Development of a One-Step Process for Production of Foam Core Particleboards using Rigid Polyurethane Foam
A simulated one-step process has been developed for the production of foam core particleboards using rigid polyurethane as the core layer. The results showed that the different techniques used for surface layer separation (unresinated particles and sprayed water) and foam injections (open system and closed system) had no influences on panels’ characteristics. Mechanical properties (e.g., bending strength and internal bond strength) were mostly influenced by the surface layer thickness, while the water absorption and edge screw withdrawal were influenced by the foam cell structure. The use of sprayed water for surface layer separation doubled the formaldehyde emission (FE) of the panels. The addition of urea (based on 10% of the dry resin) to the sprayed water had a positive effect of reducing the final FE. Furthermore, increasing the surface layer thickness had a positive, linear relationship with FE.
Physiomechanical properties of ultra-lightweight foam core particleboard: different core densities
Abstract Ultra-lightweight foam core particleboards have been produced in a novel one-step process with resinated wood particles for the faces and expandable polystyrene (EPS) as core layer material. The mechanical and physical properties of panels were investigated in terms of the different foam core densities and press parameters (temperature, pressing and foaming time). The bending strength properties of the panels were not significantly changed with increasing foam core density from 80 to 120 kg m-3. Panels produced at a press temperature of 130°C (1-EPS) have an improved core-face interface and also a denser surface layer, which positively influences the internal bond and thickness swelling. The panels produced at a press temperature of 160°C (2-EPS) have smaller and more foam cells and an improved fusion of foam beads and properties, which have a positive influence on the edge screw withdrawal resistance and water absorption.
Polystyrene foams. I. Processing‐structure relationships
In this study, processing-structure relationships in expanded polystyrene (EPS) made using near-critical carbon dioxide as a physical blowing agent were investigated. In order to investigate the relationship between structure and properties of EPS it was necessary to be able to make samples with a wide range of controlled structures. For this reason, a systematic investigation of the relationship between processing conditions and structure was performed based on a statistical experimental design. Regression analysis was conducted on the data and expressions were developed to quantify the relationships between structural parameters and processing conditions. The samples were saturated with carbon dioxide at relatively high pressure and ambient temperature and the saturated specimens were expanded at elevated temperatures. The importance of the individual processing parameters was determined. Statistical analysis of data showed that foaming time was the most important factor determining foam density, whereas saturation pressure was the most important factor determining cell size and cell density. By controlling the foaming conditions, EPS samples having the same densities and different cell sizes were produced. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1412–1420, 2003