Norma E. Marcovich

Dependence of the mechanical properties of woodflour–polymer composites on the moisture content

Woodflour of Eucaliptus saligna with two different chemical treatments (mercerization and esterification with maleic anhydride) was used as filler of an unsaturated polyester matrix. Woodflour was treated to increase the interfacial adhesion with the matrix, to improve the dispersion of the particles, and to decrease the water sorption properties of the final composite. The objective of this study was to determine the influence of the moisture content and the woodflour chemical modification on the physical and mechanical properties of the different composites. Results indicated that mechanical properties (compression and bending tests) were severely affected by moisture and chemical modifications. In wet conditions, the composites made from treated woodflour had the lowest flexural modulus and ultimate stress. It was found that this was a reversible effect, because the original values of the compression properties were recovered after drying. Temperature scans in dynamic mechanical tests showed that an irreversible change occurred during exposure to humid environments, probably due to the hydrolysis of the polyester matrix. Essentially, the same behavior was observed for matrix and composites; however, a wood-related transition overlapped the main transition in the case of wet composites.

Polyurethane Foams Obtained from Castor Oil-based Polyol and Filled with Wood Flour:

A natural polyol was prepared from castor oil by alcoholysis with triethanolamine. The oil and the oil-based polyol were characterized by infrared spectroscopy and through the analytical determination of their functional groups, both techniques indicating that the hydroxyl content increased significantly after the alcoholysis reaction. The modified oil was subsequently used as the polyol component in the formulation of rigid polyurethane foams. Wood flour was chosen to be incorporated as filler in these materials. Physical, thermal, and mechanical properties of the neat and reinforced foams were measured, analyzed, and compared to a reference commercial system. The chemical reaction between wood flour and isocyanate strongly affected the composites’ response to thermo-gravimetric tests. Compression modulus and yield strength decreased as wood flour content increased. The effect of the foam density on the compression properties was also investigated.

Mechanical properties of woodflour unsaturated polyester composites

Agrowastes and woodflour are a potential and attractive alternative of cheap reinforcement for brittle polymeric materials because they can reduce costs and, at the same time, improve certain properties. On the other hand, their high moisture sorption and low microbial resistance are disadvantages that need to be considered and, as far as possible, corrected. Polyester resins are widely used throughout the world, and can be processed with reinforcing agents very easily. In this work, the effect of the addition of chemically modified woodflour on the final properties of unsaturated polyester composites was studied. The filler was treated with an alkaline solution to increase its interfacial area and then modified with maleic anhydride (MAN) under severe reaction conditions (140°C, 24 h). No improvement in the mechanical behavior of polyester–woodflour composites was found when particles were only alkali treated, while the composites prepared with MAN-treated woodflour offered better performance under compressive loads. Simple mechanical models used to fit the experimental flexural behavior indicated that a good compatibility between filler and matrix was obtained regardless of the kind (treated or untreated) of reinforcement used.

Composites from sawdust and unsaturated polyester

Wood is an inexpensive filler that reduces the overall cost of polymer composites, with loss in some properties (e.g., ultimate strength, elongation, and water sorption often suffer with the addition of fillers) and a gain in others (e.g., Young modulus increment, reduced weight with respect to inorganic fillers, reduced wear of the processing equipment). Sawdust of Eucaliptus saligna or calcium carbonate have been used as reinforcing fillers of an unsaturated polyester matrix. The ultimate strength, elongation, and modulus are presented as a function of the filler concentration and surface treatment. The dynamic mechanical properties were used to determine the influence of the moisture content on the performance of the final material.

Sawdust modification : maleic anhydride chemical treatment

The aim of this work was to modify the sawdust surface in order to obtain a compatible filler for unsaturated polyesters. Maleic anhydride (MAN) was used as sawdust modifier. The possible esterification of sawdust with MAN was investigated. The efficiency of the treatment was determined by using chemical analysis, infrared spectroscopy (FTIR) and water retention value (WRV) test. Even under mild conditions (room temperature, no catalyst), esterification was achieved. FTIR technique allowed to determine that maleic anhydride reacted by one acid group with the sawdust surface. WRV were analysed using a Langmuir type equation which fitted the experimental results well.ZusammenfassungDiese Arbeit beabsichtigt, die Oberfläche von Sägemehl zu modifizieren, um daraus einen geeigneten Füller für Polyesterkunststoffe zu gewinnen. Als Reagenz wurde Maleinsäureanhydrid (MAN) benutzt. Mögliche Veresterung von OH-Gruppen des Sägemehls wurde untersucht. Das Ausmaß der Reaktion wurde überprüft anhand von chemischen Analysen, Infrarotspektroskopie (FTIR) und Wasserrückhaltevermögen (WRV). Schon unter milden Bedingungen (Zimmertemperatur ohne Katalysator) erfolgte die Veresterung. Aus den FTIR-Spektren ergab sich, daß die Maleinsäure nur mit einer Säuregruppe mit dem Sägemehl reagiert. WRV-Werte wurden mit Hilfe einer Lamgmuir-Gleichung abgschätzt, die die experimentellen Daten gut wiedergibt.

