Polyurethane acrylate networks including cellulose nanocrystals: a comparison between UV and EB- curing

International audienceA water-based polyurethane (PUR) acrylate water emulsion was selected as a radiation curable matrix for preparing nanocomposites including cellulose nanocrystals (CNC) prepared by controlled hydrolysis of Ramie fibers. Cross-linking polymerization of samples prepared in the form of films or of 1 mm-thick bars was either initiated by exposure to the 395 nm light of a high intensity LED lamp or by treatment with low energy electron beam (EB). The conversion level of acrylate functions in samples submitted to increasing radiation doses was monitored by Fourier Transform Infrared Spectroscopy (FTIR). Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) were used to characterize changes in the glass transition temperature of the PUR-CNC nanocomposites as a function of acrylate conversion and of CNC content. Micromechanical testing indicates the positive effect of 1 wt% CNC on Young's modulus and on the tensile strength at break (σ) of cured nanocomposites. The presence of CNC in the PUR acrylate matrix was shown to double the σ value of the nanocomposite cured to an acrylate conversion level of 85% by treatment with a 25 kGy dose under EB, whereas no increase of σ was observed in UV-cured samples exhibiting the same acrylate conversion level. The occurrence of grafting reactions inducing covalent linkages between the polysaccharide nanofiller and the PUR acrylate matrix during the EB treatment is advanced as an explanation to account for the improvement observed in samples cured under ionizing radiation

Effects of temperature on radiolysis of polyethylene in inert and oxidative atmospheres

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Temperature and LET effects on radiation-induced modifications in non-perfect polyethylenes

International audienceRegarding the nuclear safety, the potential accumulation of explosive gases during storage, transport and final disposal of Intermediate Level Long Lived Wastes (IL-LLW) has to be well understood and precisely evaluated. In this paper, we have investigated the Linear Energy Transfer (LET) effect that takes into account the different emitters present in the packages, but also the temperature impact in transport safety cases. We have focused our study on polyethylene, as this polymer presents one of the highest hydrogen radiation chemical yield (G$_0$(H$_2$)), and because of the explosive and inflammable nature of this gas. Chemical defects included in the polymer in the form of carbonyl (C=O) and vinyl (C=C) groups were explored. Depending on the atmosphere of irradiation, they are the main defects formed in polyethylene under irradiation and they are known to be effective energy and radical scavengers. Characterization of the chemical structure of pristine materials has been done. Hydrogen radiation chemical yields were quantified after polymers irradiation. Additionally, the carbon monoxide release was measured for polyethylenes with C=O moieties. Whatever the type of double bonds present in the polymer and whatever the irradiation conditions, hydrogen emission decreases compared to neat materials. Double bonds are effective scavenging groups to which energy is transferred regardless the irradiation nature. Underlying phenomena are explained in this work

Exploring Smart City IoT for Disaster Recovery Operations

Disaster recovery operations are extremely challenging and place significant demands on multiple resources, including local and international emergency response personnel, non-governmental organizations, and the military. In the immediate aftermath of a disaster, one of the most pressing requirements is for situational awareness (SA) so that resources, including personnel and supplies, may be prioritized to have the most impact and help those in the most need. As the recovery operations continue, the SA needs to be continuously updated based on changing conditions in the affected areas. There are many sources of information to provide situational awareness, including reporting by the victims of the disaster as well as observations made by responding personnel. This SA can be significantly enhanced via information obtained from Internet of Things (IoT) devices, especially in a smart city environment. This paper explores the potential to exploit Smart City IoT capabilities to help with disaster recovery operations