Toughened nylons

Nylon 6/6 is the most widely used, followed by nylon 6, with similar properties except that it absorbs moisture more rapidly and its melting point is 21C (70F) lower. Also, its lower processing temperature and less crystalline structure result in lower mold shrinkage. Nylon 6/6 has the lowest permeability by gasoline and mineral oil of all the nylons. The 6/10 and 6/12 types are used where lower moisture absorption and better dimensional stability are needed. Nylons 11 and 12 have better dimensional stability and electrical properties than the others because they absorb less moisture. These more expensive types also are compounded with plasticizers to increase their flexibility and ductility. With nylon toughening and technology advancements supertough nylons became available. Their notched lzod impact values are over 10 J/m (20 ft-lb/in), and they fail in a ductile manner. 

It is also possible to manipulate the structure by introducing other monomers into the polymer chain, changing the mechanical properties of the final material by copolymerization. It is also common, for economic reasons or to increase mechanical properties, to add particulate solids to the polymer, such as wood flour or other additives, that will affect the final mechanical properties. Another common approach is the preparation of blends of two different polymers, which are commonly nonsoluble in each other, as a strategy to increase some mechanical properties such as impact strength, as in the well-studied case of nylon toughening by butyl rubber [8, 9],... 

With nylon, toughening and technology advancements super tough nylons became available. Their notched Izod impact values are over 10 J/m (20 ft-lb/in), and they foil in a ductile manner. 

The results for the 120 C-curing epoxy film adhesives are shown in Fig. 9. Marked differences are noted here. The AF-44 nylon-toughened epoxy has very poor durability at any load and adhesion failure predominates. AF-126-2, the first-generation nitr ile-r ubber-f lexibilized epojiy has somewhat better durability and the failure mode is at least partially cohesive. AF-163 and AF-163-2, the second-generation-toughened epoxies, show a substantial... 

The nylon-toughened adhesive, AF-44, presents a special problem. The nylon-toughening material which gives this adhesive its exceptional properties is hydrophilic and its "toughening" is likely due to the presence of intermolecular hydrogen bonds. In the presence of... 

By plasticisation. This in effect reduces the Tg and in the case of nylon which has absorbed small quantities of water the toughening effect can be quite substantial. It should, however, be noted that in the case of PVC small amounts of plasticiser actually reduce the impact strength. 

Glass-fibre-filled grades of these toughened polymers are also available but these do not show the same improvement in toughness over normal glass-fibre-filled nylons. 

Polycarbonate-polystyrene blend along with poly(alkylene-dicarboxylate) such as SMA SEBS copolymer for toughening blends of PPO with nylon and polyolefin (proprietary compatibilizer)... 

Dijkstra K (1993) Deformation behavior of toughened Nylon 6, PhD dissertation. University of Twente... 

Many engineering thermoplastics such as nylon, high-impact PS, polyesters, and toughened plastics exhibit responses similar to those shown in the next two curves in Figure 3.3, designated ductile. Here the stress achieves a maximum called a yield stress at a specific strain. As strain increases beyond... 

Impact Modifiers. Notched impact strength and ductility can be improved with the incorporation of impact modifiers, which also can lower the britde— ductile transition temperature and give much improved low temperature toughness. Impact modifiers are rubbers (often olefin copolymers) that are either modified or contain functional groups to make them more compatible with the nylon matrix. Dispersion of the mbber into small (micrometer size) particles is important in order to obtain effective toughening (29). Impact modifiers can be combined with other additives, such as glass fiber and minerals, in order to obtain a particular balance of stiffness and toughness. 

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