52,333 research outputs found
tack n / tack [or tac':]
No full texttackcome in tack with 'touch, contact' But that summer I had the misfortune of coming in tack with a biologist who was sent out from St. John's to study the habits of the Atlantic salmon. Rattles and Steadies: Memoirs of a Garden River Man 123 Chl 6'touch, contact'PRINTED ITEM DNE SupWK G. M. StorySEP 2 3 1985Used I and SupUsed I and SupNot use
Molecular Aspects of Tack
No full textAbstract
In this paper, we examined strength development at a polymer-polymer interface in terms of the dynamics and statics of random-coil chains. Interdiffusion of chain segments across the interface was considered to be the controlling factor for tack and green strength of uncured linear elastomers. This concept is similar to that proposed by Voyutskii and differs markedly from contact theories as proposed by Anand. In our approach, time dependent wetting first occurs followed by interdiffusion. Increasing contact pressure and temperature should promote the establishment of molecular contact (wetting) at the interface up to a saturation point of complete wetting. However, interdiffusion is retarded by increased hydrostatic pressure and enhanced by temperature in the usual thermally activated manner. The effect of pressure on diffusion is to reduce the volume available for the “hopping” process of segmental motion and subsequently decrease the self-diffusion coefficient. This effect is important in polymer processing where large hydrostatic pressures are encountered but is not very important in normal tack experiments where the contact pressures are much less than a kilobar. Thus, tack measurements should be dependent on pressure to some degree at short contact times but should be largely independent of pressure at long contact times. Increasing the test temperature increases the average interdiffusion chain segment length, l, but decreases the stress required to pull the chain out. Since l increases with temperature as l(T)∼exp −Qd/2kT and the stress decreases faster with temperature as σ(T)∼exp Qd/4kT, the tack evaluated at constant time will decrease with increasing temperature for the interdiffusion controlled process. The effect of molecular weight on tack at constant contact time, tc, is to increase the tack according to σ∼M1/2 for those molecular weights whose relaxation time t∞&lt;tc and decrease the tack according to σ∼M1/4 for those molecular weights where t∞&lt;tc. The tack should reach a maximum at a molecular weight corresponding to t∞=tc. The latter value could be used to determine the self-diffusion coefficient of the chains. At small contact times, the results might be complicated by wetting processes. The position of this maximum in σ versus M is relatively insensitive to the contact time, sincet∞∼M3 and M at the maximum will consequently increase as tc1/3. These predictions appear to be in agreement with much experimental data on tack and green strength reviewed and presented by Hamed and Rhee, but differ in many respects from their own interpretations of the same data. In conclusion, the most important results of our molecular dynamics approach to tack and green strength are as follows; (i) the tack, a, depends on t and M, as σ∼t1/4M−1/4, for t⩽t∞; (ii) the green strength, σ∞, depends on M, as σ∞∼M1/2; (iii) both σ and σ∞ depend on testing rate, ε˙, as σ∼ε˙1/2 for T≫Tg; (iv) the self-diffusion coefficient, D, depends on M, as D=A/M2 and can be measured mechanically using appropriate tack and green strength data. These results are not unique to elastomers, and most of them have been shown to apply to other polymer materials by our laboratory and some of them have also been investigated by Kausch's group in Lausanne using crack healing experiments on glassy PMMA.</jats:p
Investigation of the behavior of asphalt tack coat interface layer.
