Mixture Of Polyethylene Research Articles

Plastic-made diesel (PMD) from pyrolysis via vacuum distillation process- A waste recycling fuel to diesel engine performance and emissions improvement

Plastic applications are remarkably increasing nowadays; thus disposal of waste plastic and its negative environmental impact is a great challenge. Turning waste plastic into useful diesel as an alternative to petroleum fuel in the diesel engine is very attractive for communities in terms of waste plastic recovery and reduction in dependency on fossil fuel. This study conducted experiments to evaluate the engine performance and emissions using plastic-made diesel (PMD) which was produced from pyrolytic crude oil of a mixture of high-density polyethylene (HDPE), polypropylene (PP) and polystyrene (PS) with equal proportion using a vacuum distillation process. The pyrochemical properties of PMD were first evaluated after distillation and tabulated. Then, three different ratios (5%, 10% and 20%) of PMD with ultra-low sulfur diesel (ULSD) were used as a diesel engine fuel to investigate engine performance and emission characteristics at variable speeds and loading operations. Results showed that the brake power (BP), torque and brake thermal efficiency of the engine with PMD20 were 2.9%–3.84%, 3.01%–3.21% and 3.9%–4.74% higher than those with ULSD at all tested conditions. The brake-specific fuel consumption (BSFC) of the engine using PMD20 decreased by about 3.77% compared to the engine using ULSD, thereby indicating less fuel usage at various load circumstances than the ULSD. Furthermore, CO emissions from PMD20 were 14.51% lesser than ULSD, and about 7.8% and 4.22% lesser than from PMD5 and PMD10 at all loading operations, respectively. The HC emissions of PMD20 were 15.1%–18.7% lower than that of the ULSD. The NOx emissions decreased by 2.06%, 3.01% and 3.95% on PMD blends PMD5, PMD10 and PMD20 compared to ULSD. These analyses demonstrate that PMD is a potential alternative fuel for engines and provides a useful means to recover the waste plastics.

Enhancement of barrier properties regarding contaminants from recycled paperboard by coating packaging materials with starch and sodium alginate blends

Novel composite packaging materials based on „clever paper“ (CP) (a mixture of polyethylene with calcium carbonate in a mass ratio of ∼1:1) with a coating layer of biodegradable polymers – corn starch (St) and sodium alginate (Alg) with and without activated carbon – were tested to determine their barrier properties against several substances (undecane, heptadecane, dodecane, triethylcitrate, dipropylphthalate, 4-methylbenzophenone, cholestane) that simulate the migratable contaminants from recycled paperboard. Industrial samples of synthetic films (LDPE, BOPP, BOPET, EVA, PLA, PVA), as well as films based on starch/alginate (St/Alg) blends (St/Alg 90/10 and St/Alg 50/50) have been tested as well. Good barrier properties against the penetration of mineral oils (less than 5% undecane has permeated after 10 days at 40 °C) were demonstrated by the film based on St/Alg 90/10. The coating of CP by a layer consisting of St/Alg 90/10 and activated carbon (AC) yielded the composite material CP/St/Alg 90/10/AC with very low permeability (close to aluminum foil). To further showcase the effectiveness of starch/alginate coatings against penetration of contaminants, additional tests were performed with purchased recycled paper coated by films based on St/Alg 70/30.

MECHANICAL TEST AND THERMAL STABILITY ON THERMOPLASTIC SAGO (Metroxylon sagu Rottb.) COMBINATION OF POLYETHYLENE AND POLYPROPYLENE

