Melt Mixing Method Research Articles

An experimental evaluation of a new eco-friendly insulating material based on date palm fibers and polystyrene

The purpose of this study is to minimize the environmental impact and to reduce the cost of petroleum-derived polystyrene by the use of date palm leaves remnants in the production of polystyrene/date palm fiber composite materials (PS-DPF). Moreover, this new material must have mechanical properties and thermal insulation comparable or superior to those of virgin polystyrene (VPS) or other insulating materials. Three types of fibers are used to make samples with fillers of 10%, 20%, and 30% (by weight), namely untreated fiber (UDPF), fiber treated by alkalinisation (ADPF), and fiber treated by benzoylation (BDPF). The melt-mixing method and hot compression molding were used for the production of the composites. Various morphological, mechanical, and thermophysical tests were carried out on the produced composites. From scanning electron microscopy (SEM) micrographs, it was determined that the dispersion of filler and its interfacial interactions with the matrix were improved due to a reduction in the OH group present on the fibers, as validated by the Fourier transform infrared spectroscopy analysis (FTIR). X-ray diffraction (XRD) studies indicate that ADPF has the highest crystallinity index. The PS-DPF composites exhibited satisfactory tensile strength within the range of 14–27 MPa, flexural strength within the range of 31–44 MPa, and tensile and flexural modulus within the range of (2.9–5.9 GPa). The results revealed that alkaline and benzoylated treatment treatments increase the tensile and flexural strength while slightly decreasing the tensile and flexural modulus. Both chemical treatments demonstrated a similar impact on these attributes. Thermogravimetric analysis (TGA) results indicated that samples of PS filled with 30% untreated and treated fibers have the maximum thermal stability compared to VPS, with a slight advantage for the untreated sample when residues are taken into account. The thermal conductivity (λ) of the composites produced was low (0.118–0.141 W/m.K) at 18°C, and its variation was incompatible with the bulk density (ρ), which varied from 860 to 980 kg/m3, and decreased with the incorporation of fibers. Moreover, replacing one-third of the composition of conventional building materials with a PS-DPF composite has shown promise for applications such as thermal insulation, with a reduction in thermal conductivity of up to 50%. The composite materials created have revealed their potential application as thermal insulators, which encourages the frequent exploitation of waste in date-producing countries.

A systematic study of the effect of graphene oxide and reduced graphene oxide on the thermal degradation behavior of acrylonitrile-butadiene rubber in air and nitrogen media

Thermal degradation of acrylonitrile-butadiene rubber (NBR)-graphene oxide (GO)/reduced graphene Oxide (G) composites (NBR-GO/G) was studied in air O2(g) and nitrogen N2(g) media at ∼800°C, using Thermal Gravimetric Analysis (TGA/DTG). The char yield of the composites was high the in N2(g) medium. This was associated with lower weight loss (%) and higher maximum degradation temperatures, Tmax(°C). Doyle simple kinetic approach was used for the first time to estimate the degradation kinetics of the NBR-GO/G composites and large amounts of activation energy Ea (KJ/mol) was observed, particularly for the NBR-GO composites. In O2(g) medium, severe degradation of NBR occurred irrespective of the GO/G-filler content. This suggested that insignificant char yield was produced to protect the scission of the NBR backbone, as decomposition of the main chain seemed to have been accelerated by the high oxygenated moieties (C–O–C, –O–C=O and O–H) decorating GO/G-sheets. For instance, NBR showed ∼89, ∼21 and ∼86 % weight residue, Wr (%) than G0.1, G0.5 and G1 respectively and ∼154, ∼350, ∼92 % higher than the respective GO0.1, GO0.5 and GO1 samples. Although, NBR-G recorded higher Wr(%) than NBR-GO, NBR-GO generally slowed the degradation of NBR than NBR-G composites, possibly due to the presence of high concentration of interactions (NBR—Sx—GO—S—NBR and NBR—O—Hσ+—N σ−—C—NBR) which raised the Ea (KJ/mol) barrier for decomposition. The high thermal stability and compression set (%) properties of NBR-GO/G composites obtained as compared to pure NBR indicated that solution processing techniques used in this current work was very effective than those compounded with melt mixing methods or with GO/G-functionalized nanoparticles. Therefore, this present study provides insights on tailoring rubber-graphene based materials for thermally harsh and high pressure applications such as; oil/gas drilling hose, oil/gas seals, gasket and tire tread materials.

