Aliphatic polymers polyamides

Wu and Siesler have assigned additional secondary amide bands in their study of the aliphatic polymer polyamide 11 (PAll). Using deuteration, variable temperature, and polarization measurements, the assignments listed in Table 8.6 were made. 

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. 

Crystalline polymers exhibit the following basic properties They are opaque as long as the size of the crystallites or spherulites, respectively, lies above the wavelength of light. Their solubility is restricted to few organic solvents at elevated temperature. The following crystalline polymers have attained technical importance as thermoplastic materials polyethylene, polypropylene, aliphatic polyamides, aliphatic/aromatic polyamides, aliphatic/aromatic polyesters, poly-oxymethylene, polytetrafluoroethylene, poly(phenylene sulfide), poly(arylene ether ketone)s. 

In the future, prospects for combining engineering polymers with the lower cost commodity polymers should lead to unique cost/performance systems. Potential combinations might include PC/PP, polyester (PBT, PET)/PP and POM/PP or HOPE. Newer commercial polyamides (PA-46 Amodel (Amoco) aliphatic/aromatic polyamide) should also be off interest in new blend combinations. An example of this involves Amodel/ PPS blends as noted by Chen and Sinclair [1997]. Although the rate of introduction of new engineering polymers has decreased, new additions will be continued to be expected and thus new blend combinations will also be offered. 

Y. Zhang, J. C. Tebby, and J. W. Wheeler. Polyamides incorporating phosphine oxide groups IV. Aromatic-aliphatic polymers. Eur. Polym. J., 35(2) 209-214, February 1999. 

Polyamides Thermoplastic aromatic or aliphatic polymer of dicarboxylic acids and diamines, of amino acids, or of lactams. Has good mechanical properties, chemical resistance, and antifriction properties. Processed by extrusion and molding. Used in fibers and molded parts. Also called PA. 

The two main commercial polyamides are nylon 6,6, produced by condensation polymerization of HMD and adipic acid (see Table 7.1), and nylon 6, an AB-type polymer, which is produced from caprolactam. Other commercial polyamides include nylons 4,6, nylon 6,12 (which are AA- and BB-type polymers) and nylon 11 and nylon 12 (which are AB polymers made from linear aliphatic amino acids containing 11 and 12 carbons, respectively) [1]. Polyamides are also produced using monomers with aromatic, rather than aliphatic segments. Polyamides that contain 85% or more of the amide bonds attached to aromatic rings are called aramids. Commercial examples include poly(p-phenyleneterephthalamide) or Kevlar and poly(m-phenyleneisoterephthalamide) or Nomex [23]. 

The homopol5unerization of diisocyanates is only useful for specialty diisocyanates, such as aliphatic 1,2- or 1,3-diisocyanates (3) and aromatic o-diisocyanates (4), which polymerize via cycloaddition processes. Anionic homopolymerization of monoisocyanates takes place by addition across the 0=N bond to form nylon-1 polymers. Polyamides are also obtained fi"om diisocyanates and enamines or ketenaminals. This reaction proceeds by a [2 -i- 2] cycloaddition reaction with subsequent ring opening to form polyamides. [2 - - 4] cycloaddition polymerization to form heterocyclic polymers is observed with carbonyl diisocyanate (5). Ring-opening polymerization occurs in the reaction of bis-epoxides... 

The excimer laser irradiation of synthetic fibers made of highly absorbing polymers, e.g. aromatic polymers such as PET and aramids as well as aliphatic polymers such as polyamide-6 and -6.6 (PA), generates a... 

The comparison of the results obtained in this study for the LCP degradation imder processing temperatures with the peculiarities of some thermally stable polyheteroaiylenes degradation [14] brings to light some common features carbonization of the structure, H2 evolution, improvement in thermo-oxidative stability with transition metal compoimds. That is why we took into accoimt the stabilization of polysulfones, aiyl-aliphatic polyimides, polyamides etc. The approach to such stabilization is based on the following proposals on the mechanisms of the above said polymer degradation ... 

Kuphal, J.A., Sperling, L.H., and Robeson, LM. (1991) Miscible blends of styrene-acrylic add copolymers with aliphatic, crystalline polyamides. /. Appl. Polym. Sci., 42, 1525-1535. 