Polyethylene is a polymer that has good elasticity properties, while polypropylene is a polymer with a high tensile strength value. Thus, the combination of these two polymers is expected to increase the value of tensile strength and elasticity. A biocomposite consisting of a mixture of Polyethylene-Polypropylene and thermoplastic sago starch (TPSS) was successfully prepared using the mixing method in an internal mixer. TPSS is made by reacting starch and glycerol with a composition of 65:35 wt.%. Compatibility was made by reacting Polyethylene-Polypropylene: Maleic anhydrate: Benzoyl peroxide with a composition of 88:9:3 wt. %. The match concentration used was 10wt.% based on the TPSS weight. The concentration of the Polyethylene-Polypropylene mixture starts from 0.10,15,20,25,30 and 100wt.%. The characterizations carried out are mechanical properties analysis are tensile strength, elongation at break and elasticity, FTIR analysis, and thermal properties are TGA and DTA. According to the test results, the addition of a mixture of polyethylene and polypropylene can increase the tensile strength from 1.7292MPa (without a mixture of polyethylene and polypropylene) to 4.8334MPa and the elongation at break also increases from 0.23% to 1.72% at a concentration of 30wt.%. Meanwhile, Young’s Modulus decreased from 740 to 281MPa at a concentration of 30 wt. %

Mechanical and Thermal Properties of the Titanium Dioxide-Modified Composites Based on Aluminum Hydroxide and a Polyethylene Mixture

Mechanical and Thermal Properties of the Titanium Dioxide-Modified Composites Based on Aluminum Hydroxide and a Polyethylene Mixture

THERMOMECHANICAL PROPERTIES OF COMPOSITE MATERIALS BASED ON MIXTURES OF HIGH AND LOW DENSITY POLYETHYLENES

The results of the research into the influence of polymer components ratio - high density polyethylene and low density polyethylene, into the regularity of changes in thermomechanical properties are presented. The deformation was measured at varying temperatures and at a constant load of 0.5 kg/cm2 . The concentration of low density polyethylene varied from 10 to 100 wt%. Depending upon the test temperature, two physical states were recorded: solid and viscous-flow. It found that as the concentration of low-density polyethylene in the composition of the polymer mixture rose, the transition temperature in the softened state and the transition temperature in the viscous-flow state dropped. The differential thermal analysis curves showed that at low concentrations of high density polyethylene, two-phase systems were formed in the polymer system. The study of composites based on aluminum hydroxide and a mixture of high and low density polyethylene revealed a wave-like change in softening and viscous-flow temperatures.

Magnetism-Assisted Density Gradient Separation of Microplastics.

A versatile method for the efficient separation of different types of microplastics from particle mixtures is presented. Magnetism-assisted density gradient separation (Mag-DG-Sep) relies on a bespoke separation cell connected to a gradient pump and located between two like-pole-facing neodymium magnets. In Mag-DG-Sep, particle mixtures initially sunk in water are subjected to a gradient of increasing concentration of MnCl2, enabling the sequential suspension and collection of particles with different densities. The suspension process is assisted by the paramagnetism of the MnCl2 solution placed between the two magnets, which contributes to focusing the ascending particles from the bottom of the separation cell to the outlet, thus enhancing the resolution of the separation process. To demonstrate the concept, a mixture of polyethylene (PE) polymer particles with a similar size range (180-212 μm) but different densities (ca. 0.98, 1.025, 1.08, and 1.35 g cm-3) was selectively separated in a single Mag-DG-Sep run. These particles were also efficiently separated when mixed with other types of particles, such as glass or soil. A generic linear MnCl2 gradient can be directly applied for sample screening covering a broad range of densities (0.98-2.20 g cm-3), while steps can be introduced in the gradient, increasing the separation resolution of particles with close densities (1.025-1.08 g cm-3). As a proof-of-concept application, Mag-DG-Sep facilitated sample preparation of microplastics present in a soil sample prior to their examination by attenuated total reflection Fourier-transform infrared spectroscopy.

