Degradable Polymers (Cambridge (CIE) A Level Chemistry): Flashcards
Exam code: 9701
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Why are poly(alkenes) non-biodegradable?
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Why are poly(alkenes) non-biodegradable?
Poly(alkenes) have non-polar, saturated carbon chains. This makes them chemically inert, so they cannot be broken down by biological or chemical processes under normal environmental conditions.
True or False?
Polyesters and polyamides can be broken down by hydrolysis, unlike poly(alkenes).
True.
Polyesters and polyamides contain hydrolysable ester and amide links, allowing them to be broken down by acid or alkaline hydrolysis. Poly(alkenes) lack these links and are non-biodegradable.
Define photodegradation.
A photodegradation is the breakdown of polymers using light energy. In polyesters and polyamides, carbonyl groups (C=O) absorb UV light, weakening and breaking the polymer chains.
What products are formed by the acid hydrolysis of a polyamide such as Kevlar?
Acid hydrolysis of Kevlar produces a dicarboxylic acid and ammonium ions. The amide links are broken down by water in the presence of acid.
Alkaline hydrolysis of a polyester produces the .......... and the .......... salt of the dicarboxylic acid.
Alkaline hydrolysis of a polyester produces the diol and the sodium salt of the dicarboxylic acid.
True or False?
Photodegradable polymers in landfill sites may not degrade effectively because they lack access to UV light.
True.
In landfill sites, polymeric materials are buried under other waste. Without access to UV light, photodegradable polyesters and polyamides cannot absorb the energy needed to break down.
How can the energy released by burning poly(alkenes) be used, and what are the environmental consequences?
Burning poly(alkenes) releases energy that can generate electricity. However, complete combustion produces CO2 and water, contributing to the greenhouse effect and global warming.
Define biodegradable polymer.
A biodegradable polymer is a polymer that can be broken down by biological or chemical processes in the environment. Polyesters and polyamides are biodegradable via hydrolysis; poly(alkenes) are not.
Carbonyl groups in polyesters and polyamides absorb .......... light, which weakens and breaks the polymer chains. This process is called ...........
Carbonyl groups in polyesters and polyamides absorb UV light, which weakens and breaks the polymer chains. This process is called photodegradation.
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