Plastics: Composition, Types & Reactions PDF

**[PLASTICS]** Composition types: **-carbon-hydrogen bonds** **-monomers-polymers** Then there are **two polymerization reactions** which are *polycondensation* and *polyaddition* **[Polycondensation]** Brings together 2 different or identical substances. Reaction creates water, but it needs t...

**[PLASTICS]** Composition types: **-carbon-hydrogen bonds** **-monomers-polymers** Then there are **two polymerization reactions** which are *polycondensation* and *polyaddition* **[Polycondensation]** Brings together 2 different or identical substances. Reaction creates water, but it needs to be disposed of. E.g. plastics that are created from this reaction is polyester, polyether, polyamide **[Polyaddition]** Bring together two identical substances or 2 different substances. Orders of the atoms are changed compared to monomer. Requires a catalyst and high pressure/temperature to work In polyaddition reaction it doesn't create any byproducts. **[Types of plastics ]** They can be separated into three different categories which are ***thermoplastics, elastomers, and thermosets*** **Thermoplastics** Melts Bonds are *covalent* and relatively temperature resistant. There are also **intermolecular** bonds or ***hydrogen bonds*** which weakens if the temperature increases. determined by chemical or physical properties **Thermoplastics:** are linearly plastically and deformable. **Amorphous:** are disordered glassy, transparent, brittle(hauras) **Semicrystalline:** are partially ordered, crystallites with ductile loops, opaque and better thermal resistance. A diagram of a pyramid Description automatically generated **Semi-crystalline plastics** are: PP (Polypropylene), PE-HD (high density polyethylene), PE-LD (low density polyethylene) and PE-LLD **Amorphous plastics** in the other hand are: *ABS* (Acrylonitrile butadiene styrene), *PS-HI* (polystyrene high impact), *PS* (polystyrene) and *PVC* (polyvinyl chloride) **Thermosets** It has 3D network and narrow meshes, but strong connections between chains and rigid (jäykkä) structure. It is possible only to process in melt phase. Hardening is done always chemically. Thermosets are resistant to higher temperature and that type of thermosets are eg. bakelite and (MF) Melamine formaldehyde. Not possible to melt again and if tried to again thermosets are only start to decomposing. ei uudestaan sulatettaviahajoaa Not scratchable and difficult to cut pieces and if the nail test is done thermoset will get a small hole of burn visible mark **Elastomers** 2D or 3D network with large meshes and connections between chains. Softened at room temperature Lämpökovettuvia thermosets. Elastomers are rubber elastic which means it will spring back. Temp. rise to scorching. Exists also as a thermoplastic (TPE). Eg. Ethylene -propylene-diene-monomer (EPDM)