Some Exploitation Properties of Wood Plastic Composites Based on Mixtures of Virgin and Recycled High Density Polyethylenes and Birch Plywood Sanding Dust

Composites based on birch plywood by-product: plywood sanding dust (PSD) and mixtures of virgin (vHDPE) and recycled high density polyethylenes (rHDPE) physical mechanical properties (tensile, flexural strength and modulus, impact strength and microhardness), water resistance and fluidity of the composite melts, were evaluated. These studies showed the possibility of usage of presented mixtures for preparing of qualitative WPCs containing 50 wt.% PSD. It was observed that the melt flow index values decrease with an increase of the content of rHDPE in polymer matrix. DSC measurements showed the diminishing of melting temperature and melting heat of vHDPE by adding of rHDPE. The tensile strength and modulus of composites decrease about 25 – 30 % but frexural strength and modulus have no changes. In the contrary impact strength and microhardness of the samples increased with an increase of additives of rHDPE. Water uptake kinetics of all composites were similar and the total amount of absorbed water after 850 h of the soaking was 12 – 13 %. The optimal content of recycled HDPE in the composites could be 25 – 30 wt.%. In general presented studies showed successful possibilities of the use of additives of rHDPE to vHDPE to produce cheaper WPCs which have no worse guality. Moreover the chosen type of rHDPE in the some cases can compete with investigated vHDPE matrix.

An Integrated Approach to Analyze Long-term Moisture Transport in Honeycomb-core Sandwich Panels

A predictive model for the time evolution of moisture uptake within a honeycomb-core sandwich has been developed. The model takes into account the water diffusion into the skins as well as into the honeycomb part of the sandwich. Experimental evidence has been found of hydrolysis of the aramidic pulp of the honeycomb, which has been consequently accounted for in the model through an irreversible reaction term. The relevant parameters of the model (diffusivities, solubilities, and aramidic hydrolysis kinetic constants), for each single component making up the sandwich, have been experimentally evaluated at several temperatures and relative humidities. Predictions of the model successfully compare with experimentally determined water uptake kinetics into the whole sandwich.

Leaching of Bituminized Waste Products (BWP) by Pure Water: The Contribution of NMR Techniques for the Investigation of the Porous Layer

The aim of this study is to improve the understanding of the water infiltration within Bituminized Waste Products (BWP) and the associated phenomena such as the development of the porous layer, the matrix swelling or the water uptake kinetics. Two sets of leaching experiments have been performed on synthesized model samples that are constituted by inactive soluble and/or insoluble salts (40% wt) embedded in bitumen. Large samples were used to quantify the water uptake kinetics and to control the macroscopic swelling of the matrixes during experiments. Smaller samples were used to characterize the depth distribution of the infiltrated water and its motion properties by NMR techniques (1H-T1 relaxation times and 1D-NMR imaging). These techniques enabled us to study the influence of the matrix chemical composition on the water advance in depth as a function of the leaching time. Results show that insoluble salts have a significant influence on water transport while soluble salts entail the development of large porosities. Preliminary results obtained with an original method based on the measurement of NMR relaxation times along the water concentration in depth are presented. They illustrate the great potential of the approach to further improve our knowledge on the establishment of the aqueous network.