Two methods are widely used for producing BOPP films, namely, the tenter process and tubular process.  Biaxial orientation increases strength and clarity. BOPP is widely used as a packaging material for packaging products such as snack foods, fresh produce and confectionery. It is easy to coat, print and laminate to give the required appearance and properties for use as a packaging material.
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 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. Such isotactic macromolecules coil into a helical shape; these helices then line up next to one another to form the crystals that give commercial isotactic polypropylene many of its desirable properties. Polypropylene can be categorized as atactic polypropylene (aPP), syndiotactic polypropylene (sPP) and isotactic polypropylene (iPP).
- Polypropylene is the second-most widely produced commodity plastic (after polyethylene).
- Isotactic polypropylene is produced at low temperatures and pressures, using Ziegler-Natta catalysts.
- A common application for polypropylene is as biaxially oriented polypropylene (BOPP).
- Melting process of polypropylene can be achieved via extrusion and molding.
- Since a normal distribution is symmetric, that means we also want 6 sigmas between the mean and the USL.
Polypropylene fibre is a major factor in home furnishings such as upholstery and indoor-outdoor carpets. 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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What are the forms of PP films?
In case of atactic polypropylene, the methyl group (-CH3) is randomly aligned, alternating (alternating) for syndiotactic polypropylene and evenly for isotactic polypropylene. This has an impact on the crystallinity (amorphous or semi-crystalline) and the thermal properties (expressed as glass transition point Tg and melting point Tm). Isotactic polypropylene is produced at low temperatures and pressures, using Ziegler-Natta catalysts.
- A Ppk of 1 means that there is “half of a bell curve” between the center of the process and the nearest specification limit.
- 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.
- Well, we want to have 6 sigmas (standard deviations) between the mean of the process and the LSL.
- Polypropylene is widely used in ropes, distinctive because they are light enough to float in water. For equal mass and construction, polypropylene rope is similar in strength to polyester rope.
The availability of sheet polypropylene has provided an opportunity for the use of the material by designers. The light-weight, durable, and colorful plastic makes an ideal medium for the creation of light shades, and a number of designs have been developed using interlocking sections to create elaborate designs. Polypropylene is widely used in ropes, distinctive because they are light enough to float in water. For equal mass and construction, polypropylene rope is similar in strength to polyester rope.
Uses of recycled polypropylene (rPP)
The properties of PP are strongly affected by its tacticity, the orientation of the methyl groups (CH3) relative to the methyl groups in neighboring monomer units (see above). The tacticity of polypropylene can be chosen by the choice of an appropriate catalyst. Polypropylene is the second-most widely produced commodity plastic (after polyethylene).
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). They employed catalysts of a type recently invented by the German chemist Karl Ziegler for synthesizing polyethylene. what is the journal entry to record the issuance of common stock 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.
What are the commercially available PP grades?
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. When polypropylene is biaxially oriented, it becomes crystal clear and serves as an excellent packaging material for artistic and retail products.
ASQ Six Sigma Green Belt Process Performance Questions
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. 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.
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. Polypropylene is also used in particular roofing membranes as the waterproofing top layer of single-ply systems as opposed to modified-bit systems.
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. Atactic polypropylene, on the other hand, lacks any regularity which makes it unable to crystallize and amorphous.
Other processing methods for PP
It is produced via chain-growth polymerization from the monomer propylene. Polypropylene has been used in hernia and pelvic organ prolapse repair operations to protect the body from new hernias in the same location. A small patch of the material is placed over the spot of the hernia, below the skin, and is painless and rarely, if ever, rejected by the body. However, a polypropylene mesh will erode the tissue surrounding it over the uncertain period from days to years.
The polymer shares some of the properties of polyethylene, but it is stronger, stiffer, and harder, and it softens at higher temperatures. (Its melting point is approximately 170 °C [340 °F].) It is slightly more prone to oxidation than polyethylene unless appropriate stabilizers and antioxidants are added. Polypropylene is blow-molded into bottles for foods, shampoos, and other household liquids. It is also injection-molded into many products, including appliance housings, dishwasher-safe food containers, toys, automobile battery casings, and outdoor furniture. These catalysts are activated with special cocatalysts containing an organoaluminum compound such as Al(C2H5)3 and the second type of a modifier.