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The aim of this study is to highlight the joint evolution of the chemical, morphological, thermal and dielectric behaviors upon the UV weathering of an industrial ethylene-propylene-diene monomer (EPDM) rubber. This latter is used as a housing of composite high voltage insulators which are installed in the Algerian desert. This material was submitted to photochemical aging by irradiating UVA rays (λ = 340 nm) at a temperature of 45 °C in order to simulate the witnessed site conditions. It was shown that the degradation process leading to the formation of oxygenated species and the depolymerization of the material are responsible of the coupling which may appear between the realized measurements. Using Kendall rank correlation analysis, joint evolution models were established. Those models introduce a novel assessment approach of the chemical and morphological status of the aged rubber using electrical and dielectric measurements.

ABSTRACTThe effect of hygrothermal aging on the mechanical behaviour of polyamide 6 (PA6) material filled with 10 wt % multi-walled carbon nanotubes (MWCNTs) has been investigated experimentally. Young’s modulus and flexural modulus of the materials are decreased by more than 30% for the conditions of 25°C/85% RH, compared to the reference conditions of 25°C/55% RH (RT), while the flexural strength by 6–17%. The decrease is larger for the conditions of 40°C/85% RH, which reveals that the effect of combined elevated temperature and moisture is more severe. The decrease in the properties is smaller for the MWCNT/PA6 specimens, which shows that the presence of MWCNTs mitigates the effect of hygrothermal aging. Finally, it is observed that the increase in the properties of the MWCNT/PA6 material is so large, for the specific MWCNT concentration, that it compensates the negative effect of hygrothermal aging.

The effect of hygrothermal aging on the mechanical behaviour of polyamide 6 (PA6) material filled with 10 wt % multi-walled carbon nanotubes (MWCNTs) has been investigated experimentally. Young's modulus and flexural modulus of the materials are decreased by more than 30% for the conditions of 25°C/85% RH, compared to the reference conditions of 25°C/55% RH (RT), while the flexural strength by 6–17%. The decrease is larger for the conditions of 40°C/85% RH, which reveals that the effect of combined elevated temperature and moisture is more severe. The decrease in the properties is smaller for the MWCNT/PA6 specimens, which shows that the presence of MWCNTs mitigates the effect of hygrothermal aging. Finally, it is observed that the increase in the properties of the MWCNT/PA6 material is so large, for the specific MWCNT concentration, that it compensates the negative effect of hygrothermal aging.

AbstractIn this communication, we highlight the remarkable and unexpected mechanical and electrical properties of new porous nanohybrid materials as readily obtained by a two-step preparation procedure. Neat multi-wall carbon nanotube (CNT)-reinforced benzoxazine nanocomposites were first produced. At a CNT content of 5 wt%, pyrolysis of the nanocomposites allowed for recovering porous monolithic nanohybrid materials exhibiting outstanding mechanical resistance (elastic modulus of ca. 50 MPa) for an electrical conductivity as high as 30 S cm−1. Interestingly, long CNTs were found to build up an internal scaffold limiting the deformation of the foamed structure and preserving the geometric shape and dimensional integrity of the sample along the pyrolysis process. The concept of this novel approach paves the way for the production of a very promising choice of viable (nano)materials for use as domains as versatile as in energy storage, catalysis, or shielding applications.

Biobased oligo(butylene succinate)-based thermoplastic polyurethanes (TPUs) were prepared following a two-step polymerization process: condensation of succinic acid and butanediol and the chain extension of resulting hydroxyl-terminated butylene succinate oligomers (OBS) in the presence of butanediol as chain extender and isophorone diisocyanate (IPDI) as coupling agent. Mechanical and thermal properties of the elaborated TPUs were evaluated in terms of hard segment and compared with those of commercial polybutylene succinate (PBS), Bionolle 1001. Whatever the compositions, the ultimate tensile properties of OBS-based TPUs and Bionolle 1001 were found to exhibit similar values ( ≈400%, σ ≈40 MPa), which can be explained by their close molecular weight (60000 g.mol-1 equiv. PS). Interestingly, a higher content of hard segments within OBS-based TPUs leads to materials exhibiting higher rigidity, smaller degree of crystallization, lower melting temperature and weaker stability of the materials with temperature. Such a trend was attributed to the presence of urethane functions and their ability to set up strong H-bonding interchain interactions.

