Nylons melting temperatures

Nylon 6 and 6/6 possess the maximum stiffness, strength, and heat resistance of all the types of nylon. Type 6/6 has a higher melt temperature, whereas type 6 has a higher impact resistance and better processibility. At a sacrifice in stiffness and heat resistance, the higher analogs of nylon are useful primarily for improved chemical resistance in certain environments (acids, bases, and zinc chloride solutions) and for lower moisture absorption. 

Nylon-4,6 [24936-71-8] introduced as Stanyl by Dutch State Mines, is synthesized from 1,4-tetramethylenediarnine and adipic acid (202). Stanyl has a high melting temperature (295°C), improved chemical resistance, better dimensional stabiUty, and higher modulus than nylon-6 and nylon-6,6 it is therefore highly suited for industrial yam appHcations, including tire cord. 

The mixture of oligomers was heated in a flask to 200°C in a mineral bath (the DSC peak melting temperature of the oligomers was 230°C) while stirring and removing water formed with a vacuum pump to form high-molecular-weight nylon-6,6. 

Among the spectrum of melt-spinnable fibers such as polyolefins and nylons, PET stands at the upper end in terms of crystalline melt temperature and glass transition temperature. This provides superior dimensional stability for applications where moderately elevated temperatures are encountered, e.g. in automobile tires or in home laundering and drying of garments. The high thermal stability results from the aromatic rings that hinder the mobility of the polymer chain. 

Thermal stability. The presence of side chains, cross-linking, and benzene rings in the polymer s "backbone increase the melting temperatures. For example, a spectrum of polymers with increasing melting temperatures would be polyethylene, polypropylene, polystyrene, nylon, and polyimide. 

The star-branched and two-armed systems appear to have enhanced entanglements or crosslinked networks that allow them to maintain their forms at temperatures above the linear nylon 6 melt temperature. Both the star-branched and two-armed species have melt temperatures slightly below that of single-armed nylon 6. The di-armed nylon appears to have properties similar to both the singlearmed and the star species. 

Other perfluoroalkyl polymers have been produced with sufficient thermal stability to withstand the temperatures of nylon melts from which carpet fihers are spun. During the subsequent heat treatment of the fiher the perfluoroalkyl groups diffuse to the surface to form a soil-resistant coating. Although such coatings add to the initial cost of the carpet they eventually save money by increasing the time intervals between cleanings. 

The upper limit of the Newtonian plateau is dependent on Mw and the melt temperature. Commonly, it is roughly in the region y = 10 2s 1. Low viscosity fiber-forming Nylon and polyethylene terephthalate (PET) are important exceptions, as their Newtonian plateau extends to higher shear rates. 

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