Potential Reduction of Low-Density Polyethylene (LDPE) Plastic Waste as A Paving Block Mixed Material

Paving blocks are the result of a mixture of Portland cement, sand, water, and with or without other additives. Based on the results of sampling the composition of plastic waste in temporary shelters for 7 days, the percentage of plastic waste generated is 14%, whereas the percentage of LDPE plastic waste is 8% and the non-LDPE is 6%. This research was conducted with a ratio of cement and sand of 1: 4 with variations of a mixture of low-density polyethylene (LDPE) plastic at 0%, 0.5%, 1%, 1.5%, and 2% by weight of sand. Paving block quality testing was carried out at the Environmental Engineering and Quality Laboratory, Department of Environmental Engineering and Concrete Laboratory, Civil Engineering, Adhi Tama Institute of Technology Surabaya. The results of the study showed that the greatest compressive strength was obtained in paving blocks with a plastic variation of 0.5%, which is 24,83 MPa. While the lowest compressive strength value is obtained at the paving block variation of 1.5%, which is 12.32 Mpa. The test results for the largest water absorption were obtained on paving blocks with a plastic variation of 2% with an average absorption of 6.45%, while the lowest water absorption was found in paving blocks with 1% plastic variation with an average absorption of 4.65%. it was concluded that the addition of reduced density polyethylene (LDPE) plastic from 0.5% to 2% had no significant impact on the addition of compressive strength and water absorption but tended to experience a decrease in the quality of the comparison sample. The potential for reducing LDPE plastic waste is 203,376 grams/day and produces 8,135 paving blocks with quality B. The purpose of this study is to the utilization of low-density polyethylene (LDPE) plastic waste in paving blocks and the effect on the quality of compressive strength and water absorption.

Statističko istraživanje recikliranja plastičnog otpada ponovnom uporabom u tlu

Recycling and reusing plastic waste are key options for ameliorating its negative effects on the environment and the economy. This paper proposes evolutionary polynomial regression (EPR) as a powerful technique to predict the compressibility behavior of sand and high-density polyethylene (HDPE) mixtures. In the investigation, a series of large-scale oedometer experiments were conducted. The results of the coefficients of lateral earth pressure and volume compressibility coefficients of different mixtures were used to develop EPR models. The model parameters were evaluated by sensitivity analyses. The results showed that the best developed EPR model is robust for estimating the characteristics of sand and HDPE mixtures.

Copolymers Prepared by Exchange Reactions Enhance the Properties of Miscible Polymer Blends

Although many polymers are not miscible or chemically incompatible, some form miscible blends, which feature tunable properties relative to those of their constituent polymers. Here, we introduce an approach to enhance the mechanical properties of miscible blends of a thermoplastic polyurethane and a sustainable polyester, polycaprolactone (PCL), by introducing a copolymer of the two corresponding monomers. Rather than polymerizing the copolymers from new monomers, they were generated by a solvent-free, ester/urethane bond-exchange process conducted during the coextrusion of polyurethane and PCL. Urethane/ester exchange was confirmed by quantitative 13C NMR spectroscopy, along with well-defined size-exclusion chromatography of the copolymers. Extrusion time and temperature affected the extent of exchange, with shorter residence times and lower temperatures giving limited bond exchange and blockier copolymers. In contrast, longer extrusion times and higher temperatures provided more extensive exchange and approximately random copolymers. Mixtures of the polyurethane and polyester homopolymers with 10 wt % copolymer demonstrated improved tensile stress and strain relative to coextruded mixtures of thermoplastic polyurethane and polyethylene because of the enhanced crystallization of the miscible homopolymer blend facilitated by the added copolymer compatibilizer. This approach represents a simple and general strategy for obtaining copolymers from homopolymers rather than using specialized polymerization techniques, allowing for products from mixed polymer waste to be used as compatibilizers or otherwise enhance the properties of the original homopolymer mixtures.

High and low temperature performance of polyethylene waste plastic modified low noise asphalt mixtures

