Mohamed Sahnoune

La thèse porte sur l’étude des propriétés et de la durabilité de différents systèmes nanocomposites à base de polyamide-11 (PA11) et d’halloysite algérienne. La première partie est consacrée à l’évaluation du potentiel comme nanocharge de l’halloysite algérienne, en la comparant à une autre commerciale, et ce à travers l’étude de nanocomposites PA11/halloysite préparés par voie fondue. Au vu des différentes techniques utilisées, les résultats révèlent le plein potentiel de l’halloysite algérienne avec des améliorations à la fois des propriétés thermiques et mécaniques après incorporation de la nanocharge. La seconde s’intéresse à l’utilisation de l’halloysite, après fonctionnalisation, comme agent compatibilisant dans des mélanges de polymères à base de PA11. Deux fonctionnalisations ont été testées avec succès, via greffage en surface de chaînes de P(S-co-MAPC1(OH)2) et de SEBS. L’incorporation de ces deux halloysites modifiées dans des mélanges PS/PA11 et PA11/SEBS-g-MA, respectivement, a permis d’obtenir des systèmes ternaires ou l’halloysite modifiée joue le rôle de compatibilisant en se plaçant à l’interface. La troisième et dernière partie du travail se concentre sur la durabilité des nanocomposites PA11/halloysite. D’abord, l’impact de l’halloysite jusqu’à 6 semaines d’immersion, sur la cinétique du vieillissement hygrothermique a été étudié, ainsi que les effets de ce vieillissement sur la morphologie et les propriétés des échantillons. L’étude révèle que l’halloysite augmente la sorption en eau tout en retardant sa diffusion dans le PA11 du fait de la tortuosité induite par sa présence. Une évolution de l'aspect extérieur du matériau est observée avec une diminution des propriétés mécaniques du PA11. Enfin, l’étude de la réaction au feu de nanocomposites PA11/halloysite avec et sans présence de retardateurs de flamme phosphorés a mis en évidence l’effet inhibiteur de l’halloysite après sa fonctionnalisation avec de l’acide méthylphosphonique. Les résultats montrent qu’à taux d’incorporation comparable, l’halloysite modifiée possède un meilleur effet sur le comportement au feu que le polyphosphate d’ammonium ou l’halloysite brute.

Ebenus pinnata is not known as a traditional medicinal plant, but modern research has revealed its richness in components of medicinal value. Yet, the species remains understudied. Here, we assess the climate effect on its morphology, pollen grains size, chromosome numbers, pollen fertility, and antioxidant and antibacterial activities. Plant material was collected from the humid, sub-humid, and semi-arid areas of Northeastern Algeria. Data treatment by principal component analysis and/or cluster analysis and ANOVA post hoc tests revealed three significantly discriminated ecotypes correlated with the climate stage. Significant differences were detected for whole plant morphology, pollen size, and antioxidant activity. No differences were revealed for chromosome numbers, pollen fertility, and antibacterial activity. The studied material showed a chromosome number of 2n = 14, high pollen fertility (94.04 ± 2.64–95.01 ± 2.02%), small pollen grains (polar axis: 17.95 ± 1.10–19.47 ± 1.27 µm; equatorial axis: 12.80 ± 1.18–13.03 ± 0.99 µm), high antioxidant activity (TPC: 50.79 ± 0.51–56.89 ± 0.46 mg/g; DPPH: 71.18 ± 2.24–95.67 ± 2.02 mg/g; RP: 11.09 ± 1.24–25.88 ± 0.26 mg/g), and efficient antibacterial activity (Inhibition area diameter: 9.25 ± 1.06–12.00 ± 1.41 mm). The climate seems to exert a significant impact on multiple aspects of the plant’s biology. It would be interesting to assess the genetic basis of this phenomenon in E. pinnata and other species.

