The effects of thermally induced residual stresses on the mechanical, thermomechanical, and morphological properties of recycled polyethylene terephthalate (rPET) were systematically investigated. Specimens were subjected to free quenching at controlled bath temperatures (0, 10, 20, and 30°C) and compared against an annealed reference. Quenching at 20°C was identified as the optimal condition, maximizing Izod impact strength ( 8.7 kJ/m2) and elongation at break ( 5.1

Researchers investigated into how thickness and quenching temperature affect the mechanical and thermomechanical properties of titanium dioxide-pigmented polycarbonate. By using compression molding, specimens free of morphological effects have been generated. Dynamic mechanical analysis was used to evaluate plates with thicknesses of 0.6, 1, 2, and 3 mm under flexion, Izod impact strength, density, and tensile testing. Two distinct heat treatments annealing and second quenching were applied. The results indicate that a second quenching at 40°C for samples 3 mm thick and 35°C for samples 2 mm thick can enhance the impact strength and elongation at break, and a relationship between the mechanical, physical, and thermomechanical properties is detected. At the expense of other characteristics like elastic modulus, density, and yield stress, these properties are improved. A relaxation mode about 30°C is associated with improved impact strength and elongation at break following the second quench.

This study demonstrates that quenching and annealing significantly influence the mechanical and thermophysical behavior of low density polyethylene (LDPE). Rapid quenching at temperature of –25 °C enhances ductility by increasing elongation at break, despite reducing thermophysical properties, likely due to microstructural refinement. In contrast, post-quenching annealing especially at 100 °C improves thermal conductivity and crystallinity but reduces ductility. The results underscore a tunable balance between thermal and mechanical performance, governed by the interplay of beta (β-) and alpha (α-) relaxation modes during heat treatment. Post-quenching annealing of low density polyethylene LDPE, particularly at 100 °C, significantly enhanced thermal conductivity, diffusivity, and crystallinity, albeit with a trade-off in ductility and increased brittleness. Quenching within the beta (β-) relaxation range promoted maximum ductility, while annealing in the alpha (α-) relaxation range improved thermophysical properties. These findings reveal that precise control of heat treatment conditions enables a tunable balance between mechanical flexibility and thermophysical performance in LDPE

This research investigated the impact of citric acid treatment on the adhesive properties of a composite material based on a poly-lactic acid matrix and Ampelodesma mauritanica fibers. Citric acid, a natural and biodegradable compound, was chosen as a more environmentally friendly alternative to the alkaline treatments traditionally used. Using a palatograph, biocomposite samples with a weight percentage of 20 % fiber were produced. Characterization was carried out using different methods such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) techniques, were used to examine the treated and untreated fiber samples. Citric acid treatment led to a reduction in the quantities of hemicellulose, lignin and wax. This observation is confirmed by the disappearance or attenuation of absorption bands at 1650 and 1731 cm-1 in the spectra. In addition, the treatments improved crystallinity, thermal stability and surface roughness of Diss (Ampelodesma mauritanica) fibers. Furthermore, Polylactic acid composites reinforced with medium-length Diss fibers were subjected to mechanical tests (Izod impact strength, tensile strength and elongation at repture), were used to characterize Poly-lactic acid composites reinforced with natural Diss (Ampelodesma mauritanica) fibers. In contrast with untreated composites, the mechanical properties of treated composites showed an increase in the modulus of elasticity, tensile strength, and elongation at repture, with values of 4.680 GPa, 48.90 MPa, and 2.52 %, respectively. Scanning electron microscopy assessments of treated composites also confirmed these findings.

