Breaking down condensation polymers 60-61 Flashcards
What ways can polyesters be broken down?
Esters can be hydrolysed under acidic or basic conditions.
- Polyesters are readily hydrolysed by hot queous alkalis, such as aqueous soidum hydroxide.
- Polyesters can also be hydrolysed with hot aqueous acid, such as aqueous hydrochloric acid, although the reaction is much slower than with an alkali.
When a polyester is hydrolysed by hot aqueous alkali what is the ester linkage hydrolysed to?
Each ester linkage is hydrolysed to:
- The sodium salt of a carboxylic acid, -COO-Na+
- a hyroxyl group, -OH.
Write the base and acid hydrolysis of terylene.
How can polyamides be broken down?
Like polyesters, polyamides can be hydrolysed by either hot aqueous acid, such as aqueous hydrochloric acid, or hot aqueous alkali, such as aqueous sodium hydroxide.
In acid conditions what is produced in the hydrolysis of polyamides?
In acid conditions, the dicarboxylic acid is produced together with an ammonium salt of the diamine.
In basic conditions what is produced in the hydrolysis of polyamides?
In basic conditions, the sodium salt of dicarboxylic acid and diamine are formed.
Write out the reactions of the breaking down of nylon-6,6 through acid and base hydrolysis.
Why is there now a need to use develop sustainable and renewable polymer packaging?
Customer demand and environmental pressures, coupled with the spiralling cost of crude oil, have led scientists to investigate and develop renewable and sustainable polymers for packaging.
Name two biodegradable polymers and explain what they are derived from.
Poly(lactic acid), made from lactic acid derived from corn starch.
Poly(glycolic acid), made from glycolic acid isolated from sugar cane and unripe grapes.
What are common properties in biodegradable polymers that allow them to degrade so easily?
Biodegradable polymers oftne have chemical bonds that can undergo hydrolysis.
What are the uses of poly(latic acid)?
Used in compost bags, food packaging and disposable tableware.
What is the main use of poly(glycolic acid)?
Poly(glycolic acid) is used primarily in surgery for stitches.
What are photodegradable polymers?
They are synthetic polymers designed to become weak and brittle when exposed to sunlight for prolonged periods.
What are the two ways of producing a photodegradable polymer?
They can be made by blending the polymer with light-sensitive additives that catalyse the breakdown of the polymer in the presence of UV radiation.
Alternatively, photodegradable plastics can be manufactured by incorporating carbonyl bonds, C=O, within the backbone of the polymer. The carbonyl bonds absorb light and break.
What happens to a photodegradable polymer when exposed to light?
Photodegradable polymers are initially converted into waxy compounds when exposed to light, before being converted to carbon dioxide and water in the presence of bacteria.
