Polyamide aliphatic

Aliphatic polyamides do not absorb light above 290 nm and photo-oxidative degradation of these polymers in that region can be initiated by the presence of such impurities as hydroperoxides, [47, 139] carbonyl groups [1869], a,j -unsaturated carbonyl groups [47, 65, 89, 99, 103] and traces of metal ions [236]. 

Carbonyl groups, which form in nylons either by photo-oxidation and thermal oxidation or by the interaction of carboxyl end-groups during processing, appear to exist as keto and iV-acylamide (or imide) groups. 

Nylons 6 and 6,6 exhibit a weak absorption at about 290 nm, which is associated with the n, n transition of a,jS-unsaturated carbonyl groups, because the n electron donation from the nitrogen is more efficient than its withdrawal. 

The major initial step in the photo-oxidation of aliphatic polyamides at 

Polyamide 11 (polyundecanamide) Polyamide 12 (polydodecanamide) Poly(amide-co-carbon monoxide) Poly( -caproamide) 

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The United States accounts for about a third of the world s consumption of cyclohexane, or 3.785 x 10 m /yr (about 1 biUion gallons per year). U.S. producers and their 1990 capacities are Hsted in Table 13. Texaco has aimounced that it is leaving the cyclohexane business, but the timing is not yet certain. Over 90% of all cyclohexane goes to the production of nylon through either adipic acid (qv) or caprolactam (qv). The balance is used to produce 1,6-hexamethylenediamine [124-09-4] (HMD A) and for various solvent uses (see Diamines and higher amines, aliphatic Polyamides). 

Table 9. Physical Constants of Commercial Aliphatic Polyamide Homopolymers ...

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

There are a number of structural variables which can considerably affect the properties of the aliphatic polyamides ... 

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 ... 

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. ... 

As with the aliphatic polyamides such as nylons 6 and 66, the polyphthalamides were developed as plastics materials only after their sucessful use in the field of fibres. Such materials were introduced in 1991 by Amoco under the trade name of Amodel. 

The use of PBT as an engineering material is more a consequence of a balance of good properties rather than of a few outstanding ones. It does not possess the toughness of polycarbonate, the abrasion resistance of an aliphatic polyamide, the heat resistance of a polysulphone, polyketone or poly(phenylene sulphide) or... 

Tuzar, Z., Kratochvil, P., and Bohdanecky, M. Dilute Solution Properties of Aliphatic Polyamides. Vol, 30, pp. 117-159. 

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. 

With DMA the effect of temperature on the modulus can be studied. By increasing the temperature from -150 to 300°C, one encounters several transitions in PA (Fig. 3.1). There is a transition at about —120°C, the y-transition, which is due to the mobilization of methylene units. There is also a transition at —30°C, which is present in wetted aliphatic PA this is due to non-H-bonded amide units and is termed the /J-transition. At about 50°C the glass Uansition (Tg) (a-transition) of the aliphatic polyamides PA-6 and PA-6,6 occurs. At this Uansition, the modulus is lowered considerably. For partially aromatic PA, the Tg occurs above 100°C. The last transition is the flow temperature, at which temperature the material melts the flow temperature and the melt temperature, as measured by DSC, correspond well. The modulus is a measure of dimensional stability and increases with crystallinity and filler content (Fig. 3.12). 

Aliphatic hyperbranched polyesters, 56 Aliphatic isocyanate adducts, 202 Aliphatic isocyanates, 210, 225 Aliphatic polyamides, 138 Aliphatic polyesteramides, 56 Aliphatic polyesters, 18, 20, 29, 32, 87 degradable, 85 hyperbranched, 114-116 melting points of, 33, 36 structure and properties of, 40-44 syntheses of, 95-101 thermal degradation of, 38 unsubstituted and methyl-substituted, 36-38... 

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. 

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