Low density wood particleboards bonded with starch foam-study of production process conditions

It has been shown that wood particleboards bonded with sour cassava starch can display low density combined with good physico-mechanical performance, thanks to starch being able to produce a strong foam that fills the interparticular space. Here we optimize the pressing conditions for the production of these panels. The procedure involved hot-plate pressing in two stages: (1) lowering the top platen to a specified thickness for a duration designated as pressing time, followed by (2) raising the top platen to allow panel expansion for a duration designated as hold time. The parameters studied were the pressing time (10 to 150 s), the hold time (290 to 890 s), and the top platen temperature (80 to 190 degrees C). The hold time and pressing time showed to be crucial parameters. The best operating conditions corresponded to 600 s of press cycle time, comprising 60 s of pressing time and 540 s of hold time. The top platen temperature used was 190 degrees C. The particleboards produced had a density of 405 kgm(-3), an internal bond strength of 0.44 Nmm(-2), and a thickness swelling of 13.2%. This can be considered as very good performance, taking into account the panels' low density

Synthesis of low density polyester particles as light-fillers for wood-based panels and thermoplastics

Nowadays, the reduction of weight is an important issue in several areas such as the furniture andautomotive industries. Lightweight wood-based panels, with appropriate mechanical performance, aredesired to facilitate handling and transportation. Concerning the automotive industry, lighter parts allowhigher vehicle efficiency and thus lower CO2 emissions.In this context, we are studying the use of low density particles (LDPs) as light fillers in wood-basedparticleboards and thermoplastics. These particles combine low density and high mechanical resistance asa result of an internal multi-alveolar structure separated by rigid polymeric walls. The structural material isunsaturated polyester crosslinked with styrene.For producing LDPs, an organic phase comprising unsaturated polyester dissolved in styrene isdispersed in an aqueous solution of polyvinyl alcohol (PVA) at high stirring rate. A base is previouslyadded to the organic phase, causing the neutralization of the polyester carboxyl groups and formingpolyester salts which leads to the diffusion from the external aqueous medium. This entrapped waterforms the internal vesicles, and the whole system becomes a water-in-oil-in-water (W/O/W) emulsion(double emulsion). Radical polymerization is then initiated by adding an organic-soluble initiator.Particles are then washed with distilled water, sieved and dried.For each application (wood panels and thermoplastics, respectively) LDPs must have significantlydifferent sizes, hence the great challenge of process optimization. The influence of stirring rate conditions,type of cure initiator and drying conditions on the final internal vesiculation, particle size and density werestudied. Well vesiculated LDPs, with two diameter ranges, 1-4 mm and 3-45 µm, were prepared. Theirperformance in lignocellulosic particleboards and in polypropylene matrix was studied

Low-Density Cardoon (Cynara cardunculus L.) Particleboards Bound with Potato Starch-Based Adhesive

In the present work, and for the first time, totally biosourced low-density particleboards were produced using cardoon particles (a no added value by-product from the Portuguese cheese making industry), bound with a potato starch adhesive. Different starch/cardoon ratios (0.6, 0.8, 1 and 1.2) were tested and the effect of different bio-based additives (chitosan, wood fiber and glycerol) on the performance of the adhesive system was evaluated. The best result was obtained for a formulation with a starch/cardoon mass ratio of 0.8, a chitosan/starch mass ratio of 0.05 and a water/starch mass ratio of 1.75. The particleboards produced had a density of 323 kg·m⁻³, internal bond strength of 0.35 N·mm⁻² and thickness swelling of 15.2%. The values of density and internal bond strength meet the standard requirements of general-purpose lightweight boards for use in dry conditions according to CEN/TS 16368 specification. Moreover, the susceptibility of the formulations with best results was established against subterranean termites and one decay fungi.Laboratory for Process Engineering, Environment, Biotechnology and Energy (UIDB/00511/2020); FCT/MCTES (PIDDAC); North Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF) (NORTE-01-0145-FEDER-000005); Centre Portugal Regional Operational Programme (CENTRO 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF) (CENTRO-01-0246-FEDER-000003).info:eu-repo/semantics/publishedVersio

Preparation of carbon molecular sieve membranes from an optimized ionic liquid-regenerated cellulose precursor