This study developed a polypropylene (PP) composite with enhanced thermal and mechanical properties by combining natural Luffa aegyptiaca fibers and alumina (Al2O3) fillers. Individual PP/Luffa and PP/alumina composites were also prepared for comparison. Luffa fibers were treated with NaOH and stearic acid, and alumina was coated with stearic acid to improve compatibility with the PP matrix. Composites with 2

We use an ab-initio approach to analyze the structural, electronic band structure, and thermoelectric properties of titanium dioxide (TiO2 in rutile phase), and we then use rutile-TiO2 nanoparticles to determine its effects on sol-gel-produced polyvinyl alcohol/silicon dioxide (PVA/SiO2) hybrid films. The synthesis of hybrid films involved the incorporation of 1 % rutile-TiO2 nanoparticles in the PVA/SiO2 matrix. The thermoelectric properties of the resulting hybrid films were characterized by Seebeck coefficient measurements, as well as electrical and thermal conductivities. The synthesis of PVA/SiO2/Nano-TiO2 films was accomplished with success. The chemical bonds have amply demonstrated that the PVA backbone is connected to the (SiO2-TiO2) network. TGA testing indicates that hybrid films are more resistant to higher temperatures than pure PVA films. SiO2 nanoparticles reveal more effective loading to improve dielectric characteristics compared to TiO2. The best results are obtained in cases of mechanical, thermal and electrical insulation when both nanofillers are integrated into the polymer matrix. The findings show that the thermoelectric performance of PVA/SiO2 hybrid films is improved by the addition of (1%) rutile-TiO2 nanoparticles in the rutile phase. This study provides insights into the potential applications of rutile-TiO2 nanoparticles in enhancing the thermoelectric properties of hybrid materials and opens up avenues for further research in this area, and contributes to the growing body of knowledge on enhancing the thermoelectric properties of materials by incorporating rutile-TiO2 nanoparticles into hybrid films synthesized by the sol-gel method.

The thermal behavior of a poly(methylmethacrylate) (PMMA) pigmented with titanium dioxide (TiO2) is studied in both Steady state and transient regimes in the present work. The numerical results of thermal conductivity, based on the finite element method, are compared to theoretical models and experimental measurements, which varies depending on the quenching temperature and pigment content. Time evolution of temperatures during the quenching of the composite is taken into account for different quenching temperatures and different pigment contents. It is noted that the heat exchange becomes slower for a pigment fraction of 0.5

Abstract We use an ab initio approach to look into the structural, electronic band structure, and thermoelectric properties of titanium dioxide (TiO2 in rutile phase), and we then use TiO2 to create its effects on sol-gel-produced polyvinyl alcohol/silicon dioxide (PVA/SiO2) hybrid films. The synthesis of the hybrid films involved the incorporation of 1% TiO2 nanoparticles in the PVA/SiO2 matrix. The thermoelectric properties of the resulting hybrid films were characterized through measurements of the Seebeck coefficient, electrical conductivity, and thermal conductivity. The findings show that the thermoelectric performance of the PVA/SiO2 hybrid films is greatly improved by TiO2 nanoparticles are added to the rutile phase, with an optimal concentration (1%) of TiO2 nanoparticles. This study provides insights into the potential applications of TiO2 nanoparticles in enhancing the thermoelectric properties of hybrid materials and opens up avenues for further research in this area, and contributes to the growing body of knowledge on enhancing the thermoelectric properties of materials by incorporating TiO2 nanoparticles into hybrid films synthesized by the sol-gel method.

In this paper, parameters that effectively contribute to glass surface degradation from sandblasting erosion processes are investigated and optimized on the basis of the method of Taguchi. The polystyrene glass used in this work has been eroded taking into account the projected sand mass, the particles’ grain size and the velocity as the main influencing parameters by looking at specimens’ surface roughness (SR) and optical transmission (OT). Taguchi’s Design L9 orthogonal array of experiments has been implemented in order to obtaining the best combination among these parameters. The significant parameters affecting the responses have been determined on the basis of variance analysis. These have revealed that the particles’ size and velocity are the most effective parameters on the responses OT and SR of the degraded surface with 92 and 56% contribution, respectively. These optimized influential parameters’ combinations have revealed severe eroding processes occurring to the polystyrene glass surface as confirmed by the optical micrographs.

