Polypropylene temperatures

Figure 3 Thermal oxidative breakdown of polypropylene (temperature 200°C Poj = 350 Tor stabilizer concentration 0.5 mass percent). 1-without stabilizer 2-Santanox 3-polythiosemicarbazide disulfide 4-polyamineaniline disulfide 5-polydi-iminodiphenyloxide disulfide 6-polyaniline disulfide 7-polydiiminodiphenylmethane disulfide 8-hydrorubeanicpoly disulfide 9-thiocarbamide polysulfide 10-polyiminoazobenzene disulfide.

Figure 2a Dynamic viscosity vs frequency for irradiated Polypropylene, Temperature 180...

Table 1 Mobility regions for physical aging of polypropylene (temperature values refer to homopolymers produced with conventional catalysts)...

Table 12 Presentation of syndiotactic polypropylene temperatures NMR spectroscopic samples produced with stereosequence distributirais (%) fra-5/MAO at different polymerizatirai ...

Polypropylene is translucent and autoclavable and has no known solvent at room temperature. It is slightly more susceptible to strong oxidizing agents than polyethylene. 

This type of adhesive is generally useful in the temperature range where the material is either leathery or mbbery, ie, between the glass-transition temperature and the melt temperature. Hot-melt adhesives are based on thermoplastic polymers that may be compounded or uncompounded ethylene—vinyl acetate copolymers, paraffin waxes, polypropylene, phenoxy resins, styrene—butadiene copolymers, ethylene—ethyl acrylate copolymers, and low, and low density polypropylene are used in the compounded state polyesters, polyamides, and polyurethanes are used in the mosdy uncompounded state. 

Pulp-like olefin fibers are produced by a high pressure spurting process developed by Hercules Inc. and Solvay, Inc. Polypropylene or polyethylene is dissolved in volatile solvents at high temperature and pressure. After the solution is released, the solvent is volatilised, and the polymer expands into a highly fluffed, pulp-like product. Additives are included to modify the surface characteristics of the pulp. Uses include felted fabrics, substitution in whole or in part for wood pulp in papermaking, and replacement of asbestos in reinforcing appHcations (56). 

Some cast (unoriented) polypropylene film is produced. Its clarity and heat sealabiUty make it ideal for textile packaging and overwrap. The use of copolymers with ethylene improves low temperature impact, which is the primary problem with unoriented PP film. Orientation improves the clarity and stiffness of polypropylene film, and dramatically increases low temperature impact strength. BOPP film, however, is not readily heat-sealed and so is coextmded or coated with resins with lower melting points than the polypropylene shrinkage temperature. These layers may also provide improved barrier properties. 

The double-bubble process may be used to produce biaxiaHy oriented film, primarily polypropylene. In this process the first bubble formation is similar to the conventional blown film, except that the bubble is not coUapsed. Rather it is reheated to the orientation temperature and blown and drawn further in a second stage. It is then coUapsed, sUt, and wound. This process is generally limited to a final film thickness of less than 24 p.m. 

Margarine and butter contain fat plus water and water-soluble ingredients, eg, salt and milk soHds that impart flavor and color to the product. Generally these products are distributed at refrigerated temperatures to retain their quaHty. Greaseproof packaging, such as polyethylene-coated paperboard, aluminum foil/paper, parchment paper wraps, and polypropylene tubs, is used for butter and margarine (see Dairy substitutes). 

Oriented polypropylene film (OPP) may be classified as heat-set and non-heat-set, blown and tentered, coextmded and coated. Orientation improves the cold-temperature resistance and other physical properties. Heat-set biaxially oriented polypropylene film (BOPP) is the most widely used protective packagiag film ia the United States. It is used to wrap bakery products, as lamination pHes for potato and com chips, and for pastas and numerous other flexible pouch and wrapping appHcations. Nonheat-set OPP is used as a sparkling, transparent shrink-film overwrap for cartons of candy. 

Extmsion of polyethylene and some polypropylenes is usually through a circular die into a tubular form, which is cut and collapsed into flat film. Extmsion through a linear slot onto chilled rollers is called casting and is often used for polypropylene, polyester, and other resins. Cast, as well as some blown, films may be further heated and stretched in the machine or in transverse directions to orient the polymer within the film and improve physical properties such as tensile strength, stiffness, and low temperature resistance. 

Formic acid is commonly shipped in road or raH tankers or dmms. For storage of the 85% acid at lower temperatures, containers of stainless steel (ASTM grades 304, 316, or 321), high density polyethylene, polypropylene, or mbber-lined carbon steels can be used (34). For higher concentrations. Austenitic stainless steels (ASTM 316) are recommended. 

Electric Submersible Oil Well Pump Cable. These cables are rated up to 5 kV and are designed for highly corrosive oil wells that besides oil also contain brine and other harsh chemicals as well as gases under high pressure and high temperatures (6). Insulations can be based on polypropylene for low temperature wells or on ethylene—propylene mbber which is compounded with special ingredients in order to resist the environments of high temperature wells (Fig. 4). 

Many polymers, including polyethylene, polypropylene, and nylons, do not dissolve in suitable casting solvents. In the laboratory, membranes can be made from such polymers by melt pressing, in which the polymer is sandwiched at high pressure between two heated plates. A pressure of 13.8—34.5 MPa (2000—5000 psi) is appHed for 0.5 to 5 minutes, at a plate temperature just above the melting point of the polymer. Melt forming is commonly used to make dense films for packaging appHcations, either by extmsion as a sheet from a die or as blown film. 

Fabric Composition. The method of fabric manufacture dictates many of the characteristics of the sheet, but intrinsic properties are firmly estabhshed by the base polymer selected. Properties such as fiber density, temperature resistance, chemical and light stabiUty, ease of coloration, surface energies, and others are a function of the base polymer. Thus, because nylon absorbs more moisture than polypropylene, spunbonded fabrics made from nylon are more water absorbent than fabrics of polypropylene. 

Polyester. This fiber has several performance advantages versus polypropylene, although it is less economical. Polyester can produce higher tensile strength and modulus fabrics that are dimensionally stable at higher temperatures than polypropylene. This is of importance in selected appHcations such as roofing. Polyester fabrics are easily dyed and printed with conventional equipment which is of extreme importance in apparel and face fabrics although of lesser importance in most spunbonded appHcations (see Fibers, polyester). 

The use of steam is generally limited to polypropyleae and polyethylene fusion because impractical pressures are required to reach the temperature levels, eg, >200° C, required for bonding polyesters. In general, greater temperature control is required for area bonding polypropylene than for other polymers because the temperature difference between the matrix and biader fibers can be only 3°C (26). 

The value of the glass-transition temperature, T, is dependent on the stereoregularity of the polymer, its molecular weight, and the measurement techniques used. Transition temperatures from —13 to 0°C ate reported for isotactic polypropylene, and —18 to 5°C for atactic (39,40). 

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