Polypropylene, 411 Table

In the United States, fibers and injection mol ding are the main appHcations for polypropylene (Table 8), followed by film. In Europe and Japan, injection mol ding appHcations predominate (Table 10). This market area is more likely to decline in economic recession, as consumers postpone purchases of apphances and automobiles. Film appHcations are important in both regions, but fibers are a much less important use for polypropylene in Japan than in other developed regions. The heavy use of polypropylene nonwovens in the manufacture of disposable diapers and similar products, and the wide use of polypropylene carpets in the United States, account for the greater consumption of fibers. 

Consistent with the preceeding acid work, when TMPTA is added to the monomer solutions containing either lithium salt or urea, synergistic effects are observed for the radiation grafting of styrene to polypropylene (Table IV). Again the maximum increase in yield occurs in the monomer solution corresponding to the Trommsdorff peak. 

Similar synergistic effects are found with TMPTA and the inorganic additive, lithium nitrate, for photografting to polypropylene (Table VIII). 

As the time of exposure to UV is increased, the magnitude of the synergistic effect between TMPTA and lithium nitrate is increased dramatically for the UV grafting of styrene to polypropylene (Table XI) such that after 16 hours of irradiation very large yields are obtained. Even with TFMA, the grafting yield in the 30% monomer solution is increased by almost one order of magnitude due to the synergistic effect. 

Fig. 3.7. Reduced stored free energy FB wvs. reduced shear rate /fy for two samples of polypropylene (Table 3.3) in transdecalin at ISO0 C (74). The following concentrations in wt. per cent are used Sample A (A) 2.5, ) 2.0, ( ) 1.0 ...

Effect of Substrate. Again, polyethylene and ethylene-propylene copolymers are better substrates for block formation than polypropylene (Table XI). Polyethylene is better than polypropylene, and a polyethylene-polypropylene-polyethylene type of block polymer is better than polyethylene. This agrees with what has been found for AFR polymers containing methylvinylpyridine and acrylonitrile. It also supports our belief that AFR polymers are formed by the growing of a free radical polymer onto active ends of anionic polymer chains. If it were a random grafting reaction, it would be hard to explain why a propylene polymer with a more vulnerable tertiary hydrogen should give a lower... 

An LVP may be packaged in a vial, a flexible bag, or, in some cases, a disposable syringe. Packaging material for cartridges, syringes, vials, and ampules are usually composed of polypropylene (Table 2). 

Polypropylene (Table I, compounds 4 to inclusive). High Moleculer Weight High Density Polyethylene. 

Comparison of the carboxylation procedures using acrylic acid in lieu of maleic anhydride is even more striking with isotactic polypropylene (Table V) than with polyethylene. 

Weakening effect of nanoparticles was observed not only with wood-flonr-filled polypropylene (Tables 4.28-4.30) bnt also with rice-hnlls-fllled polypropylene on both tensile and flexural properties (Tables 4.31 and 4.32). 

If the fiber is to be ironed, its Tg should be above 200°C. Branching and crosslinking are nndesirable since they inhibit crystalline formation. Even so, some crossfinkmg may be present to maintain a given orientation, snch as desired in permanent press clothing. While most fibers are made from condensation polymers, new treatments allow some fibers to be made from olefinic materials snch as polypropylene (Table 3). 

Glass Fiber-Reinforced Polypropylene Table 9.9 Effect of Fiber Glass Sizing Agents on the IFSS 287... 

Dielectric relaxation and dielectric strength of polypropylene Table 2 Dielectric strength values on PP samples of different thickness... 

In addition, self-reinforced fiber composites are far superior to glass and carbon fiber materials with regard to their energy consumption during production and recycling because of the low melting point of polypropylenes. Table 22.2 shows the comparison. 

All polymers do, however, undergo second-order transitions, which occur when the volume-temperature curve at a given pressure undergoes a discontinuity but not a volume change at constant temperature. The most important of these transitions is the glass transition temperature Tg. Figure 2-9 shows the occurrence of such a point for atactic polypropylene. Table 2-2 [21] lists Tg... 

Table 3 shows the apparent melting temperature, Tm, the crystallinity temperature, Tc, the apvparent enthalpy, AH, and the aystallinity index, a, obtained from DSC measurements for polypropylenes PFD, PP-CR154, PP-CR402 and PP-CR546. AU the values measured are in accordance with data reported in the literature (Karger-Kocsis, 1995 Pasquini, 2005). Tm decreased with the peroxide content while Tc and a remained constant. The evolution of Tm with the peroxide content underwent the same trend as that of the Mw with peroxide content among the controlled-rheology polypropylenes (Table 1). However, the present results stood up for the no enhancement of either the aystaUine degree or the crystallinity...

