The effect of organoclay addition on the properties of an acrylate based, thermally activated shape memory polymer

Shape Memory Polymers (SMPs) exhibit the intriguing ability to change back from an intermediate, deformed shape back to their original, permanent shape. In this contribution a systematic series of t-butylacrylate-co-poly(ethyleneglycol) dimethacrylate (tBA-co-PEGDMA) polymers have been synthesised and characterised prior to incorporation of organoclay. Increasing the poly(ethyleneglycol) dimethacrylate (PEGDMA) content in increments of 10% increased the storage modulus from 2005 to 2250 MPa, reduced the glass transition temperature from + 41 to − 26 °C and reduced the intensity of the associated tan δ peak. The tBA-co-PEGDMA crosslinked networks displayed useful shape memory properties up to PEGDMA contents of 40%. Above this PEGDMA percentage the materials were prone to fracture and too brittle for a realistic assessment of their shape memory capability. The system containing 90% t-butylacrylate (tBA) and 10% PEGDMA was selected as the host matrix to investigate how the incorporation of 1 to 5 mass% of a benzyl tallow dimethylammonium-exchanged bentonite (BTDB) influenced the shape memory properties. X-ray diffraction data confirmed that BTDB formed a microcomposite in the selected matrix and exerted no influence on the storage modulus, rubbery modulus, glass transition temperature, Tg, or the shape or intensity of the tan δ peak of the host matrix. Therefore, it was anticipated that the presence of BTDB would have no effect, positive or negative, nor on the shape memory properties of the host matrix. However, it was found that the incorporation of clay, especially at the 1 mass% level, significantly accelerated the speed, compared with the clay-free SMP, at which the microcomposite returned to the original, permanent shape. This accelerated return to the permanent shape was also observed when the microcomposite was coated onto a 100 μm PET film

Risk assessment of irrigation with water contaminated by trace metals on the soil-plant complex in the El Madher plain, north-east Algeria

Polluted water poses significant health risks when it is part of the water sources used for irrigation, leading to the contamination of soil and plants by various pollutants. This work aims, firstly, to assess the degree of pollution of Wadi El Gourzi water (Batna, Algeria), and then to verify the consequences on their use for the irrigation of market garden plants for everyday consumption (lettuce, cilantro, parsley and spinach), both in the aerial part (stems and leaves) and in the soil where they are grown. This study focuses on trace metals (Cr, Pb, Zn and Cd). Soil pollution was assessed by calculating the soil pollution index (PI), while the uptake of these elements by plants was monitored by the transfer factor (TF). The analyses of the Wadi El Gourzi water with the flame atomic absorption spectrophotometer (FAAS) show a maximum abnormal concentration of Cr (17.37 mg∙dm-3), Pb (0.71 mg∙dm-3) and Cd (0.45 mg∙dm-3). For the analysis of the soils irrigated by these waters, the results of the PI show that the soils used for the cultivation of parsley and lettuce are polluted by several metals (PI > 1). The concentrations of trace metals elements (TMEs) in the sampled plants show a significant accumulation of Zn, Cd, Pb and Cr by the vegetables (coriander, parsley, spinach and lettuce). These concentrations are above the permitted standards

Étude de propriétés de surface de matériaux composites à charges lamellaire et graphitique

La variation de certaines propriétés de matériaux, passe par une modification de leurs surfaces. Nous avons étudié l'influence de l'ajout de renforts sur les propriétés de surface de matériaux photopolymérisables à différentes matrices. Les matériaux obtenus sont soit micro ou nanocomposites, tout dépend de la taille des particules incorporées dans la matrice. Ces études révèlent une grande importance, vu que les résines photopolymérisables trouvent des applications dans des domaines aussi variés que la microélectronique, les adhésifs, les peintures, les vernis ou les emballages [1-6]. Dans cette perspective nous nous sommes intéressés à étudier les énergies de surface, l'effet barrière à l'eau, l'effet écran, l'effet matant et la dureté persoz. Les renforts incorporés sont du type lamellaire ou graphitique. Nous avons établi que l'incorporation, de particules d'argile, augmentait l'énergie de surface du composite alors que les renforts carbonés la faisaient diminuer. Nous avons démontré par ailleurs qu'on pouvait moduler l'effet barrière à l'eau en fonction de la nature et de la concentration du renfort. Les composites étudiés présentaient un effet matant nettement inférieur à celui des matrices

