effect of temperture on polymers
Effect of Temperature on Polymers:
Solids on heating eventually melt to form a liquid. With polymers it is not so simple rubber on cooling (in liquid nitrogen) becomes brittle or glassy. Many polymers have a mixture of ordered
(crystalline) regions and random (amorphous) regions. In the glassy state, the tangled chains in the amorphous region are frozen so movement of chains is not possible the polymer is brittle. If the glassy material is heated, the chains reach a temperature at which they can move. This temperature is called the glass transition temperature. Above this temperature the polymer is flexible. At the melting point, the crystalline regions break down and the polymer becomes a viscous liquid.
The Physical Properties of a Polymer Depends on:
Chain Length
The physical properties of a polymer are strongly dependent on the size or length of the polymer chain. Long chains get tangled up in each other and stick together far more than short chains. This means that polymers made of long chain molecules have higher melting points than those made of short chains. Increasing chain length furthermore tends to decrease chain mobility, increase strength and toughness, and increase the glass transition temperature shorter molecules can pass over each other more easily so materials made of these molecules are softer and more ‘squishy’.
Side Group:
The attractive forces between polymer chains play a large part in determining a polymer’s properties. Because polymer chains are so long, these iner-chain forces are amplified far beyond the attractions between conventional molecules. Polar side groups give stronger attraction between polymer chains, making the polymer stronger, different side group on the polymer can lend the polymer to ionic bonding or hydrogen bonding between its own chains. These stronger forces typically result in higher tensile strength and higher crystalline melting points.
Branching:
The branching of polymer chains affects
Solids on heating eventually melt to form a liquid. With polymers it is not so simple rubber on cooling (in liquid nitrogen) becomes brittle or glassy. Many polymers have a mixture of ordered
(crystalline) regions and random (amorphous) regions. In the glassy state, the tangled chains in the amorphous region are frozen so movement of chains is not possible the polymer is brittle. If the glassy material is heated, the chains reach a temperature at which they can move. This temperature is called the glass transition temperature. Above this temperature the polymer is flexible. At the melting point, the crystalline regions break down and the polymer becomes a viscous liquid.
The Physical Properties of a Polymer Depends on:
Chain Length
The physical properties of a polymer are strongly dependent on the size or length of the polymer chain. Long chains get tangled up in each other and stick together far more than short chains. This means that polymers made of long chain molecules have higher melting points than those made of short chains. Increasing chain length furthermore tends to decrease chain mobility, increase strength and toughness, and increase the glass transition temperature shorter molecules can pass over each other more easily so materials made of these molecules are softer and more ‘squishy’.
Side Group:
The attractive forces between polymer chains play a large part in determining a polymer’s properties. Because polymer chains are so long, these iner-chain forces are amplified far beyond the attractions between conventional molecules. Polar side groups give stronger attraction between polymer chains, making the polymer stronger, different side group on the polymer can lend the polymer to ionic bonding or hydrogen bonding between its own chains. These stronger forces typically result in higher tensile strength and higher crystalline melting points.
Branching:
The branching of polymer chains affects