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Abstract Surfactant chemistry can affect the phenolic foam (PF) properties by controlling the collision and combination of the created bubbles during foam production. The study was accomplished using two surfactant families, nonionic: polysorbate (Tween80) and anionic: sodium and ammonium lauryl sulfates (SLS30 and ALS70) and sodium laureth sulfate (SLES270) to manufacture PF foams. Tween80 and SLS30 resulted in foams with the lowest and highest densities, 20.2 ± 0.2 and 42.72 ± 0.4 kg/m3, respectively. All the surfactants created an open-cell morphology, except Tween80 with a semi-open-cell structure consisting of large cells and thicker cell wall thickness. The anionic surfactant had better performance, the foams made by SLS30 had cells with diameters of 338.5 ± 18.5 and cell density of 2.5 cell/mm3 × 105. While the SLES270 made foam with the highest cell density and the smallest cell size that caused higher compressive strength. The SLES270 led to keeping the foam flexibility even under the fire exposition, and it increased the thermal insulation by 50% while the other samples were turned into fragile foam. A higher level of polarity in SLES270 caused better micelle production and then better bubble formation, followed by the bubble coalition.

This study examines the efficacy of decision tree and AdaBoost algorithms in predicting mechanical and fracture parameters of polypropylene nanocomposites toughened with ethylene-based and propylene-based thermoplastic elastomers and reinforced with fumed silica and halloysite nanotube nanoparticles. The essential work of the fracture approach was utilized to study the fracture parameters, including elastic and plastic works of the blended polymer nanocomposites. The data were divided into 80 % for training and 20 % for testing. AdaBoost consistently achieved superior performance compared to the decision tree model in all variables throughout both the training and testing stages. During the testing phase, the AdaBoost model obtained R2 values of 0.90 for Young's modulus, 0.93 for elongation at break, 0.87 for tensile strength, 0.86 for plastic work, and 0.60 for elastic work. Also, the mean absolute percentage error for the AdaBoost model during the test phase was 3.10 % for Young's modulus, 3.25 % for tensile strength, 10.34 % for elastic work, 13.55 % for plastic work, and 24.78 % for elongation at break. Furthermore, a sensitivity analysis examining the effects of various features such as TPO type, nanoparticles, and nanoparticle type on mechanical properties reveals that TPO has the most significant overall influence. The results also include an analysis of the impact of the key features on each mechanical property based on the sensitivity analysis.

Abstract Rigid polylactic acid (PLA) foams fabricated via thermally induced phase separation (TIPS) utilizing a ternary solution of PLA, Tetrahydrofuran (THF), and water. The PLA gels were stabilized mechanically by the substituting of the THF/water solvent mixture with ethanol as non-solvent and subsequently vacuum dried. A comprehensive characterization of PLA foams was achieved by Scanning Electron Microscopy (SEM), X-ray Diffractometry (XRD) and Brunauer–Emmett–Teller (BET) analyses. The BET area obtained in the PLA foam is up to 18.76 m2/g. The Response Surface Methodology (RSM) was utilized to assess the impacts of four independent variables (polymer concentration, solvent composition, quench temperature, and aging time) on the pore size and density of PLA foam. The experimental findings demonstrated that the fabrication parameters could be fine-tuned to govern the morphology of the pores, comprising their size and density. The optimal values of parameters for cell size were identified by RSM to be 8.96 (wt%), 91.60 (w/w), 5.50 °C, and 3.86 h for the optimum cell size of 37.96 µm (37.78 by Genetic Algorithm). Optimum density by RSM 88.88 mgr/cm3 (88.38 mgr/cm3 by Genetic Algorithm) was obtained at 5.00 (wt%), 89.33 (w/w), 14.40 °C and 2.65 h.

Abstract Nano-silicon carbide (SiC) as a high thermal conductive material with an intrinsic thermal conductivity of ~ 490 W/m K was used to improve the cure characteristics, kinetics, and thermodynamics of curing reaction of styrene-butadiene rubber/butadiene rubber (SBR/BR) compounds. The considerations were carried out by non-isothermal differential scanning calorimetry (DSC). Results revealed that the presence of SiC shifted the peak and end temperatures of the curing peak to lower temperatures. The calculated activation energy of the curing reaction based on the Kissinger approach showed a descent from 409.8 to 93.8 kJ/mol by adding SiC from 0 to 7.5 phr (part per hundred rubber). Moreover, the obtained Gibbs free energy variation and equilibrium constant of the curing reaction proved that the reaction was absolutely forced and irreversible, which can be increasingly characterized as a one-way process. According to the results, SiC accelerated the curing reaction because of the increment of heat transfer into the compound. This phenomenon caused the increment of enthalpy variation of the vulcanization reaction, particularly at the SiC content of 5 phr. The achieved kinetic parameters via fitting an autocatalytic model based on the Sestàk–Berggren model by the Màlek method to describe the kinetics of the curing reaction indicated that the SiC filler had a catalytic effect on the curing reaction of SBR/BR-SiC, particularly after 2.5 phr of the filler.

