An Immersion Test for Rubber Compounds

1941 ◽  
Vol 14 (3) ◽  
pp. 741-748
Author(s):  
B. S. Garvey
Keyword(s):  
Immersion Test ◽  
Preliminary Evaluation ◽  
Final Test ◽  
Swelling Agent ◽  
Rubber Compounds ◽  
Comparable Accuracy ◽  
Finished Article

Abstract The immersion procedure described here is much faster than the present A. S. T. M. method, and gives results of comparable accuracy. It requires less space and less solvent. The most serious objection to it is the occurrence of anisotropic swelling due to grain in the rubber. However, there is usually more grain in manufactured articles, such as hose, than in tensile sheets. Both methods are useful chiefly for the preliminary evaluation of compounds. The final test frequently is made on the finished article under special conditions. The sensitivity of this test to grain effects suggests that its use with a good swelling agent will be a useful tool for measuring the extent of such grain in various compounds.

Tear Initiation and Tear Propagation

1950 ◽  
Vol 23 (1) ◽  
pp. 137-150 ◽  
Author(s):  
J. M. Buist
Keyword(s):  
Test Piece ◽  
Maximum Shear Stress ◽  
Test Group ◽  
Preliminary Evaluation ◽  
Discriminating Power ◽  
Rubber Compounds ◽  
Group 2 ◽  
Tear Propagation ◽  
Limiting Value ◽  
Group 1

Abstract (1) Both the crescent and angle tests are group (2) tests; therefore the width of the sample must fee taken into account when the tear resistance is being calculated. (2) There is one exception to the above, and that is the case of knotty tears in group (2) tests. When knotty tears occur, the test becomes a direct tear test [group (1)], and the width is no longer important. (3) When knotty tears occur with group (1) tests, the width must be considered for, in reality, the test has become a group (2) test. (4) Some rubbers exhibit fibering during tearing, and this is explained by the cohesive forces between fibers reaching a limiting value before the limiting value of the breaking strength of a fiber is reached. (5) Differences in the mechanism of tearing with different fillers have been noted. (6) Practical evidence of the existence of maximum shear stress in subsurface planes of the material has been obtained, and a mathematical solution for a simple case has been given. (7) The angle tear method is a combination of tear initiation and tear propagation, and can be regarded as complementary to the crescent test. It cannot be regarded as a replacement for the crescent test. (8) With certain rubber compounds the component of stress in the direction of pull is too high in the case of the angle test-piece. (9) It is suggested that the unnicked crescent be used in preference to the angle test-piece for tear initiation measurements, as the unnicked crescent test-piece has more discriminating power. (10) The same proportion of straight and knotty tears occurs with both the crescent and angle methods. (11) A preliminary evaluation of the I.G. tear cutter indicates that the fairest comparison with other methods requires a single slit to be inserted in the outside circumference of the ring.

Determination of Effective Crosslink Density in Silicone Rubber

1965 ◽  
Vol 38 (4) ◽  
pp. 924-939
Author(s):  
Robert D. Seeley ◽  
George W. Dyckes
Keyword(s):  
Silicone Rubber ◽  
Crosslink Density ◽  
Theoretical Calculations ◽  
Empirical Relationships ◽  
Physical Test ◽  
Swelling Agent ◽  
Rubber Compounds ◽  
Resultant Data ◽  
Volume Swelling

Abstract As a result of the investigations reported here, a simple and precise method was evised to measure the compression-deflection of solvent-swollen silicone rubber. The method was found to be reliable, and the resultant data were used to calculate effective crosslink densities of solid and cellular silicone rubber compounds. Empirical equations were derived relating compression and deflection to effective crosslinking of solid and cellular silicone rubber swollen in toluene. The weak swelling action of MEK precludes the derivation of empirical relationships between compression, deflection, and effective cross-linking of the rubber. The investigation further showed that toluene is a better and more useful swelling agent than methyl ethyl ketone (MEK). The volume swelling ratios for toluene and MEK were determined. Toluene was found to be about 1.4 times more effective as a swelling agent than MEK. Limited laboratory physical test data show a reasonable correlation to νe/Vr data. (More testing will be required to establish definite relationships.) This investigation also showed that the method employed here for crosslinking determinations is suitable for cellular rubber, since the data obtained from toluene-swollen specimens agrees quite well with theoretical calculations. Finally, the Flory-Huggins interaction parameters for toluene and MEK were determined.