Dielectric Spectroscopy of Melt-Mixed Polypropylene and Pyrolytically Stripped Carbon Nanofiber Composites

In this work, pyrolytically stripped carbon nanofiber (CNF) polypropylene (PP) composites were synthesized following a scalable melt-mixing method, and the effects of CNF weight concentrations on the electrical conductivity, dielectric permittivity, electrical modulus and electrical impedance of PP/CNF composites were studied. Quite unexpectedly, the electrical conductivity of PP/CNF composites improved only slightly as the incorporation of CNFs was raised, yielding a maximum of ~10−10 S m−1 for PP/CNF 5 wt. % composites. The increase corresponded to a gradual improvement of the dielectric constant up to a maximum of ~9 for PP/CNF 5 wt. % composites at 1 MHz, which was attributed to the raise of interface polarization effect. Moreover, the Cole–Cole model was used to analyze the effects of CNF concentrations on the dielectric relaxation of PP/CNF composites, from which was deduced that the incorporation of CNFs increases their dielectric strength and relaxation times. The analysis gathered here aims to provide a better insight into the enhanced dielectric properties observed in low-conducting polymer composites filled with CNFs.

Fabrication of silver ions aramid fibers and polyethylene composites with excellent antibacterial and mechanical properties

Abstract Nowadays, with the continuous understanding of the pathogenic mechanism of bacterium, the demand for antibacterial plastic products had significantly increased. Besides that, many counties issued mandatory standards for plastic products, which imposed strict requirements on ash content to prevent the addition of excessive inorganic matter to plastics in order to avoid weakening the properties of plastics and deteriorating the recyclable property. Based on this, the development of composites with organic fiber-loaded antibacterial agents is of practicable value and urgency. We used an open-ring addition reaction to modified aramid fiber (AF) by utilizing epoxypropyltrimethoxysilane to react with the reactive groups on the surface of AFs. Subsequently, the modified fibers were surface loaded with silver ionic glass beads. After that, a series of high-density polyethylene composites with excellent mechanical properties and antibacterial properties were prepared using melt mixing method. It was shown that the composite had a low ash value (1.88 wt%) even at a higher filling concentration (7 wt%) and the fibers could change the crystalline properties and morphology of the composite. Because of the fiber reinforcement and crystallization induction effects, the tensile strength and elasticity module of the composites could be improved by 141% and 136%, respectively. In addition, the composites had excellent long-lasting contact antibacterial effects against the inhibition of E. coli. The proposed organic fiber loading technique and antibacterial composites will provide a method for designing and preparing eco-friendly and high-performance plastic products.

3D printing of PLA-TPU with different component ratios: Fracture toughness, mechanical properties, and morphology

In this study, three PLA-TPU compounds were prepared by the melt mixing method and after the process of compounding, filament preparation, and 3D printing with Fused Deposition Modeling (FDM). The mechanical properties under compression, tensile, bending, shear modes, and fracture toughness were comprehensively and experimentally assessed. Also, for thermal analysis and microstructural evaluation, Dynamic Mechanical Thermal Analysis (DMTA) and Scanning Electron Microscopy (SEM) were used. The thermal analysis of the PLA-TPU compounds showed an increase and decrease in the loss and storage modulus with increasing PLA value, while all compounds had almost the same glass transition temperature. The results of mechanical tests showed that by raising the amount of PLA, the strength and formability increased and decreased, respectively in all loading modes. The UTS values for PLA50, PLA70, and PLA90 were achieved 27.27 MPa, 40.91 MPa, and 54.18 MPa, respectively. Also, the fracture toughness results were consistent with the mechanical properties. The PLA90 had 1.69 and 2.36 times higher fracture toughness than the PLA70 and PLA50 compounds, respectively. SEM images showed that with the increase in the amount of TPU, the voids caused by the printing and neck growth due to the incomplete integration of the inter and intralayer rasters rises, which is the reason for the decrease in strength and printability. The shear test results also confirmed the SEM images quantitatively and showed that the connection between the layers and density improves with increasing the amount of PLA.

