Adhesion on Substrates Used in the Building Industry

In this section, adhesion durability under severe conditions (immersion in 80°C water) of two-component tin catalyzed sealants (DC 993 and DC opt) and a one – part titanate catalyzed sealant (DC 895) are compared. Pyrosil® treatment was used as a dry primer.

The peel adhesion tests are shown in Table 5.

Despite the improvement in the adhesion build up by the use of a primer (Pyrosil®) or by the use of the adhesive formulation optimized for adhesion build up (DC opt), this improvement is not confirmed after immersion in hot

Copyright by ASTM Int’l (all rights reserved); Tue May 6 12:07:08 EDT 2014 Downloaded/printed by

Rochester Institute Of Technology pursuant to License Agreement. No further reproductions authorized.

TABLE 4—Tensile strength after accelerated ageing with low E coated glass (*: glass breakage).

Tensile Strength

Coated No Primer (MPa)

Edge Del. No Primer (MPa)

Coated 1200 OS (MPa)

Coated

Pyrosil

(MPa)

Edge Del. Pyrosil (MPa)

1 week RT

0.94

>0.70*

0.87

1.00

1.02

3 weekWI(55°C)

>0.65*

0.75

>0.67*

0.84

7 week WI (55°C)

0.58

0.60

0.60

0.68

0.56

6 week WI (45°C)

0.77

0.89

0.84

0.89

0.84

1000 h 85°C/85 % RH

0.79

0.85

0.82

0.95

0.94

2000 h 85°C/85 % RH

0.93

0.91

0.90

0.85

0.84

1000 h QUVa

0.93

>0.60*

>0.90*

>0.70*

>0.50*

2500 h QUVa

0.87

0.83

5000 h QUVa

0.94

0.89

0.80

0.79

0.98

aFor the QUV accelerated ageing, a QUV accelerated weathering tester was used with UVA-340nm lamps; the weathering cycle used was 4 hours irradiation at 340nm and 60 °C followed by 4 hours condensation.

water, indicating that the benefit of the primer is more for the adhesion buildup

than for the durability.

Tensile strengths and percentage of cohesive failure (% CF) for mixed glass – anodized aluminum H-bars (12 mm x 12 mm x 50 mm) are given in Table 6. The results confirm the severity of the test in 80°C water since the results are

TABLE 5—Peel adhesion after immersion in 80°C water.

Condition

Material

Glass

GS

AMF

SS

AA

7 day cure

DC 993

CF

AF

AF

AF

CF

DC 993 + Pyr

CF

CF

CF

CF

CF

DC opt

CF

CF

CF

CF

CF

DC 895

CF

CF

AF

CF

CF

DC 895 + Pyr

CF

CF

CF

CF

CF

2 week 80°C

DC 993

CF

CF

CF

AF

CF

DC 993 + Pyr

CF

CF

CF

AF

CF

DC opt

AF

AF

CF

AF

CF

DC 895

CF

AF

CF

AF

CF

DC 895 + Pyr

CF

CF

CF

AF

AF

4 week 80°C

DC 993

AF

CF

CF

AF

CF

DC 993 + Pyr

AF

CF

CF

AF

CF

DC opt

AF

AF

AF/CF

AF

AF

DC 895

CF

AF

AF/CF

AF

AF

DC 895 + Pyr

CF

CF

CF

AF

AF

TABLE 6—Tensile strengths of H-bars after water immersion.

Condition

Mat

Tensile MPa

%CFa Gl

%CFa Al

4 week cure RT

DC 895

1.30

95

100

DC 895 + Pyr

1.32

90

100

DC 993

1.10

100

100

DC 993 + Pyr

1.00

100

100

6 week WI45° C

DC 895

1.20

90

100

DC 895 + Pyr

1.05

60

100

DC 993

1.05

100

100

DC 993 + Pyr

1.02

100

100

1 week WI 80° C

DC 895

0.77

57

95

DC 895 + Pyr

0.80

30

100

DC 993

0.75

98

100

DC 993 + Pyr

0.73

67

100

2 week WI 80° C

DC 895

0.75

48

95

DC 895+Pyr

0.77

30

100

DC 993

0.61

0

95

DC 993 + Pyr

0.57

0

100

3 week WI 80 °C

DC 895

0.68

33

95

DC 895+Pyr

0.71

20

100

DC 993

0.40

0

100

DC 993 + Pyr

0.32

0

100

aa 30 %CF Gl, for instance, means Glass surface shows 70% adhesive failure.

worse after one week than after 6 weeks in 45°C water. Although the titanate- catalyzed 1K sealant shows faster partial loss of adhesion on glass, some adhe­sion is maintained longer than observed for 2K systems. Again, no effect of the primer on the adhesion durability could be measured. In hot water immersion, adhesion on anodized aluminum seems to be much better than on glass.

Conclusion

When no adhesion occurred with a specific silicone adhesive on a specific sub­strate, the use of the 1200 OS Primer Clear or the dry Pyrosil® primers was shown to improve the speed of adhesion buildup and therefore contributed to the improvement of the adhesive behavior within the initial days after applica­tion. To a lesser extent, the use of a primer also improves adhesion durability, tested after accelerated ageing, on substrates which do not show adhesion in the absence of the primer. Most wet primers have a high volatile organic con­tent compared to the Pyrosil®R burner which only emits carbon dioxide as a by­product. In our study, adhesion buildup could also be improved by modifying the sealant/adhesive formulation.

Copyright by ASTM Int’l (all rights reserved); Tue May 6 12:07:08 EDT 2014

Downloaded/printed by

Rochester Institute Of Technology pursuant to License Agreement. No further reproductions authorized.

However, this study was not able to demonstrate that adhesion durability could be extended by the use of a wet or a dry primer for substrate/formulation combinations which already show good adhesion buildup in the absence of a primer. For those substrate/adhesive combinations, primers show no improve­ment in the ultimate adhesion properties.

This study also shows that accelerated ageing under water immersion at 80°C is extremely severe when compared to more realistic conditions such as 2000 h at 85°C and 85 % relative humidity (% r. h.) or 5000 h under 340 nm irra­diation (QUV).