Polymerisation

IIC 2012

Objectives

• Recall the many different uses and applications of polymers

• Describe how a polymer is made from monomers and the use of plasticizers.

• Explain the problems that are caused by plasticizers used in polymer manufacture

Recap - Alkenes

• Alkenes are hydrocarbons with double bonds between carbon atoms.

• One double bond is enough, it does not need to be between every carbon atom.

• Examples are ETHENE and PROPENE

The general formula

CnH2n

Using the formula

• Use this to calculate the formula for an alkene with

• 10 carbon atoms

• 15 carbon atoms

• 14 carbon atoms

Using the formula - answers

• Use this to calculate the formula for an alkene with

• 10 carbon atoms C10H20

• 15 carbon atoms C15H30

• 14 carbon atoms C14H28

Polymerisation

Polymerisation

• In polymerisation many small molecules MONOMERS join together to form a larger molecule POLYMER sometimes containing many thousands of monomers.

Names of polymers

• How many polymers can you name?

• Write the list in your book.

Did you get? Add to your own list• Cling film/cellophane• Non stick coating (Teflon) • Tights and clothing (Nylon, Lycra)• Windows and doors (uPVC)• Bottles and food packaging• Waterproof coatings for fabrics (Goretex)• Dental polymers• Wound dressings especially for burns• Hydrogels for use in nappies.• Smart materials such as memory foam.• PVC poly vinyl chloride

Drawing monomers and polymers

monomermonomer

polymer polymer

Polymerisation of PVC

• Can you draw the ‘H diagram’ for PVC from the monomer vinyl chloride?

Answer

Properties of PVC

• PVC is a rigid hard waterproof plastic that is commonly used for applications where durability is required eg “windows, doors and conservatories”.

Rigid or flexible

• It is not always desirable for the plastic to be rigid and brittle.

• Toys in particular need to be safe and to maintain their appearance and for this they need to be flexible.

Plasticizers

• Plasticizers for plastics are additives, most commonly phthalate ester.

• Almost 90% of the market for plasticizer is for PVC, giving this material improved flexibility and durability.

How do plasticizers work?

• Plasticizers work by embedding themselves between the chains of polymers, spacing them apart (increasing the "free volume"), and making it softer.

• For plastics such as PVC, the more plasticizer added, the more flexible and durable it will be.

Plasticizer between chains of polymer

Problems with plasticizers

• Plasticizers evaporate and tend to concentrate in an enclosed space; the "new car smell" is caused mostly by plasticizers evaporating from the car interior.

• Phthalates have been linked with potential health problems. http://news.bbc.co.uk/1/hi/8361863.stm

• http://www.youtube.com/watch?v=gKv1LDZSzPk• When the plasticizer has evaporated the plastics become

brittle and less durable.• Other possible sources of the problem:

http://www.dailymail.co.uk/health/article-105466/Fertility-timebomb-drinking-water.html

Plenary - Questions

• We are going to move onto some questions now