Amorphous polyamides properties

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 use of other materials as the central layer of the barrier laminate is, of course, feasible. Obvious candidates for this application include the high barrier amorphous polyamides (Chapter 5 (50)) and the liquid crystalline polyesters (Chapter 3(57)) which either develop slightly improved barriers under elevated relative humidity conditions or at least do not lose barrier properties. No reports are yet available concerning the performance of such structures. 

The structure of an amorphous polyamide prepared from hexamethylenediamine and isophthalic/tere-phthalic acids was modified in order to determine the effect of chemical structure on the oxygen permeation properties. The greatest increase in permeation was obtained by lengthening the aliphatic chain. Placement of substituents on the polymer chain also led to increased permeation. Reversal of the amide linkage direction had no effect on the permeation properties. Free volume calculations and dielectric relaxation studies indicate that free volume is probably the dominant factor in determining the permeation properties of these polymers. 

Selar PA, poly(hexamethylene isophthalamide/terephthalamide) or 6-I/T (the diamine components are listed first, then the diacid components), is an amorphous polyamide which is marketed by Du Pont. As shown in Figure 1, it has unique properties for a barrier resin in that the oxygen barrier properties actually... 

Through systematic modification of the polymer backbone, the effects of chemical structure upon the oxygen permeation properties of aliphatic-aromatic amorphous polyamides were determined. In this class of polymers, the greatest effects were obtained by alteration of the chain length and disruption of the amide hydrogen bonding by N-alkylation. It is remarkable that reversal of the amide linkage has no effect whatsoever on the permeation properties of the examples studied. 

To improve the oxygen barrier properties of PA-6 (and PA-66), high T barrier type amorphous polyamides such as PA-6I/6T (Selar PA) have been blended [JCrizan et al., 1989 Blatz,... 

J. G. Dolden. Structure-property relationships in amorphous polyamides. Polymer, 17(10) 875-892, October 1976. 

PA/PC blends have also been compatibilized by block copolymer formation through reactiffli of PA amine end-groups with PC anhydride end-groups (Hathaway and Pyles 1988, 1989). PC phenolic end-groups were anhydride-functionalized by reaction with trimellitic anhydride acid chloride. Extruded blends of PA-6 and PC were characterized by selective solvent extraction and mechanical properties of test parts. An amorphous polyamide could also be compatibilized with PC using this strategy. 

The mechanical properties of the in situ composites are further considered. The tensile modulus of the blend based on an amorphous polyamide (PA) and the aromatic co-polyesther HBA/HNA by Celanese are reported (see fig. 16, 17) (30). Both the... 

Yoo, Y., Cui, L., Yoon, P.J., and Paul, D.R. (2010) Morphology and mechanical properties of rubber toughened amorphous polyamide/MMT nanocomposites. Micromolecules,... 

The highly intractable chemical stmcture vMch. inq)arts the outstanding mechanical properties also makes the PATs very difficult to process (4, 5). In the ftilly imidized form PAI is not processable hence a poly(amic acid) (PAA) precursor is the usual form in which they are supplied and bricated. The precursors themselves have very hi viscosities in the melt state and hence the flow characteristics tend to be very poor. Semicrystalline and amorphous polyamides (6) and aromatic sulfone polymers such as poly(phenylene sulfide), poly(ether sulfone) and polysulfone (7) have been blended with the precursor to PAI, to obtain better flow characteristics. 

Kim, J.K., Park, S.H., O, H.T., and Jeon, H.K. (2001) The effect of weld-lines on the morphology and mechanical properties of amorphous polyamide/poly(ethylene-ran-propylene) blend with various amounts of an in situ compatibilizer. Polymer, 42, 2209-2221. 

Y. Yoo and D. R. Paul. Effect of organoclay structure on morphology and properties of nanocomposites based on an amorphous polyamide. Polymer,... 

Mechanical properties of injection molded blends of thermoplastic polymers and thermotropic LCP materials were first reported by Siegmann et al. (1985) with reference to a blend of an amorphous polyamide and Vectra A. In particular, the modulus was found to undergo a 1.5-fold increase by addition of 25 % of LCP, and elcHigation at break underwent a dramatic decrease with only 5 % of LCP. These... 

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. 

Because of the capacity to tailor select polymer properties by varying the ratio of two or more components, copolymers have found significant commercial appHcation in several product areas. In fiber-spinning, ie, with copolymers such as nylon-6 in nylon-6,6 or the reverse, where the second component is present in low (<10%) concentration, as well as in other comonomers with nylon-6,6 or nylon-6, the copolymers are often used to control the effect of sphemUtes by decreasing their number and probably their size and the rate of crystallization (190). At higher ratios, the semicrystalline polyamides become optically clear, amorphous polymers which find appHcations in packaging and barrier resins markets (191). 

In addition to the semicrystalline nylons, which comprise the vast majority of commercial resins, nylon is also available in an amorphous form that gives rise to transparency and improved toughness at the expense of high temperature properties and chemical stress crack resistance. Table 2 shows the properties of some different polyamide types. 

Cycloahphatic diamines react with dicarboxyUc acids or their chlorides, dianhydrides, diisocyanates and di- (or poly-)epoxides as comonomers to form high molecular weight polyamides, polyimides, polyureas, and epoxies. Polymer property dependence on diamine stmcture is greater in the linear amorphous thermoplastic polyamides and elastomeric polyureas than in the highly crosslinked thermo set epoxies (2—4). 

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