Powdered polyamide

The anionic polymerization of lactams represents the only suitable method to prepare powdered PA materials. One advantage here is that the polymerization process is fast, even at temperatures much below than the melting temperature of the synthetized polyamide. Powdered PAs have a number of applications, including flame spraying, electrostatic coating and paste preparation (mainly for cosmetics). 

Polymerization and copolymerization proceed in organic liquids, which act as precipitants for the PA being formed. For this, nonpolar solvents such as xylene, ethylbenzene [82], n-heptane [83], various gasoline fractions [83] and oils are generally applied. In most cases, the processes used resemble dispersion polymerization (when the monomer is soluble in the medium), although suspension polymerization (when the lactam is only incompletely soluble in the given medium) may also be used. 

In recent years, many of the processes initiated by Synhydride (soluble in nonpolar media) and aliphatic or aromatic (di)isocyanates [82], carbodiimides [84] or N-lauroyl-e-caprolactam [83] have been studied, although the first initiation system was composed of the sodium salt of CL and CO2 [85]. 

The polymerization requires a higher concentration of the initiation system and a different initiator/activator ratio when compared to bulk polymerization. The resultant PA has a high molar mass, and no marked side reactions accompany the polymerization, due mainly to the low polymerization temperatures utilized, which mainly range between 90 and 130°C [82]. 

A very rapid initiation system-namely, a combination of the sodium salt of CL and cydohexyl isocyanate [87]-made it possible to shorten the polymerization times to lOmin (at 155 °C). The polyisobutylene (PIB) oils used partially dissolved 

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Only a few commercial uses for TDA per se have been found. In epoxy curing appHcations, 2,4- I DA has been used as a component of a eutectic mixture with short chain aUphatic glycidal ether resins (46) as well as by itself (46,47) TDA (46) and single isomers (47) are also used as amine curatives. TDA can be used as a chain extender in polyurethanes (48,49). TDA is cited as a monomer in making aromatic polymers with unique properties, eg, amorphous polyamides (50), powdered polyamides (51), and low melting, whoUy aromatic polyamides (52). 

The generation of active centers on powdered polyamide backbone by high energy irradiation or by chemical reactions is reported in the literature. 

Quantitative or semi-quantitative determination of analytes by SPME requires working within the linear dynamic range of the SPME fiber. If the linear dynamic range is exceeded, the extracted amount of analyte will not reflect the amount of analyte in the sample. Figure 2 shows the normalized peak areas for the headspace extractions of different amounts of powdered polyamide 6.6 [67]. The extraction time and temperature were 45 min and 80 °C. Under the given conditions, the dynamic range of the PDMS/DVB fiber was linear if the polyamide sample size was between 1 and 100 mg. For the... 

TLC is a simple, inexpensive technique that can be effectively used for the analysis of natural products including quassinoids. In addition to being used as an analytical tool, TLC is also used to partially purify and isolate quassinoids as in colunui chromatography. The effectiveness of the separation depends on the extract, choice of mobile phase, and absorption layer such as silica gel, alumina, cellulose powder, polyamides, and ion-exchangers supported on glass or metal plate. Rf values or the retention factor is commonly used to describe chromatographic behavior and is defined as distance moved of a particular spot divided by the distance moved by the solvent front. Comparative Rf values can be utilized to analyze extracts both qualitatively and quantitatively. Quassinoids give red color on TLC plate when sprayed with concentrated sulfuric acid and brown when heated. Various stationary and mobile phases have been utilized in the separation of quassinoids, viz. ... 

Evrard et al. [195] evaluated powdered polyamides of different types as sani-reinfoicing fillers in carboxylated nitrile rubber. They evaluated the filler vulcanizates for tensile properties, tear strength, coefficient of friction, filler matrix adhesion, and swelling in various fluids. 

Food dyes are extracted from foods by using adsorbents such as wool fibers, powdered polyamide, cellulose exchange resins, or RP cartridges (Sep-pak Cis), which is the method of choice for a fast and easy cleanup. After desorption of the colorants and filtration, the solution is analyzed by either ion-pair or reversed-phase LC. Ion-pair LC uses water acetone mixtures (80 20) with tetrabutylammonium chloride added as ion-pair agent and Cig or Cg columns. As for RPLC, a combination of phosphate buffer methanol, water acetonitrile, and methanokacetone are commonly used. Gradients are used to allow the separation of the different classes of... 

The obtainment of fine powders of PCL, poly(co-laurolactam), and their copolymers has attracted relevant attention in recent years for possible commercial utilizations in several fields. Cosmetic formulations, coating and graphic art applications, protein or enzyme immobilization techniques, rotational molding and sintering processes, and filtration devices in food and beverage industry are the major industrial fields where powdered polyamides are currently applied. Their use as stationary phase in chromatography has also been envisaged and introduced for some specific systems. 

Although Synhydride (resp. Dilactamate) is not considered to be a normal initiator, it is today being used in industrial polymerization casting to some extent (private confidential communication). Recently, Synhydride has been applied, in combination with diisocyanate activators, for the preparation of powder polyamides (see Section 7.10). 

