Name: standard test method astm d 7998-19 for the cohesive strength development of wood adhesives
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Description: Watch this Scientific Journal Video about Standard Test Method ASTM D 7998-19 for the Cohesive Strength Development of Wood Adhesives at JoVE.com

This work was supported by the&#160;United Soybean Board grant&#160;1940-352-0701-C and the U.S.&#160;Department of Agriculture\Forest&#160;Service. We appreciate the support and detailed information&#160;from Phil Humphrey of AES.

1. Preparation of substrates
<ol>
	<li>Use a substrate surface that is suitable for the application. For wood, use a sliced veneer of about 0.6 to 0.8 mm thick from a reliable producer because these veneers are used for plywood and laminated veneer lumber (LVL) manufacturing. These are obtained from a veneer supplier, as sheets of 0.6 to 0.8 mm thickness and cut into 305 mm on a side. A consistent substrate is a hard maple (Acer saccharum) face veneer because of its surface smoothness and consistent thickness,...

<ol>
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E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+device+to+test+adhesive+bonds.">A device to test adhesive bonds.</a> U.S. Patent. , (2003).</li><li>Humphrey, P. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temperature+and+reactant+injection+effects+on+the+bonding+kinetics+of+thermosetting+adhesives.">Temperature and reactant injection effects on the bonding kinetics of thermosetting adhesives.</a> Wood adhesives. , (2005).</li><li>Humphrey, P. E., Frihart, C. R., Hunt, C., Moon, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Outline+Standard+for+Adhesion+Dynamics+Evaluation+Employing+the+ABES+(Automated+Bonding+Evaluation+System)+Technique.">Outline Standard for Adhesion Dynamics Evaluation Employing the ABES (Automated Bonding Evaluation System) Technique.</a> International Conference on Wood Adhesives 2009. , 213-223 (2010).</li><li>ASTM International. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> D 7998-19 Standard Test Method for Measuring the Effect of Temperature on the Cohesive Strength Development of Adhesives using Lap Shear Bonds under Tensile Loading, in Vol. 15.06. , (2019).</li><li>Rohumaa, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+influence+of+felling+season+and+log-soaking+temperature+on+the+wetting+and+phenol+formaldehyde+adhesive+bonding+characteristics+of+birch+veneer.">The influence of felling season and log-soaking temperature on the wetting and phenol formaldehyde adhesive bonding characteristics of birch veneer.</a> Holzforschung. 68 (8), 965-970 (2014).</li><li>Rohumaa, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+Log+Soaking+and+the+Temperature+of+Peeling+on+the+Properties+of+Rotary-Cut+Birch+(Betula+pendula+Roth)+Veneer+Bonded+with+Phenol-Formaldehyde+Adhesive.">Effect of Log Soaking and the Temperature of Peeling on the Properties of Rotary-Cut Birch (Betula pendula Roth) Veneer Bonded with Phenol-Formaldehyde Adhesive.</a> Bioresources. 11 (3), 5829-5838 (2016).</li><li>Smith, G. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+some+process+variables+on+the+lap-shear+strength+of+aspen+strands+uniformly+coated+with+pmdi-resin.">The effect of some process variables on the lap-shear strength of aspen strands uniformly coated with pmdi-resin.</a> Wood and Fiber Science. 36 (2), 228-238 (2004).</li><li>Pizzi, A., Pizzi, A., Mittal, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Urea-formaldehyde+adhesives.">Urea-formaldehyde adhesives.</a> Handbook of Adhesive Technology. , 635-652 (2003).</li><li>O'Dell, J. L., Hunt, C. G., Frihart, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+temperature+performance+of+soy-based+adhesives.">High temperature performance of soy-based adhesives.</a> Journal of Adhesion Science and Technology. 27 (18-19), 2027-2042 (2013).</li><li>Frihart, C. R., Beecher, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Factors+that+lead+to+failure+with+wood+adhesive+bonds.">Factors that lead to failure with wood adhesive bonds.</a> World Conference on Timber Engineering 2016. , (2016).</li><li>Hunt, C. G., Frihart, C. R., Dunky, M., Rohumaa, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Understanding+wood+bonds:+going+beyond+what+meets+the+eye.">Understanding wood bonds: going beyond what meets the eye.</a> Reviews of Adhesives and Adhesion. 6 (4), 369-440 (2018).</li><li>Frihart, C. R., Dally, B. N., Wescott, J. M., Birkeland, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bio-Based+Adhesives+and+Reliable+Rapid+Small+Scale+Bond+Strength+Testing.">Bio-Based Adhesives and Reliable Rapid Small Scale Bond Strength Testing.</a> International Symposium on Advanced Biomass Science and Technology for Bio-based Products. , (2009).</li></ol>

Critical steps in the procedure are as follows: selection of substrates, preparation of specimens, operability of the equipment, and bonding of samples.
The substrate must be strong, have minimal defects (smooth, flat, no cracks and no discoloration. Unsanded, rotary cut cabinetry face veneer of a diffuse porous hardwood with sugar maple (Acer saccharum) preferred. Sanding creates a less even and more fragmented surface7. After conditioning the veneer at 21 &#1...

