Polymers act very differently to ceramics and metals, when attempting to understand their difference it is ideal to know the modulus of elasticity and how strong they are at molecular level. Due to how polymers have a low strength and high thermal expansion they are commonly used in areas of restorative materials, for instance impression materials mostly used are made from elastomeric polymers. Polymers are also utilised in the composite filling material mainly used for anterior teeth. Acrylic resin and other polymers can be used to make removable dentures, other appliances where polymers are used are soft liners, cements, pit and fissures sealant (Sahin, 2017). In terms of elasticity, when chains of polythene are lined up parallel to each other and forced under tensile stress along their long axis the stress which is needed to stretch the atoms in the chain further from each other is quite high (O’Brien, 2003). In addition to that polymers are considered to have a fairly low strength level compared to ceramics and metals, polymers also have strong bonds within polymer chains and the weak bonds between polymer chains.
When the temperature of a material increases it results in increased atomic vibrations. Polymers are known for their strong bonds between atoms, and weak bonds between polymer chains. Therefore, the vibration of carbon atoms that are inside the polymer chain are forced in the directions that are parallel to the long axis, however the atoms are able vibrate in two directions. Therefore, when a polymer is heated there is a separation from the chains in order to allow for the larger amplitude vibration, which is often perpendicular to the long axes of the polymer chains. Additionally, when exploring the thermal behaviour of polymers, they can be categorised into either thermoplastic polymers or thermosetting polymers. The difference between the two is thermoplastic polymers have the ability to be melted and remoulded back into liquid form, whereas thermosetting polymers stay in permanent solid form.
Due to how weak secondary bonds in polymers are, they require water molecules to penetrate between