Composites Made from Lignocellulosics and Thermoset Polymers

Abstract Composites made from a stryrene/unsaturated polyester thermoset matrix and woodflours from different wood species have been prepared and tested. Pine (Pino Eliottis), eucaliptus (Eucaliptus Saligna) and marmelero (Ruprechia Laxiflora), a softwood and two semihard woods respectively, were selected for this study because of the availability and local abundance. The particles were used untreated and chemically modified with maleic anhydride (MAN). Thermogravimetric analysis and analytical techniques were used in the characterization of untreated and treated flours. Dispersion of the fibrous particles, as well as maximum filler concentration (accompanied by complete wetting of the wood fibers) was dependent on the treatment and on the wood species utilized. Bending and compression tests indicated some improvement in the performance of the composites, if the woodflour was previously esterified. Scanning electron microscopy (SEM) allowed to observe changes in the fracture surfaces due to MAN treatment of the fibers.

Moisture dependence of the properties of composites made from tung oil based polyurethane and wood flour

Natural composites prepared from a polyurethane (PU) based on tung oil and different percentages of wood flour (WF) or microcellulose (MC) were exposed to humid environments and the resulting changes of their properties were evaluated. The equilibrium moisture content of the composites increased with the wood flour percentage. Dynamic mechanical tests performed during temperature scans revealed the changes resulting from moisture absorption on the main transition temperature of the matrix as well as on the storage modulus. The tensile mechanical properties of the materials were also strongly affected by moisture. The different degree of dispersion achieved during the incorporation of WF and MC into the matrix was considered the main reason for the different effect of each filler on the thermal and mechanical properties of the resulting composites.

Vegetable Oil Based-Polymers Reinforced with Wood Flour

Liquid polymer precursors were synthesized from vegetable oils to be utilized in the preparation of oil based-resins to be later reinforced with a filler also obtained from natural sources. In this work, an unsaturated oil, tung oil, produced in the region was selected as raw material. The vegetable oil was chemically functionalized to obtain a polyol to be further used in polyurethane formulations. Different analysis techniques were used to investigate the hydroxyl content in the modified oil. Oil based composites containing pine wood flour as filler were prepared and mechanically tested.

Wood Flour — Recycled Polyol Based Polyurethane Lightweight Composites

This work is focused on the production and characterization of lightweight polyurethane (PU) composites reinforced with pine wood flour (WF), which can have applications in car interior panels, construction, and acoustic insulation. A crosslinked PU formulated from a recycled polyol was used as matrix. The mechanical performance of the reinforced composites was studied through tensile, three point bending, and dynamic mechanical tests. The strength, modulus, and storage modulus increased with filler concentration.The addition of Al(OH)3 did not reduce the flammability of the composites with low WF concentrations; however, some improvements were found in the case of composites prepared with 20 wt% WF.

Food Biopackaging Based on Chitosan

Chitin, available from waste products of the shellfish industry (shells of the crab, shrimp, etc.), is one of the most abundant natural polymers in the world, and it is used for the production of chitosan by deacetylation. Chitosan, a cationic polysaccharide, natural, nontoxic, biodegradable, biocompatible, bioadhesive, and available commercially, has been employed in a variety of applications ranging from membrane separation, tissue engineering, wound healing, and dressing to hydro gels formation and biodegradable films for food packaging. It is also a well-known biopolymer for its broad antimicrobial activity against bacteria and fungi. Chitosan possesses high positive charge on NH3 + groups when dissolved in aqueous acidic solution, and therefore it is able to adhere to or aggregate with negatively charged molecules forming three-dimensional networks. Moreover, chitosan acts as stabilizer of hydrocolloids, lipids, and mixtures, promoting emulsion formation and interfacial stabilization, so it is frequently used as emulsifier in film-forming solutions. Due to all these advantageous characteristics added to its excellent film-forming properties and low cost, chitosan has generated enormous interests, and thus the quantity and quality of research using this polymer in the area of packaging have increased steadily in the last few years. Chitosan-based food packaging can be classified as “active” because they include systems capable of inhibiting microorganism action and avoiding loss of food quality. In particular, the antimicrobial packaging is one of the most innovative M.R. Ansorena (*) Food Engineering Group, Chemical Engineering Department, Engineering Faculty, National University of Mar del Plata, Mar del Plata, Argentina e-mail: ransorena@fi.mdp.edu.ar N.E. Marcovich • M. Pereda Ecomaterials, Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA-CONICET), Mar del Plata, Argentina e-mail: marcovic@fi.mdp.edu.ar; mpereda@fi.mdp.edu.ar # Springer International Publishing AG 2018 L.M.T. Martínez et al. (eds.), Handbook of Ecomaterials, https://doi.org/10.1007/978-3-319-48281-1_68-1 1 and promising active packaging types developed over the last decade. Accordingly, this chapter discusses in detail the latest advances on films for food packaging based on chitosan.