PP What does PP stand for? The Free Dictionary

I have not encountered pg to be used, but I do use it in informal note taking. Polypropylene is also used as an alternative to polyvinyl chloride (PVC) as insulation for electrical cables for LSZH cable in low-ventilation environments, primarily tunnels. This is because it emits less smoke and no toxic halogens, which may lead to production of acid in high-temperature conditions. 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.

  • The high surface-area and naturally oleophilic polypropylene nonwovens are ideal absorbers of oil spills with the familiar[citation needed] floating barriers near oil spills on rivers.
  • The melt flow rate (MFR) or melt flow index (MFI) is a measure of molecular weight of polypropylene.
  • However, a polypropylene mesh will erode the tissue surrounding it over the uncertain period from days to years.
  • It is normally produced in large rolls which are slit on slitting machines into smaller rolls for use on packaging machines.

Atactic polypropylene, on the other hand, lacks any regularity which makes it unable to crystallize and amorphous. What if the CPK value is at 5.63 and Ppk at 2.58 but the xbar chart is having some points out of control limits. Connect and share knowledge within a single location that is structured and easy to search.

Uses of recycled polypropylene (rPP)

The wide color range, durability, low cost, and resistance to dirt make it ideal as a protective cover for papers and other materials. A particularly important one is polypropylene random copolymer (PPR or PP-R), a random copolymer with polyethylene used for plastic pipework. Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene. Polypropylene is most commonly used for plastic moldings, wherein it is injected into a mold while molten, forming complex shapes at relatively low cost and high volume; examples include bottle tops, bottles, and fittings.

  • Polypropylene is the second-most widely produced commodity plastic (after polyethylene).
  • The large number of end-use applications for polypropylene are often possible because of the ability to tailor grades with specific molecular properties and additives during its manufacture.
  • The APA style of referencing, which I have most frequently used, requires that p. is used for single page references or citations (Book Title, p. 13) while for multiple pages you must cite it as (pp. 35-40).
  • This form of citation is used when you are using brief/in text citations.

They employed catalysts of a type recently invented by the German chemist Karl Ziegler for synthesizing polyethylene. Partly in recognition of this achievement, Natta was awarded the Nobel Prize for Chemistry in 1963 along with Ziegler. Commercial production of polypropylene by Montecatini in Italy, Hercules Incorporated in the United States, and Hoechst AG in West Germany (now in Germany) began in 1957. Since the early 1980s production and consumption have increased significantly, owing to the invention of more efficient catalyst systems by Montedison and the Japanese Mitsui Petrochemical Industries, Ltd. A common application for polypropylene is as biaxially oriented polypropylene (BOPP). These BOPP sheets are used to make a wide variety of materials including clear bags.

Manufacturing from polypropylene

The catalysts are differentiated depending on the procedure used for fashioning catalyst particles from MgCl2 and depending on the type of organic modifiers employed during catalyst preparation and use in polymerization reactions. Two most important technological characteristics of all the supported catalysts are high productivity and a high fraction of the crystalline isotactic polymer they produce at 70–80 °C under standard polymerization conditions. Commercial synthesis of isotactic polypropylene is usually carried out either in the medium of liquid propylene or in gas-phase reactors. Another type of metallocene catalysts produce syndiotactic polypropylene.[26] These macromolecules also coil into helices (of a different type) and crystallize. It can be produced commercially either with a special type of supported Ziegler-Natta catalyst or with some metallocene catalysts. Polypropylene fibre is a major factor in home furnishings such as upholstery and indoor-outdoor carpets.

The properties of PP are strongly affected by its tacticity, the orientation of the methyl groups (CH3 in the figure) relative to the methyl groups in neighboring monomer units. Commercially available isotactic what do cash flow statements have to do with liquidity chron com polypropylene is made with two types of Ziegler-Natta catalysts. The first group of the catalysts encompasses solid (mostly supported) catalysts and certain types of soluble metallocene catalysts.


When polypropylene is biaxially oriented, it becomes crystal clear and serves as an excellent packaging material for artistic and retail products. As polypropylene is resistant to fatigue, most plastic living hinges, such as those on flip-top bottles, are made from this material. However, it is important to ensure that chain molecules are oriented across the hinge to maximise strength. Melting process of polypropylene can be achieved via extrusion and molding. Common extrusion methods include production of melt-blown and spun-bond fibers to form long rolls for future conversion into a wide range of useful products, such as face masks, filters, diapers and wipes.

