Nylon impact strength

Nylon Cloth Grade with Phenolic Resin Binder. Grade N-1 has excellent electrical properties under high humidity conditions and good impact strength, but is subject to flow or creep under load, especially at temperatures higher than normal. 

The effect of temperature on properties can be seen in Figure 2, which shows the effect on modulus of increasing temperature of unmodified and glass-reinforced nylon-6,6. Impact strength, however, shows a steady increase with temperature as it does with moisture. 

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. 

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. 

Copolymers of chlorotrifluoroethylene and ethylene were introduced by Allied Chemicals under the trade name Halar in the early 1970s. This is essentially a 1 1 alternating copolymer compounded with stabilising additives. The polymer has mechanical properties more like those of nylon than of typical fluoroplastic, with low creep and very good impact strength. Furthermore the polymers have very good chemical resistance and electrical insulation properties and are resistant to burning. They may be injection moulded or formed into fibres. 

The suppliers of nylon 46 have laid particular emphasis on the fact that this polymer, with its highly symmetrical chain structure, leads to both a high level of crystallinity and a high rate of nucleation. In turn the high nucleation rate leads to a fine crystalline structure which in this case is claimed to lead to a higher impact strength (dry as moulded) than with nylons 6 and 66. 

Figure 18.12. Effect of temperature on the impact strength of nylon 66. (Reproduced by permission...

Figure 18.11 shows the influence of temperature on the tension modulus of nylons 66 and 6 and Figure 18.12 the effect of temperature on impact strength of nylon 66. Figure 18.13 shows the profound plasticising influence of moisture on the modulus of nylons 6 and 66, while Figure 18.14 illustrates the influence of moisture content on impact strength. 

The glass-fibre nylons have a resistance to creep at least three times as great as unfilled polymers. In the case of impact strength the situation is complex since unfilled nylons tend to break showing tough fracture whereas the filled polymers break with a brittle fracture. On the other hand the glass-filled polymers are less notch sensitive and in some tests and service conditions the glass-filled nylons may prove the more satisfactory. 

Whilst nylon 66 has the higher T , the long-term heat resistance of typical copper-stabilised nylon 6 is somewhat superior in such properties as impact strength and bending strength compared to nylon 66. However, it is frequently the case that nylon 66 has better resistance to chemicals at elevated temperatures. 

It has been shown that for acrylic, glass-filled nylon and methyl pentene there is reasonable correlation between the reciprocal of the stress concentration factor, K, and impact strength. However, for PVC good correlation could only be achieved if the finite dimensions of the sample were taken into account in the calculation of stress concentration factor. 

In a partially crystalline homopolymer, nylon 6, property enhancement has been achieved by blending with a poly(ethylene-co-acrylic acid) or its salt form ionomer [24]. Both additives proved to be effective impact modifiers for nylon 6. For the blends of the acid copolymer with nylon 6, maximum impact performance was obtained by addition of about 10 wt% of the modifier and the impact strength was further enhanced by increasing the acrylic acid content from 3.5 to 6%. However, blends prepared using the salt form ionomer (Sur-lyn 9950-Zn salt) instead of the acid, led to the highest impact strength, with the least reduction in tensile... 

Nylon 11 Nylon 11 is a hard abrasion-resistant, scuff-resistant coating. When correctly formulated and applied, it can be used for exterior application. It has good resistance to solvents and to a range of alkalis and salt solutions up to 80°C. If water quenched, the coating has excellent impact strength. However, Nylon 11 is crystalline and pull-back from sharp edges can be a problem. It is therefore essential that metal work is well radiused. 

Nylons are used both in engineering applications and in making fibers. A combination of high impact strength and abrasion resistance makes nylon an excellent metal substitute for bearings and gears. As fiber, nylon is used in a variety of applications, from clothing to tire cord to ropes. 

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]. 

We can manipulate the properties of nylon products by changing the conditions under which we crystallize them. The degree of crystallinity is increased by slow cooling, annealing, and by crystallization from highly oriented melts. As we increase the crystallinity level, stiffness and yield strength increase at the expense of impact strength. 

There is no true correlation between the two methods as we can see in Figure 3.5, which displays the notched versus un-notched impact strength of various grades of polycarbonates, acrylics, polyphenylene sulfide and nylon. 

In general, substitution of polar atoms and polar groups for nonpolar or less polar moieties results in an increase in the Tg and such mechanical properties as yield stress and modulus. Thus condensation polymers such as nylons, polycarbonate (PC), and polyesters are typically higher-melting and exhibit higher Tg s, tensile strength and associated properties, but typically lower impact strengths and associated properties which require some flexibility (Table 5.3). 

Although glass spheres are classified as nonreinforcing fillers, the addition of 40 g of these spheres to 60 g of nylon 66 increases the flexural modulus, the compressive strength, and the melt index of the polymer. The tensile strength, the impact strength, the creep resistance, and the elongation of these composites are less than those of the unfilled nylon 66. 

---