Elongation measurement

Some viscoelasticity results have been reported for bimodal PDMS [120], using a Rheovibron (an instrument for measuring the dynamic tensile moduli of polymers). Also, measurements have been made on permanent set for PDMS networks in compressive cyclic deformations [121]. There appeared to be less permanent set or "creep" in the case of the bimodal elastomers. This is consistent in a general way with some early results for polyurethane elastomers [122], Specifically, cyclic elongation measurements on unimodal and bimodal networks indicated that the bimodal ones survived many more cycles before the occurrence of fatigue failure. The number of cycles to failure was found to be approximately an order of magnitude higher for the bimodal networks, at the same modulus at 10% deformation [5] ... 

In standard FAB, the surface of the matrix solution is depleted of analyte and suffers from radiational damage during elongated measurements. Refreshment of the surface proceeds by diffusion (limited by the viscosity of the matrix) or evaporation. Continuous-flow fast atom bombardment (CF-FAB) continuously refreshes the surface exposed to the atom beam. [107,108] The same effect is obtained in slightly different way by the frit-fast atom bombardment (frit-FAB) technique. [109,110] In addition, both CF-FAB and frit-FAB can be used for online-coupling of liquid chromatography (LC, Chap. 12) [111] or capillary electrophoresis (CE) to a FAB ion source. [112]... 

The raw data from a tensile test are the load versus elongation measurements made by the load cell and the extensometer, respectively. To eliminate sample geometry effects, the extension is divided by the initial length to obtain the dimensionless strain (which is occasionally multiplied by 100 and reported as % elongation for samples... 

Elastomer behavior is depicted by the bottom curve in Figure 3.3. Here the modulus (ratio of stress to strain, as of strength to elongation measure of polymer stiffness) is low, but elongations to several hundred percent are possible before failure. 

The elongation measured over a fixed gage length, and the reduction of area of the section at the fracture are measures of ductility. In cylindrical specimens, the area is readily determined from the final diameter at the fracture. The percent reduction of area is then determined as original area minus final area, divided by original area. 

As can be seen from Table 6, the physical properties of some of the cured blends made with the surface devulcanized reclaimed rubber crumb samples were equivalent to those made with only virgin rubber. For instance, the 100% modulus, 300% modulus, and percent elongation measured in Examples 19 and 20 were very similar to those found in the control using only virgin rubber (the series labeled None ). 

Low-Density Polyethylene. The data from outdoor weathering are summarized In Figure 1. The low-temperature brittleness (LTB) measurements show that a well-dispersed carbon black of > 1% concentration and < 35 millimicrons (mu) particle size Is necessary for maximum resistance to photo-oxldatlon. The results from elongation measurements agree with those found for LTB, as would be expected, since both measurements reflect the notch sensitivity of polyethylene to micro cracks caused by photo-oxldatlon. Accelerated weathering studies on these compounds have been reported previously (2) and Indicate the same ranking as found in outdoor exposure. 

Stress-decay is Illustrated In Figure 2. Here the fiber was stretched 300% and the change Is stress requlrd to maintain that elongation measured as a function of time. 

Tables 3.70 through 3.72 summarize the effect of one-year South Florida outdoor exposure on the electrical and mechanical properties of FEP. Little change has occurred in the dielectric breakdown strength, dielectric constant, and dissipation factor of FEP due to exposure. Tensile strength and break elongation measurements are essentially unchanged. The only decline is in the MIT flex life (ASTM D2176) of the one-year sample, which could be due to measurement error. The reason for a decrease in flex life could be the MIT method that has a high degree of uncertainty. Certainly, the other mechanical properties do not support the measured decline in the flex life.

Tensile strips of polyester were cut, three in each direction, i.e. machine direction (MD) and transverse direction (TD). The films were then immersed in < of reagent for seven days, after which tensile and elongation measurements were then carried out. 

The strength and elongation measurements are taken from autographic load-extension curves. Reduction of area is obtained from direct measurements of the test specimen. Because of the very small diameter of the wire and the importance of accurate measurements, a precise method of measuring the original and final diameters is employed. A microscope with cross hairs and a movable, calibrated stage is used to obtain diameter measurements accurate to 0.0001 in. 

Fiber elongation measurements are based on the rate of elongation, dL/dt, where L is the fiber length, of a fiber of cross-sectional area, A, which is suspended vertically in a furnace. The elongation rate is determined by the viscosity of the melt and the applied stress, F/A, where F is the force applied to the fiber. The viscosity is then given by the expression ... 

The maximum elongation measured for lanyards during the force test ... 

Table 6 Basic properties of metallocene copolymers and reference LDPE characterized with the melt elongational measurements...

---