Polyamides physical properties

In the area of moleculady designed hot-melt adhesives, the most widely used resins are the polyamides (qv), formed upon reaction of a diamine and a dimer acid. Dimer acids (qv) are obtained from the Diels-Alder reaction of unsaturated fatty acids. Linoleic acid is an example. Judicious selection of diamine and diacid leads to a wide range of adhesive properties. Typical shear characteristics are in the range of thousands of kilopascals and are dependent upon temperature. Although hot-melt adhesives normally become quite brittle below the glass-transition temperature, these materials can often attain physical properties that approach those of a stmctural adhesive. These properties severely degrade as the material becomes Hquid above the melt temperature. 

Nylon-6,6 [32131 -17-2J is a tough, translucent white, semiciystalline, high melting (T , = 265 C) material. The common physical properties ate shown in Table 9, and principal producers woddwide in Table 10, for nylon-6,6 and other commercial polyamides. 

Nylon-6,6 and nylon-6 have competed successfully ia the marketplace siace their respective commercial iatroductioas ia 1939 and 1941, and ia the 1990s share, about equally, 90% of the total polyamide market. Their chemical and physical properties are almost identical, as the similarity of their chemical stmcture might suggest the amide functions are oriented ia the same directioa aloag the polymer chain for ayloa-6, but are altematiag ia directioa for ayloa-6,6. 

Cycloahphatic diamines which have reacted with diacids to form polyamides generate performance polymers whose physical properties are dependent on the diamine geometric isomers. (58,74). Proprietary transparent thermoplastic polyadipamides have been optimized by selecting the proper mixtures of PDCHA geometric isomers (32—34) for incorporation (75) ... 

Nearly all of the polymers produced by step-growth polymerization contain heteroatoms and/or aromatic rings in the backbone. One exception is polymers produced from acyclic diene metathesis (ADMET) polymerization.22 Hydrocarbon polymers with carbon-carbon double bonds are readily produced using ADMET polymerization techniques. Polyesters, polycarbonates, polyamides, and polyurethanes can be produced from aliphatic monomers with appropriate functional groups (Fig. 1.1). In these aliphatic polymers, the concentration of the linking groups (ester, carbonate, amide, or urethane) in the backbone greatly influences the physical properties. 

Diamantane-based polymers are synthesized to take advantage of their stiffness, chemical and thermal stability, high glass transition temperature, improved solubility in organic solvents, and retention of their physical properties at high temperatures. All these special properties result from their diamantane-based molecular structure [90]. Polyamides are high-temperature polymers with a broad range of applications in different scientific and industrial fields. However, their process is very difficult because of poor solubility and lack of adequate thermal stability retention [90]. Incorporation of 1,6- or... 

We have prepared a synthetic protein polymer based on repeat sequence Lys-25 to investigate the effect of uniformity of crosslink placement on the physical properties of a polymer hydrogel (Figure 1). The design of Lys-25 reflects two essential structural requirements for formation of polymer hydrogels (1) a flexible, hydrated (polyamide) backbone and... 

The materials used in nonwoven fabrics include a single polyolefin, or a combination of polyolefins, such as polyethylene (PE), polypropylene (PP), polyamide (PA), poly(tetrafluoroethylene) (PTFE), polyvinylidine fluoride (PVdF), and poly(vinyl chloride) (PVC). Nonwoven fabrics have not, however, been able to compete with microporous films in lithium-ion cells. This is most probably because of the inadequate pore structure and difficulty in making thin (<25 /rm) nonwoven fabrics with acceptable physical properties. 

As indicated in Table I, most properties of polyamide derivatives of BA, nylons 13, and 13/13, are predictable from properties of commercial engineering plastics such as nylon-11 and nylon-6/10 -- the BA based nylons are have lower moduli and most physical properties are unexceptional.[9,10] However, the BA based nylons have one exceptional property -- their very low capacity to absorb moisture. This property suggests that these materials may be less affected by water plasticization than other nylons, and it has attracted interest in developing BA-based nylons commercially. Development has been impeded by the fact that BA is not produced on a sufficient scale to make it cost-competitive, and apparently the attractive markets are not large enough to justify investment in development of BA processes, creating a chicken-or-egg" problem. 

Thermal stability as measured by these ramped TGA experiments of the sort previously described are not the definitive test of a polymer s utility at elevated temperature. Rather, for a polymer to be useful at elevated temperatures, it must exhibit some significant retention of useful mechanical properties over a predetermined lifetime at the maximum temperature that will be encountered in its final end use application. While many of the bisbenzocyclobutene polymers have been reported in the literature, only a few have been studied in detail with regards to their thermal and mechanical performance at both room and elevated temperatures. Tables 7-10 show some of the preliminary mechanical data as well as some other physical properties of molded samples of polymers derived from amide monomer 32, ester monomer 40, diketone monomer 14 and polysiloxane monomer 13. The use of the term polyamide, ester etc. with these materials is not meant to imply that they are to be regarded as merely modified linear thermoplastics. Rather, these polymers are for the most part highly crosslinked thermosets. 

Synthesis of telechelic oligomers usable in the synthesis of multiblock polyesters or polyamides with different segments presenting specific physical properties... 

Two most common families of RO membranes, based on the type of polymer backbone, are cellulose acetate and polyamide.12 Membranes made from these polymers differ in many respects, including performance, physical properties, structure and the manner in which they are created. These aspects are discussed below. 

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