Rolling tack

Figure 8.18. (a) Rolling tack test (b) peel test (c) low angle heal test. 

In the same way that natural mbber is predominandy used in blends, it is also predominandy used in tire manufacture. Its excellent building tack, low heat buildup, low rolling resistance, and good low temperature performance make it the polymer of choice for many parts of tire constmction, for both passenger and tmck vehicles. The effects of radiali2ation and demand for low rolling resistance and good low temperature performance have all tended to benefit natural mbber, especially in tmck tire constmction, as shown in Table 9. 

In another tack test, a steel ball of specified diameter is rolled down a grooved incline onto a conditioned surface area of pressure sensitive adhesive (ASTM D 3121, PSTC-6). The length of travel before it stops is the rolling ball tack (Fig. 2d) reported in millimeters. It is relatively inexpensive and simple to set up. Similar test variables to the probe tack test apply. 

Fig. 2. Tack tests and results, (a) Probe tack, (b) Probe tack vs. temperature for a natural rubber PSA. (c) Loop tack, (d) Rolling ball.

Rolling ball. A small steel ball with specific weight and diameter is rolled down an inclined plane onto a thin film of adhesive placed at the bottom. The distance the ball rolls on the adhesive film before stopping is a measure of the tack (the longer the distance, the lower the tack). 

First, roll out the fabric and secure it, either by digging it into the ground or by tacking it down with large landscaping staples. 

A large proportion of the circa 3.7 x 106 t/yr of natural mbber used in tires is consumed in tmck tires, off-the-road tires, and aircraft tires, all of which demand a low heat buildup performance. The retreading of tmck tires was also the province of natural mbber until the precured process was developed. Prior to the advent of this technique, the tack of natural mbber was essential for the unvulcanized mbber to adhere onto the buffed carcass, and the thickness of the shoulder region was such that the low heat buildup of natural mbber was essential to ensure that no failure occurred in service. With the precured tread process neither of these attributes were necessary and, synthetic mbber, which was and continues to be used, was found to give particularly good wear performance under low severity conditions, especially in the United States. However, work (56) has shown that natural mbber-based formulations can be developed which give a similar order of wear performance to the all-synthetic mbber tread, but with the additional benefit of lower rolling resistance, and hence better fuel economy. 

The methods to evaluate PSAs include the rolling ball test (ASTM D3121, PSTC-6, BS EN 1721), loop tack test (ASTM D6195, FINAT Test Method 9, BS EN 1719), and quick stick test (PSTC-S). ... 

Tack cement - A formulated rubber/cement mixture which can be rolled or brushed on surfaces which will hold the rubber panel in place until cure takes place. Normally considered a part of the adhesive system. 

D 3121 Test Method for Tack of Pressure Sensitive Adhesives by Rolling Ball... 

PSA Formulation and Properties. The formulations used in this study for the Hycar 2103-Prepolymer C and Hycar 2106-Prepolymer C PSA contain OH/NCO ratios of 1.7 and 1.3, respectively. Dibutyltin dilaurate catalyst is used at a 0.2 wt.% level based on the total adhesive solids. PSA samples are made from an 80% solids solution (by wt.) with a dry solvent system (27/73 by wt. of ethyl acetate-toluene) and cured at 150°C for 45 seconds. The samples are then evaluated by running 180° peel, static shear, rolling ball tack, and vinyl film shrinkage tests. 

These adhesive systems give an excellent combination of static shear (at both room temperature and 70°C) and rolling ball tack along with excellent vinyl film shrinkage resistance. The results of these tests are summarized in Table III. 

Performance Flexibility. Figure IV illustrates the effect of the 0H/NC0 ratio of 180° peel strength and rolling ball tack for both the Hycar 2103-Prepolymer C and Hycar 2106-Prepolymer C adhesive systems. Peel strength values of 493 N/m (45 oz./in.) or lower are possible for the Hycar 2103 system simply by altering the 0H/NC0 ratio. Likewise for the Hycar 2106 system, peel strengths of 657 N/m (60 oz./in.) or lower are possible. 

In both cases, rolling ball tack remains relatively constant unless the 0H/NC0 ratio becomes too low. In addition, no creep in static shear is observed at room temperature or 70°C at the ratio shown. 

Figure V demonstrates the effect of adhesive dry coating weight on 180° peel strength and rolling ball tack with OH/NCO ratios of 1.7 and 1.3 for Hycar 2103 and Hycar 2106, respectively. Static shear tests run both at room temperature and 70°C show no creep for both systems throughout the thickness range tested.

Only at low adhesive coating weight does the rolling ball tack begin to increase slightly. 

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