Novel carbon molecular sieve membranes with high separation performance and stability in the presence of humidified streams were prepared from an optimized ionic liquid-regenerated cellulose precursor, in a single carbonization step. Membranes prepared at two different carbonization end temperatures (550 degrees C and 600 degrees C) were analyzed through scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, carbon dioxide adsorption and permeation experiments. The prepared membranes exhibited uniform thickness of approximately 20 mu m and a well-developed microporous structure. The permeation performance of these carbon molecular sieve membranes was above the Robeson upper bound curve for polymeric membranes. In particular, the membrane prepared at 550 degrees C end temperature exhibited permeability to oxygen of 5.16 barrer and O-2/N-2 ideal selectivity of 32.3 and permeability to helium of 126 barrer and He/N-2 ideal selectivity of 788; besides, permeation experiments performed in the presence of ca. 80% relative humidity showed that humidity does not originate pore blockage. These results open the door for the preparation of tailor made precursors that originate carbon molecular sieve membranes with extraordinary separation performances, mechanical resistance and stability

Sucrose Inversion - An Experiment on Heterogeneous Catalysis

llustration of heterogeneous catalysis concepts in laboratory courses is not usually simple or economical. For our undergraduate senior lab course we have developed an environmentally friendly experiment dealing with several aspects of heterogeneous catalysis, having in mind the use of readily available and relatively inexpensive equipment, and chemicals on a compact setup, which students can safely operate. The experiment deals with the acid-catalyzed sucrose inversion, performed in packed bed chemical reactors, where the catalyst is a cation-exchange resin in the H + form. An additional reactor is included for illustrating an enzyme-catalyzed system. The conversion achieved is determined using the Flow Injection Analysis technique

The influence of scavengers on VOC emissions in particleboards made from pine and poplar

This paper studies the performance of scavengers on Volatile Organic Compound (VOC) emissions from wood-based composites. Particleboards made from maritime pine (Pinus pinaster Ait.) and European poplar (Populus spp.) were produced with a UF resin doped with melamine and two scavengers, sodium metabisulfite and urea. VOC emission was measured according to EN ISO 16000. Particleboards made from pine present much higher total VOC (TVOC) emissions than boards made from poplar. Pine emits a higher amount of terpenes, but also aldehydes, acids and terpenoids, while poplar emits mainly acetic acid. Sodium metabisulfite showed an excellent ability to reduce aldehydes emission, which represents nearly 50 % of total emission of particleboards made from pine. When sodium metabisulfite was applied to particleboards made from poplar, reduction of TVOCs was not significant due to the low contribution of aldehydes to TVOCs. Urea presents a low reduction in TVOCs for both wood species

Synthesis and characterization of moisture cured prepolymer polyurethane films

Polyurethane prepolymers are a group of materials representing a reactive intermediate betweenmonomeric isocyanates and polyurethane polymers. They are the polycondensation reaction product of adiisocyanate (hard segments) and a material with hydroxyl functionality such as a polyol -glycol of high molecular weight (flexible segments). Most polyols used in polyurethane synthesis arebased on polyether, polyester or polycarbonate structures. About isocyanate, its structure determines itsreactivity and is known that aliphatic isocyanates are less reactive than aromatic ones.The properties of these prepolymers and the final products (adhesives, sealants and coatings) can be tunedby selecting suitable polyol and isocyanate components, as well as their molar ratio. When wateremulsifiable polymers are intended, anionic monomer dimethylolpropionic acid (DMPA) is incorporatedin the chain as internal emulsifier.The aim of this work was to synthesize and characterize moisture cured polyurethane prepolymers forhigh gloss coating applications. Desired resin must be emulsifiable in water (for easy cleaning of thereactor and auxiliary equipment) and the respective coating must be transparent, colorless and tack free.The following parameters were studied: chemical nature and molecular weight of polyol (polyether andpolycarbonate, from 400 to 2000 molecular weight), initial molar ratio of isocyanate to hydroxyl groups(NCO/OH ratio from 1.5 to 2.5) and presence or absence of DMPA. The isocyanate used was alwaysisophorone diisocyanate.The coatings obtained were caharacterized in terms of thermal stability, Buchholz hardness, scratchresistance, tack, gloss and yellowness index. The results were analysed and related to the expectedpolymer structures for the different cases. The best performance was obtained for polycarbonate polyolwith higher NCO/OH ratio and containing DMPA