Synthetic Fiber and Plastics Industries. In the synthetic fibers and plastics industries, the substrate itself serves as the solvent, and the whitener is not appHed from solutions as in textiles. Table 6 Hsts the types of FWAs used in the synthetic fibers and plastic industries. In the case of synthetic fibers, such as polyamide and polyester produced by the melt-spinning process, FWAs can be added at the start or during the course of polymerization or polycondensation. However, FWAs can also be powdered onto the polymer chips prior to spinning. The above types of appHcation place severe thermal and chemical demands on FWAs. They must not interfere with the polymerization reaction and must remain stable under spinning conditions. 

In 1954 the surface fluorination of polyethylene sheets by using a soHd CO2 cooled heat sink was patented (44). Later patents covered the fluorination of PVC (45) and polyethylene bottles (46). Studies of surface fluorination of polymer films have been reported (47). The fluorination of polyethylene powder was described (48) as a fiery intense reaction, which was finally controlled by dilution with an inert gas at reduced pressures. Direct fluorination of polymers was achieved in 1970 (8,49). More recently, surface fluorinations of poly(vinyl fluoride), polycarbonates, polystyrene, and poly(methyl methacrylate), and the surface fluorination of containers have been described (50,51). Partially fluorinated poly(ethylene terephthalate) and polyamides such as nylon have excellent soil release properties as well as high wettabiUty (52,53). The most advanced direct fluorination technology in the area of single-compound synthesis and synthesis of high performance fluids is currently practiced by 3M Co. of St. Paul, Minnesota, and by Exfluor Research Corp. of Austin, Texas. 

Available Forms. Phthalocyanines are available as powders, in paste, or Hquid forms. They can be dispersed in various media suitable for aqueous, nonaqueous, or multipurpose systems, eg, polyethylene, polyamide, or nitrocellulose. Inert materials like clay, barium sulfate, calcium carbonates, or aluminum hydrate are the most common soHd extenders. Predispersed concentrates of the pigments, like flushes, are interesting for manufacturers of paints and inks (156), who do not own grinding or dispersing equipment. Pigment—water pastes, ie, presscakes, containing 50—75% weight of water, are also available. 

Polyamides. Coating powders based on polyamide resins have been used in fusion-coating processes for along time (1). Nylon-11 [25587-80-8] h.2LS been used almost exclusively however, more recently, coating powders also have been sold based on nylon-12 [24937-16-4]. The properties of these two resins are quite similar. Nylon-6 [25038-54-4] and nylon-6,6 [32131 -17-2] are not used because the melt viscosities are too high. 

Epoxy-polyamide resin with a powdered oxide filler... 

NOTE Early polyalkylene polyamide antifoam formulations (1940s) developed by Dearborn Chemical Company (now G.E. Betz, formerly Hercules Betz-Dearborn) employed protective colloid technology. These products generally were in powder or briquette form. 

We studied the polyamidation of nylon 4,6, and varied the reaction time, reaction temperature, partical size, starting molecular weight, and type of reactor gas. At the same time we looked at the molecular weight broadening and the degradation with colour formation. In order to have good heat and mass transfer the reactions were mainly conducted on fine powder in a fluidized bed reactor and with dry nitrogen as carrier gas. 

Polyamide powder showed to be highest recovery adsorbent for quantitative determination, compared to other resins. The isolated colorants were analyzed by... 

The first sample is a reactive poly(tetrafluoroethylene)/polyamide 6 (PTFE/ PA) blend [43]. When mixing PTFE micro-powder and PA in an extruder at about 280°C, relatively large PTFE particles occur in the final product because of immiscibility. By irradiation with electrons in air reactive groups in the PTFE powder are formed. These functionalised particles react with the molten PA in the extruder, and graft copolymers are formed, improving the compatibility of the components. At the same time a decrease in PTFE particle size proportional to the irradiation dose can be observed, and a PTFE/PA compound with better properties is produced. 

The most commonly used liquid thermoplastics are plastisols (pastes of PVC with a high content of plasticizers). There is also a polyamide of very low consumption. Some of the processes can be applied to powders in suspension. 

SUPreM, Plytron, Quadrax (Gurit Suprem) consolidated tapes or fabrics are made from continuous fibres impregnated with thermoplastic powder. The fibres can be glass, aramid, carbon, steel and the matrices are polyethylene, polypropylene, polyamide, PPS, polyetherimide, PEEK, thermoplastic polyimide, or fluorothermo-plastic. High levels of fibres can be obtained, 65% in volume, for example. 

Several polymer-related uses of brassylic acid (BA) have been investigated. For example, a BA/l,3-butanediol/lauric acid oligomer is an effective plasticizer for poljrvinyl chloride,[6] BA/ethylene glycol and BA/propylene glycol polymers function as polyester based polyurethane elastomers,[7] and BA has been patented as a cross-linker for glycidyl methacrylate copolymer powder coatings.[8] However, the most detailed studies have involved polyamides selected data from these studies are summarized in Table I. 

EMA copolymer Acrylic Polyester fiber Polyamide copolymer with polyether/polyester Epoxy and PVC powders Nylon-6 Acrylic fibers Poromeric film Vinyl Vinyl PVC... 

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