Crystalhne polymers may be nucleating agents for other crystalline polymers. This holds true of course for polymers that are chemically very similar, for example, high and low density PEs. However, many other examples of polymer/polymer epitaxy are available, even for mildly or incompatible polymer pairs PE versus aliphatic polyesters, polyamides versus iPP, PE versus iPP and, reciprocally, iPP versus PE, PTFE versus iPP, and so on. 

Most polyesters, polyamides, and polyurethanes are susceptible to hydrolysis with a consequent decrease in molecular weight. Aliphatic polymers often hydrolyze more rapidly than aromatic polymers. Once again, the lower molecular-weight materials are subject to biological attack. The hydrolysis itself may be part of enzymatic attack on the main chains. Some polyurethanes based on polyester polyols are easily... 

Polyamide or polyimide polymers are resistant to aliphatic, aromatic, and chlorinated or fluorinated hydrocarbons as well as to many acidic and basic systems but are degraded by high-temperature caustic exposures. 

Tension Above materials plus High-density polyethylene Polypropylene Acetal polymers Aliphatic polyamides (nylons) PPO Poly(ethylene terephthalate) Polysulphones... 

As is commonly the case with crystalline polymers the glass transition temperature is of only secondary significance with the aliphatic polyamide homopolymers. There is even considerable uncertainty as to the numerical values. Rigorously dried polymers appear to have TgS of about 50°C, these figures dropping towards 0°C as water is absorbed. At room temperature nylon 66 containing the usual amounts of absorbed water appears to be slightly above the T ... 

Whilst the aliphatic nylons are generally classified as being impact resistant, they are affected by stress concentrators like sharp comers which may lead to brittle failures. Incorporation of mbbers which are not soluble in the nylons and hence form dispersions of rubber droplets in the polyamide matrix but which nevertheless can have some interaction between mbber and polyamide can be most effective. Materials described in the literature include the ethylene-propylene rubbers, ionomers (q.v.), polyurethanes, acrylates and methacrylates, ABS polymers and polyamides from dimer acid. 

As with the aliphatic polyamides, the heat deflection temperature (under 1.82 MPa load) of about 96°C is similar to the figure for the Tg. As a result there is little demand for unfilled polymer, and commercial polymers are normally filled. The inclusion of 30-50% glass fibre brings the heat deflection temperature under load into the range 217-231°C, which is very close to the crystalline melting point. This is in accord with the common observation that with many crystalline polymers the deflection temperature (1.82 MPa load) of unfilled material is close to the Tg and that of glass-filled material is close to the T. ... 

Carothers also produced a number of aliphatic linear polyesters but these did not fulfil his requirements for a fibre-forming polymer which were eventually met by the polyamide, nylon 66. As a consequence the polyesters were discarded by Carothers. However, in 1941 Whinfield and Dickson working at the Calico Printers Association in England announced the discovery of a fibre from poly(ethylene terephthalate). Prompted by the success of such a polymer, Farbenfabriken Bayer initiated a programme in search of other useful polymers containing aromatic rings in the main chain. Carbonic acid derivatives were reacted with many dihydroxy compounds and one of these, bis-phenol A, produced a polymer of immediate promise. 

This class of polyesters consists of four major commercial polymers and their copolymers, namely PET, PTT, PBT, and PEN (see Table 2.1). They compete for engineering thermoplastics, films, and fibers markets with other semicrystalline polymers, such as aliphatic polyamides, and for some other applications with amorphous engineering plastics such as polycarbonate. The syntheses of PET and PBT, detailed in numerous reviews and books,2-5 are described in Sections 23.2.2 and 2.3.2.1. 

Polymers with hetero-atoms in the chain are suitable for chemical recycling of waste materials. In addition to depolymerisation (nylon 6) and solvolysis (nylon 6,6, PETP, PU) the degradation of aliphatic polyamides with dicarboxylic acids, diamines and cyclic anhydrides, especially trimellitic anhydride, becomes more and more important. The utilisation of the obtained fragments is described. 

The most prominent aliphatic polyamides are polyamide 6 and polyamide 6.6. Polyamides are used in a broad range of applications as performance polymers in medicine, textile, and car manufacturing industries. In 2003, the European production ofpolyamides was approximately 3 million tons for technical applications. Of the total polyamide consumption, 94% was polyamide 6 and polyamide 6.6. 

---