Transcript Polymers History of Polymers

Polymers
History of Polymers
A plastic material is one that is easily shaped and
takes on a permanent set.
The term polymer refers to a material which has
been made by some polymerisation process.
Additives and polymers combined yield plastics.
Man has been using polymers such as shellac,
horn, gutta, percha, bitumen, lacquer and
amber for centuries.
Ploymers
History of polymers
Research was undertaken to develop and improve
on nature, thus synthetic polymers were
developed.
With an increase in understanding in the structure
of these materials there was rapid development
in the technology of polymers. Their historical
development generally follows five stages:
Polymers
History of Polymers
1- from earliest time to 1900: the realisation of a
new material group,
2- 1900 -1930 The birth of a plastic technology,
3 - 1930 -1950 Plastics as substitute materials
4 - 1950 1970 The “Plastics” age
5 - 1970 - now Engineering Plastics.
Polymers
Structure of polymers
New polymers are being discovered and
developed all the time. Many are developed for
particular property combinations which are
required for specific tasks.
Until 1920 people thought polymers were just thick
jellies or liquids like bitumen. Nobody really
understood them fully.
In 1920 Staudinger showed that polymers were
composed of very large molecules,- thus the
term polymer was developed.
Polymers
structures
Polymers consist of long chains, which are
composed of simple structural units (mers)
joined together.
mer
mer
mer
mer
mer
“poly” = many
mer
mer
mer
Mers strung together to form polymers
mer
Polymers
structures
There are lots of different types of mers that can
join together to form polymers.
Mers are simple organic molecules. These are
special molecules that will link together such as
double link molecules.
These are like linking arms together to form a
human chain.
Polymers
structures
1
Closed molecule
One-handed
Two-handed
Three or more
handles
Linear molecule
Cross-linked
polymers
Polymers
Types of chains
1-Linear chains
These are formed when chains are built up without any
deviation. They are generally formed when the mers
used have only two reactive sites.
2-Branched chains
Deviation can occur when the chain is being formed and
chain branching can result.
3- Cross-linking
The branches can join up to give cross-links between
adjacent chains.
Polymers
structures
Level 1
The types of mers
Level 2
Combining mers together
Level 3
The way mers are joined together
Level 4
The degree of order in polymers
Level 5
Polymer mixtures
Polymers
Thermoset
and
Thermplastics
The basic structure of polymers is that the mers are
strung together in chains. Analogies like paper clip
chains and spaghetti are very useful.
There is a strong covalent bond along the length of the
chain. The way the chains relate to each other
determines the type of structure and, hence
properties.
If the bonds between the chains are primary then a rigid
3D network is constructed and a Thermoplastic
polymer will result.
Polymers
Thermoset
and
Thermoplastics
If the bonds between the chains are weak
secondary bonds, then these will easily be
disrupted by heat. Such polymers are termed
Thermoplastics.
The difference is explained by describing how
butter can be melted in a frying pan and when
allowed to cool, will harden again. Whereas if an
egg is broken and fried in the pan until hard, it
cannot be resoftened.