The Synergic Effect of Primary and Secondary Flame Retardants on the Improvement in the Flame Retardant and Mechanical Properties of Thermoplastic Polyurethane Nanocomposites

Recently, nanocomposites of polymers have attracted attention due to their advanced features compared to their complement polymer microcomposites. In this study, thermoplastic polyurethane (TPU) was used as a matrix; antimony trioxide (primary flame retardant) and montmorillonite organo-clay (secondary flame retardant), along with benzoflex (plasticizer), were used as fillers to examine their synergistic effect. Nanocomposites of various compositions (TPU-1 to TPU-6) were prepared via the melt-mixing method and compressed to form sheets of the desired dimensions with a compression molding hydraulic press machine. Characterization of the samples was conducted with Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). A tensile test was performed through a universal testing machine (UTM) which showed that the Young’s Modulus improved from 147.348 MPa for the pure sample (TPU-1) to 244.568 MPa for TPU-6. A UL-94 test was executed to observe flame retardance. The sample of interest (TPU-6) achieved V-0 classification in UL-94. All these results confirmed the synergistic effect of primary and secondary flame retardants. An optimum increase in fire resistance and mechanical strength was observed for TPU-6.

Investigating the role of PA6/GO interactions on the morphological, rheological, and mechanical properties of PA6/ABS/GO nanocomposites

ABSTRACT This study is dedicated to investigate the rheological, mechanical, and morphological properties of polyamide 6/poly (acrylonitrile butadiene styrene) (PA6/ABS) blends in the presence of graphene oxide nanoplates (GO). In this regard, scanning electron microscopy analysis, rheological assessments, and mechanical tests were performed. PA6/ABS (65 wt%, 35 wt%) blends were prepared by melt mixing method in the presence of 0.25 wt%, 0.5 wt%, and 1 wt% GO nanoparticles. Also, to study the effect of mixing protocol on these properties, the mixing sequences varied for the blends containing 0.5 wt% GO. The rheological, mechanical, and morphological analyses demonstrated the formation of significant interaction between PA6 and GO for polymer blends having 0.25 wt% GO. On the other hand, the decrease in the elasticity for the 0.5 wt% GO incorporated polymer blend was attributed to the lubricating role of GO in PA6 as a consequence of weak interactions between PA6 and GO. ABS/GO pre-mixed blend showed good interfacial adhesion between PA6 and ABS as a result of kinetic influence of GO for interfacial localization in PA6/ABS polymer blends. Furthermore, PA6/GO pre-mixing protocol demonstrated the highest elasticity for PA6/ABS blend due to the PA6/GO adhesion reinforcement.

Electrical Properties of Bi<sub>0.5</sub>Na<sub>0.5</sub>TiO<sub>3</sub>/ PVDF(25/75) Composite

The mechanical impact-based energy harvesting behavior of a 0-3 Bi0.5Na0.5TiO3/PVDF(25/75) composite prepared using the melt-mixing method have been demonstrated. X-ray diffraction analyses revealed the formation of a composite sample, while AFM image analyses revealed that BNT-particle sizes ranged between 0.6 and 1.4 μm and were evenly distributed throughout the polymer matrix, and surface roughness was found to be between 0.2 and 1.8 μm. With increasing impact height (applied mechanical energy), a remarkable increase in generated electric voltage and energy was observed. As a result, the present composite is a better lead-free alternative for piezo-sensing/detection and energy harvesting applications.

Improved discharge energy density and efficiency of polypropylene-based dielectric nanocomposites utilizing BaTiO3@TiO2 nanoparticles

With increased requirements from the miniaturization, lightweight and integration of electronic devices, it is urgent to improve the discharge energy density (Ue) of commercial polypropylene (PP) film capacitor. In this work, core-shell structure BaTiO3@TiO2 nanoparticles were introduced into polypropylene matrix via melt mixing method. Due to the existence of the transition layer, the addition of BaTiO3@TiO2 nanoparticles can increase the interfacial polarization of the composites without causing obvious local electric field concentration in comparison with bare BaTiO3 nanoparticles. Moreover, BaTiO3@TiO2 nanoparticles can act as an electron trap to inhibit the movement of carriers and hinder the growth of the electrical tree, thereby promoting the breakdown strength (Eb) of PP-based nanocomposites. As a result, the Ue of the nanocomposite with 6 wt% BaTiO3@TiO2 nanoparticles was improved from 4.28 J/cm3 of pure PP to 5.58 J/cm3, maintaining a high efficiency of more than 95%. This study provides an effective strategy to optimize energy storage density of PP film capacitors.

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.

Morphological, Mechanical and Gas Penetration Properties of Elastomer Composites with Hybrid Fillers.