Three different compatibilizers were used; namely: Fusabond (FSB) which is a maleic anhydride grafted polyethylene, montanic acid (E wax), and used engine oil (UEO) were incorporated into cellulose acetate/low density polyethylene (CA/LDPE) composites at three fiber contents: 5, 15 and 30 phr. Three series of samples consisting of treated composites using coupling agents were prepared, while one group was left untreated as a reference composite. To assess the performance of the composites, different testing techniques were used. These include attenuated total reflectance spectroscopy(FTIR-ATR), thermogravimetric analysis(TGA), differential scanning calorimetry(DSC), tensile test, dynamic mechanical thermal analysis(DMTA), and scanning electron microscopy(SEM). The presence of ethylene vinyl acetate (EVA) in LDPE enhanced the adhesion at the polymer/fiber interface, as reflected by the increase of Young’s modulus by 75, 166, and 245% respectively compared to neat LDPE, an increase of the storage modulus and a reduction of the damping factor value. Incorporating Fusabond was also found to affect slightly the mechanical properties with high fiber contents compared to the composites without the coupling agent by 13%. On the other hand, the use of montanic acid and used engine oil affected the cellulose acetate fibers distribution within the matrix. The UEO enhanced the dispersion but acted as a plasticizer resulting in a slight reduction of the crystallinity. Moreover, the interaction between the LDPE matrix and the CA fibres was indicated by the resulting fracture surface morphology. The results obtained suggest that the CA/LDPE composites would be suitable for packaging or used in automotive applications.

Southern Algeria is characterized by a harsh climate due to erosion by sandstorms. The characteristics of poly (methyl methacrylate) (PMMA) allow it to replace mineral glasses and improve its performance. The surfaces of eroded PMMA objects have altered optical and mechanical properties. The purpose of this study is to improve the hardness and erosion resistance of PMMA by the annealing and quenching process. The PMMA samples before being eroded at different impact angles were treated by two different heat treatments; namely: an annealing which represents the reference state followed by a quenching from T g + 15 °C to different temperatures below T g . Erosion resistance was found to be improved by the quenching process and contributing to the increase in optical transmission of PMMA samples tested at different impact angles. The most pronounced effect of quenching was observed for the impact angle 45° at a temperature of 20 °C by inducing the improvement of Vickers hardness (21.8 HV) which can be linked to the relaxation mode β around this temperature.

This work is focused on the preparation and characterization of poly (vinyl alcohol)/silica gel/Nano-TiO 2 , and the study of titanium dioxide (TiO 2 ) nanoparticles (from 1 to 5%) on the properties of poly (vinyl alcohol) (PVA)/silica films. This new material was prepared by the sol-gel method using poly (vinyl alcohol) powder with Tetraethyl Orthosilicate (TEOS) as a precursor source of silica. TEOS was hydrolyzed and condensed in water and ethanol in the presence of hydrochloric acid (HCl) used as a catalyst. Fourier transform infrared (FT-IR), water absorption, water contact angle, ultraviolet-visible spectrometry (UV-VIS), and thermogravimetric analysis (TGA) were used to characterize the hybrid films obtained. The PVA/SiO 2 /Nano-TiO 2 films were successfully synthesized. Owing to the FT-IR Analysis, the chemical bonds have clearly shown that the PVA backbone is linked to the (SiO 2 -TiO 2 ) network. UV-VIS tests indicated that the hybrid films' UV shielding properties were drastically enhanced as a result of the addition of TiO 2 . According to the TGA tests, the hybrid films are more heat tolerant than neat PVA films. The water contact angle results revealed that TiO 2 nanoparticles used as a doping compound possess an important influence on the hydrophilicity of PVA/SiO 2 as thin films. The film's water resistance has also been enhanced.

