Bonding polypropylene

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 stability of such HCP is not high. For instance, although the heparin (ionic bonds) — ternary ammonium salts (covalent bonds) — polypropylene associate is not actually affected by distilled water, the 3 hours storage of the product in blood plasma reduces the surface concentration of heparin to 30% of its initial value65. It is noteworthy that heparin is very effectively eluted by solutions of y-globuline (Table 7)65>. 

This adhesive was used for bonding polypropylene to itself or to plastics, wood, and paper. Copolymerization of butadiene with dichloroallyl levulinate... 

Includes olefin film, olefin fiber, and spun-bonded polypropylene. 

Chidambaram A. Davis H and Batra S K, Strength loss in thermally bonded polypropylene fibers . Joint INDA-TAPPI Conference, INTC 2000, International Non-wovens Technical Conference, Book of Papers, Dallas USA, 2000, 19.0-19.23. 

N-(n-Butyl)-3-aminopropyltrimethoxysilane 3-Glycidyloxypropyltriethoxysilane primer, substrates difficult-to-bond Polypropylene wax, maleic anhydride-modified primer, surface repeated use food-contact Polymethylmethacrylate/poly (trimethoxysilylpropyl) methacrylate copolymer... 

Figure 14.34 Heat release rate and total heat release for maleic anhydride bonded polypropylene with various concentrations of exfoliated montmorillonite added.

Silicone rubber is difficult to bond with cyanoacrylates. The adhesive does not wet the surface properly without special surface treatment, due to the very low surface energy, and therefore will not bond. Polypropylene (PP), polyethylene (PE), polytetrafluoro ethylene (PTFE) and acetal plastics and Santoprene rubber also fall into this category and cannot be bonded without prior surface preparation. 

This calculation is only applicable to a Newtonian fluid and an isotropic spreading pattern. Hirt et al. obtained straight lines in plots of the type described above in experiments with samples of spun-bonded nonwoven mats of polypropylene and polyester using a Newtonian resin as fluid, A center hole was precut in the mat at the point where the resin was injected. Examples of permeability values reported are on the order of (2-4) x 10 m for epoxy resins flowing in spun-bonded polypropylene and polyester nonwovens and (0.3-4.5) X 10" ° m for mats of chopped glass fiber. The permeabilty increases with increasing resin volume fraction. 

The mounting cup (ferrule for botde valves) mechanically joins the valve to the container. The mounting cup may be made from a variety of materials, but is typically tin-plated steel coated on the underside. It contains the gasket which provides the seal. Soft gasketing material is appHed wet and bonded in place or, more frequently in larger cans, cut mbber, polyethylene, or polypropylene gaskets are used. 

Olefin fiber is an important material for nonwovens (77). The geotextile market is stiU small, despite expectations that polypropylene is to be the principal fiber in such appHcations. Disposable nonwoven appHcations include hygienic coverstock, sanitary wipes, and medical roU goods. The two competing processes for the coverstock market are thermal-bonded carded staple and spunbond, both of which have displaced latex-bonded polyester because of improved strength, softness, and inertness. 

In extmsion coating a polymer is extmded from a slot die into the nip of two roUs where it is bonded to a substrate under pressure (Fig. 6). A corona discharge may be appUed to the substrate just prior to the nip to enhance adhesion. Polyethylene or ionomer are the most common resins used in extmsion coatings. They provide improved moisture barrier (on paper), or sealabUity (on foU, polypropylene, or polyester). When a second substrate is introduced to the nip, laminated stmctures may be produced. 

Lamination Inks. This class of ink is a specialized group. In addition to conforming to the constraints described for flexo and gravure inks, these inks must not interfere with the bond formed when two or more films, eg, polypropylene and polyethylene, are joined with the use of an adhesive in order to obtain a stmcture that provides resistance properties not found in a single film. Laminations are commonly used for food applications such as candy and food wrappers. Resins used to make this type of ink caimot, therefore, exhibit any tendency to retain solvent vapor after the print has dried. Residual solvent would contaminate the packaged product making the product unsalable. 

Some of the most difficult heterophase systems to characterize are those based on hydrocarbon polymers such as mbber-toughened polypropylene or other blends of mbbers and polyolefins. Eecause of its selectivity, RuO staining has been found to be usehil in these cases (221,222,230). Also, OsO staining of the amorphous blend components has been reported after sorption of double-bond-containing molecules such as 1,7-octadiene (231) or styrene (232). In these cases, the solvent is preferentially sorbed into the amorphous phase, and the reaction with OsO renders contrast between the phases. 

The use of TAG as a curing agent continues to grow for polyolefins and olefin copolymer plastics and mbbers. Examples include polyethylene (109), chlorosulfonated polyethylene (110), polypropylene (111), ethylene—vinyl acetate (112), ethylene—propylene copolymer (113), acrylonitrile copolymers (114), and methylstyrene polymers (115). In ethylene—propylene copolymer mbber compositions. TAG has been used for injection molding of fenders (116). Unsaturated elastomers, such as EPDM, cross link with TAG by hydrogen abstraction and addition to double bonds in the presence of peroxyketal catalysts (117) (see Elastol rs, synthetic). 

Covers for the battery designs in Figures 1 and 2 are typically molded from materials identical to that of the respective case, and vent plugs are frequentiy made of molded polypropylene. Other combinations are possible, eg, containers molded of polyethylene or polypropylene may be mated with covers of high impact mbber for use in industrial batteries. After the cover is fitted over the terminal post, it is sealed onto the case. The cover is heat bonded to the case, if it is plastic it is sealed with an epoxy resin or other adhesive, if it is vulcanized mbber. Vent caps are usually inserted into the cover s acid fiU holes to faciHtate water addition and safety vent gasses, except for nonaccessible maintenance-free or recombinant batteries. In nonaccessible batteries, the vent is fabricated as part of the cover. 

Polypropylene can be fabricated by almost any process used for plastics (see Plastics processing). The extmsion of pipe and injection mol ding of fittings present no unusual problem. However, there is no way to bond the fittings to the pipe except by remelting the polymer, which is impractical on most constmction sites. The resin can be reinforced by glass fibers, mineral fillers, or other types of fillers and can be pigmented readily. 

This conceptual link extends to surfaces that are not so obviously similar in stmcture to molecular species. For example, the early Ziegler catalysts for polymerization of propylene were a-TiCl. Today, supported Ti complexes are used instead (26,57). These catalysts are selective for stereospecific polymerization, giving high yields of isotactic polypropylene from propylene. The catalytic sites are beheved to be located at the edges of TiCl crystals. The surface stmctures have been inferred to incorporate anion vacancies that is, sites where CL ions are not present and where TL" ions are exposed (66). These cations exist in octahedral surroundings, The polymerization has been explained by a mechanism whereby the growing polymer chain and an adsorbed propylene bonded cis to it on the surface undergo an insertion reaction (67). In this respect, there is no essential difference between the explanation of the surface catalyzed polymerization and that catalyzed in solution. 

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