Nylon also impact strength

Plasticizers. Plastici2ers are used to increase the flexibiHty of nylon and improve impact strength. They are most commonly used in nylon-11 and nylon-12 for such appHcations as flexible fuel hoses for automobiles. Unextracted nylon-6 is also used with the caprolactam acting as the plastici2er. Other common plastici2ers are long-chain diols and sulfonamides. 

Nylon-6-clay nanocomposites were also prepared by melt intercalation process [49]. Mechanical and thermal testing revealed that the properties of Nylon-6-clay nanocomposites are superior to Nylon. The tensile strength, flexural strength, and notched Izod impact strength are similar for both melt intercalation and in sim polymerization methods. However, the heat distortion temperature is low (112°C) for melt intercalated Nylon-6-nanocomposite, compared to 152°C for nanocomposite prepared via in situ polymerization [33]. 

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. 

Table VI compares the key properties of these two types of thermotropic polymers category by category. The samples compared had the same melting ranges, but were very different in reduced viscosities and solubility characteristics. The data compared were those processed under the most favorable conditions. Interestingly enough, the as-spun fibers from the polyester-carbonate can be heat-treated more efficiently than those fibers (of same tenacity) spun from the polyester. Both of them gave fiber properties far superior to those of nylons and polyethylene terephthalate. These two classes of polymers also had comparative properties (such as tensile strength, tensile modulus, flex modulus, notched Izod impact strength) as plastics and their properties were far superior to most plastics without any reinforcement.

From the table It appears that the Izod Impact strength Improves as the Interfacial adhesion increases. This Is also concluded In a recent publication about nylon 6.6 compounded with polyethylene-g-maleic anhydride polymer (15). Addition of more rubber In system 3 (30 %) affords hardly any addltonal Improvement In toughness, but the flexural modulus, which In ABA block copolymers Is already lower than In a dispersed rubber system, Is more than halved. 

Commercial impact modified PPE/PA blends exhibit notched Izod impact strengths ranging from 175 to 500 J/m at room temperature. They also differ in their ductile brittle transition temperature and low temperature impact behavior. The type of nylon used (PA-6 or PA-66 or copolymer type), its end group concentrations and molecular weight, and more importantly, the nature of the rubber modifier used (compatible... 

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],... 

The 1950s also saw the development of two families of plastics — acetal and polycarbonates. Together with nylon, phenoxy, polyimide, poly(phenylene oxide), and polysulfone they belong to the group of plastics known as the engineering thermoplastics. They have outstanding impact strength and thermal and dimensional stability — properties that place them in direct competition with more conventional materials like metals. 

The first commercial product made from nylon RIM was a front quarter panel (fender) for the Oldsmobile Omega Sport. Because of the excellent impact strength of nylon RIM, it has been used for bumper covers and automobile fascia. It also finds application in housings for business machines and electronics. 

Other environmental factors besides temperature may also affect impact behavior. For example, if the material is in the vicinity of a fluid which attacks it, then the crack-initiation energies may be reduced, resulting in lower impact strength. Some materials, particularly nylon, are significantly affected by water, as illustrated in Figure 3.40. The absorption of water produces a spectacular improvement in the impact behavior of nylon. 

I The effect of humidity also can be significant with certain plastics when the Innahanical strength, and in particular the impact strength, depends on the Ipioant of water absorbed (i.e., a typical example is nylon). 

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