Polycarbonate is a tough, amorphous and transparent high performance thermoplastic polymer. It is used in many fields of application due to its versatile thermophysical, mechanical and optical properties. However, one of its drawbacks is its relatively high thermal conductivity which prevents its application as an insulating material. An appropriate heat treatment can therefore be a useful route to improve the thermal insulating property. The objective of this work is to study the effect of heat treatment; namely the influence of the quenching temperature above and below the glass transition temperature (Tg) on the thermophysical properties of neat polycarbonate (PC). The effect of the quenching temperature above Tg was also studied for neat poly (methyl methacrylate) (PMMA). The effect of residual stresses (RS) generated by the free quenching process on the thermophysical properties of neat PC was investigated. The thermal conductivity (k) and thermal diffusivity (a) of neat PC were measured using a periodic measurement method (DICO), (DIffusivity and COnductivity), at room temperature. The DICO method developed in the CERTES laboratory (Center for Studies and Research in Thermal, Environment and Systems of Paris 12 University), allows simultaneous access to the conductivity and thermal diffusivity from which the specific heat (Cp) can then be deduced. This work showed that the quenching from a high temperature above Tg did not affect the thermal conductivity and thermal diffusivity of both PC and PMMA. However, quenching from a temperature below Tg (130 ° C) caused a decrease of both the thermal. In fact the thermal conductivity of PC annealed at 130 ° C which is 0.22 W. m -1 .K -1 decreased to 0.06 W. m -1 .K -1 and 0.14 W. m -1 .K -1 after quenching at 0° C and 40 ° C respectively. This means that quenching would therefore improve the insulating capacity of PC compared to the material which has undergone only annealing. Contrary to the thermal conductivity, the values of the specific heat capacity in this temperature range ( 0° C – 40° C) significantly increased as a result of quenching. They increase from 1118 J. kg -1 . K -1 for the annealed sample to 1290 J. kg -1 . K -1 for PC quenched at 0° C and increased to 2221 J. kg -1 . K -1 for PC quenched at 40 ° C which corresponds to an increase by 98 %. It was also found that the values of thermal conductivity and specific heat were in good agreement with those reported in the literature for neat PC samples quenched below Tg.

This work presents the chemical modification of Spanish broom flour (SBF), and the study of SBF loading and surface treatment on the performances of polypropylene (PP) biocomposites. In order to enhance the interfacial interactions between the PP matrix and the SBF, two types of chemical treatments were used: 2 wt% of sodium hydroxide (NaOH) for different times (8, 24 and 48 h) and 5 wt% of vinyltrimethoxysilane (VTMS), respectively. Different techniques for characterization such as the melting flow index (MFI), X-ray diffraction, transient plane source (TPS) and water absorption were used. The experiment results showed a decrease of the MFI with increasing of modified SBF content, independently of the type of the chemical treatment. Moreover, this decrease became significant in the biocomposites containing SBF-VTMS. The X-ray patterns showed that surface treatment of SBF could improve their crystallinity and crystallite sizes. The TPS measurements illustrates that the thermal conductivity of the biocomposites decreases with 10 wt% of modified SBF loading. Higher content than 20 wt% of SBF, improved the thermal conductivity of the biocomposites. Meanwhile, the lowest values were found when the VTMS is used. Besides, it was accompanied by a decrease in absorptivity due to the better interfacial adhesion SBF-PP.

In this study, the effect of paraffin (PR) and copper (Cu) incorporation in polycarbonate (PC) was investigated using differential scanning calorimetry (DSC). The effect of PR incorporation in PC was investigated using thermogravimetric analysis (TGA). The effect of thermal treatments on thermophysical properties was studied in PC/PR and PC/Cu composites by using the hot-disk method and a periodic method (DICO). Specimens were heated at 160 degrees C (T-g +15 degrees C), then two different cooling methods were employed: furnace cooling (annealing) and water cooling (quenching) at 0 degrees C and 35 degrees C. The DSC results showed that a solid-liquid transition occurred in all PR formulations, as well as showed the plasticizing role of the PR additive. Thermal stability decreased with the addition of PR. Thermal conductivities (lambda) increased with increasing Cu content and decreased with PR additive content, and the annealed samples showed a higher thermal conductivity (lambda) than quenched ones. Meanwhile, a small difference between the thermal conductivity of the DICO samples and the hot-disk samples was noticed.