No full textState Project 736-99-1028LTRC Project 00-2BAsphalt tack coat is a light application of asphalt, usually asphalt diluted with water. It ensures a bond between the surface being paved and the overlying course by providing increased shear strength between two interfaces. Normally hot asphalt cements, emulsified asphalts or cutback asphalts are used as tack coat. The objective of this study was to evaluate the practice of using tack coats through controlled laboratory simple shear tests and determine the optimum application rate. The influence of tack coat types, application rates, and test temperatures on the interface shear strength was examined. Six emulsions (CRS-2P, CRS-2L, SS-1, CSS-1, SS-1h and SS-1L) and two asphalt binders (PG 64-22 and PG 76-22M) were selected as tack coat materials. The residual application rates considered were 0.00 l/sq m (0.00 gal/sq yd), 0.09 l/sq m (0.02 gal/sq yd), 0.23 l/sq m (0.05 gal/sq yd), 0.45 l/sq m (0.1 gal/sq yd), and 0.9 l/sq m (0.2 gal/sq yd). A simple shear test was performed to determine the shear strength at the interface at two test temperatures, 25 deg C (77 deg F) and 55 deg C (131 deg F). The influence of vertical load levels on interface bonding strength was evaluated using the optimum tack coat material and application rate. Based on the statistical analysis of the interface bond strengths provided by various tack coat types at different application rates, both CRS-2P and CRS-2L were identified as the optimum tack coat types among the eight tack coats considered in this study. The preliminary test results indicated that CRS-2P emulsion provided the highest interface bond strength at the test temperature of 25 deg C (77 deg F) whereas CRS-2L provided the highest interface bond strength at the test temperature of 55 deg C (131 deg F), both at an optimum residual application of 0.09 l/sq m(0.02 gal/sq yd). In addition, it was found that shear resistance at the interface increased significantly with an increase in vertical load and decreased with an increase in temperature
Influence of asphalt tack coat materials on interface shear strength
No full textAsphalt tack coat is a light application of asphalt, usually diluted with water. It is used to ensure a bond between the surface being paved and the overlying course. Normally, hot asphalt cements, emulsified asphalts, or cutback asphalts are used as tack coats. The objective of this study was to evaluate the practice of using tack coats through controlled laboratory simple shear tests and determine the optimum application rate. The influence of tack coat types, application rates, and test temperatures on the interface shear strength was examined. Four emulsions (CRS 2P, SS-1, CSS-1, and SS-1h) and two asphalt binders (PG 64-22 and PG 76-22M) were selected as tack coat materials. The residual application rates considered were 0.00 (0.00), 0.09 (0.02), 0.23 (0.05), 0.45 (0.1), and 0.9 (0.2) L/m2 (gal/yd2). A simple shear test was performed to determine the shear strength at the interface at two test temperatures, 25°C (77°F) and 55°C (131°F). The results indicated that CRS-2P emulsion was the best tack coat type and 0.09 L/m2 (0.02 gal/yd2) was the optimum application rate at which a maximum interface shear strength was measured for both test temperatures
Tack of Butyl and Natural Rubbers
No full textAbstract
A comparative study of the tack of Butyl and natural rubbers was made by contacting freshly cut surfaces of the compounds under various time-temperature-pressure conditions and measuring the force required to separate the splice. The temperature of the knife used to cut the samples was found to be of primary importance. The tack of Butyl compounded with 50 parts of semireën-forcing carbon black (no curatives) decreases regularly with increasing knife temperature. Both longer time and higher pressure of contact favor better splicing. Data are presented on the effect of various plasticizers and carbon blacks on the tack of Butyl compounds.</jats:p
Adhesion-cohesion balance of prepreg tack in thermoset automated fiber placement. Part 2: Ply-ply cohesion through contact formation and autohesion
No full textContact formation and autohesion with respect to their role as the major mechanisms governing the tack between thermoset prepregs in automated fiber placement were explored. Therefore, a novel 90° peel test with strictly separated and individually controllable compaction and debonding phases was employed for experimental tack characterization in a rheometer. Variation of compaction pressure, dwell time and temperature enabled the experimental isolation of contact formation and autohesion influences. The experimentally determined tack, ply-ply contact area and resin viscoelastic characteristics were used to parametrize simplified semi-empirical bond strength sub-models that have originally been developed for thermoplastic composite manufacturing techniques. The model prediction was validated successfully within the experimentally reproducible parameter range. Eventually, manufacturing scenarios for thermoset automated fiber placement (AFP) respecting different lay-up velocities (up to 1 m s−1), compaction pressures (up to 10 N mm−2) and both lay-up and mold temperatures (20–60 °C) were assessed in terms of estimated prepreg tack. The implication of both mechanisms, contact formation and autohesion, in the evolution of prepreg tackiness was found to be able to replicate the bell-shaped tack curves proposed by the adhesion-cohesion balance
