a spinning die temperature of 240 °C and a spinning die pressure lower than 0.01 MPa, the compound pellets can be successfully formed into melt-blown nonwoven fabrics with a 10-micrometer diameter. The proposed melt-blown nonwoven fabrics can be processed with electret to form long-lasting electret melt-blown nonwoven filters.

Real-Time Monitoring of Pellet Plastication in a Full-Flight Screw and Kneading Disk Elements of a Co-Rotating Self-Wiping Twin-Screw Extruder by Acoustic Emission (AE) Sensing

The plastication of pellets in a co-rotating twin-screw extruder is a significant concern for product homogeneity and stability in the plastic industry. We developed a sensing technology for pellet plastication in a plastication and melting zone in a self-wiping co-rotating twin-screw extruder. The collapse of the solid part of the pellets emits an elastic wave as an acoustic emission (AE) that is measured on the kneading section of the twin-screw extruder using homo polypropylene pellets. The recorded power of the AE signal was used as an indicator of the molten volume fraction (MVF) in the range of zero (fully solid) to unity (fully melted). MVF decreased with increasing feed rate monotonically in the range of 2-9 kg/h at a screw rotation speed of 150 rotations per minute (rpm) because of the reduction in the residence time of pellets in the extruder. However, the increase in feed rate from 9 to 23 kg/h at 150 rpm resulted in an increase in the MVF as the friction and compaction of pellets caused their melting. The AE sensor could elucidate the pellet's plastication phenomena caused by friction, compaction of pellets, and melt removal in the twin-screw extruder.

Regenerated cellulose fabric reinforced bio-based polypropylene sandwich composites: fabrication, mechanical performance and analytical modelling

Sandwich composites were fabricated successfully with the balsa wood as core material and regenerated cellulose fabric bio-based polypropylene (PP) composite skins. The regenerated cellulose fabric PP composites were produced using two different methods: the conventional stacking lay-up and directly using PP pellets. Sandwich composites were made using the hot press equipment with the customized mold. The sandwich composite system and bio-composite laminate were designed to achieve very close weight to compare the key mechanical properties that each design can bear. It was evidenced from the experimental results that 416% increase in the bending load bearing property of the part can be obtained when sandwich structure was used. These experimental results were in close agreement with one of the analytical modelling utilised. The drop weight impact test results demonstrated that the sandwich specimen is capable of withstanding more than 6 kN load and absorbing the impact energy of 28.37 J.

Selection of microorganisms capable of polyethylene (PE) and polypropylene (PP) degradation

Microorganisms degrade microplastics, but their potential is still not fully exploited, e.g., due to inadequate selection of microorganisms. We developed an effective selection method of microorganisms capable of polyethylene (PE) and polypropylene (PP) degradation and assessed the scale of polymer degradation by microbial populations.We isolated seven bacterial strains (three Priestia megaterium strains, Klebsiella pneumoniae, Pseudomonas fluorescens, Enterobacter ludwigii, Chryseobacterium sp.) and seven fungal strains (four Fusarium spp., two Lecanicillium spp. and Trichoderma sp.) with PE degradation potential, as well as seven bacterial strains (five Serratia marcescens and two Enterobacter spp.) and six fungal strains (four Aspergillus spp., Fusarium oxysporum and Penicillium granulatum) with PP degradation ability. Scanning electron microscopy (SEM) analysis confirmed the presence of a biofilm and revealed surface changes in both PE and PP pellets, but the greatest changes (microcracks and corrugations) were observed for PP incubated with bacteria. Fourier transform infrared (FTIR) spectroscopy confirmed the structural changes on the studied polymer surfaces.In conclusion, the isolation of plastic-degrading bacteria and fungi from waste landfills represents an effective strategy for the collection of microorganisms with high potential for PE and PP degradation. The bacteria and fungi revealed better potential for PP degradation and PE degradation, respectively.

Synthesis and characterization of biocomposites based polypropylene/thermoplastic starch- reinforced with natural STIPA TENACISSIMA fibers and PP-g-MA

The current work aims to develop environmentally friendly plastic materials by preparing a composite polypropylene/thermoplastic starch (PP/TPS) using a melt-compounding process. In order to improve the compatibility of the two naturally incompatible polymers, natural Stipa tenacissima fibers treated on their surfaces and polypropylene (PP) pellets grafted with Maleic Anhydride (MA) were added to the mixture (PP and TPS). The mixture was then prepared using the melt-mixing method in various concentrations. X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA)/Differential thermal analysis (DTA), and mechanical tensile tests were then used to characterize the various formulations. SEM images revealed that the addition of (PP-g-MA) and natural fibers resulted in good starch plasticization and higher thermoplastic starch dispersion in the polypropylene matrix. It was also discovered that increasing the TPS concentration over the PP concentration tends to reduce the mechanical tensile properties. However, the composite with 15% TPS had the best mechanical properties. The thermogravimetric analysis (TGA) results revealed that the organic filler used acted as a reinforcing agent, increasing the thermal stability of the polypropylene/thermoplastic starch (PP/TPS) compound.