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.
Effect of processing parameters on physical and structural properties of lightweight foam core sandwich panels
Abstract Weight reduction is becoming an important topic for the wood-based panels industry. Recent development for foam core particleboard in an integrated process has a great potential to replace heavy conventional particleboards. For further progress of these new types of panels, exploring the physical properties is of high interest. In this study, the effect of two different sets of process parameters (press temperature, pressing and foaming times) on the physical properties and dimensional stability of foam core panels was examined. Panels produced by a lower press temperature (130°C) have a better surface quality. Thickness swelling of panels in short- (2 h) and long-term (24 h, 14 days) immersion shows different trends due to the different attained foam structures. Small inter cellular voids between the foam cells formed during the in situ foaming process play an important role for the water absorption values, especially in short-term immersion. Different process parameters caused different fusion of the beads in the core layer. With increasing panel density, the dimensional stability is significantly decreased because of the increased wood particles in the face layer. With proper selection of process parameters, foam core panels with higher dimensional stability than conventional particleboards can be produced.
Philosophy of Education
LIST OF FIGURES PREFACE ACKNOWLEDGEMENTS 1 Philosophy of Education Before the Twentieth Century Socrates and Plato Aristotle Rousseau Pestalozzi, Herbart, and Froebel Summary Questions Introduction to the Literature 2 The Philosophical and Educational Thought of John Dewey Dewey's Philosophical Orientation The Meaning and Aims of Education Dewey's Psychology Dewey's Theory of Knowledge Democracy and Education The Place of Subject Matter Dewey Today: An Assessment Summary Questions Introduction to the Literature 3 Analytic Philosophy Philosophical Analysis in Education The Analysis of Teaching Current Analyses of Teaching Summary Questions Introduction to the Literature 4 Continental Philosophy Existentialism Phenomenology Critical Theory Hermeneutics Postmodernism Summary Questions Introduction to the Literature 5 Logic and Critical Thinking Formal Logic Informal Logic McPeck's View of Critical Thinking An Alternative Approach Summary Questions Introduction to the Literature 6 Epistemology and Education Justified True Belief Foundationalism Truth Nonfoundational Theories of Knowledge Epistemology and Education Constructivism Summary Questions Introduction to the Literature 7 Philosophy of Social Science and Educational Research How Does Science Grow? A Debate in Educational Research Some Examples Summary Questions Introduction to the Literature 8 Ethics and Moral Education Pre-Enlightenment Ethics Enlightenment Ethics Utilitarianism Deweyan Ethics Moral Education Cognitive Developmentalism Summary Questions Introduction to the Literature 9 Social and Political Philosophy The Current Debate Justice and Equality in Education Summary Questions Introduction to the Literature 10 Problems of School Reform Equality Accountability Standards Testing Summary Questions Introduction to the Literature 11 Multiculturalism and Cosmopolitanism Multiculturalism Cosmopolitanism The Educator's Dilemma Summary Questions Introduction to the Literature 12 Feminism, Philosophy, and Education Feminist Critiques of Philosophy Epistemology Philosophy of Social Science Ethics Care and Education Summary Questions Introduction to the Literature NOTES BIBLIOGRAPHY INDEX