Juan López

Combined Effect of Poly(hydroxybutyrate) and Plasticizers on Polylactic acid Properties for Film Intended for Food Packaging

Poly(lactic acid) PLA, and poly(hydroxybutyrate) PHB, blends were processed as films and characterized for their use in food packaging. PLA was blended with PHB to enhance the crystallinity. Therefore, PHB addition strongly increased oxygen barrier while decreased the wettability. Two different environmentally-friendly plasticizers, poly(ethylene glycol) (PEG) and acetyl(tributyl citrate) (ATBC), were added to these blends to increase their processing performance, while improving their ductile properties. ATBC showed higher plasticizer efficiency than PEG directly related to the similarity solubility parameters between ATBC and both biopolymers. Moreover, ATBC was more efficiently retained to the polymer matrix during processing than PEG. PLA–PHB–ATBC blends were homogeneous and transparent blends that showed promising performance for the preparation of films by a ready industrial process technology for food packaging applications, showing slightly amber color, improved elongation at break, enhanced oxygen barrier and decreased wettability.

Plasticized Poly(lactic acid)–Poly(hydroxybutyrate) (PLA–PHB) Blends Incorporated with Catechin Intended for Active Food-Packaging Applications

Active biobased packaging materials based on poly(lactic acid)-poly(hydroxybutyrate) (PLA-PHB) blends were prepared by melt blending and fully characterized. Catechin incorporation, as antioxidant compound, enhanced the thermal stability, whereas its release was improved by the addition of acetyl(tributyl citrate) (ATBC) as plasticizer. Whereas the incorporation of ATBC resulted in a reduction of elastic modulus and hardness, catechin addition produced more rigid materials due to hydrogen-bonding interactions between catechin hydroxyl groups and carbonyl groups of PLA and PHB. The quantification of catechin released into a fatty food simulant and the antioxidant effectiveness after the release process were demonstrated. The effect of the materials exposure to a food simulant was also investigated. PHB-added materials maintained their structural and mechanical properties after 10 days in a test medium that represents the worst foreseeable conditions of the intended use. Thus, plasticized PLA-PHB blends with catechin show their potential as biobased active packaging for fatty food.

On the Use of PLA-PHB Blends for Sustainable Food Packaging Applications

Poly(lactic acid) (PLA) is the most used biopolymer for food packaging applications. Several strategies have been made to improve PLA properties for extending its applications in the packaging field. Melt blending approaches are gaining considerable interest since they are easy, cost-effective and readily available processing technologies at the industrial level. With a similar melting temperature and high crystallinity, poly(hydroxybutyrate) (PHB) represents a good candidate to blend with PLA. The ability of PHB to act as a nucleating agent for PLA improves its mechanical resistance and barrier performance. With the dual objective to improve PLAPHB processing performance and to obtain stretchable materials, plasticizers are frequently added. Current trends to enhance PLA-PHB miscibility are focused on the development of composite and nanocomposites. PLA-PHB blends are also interesting for the controlled release of active compounds in the development of active packaging systems. This review explains the most relevant processing aspects of PLA-PHB based blends such as the influence of polymers molecular weight, the PLA-PHB composition as well as the thermal stability. It also summarizes the recent developments in PLA-PHB formulations with an emphasis on their performance with interest in the sustainable food packaging field. PLA-PHB blends shows highly promising perspectives for the replacement of traditional petrochemical based polymers currently used for food packaging.

OPTIMIZATION OF VARIABLES ON THE SUPERCRITICAL FLUID EXTRACTION OF PHTHALATE PLASTICIZERS

Abstract Supercritical fluid extraction (SFE) has become an important and useful technique to prepare samples before analysis. The use of supercritical CO2 yields a rapid and quantitative extraction of phthalate plasticizers added to poly(vinyl chloride) (PVC) products. One of them is the plasticized PVC which is a material commonly used in toy manufacturing and other industries. SFE conditions affecting the extraction efficiency have been studied and optimized when pure CO2 is used. Firstly, the influence of the sample particle size in the extraction process has been studied. A fast and quantitative extraction is obtained when the surface/volume ratio of the sample is increased. In addition, the influence of temperature, pressure and time for different phthalates has been studied.

Mechanical and Thermal Properties of Polyvinyl Chloride Plasticized with Natural Fatty Acid Esters

From an industrial point of view, the use of new nontoxic and biodegradable plasticizers coming from natural resources is an interesting alternative to traditional plasticizers based on phthalates. In this study, two types of epoxidized fatty acids esters (EFAE) with different molecular weights have been used in order to produce flexible PVC with low toxicity. Different amounts of EFAE 201 and 401 have been considered in this study. Mechanical and thermal properties have been determined and morphology of fracture surface has been studied by scanning electron microscopy.

