Cold neutron transmission for the in situ analysis of the gas diffusion in polymers

A novel set up for monitoring the gas diffusion process in polymers has been developed. This set up is based on performing neutron radiography and tomography of polymeric materials under high pressures of gas. Information about the absorption kinetics of supercritical CO2 was obtained. Additionally, solubility, diffusivity, and macroscopic changes in the dimensions of the samples can be in situ obtained through the developed measurement technique. This novel approach can be very helpful to analyze the diffusion kinetics in a wide range of polymer

Multi scale tomographic Analysis of polymeric foams A detailed study of the cellular structure.

This manuscript presents a detailed characterization of the cellular structure of two types of polymeric foams by non destructive multi scale X ray computed micro tomography. This comparative study is conducted in two different polymeric materials rigid polyurethane foams and cross linked low density polyethylene foams . Based on this technique and using 3D image analysis, conventional descriptors of the foams gaseous phase cell size distribution, mean cell size and anisotropy ratio are characterized at a standard voxel size of 5 amp; 8239; m. Complementarily, 0.4 amp; 8239; m voxel size synchrotron X ray tomography data sets have been used to characterize, using a new image analysis approach, features of the solid phase of the foams fraction of mass in the struts and thickness of the different entities of the solid architecture struts and walls . The presented methodology, based on multi scale tomographic analysis, allows obtaining a better understanding of the connection between foaming process and cellular structure and is important to gain knowledge on the structure properties relationships for these material

Effect of solid phase corrugation on the thermo mechanical properties of low density flexible cellular polymers

This manuscript presents the effect of the solid phase corrugation of low density flexible cellular polymers on both their mechanical and thermal properties. First, a detailed quantification of solid phase corrugation has been carried out by means of high resolution synchrotron micro tomography in a collection of polyethylene foams. Subsequently, the collapse stress in compression has been analysed both from the theoretical and experimental points of view achieving a clear relation between the solid phase corrugation and the ratio of theoretically calculated and experimentally measured collapse stress. Finally, solid phase corrugation has been correlated with the thermal expansion coefficient at room temperatur

Pore connectivity of aluminium foams effect of production Parameters

This work studies the effect of some production parameters on the pore connectivity grade i.e., the opencell content associated cracks and missing cell walls of aluminium foams produced via powder metallurgy route. Two types of precursors, extruded and hot uniaxially compressed, were used to create a varied group of Al Si and Al Si Mg alloy based foams in a wide porosity range. The cellular structure and defects were characterized by gas pycnometry and X ray tomography. The analysis performed points to a high pore connectivity in all foam specimens, despite these materials are classified as closed celled due to their appearance, and a significant dependence on all the parameters varied. These dependences and the related mechanisms are discussed in the paper in terms of i the dissimilar foam evolution at initial stages effect of precursor processing technique , ii the solidification shrinkage of each alloy effect of composition and iii the cell wall thinning effect of foam porosity and local drainage . In addition, it has been observed that the interconnections are preferably located in the central parts of the samples, thus suggesting the possible effect of the cooling conditions on defect generatio

Comparison between Neutron and X ray Tomography A Study on Polymer Foams

This work aims at discussing the possibilities of high resolution neutron tomography, in comparison to conventional cone beam X ray CT, based on the results on a set of polymeric foamed materials. The experiments have been carried out at the BER II V7 CONRAD instrument and compared to the images obtained in a CT system based on a microfocus tube and a high resolution flat panel detector. This type of materials has not been previously examined with neutron imaging. The enhanced neutron attenuation relative to the X ray attenuation encouraged this investigation. Nevertheless the results point to a better spatial resolution of X rays in comparison with current neutron tomography resolution although pixel size was in the same order. Reasons behind these results point to a low signal to noise S N ratio in neutron tomography due to the rather low neutron flux and the beam collimating L D ratio causing a reduction in the spatial resolution. Nevertheless the contrast of polymeric materials in neutron imaging offers further possibilities for future developments in high resolution neutron tomograph