Physical properties of polyamides

Table IX, Physical Properties of Polyamide-Epoxy Resin Castings...

As with many other polymers, the effects of irradiation on the physical properties of polyamides are highly dependent on the atmosphere during irradiation. For example, irradiation of a high tenacity Nylon 6,6 with an electron beam in an atmosphere free of oxygen showed only a 4% loss of tensile strength after 200 kGy and 35% loss after... 

Water iofiuences the physical properties of polyamides and the effects on nylon 6 and various polyamides have been studied. ... 

The water absorption of PBT in the saturated state is about 0.5 % Maximum water absorption is reached storage in water for 150 days at room temperature [73]. At elevated temperatures, water leads to a loss of strength as a result of hydrolytic degradation of the PBT. The level of water uptake by PBT is very low compared with polyamides, which can absorb between 2 and 8 % of water [50]. The physical properties of polyamides are strongly dependent on the moisture content, which in turn depends on whether they are applied or stored under a dry or wet climate. In contrast, PBT... 

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... 

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. 

Shifting from one interdisciplinary nomenclature to another we can view the bidentate molecule as an amino acid, the amide becomes a peptide and the polyamide a polypeptide or a protein. Hence, we have abjured organic chemistry in favour of biochemistry. Proteins are built up from approximately 20-25 different a-amino acids, the individual order of which decide the chemical and physical properties of a particular protein. Due to a combination of certain attributes of e peptide linkage, and the presence of functionalities enabling the formation of hydrogen bonds, protein strands fall into one of three geometrically different categories random coil, a-helix and pleated sheet. 

Effect of thermostabilizers on the polymer properties was studied by different physicochemical methods. For example, in the work [260] method of DSS (differential spectroscopy) was used to define the effect of polyester-imide on thermo-physical properties of PETP. By this method it was found out that polyester-imide reduces PETP ability to crystallization. Methods of thermogravimetric analysis (TGA) and infrared spectroscopy in the nitrogen atmosphere were used in the work [261] to define thermal stability of the mixture of PETP and polyamide with the additive - modifier - polyethylene. It has been found that introduction of the additive decreases activation energy which positively tells on the ability of PETP to thermal destruction. 

Polymer Specimens. The materials used in this work were polyimide (PI),polyamide-imide (PAl), polyether-ether-ketone (PEEK), polyphenylene sulfide (PPS) and polyether sulphone (PES). The chemical formulas and physical properties of the specimen polymers are summarized in Table I. The specimen polymers, except PPS, were unfilled while the PPS specimen was filled with glass fiber of Uo wt. %. PAI and PES are amorphous polymer with considerably high glass temperature. The polymers, except PI, can flow at hi temperatures and allow the use of injection molding. 

These properties will differ in chemically different resins but even chemically similar resins by different supplier can show different performance characteristics. However, in many cases the lowering of the physical properties can be tolerated depending on the end use of the injection molded part. It should be noted based on customer reports that the physical properties of fiber reinforced polyamide parts are not effected by such high aluminum pigment loading. 

Very interesting and instructive results have been obtained by Fuller, Baker and Pape in systematic investigations on the X-ray behaviour and the physical properties of copolymers (i. e. polymers formed by polycondensation of mixtures of various repeating units) and methylated polyamides. Amongst other results, transformations of the X-ray pattern have been obtained upon stretching, which are similar to those observed in the a keratine- / keratine transformation in animal hairs (see below) h For this subject we must, however, refer to the literature cited. 

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