Ethylene–propylene–diene monomer (EPDM)-based composites including four different types of graphene nanoplatelets (GnPs) were prepared to evaluate the size effects of GnPs in terms of both specific surface area and lateral size on the morphological, mechanical, and viscoelastic properties, swelling ratio, crosslink density, and oxygen permeability. EPDM-based hybrid composites with GnPs and carbon black (CB) fillers were prepared, with the concentrations of 20 and 50 phr of CB and GnPs up to 7 phr. All samples were prepared using the melt mixing method, followed by compression molding. The specific surface area of GnPs is a more important key factor for mechanical and viscoelastic properties than its lateral size. The presence of GnPs leads to a decrease in the swelling ratio and oxygen permeability of the matrix while an increase in the crosslinking density. For a given specific surface area of GnPs (170 m2/g) and the same thickness (5 nm), the optimum lateral size for mechanical properties, swelling ratio, and crosslinking density is about 30 µm. There is a distinct synergic effect on the mentioned properties when hybrid fillers are used. For hybrid composites, the optimum total and each filler concentration are found to be important for achieving the best performance in terms of mechanical properties, swelling ratio, and crosslink density.

Anchoring carbon nanotubes to boron nitride microrods for enhancing the thermal conductivity of polystyrene

The development of high-performance thermally conductive fillers is crucial for the thermal management of polymer-based composites. Herein, a facile precursor pyrolysis strategy was adopted to fabricate boron nitride@multiwalled carbon nanotubes (BN@MWCNTs) fillers, wherein uniformly distributed MWCNTs were firmly anchored on BN microrods. Benefiting from the unique structure, the BN@MWCNTs act as fillers in the design of polystyrene (PS)/BN@MWCNTs composites via in situ polymerization. As a result, a 7.74-fold higher thermal conductivity (TC) (9.55 W/m·K) was achieved for the 10 wt% BN@MWCNTs, as compared to native PS/BN/MWCNTs prepared by the conventional melt-mixing method. More importantly, the PS/BN@MWCNTs composites exhibited satisfactory electrical insulation owing to the isolation effect of BN. Overall, this work provides a promising frontier for the design of polymer-based thermally conducting materials for applications in thermal management.

Influence of basalt fiber and maleic anhydride on the mechanical and thermal properties of polypropylene

AbstractNatural mineral fiber basalt has excellent thermal and mechanical characteristics. The current research focuses on evaluating the mechanical and thermal characteristics of polypropylene (PP) composites reinforced with short‐length basalt fibers (BF) fabricated by the melt mixing method. Maleic anhydride (MAH) at 3 wt% was used as a compatibilizer for fabricating the composites. The composite's mechanical, thermal, and morphological properties were investigated. The mechanical properties of the composites were enhanced with an increase in BF loadings from 10 to 40 wt% and beyond that it decreased. The chemical interaction between the fiber and the matrix was evaluated using Fourier transform infrared spectroscopy. Differential scanning calorimetry studies were used to determine the crystallization temperature, melting temperature and percent crystallinity of the composite. According to dynamic mechanical analysis, reinforcing PP with BF improved the damping property. Scanning electron microscopy revealed good interfacial interaction among the fiber and matrix and X‐ray diffraction was used to study the composite crystallinity.

Recycling Waste Nonmetallic Printed Circuit Boards for Polyvinyl Chloride Composites.

To reduce environmental threats, such as land filling, incineration and soil pollution, which are associated with the improper waste management of waste printed circuit boards, the utilization of NMPCBs from waste PCBs as a filler in composites was pursued. Untreated and treated NMPCBs in varying ratios, 10–30 wt.%, were blended with PVC to produce NMPCB/PVC composites, using the melt-mixing method via an internal mixer, in order to solve the remaining NMPCB waste problem after the valuable metals in PCBs were recovered. The incorporation of the NMPCB with PVC resulted in an increase in the tensile modulus and the thermal stability of the resulting composites. Scanning electron microscopy (SEM) results indicated improved interfacial adhesion between the treated NMPCB and the PVC matrix. The FTIR results of the NMPCB treated with 3-glycidyloxypropyltrimethoxysilane (GPTMS) revealed the formation of Si-O-Si bonds. The densities of the composites were found to increase with an increase in the content of the treated NMPCB, and compatibility improved. The tensile properties of the treated NMPCB/PVC composites were higher than those of the untreated NMPCB/PVC composites, suggesting improved compatibility between the treated NMPCB and PVC. The PVC composite with 10 wt.% of the treated NMPCB showed the optimum tensile properties. It was observed that the tensile modulus of the treated NMPCB/PVC composite increased by 47.65% when compared to that of the neat PVC. The maximum thermal degradation temperature was 27 °C higher than that of the neat PVC. Dynamic mechanical analysis results also support the improved interfacial adhesion as a result of the improvement in the storage modulus at the glassy region, and the loss factor (tan δ) peak shifted to a higher temperature range than that of the PVC and the untreated NMPCB/PVC composite. These studies reveal that the NMPCB was successfully modified with 1 wt.% of GPTMS, which promoted the dispersion and interfacial adhesion in the PVC matrix, resulting in better tensile properties and better thermal stability of the PVC composite.

