Nylon viscoelasticity

One component of a terpolymer of butadiene, styrene and vinyl pyridine used in latex form to promote good adhesion between rubber and textiles, particularly rayon and nylon. Viscoelasticity... 

The early invesligations of viscoelasticity using silk, glass, and rubber may be extended to fibers, plastics, and elastomers, respectively. One of the early observations was that these materials undergo very slow irreversible flow or creep when subjected to stress over a long period of time. This irreversible effect is responsible for the so-called flat spots in nylon 66-rein-forced pneumatic tires. 

Researchers have examined the creep and creep recovery of textile fibers extensively (13-21). For example, Hunt and Darlington (16, 17) studied the effects of temperature, humidity, and previous thermal history on the creep properties of Nylon 6,6. They were able to explain the shift in creep curves with changes in temperature and humidity. Lead-erman (19) studied the time dependence of creep at different temperatures and humidities. Shifts in creep curves due to changes in temperature and humidity were explained with simple equations and convenient shift factors. Morton and Hearle (21) also examined the dependence of fiber creep on temperature and humidity. Meredith (20) studied many mechanical properties, including creep of several generic fiber types. Phenomenological theory of linear viscoelasticity of semicrystalline polymers has been tested with creep measurements performed on textile fibers (18). From these works one can readily appreciate that creep behavior is affected by many factors on both practical and theoretical levels. 

There are three major viscoelastic relaxations in 66 nylon... 

Basic Approach. We consider the cases in which a viscoelastic specimen such as a piece of nylon monofilament is subjected to a sinusoidal straining expressed by ... 

Characteristics of the Hysteresis Loop and Stress Wave in the Nonlinear Viscoelastic Response to the Sinusoidal Straining. Figure 3 is a schematic of a hysteresis loop obtained when a nylon 6 monofilament was subjected to a sinusoidal straining with yo = 1% and Ay = 1% at 90°C under a frequency of 10 cycles per sec. 

Rheological studies of PET nanocomposites are not ample, but show very interesting features. In the low frequency range, the nanocomposites display a more elastic behavior than that of PET. It appears that there are some physical network structures formed due to filler interactions, collapsed by shear force, and after all the interactions have collapsed, the melt state becomes isotropic and homogeneous. Linear viscoelastic properties of polycaprolactone and Nylon-6 [51] with MMT display a pseudo-solidlike behavior in the low frequency range of... 

A nylon bolt of diameter 8 mm is used to join two rigid plates. The nylon can be assumed to be linearly viscoelastic with a tensile-stress-... 

Polypropylene melts are viscoelastic fluids. As such, the melts exhibit non-Newtonian viscosity, normal stresses in shear flow, excessive entrance-and-exit pressure drop, die swell, secondary entrance flows, melt fracture, and draw resonance. (Newtonian fluids also exhibit draw resonance.) Polypropylene melts are more viscoelastic than melts of nylon and polyester. 

Figure 7 Temperature dependence of the viscoelastic propcitics( tan ) of nylon 6 films (Ihnsile mode, iOHz).

The discussions above focus on the small strain as a response of polymer materials to the small stress. Large stress brings large strain and even destroys the inherent structure of the solid materials, causing permanent deformation. Under the constant strain rates, the stress-strain curve reflects the structural and viscoelastic characteristic features of materials. For polymer materials, there occur five typical curves, as illustrated in Fig. 6.18 (1) hard and brittle, such as PS and PMMA, eventually brittle failure (2) hard and tough, such as Nylon and PC, most of semi-crystalline polymers. 

In the course of extensive studies of the creep and recovery behaviour of textile fibres already referred to, Leaderman [13] became one of the first to appreciate that the simple assumptions of linear viscoelasticity might not hold even at small strains. For nylon and cellulosic fibres he discovered that although the creep and recovery curves may be coincident at a given level of stress - a phenomenon associated with linear viscoelasticity (Section 4.2.1) the creep compliance plots indicated a softening of the material as stress increased, except at the shortest times (Figure 10.4). Thus, the creep compliance function is non-linear and of the... 

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