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Questions and Answers
What is the function of water in chemical foaming of polyurethane?
What is the function of water in chemical foaming of polyurethane?
What are the two primary raw materials used to prepare polyurethane?
What are the two primary raw materials used to prepare polyurethane?
What is the purpose of chain extenders in polyurethane chemistry?
What is the purpose of chain extenders in polyurethane chemistry?
What is the repeating unit of polyurethane chemistry?
What is the repeating unit of polyurethane chemistry?
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What is the result of the reaction between isocyanate group and water in chemical foaming?
What is the result of the reaction between isocyanate group and water in chemical foaming?
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What are the two types of foam formation in polyurethane chemistry?
What are the two types of foam formation in polyurethane chemistry?
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Which of the following statements about polyurethane is true?
Which of the following statements about polyurethane is true?
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What is the typical structure of a polymeric foam material?
What is the typical structure of a polymeric foam material?
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Who pioneered the chemistry of polyurethane?
Who pioneered the chemistry of polyurethane?
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What is the internal phase of a foam?
What is the internal phase of a foam?
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What type of materials can be used to form foams?
What type of materials can be used to form foams?
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What has Mobay Corporation introduced for use in the formulation of different types of polyurethane?
What has Mobay Corporation introduced for use in the formulation of different types of polyurethane?
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Study Notes
Introduction to Polyurethane
- Polyurethane emerged as a versatile substitute for traditional foams like polyethylene and expanded polystyrene.
- Developed through the addition polymerization of isocyanates and polyols, allowing customization of properties for various applications.
- Pioneered in the late 1930s by Otto Bayer and colleagues, paving the way for diverse practical uses.
Types of Polyurethane Foams
- Two main types: Rigid Foam and Flexible Foam, distinguished by pore structure and application.
- Foams are created by generating gas bubbles within a base material, leading to a cushiony texture.
- The gas phase (internal phase) is dispersed within a solid plastic matrix (external phase).
Raw Materials Used
- Main raw materials include isocyanate compounds and polyols, requiring additional ingredients:
- Chain extenders: Enhance properties and strength.
- Foaming agents: Induce foam formation.
- Foam stabilizers: Maintain foam structure.
- Pigments: Add color to the final product.
- Various additives: Fillers, light and thermal stabilizers, antioxidants, and antibacterial agents.
Key Isocyanate Compounds
- TDI (Toluene Diisocyanate), MDI (Methylene Diphenyl Diisocyanate), HMDI (Hexamethylene Diisocyanate), and MDCI.
- Polyisocyanates can form adducts with compounds like TMP (Trimethylolpropane) to create more complex structures such as isocyanurate trimers.
Chemistry of Polyurethane Formation
- The isocyanate functional group reacts with reactive hydrogen-containing compounds.
- The structure of the resultant polyurethane depends on the specific isocyanate and polyol used, in addition to any modifiers like chain extenders.
Foam Formation Mechanisms
- Chemical Foaming: Involves water reacting with isocyanate, producing carbon dioxide and amine via carbamic acid decomposition.
- Physical Foaming: Involves the use of physical agents to create gas bubbles without the chemical reactions involved in chemical foaming.
Applications of Polyurethane
- Varied applications across industries, produced by tailoring formulations of monomeric and polymeric isocyanates.
- Notable products: Acrylic PU paints and Melamine PU polish, demonstrating the chemical diversity and functional capabilities of polyurethane.
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Description
Learn about the chemistry of polyurethane, its raw materials, synthesis, and types including rigid foam and flexible foam. Discover the structure and properties of polyurethane.
