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Expert Opinion on Current Trends in the Window and Door Seal Market. PART 2.
Sealants are essential components of window and other translucent enclosing structures. How do you choose the right seal—or more precisely, what tests can help you choose the most suitable one? GOST 30778-2001 defines the properties of materials used to manufacture seals, and GOST 31362-2007 evaluates the durability of seals, measured by their resistance to operational impacts. Both GOSTs are undoubtedly important when choosing a seal type, as the former defines the characteristics of the seal itself—primarily elasticity and recovery at low and high temperatures—while the latter determines the preservation of key seal performance indicators when exposed to environmental factors. These include UV radiation from the sun, low temperatures, and simulated precipitation.
Seal-related complaints during the first two years usually arise from air leaks or leaks caused by precipitation. Most often, this is due to improper corner formation and poor seal recovery during cold weather. The composition of the seal material has a key impact on its performance, but the seal geometry can also be decisive. In our experience, the seal material and seal design account for 70% of the seal’s performance in a structure, and 30% depends on the design of the structure itself.
Extensive experience in developing seals and polymer compounds has allowed us to identify the most critical seal test methods that simulate real-world performance in a structure. These include:
- Shrinkage along the length of the seals at elevated temperatures in an oven. According to GOST 31362-2007, shrinkage should not exceed 3%; less than 1% is considered good, and 0.2–0.3% is ideal. However, we have encountered many seals with values exceeding 4–5%.
- Seal cracking under compression at high temperatures. This indicator is not specified in GOST, but it is a common occurrence in practice. We simulate this cracking during deformation by winding the seal and applying compression.
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| Fig. 1 Preparation of samples for high temperature cracking tests. | Fig. 2 Cracking of samples of poor-quality sealant. | Fig. 3 Cracking and shrinkage of the glass unit seal at the facility. |
The seal is compressed to the minimum allowable gap between the frame and the sash; for different window systems this value varies, but is usually about 3 mm. Compression is carried out at a temperature of +70°C and at a temperature of -30°C. Residual deformation under compression (RDC) according to GOST 31362-2007 is a characteristic of the seal expressed as the ratio of the irreversible deformation during the test (compression or tension) to the maximum deformation. Residual deformation under compression at negative temperatures (-30°C) for 24 hours, relaxation for 30 minutes in an open clamp in an alcohol medium. A characteristic of the seal expressed as the ratio of irreversible deformation during the test (compression or tension) to the maximum deformation. Simulation of seal recovery when opening the window sash in winter, as well as air leakage through the seal due to reduced elastic recovery.
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| Fig. 4 Preparation of samples for static compression deformation testing. | Fig. 5 Relaxation in sprit at minus 30°C of samples after 24 hours of static compression at minus 30°C. | Fig. 6 Relaxation at +25°C of samples after 24 hours of static compression at minus 30°C. |
Table 1. Results of the ODS after testing for static compression deformation of seals.
| Марка | Height before testing, mm | ODS, at 70°C, %, relaxation 30 min at 25°C, % | ODS, at -30°C,%, relaxation 30 min at -30°C, % | ODS, at -30°C, %, relaxation at 30 min +25°C, % |
| 1. TPE sample | 6,3 | 37,2 | 68,9 | 11,3 |
| 2. LCS sample | 6,4 | 23,5 | 60,2 | 5,2 |
| 3. EPDM sample | 6,5 | 43,0 | 76,3 | 22,3 |
| 4. LCS sample | 6,4 | 24,4 | 60,5 | 6,9 |
| 5. TPE sample | 6,4 | 33,9 | 68,9 | 8,5 |
A new method for evaluating the ability of samples to recover after stretching according to ASTM D1329. The RT (Retraction Tester) test is a testing method for evaluating seal recovery at low temperatures. Before the cooling procedure, the sample is stretched. In the second stage, the stretched seal sample is cooled to -70°C, then the load is removed and the sample is heated at a rate of 1°C/min until it reaches room temperature (+25°C). The temperature at which the sample recovers 10%, 30%, 50%, and 70% of its original length is recorded — respectively indicators TR10, TR30, TR50, and TR70. These values are shown in the table below, showing the elastic behavior of the seal at low temperatures.
ODS, at 70°C, %, relaxation 30 min at 25°C, %
Fig. 7 Retraction tester.
Fig. 8. RT test results.
Organoleptic test. Unpleasant odor, excessive soot content, and imprint on the profile. With large glazing areas, the amount of sealant present in the room increases critically. Low-quality sealant formulations emit a persistent rubbery odor in the room, especially pungent in hot, sunny weather.
Fig. 9. Soot stain test.
The presence of qualified personnel and a fully equipped laboratory makes it possible to conduct a complex of comparative tests of the seal. The engineering staff and the laboratory of the Standard Prof Factory regularly carry out seal tests free of charge for their partners. In real conditions of limited resources, it is often easier for the consumer to distinguish between high-quality and low-quality seals by the type — TPE or EPDM. However, the experience of recent years, numerous tests carried out, and the tests presented above show that high-quality TPE exceeds low-quality EPDM seal in terms of properties. Traditionally, rubber is considered better in elasticity, but the LCS series seals show a stable superiority in property levels over EPDM seals according to GOST 30778-2001 and GOST 31362-2007. The proven durability of LCS seals is more than 20 years under testing conditions for EPDM rubbers (IVM — cold climate).
PhD, the CEO of the Standard Prof Factory
Vasilii Novokshonov