Influence of surface modification of zinc oxide on physical properties of high density polyethylene

Inorganic nanofillers have sparked important research in the field of polymer nanocomposites because they can improve the properties of polymers. Hydrophobic ZnO nanoparticles modified by oleic acid (OA) were designed and prepared to accelerate the dispersion state of ZnO in the high viscosity polyethylene (HDPE), and enhance the performance of HDPE. HDPE/ZnO nanocomposites with different kinds and fractions of ZnO were further prepared via melt mixing method. The result showed the hexagonal and spindle-like ZnO nanoparticles with size distribution of 150–300 nm was acquired in the absence and presence of OA. Compared with surface untreated ZnO (U-ZnO), ZnO nanoparticles modified by OA (O-ZnO) can disperse evenly into HDPE at the fraction of O-ZnO below 5 wt%. TG data showed the presence of nanosized U-ZnO and O-ZnO in HDPE can significantly enhance the thermal stability of HDPE through raising the activation energy of HDPE in thermal decomposition process. The thermal decomposition order (n) for HDPE/ZnO nanocomposites was mostly bigger than that of HDPE, demonstrating the decomposition mechanism for HDPE became more complicated because of the addition of ZnO nanoparticles. DSC data showed U-ZnO nanoparticles cannot accelerate nucleation of HDPE and seemed to postpone the crystallization process, and O-ZnO nanoparticles was heterogeneous nucleating agent for HDPE. Moreover, the tensile and impact strength of HDPE was improved by the addition of O-ZnO, and connected with the dispersion state of ZnO nanoparticles in HDPE. The improvement in thermal stability, crystallization and mechanical properties by adding ZnO into HDPE matrix significantly enhance the potential of HDPE in food packaging, electronic packaging, drug and pharmaceutical bottles.

Study on Mechanical Properties of Banana Fiber-Reinforced Materials Poly (Lactic Acid) Composites

Synthetic materials reinforced with natural fibers are attracting great attention of scientists and researchers. Sustainability and eco-friendly nature along with easy availability and low cost are the key reasons. In this work, a natural fiber such as a banana fiber was investigated to create bioavailable materials while enhancing mechanical properties. The banana fiber was extracted from banana sheath by the mechanical method combined with chemical treatment with NaOH 1, 2, 3, 4, and 5%. Treatment of the banana fiber with NaOH effectively removes other impurities from the fiber surface and the fiber surface becomes rough, increasing the compatibility and bonding between banana fiber and PLA. The reported optimum NaOH concentration was 5% banana fiber used for the material polylactic acid (PLA) composite/banana fiber. The composites (BF) were prepared by the hot melt mixing method. The results showed that 20% by weight of banana fiber gave good results and the mechanical strength values kept at the specified level (tensile strength: 52.57 MPa, flexural strength: 70.35 MPa, impact strength: 155.45 J/m and hardness: 23.8 Hv). SEM observations showed visual evidence that surface impurities were removed from the fiber by NaOH treatment.

Solid dispersions of quercetin-PEG matrices: Miscibility prediction, preparation and characterization

Quercetin is a bioflavonoid compound with low water solubility in both foods and the gastrointestinal tract, which limits the exploitation of its health-promoting properties. This study aims to formulate solid dispersions (SDs) of quercetin with hydrophilic polyethylene glycol PEG matrices, using the melt-mixing method, to improve the dissolution and antioxidant activity of quercetin. Initially, the total Gibbs free energy for different binary mixtures was modelled to predict the miscibility of the compounds. Then, the physicochemical properties of the formulated SDs were characterised and dissolution tests and antioxidant activity measurements were performed in vitro to evaluate the improved profiles and antioxidant activity of the SDs developed. The group contribution methods of Hoy and Van Krevelen and Hoftyzer, used for PEG solubility parameter calculations, presented a suitable prediction of interaction and miscibility behaviour. The results suggested the presence of amorphous quercetin precipitates in the crystalline matrix of PEG 4000 and PEG 6000, and the formation of an amorphous SD between quercetin and PEG 1000. These formulations achieved good radical scavenging activity and better dissolution, especially the quercetin-PEG 1000 SDs.