Wood bonding is the largest single adhesive market and has led to efficient use of forest resources. For many centuries, solid wood was used for most applications, except for furniture construction, with no test criteria except product in-use durability. However, bonded wood products became more common, starting with plywood and glulam beams, using bio-based adhesives1,2. Although these products were satisfactory at the time, the replacement of soy, casein, and blood glues by synthetic adhesives containing formaldehyde led to improved properties. The higher performance of these new adhesives led to defined testing standards with higher performance expectations than achievable with most bio-based adhesives. The synthetic adhesives also made possible the bonding of particles including sawdust to form particleboards, fibers to form fiberboards with varying densities, chips to provide oriented strandboard and parallel strand lumber, veneers to yield plywood and laminated veneer lumber, as well as finger jointed lumber, glulam, cross laminated lumber, and wood I-joists3. Each of these products have their own testing criteria4. Thus, the development of a new adhesive can require a lot of formulation work and extensive testing to determine if there is any potential for developing sufficient strength. This time-consuming testing and the complexity of wood properties and wood bonding5 has limited the development of new adhesives. In addition, the mechanical properties of wood adhesives can be different when cured between wood surfaces as opposed to neat6. Curing in contact with wood allows water and low molecular weight components from the adhesive to escape, in addition to complex interphase and chemical interactions of the adhesive with the wood3,7.
The development of the Automated Bonding Evaluation System (ABES) has been very helpful for understanding the strength development of wood adhesives because it is rapid and easy to use8,9,10. The system is an integral unit that bonds lap-shear samples and then measures the force under tension needed to break the bond. Its utility has led to development of ASTM method D7998-19 that uses this system11. Although this system was originally designed to measure adhesive strength development as a function of temperature and time, it can also measure the heat resistance of cured adhesives, as well as routine bond strength evaluation. Although the ABES test is a very useful preliminary screening tool, like any test, it has its limitations and does not replace all specific product strength and durability testing.
While there are many means of gauging the curing characteristics of adhesives, ranging from gel-time rheometry to differential scanning calorimetry, dynamic mechanical analysis, and spectroscopy of many types, only the ABES method measures the development of mechanical strength. This requires an instrument that is tightly controlled for heating, cooling, and in-place tensile testing11.

<table>
	<tbody>
		<tr>
			<td>Adhesive</td>
			<td>Supplied by user</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Balance</td>
			<td>Normal supply house</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Mark II Automated Bonding Evaluation System (ABES-II)</td>
			<td>Adhesive Evaluation Systems Inc</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pneumatically driven sample cutting device</td>
			<td>Adhesive Evaluation Systems Inc</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Regular spatula</td>
			<td>Normal supply house</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Wood supply &#8211; Hard maple</td>
			<td>Besse Forest Products Group</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

standard test method astm d 7998-19 for the cohesive strength development of wood adhesives

The properties of cured wood adhesives are difficult to study because of the loss of water and other components to the wood, the influence of wood on the adhesive cure, and the effect of adhesive penetration on the wood interphase; thus, normal testing of a neat adhesive film is generally not useful. Most tests of wood adhesive bond strength are slow, laborious, can be strongly influenced by the wood and do not provide information on the kinetics of cure. Test method ASTM D 7998-19, however, can be used for fast evaluation of the strength of wood bonds. The use of a smooth, uniform, and strong wood surface, like maple face-veneer, and sufficient bonding pressure reduces the adhesion and wood strength effects on bond strength. This method has three main applications. The first is to provide consistent data on bond strength development. The second is to measure the dry and wet strengths of bonded lap shear samples. The third is to better understand the adhesive heat resistance by quickly evaluating thermal sensitivity and distinguishing between thermal softening and thermal degradation.

The procedure has been used extensively for the study of protein adhesives at the Forest Products Laboratory. It has been found that less than 2 MPa wet bond strength was insufficient to warrant further wood adhesive testing, while greater than 3 MPa was a promising result for further testing19. It has been shown to be useful in demonstrating sensitivity of wood processing conditions12,13. Further examples can be found in Frihart publicati...

Watch this Scientific Journal Video about Standard Test Method ASTM D 7998-19 for the Cohesive Strength Development of Wood Adhesives at JoVE.com

Standard Test Method ASTM D 7998-19 for the Cohesive Strength Development of Wood Adhesives

We present a procedure, ASTM D7998-19, for a rapid and more consistent evaluation of both dry and wet strength of adhesive bonds on wood. The method can also be used to provide information on strength development as a function of temperature and time or strength retention up to 250 &#176;C.

The properties of cured wood adhesives are difficult to study because of the loss of water and other components to the wood, the influence of wood on the ...

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