AC14: Polymers Flashcards
What is addition polymerisation
addition of large numbers of alkene molecules to each other to form a long chain polymer
what conditions are required for addition polymerisation
higher temperature and high atm
State 5 benefits of addition polymers
1- these polymers are inexpensive as they’re made from alkenes which are easily and cheaply produced from petroleum
2- have several applications
3- recyclable
4- can be burned and heat released used for energy
5- chemical feedstock - can be converted chemically into other useful products
State 2 disadvantages of addition polymers
1- non-biodegradable
2- when burnt, need to deal with possibly toxic combustion products e.g. HCl - removed by neutralisation with an alkali
What is condensation polymerisation
polymerisation involving the elimination of water
What are polyesters made from
monomers reacted together by esterification reactions
Give two ways polyesters can be formed, and give an example and a use of polyesters
1- monomer containing both an alcohol and a carboxylic acid group
2- two monomers: a diol and a dicarboxylic acid
an example is PGA polyglycolic acid - used for medical sutures
Explain how a monomer containing both an alcohol and a carboxylic acid group can form a polyester
a H2O molecule is removed from the monomer (a H atom from the -OH, and the OH from the COOH for example) - condensation polymerisation
Explain how two monomers, a diol and a dicarboxylic acid can form a polyester
condensation polymerisation - 2 H2O molecules are removed (OH and H from diol, OH and H from dicarboxylic acid, forms an ester link)
what is a more efficient method to make polyesters rather than using alcohol/carboxylic acid condensation, why is this and what is the byproduct
alcohol/acyl chloride condensation:
higher yield and no concentrated acid catalyst is required
2 HCl molecules are formed as a byproduct instead of H2O
What are polyamides made from
monomers linked by secondary amide groups
Give two ways polyamides can be formed, and give two examples example and their uses
1- monomer containing both an amine (-NH2) and a carboxylic acid group
2- two monomers: a diamine and a dicarboxylic acid
an example is nylon - for fabrics, guitar strings
nomex - oven gloves, fire protective suits
Explain how a monomer containing both an amine (-NH2) and a carboxylic acid group can form a polyamide
condensation polymerisation - H2O molecule is removed (H from NH2 and OH from COOH)
Explain how two monomers: a diamine and a dicarboxylic acid can form a polyamide
condensation polymerisation - 2 H2O molecules are removed (OH from both COOH and H from both NH2 to form an amide linkage)
what is a more efficient method to make polyamides rather than using amine/carboxylic acid condensation, why is this and what is the byproduct
acyl chloride/amine condensation:
higher yield and no concentrated acid catalyst needed
two molecules of HCl are formed as a byproduct
are polyesters/polyamides chemically degradable? explain why and how
yes - ester and amide bonds undergo hydrolysis when heated under reflux with aqueous acid or alkali
What are the products of acid catalysed hydrolysis of polyesters and what is the reactant
alcohol and carboxylic acid are the products
2 molecules of H2O is the reactant
What are the products of alkali/base catalysed hydrolysis of polyesters and what is the reactant
alcohol and carboxylate ion are the products
2 molecules of OH- ion is the reactant
What are the products of acid catalysed hydrolysis of polyamides and what is the reactant
carboxylic acid and hydrocarbon with NH3+ on both ends are the products
2 molecules of H2O and H+ are the reactants
What are the products of alkali/base catalysed hydrolysis of polyamides and what is the reactant
carboxylate ion and amide are the products
2 molecules of OH- is the reactant
What is a disadvantage of fibres being made from polyamides/polyesters
because of hydrolysis reactions by acids/alkalis, fibres made by these polymers are easily damaged by spills of acid or alkali
What is the difference between biodegradable and photodegradable polymers
biodegradable - broken down by microorganisms
photodegradable - broken down by UV light
Why are degradable polymers beneficial
they will be more sustainable as they should degrade rather than accumulate as waste polymers
State 6 ways waste polymers can be sustainably rid of
1- recycling
2- PVC recycling
3- Using waste polymers as fuel
4- Feedstock recycling
5- Biodegradable
6- Photodegradable polymers
How are polymers recycled and how do their promote sustainability
Discarded polymers are sorted by type, once sorted - they are chopped into flakes, washed, dried & melted. Recycled polymer is cut into pellets & used to make new products
reduces polymers’ environmental impact by conserving finite fossil fuels & decreasing waste going to landfill
Describe and explain the process of PVC recycling
Recycling PVC is hazardous - when burnt, releases hydrogen chloride which is a corrosive gas & other pollutants like toxic dioxins
PVC is dissolved in solvents, high-grade PVC is recovered by precipitation from the solvent, solvent is used again
How can waste polymers be used as fuel
Can be incinerated to produce heat, generating steam to drive a turbine producing electricity
Describe the process of feedstock recycling
chemical and thermal processes that can reclaim monomers, gases, or oil from waste polymers. The products resemble those produced from crude oil in refineries -> can be used as raw materials for production of new polymers. This process is able to handle unsorted and unwashed polymers
Describe the process of biodegradable recycling
polymers broken down by microorganisms into water, carbon dioxide & biological compounds. These polymers usually are made from starch/cellulose, or have additives that altar their structure so microorganisms can break them down.
Describe the process of photodegradable recycling
oil based polymers, contain bonds that are weakened by absorbing light to start the degradation, alternatively, light-absorbing additives are used
