5. Plastic 3D Printing Materials and Processes:
• It is very difficult to realize how important plastics have become to our everyday lives
500,000,000,000 Kg
20,000,000,000 Kg
6. The terminology of plastics
• If you are going to understand plastics, you are going to learn a lot of new terms.
• Try saying ‘Polyoxybenzylmethyleneglycolanhydryde’.
• The other name is Bakelite.
7. • The word plastic comes from the Greek word plasticos, which means to be shaped or
molded by heat.
• As we will see, shaping plastics by using heat is a basic part of nearly all plastics
manufacturing processes.
Types of Plastics:
• Natural plastics: these are naturally occurring materials and can be shaped and molded by
heat.
• An example of this is amber, which is a form of fossilized pine tree resin and is often used
in jewelry manufacture.
8. • Semi synthetic plastics: these are made from naturally occurring materials that have
been modified or changed but mixing other materials with them.
• An example of this is cellulose acetate, which is a reaction of cellulose fiber and acetic
acid and is used to make cinema film etc.
9. • Synthetic plastics: these are materials that are derived from breaking down, or ’cracking’
carbon-based materials, usually crude oil, coal or gas, so that their molecular structure
changes.
• This is generally done in petrochemical refineries under heat and pressure and is the first
of the manufacturing processes that is required to produce most of our present day,
commonly occurring plastics.
10. • Synthetic and semi synthetic plastics can be further divided into two categories.
• Thermoplastics
• Thermosetting Plastics
• These two categories are defined by the way in which they react when heated.
Thermoplastics:
• These are plastics that can be softened and formed using heat, and when cooled they will
take up the shape that they have been formed into.
• But if heat is reapplied, they will soften again.
• Examples of thermoplastics are acrylic and styrene, probably the most common plastics
found in school workshops.
11. Thermosetting plastics
• These are plastics that soften when heated, and can be moulded when soft, and when
cool they will set into the moulded shape.
• But if heat is reapplied they will not soften again, they are permanently in the shape that
they have been moulded into.
• Examples: polyester resins used in glass reinforced plastics work, and melamine
formaldehyde.
12. THE STRUCTURE OF POLYMERS
• To understand how plastics are made, and why certain plastics are suitable for some uses,
and others not, you have to understand a little about the structure of polymers.
• Polymers are large molecules made up of many smaller molecules. 'Poly' means many and
'mer' means units.
• These smaller units are called monomers (mono = one, mer = unit) and are joined
together through polymerization to form polymers.
• A polymer contains hundreds of thousands of monomers.
13. Crystalline and amorphous polymers
• In ceramics or metals, a crystalline solid comprises repeating unit cells that contain each
of the component atoms in the material.
• Each unit cell is composed of one or more molecular units.
• In a polymer this is not possible; the molecules are chains containing potentially millions
of formula units.
• However, a repeating unit in a polymer - the monomer from which it was made.
• This must be the basis of both long and short-range order in a polymeric material.
• For example, a short section of linear poly(ethylene) looks like this:
