Why is polypropylene strong

Manufacturers quote "isotactic index" - amount insoluble in hot solvent - which indicates? Polypropylene does not crystallise so readily as polyethylene, it tends to supercool, and this becomes worse at higher molecular weights.

Production of polypropylene takes place by slurry, solution or gas phase process, in which the propylene monomer is subjected to heat and pressure in the presence of a catalyst system. Polymerisation is achieved at relatively low temperature and pressure and the product yielded is translucent, but readily coloured.

Differences in catalyst and production conditions can be used to alter the properties of the plastic. Propylene is obtained, along with ethylene, by cracking naphtha crude oil light distillate. Ethylene, propylene, and higher alkenes are separated by low temperature fractional distillation. From being a byproduct of ethylene in the early 's, propylene is now an important material in its own right.

Polypropylene is a major tonnage polymer with a growth rate higher than the norm for such thermoplastics. This growth rate is partially because of the versatility of polypropylene, and hence the wide range of application areas as indicated above. However, in the UK we have always used more polypropylene than in other European countries, e.

West Germany. This is particularly the case in injection mouldings, which elsewhere might well be made from high density polyethylene. Polypropylene is a relatively easy materials to injection mould in spite of its semicrystalline nature. The absence of any real need for high molecular weight, from the mechanical properties view point, leads to low melt viscosity easy flow.

The pseudoplastic nature of polypropylene enhances this effect at high shear rates fast filling rates. Typically melt temperatures for injection moulding are between and oC. Though they can be as high as , or even oC, for short periods of time. With Flame Retardant grades it recommended that oC is not exceeded.

Mould filling rates are generally on the high side, to ensure good surface finish and strong mouldings free of weld lines and flow fronts. Adequate venting of the mould is essential to prevent burn marks. The melt flow index gives a rough guide to melt flow behaviour, but as a result of the pseudoplastic nature of polypropylene which is strongly dependant on the molecular weight distribution this should not be taken too literally. Spiral flow mould data is sometimes provided by manufacturers as a practical means of assessing the flow behaviour, but this is no substitute for the fundamental melt rheological and thermal data which is now becoming more widely available.

Important factors which affect the shrinkage of polypropylene mouldings include:. As a result of the ease of flow of polypropylene materials they are often chosen for large area mouldings where it is desirable to operate with minimum clamp forces. However for many current polypropylene mouldings, especially where good surface finish is required, it is common practice to use melt temperatures of oC combined with high packing pressures typically about 80 MPa.

How is Polypropylene different from Polyethylene? MORE Polypropylene can be combined with other materials, as can polyethylene. Products made from polypropylene Polyethylene has more demand however than polypropylene. Here is a list of some of the differences between polyethylene and polypropylene: Polyethylene and Polypropylene are very similar as far as physical properties. However, Polyethylene can be produced optically clear where polypropylene can only be made translucent like a milk jug.

Polyethylene does have physical properties that allow it to stand up better in cold temperatures, particularly when using it as signs. Polyethylene is a good electrical insulator.

It offers good tracking resistance, however, it becomes easily electrostatically charged which can be reduced by additions of graphite, carbon black or antistatic agents. Polypropylenes are light in weight. They have a high resistance to cracking, acids, organic solvents and electrolytes.

They also have high melting point and good dielectric properties and are non-toxic. Monomer of polyethylene is ethylene and monomer of polypropylene is propylene. Polyethylene has a lower melting point compared to the higher melting point of polypropylene.

Polypropylene is stiffer and resistant to chemicals and organic solvents compared to polyethylene. This makes polypropylene ideal for total immersion applications where the basket material underneath has to be protected from exposure to various chemicals. Surface Hardness. The hardness of polypropylene is measured on the Rockwell R scale as 92—placing it on the high end of the softer materials measured on that scale.

This means the material is semi-rigid. This makes it more likely to bend and flex with an impact. Operating Temperature. Beyond this temperature, the performance values of the material may be compromised. Melting Temperature. This makes polypropylene unsuited to high-temperature applications of any kind.

Why You Should Use Polypropylene Liquid Cleaning Processes An ideal use case for polypropylene would be an aqueous parts washing process where the basket being coated would be submerged in non-oxidizing agents for prolonged periods of time. Parts Protection Another reason to use polypropylene would be to protect delicate parts from getting scratched. Limited Impact Durability Sharp, sudden impacts from other objects can cause damage to a polypropylene coating.

Author: Marlin Steel. Its industrial material handling containers serve many industries including aerospace, defense, medical and automotive. Request a Quote Today. Another advantage of Polypropylene is that it can be easily copolymerized essentially combined into a composite plastic with other polymers like polyethylene. Copolymerization changes the material properties significantly, allowing for more robust engineering applications than are possible with pure polypropylene more of a commodity plastic on its own.

The characteristics mentioned above and below mean that polypropylene is used in a variety of applications: dishwasher safe plates, trays, cups, etc, opaque to-go containers, and many toys. Thermoplastic materials become liquid at their melting point roughly degrees Celsius in the case of polypropylene. A major useful attribute about thermoplastics is that they can be heated to their melting point, cooled, and reheated again without significant degradation. Instead of burning, thermoplastics like polypropylene liquefy, which allows them to be easily injection molded and then subsequently recycled.

By contrast, thermoset plastics can only be heated once typically during the injection molding process. The first heating causes thermoset materials to set similar to a 2-part epoxy resulting in a chemical change that cannot be reversed. If you tried to h eat a thermoset plastic to a high temperature a second time it would simply burn.

This characteristic makes thermoset materials poor candidates for recycling. Polypropylene is used in both household and industrial applications. Its unique properties and ability to adapt to various fabrication techniques make it stand out as an invaluable material for a wide range of uses. Its growth has been sustained over the years and it remains a major player in the plastic industry worldwide. At Creative Mechanisms , we have used polypropylene in a number of applications across a range of industries.

Perhaps the most interesting example includes our ability to CNC machine polypropylene to include a living hinge for prototype living hinge development. Polypropylene is a very flexible, soft material with a relatively low melting point. These factors have prevented most people from being able to properly machine the material. It gums up. It starts to melt from the heat of the CNC cutter. It typically needs to be scraped smooth to get anything close to a finished surface. But we have been able to solve this problem which allows us to create novel prototype living hinges out of polypropylene.

Take a look at the video below:.