Dye Penetrant Induced Micro cracking in High Performance Thermoplastic Polyimide Composites

1998 ◽  
Vol 32 (1) ◽  
pp. 31-48 ◽  
Author(s):  
A. Paige Clifton Furrow ◽  
David A. Dillard ◽  
Terry L. St. Clair ◽  
Jeffrey Hinkley
Keyword(s):  
Composite Materials ◽  
High Performance ◽  
Immersion Test ◽  
Material System ◽  
Final Test ◽  
Stress Cracking ◽  
Thermal Residual Stresses ◽  
Polyimide Composites ◽  
Dye Penetrant ◽  
The Individual

The possibility of spurious microcracking in three high performance thermoplastic polyimide composite materials due to zinc iodine dye penetrant was studied. The material systems were IM7/LaRCTM-IAX, IM7/LaRCTM-IAX2, and IM7/LaRCTM-8515. Specimens from each material system were subjected to one of three immersion tests. The first immersion test involved soaking composite specimens previously prepared with different polishing techniques in dye penetrant. In the second test, specimens were soaked in the individual components of the dye penetrant. The final test involved soaking the specimens in one of six immersion liquids followed by soaking in dye penetrant. Results showed that the composite materials have sufficiently high thermal residual stresses to drive microcracking in the presence of dye penetrant without external mechanical loading. There was no evidence that the different polishing techniques had an effect on dye penetrant induced stress cracking. The individual components of the dye penetrant did not produce microcracks in the composites. Some combination of the components must be present to induce microcracking. Observations also revealed that polishing had an effect on the microcracking process of the composites that were initially soaked in immersion liquids then dye penetrant.

Preliminary Evaluation of a Weibull Function for Fitting Slow-Component Eye Velocity over the Time Course of Caloric-Induced Nystagmus

1989 ◽  
Vol 32 (3) ◽  
pp. 681-687 ◽  
Author(s):  
C. Formby ◽  
B. Albritton ◽  
I. M. Rivera
Keyword(s):  
Time Course ◽  
Slow Component ◽  
Weibull Function ◽  
Preliminary Evaluation ◽  
Mathematical Function ◽  
Before And After ◽  
Best Fitting ◽  
Eye Velocity ◽  
Fitting Parameters ◽  
Weibull Equation

We describe preliminary attempts to fit a mathematical function to the slow-component eye velocity (SCV) over the time course of caloric-induced nystagmus. Initially, we consider a Weibull equation with three parameters. These parameters are estimated by a least-squares procedure to fit digitized SCV data. We present examples of SCV data and fitted curves to show how adjustments in the parameters of the model affect the fitted curve. The best fitting parameters are presented for curves fit to 120 warm caloric responses. The fitting parameters and the efficacy of the fitted curves are compared before and after the SCV data were smoothed to reduce response variability. We also consider a more flexible four-parameter Weibull equation that, for 98% of the smoothed caloric responses, yields fits that describe the data more precisely than a line through the mean. Finally, we consider advantages and problems in fitting the Weibull function to caloric data.

Suppressed, but Not Forgotten

2011 ◽  
Vol 70 (1) ◽  
pp. 5-11 ◽  
Author(s):  
Beat Meier ◽  
Anja König ◽  
Samuel Parak ◽  
Katharina Henke
Keyword(s):  
Memory Trace ◽  
Thought Suppression ◽  
Test Phase ◽  
Indirect Test ◽  
Final Test ◽  
Test Experiment ◽  
And Control ◽  
Cue Words ◽  
The Impact

This study investigates the impact of thought suppression over a 1-week interval. In two experiments with 80 university students each, we used the think/no-think paradigm in which participants initially learn a list of word pairs (cue-target associations). Then they were presented with some of the cue words again and should either respond with the target word or avoid thinking about it. In the final test phase, their memory for the initially learned cue-target pairs was tested. In Experiment 1, type of memory test was manipulated (i.e., direct vs. indirect). In Experiment 2, type of no-think instructions was manipulated (i.e., suppress vs. substitute). Overall, our results showed poorer memory for no-think and control items compared to think items across all experiments and conditions. Critically, however, more no-think than control items were remembered after the 1-week interval in the direct, but not in the indirect test (Experiment 1) and with thought suppression, but not thought substitution instructions (Experiment 2). We suggest that during thought suppression a brief reactivation of the learned association may lead to reconsolidation of the memory trace and hence to better retrieval of suppressed than control items in the long term.

Sign in / Sign up

Export Citation Format

Share Document