Effect of the Degree of Ionization on the Insertion of Polyvinylpyridinium Salts into Bentonite

The present work reports the effect of the degree of α ionization of poly(4-vinylpyridinium) salts (P4VPS) on the insertion of these polymer salts into bentonite. Nanocomposite materials made of a Na-montmorillonite mineral with poly(4-vinylpyridinium) salts (P4VPS) have been synthesised and characterised. The modified samples were studied by X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The basic spacing of unmodified montmorillonite, determined by XRD, was measured to be 1.38 nm; it was found to increase after modification up to 1.50 nm. The insertion capacity of P4VPS into bentonite increased with the increasing degree of quaternisated nitrogen sites in the polymer

Adsorption of Nickel in Aqueous Solution onto Natural Maghnite

International audienceMaghnite clay obtained from Tlemcen, Algeria was investigated to remove heavy metal ion from wastewater. Thus, the present study includes the adsorption of Ni(II) in aqueous solution on maghnite clay through the process of adsorption under various conditions (with variable concentration of metal ion, temperature, pH and mixing time). Increasing pH favours the removal of metal ions till they are precipitated as the insoluble hydroxides. The uptake is rapid with maximum adsorption being observed within 10 min for Ni(II). In addition, the results obtained from adsorption isotherm indicated that these data can be better fitted with the Langmuir and Freundlich equations than the Dubinin-Radushke-vich (D-R) equation

Synthèse de matériaux hybrides polymère-argile par polymérisation photo-induite

L'objectif de cette étude est de synthétiser des matériaux nanocomposites très résistants par un procédé rapide et non polluant, la polymérisation réticulante Pour celà, nous avons incorporé de l'argile préalablement rendue organophile dans des résines multifonctionnelles. Des phyllosilicates (bentonite, montmorillonite) ont été traitées par divers sels d'ammonium pour les rendre organophiles et ainsi compatibles avec la matrice polymère. La polymérisation de la résine lors de l'exposition au rayonnement ultraviolet a été suivie in situ à l'aide de la spectroscopie infrarouge résolue dans le temps. Dans tous les cas, l'argile organophile n'influence pas ou très peu la cinétique de la réaction de photopolymérisation. 
Le matériau nanocomposite ainsi obtenu est parfaitement transparent, insoluble dans les solvants organiques et présente des propriétés mécaniques nettement améliorées par rapport à la résine seule et au microcomposite, pour un taux de charges compris entre 2 et 5%. L'addition de nanoparticules permet entre autre de réduire de manière efficace la brillance de revêtements UV (plus de 50% pour une résine chargée à 2%). L'association intime de la charge et du liant organique à l'échelle moléculaire confère enfin à ce matériau des propriétés barrières (aux gaz et àl'eau) supérieures celles de la matrice polymère photoréticulée

Adsorption of Zinc in Aqueous Solution onto Natural Maghnite Modified by 3-Aminopropyltriethoxysilane

International audienceZinc (II) was immobilised directly onto clay, maghnite (M13), and after their amine functionalisation with (3-aminopropyl)triethoxysilane (APTES). The APTES-functionalised maghnite (MS) showed higher zinc loading than only maghnite, indicating that the clay functionalisation enhanced the Zn(II) removal. The hydrophilic properties of the clay surface have been modified, but not turned into hydrophobic ones. The graft has indeed a polar amine group and the chain length is too short to present an important hydrophobic character. X-ray diffraction indicated that their original structure had been preserved. This new hybrid organic–inorganic material may be a good alternative for separation and pre-concentration of heavy metal ions. Both adsorbents were characterised by FTIR, XRD, TG and SEM. Both adsorbents showed maximum adsorption of the metal ions at pH 6.1 for Mag and pH 9 for MS. The adsorption processes followed pseudo-second-order kinetics. The Langmuir model best fits the adsorption data