Polyamide casting

Polyamides. Metallized plastics [40] have been obtained from metal chelates of nylon 4 and nylon 6 by soaking a film of the polyamides cast from formic... 

The difference between standard vacuum casting and nyion casting are the mold temperatures, which are in the temperature range from 140 to 160 °C in polyamide casting. This means that higher quality silicones have to be used for the mold. 

When drawdown is high, the film may be uniaxially oriented and the properties of the final film isotropic. In the manufacture of strapping tape this effect is accentuated. If the cast or quenched film is to be used to feed an orientation tine, additional attention must be given to the amorphous—crystalline nature of the film ia the draw processes so that maximum strength can be achieved and uniform gauge and optical quality maintained. Slot casting is used for the orientation of these resins, polyesters, polyamides, and a variety of others. 

An important development of polymerisation casting is that of reaction injection moulding. Developed primarily for polyurethanes (and discussed further in Chapter 27), the process has also found some use with polyamides and with epoxide resins. 

The predominant RO membranes used in water applications include cellulose polymers, thin film oomposites (TFCs) consisting of aromatic polyamides, and crosslinked polyetherurea. Cellulosic membranes are formed by immersion casting of 30 to 40 percent polymer lacquers on a web immersed in water. These lacquers include cellulose acetate, triacetate, and acetate-butyrate. TFCs are formed by interfacial polymerization that involves coating a microporous membrane substrate with an aqueous prepolymer solution and immersing in a water-immiscible solvent containing a reactant [Petersen, J. Memhr. Sol., 83, 81 (1993)]. The Dow FilmTec FT-30 membrane developed by Cadotte uses 1-3 diaminobenzene prepolymer crosslinked with 1-3 and 1-4 benzenedicarboxylic acid chlorides. These membranes have NaCl retention and water permeability claims. 

Membranes UF membranes consist primarily of polymeric structures (polyethersulfone, regenerated cellulose, polysulfone, polyamide, polyacrylonitrile, or various fluoropolymers) formed by immersion casting on a web or as a composite on a MF membrane. Hydrophobic polymers are surface-modified to render them hydrophilic and thereby reduce fouling, reduce product losses, and increase flux [Cabasso in Vltrafiltration Membranes and Applications, Cooper (ed.). Plenum Press, New York, 1980]. Some inorganic UF membranes (alumina, glass, zirconia) are available but only find use in corrosive applications due to their high cost. 

Many polymers have been processed by casting, e.g., acrylics, polystyrene, polyamide (nylon 6), phenolics, PVC/plasticiser. Many of these are used in a pre-polymer form, which polymerise on the casting belt, or the polymerisation can be completed later by application of heat. 

Photodissociation of the polyamides (Figures 4 and 5) was carried out in the solid films. Polymer films (1-2 U m) were cast onto quartz substrates and were exposed to monochromatic 250 nm light from a spectroirradiator. The dissociation of the thymine photodimers was followed by monitoring the absorbance at 270 nm. The results obtained for the polyamide prepared from the reaction of propane diamine and the isomers of the thymine photodimer (cis-syn(17a), cis-anti(17b), and... 

P.Y.110 lends color to polystyrene and styrene containing plastics. It is a suitable candidate for unsaturated polyester and other cast resins, as well as for polyurethane. P.Y.110 is used to an appreciable extent in polypropylene spin dyeing, it is very lightfast in this medium. It is utilized in polyacrylonitrile spin dyeing and sometimes also in polyamide. Its fastness properties, however, especially its lightfastness, do not meet special application conditions (Sec. 1.8.3.8). 

P.B.15 1 is also applied in polystyrene, polyamide, polycarbonate (in which it is heat stable up to 340°C), PUR foam materials, and cast resins. It should be noted, however, that the hardening of cast resins which are based on unsaturated polyesters is usually much retarded. 

P.B.15 3, like stabilized a-Copper Phthalocyanine Blue, markedly affects the hardening of unsaturated polyester cast resins. The list of applications also includes PUR foam materials, office articles, such as colored pencils, wax crayons, and water colors, as well as spin dyeing of polypropylene, polyacrylonitrile, secondary acetate, polyamide, polyester, and viscose. Used in polyester spin dyeing, P.B.15 3 satisfies the thermal requirements of the condensation process (Sec. 1.8.3.8). 1/3 and 1/25 SD samples equal step 7-8 on the Blue Scale for lightfastness. Textile fastnesses, such as stability to wet and dry crocking are perfect. 

Membranes used for the pressure-driven separation processes, microfiltration, ultrafiltration and reverse osmosis, as well as those used for dialysis, are most commonly made of polymeric materials 11. Initially most such membranes were cellulosic in nature. These are now being replaced by polyamide, polysulphone, polycarbonate and a number of other advanced polymers. These synthetic polymers have improved chemical stability and better resistance to microbial degradation. Membranes have most commonly been produced by a form of phase inversion known as immersion precipitation. This process has four main steps (a) the polymer is dissolved in a solvent to 10-30 per cent by mass, (b) the resulting solution is cast on a suitable support as a film of thickness, approximately 100 11 m, (c) the film is quenched by immersion in a non-solvent bath, typically... 

