Contents Definition Structure Manufacturing Proses Applications Properties Recycling
Definition Poly(propylene) (PP) is a recyclable thermoplastic addition polymer made from the combination of propylene monomers. It is a linear hydrocarbon polymer. Monomer: Propylene Polymer: Polypropylene
Structure PP is defined as being semi-crystalline. Some of the molecular chains are able to pack relatively closely together and this leads to the formation of a limited amount of highly ordered crystalline areas. PP can form three basic chain structures depending on the position of the methyl groups: Isotactic *(highest crystallinity because the chains can pack closely together.) *(This regular form permits the molecules to crystallize to a hard.) Syndiotactic Atactic *(noncrystalline because of the wide spacing of the polymer chains.) Until catalysts were developed, only soft, atactic PP could be made. However with the use of catalysts PP can be made isotactic or more rigid.
Most commercial polypropylene has an intermediate level of crystallinity between that of low density polyethylene (LDPE) and high density polyethylene (HDPE); It s Young's modulus is also intermediate. Although it is less tough than HDPE and less flexible than LDPE, it is much less brittle than HDPE.
Methyl group on to the hydrocarbon chain can affect physical properties such as melting temperature.
Forms Homopolymers and copolymers are the two main basic types of polypropylene in the market. a) PP homopolymer is the most widely utilized generalpurpose grade. It contains only propylene monomer in a semi-crystalline solid form. Main applications include packaging, textiles, pipes, automotive and electrical applications. b) PP copolymer family is further divided into random copolymers and block copolymers produced by polymerizing of propylene and ethylene.
PP random copolymer is produced by polymerizing together ethylene and propylene. These polymers are flexible and optically clear making them suitable of applications requiring transparency and for products requiring an excellent appearance. PP block copolymer, ethylene content is larger. (Ethylene improves certain properties, like impact resistance) It has co-monomer units arranged in regular pattern. The regular pattern hence makes thermoplastic tougher and less brittle than the random copolymer. These polymers are suitable for applications requiring high strength such as industrial usages.
1.Highest 2.Intermediate 3.Lowest Rigidity Abuse Resistance Transparency Homopolymers 1 3 2 Random copolymers 3 2 1 Block copolymers 2 1 3
price and performance high-performance thermoplastics PPS engineering thermoplastics PBT PET PC production volume standard thermoplastics PP PS PVC semi crystalline Opaque Flexible Chemical resistant amorphous Transparent Brittle Not chemical resistant
Prodution
Market of polypropylene 18% 11% 8% 14% electric others packaging textile automotive 49% Polypropylene Industry, Turkey, Demand by End-Use Sector (%), 2017
Applications
Chemical tanks
Automotive bumpers Dishwasher-safe container
Aplications of PP Automotive Parts
Biaxially oriented polypropylene(bopp)
Properties Chemical Resistance: Bases and acids don t react readily with PP, which makes it a good choice for containers of such liquids, such as cleaning agents, first-aid products, and more. Elasticity and Toughness: PP will act with elasticity over a certain range of deflection but it will also experience plastic deformation early on in the deformation process, so it is generally considered a "tough" material. Fatigue Resistance: PP retains its shape after a lot of torsion, bending and/or flexing. Insulation: PP has a very high resistance to electricity and is very useful for electronic components. Transmissivity: PP can be made transparent, it is normally produced to be naturally opaque in color. PP can be used for applications where some transfer of light is important or where it is of aesthetic value.
PP exhibits only minimal water absorption and permeability. PP is one of the lightest thermoplastics. High crystalline grades provide particularly good resistance to polar organic solvents, alcohols, esters, ketones, fats and oils. PP is normally tough and flexible, especially when copolymerized with ethylene. This allows PP to be used as an engineering plastic. As a plastic it's used to make things like dishwasher-safe food containers. It can do this because it doesn't melt below 160 o C.
HDPE is known to have higher crystallinity than PP which enables it to have more plastic behavior than HDPE and PP show a very long necking behavior. PP is resistant to cracking and stress, even when flexed, so it s used in lots of hinges.
Brittle polymer: Polystyrene Ductile polymer: Polypropylene
Advantages Low cost High flexural strength due to its semi-crystalline nature Good electrical insulator Good impact strength Good fatigue resistance Chemical resistance over a wide range of bases and acids Very resistant to absorbing moisture Disadvantages Highly flammable UV degragation Swell rapidly in chlorinated solvents and aromatics
Manufacturing from polypropylene Extrusion Molding The most common shaping technique is injection molding, which is used for parts such as cups, cutlery, vials, caps, containers, housewares, and automotive parts such as batteries. The related techniques of blow molding and injection-stretch blow molding are also used, which involve both extrusion and molding.
Injection molding
Blow molding
Stretch Blow Molding
Recycling Recycling of polypropylene products involves the following steps: Collection - This involves accumulating used plastic products from the domestic municipal waste stream. This is usually mixed plastic waste in which all types of plastic products will be present. Sorting - The sorting process involves separation of PP products from products made of other types of plastics, based on their recycling codes. Cleaning In this step, paper labels and coloured pails are removed, then the products are granulated and washed which gives rise to clean flake. This flake is converted to uniformly sized pellets for easy feeding into extruder or moulder. Reprocessing by melting The pellets are then fed into an extruder where it is melted at 240 o C and cut into small granules which are now ready to use in making new products. Creating new products using the recycled PP In this step, key parameters of the recycled material such as the melt flow index are measured to assess their suitability for use in different applications. Depending upon these properties, the recycled PP is moulded into various products.
clean flakes
clean flakes