Particulate composite based on coconut fiber and castor oil polyurethane adhesive: An eco-efficient product

This paper presents a study on the potential use of coconut fiber as material to produce particleboards, with two different densities (0.8 g/cm(3) and 1.0 g/cm3), using castor oil-based polyurethane adhesive and urea-formaldehyde. The quality of the product that can be produced by industry was evaluated according to the normative NBR 14.810:2006, where density, thickness swell (TS), absorption, modulus of elasticity (MOE), modulus of rupture (MOR) in static bending and internal bond (IB) were determined. From the results, there was a decrease in TS and increase in MOR of coconut fiber panels with polyurethane resin panels compared with coconut fiber and resin urea-formaldehyde. Scanning microscopy electronic images (SEM) indicated that castor oil-based polyurethane adhesive occupies the gaps between the particles, a factor that contributes to improved physical and mechanical properties of the panels. The assessment of durability through accelerated aging tests shows that panels protected with waterproofing material can be used in environments that have contact with moisture. (C) 2012 Elsevier B.V. All rights reserved.

The influence of "C-factor" and light activation technique on polymerization contraction forces of resin composite

Objectives: This study evaluated the influence of the cavity configuration factor ("C-Factor") and light activation technique on polymerization contraction forces of a Bis-GMA-based composite resin (Charisma, Heraeus Kulzer). Material and Methods: Three different pairs of steel moving bases were connected to a universal testing machine (Emic DL 500): groups A and B - 2x2 mm (CF=0.33), groups C and D - 3x2 mm (CF=0.66), groups E and F - 6x2 mm (CF=1.5). After adjustment of the height between the pair of bases so that the resin had a volume of 12 mm(3) in all groups, the material was inserted and polymerized by two different methods: pulse delay (100 mW/cm(2) for 5 s, 40 s interval, 600 mW/cm(2) for 20 s) and continuous pulse (600 mW/cm(2) for 20 s). Each configuration was light cured with both techniques. Tensions generated during polymerization were recorded by 120 s. The values were expressed in curves (Force(N) x Time(s)) and averages compared by statistical analysis (ANOVA and Tukey's test, p<0.05). Results: For the 2x2 and 3x2 bases, with a reduced C-Factor, significant differences were found between the light curing methods. For 6x2 base, with high C-Factor, the light curing method did not influence the contraction forces of the composite resin. Conclusions: Pulse delay technique can determine less stress on tooth/restoration interface of adhesive restorations only when a reduced C-Factor is present.