Addition of crosslinking agents facilitates crosslinking of polypropylene. Table 5.31. During irradiation, thermal-oxidative stability is reduced because of the radicals formed. 

The mechanical effects of fillers are shown in Table 8 for polypropylene, Table 9 for high density polyethylene and Table 10 for copolymer. 

PROPENE The major use of propene is in the produc tion of polypropylene Two other propene derived organic chemicals acrylonitrile and propylene oxide are also starting materials for polymer synthesis Acrylonitrile is used to make acrylic fibers (see Table 6 5) and propylene oxide is one component in the preparation of polyurethane polymers Cumene itself has no direct uses but rather serves as the starting material in a process that yields two valuable indus trial chemicals acetone and phenol... 

Physical Properties. Table 1 (2) shows that olefin fibers differ from other synthetic fibers in two important respects (/) olefin fibers have very low moisture absorption and thus excellent stain resistance and almost equal wet and dry properties, and (2) the low density of olefin fibers allows a much lighter weight product at a specified size or coverage. Thus one kilogram of polypropylene fiber can produce a fabric, carpet, etc, with much more fiber per unit area than a kilogram of most other fibers. 

Table 3. Stabilization of Polypropylene Fiber by Polymeric HALS ...

Fig. 7. Shear viscosity at 180°C of polypropylene of different molecular weight and distribution vs shear rate (30) see Table 4 for key. Pa-s = 0.1 P...

Table 4. Molecular Weight Characterization Data for Polypropylene Samples ...

Table 6 shows the sales estimates for principal film and sheet products for the year 1990 (14). Low density polyethylene films dominate the market in volume, followed by polystyrene and the vinyls. High density polyethylene, poly(ethylene terephthalate), and polypropylene are close in market share and complete the primary products. A number of specialty resins are used to produce 25,000—100,000 t of film or sheet, and then there are a large number of high priced, high performance materials that serve niche markets. The original clear film product, ceUophane, has faUen to about 25,000 t in the United States, with only one domestic producer. Table 7 Hsts some of the principal film and sheet material manufacturers in the United States.

Olefin Polymers. The flame resistance of polyethylene can be increased by the addition of either a halogen synergist system or hydrated fillers. Similar flame-retarder packages are used for polypropylene (see Olefin polymers). Typical formulations of the halogen synergist type are shown in Table 15 the fiUer-type formulations are in Table 16. 

Table 16. Hydrated Filler Systems for Polyethylene and Polypropylene ...

The majority of spunbonded fabrics are based on isotactic polypropylene and polyester (Table 1). Small quantities are made from nylon-6,6 and a growing percentage from high density polyethylene. Table 3 illustrates the basic characteristics of fibers made from different base polymers. Although some interest has been seen in the use of linear low density polyethylene (LLDPE) as a base polymer, largely because of potential increases in the softness of the final fabric (9), economic factors continue to favor polypropylene (see OlefinPOLYMERS, POLYPROPYLENE). 

Polypropylene polymers are typically modified with ethylene to obtain desirable properties for specific applications. Specifically, ethylene—propylene mbbers are introduced as a discrete phase in heterophasic copolymers to improve toughness and low temperature impact resistance (see Elastomers, ETHYLENE-PROPYLENE rubber). This is done by sequential polymerisation of homopolymer polypropylene and ethylene—propylene mbber in a multistage reactor process or by the extmsion compounding of ethylene—propylene mbber with a homopolymer. Addition of high density polyethylene, by polymerisation or compounding, is sometimes used to reduce stress whitening. In all cases, a superior balance of properties is obtained when the sise of the discrete mbber phase is approximately one micrometer. Examples of these polymers and their properties are shown in Table 2. Mineral fillers, such as talc or calcium carbonate, can be added to polypropylene to increase stiffness and high temperature properties, as shown in Table 3. 

Random insertion of ethylene as comonomer and, in some cases, butene as termonomer, enhances clarity and depresses the polymer melting point and stiffness. Propylene—butene copolymers are also available (47). Consequendy, these polymers are used in apphcations where clarity is essential and as a sealant layer in polypropylene films. The impact resistance of these polymers is sligbdy superior to propylene homopolymers, especially at refrigeration temperatures, but still vastiy inferior to that of heterophasic copolymers. Properties of these polymers are shown in Table 4. 

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