27 июля, 2015 
Malyar Recommended use temperature for dry animal glues and compounded products (except liquid glues) in most applications is 140 to 145°F (60 to 63°C). A range of 135 to 155°F (57 to 68°C) is acceptable but not preferred. Use at lower temperatures results in undesirable properties such as high viscosity, poor machinability, excessive glue use, and premature gelation, resulting in bond failure. Use at temperatures that are too high causes excessive water loss and degradation of the glue by heat hydrolysis. Excessive dilution of a glue solution to retard gelation is a bad practice that can result in a ‘‘starved’’ bond with insufficient glue to adhere. Use of a lower grade of glue or a gel depressant is indicated. Dry glues and compounded dry blends for adhesive use are usually prepared at 25 to 55% solids. Compounded cake glues are used as is, or diluted up to 20% with water. The amount of water used depends on glue grade, speed of operation, and type of material to be bonded.
Four basic steps for adhesive applications are as follows:
1. Deposit a thin, continuous glue film on one of the surfaces to be bonded.
2. Allow the glue film to become tacky (transition point from liquid to gel) before applying pressure.
3. Apply uniform pressure to ensure complete contact between surfaces to be bonded.
4. Continue pressure long enough to ensure a strong initial bond.
Grade selection for many uses involves consideration of the desired viscosity and gel properties for the specific end use. High test grades have the greatest water-taking properties, high viscosity, rapid gel formation and strength, fast speed of set, and greatest reactivity with insolubilizing materials. Low test grades have long tack life and open time, slow rate of gel formation and set, and best film-forming properties at high solids. Medium test grades provide intermediate properties. Grade selection for adhesive use generally involves matching the gelation rate of the animal glue solution with the time from the application of the glue film to the bonding of the substrates (open time). The gelation rate and viscosity of animal glue solutions are usually closely related.
|
Glue Concentration (%) |
High Test (155 mP) |
Medium-High Test (102 mP) |
Medium Test (63 mP) |
Low Test (32 mP) |
|
5 |
3.0 |
2.4 |
2.0 |
1.6 |
|
10 |
8.8 |
5.6 |
3.6 |
2.6 |
|
12.5 |
15.5 |
10.2 |
6.3 |
3.2 |
|
15 |
28.0 |
17.2 |
8.4 |
5.0 |
|
20 |
79.0 |
46.0 |
22.4 |
10.0 |
|
25 |
196 |
112 |
49.6 |
19.6 |
|
30 |
524 |
264 |
108 |
37.6 |
|
35 |
1,360 |
612 |
224 |
72.0 |
|
40 |
3,216 |
1,320 |
476 |
133 |
|
50 |
16,320 |
7,240 |
2,400 |
566 |
|
Source: Ref. 10, p. 146. Table 4 illustrates the viscosity in centipoise at 140°F for solutions of dry glues of given test and millipoise value [10]. |
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