Summary:Starting from gypsum as by‐product of lactic acid fabrication process, novel high performance composites have been produced by melt‐blending PLA and this filler after a previous specific dehydration performed at 500 °C for min. 1h. Due to PLA sensitivity towards hydrolysis, the utilization of β‐anhydrite II (AII) as filler is a prerequisite. Characterized by attractive mechanical and thermal properties due to good filler dispersion throughout the polyester matrix, these composites are interesting in biodegradable rigid packaging or technical applications. Interestingly, tensile strength of PLA – AII composites proved remarkably high, e.g. higher than 35 MPa at 50 wt‐% filler content. However a decrease of impact properties has been recorded. To increase the toughness of these composites while preserving high stiffness an impact modifier based on ethylene copolymer has been mixed with both the polymer matrix and AII by melt‐compounding. The effectiveness of the impact modifier was confirmed in both neat PLA and AII‐based composites. Addition of 5‐10 wt‐% impact modifier into highly filled composites (30 to 40 wt‐% filler) leads to an attractively threefold increase of impact strength with respect to the compositions without modifier, remarkable thermo‐mechanical performances and good filler dispersion.

The influence of different factors on the miscibility of diglycidyl ether of bisphenol A (DGEBA)/thermoplastic blends was studied. DGEBA/poly(ether imide) (PEI) blends exhibited upper critical solution temperature behavior. The addition of a trifunctional epoxy [triglycidyl para-amino phenol (TGpAP)] increased the miscibility window. The addition of diamines as hardeners could also increase [4,4'-methylene-bis(3-chloro-2,6-diethylaniline) (MCDEA)] or decrease (4,4'-diaminodiphenylsulfone) the miscibility window. DGEBA/poly(ether sulfone) (PES) blends showed lower critical solution temperature behavior. The addition of TGpAP had an effect similar to that for PEI blends, but the presence of MCDEA as a hardener decreased the miscibility of epoxy/PES blends. The modeling of the cloud-point curves was performed with the Flory–Huggins equation (Flory, P. J. Principles of Polymer Chemistry; Cornell University Press: Ithaca, NY, 1953; p 672) according to the procedure developed by K. Kamide, S. Matsuada, and H. Shirataki (Eur Polym J 1990, 26, 379), with the interaction parameter used as the fitting parameter. A phenomenological model that takes into account the molar mass of DGEBA and the amount of TGpAP is proposed and is found to predict the cloud-point temperature of any TGpAP/DGEBA/PEI blend. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 83: 1385–1396, 2002

The oegopsid squid family Onychoteuthidae presently comprises six genera (Moroteuthis, Onychoteuthis, Ancistroteuthis, Kondakovia, Onykiaand Chaunoteuthis) but the status of some of these is still uncertain. An interdisciplinary study was undertaken to clarify the phylogenetic relationships, which included a morphological approach (morphometric analysis), and a molecular study of a mitochondrial gene portion (l–rRNA gene, 16S).The morphometric analysis identified two groups, one including some Onychoteuthisand some Moroteuthis knipovitchi, and another including the remaining genera or species. At the intrageneric level, M. knipovitchiappears to be separated from the other species of the genus; M. robustais closely related to M. ingensand M. pacifica. Morphometric analysis confirmed that Kondakovia longimanais different from M. ingens. Likewise, Onychoteuthiswas clearly separated from the other genera, but there is neither geographical grouping nor morphometric differentiation of the Onychoteuthisspecies with the parameters measured. Some specimens were apparently intermediate between the Onychoteuthisand Ancistroteuthisgroups.On a molecular basis, the Onychoteuthidae appeared to be monophyletic. Monophyly of the genus Moroteuthis(four species studied) was not strongly supported: M. knipovitchiwas distinct from the others. The molecular analysis showed three Hawaiian species, Onychoteuthis compacta, O. sp. B and O. sp. C, to be closely related. The gene sequence for the newly created species of Onykiais clearly different from all the others, indicating that it is a true species.