Studying the effect of quenching from the melt state on the structure and impact resistance of Isotactic polypropylene (iPP) was the major aim of this work. Various tests were applied to confirm changes that occur to iPP, namely impact tests, WAXD, FTIR, and the density. The quenching from the melt state to different temperatures decreased the values of Izod impact strength for all the quenching temperatures. The FTIR result showed a decrease in the crystallinity of the polymer at the free quenching temperature of 20 degrees C. The X-ray diffraction study revealed that the structure dominates the main morphology of iPP.

ABSTRACT The removal of methylene blue (MB) from aqueous solutions using sulfuric acid modified Cupressus semperirens cones (H2SO4-CSC), was investigated. Results showed that a pH value of 12 was favorable for the adsorption of MB and that the moisture and ash yields are suitable for industrial exploitation. A high porosity value was found, 68.1%. In agreement with its low content of basicity compared to its acidity, the H2SO4-CSC absorbent had an acidic behavior. Rate constants of pseudo-first-order, pseudo-second-order, and nth kinetic model were determined to analyze the dynamic of the biosorption process; they showed that adsorption kinetics followed a pseudo-second-order and nth kinetic models. Ionic strength was shown to have a negative impact on the biosorption of MB onto H2SO4-CSC. The Sips isotherm model was found to be the most relevant to describe MB biosorption onto H2SO4-CSC with a correlation factor R2 > 0.999. The biosorption capacity of H2SO4-CSC was found to be 460 mg g−1 at 10°C and 590 mg g−1 at 25°C, confirming biosorbent efficiency for the removal of MB dye from aqueous solutions. Thermodynamic parameters indicated that the biosorption process of MB was endothermic and more effective at high temperatures. The values of ΔG° and ΔH° confirmed that the biosorption of MB onto H2SO4-CSC was spontaneous and endothermic in nature. An irregular increase in randomness at the H2SO4-CSC–solution interface during the biosorption process was suggested by the positive values of ΔS°.

In this study, the effects of free quenching on mechanical physical and thermal behaviours of high density Polyethylene (PEHD) have been investigated. Three different thermal treatments were used: A first free quenching from the melt state to air, a second free quenching from 130°C to different temperatures and finally an annealing .The results have shown that an improvement of the impact strength and elongation at break can be obtained after a first quenching to air. However, a second quenching at 0°C gives better results and a correlation between the mechanical and thermal properties is observed. The improvement of these properties is obtained to the detriment of other properties like elasticity modulus, density, vicat softening temperature (VST) and heat distortion temperature (HDT). The improvement of impact strength and elongation at break after the second quenching is probably linked to the existence of a relaxation mode located around this temperature. Keywords : free quenching; polyethylene, mechanical, physical, thermal. DOI : 10.7176/CPER/59-03

In this study, the effects of the free quenching temperature on mechanical, thermomechanical and thermophysical properties of pigmented polystyrene (PS/TiO2) with 3% of TiO2 were investigated. Thermal conductivity and thermal diffusivity of the titanium dioxide pigmented polystyrene were measured using a periodic method. The results show a slow improvement of the notched Izod impact strength obtained after a second quenching at 15 and 35°C; whereas thermal conductivity and diffusivity reached a minimum value at the quenching temperature of 35°C. However, the effect on the thermophysical properties is only noted for the second quenching temperature 35°C. The study allowed examining the effect of quenching temperature, filler concentration and material thickness on the transient thermal behavior of the titanium dioxide pigmented polystyrene.