Microstructure, mechanical, and thermogravimetric characterization of cellulosic by-products obtained from biomass seeds.

The microstructural, thermal, and nanomechanical characterization of biomass by-products coming from the food industry were studied. Scanning electron microscopy showed a microstructure formed by polygonal grains. The thermal behavior of seeds, evaluated by thermogravimetric analysis, revealed three main components (hemicellulose, cellulose, and lignin). Walnut shell showed the highest thermal stability and also the highest amount of lignin. The nanomechanical aspects were evaluated by nanoindentation. Samples with higher amount of cellulose presented minor modulus values. In accordance with the thermal stability, the highest modulus and hardness were observed in walnut. These by-products could be useful as reinforcement materials for biodegradable plastic industry.

First Ultra-High-Performance Fibre- Reinforced Concrete Footbridge in Spain: Design and Construction

Abstract Ultra-high-performance fibre-reinforced concrete (UHPFRC) is defined as a cement-based composite material that combines three technical advances in concrete: high compressive strength, presence of steel fibres and flowability. Since UHPFRC is a very expensive material, in order that UHPFRC can be considered as a competitive alternative in structural applications, it is necessary to optimise the design of structural systems. This process leads to UHPFRC lightweight structures that minimise the concrete needs and give solutions more similar to steel than concrete. The innovative design of the 43,5 m span footbridge, constructed only with UHPFRC and placed over the Ovejas ravine in Alicante, Spain, is presented in this paper. The new UHPFRC footbridge has replaced the former design devised in steel due to many factors such as lower construction and maintenance costs, high durability in aggressive environment close to the sea leading to an increase in service life and its aesthetic enhancement. This paper covers several issues about the design and construction of this singular footbridge, such as design justification, structural evaluation, UHPFRC mix design, quality control and construction process at all stages. The static and dynamic load tests performed are also presented. The footbridge over the Ovejas ravine has become the first structure constructed with UHPFRC in Spain, and as far as we know, it is the first truss pedestrian footbridge made only of UHPFRC in the world.

STRS: Social Network Based Recommender System for Tourism Enhanced with Trust

Nowadays, the development and use of Recommender Systems has grown significantly as a tool to counteract the overload information problem, by selecting a subset of personalized items from a huge set of information based on user preferences. On the other hand, Multi-Agent System applications have shown to be an important area where the Recommender System theory can be applied. This paper presents a tourism Recommender System architecture integrating Multi-Agent Technology and Social Network Analysis, applying trust concepts to create relevant and good quality personalized recommendations trying to solve the tourist Recommender Systems issues.

Reconstrucción Tridimensional de Superficies en el Cuerpo Humano

A study on the alignment process of data of human morphology obtained by laser acquisition devices is presented in this paper. A three-dimensional latest generation digitizer is used and a methodology of alignment for the human morphology data is established. Also, guides on how to solve problems of this alignment are discussed and a comparative study of point clouds processing programs is carried out. RapidFormTM, the standard software used for editing data acquired by the scanner 3D is compared with PolyworksTM, the alternative to RapidFormTM software used due to its good characteristics for the alignment mechanical parts. Results of the comparison of some software applications are showed.Resumen Se presenta un estudio del proceso de alineacion de datos obtenidos de morfologias humanas mediante un dispositivo de adquisicion por laser. Se utiliza un dispositivo digitalizador tridimensional de ultima generacion y se establece una metodologia de trabajo para el proceso de alineacion de los datos obtenidos de morfologias humanas. Ademas, se indican las directrices para resolver los problemas derivados de esta alineacion y se realiza el estudio comparativo de programas de tratamiento de nubes de puntos. RapidForm™, el software estandar utilizado para la edicion de los datos adquiridos por el escaner 3D es comparado con Polyworks™, el software alternativo a RapidForm™, debido a su calidad de alineamiento de piezas mecanicas. Resultados de la comparacion de algunas aplicaciones de los programas son presentados y discutidos. Palabras clave: reconstruccion 3D, morfologias humanas, alineacion de datos, RapidForm, Polyworks Three-dimensional reconstruction of surfaces in human body

Combined solvent extraction-mass spectrometry determination of free phenol traces in poly(vinyl chloride) products

A gas chromatography-mass spectrometry technique was used for the analysis of trace phenol in poly(vinyl chloride) products. A pre-concentration of samples was made by using a solid-phase extraction cartridge, previously developed for wastewater. The cartridge extraction of several samples yielded recoveries better than 90%. The relative standard deviation of overall recoveries for ten different samples was less than 7%. The detection limit achieved was less than 10 ppb (w/w) for free phenol measured in plastic materials.