It is also injection-molded into many products, including appliance housings, dishwasher-safe food containers, toys, automobile battery casings, and outdoor furniture. The melt flow rate (MFR) or melt flow index (MFI) is a measure of molecular weight of polypropylene. The measure helps to determine how easily the molten raw material will flow during processing. Polypropylene with higher MFR will fill the plastic mold more easily during the injection or blow-molding production process. As the melt flow increases, however, some physical properties, like impact strength, will decrease. These catalysts are activated with special cocatalysts containing an organoaluminum compound such as Al(C2H5)3 and the second type of a modifier.

Can A Process Meet Specifications?

We call the difference between the two the specification spread, sometimes referred to as the Voice of the Client. Essentially, the molecule consists of a backbone of carbon atoms with attached hydrogen atoms; attached to every other carbon atom is a pendant methyl group (CH3). Very thin sheets (≈2–20 µm) of polypropylene are used as a dielectric within certain high-performance pulse and low-loss RF capacitors.

Is the Process Acceptable? Ppk (Capability)

If then there is marginal difference between Cpk and Ppk and any point still showing out of control limit then it it should be acceptable since absolute values of Cpk and Ppk are much higher than six sigma level. A Ppk of 1 means that there is “half of a bell curve” between the center of the process and the nearest specification limit. The process spread is the distance between the highest value generated and the lowest. Per Strunk and White’s Elements of Style, p. is used to denote 1 page, pp. to denote a range of pages. This form of citation is used when you are using brief/in text citations. All content on this website, including dictionary, thesaurus, literature, geography, and other reference data is for informational purposes only.

If your process spread exceeds the specification spread, then the answer is no.  However, if the process spread is less than the specification spread, then process variation is low enough for it to fit. Process Capability Pp measures the process spread vs. the specification spread. In other words, how distributed the outcome of your process is vs. what the requirements are. When a thin section of molded polypropylene is flexed repeatedly, a molecular structure is formed that is capable of withstanding much additional flexing without failing. This fatigue resistance has led to the design of polypropylene boxes and other containers with “self-hinged” covers. It can also be produced in sheet form, widely used for the production of stationery folders, packaging, and storage boxes.

This information should not be considered complete, up to date, and is not intended to be used in place of a visit, consultation, or advice of a legal, medical, or any other professional. Polypropylene is also used in particular roofing membranes as the waterproofing top layer of single-ply systems as opposed to modified-bit systems. Polypropylene is widely used in ropes, distinctive because they are light enough to float in water.[49] For equal mass and construction, polypropylene rope is similar in strength to polyester rope. A z score is the same as a standard score; the number of standard deviations above the mean. The APA style of referencing, which I have most frequently used, requires that p. is used for single page references or citations (Book Title, p. 13) while for multiple pages you must cite it as (pp. 35-40).

Such applications occur in houses as water filters or in air-conditioning-type filters. The high surface-area and naturally oleophilic polypropylene nonwovens are ideal absorbers of oil spills with the familiar[citation needed] floating barriers near oil spills on rivers. Due to the outbreak of the COVID-19 pandemic in 2020, the demand for PP has increased significantly because it’s a vital raw material for producing meltblown fabric, which is in turn the raw material for producing facial masks. Most commercial polypropylene is isotactic and has an intermediate level of crystallinity between that of low-density polyethylene (LDPE) and high-density polyethylene (HDPE). Isotactic precipitates when the solution is cooled to 25 °C and atactic portion remains soluble in p-xylene. Isotactic polypropylene was discovered in 1954 by Italian chemist Giulio Natta and his assistant Paolo Chini, working in association with the Montecatini Company (now Montedison SpA).

Well, we want to have 6 sigmas (standard deviations) between the mean of the process and the LSL. Since a normal distribution is symmetric, that means we also want 6 sigmas between the mean and the USL. Let’s imagine that your process has 2 specifications; a Lower Specification Limit (LSL) which is the lowest value allowed, and an Upper Specification Limit (USL), the highest value allowed.

These applications take advantage of the toughness, resilience, water resistance, and chemical inertness of the polymer. However, because of its very low moisture absorption, limited ability to take a dye, and low softening point (an important factor in ironing and pressing), polypropylene is not an important apparel fibre. When polypropylene film is extruded and stretched in both the machine direction and across machine direction it is called biaxially oriented polypropylene.

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