Multiwalled Carbon Nanotube-Coated Poly-Methyl Methacrylate Dispersed Thermoplastic Polyurethane Composites for Pressure-Sensitive Applications

Thermoplastic polyurethane (TPU) is a widely used polymer for a variety of pressure sensing applications because of its softness and shape memory. This work reports the synthesis of novel TPU-based three-dimensional structured (3D) pressure-sensitive composites via the melt mixing method. Poly-methyl methacrylate (PMMA) microbeads of different sizes (5, 10, and 20 µm) were first coated with multi-walled carbon nanotubes (MWCNT) and then incorporated into the TPU matrix for achieving an early electro conductive percolation threshold compared to without PMMA beads. The addition of MWCNT coated PMMA beads reduced the TPU insulated areas by creating a 3D conductive network that finally reflected the early percolation threshold during external pressure. Raman microscopy and XRD results confirmed the MWCNT coated nicely on the surface of PMMA beads. The pressure sensitivity results also confirmed the decrease in resistance of the composites with the increase in the applied external pressure. Composites with 10 µm PMMA bead size showed the most linear responses to the decrease in resistance with increasing pressure and showed a higher strain gauge factor value (3.15) as compared to other composites, which had values of 2.78 and 2.42 for 20 and 5 µm, respectively. Microstructure analysis of the composites by SEM, capacitance, permeability, and thermal conductivity measurements was also investigated to support the above evidence. The results support the suitability of this novel composite as a potential candidate for pressure sensing applications.

Assessment of new composites containing polyamide-6 and lead monoxide as shields against ionizing photonic radiation based on computational and experimental methods

This study aimed to introduce new composites, containing polyamide-6 (PA6) and lead monoxide (PbO), to protect against ionizing photon sources used for diagnostic and therapeutic purposes. Five composites, containing various weight percentages of PbO filler (0, 5, 10, 20, and 50%), were developed in this study. Initially, the numerical attenuation value was estimated using the XMuDat program by calculating the mass attenuation coefficients at different energy levels. Next, the samples were synthesized based on the melt-mixing method in a laboratory mixing extruder. Their characteristics were also determined by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Finally, experimental radiation attenuation tests were carried out. Based on the SEM results, the acceptable filler weight percentage was up to 20%. However, substantial aggregates were formed at the highest weight percentage. The results of XRD analysis showed a higher tendency for crystallization by decreasing the amorphous area while increasing the filler weight percentage. Moreover, the mass loss rate was monitored at different temperatures, revealing that the filler incorporation improved the thermal durability of the samples. The radiation results showed a good agreement between the experimental and computational data, except when aggregates formation was substantial. The experimental data revealed that when the lead weight percentage increased from 0% (crude PA6) to 50%, the half-value layer decreased from 3.13 to 0.17 cm at an energy level of 59 keV and from 7.28 to 4.97 cm at an energy level of 662 keV. Following the studied mechanism, the superiority of lead/polyamide composites can be found in the high adsorption of photon radiation at low energies (E < 0.20 MeV) and significant attenuation at medium and higher energies. Considering these promising results, the shielding properties of these composites can be further analyzed via more practical investigations.

Structural, thermal, and viscoelastic response of nanoclay reinforced polylactic acid/thermoplastic polyurethane shape‐memory nanocomposites of low transition temperature

AbstractShape memory polymers are strong competitors against shape memory alloys in many similar applications due to their inherent properties. Numerous studies have already reported shape memory properties of pure and blended polymer systems. However, further research is required to address property–structure interplays in nano‐reinforced shape memory composites of low programming temperature with specialty applications including wearing smart cloths, advanced medical devices and biomedical shape memory scaffolds. This research aims to evaluate the overall interplay amongst thermal, structural and viscoelastic properties of nanoclay reinforced polylactic acid (PLA)/thermoplastic polyurethane (TPU) shape memory blends whilst the use of a plasticizer is hypothesized to modify the programming temperature of the fabricated parts. To achieve this, the melt mixing method was utilized in fabrication of nanoclay filled PLA/TPU blends of 60/40 ratio as the optimized reference system. Polyethylene glycol (PEG) was used to reduce the stimulation temperature down to around 42°C. The results showed that the optimal thermal, structural and shape memory properties are obtained when 5 wt% of nanoclay and 10 wt% of PEG are incorporated into the reference blend exhibiting the targeted stimulus temperature as supported by the thermal, structural and shape memory response of the parts. The contact angles, surface energy values and transmission electron microscopy analysis further confirmed the improvement in the miscibility of PLA/TPU blends correlated to the overall shape memory response of the fabricated parts.