ceramics, composites and polymers

• ceramics are non-metal solids with high melting points that are not made from carbon based compounds. some can be made from clay
• ceramics : when it is fired at high temperatures, it hardens to form clay ceramic. It can be moulded when wet
• ceramics are used for pottery and bricks
• another example of a ceramic is glass. generally transparent can be moulded when hot and can be brittle when thin
• most glass made is soda - lime glass, which is made by heating limestone, sand and sodium carbonate until it melts. when the mixture cools it forms glass
• borosilicate glass has a higher melting point than soda - lime glass. Made the same way, using a mixture of sand and boron trioxide
• composites are generally made of two different materials embedded together. fibres or fragments of a material (called reinforcements) are surrounded by a matrix acting as a binder. the properties of a composite depend on the material it is made from
• composite : fibre glass consists of fibres of glass embedded in a matrix made of polymer (plastic). low density, very strong. used for skis, boat.
• composite : carbon fibre have a polymer matrix. the reinforcement is either made from long chains of carbon atoms bonded together or from carbon nanotubes. strong and light. used in aerospace
• composite : concrete is made from sand and gravel embedded in cement. strong. building material
• composite : wood is a natural composite of cellulose fibres held together by an organic polymer matrix
• how its made and what its made from influences the properties of a polymer
• the properties of poly(ethene) depend on the catalyst that was used and the reaction conditions it was made under
• low density poly(ethene) is made from ethene at a moderate temperature under a high pressure. it is flexible and used for bags and bottles
• high density poly(ethene) is made at lower temperature and pressure with a catalyst. more rigid and used for water tanks and pipes.
• the monomers that a polymer is made from determine the type of bonds that form between the polymer chains. these weak bonds between the different molecule chains determine the properties of the polymer
• thermosoftening polymers contain individual polymer chains entwined together with weak intermolecular forces between their chains . you can melt these plastic and remould them
• thermosetting polymers contain monomers that can form cross- links between the polymer chains, holding the chains together in a solid structure. don't soften when heated. strong, hard and rigid