Natta utilised catalysts developed for the polyethylene industry and applied the technology to propylene gas. These new polymers with their ability to crystallise soon became popular and polypropylene is now a very successful product in many areas. Commercial production began in and polypropylene usage has displayed strong growth from this date.
The versatility of the polymer the ability to adapt to a wide range of fabrication methods and applications has sustained growth rates enabling PP to challenge the market share of a host of alternative materials in plethora of applications including Oriented polypropylene OPP has seen considerable growth, having replaced cellophane in virtually all applications.
PP does not present stress-cracking problems and offers excellent electrical and chemical resistance at higher temperatures. While the properties of PP are similar to those of Polyethylene, there are specific differences. These include a lower density, higher softening point PP doesn't melt below oC, Polyethylene, a more common plastic, will anneal at around oC and higher rigidity and hardness.
Additives are applied to all commercially produced polypropylene resins to protect the polymer during processing and to enhance end-use performance. Linear hydrocarbon polymer, little or no unsaturation. Similar to polyethylene in many properties, especially solution and electrical.
However, the presence of the methyl group attached to every alternate backbone chain carbon atom can alter the properties in a number of ways: i it can cause a slight stiffening of the chain - increasing the crystalline melting point Tm ; ii it can interfere with the molecular symmetry - depressing crystallinity and hence Tm. Isotactic Syndiotactic. The methyl group also has a chemical effect, i. 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. So…polypropylene is used in nearly every plastics market, from protective packaging to medical equipment. Check out different types of plastic and their uses. What is Polypropylene Plastic? Section About Plastics. Professor Plastics Read Bio.
Discover more about another versatile plastic: HDPE Plastic Speaking of recycling, like many other thermoplastics , polypropylene can be melted and reformed into plastic pellets that then are used to make new products. The history of polypropylene began in when a German chemist named Karl Rehn and an Italian chemist named Giulio Natta first polymerized it.
This led to a large commercial production of the product that began just three years later. Natta synthesized the first syndiotactic polypropylene. The uses of polypropylene are numerous because of how versatile this product is. According to some reports, the global market for this plastic is It is used in products such as the following:. There are a few reasons that manufacturers turn to this type of plastic over others.
Consider its applications and benefits:. The use of polypropylene in everyday applications occurs because of how versatile this plastic is. For example, it has a high melting point compared to similarly weighted plastics. As a result, this product works very well for use in food containers where temperatures can reach high levels — such as microwaves and in dishwashers.
With a melting point of degrees F, it is easy to see why this application makes sense. It is easy to customize, too. One of the benefits it offers to manufacturers is the ability to add dye to it.
It can be colored in various ways without degrading the quality of the plastic. This is also one of the reasons it is commonly used to make up the fibers in carpeting.
It also adds strength and durability to the carpeting. This type of carpeting can be found effective for use not only indoors but also outdoors, where damage from the sun and elements doesn't affect it as readily as other types of plastics. Other benefits include the following:. Understanding polypropylene is important because it is significantly different from other types of products. It's properties allow it to be effective in the use of material popular in everyday use, including any situation in which a non-staining and non-toxic solution is necessary.
0コメント