Experimental study of the effect of tack coats on interlayer bond strength of pavement
No full textThe performance and lifetime of the flexible asphalt pavement are mainly dependent on the interfacial bond strength between layer courses. To enhance the bond between layers, adhesive materials, such as tack coats, are used. The tack coat itself is a bituminous material, which is applied on an existing relatively non-absorbent surface to ensure a strong bond between the old and newly paved layer. The primary objective of this study was to evaluate the effects of various types of tack coat materials on interlayer bond strength and to determine the optimal application rate for each type. The tack coat types used in this paper were RC-70, RC-250, and CSS-1h. Both laboratory-prepared and field-constructed hot mix asphalt concrete pavements using the tack coats were tested for the binding strength between the layers. A direct shear test was used for the testing. The results obtained from the study showed that the optimum application rate for RC-70 was 0.1 L/m2, and for RC-250, it was 0.2 L/m2, while the optimum application rate for CSS-1h was 0.1 L/m2. From the field test, the optimum application rate of the RC-250 tack coat was 0.1 L/m2
Account Statement for Clothing and Horse Tack, April14, 1871
No full textThis handwritten account statement lists clothing items and horse tack purchased by Thomas L. Darden from June to August 1869 at a cost of sixteen dollars and thirty-five cents. The items were purchased from M. Rubel and payment was received April 14, 1871.https://scholarsjunction.msstate.edu/mss-darden-papers/1246/thumbnail.jp
Discerning autotrophy, mixotrophy, and heterotrophy in marine TACK archaea from the North Atlantic
No full textDNA stable isotope probing (SIP) was used to track the uptake of organic and inorganic carbon sources for TACK archaea(Thaumarchaeota/Aigarchaeota/Crenarchaeota/Korarchaeota) on a cruise of opportunity in the North Atlantic. Due to water limitations, duplicate samples from the deep photic (60–115 m), the mesopelagic zones (local oxygen minimum; 215–835 m)and the bathypelagic zone (2085–2835 m) were amended with various combinations of12C- or13C-acetate/urea/bicarbonate to assess cellular carbon acquisition. The SIP results indicated the majority of TACK archaeal operational taxonomic units(OTUs) incorporated13C from acetate and/or urea into newly synthesized DNA within 48 h. A small fraction (16%) of the OTUs, often representing the most dominant members of the archaeal community, were able to incorporate bicarbonate in addition to organic substrates. Only two TACK archaeal OTUs were found to incorporate bicarbonate but not urea or acetate.These results further demonstrate the utility of SIP to elucidate the metabolic capability of mesothermal archaea in distinct oceanic settings and suggest that TACK archaea play a role in organic carbon recycling in the mid-depth to deep oceanVirginia Institute of Marine Scienc
MEASUREMENT OF THE VIBRATION-ROTATION SPECTRUM OF THE HYDROXIDE ANION () BY VELOCITY MODULATION LASER SPECTROSCOPY
No full text. T. J. Lee and H. F. Schaefer III, J. Chem. Phys. 83, 1784 (1985). 2. H.-J. Werner, P. Rosmus, and E.-A. Reinsch, J. Chem. Phys. 79, 905 (1983). 3. P.A. Schulz, R.D. Mead, P. L. Jones, and W.C. Lineberger, J. Chem. Phys. 77, 1153 (1982). 4. N.H. Rosenbaum, J. C. Owrutsky, L. M. Tack, and R.J. Saykally, J. Chem. Phys. (accepted). Address of Rosenbaum, Owrutsky, Tack, and Saykally: Department of Chemistry, University of California, Berkeley, CA 94720.Author Institution:Guided by the ab initio predictions for the fundamental made by Lee and Schaefer (1) and by Werner, Rosmus, and Reinsch (2) along with the laser photodetachment results of Schulz et al. (3), we measured the band of and by velocity modulation spectroscopy with a color center laser (4). The concentration was found to be maximized in a or discharge where the addition of argon both rotationally heats the and increases its overall concentration. The signal was also found to be dramatically dependent on the presence of metal sputtered on the discharge cell wall. The and bands were analyzed separately with a least squares analysis yielding the equilibrium bond length and vibration-rotation constants through sextic distortion terms. Using the band origins of the two isotopomers, the harmonic vibrational frequencies and first order anharmonicities were calculated
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