Metal-insertion

This reaction requires a metal complex that is coordinatively unsaturated and provides another way for bonding of reactant ligands to a metal.Insertion ... 

One of the ways to increase the bearing strength of a joint is to use metal inserts as in the shimmed joint of Figure 7-40. Another way is to thicken a section of the composite laminate as in the reinforced-edge joint in Figure 7-40. 

An alternative approach for injection molding is the use of a rotary table injection machine. This type of machine uses the multistation concept, each station having a single cavity mold generally using a point gating/ injection point as previously mentioned. Consider a rotary table machine with eight stations, station one would be the injection station and station seven would be the unload and load metal insert station. This type of process has been successfully used for different types of lip type rotary shaft seals where more expensive elastomers are used and waste needs to be kept to a minimum. 

Access of air and water will also affect the corrosion rate. Metal inserts in corrosive plastics are most actively attacked at the plastic/metal/air interfaces with certain metals, notably aluminium titaniumand stainless steel, crevice effects (oxygen shielding and entrapment of water) frequently accelerate attack. Acceleration of corrosion by bimetallic couples between carbon-fibre-reinforced plastics and metals presents a problem in the use of these composites. 

Germanium phthalocyanine (PcGeCl2), similar to silicon phthalocyanine, is prepared from isoindolinediimine and germanium(IV) chloride in quinoline.105,1 10,1 53 Besides this common procedure, it can also be prepared by metal insertion into PcH2 starting from germanium(IV) chloride in dimcthylformamidc.141 The diol can be obtained by reprecipitation from concentrated sulfuric acid. 

Palladiumphthalocyanine (PcPd) can be synthesized from phthalimide, ammonium molyb-date(VI), urea and palladium(II) chloride in nitrobenzene.285 Peripherally substituted palladium phthalocyanine is prepared by the reaction of phthalonitrile286 or isoindolinediimine114,117 and palladium(II) acetate in 2-(dimethylamino)ethanol. Also a metal insertion into metal-free phthalocyanine in dimethylfonnamide starting from bis(triphenylphos-phane)palladium(II) chloride has been performed.141,287... 

The preparation of silver phthalocyanine (PcAg) is carried out by metal insertion into metal-free phthalocyanine from silver(I) nitrate. The reaction is performed in dimethylformamide291 or in a mixture of 1,2-dichloroethane, sodium acetate and acetic acid.231... 

Zinc phthalocyanine (PcZn) is prepared from phthalonitrile in solvents with a boiling point higher than 200 C, e.g. quinoline277,278 or 1-bromonaphthalene,137 or without solvent in a melt of phthalonitrile.83,116 The zinc compound normally used is zinc(ll) acetate or zinc powder. The reaction of zinc(II) acetate with phthalic acid anhydride, urea and ammonium mo-lybdate(VI) is also successful.262 The metal insertion into a metal-free phthalocyanine is carried out in an alcohol (e.g.. butan-l-ol).127,141,290 This reaction can be catalyzed by an alkali metal alkoxide.112,129... 

Frequently, a product becomes loaded when it is subjected to a defined deflection. The actual load then is a result of the structural reaction of the product to the applied strain. Unlike directly applied loads, strain-induced loads are dependent on the modulus of elasticity and, with TPs, will generally decrease in magnitude over time. Many assembly and thermal stresses could be the result of strain-induced loads. They include metal insert press fits in the plastic and clamping or screw attachments. 

Fourth, molded-in metal should be avoided whenever alternate methods will accomplish the desired objective. If it is essential to incorporate such inserts, they should be shaped so that they will present no sharp inside comers to the plastic. The effect of the sharp edges of a metal insert would be the same as explained in the first point above, namely, brittleness and stress concentration can occur. The cross-section that surrounds a metal insert should be heavy enough that it will not crack upon cooling. A method of minimizing cracking around the insert is to heat the... 

A common use is with a plastic hub or boss accepting either a plastic or metal insert. The press fit operation tends to expand the hub creating a tensile or hoop stress. If the interference is too great, a very high strain and stress will develop. The plastic product will (1) fail immediately by developing a crack parallel to the axis of the hub to relieve the stress, a typical hoop stress failure, (2) survive assembly but fail prematurely when the product is in use for a variety of... 

Molded-in insert If metal inserts are to be molded into a plastic product consideration should be given to wall thickness around the insert (Table 3-18) and their shape. The shape should present no sharp edges to the plastic, since the effect of the edges would be similar to that of a notch. A knurled insert... 

Metal inserts are usually not feasible, because thin walls are not sufficiently strong to hold inserts, particularly if thermal expansion and contraction of the product takes place in service. Figure 3-40 shows a method of holding metal fittings. It may be desirable to in-... 

When metal inserts require hermetic sealing, consider coating them with a flexible elastomer such as an RTV rubber, polyurethane, or epoxy system. A second method is to design an annular space or reservoir at one end of the insert from which to dispense the flexible elastomers to effectively create a hermetic seal. Flexible sealants are also used to compensate for differences in the thermal coefficient of expansion between metal and plastic. 

Both shape and design details are heavily process related. The ability to mold ribs, for example, may depend on material flow during a process or on the flowability of a plastic reinforced with glass. The ability to produce hollow shapes depends on the ability to use removable cores, including air, fusible or soluble solids, and even sand. Hollow shapes can also be produced using cores that remain in the product, such as foam inserts in RTM or metal inserts in IM. 

Rybtchinski, B. Milstein, D. Metal insertion into C—C bonds in solution. Angew. Chem. Int. Ed. 1999, 38, 871-883. 

Porphyrin Cofactors Their Advantages and Irreversible Metal Insertion. 215... 

To achieve the synthesis of all the chlorophylls as magnesium chelates we shall return later to the way the magnesium was inserted while simultaneously the metals iron, cobalt and nickel were prevented from entering the chlorin centre despite the facts that all these metals bind more strongly to chlorin, and they themselves have to be handled specifically and separately to make coenzymes based on them. We note first the general advantages of metal insertion and once again observe the sophistication of the... 

In contrast, methyl cyclopropenone is reported283) to react with the Pt-olefin complex 455 at low temperature with replacement of the olefin ligand. In the resulting complex 456 the cyclopropenone interacts with the central atom via the C /C2 double bond according to spectroscopic evidence284). At elevated temperatures a metal insertion to the C1<2)/C3 bond occurs giving rise to 457. Pt complexes of a similiar type were obtained from dimethyl and diphenyl cyclopropenone on reaction with 455 and their structures were established by X-ray analysis285). 

Many types of component are produced by this method with little difficulty, but, unless very extreme measures of mould design are employed, some components of an intricate nature defy moulding by compression techniques. The reasons are usually the difficulty or cost of preparing a suitable blank shape, the impossibility of ensuring flow of the required amount of rubber into the cavity, or the inability to retain loose metal inserts for bonding in their correct positions. 

An injection machine can be equipped with a two-sided shuttle table using either 1 or 2 complete moulds. Applications are in production using a common top mould plate and two identical lower plates. Products with metal inserts or which require unloading and mould cleaning times as long as cure times are best suited to this process. 

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