Incorporation of an acrylic fatty acid derivative as comonomer for oxidative cure in acrylic latex

An acrylic fatty acid derivative (AcFAD) was evaluated as comonomer for promotion of oxidative cure in waterborne latexes. AcFAD was polymerized by solvent homopolymerization and copolymerization and by emulsion copolymerization, and the final products characterized. In the two polymerization processes, NMR analyses confirmed that the reaction occurred involving both the terminal acrylic double bond and the conjugated double bonds of the aliphatic chain. Compared with a reference acrylic latex, the results obtained after AcFAD incorporation showed a time-dependent increase in gel content and in solvent resistance of dry films. These were ascribed to oxidative cure and consequent self-crosslinking of the acrylic polymer, involving the conjugated double bonds in AcFAD side chains. Oxidative cure was also confirmed by FTIR analyses. In addition, reduction in minimum film-forming temperature evidenced that AcFAD has an internal plasticization effect during film formation. Incorporation of this comonomer in acrylic paint binder formulations constitutes a promising alternative to the use of volatile coalescing agents

Membrane ultrafiltration for oil-from-water separation: Multidisciplinary lab experiment

An ultrafiltration membrane module was assembled and used for treating an oil-in-water (O/W) emulsion. This lab set-up was implemented to teach membrane separation processes within Chemical or Environmental Engineering programmes. The experimental set-up and procedure are described, as well as typical results obtained by students, underlining the main objectives and reasoning expected to be accomplished in each stage of the work. Particular emphasis is given to the discussion of the impact of some variables, such as pressure driving force, surface velocity and emulsion concentration, on concentration polarization, recovery and rejection. The use of this technology at an industrial scale is also discussed. The implemented lab experiment has a relevant pedagogic impact and facilitates students to grasp the inherent theoretical concepts, as perceived from their reports and oral discussions. Moreover, the work has been well accepted and appreciated by students, as can be inferred from the questionnaire; their assessment also showed the fulfilment of the established technical and pedagogic objectives. Particularly relevant is the importance that students attribute to the execution of the experimental work to comprehend the concepts (i.e. importance of a hands-on approach)

Preparation of robust polyamide microcapsules by interfacial polycondensation of p-phenylenediamine and sebacoyl chloride and plasticization with oleic acid

Microcapsules produced by interfacial polycondensation of p-phenylenediamine (PPD) and sebacoyl chloride (SC) were studied. The products were characterized in terms of morphology, mean diameter and effectiveness of dodecane encapsulation. The use of Tween 20 as dispersion stabilizer, in comparison with polyvinyl alcohol (PVA), reduced considerably the mean diameter of the microcapsules and originated smoother wall surfaces. When compared to ethylenediamine (EDA), microcapsules produced with PPD monomer were more rigid and brittle, prone to fracture during processing and ineffective retention of the core liquid. The use of diethylenetriamine (DETA) cross-linker in combination with PPD did not decrease capsule fragility. On the other hand, addition of a small fraction of oleic acid to the organic phase remarkably improved wall toughness and lead to successful encapsulation of the core-oil. Oleic acid is believed to act as a plasticizer. Its incorporation in the polymeric wall was demonstrated by FTIR and (1)H-NMR.This work was funded by FEDER funds through the Operational Programme for Competitiveness Factors (COMPETE), ON.2 – O Novo Norte – North Portugal Regional Operational Programme and National Funds through Foundation for Science and Technology (FCT) under the projects: PEst-C/EQB/UI0511, NORTE-07-0124-FEDER-000026 – RL1_ Energy and PTDC/CTM-NAN/119979/2010. The Bruker Avance III 400 spectrometer is part of the National NMR network and was purchased under the framework of the National Programme for Scientific Reequipment, REDE/1517/RMN/2005, with funds from POCI 2010 (FEDER) and (FCT). Joana R. Góis acknowledges FCT-MCTES for her PhD scholarship (SFRH/BD/69635/2010)