• Waste plastics can be a viable alternative for reducing polymer in asphalt mixtures. • PE compared to non-PE with same binder improved resistance against deformation. • PmB mixture compared to PE showed higher resistance against cyclic loading. • SCB test showed PE mixtures had slightly improved fracture energy toughness. Waste plastic in low noise asphalt mixtures can be a viable alternative to asphalt mixtures with polymer modified bitumen. The performance of low noise semi dense asphalt (SDA) mixtures with waste polyethylene (PE) plastic is investigated. The cyclic compression test (CCT) and semi-circular bending (SCB) test was used for characterization of high and low temperature performance. The CCT results revealed that the PmB mixture had shown significantly higher resistance compared to the PE mixture. However, the PE modification showed some improvements in terms of CCT loading when compared with mixtures using the same base binder without PE. The SCB test results found that on average using higher content of PE mixtures had slightly improved fracture energy and lower fracture toughness compared to asphalt mixtures using polymer modified binder (PmB). The electron microscopy images showed that the PE does not completely melt during the mixing process and exists as elastic bodies within the mixture. The findings showed that at low temperatures, both PE and binder behave elastically, whereas at higher temperatures, PE remains elastic, and binder's viscoelasticity becomes dominant. These results highlight the importance of selecting proper base binder for such modifications with waste plastic.

Kinetic synergistic effect in co-pyrolysis of Eucalyptus globulus with high and low density polyethylene

The pyrolysis of Eucalyptus globulus (EG) with different blends of high density polyethylene (HDPE) and low density polyethylene (LDPE) by thermogravimetry has been studied. ASTM-E1641-16 standard method has been used to evaluate the kinetics during the pyrolysis of the studied blends. For all feedstocks (EG, HDPE and LDPE) and blends studied, the relative content (%) of the volatile organic compound has been determined by GC–MS analysis. Different synergistic effects on the activation energy of EG blends with HDPE and LDPE have been found. EG-HDPE blends showed a minimum activation energy (Ea) (125 kJ mol−1) at the 80% EG–20% HDPE ratio, while the minimum Ea value for EG-LDPE blends was found at the 60% EG–40% LDPE ratio (135 kJ mol−1) has been identified. To test which components exert a greater synergistic effect, mixtures of HDPE and LDPE with the main components of eucalyptus (cellulose, hemicellulose and lignin) have also been studied. However, no synergistic effects on the pyrolysis of cellulose have been detected. Moreover, in hemicellulose and lignin with both types of polyethylene mixtures, a significant decrease in Ea has been appreciated. The lowest Ea values for 60% cellulose–40% HDPE (167 kJ mol−1) and 60% lignin–40% HDPE (140 kJ mol−1) has been calculated. On the other hand, minimum values for 40% cellulose–60% LDPE (166 kJ mol−1) mixture and for 40% lignin–60% LDPE (168 kJ mol−1) mixture have been detected. Thus, the decrease in both Ea and the Arrhenius pre-exponential factor on the eucalyptus-polyethylene blends to the presence of hemicellulose and lignin can be attributed. Moreover, during the co-pyrolysis of HDPE-EG mixtures, n-paraffins, ketones, phenols and sugars are the main VOCs identified. In contrast, in LDPE-EG mixtures, only n-paraffins (55%) and olefins (44%) have been identified.

The in situ synthesis of weakly entangled ultrahigh‐molecular‐weight polyethylene/polyethylene wax blends and its synergetic disentanglement effect on LLDPE reinforcement

AbstractHigh‐performance ultrahigh‐molecular‐weight polyethylene (UHMWPE)/low‐molecular‐weight polyethylene (PE) mixture additives were proven to be effective for enhancing commercial high‐density polyethylene (HDPE) resins, which were synthesized by the complicated dual‐site immobilized catalyst system. In this paper, PE wax components were preadded in the polymerization reactor for in situ synthesizing the UHMWPE/PE wax binary blends with just a single SiO2/MgCl2 supported Z–N catalyst modified by the active site isolators. The influence of PE wax addition on the catalytic activity, molecular weight, thermodynamic property, particle size, and entanglement density was systematically researched. It was evidenced that the catalytic activity and molecular weight exhibit a linear relationship with the ethylene solubility caused by the PE wax addition. Besides, the competition between chain propagation/crystallization balance and PE wax long chains entanglement effect arising from the PE wax addition leads to the minimum entanglement density (GNt = 0.59) of UHPE‐20%. The disbalance of chain propagation rate and chain crystallization rate can be broken by PE particle fragmentation, inducing rapidly increased entanglements. Furthermore, with the synergistic disentanglement influence of reduced entanglements for UHMWPE and the chain diffusion ability for PE wax, the LU‐30 sample with a mixture of UHPE‐30% and linear low‐density polyethylene (LLDPE) exhibits the optimum strength/stiffness/toughness properties. The tensile strength, Young's modulus, and impact strength of LU‐30 reach 18.2 MPa (+4%), 172.1 MPa (+53.8%), 60.5 kJ/m2 (+13.1%), respectively, compared with those of pure LLDPE. The overall enhanced mechanical properties are attributed to the intensive signal intensity and tightly stacked form of shish‐kebab structures, which were verified by the two‐dimensional small angle X‐ray scattering and two‐dimensional wide angle X‐ray diffraction patterns. In addition, the in situ polymerization method of UHMWPE/PE wax with SiO2/MgCl2 supported Z–N catalysts exhibits a great probability of efficient utilization of low‐molecular‐weight polyethylene by‐products (PE wax).