The North African E. pinnata is not known as a traditional medicinal plant but modern research has revealed its extracts richness in anti-oxidants and components of medicinal value. Despite its wide distribution and medicinal value, the species remains taxonomically and phytochemically un-derstudied, especially in Algeria. Here we compare three ecotypes of E. pinnata from the humid, sub-humid and semi-arid areas. The comparison was carried out using classical techniques of multivariate plant morphology, pollen grains size and shape, chromosome numbers, pollen fer-tility, anti-oxidant and antibacterial activities. Significant differences were revealed for all criteria except pollen fertility and antibacterial activity. The semi-arid ecotype showed to be a remote group in relation to the two others except for pollen size where the remote group was the sub-humid ecotype. Pollen size appeared positively correlated with karyotype length. The results (mg GAE/g EXT) of the antioxidant activity tests of the “humid”, “sub-humid” and the “semi-arid” plant groups are as follows, respectively; TPC: 50.79±0.51, 52.04±1.05 and 56.89±0.46; DPPH: 71.18±2.24, 86.39±3.02 and 95.67±2.02; RP: 11.09±1.24, 17.21±0.75 and 25.88±0.26. The inhibition area diameter in the antibacterial activity test varied from 9.25±1.06 mm (Semi-arid plants vs Pseudo-monas aeruginosa) to 12.00±1.41 mm (Sub-humid plants vs Escherichia coli).

The seven-spotted ladybug is a widespread species in the Palearctic, and also acclimated in the Nearctic. It has been classified into different species on the basis of certain morphological characteristics, the geographical origin, and the genitalia structure of both sexes. The morphotypes of North Africa and the Canary Islands are separated, under the name of Coccinella algerica Kovář, 1977, from the rest of the Palearctic and Nearctic populations of Coccinella septempunctata Linnaeus, 1758. In this study, we investigated, on one hand, whether potential reproductive barriers have been established during evolution between the geographically isolated North African and the European seven-spotted ladybugs by performing reciprocal crosses. On the other hand, we assessed their cuticular hydrocarbon (CHC) divergence by GC–MS. The 33 CHCs indentified are with a skeleton of 23 to 32 carbon atoms. These CHCs are linear alkanes (24.9 ± 3.6%) and methyl-branched alkanes (75.1 ± 3.6%) including monomethylalkanes (48.8 ± 2.4%), dimethylalkanes (24.6 ± 4.0%) and trimethylalkanes (2.0 ± 1.0%). Although all the CHC compounds identified are present in the two seven-spotted ladybugs and their F1 and F2 hybrids, their profiles diverged significantly. However, these chemical divergences have not altered the sexual communication to cause reproductive isolation. The two ladybugs interbreed and leave viable and fertile offspring, with even a heterosis effect on reproductive performances, without phenotypic degradation after the F1 generation. So, these chemical differences are just an intraspecific variability in response to heterogeneous environments. The two types of ladybugs can be considered as two different races of the same species with reduced genetic divergence.

The effect of gamma irradiation on neat Polyamide-11 (PA11) and PA11 filled with 3 wt% of halloysite nanotubes (HNTs) was investigated at various doses up to 100 kGy in air and at room temperature. The irradiation test was conducted on sample films prepared by a twin-screw extruder in the first step then cast extrusion. The study showed the formation of a maximum of gel fraction up to 10 and 20 kGy for neat PA11 and PA11/HNTs, respectively. Furthermore, the results indicated the occurrence of crosslinking at low irradiation dose, whereas chain scission took place at higher ones. Additionally, the results revealed that the presence of HNTs limits the impacts of gamma irradiation through a barrier effect. An optimum irradiation dose was found for thermal and mechanical properties, corresponding to the dose for maximum gel formation. Moreover, experimental design was implemented to highlight the main incidences and interactions of both halloysite incorporation and radiation dose on some relevant effects of gamma irradiation.

