M. García-Morales

Development of highly-transparent protein/starch-based bioplastics

Striving to achieve cost-competitive biomass-derived materials for the plastics industry, the incorporation of starch (corn and potato) to a base formulation of albumen and glycerol was considered. To study the effects of formulation and processing, albumen/starch-based bioplastics containing 0-30 wt.% starch were prepared by thermo-plastic and thermo-mechanical processing. Transmittance measurements, DSC, DMTA and tensile tests were performed on the resulting bioplastics. Optical and tensile properties were strongly affected by starch concentration. However, DMTA at low deformation proved to be insensitive to starch addition. Thermo-mechanical processing led to transparent albumen/starch materials with values of strength at low deformation comparable to commodity plastics. Consequently, albumen biopolymers may become a biodegradable alternative to oil-derived plastics for manufacturing transparent packaging and other plastic stuffs.

End-performance evaluation of thiourea-modified bituminous binders through viscous flow and linear viscoelasticy testing

Straight-run bitumens are no longer suitable in new asphalt mixtures. Consequently, the use of modified bitumens has become more important. In order to both improve binders’ mechanical properties and prevent it from phase separation whilst stored at high temperature, the paving industry is currently developing new modification routes based on reactive agents. This work studies the use of thiourea, which has proven to efficiently broaden the temperature interval over which the binder demonstrates an adequate performance. On the one hand, viscous flow and dynamic shear tests indicate an enhancement in the high in-service temperature strength, along with a reduced thermal susceptibility. On the other hand, results of dynamic flexural tests reveal a significant decrease in the binder glass transition temperature. Finally, the use of master curves and a further frequency/temperature conversion are proposed, in order to attain a suitable viscoelastic characterisation of bituminous binders at low temperatures.

Influence of tragacanth gum in egg white based bioplastics: Thermomechanical and water uptake properties

This study aims to extend the range of applications of tragacanth gum by studying its incorporation into bioplastics formulation, exploring the influence that different gum contents (0-20wt.%) exert over the thermomechanical and water uptake properties of bioplastics based on egg white albumen protein (EW). The effect of plasticizer nature was also evaluated through the modification of the water/glycerol ratio within the plasticizer fraction (fixed at 40wt.%). The addition of tragacanth gum generally yielded an enhancement of the water uptake capacity, being doubled at the highest content. Conversely, presence of tragacanth gum resulted in a considerable decrease in the bioplastic mechanical properties: both tensile strength and maximum elongation were reduced up to 75% approximately when compared to the gum-free system. Ageing of selected samples was also studied, revealing an important effect of storage time when tragacanth gum is present, possibly due to its hydrophilic character.

New foamed/modified bitumen using phosphogypsum waste

This paper describes a new alternative way to produce foamed bitumen, by using phosphogypsum wastes (PG), which is also able to enhance the mechanical behavior of the resulting binder. PG waste is generated worldwide from the production of phosphoric acid and deposited in stacks, causing environmental problems. The results obtained point out that the addition of 10 wt.% PG to a 35/50 paving grade bitumen, when activated with a small amount of strong acid, results in a foamed bitumen with enhanced the rheological properties, especially at high in-service temperatures, after foam collapses. This is mainly attributed to the existence of chemical reactions involving phosphorus compounds contained in the PG, forming new chemical links with some bitumen molecules. Another positive aspect of this technology is that this method produces more stable bitumen foam if compared to the traditional processes, i.e. through direct injection of water. Thus, the combined effect of temperature and the activation agent (sulphuric acid) gives rise to dehydration of the structural water contained in PG yielding foamed bitumen.

The Effect of Water on the Modification of Bitumen with MDI‐PEG Prepolymer

This work studies the role of water during the curing of bitumen modified by isocyanate‐based reactive polymers. A long‐term bitumen modification, which develops for a long period of curing (up to several months), have been identified. It results from chemical reactions between ‐NCO groups in the MDI‐PEG and, mainly, the resin fraction. Long‐term bitumen modification seems to be related to the reaction between reactive polymer and bitumen compounds and to the environmental conditions (probably due to air moisture). Thus, water can slowly diffuse into the bitumen and react with the remaining free ‐NCO groups, giving rise to an increase in the molecular weight of the polymer‐bitumen molecules.