Catalytic Co-pyrolysis of empty fruit bunch and high-density polyethylene mixtures over rice husk ash: Thermogravimetric, kinetic and thermodynamic analyses

Rice husk ash (RHA) has been used as a catalyst precursor but there are lack of studies on the application of the resulting catalyst. This study allows researchers to have an insight on using RHA-sourced catalysts in pyrolysis and be encouraged to utilize waste materials in the future. The goal of this study is to examine the effect of catalysts derived from rice husk ash (RHA) using the solvent-free method, labelled as RHA-T, on the catalytic co-pyrolysis of empty fruit bunch (EFB) and high-density polyethylene (HDPE) via thermogravimetric analyser (TGA). Comparisons were then made with co-pyrolysis and catalytic co-pyrolysis over raw RHA and Hydrogen-exchanged Zeolite Socony Mobil-5 (HZSM-5). Thermogravimetric analysis was conducted (EFB-to-HDPE mass ratio of 1:1, catalyst-to-feedstock mass ratio of 1:1) in a nitrogen atmosphere, where samples were heated from 30 °C until 700 °C (heating rate 20 °C/min). The order of runs with highest mass loss in the second phase is as follows, with the term ‘BP’ indicating the biomass-plastic feedstock: BP-RHA-T (98.17 wt%), BP-RHA (96.25 wt%), BP (86.82 wt%) and BP-HZSM-5 (70.59 wt%). Kinetic analysis using Coats-Redfern method and comparing between different diffusional reaction models showed that using BP-RHA-T follows a one-dimensional diffusion reaction, similar to the non-catalytic run. Using RHA-T resulted in higher activation energy (83.03 kJ/mol to 84.91 kJ/mol) compared to the non-catalytic run (62.39 kJ/mol to 68.97 kJ/mol). Thermodynamic analysis showed the pyrolysis runs were endothermic and non-spontaneous. Using RHA-T resulted in a higher change of enthalpy, a lower change of Gibbs free energy and a less negative change of entropy. It can be concluded that applying catalysts synthesized using low-cost materials like RHA can improve the degradation of EFB and HDPE via pyrolysis, compared to commercial HZSM-5 catalysts.

Biodegradable polymers based on natural carotenoids

Carotenoids such as curcumin and bixin are polyisoprenoids, and are responsible for red, orange or yellow colors. Curcumin is a yellow hydrophobic polyphenol that presents a low molecular weight. Bixin is a natural color extracted from the Annato tree and its color varies from yellow to red due to the presence of the isomer carotenoid trans-bixin. Food and cosmetic industries use them due to their antioxidant properties. The biodegrading properties of polymer blends can be improved by the addition of vegetable oil, organic and inorganic additives or by mixing them with a biodegradable polymer. According to previous studies, polymers produced by a mixture of Moringa polymer (PMO), polyethylene (PE) and commercial biodegradable polymers (PB), composed of PBAT (poly(butylene adipate-co-terephthalate)/PLA (polylactic acid), presented mechanical properties similar to those of PE, except for a higher biodegradation capacity. Vegetable oils can be used as plasticizers for polymer blends and Moringa oil and improved the biodegradation properties in other studies.