Table 4.51 Neat, reinforced and modified cast polyamides examples of properties...

This process, commonly used with thermosets, is sometimes used for specific thermoplastics such as monomers or pre-polymers of PMMA or polyamide (Nyrim). For the latter, a mix is made just before casting with ... 

Figure II. Effect of film casting conditions on the performance of resulting (a) cellulose acetate (12) and (h) aromatic polyamide-hydrazide membranes. The latter data are tho.se of O. Kutowy and S. Sourirafan (not yet published).

Relationship Between Nodular and Rejecting Layers. Nodular formation was conceived by Maler and Scheuerman (14) and was shown to exist in the skin structure of anisotropic cellulose acetate membranes by Schultz and Asunmaa ( ), who ion etched the skin to discover an assembly of close-packed, 188 A in diameter spheres. Resting (15) has identified this kind of micellar structure in dry cellulose ester reverse osmosis membranes, and Panar, et al. (16) has identified their existence in the polyamide derivatives. Our work has shown that nodules exist in most polymeric membranes cast into a nonsolvent bath, where gelation at the interface is caused by initial depletion of solvent, as shown in Case B, which follows restricted Inward contraction of the interfacial zone. This leads to a dispersed phase of micelles within a continuous phase (designated as "polymer-poor phase") composed of a mixture of solvents, coagulant, and a dissolved fraction of the polymer. The formation of such a skin is delineated in the scheme shown in Figure 11. 

Shell Epon 828 epoxy resin was cured with 13 PHR (parts per hundred of epoxy) of triethylene tetramine as a typical polyamine, 65 PHR of Shell Epon V-15 polyamide as a typical polyamide, or 130 PHR of dodecenyl succinic anhydride as a typical anhydride. Liquid formulations were cast in 5iluminum molds and oven-cured as follows ... 

Brass, bronze, steel, phenolic, acetal, and nylon (natural) had been used with various degrees of success. A specially formulated cast polyamide was recommended, tested, and designed into the function. The part is currently offering a longer wear life, with less moisture pick-up and greater ease of installation. 

A new class of hydrophilic polyamides, poly(tetrahydropyran-2,6-diylimino-carbonyl) 1 was prepared by the anionic polymerization of a bicyclic oxalactam (abbreviated as BOL, 2) 38-42). The resulting polyamide / has glass transition, fusion, and decomposition points at 130,260-285, and 315 °C, respectively, and its membrane can be obtained by casting from a polyBOL solution. The solubility parameter... 

The patents 9 47) filed by Richter and Hoebn in du Pont include many aromatic and heterocyclic condensed polymers for asymmetric reverse osmosis membranes, for example, the condensed polymers 4 from 3-arninobcnzhydrazide, 4-amino-benz-hydrazide (5), isophthaloyl chloride, and terephthaloyl chloride (6). The membranes were cast from polyamide solutions containing 0 3 % LiCl in dimethylacetamide,... 

The polyamide-hydrazide 7 was prepared by solution polymerization in anhydrous dimethylacetamide from terephthaloyl chloride and p-amino-benzhydrazide at ca. 10 °C. The polyamide 8 resulted from the polycondensation of m-phenylenediamine with isophthaloyl chloride at —20 °C, whereas 9 was prepared by the reaction of terephthaloyl chloride with the complex diamine l,3-bis(3-aminobenzamide)benzene at —20 °C. The water flux and salt rejection through these membranes were summarized in Table 5. The polyamide-hydrazide (7) membranes were prepared from polymer solutions containing 6 7% polymer (Mv 3 34,000) by casting on glass plates. The material was placed in an oven for 30 60 min and coagulated in deionized... 

Low molecular weight salts contained in the casting solution of aromatic polyamides much increased the membrane fluxes without a detrimental effect on rejection, as shown in Table 6 S2). 

Reverse osmosis membranes were also prepared from polyamides with pendant carboxamide groups 90). For example, 4,4 -diaminodiphenylmethane-3,3 -dicarbox-amide-isophthaloyl chloride copolymer 33 was dissolved in DMF containing LiCl, cast to 250 p thickness, dried at 100 °C for 15 min, and gelled in ice water to give a membrane with the water flux permeability of 900 1/m2 day and salt rejection of 80% (0.5% NaCl aqueous solution, 30 kg/cm2). After heating the membrane in... 

In comparison with other thermoplastics, polyamides have superior mechanical properties, vibration and chemical resistance, and high dielectric properties. The superior antifrictional characteristics of cast PA-6 allow us to use it for bearings instead of bronze, cast iron, steel, babbit, reinforced phenolic compounds, and other materials. 

Anionic polymerization of s-caprolactam is used to make cast or RIM polyamide-6. Using a premade lactam chain end and a metal catalyst, it proceeds rapidly at 100-160°C, well below the melting temperature of the polymer, Tm 220°C. The propagation differs from anionic propagation of most unsaturated monomers because the growth center at the chain end is not represented by an anionically activated group but by a neutral N-acy-lated lactam, and the anionically activated species is the incoming monomer (Table 2.26). 

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