alcohol rubber Interview Questions and Answers
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What is alcohol rubber?
- Answer: Alcohol rubber, also known as polyvinyl alcohol (PVA) rubber, is a synthetic rubber derived from the polymerization of vinyl alcohol monomers. It's not technically a "rubber" in the natural latex sense, but shares similar properties like elasticity and flexibility. It's characterized by its excellent water solubility and biocompatibility.
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What are the key properties of alcohol rubber?
- Answer: Key properties include water solubility, biocompatibility, film-forming ability, good adhesion, flexibility, and relatively good strength. It also exhibits good resistance to certain oils and solvents.
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How is alcohol rubber synthesized?
- Answer: Alcohol rubber is typically synthesized through the hydrolysis of polyvinyl acetate (PVAc). PVAc is first polymerized, then treated with an alkaline solution to replace the acetate groups with hydroxyl groups, resulting in PVA.
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What are the different grades of alcohol rubber available?
- Answer: Grades vary based on the degree of hydrolysis (the percentage of acetate groups replaced by hydroxyl groups), molecular weight, and viscosity. Higher degrees of hydrolysis generally lead to increased water solubility and lower flexibility.
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What are the applications of alcohol rubber in the medical field?
- Answer: Its biocompatibility makes it suitable for applications like contact lenses, surgical sutures, drug delivery systems, and wound dressings. Its water solubility is advantageous in biodegradable medical devices.
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How does alcohol rubber's water solubility affect its applications?
- Answer: Water solubility is both a benefit and a limitation. It allows for biodegradability and easy removal in some applications, but it also limits its use in environments with prolonged water exposure. Formulations often incorporate crosslinking to reduce solubility.
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What are the limitations of alcohol rubber?
- Answer: Limitations include its susceptibility to degradation by strong acids and bases, relatively low tensile strength compared to other rubbers, and its sensitivity to moisture and temperature changes.
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How is alcohol rubber processed?
- Answer: Processing often involves dissolving the PVA in water, then casting, molding, or extrusion to create the desired shape. Drying and further processing (like crosslinking) may be required.
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What is the role of crosslinking in alcohol rubber?
- Answer: Crosslinking improves the mechanical properties, such as tensile strength and resistance to water, by creating chemical bonds between PVA chains, reducing water solubility and increasing durability.
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How is the degree of hydrolysis determined in alcohol rubber?
- Answer: The degree of hydrolysis is determined through various analytical techniques, such as titration or nuclear magnetic resonance (NMR) spectroscopy, which measure the remaining acetate content.
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How does temperature affect the properties of alcohol rubber?
- Answer: Temperature affects the water solubility and mechanical properties. Higher temperatures can increase solubility and potentially weaken the material. Low temperatures can make it brittle.
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What are some common additives used with alcohol rubber?
- Answer: Common additives include plasticizers to improve flexibility, fillers to enhance strength and reduce cost, and crosslinking agents to improve properties.
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Can alcohol rubber be recycled?
- Answer: Recycling depends on the specific formulation and application. Some formulations may be easier to recycle than others. Often, the material degrades in the environment.
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What is the shelf life of alcohol rubber?
- Answer: Shelf life varies significantly depending on storage conditions (temperature and humidity), the degree of hydrolysis and any added stabilizers. Proper storage is crucial to maintain its properties.
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