Polymer Composites Supported on Polyolefins and Dried Barley Grass

Benchmark results of physical, rheological and biodegradable properties of low (HDPE 273-83) and high (LDPE 15303-003) pressure polyethylene mixture by a factor of 1:1 supported on dried barley grass flour (200 microns maximum) ( 5–30 % by weight) enhanced by compatibilizer of 10 % (method functionalized with ultrathene alkaline alcohol exchange (ethylene-vinyl acetate copolymer 12206-007) and 1 % processing aid (polyethylene glycol (PEG-115 (4000)). It was concluded that the Young modulus and tensile strength do not decrease significantly with increase in vegetable reinforcement (up to 30 %). To compare the composite properties in terms of biodegradability, moisture uptake, chemical oxygen demand, and weight loss, a 12-month study was performed in laboratory soil. It is shown that an increase in the content of plant reinforcement increases the biodegradability of the composite. Resulting composites can be used in the production of various packaging materials.

Valorization of plastic wastes for production of fuels and value-added chemicals through pyrolysis – A review

Recycling of waste plastics is a promising solution to deal with the pressure on fuel economy in forthcoming years and to address the concern regarding its accumulation in the environment. Municipal Solid Waste (MSW) is a dominant source of plastic waste. Waste management principles can be applied for resource recovery and energy generation. Pyrolysis, a thermochemical recycling method, holds multiple advantages in relation to product utility, energy input and environmental footprint. The focus of this review is to investigate the potential of pyrolysis to convert waste plastic stream comprising of a mixture of High-Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), Polypropylene (PP) and Polystyrene (PS) into fuel and value-added products (VAP). Concentrated efforts are made to analyse process conditions to maximize production of utilizable fractions (gas and oil) and value-added chemicals through pyrolysis. Behaviour of plastic waste components under different process conditions with reaction mechanisms in both catalytic and non-catalytic pathways are explored and summarized. Discussions on the importance of kinetic, particle and reactor scale to develop a process scheme for pyrolysis process, futuristic research directions are also presented. This paper also critically reviews utility requirements and well-established commercial process to comply with environmental legislations.

Flame Propagation Characteristics of Hybrid Explosion of Ethylene and Polyethylene Mixture under Pressure Accumulation

In order to study the flame propagation characteristics of a ethylene/polyethylene hybrid explosion under pressure accumulation, a visual pressure-bearing gas/power hybrid-explosion experimental platform was built. The flame propagation characteristics of polyethylene and ethylene/polyethylene hybrid explosions in the closed vessel were analyzed. The results show that the flame brightness, flame front continuity and average flame propagation velocity of polyethylene dust explosion in the closed vessel increased first and then decreased when the polyethylene dust concentration increased. The curve of the flame propagation velocity with time had obvious pulsation characteristics. Adding 1% and 3% ethylene to different concentrations of polyethylene dust significantly improved its explosion flame brightness, flame front continuity and average flame propagation velocity. Moreover, it also improved the fluctuation amplitude of the explosion flame propagation velocity with time curve. The explosion flame of the polyethylene dust and ethylene/polyethylene hybrid mixture included four zones during the propagation process, which were denoted as the unburned zone, preheated zone, premixed flame zone and dust flame zone. The addition of ethylene to polyethylene dust can significantly increase its thickness of premixed flame zone and preheated zone, and the thickness increased when the ethylene concentration increased.

The Effect of Linear Low-Density Polyethylene and Palm Kernel Shell Ash Mixture on the Physical, Mechanical and Degradation Properties of Paving Blocks

