RESUMO
Lignocellulosic wastes resulting from agricultural activities as well as Tetra Pak residues from urban centres can cause significant levels of pollution. A possible action to minimize this problem is to use them in the production of particleboards. The purpose of this study was to evaluate the physical, mechanical, and hydration properties of particleboards manufactured with the mixture of woody biomass (Cupressus lusitanica, Gmelina arborea, and Tectona grandis) and either agricultural wastes [pineapple leaves (Ananas comosus) and palm residues (Elaeis guineensis)] or Tetra Pak residues (TP). The results show that the particleboards prepared with TP and woody biomass can reduce the swelling and water absorption in up to 40% and 50% compared with particleboards without TP. Also, these particleboards had increased flexure resistance and shear stress (up to 100%) compared with those without TP. On the contrary, particleboards prepared with pineapple leaves in combination with woody biomass showed the lowest mechanical properties, particularly for tensile strength, hardness, glue-line shear, and nail and screw evaluation.
Assuntos
Materiais de Construção , Reciclagem/métodos , Madeira/química , Agricultura , Biomassa , Cinética , Maleabilidade , Resistência ao Cisalhamento , Água/químicaRESUMO
El presente trabajo se propone una reflexión acerca de las tensiones y contradicciones de los procesos de construcción identitaria en el trabajo flexible, a partir de los resultados de una investigación en empresas chilenas. El análisis propone la existencia de dinámicas caracterizadas por la tensión entre los elementos heredados de la trayectoria y los aspectos deseados a nivel identitario, así como de las distancias y contradicciones existentes entre la dimensión individual y la colectiva de la construcción identitaria.
The article proposed a reflection on the tensions and contradictions of identity construction processes in flexible work, within the results of a research in some Chilean companies. The analysis suggests the existence of dynamics characterized by a tension between inherited elements from the trajectory and desired aspects in an identity level, as well as distances and contradictions between individual and collective dimensions of identity construction.
Assuntos
Psicologia Social , Chile , Pesquisa QualitativaRESUMO
This work evaluates the feasibility of reacting tannins isolated from Pinus radiata D. Don bark with epoxide resins of the diglycidyl and polyglycidyl ether type. To this end, gel times of aqueous tannin dispersions (40% w/w) with every one of nine selected resins (5% w/w), at previously established pH values (initial equal to 3.3, 4, 7 and 10), have been determined. Products of these reactions were analyzed by FT-IR spectroscopy, and the results were compared with those obtained from tannin-p-formaldehyde and (+)-catechin-p-formaldehyde systems, at the same pH values. Their mechanical properties were evaluated, by dynamic mechanical analysis, at two pH values (3.3 and 10). In general, it was concluded that tannin-epoxide resin systems behave similarly to tannin-paraformaldehyde systems, especially at basic pH values.