Les falaises calcaires méditerranéennes de basse altitude sont connues pour leur diversité et leur richesse exceptionnelles en endémiques, souvent insuffisamment évaluées en Algérie. Cette étude est une analyse et une synthèse des évaluations UICN individuelles de trois endémiques chasmophytes algériennes, Silene sessionis, S. aristidis et S. auriculifolia. L’objectif est de comprendre les diverses menaces qui s’exercent sur ce type d’habitat et les enjeux de conservation que représentent les espèces qui l’habitent. L’évaluation de celles-ci a été réalisée dans cinq zones littorales ou sublittorales du pays. Leurs statuts de conservation ont été établis selon les recommandations de l’UICN et validés par le processus officiel de Liste Rouge. De nouveaux sites ont été découverts pour S. sessionis et S. aristidis avec respectivement 23/103 et 152/1174 individus jeunes/total, une zone d'occurrence (EOO) de 2 et 2623 km² et une zone d’occupation (AOO) de 12 et 32 Km². Les menaces identifiées sont les carrières, l’escalade sportive et le béton projeté. Un seul site a été retrouvé pour S. auriculifolia (absent dans trois autres sites historiques), avec seulement six individus, tous sénescents, une EOO et une AOO de seulement 0 et 4 Km respectivement. Les menaces y sont mal identifiées. Les nouveaux statuts retenus pour les trois espèces sont, respectivement, « En Danger d’Extinction », « Vulnérable » et « En Danger Critique d’Extinction ». Des mesures de conservation in situ sont très recommandées concernant S. sessionis et S. aristidis, et une conservation ex situ de S. auriculifolia apparaît urgente. L’enjeu patrimonial de ces falaises en Algérie, souvent situées à proximité de villes et/ou d’infrastructures de transport, mérite un renfort des mesures réglementaires (protection légale des espèces, interdiction de techniques d’aménagement) et des mesures de prévention (études d’impact avant projet). The Mediterranean low-altitude limestone cliffs are known for their exceptional diversity and richness in endemics, often insufficiently assessed in Algeria. The present study is an analysis and a synthesis of individual IUCN assessments of three endemic Algerian chasmophytic species, Silene sessionis, S. aristidis and S. auriculifolia. The aim is to understand the various threats to this kind of habitat and the conservation issues of the species that grow on it. These assessments were carried out in five littoral or sublittoral areas in the north of the country. Their conservation status was established according to the IUCN recommendations and approved by the official Red List process. New sites were discovered for S. sessionis and S. aristidis with, respectively, 23/103 and 152/1174 young/total individuals, an extent of occurrence (EOO) / area of occupancy (AOO) of 2/12 and 2.6/32 km². The identified threats are quarries, sport climbing and shotcrete. A single site was found for S. auriculifolia (absent in three other historical sites) with only six individuals, all senescent and sterile, an EOO and an AOO of only 0 and 4 km respectively. Threats are poorly identified. The new adopted statuses for the three species are, respectively, "Endangered", "Vulnerable" and "Critically Endangered". In situ conservation measures are highly recommended for S. sessionis and S. aristidis; ex situ conservation of S. auriculifolia appears urgent. The heritage issues of these cliffs in Algeria, often located close to cities and/or transport infrastructures, deserve a reinforcement of regulatory measures (legal protection of species, ban of some development technologies) and preventive measures (pre-project impact assessments).

Halloysite nanotubes (HNTs) were successfully incorporated as flame retardants in polyamide‐11 (PA11) after their modification with methyl phosphonic acid. Fourier transform infrared spectroscopy, thermal gravimetric analysis (TGA) and pyrolysis–gas chromatography–mass spectrometry were used to evidence the functionalization of the clay. Raw and modified HNTs were then incorporated by melt mixing in PA11 at 20 wt%. Compositions containing both ammonium polyphosphate (APP) and HNTs were also prepared. TGA and pyrolysis combustion flow calorimeter exhibited enhancement in thermal stability upon incorporation of both raw and modified halloysite nanotubes while APP causes degradation at lower temperature. Cone calorimeter data showed that modified halloysite acts by forming an insulating barrier during the combustion, which limits heat and mass transfers. Moreover, elemental analysis of sample residues after cone test evidenced that a part of the phosphorus of the modified halloysite was transferred to the gaseous phase. These results suggest the full potential of halloysite as fire retardant agent for polyamides. POLYM. ENG. SCI., 59:526–534, 2019. © 2018 Society of Plastics Engineers

This article reports some morphological, tribological, and mechanical data on polyamide-11(PA11)/halloysite nanotube (HNT) nanocomposites prepared by melt-compounding. HNTs extracted from the Djebel Debbagh deposit in Algeria were incorporated into the polymer at 1, 3, and 5 wt%. For comparison, commercial HNTs were also used under the same processing conditions. Scanning electron microscopy showed that both HNTs were homogeneously dispersed in the PA11 matrix, despite the presence of few aggregates, in particular at higher filler contents. The tribological properties were significantly improved, resulting in a decrease in the friction coefficient and the wear rate characteristics due to the lubricating effect of HNTs. This is consistent with optical profilometry data, which evidenced the impact of both types of HNTs on the surface topography of the nanocomposite samples, in which the main wear process was plastic deformation. Furthermore, Young’s modulus and tensile strength were observed to increase with the filler content, but to the detriment of elongation at break and impact strength. Regarding the whole data, the raw Algerian halloysite led to interesting results in PA11 nanocomposites, thus revealing its potential in polymer engineering nanotechnology.