The aim of this research was to evaluate the physical-mechanical parameters of paving stones obtained on the basis of the mixture of linear low-density polyethylene (LLDPE) and palm kernel shell ash (PKSA) waste. The ratio of LLDPE to PKSA waste (% weight) was varied in five treatments: A0 (100:0), A1 (97.5:2.5), A2 (95:5), A3 (92.5:7.5), A4 (90:10) and A5 (87.5:12.5). The physical appearance, thickness, compressive strength, water absorption, and morphological characteristics of the paving blocks were observed. The blocks were observed at ambient temperature, exposed to sunlight, and placed on the ground surface on day 0 and day 365. The results showed that addition of PKSA waste decreased the compressive strength but increased the water absorption capacity without a significant effect on the thickness of the paving blocks. Observation after 365 days showed insignificant decreases of compressive strength and thickness, whereas the water absorption capacity increased slightly. Small cracks and more voids in the surface, and more brittleness were observed. To summarize, composites of LLDPE and PSKA as filler have physical-mechanical properties that can be used for road pavement blocks.

Thermocatalytic Conversion of Plastics into Liquid Fuels over Clays.

Recycling polymer waste is a great challenge in the context of the growing use of plastics. Given the non-renewability of fossil fuels, the task of processing plastic waste into liquid fuels seems to be a promising one. Thermocatalytic conversion is one of the methods that allows obtaining liquid products of the required hydrocarbon range. Clays and clay minerals can be distinguished among possible environmentally friendly, cheap, and common catalysts. The moderate acidity and the presence of both Lewis and Brønsted acid sites on the surface of clays favor heavier hydrocarbons in liquid products of reactions occurring in their pores. Liquids produced with the use of clays are often reported as being in the gasoline and diesel range. In this review, the comprehensive information on the thermocatalytic conversion of plastics over clays obtained during the last two decades was summarized. The main experimental parameters for catalytic conversion of plastics according to the articles’ analysis, were the reaction temperature, the acidity of modified catalysts, and the catalyst-to-plastic ratio. The best clay catalysts observed were the following: bentonite/spent fluid cracking catalyst for high-density polyethylene (HDPE); acid-restructured montmorillonite for medium-density polyethylene (MDPE); neat kaolin powder for low-density polyethylene (LDPE); Ni/acid-washed bentonite clay for polypropylene (PP); neat kaolin for polystyrene (PS); Fe-restructured natural clay for a mixture of polyethylene, PP, PS, polyvinyl chloride (PVC), and polyethylene terephthalate (PET). The main problem in using natural clays and clay minerals as catalysts is their heterogeneous composition, which can vary even within the same deposit. The serpentine group is of interest in studying its catalytic properties as fairly common clay minerals.

Buildup Factor Computation and Percentage Depth Dose Simulation of Tissue Mimicking Materials for an External Photon Beam (0.15–15 MeV)

Nowadays, the use of tissue mimicking material (TMM) is widespread in both diagnostic and therapeutic medicine, as well as for quality assurance and control. For example, patient exposure evaluation during therapeutic tests has been commonly measured using TMMs. However, only a few materials have been developed for research use at the megavoltage photon energy encountered in medical radiology. In this paper, we extended our previous work to cover the photon energy range of 0.15–15 MeV for five human tissues (adipose, cortical bone, fat, lung and muscle). As a selection criterion for TMM, other than the attenuation coefficient, we introduced the computation of the buildup factor (BUF) for a given couple of energy and depth based on the geometric progression fitting method. Hence, we developed a C++ program able to compute BUF for depths up to 40 mean free path. Moreover, we simulated the percentage depth dose (PDD) of a 6 MV photon beam through each tissue and their equivalent materials using the Geant4 Monte Carlo toolkit (version 10.5). After the comparison of a set of parameters (mass attenuation and mass energy absorption coefficients, BUF, equivalent and effective atomic numbers, electron density, superficial and maximal dose and dose at 10 and 20 cm depths), we found that SB3 (a mixture of epoxy and calcium carbonate) and MS15 (a mixture of epoxy, phenol, polyethylene and aluminum oxide) accurately imitate cortical bone and muscle tissues, respectively. AP6 (a mixture of epoxy, phenol, polyethylene and teflon), glycerol trioleate and LN1 (a mixture of polyurethane and aluminum oxide) are also suitable TMMs for adipose, fat and lung tissues, respectively. Therefore, this work can be useful to physician researchers in dosimetry and radiological diagnosis.