The impacts of nano-alumina (NA) as a filler and the manufacturing methods of Dunlop and air microbubbling on the physical, microstructural and mechanical properties of natural rubber latex foam (NRLF) were comprehensively investigated. The achieved crosslink density through the swelling method using the Flory–Rehner equation showed that the nano-alumina led to an increase in the crosslinking level in the foam. The foams prepared by the air microbubbling (BLF) had crosslink density 57–160% more than Dunlop (LF). Despite the fact that the nano-alumina enhanced the cell size and broadened their diameters probability distribution, the field-emission scanning electron microscopy illustrated that the air microbubbling resulted in the foams with 105% smaller cell size (0.113 mm) and 840% higher cell density (57.94·105 cell/mm3). In addition, the calculated specific tensile strength, modulus, toughness, and elongation at break proved that the metallic oxide filler of nano-alumina improved the tensile characteristics of the NRLF up to 60%. According to the results, adding 3 phr nano-alumina to the foam increased the compression recovery to 86 and 99.4% in the LF and BLF samples, respectively. Finally, the analysis of variance was performed to optimize the formulation of foams prepared by two manufacturing methods.

Ammonium polyphosphate (APP) was grafted onto the surface of exfoliated graphite nanoplatelet (GNP) to obtain a novel flame retardant, GNP-g-APP, and thereafter was incorporated into the ethylene vinyl acetate (EVA) to improve its flame retardancy. The chemical structures of the precursors and the target product were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and energy dispersive X-ray spectroscopy (EDS) techniques. FTIR spectra appeared at 1056 and 1103 cm−1 were attributed to POC asymmetric stretching bond, that conformed formation of GNP-g-APP. Thermal stability behaviour and flame retardancy performance of the samples were evaluated by TGA, UL-94, micro-calorimetry, and cone calorimetry. TGA measurements revealed the superiority of GNP-g-APP over GNP. The micro-calorimetry analyses indicated a sharp fall in both the total heat release (THR) and the peak of heat release rate (pHRR) of EVA containing 30 wt.% GNP-g-APP, evidenced by a thick char layer formed as barrier. Cone calorimetry confirmed flame-retardant effect of GNP-g-APP featured by a reduction in pHRR (−63 %) and THR (−31.6 %) due to the formation of a cohesive char layer. Although GNP addition sharply decreased the elongation at break of 70/30 (w/w) composites from 500% for neat EVA to 71%, a very promising value of 364% for EVA/GNP-g-APP sample preserved superior flexibility.

Background: Education of the patients with Coronavirus Disease 2019 (COVID-19) and their families is necessary to improve the quality of life. This study investigated the effect of person and family-centered training via telenursing on the quality of life in patients with COVID-19. Methods: This interventional study was performed on 88 patients with COVID-19 18--65 years and 44 family members referred to the Bank Melli Hospital, Tehran, Iran. The samples were randomly assigned into two groups person-centered and family centered. A cyberspace group including patients and their families was created. Four educational sessions planned (15--30-min-every day) and three sessions planned for completing the questionnaires via phone. The data were collected using demographic characteristics form and the 12-item Short-Form Health Survey version 2 before and 6 weeks after the intervention and were analyzed in SPSS 22 using Chi-square test, paired t-test, and independent t-test. Results: The mean scores of quality-of-life increased significantly in the person-centered group from 26.81 ± 5.15 to 34.4 ± 4.39 before and six weeks after intervention, respectively (p < 0.001). The means scores of quality-of-life increased significantly in the family-centered group from 28.11 ± 4.79 to 35.86 ± 3.85 before and 6 weeks after the intervention, respectively. (p < 0.001). Conclusions: The person and family centered methods increase the mean scores of quality-of-life of patients with COVID-19. The family centered method can be more effective to improve the quality of life of these patients.

The aim of this study was to investigate the flexural behavior of engineered cementitious composites (ECCs) reinforced by cellulose pulp (CP) and cellulose microfibers (CMF). The reinforcements were obtained from chemical-mechanical treatments of Kraft paper and used in ECC mix design. Results showed that cement reinforced by CP exhibited a strain-hardening behavior in the three-point bending test, while CMF led to a brittle behavior in cement composites. Moreover, different hybrid combinations of polyvinyl alcohol (PVA) and CMF achieved quite a high strength while maintaining a high level of flexural toughness. A combination of 0.5 vol% CMF and 1.5 vol% PVA resulted in a significant increase in flexural toughness and a slight improvement in flexural strength. The properties of this hybrid composite were comparable with one containing 2 vol% of PVA fiber.

The leading purpose of this work was to broaden the current knowledge about the impacts of various chain configurations of polypropylene (PP), i.e., linear and branched form, on the thermal properties (thermal stability, thermal conductivity, crystallinity, thermal mechanical properties) of PP nanocomposites reinforced by graphene nanoplatelet (GnP) particles. The utilization of GnP with different particle size gave us good information about the impacts of filler's dimension on the thermal properties as well. Regardless of the PP type, EC1500-filled (small size GnP) composites showed higher storage modulus in the dynamic mechanical analysis. With respect to DSC results, incorporation of GnP, particularly GnP with smaller particles, led to a striking increment in crystallization temperature and crystallinity, and nucleating efficiency of GnP in linear PP-based composites was higher. The employment of GnP brought about an improvement in degradation temperature and thermal stability of nanocomposites, and smaller GnP was more effective in this context. However, due to its higher aspect ratio, EC100 GnP (large size GnP) could enhance thermal conductivity more satisfactory, specifically in linear PP-based samples. Keywords: Polypropylene, Graphene nanoplatelet, Nanocomposites, Thermal properties, Dynamic mechanical analysis, Thermal conductivity, DSC