STATUS OF INSULATING GLASS SEALANTS IN THE UNITED STATES

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1 STATUS OF INSULATING GLASS SEALANTS IN THE UNITED STATES J. R. PANEK Yardley, USA 1 Summary The increasing cost of energy has emphasised the need for insulation and insulating glass in the last 15 years. The high rise buildings require high performance units where cost is no object both in the north from the cold and the south from the heat. Long term performance is desired at low replacement cost. Here butyl/silicone give the optimum performance. However, this area only comprises about 33% of the total market, while the remainder goes into housing and replacement units on housing. This area is dominated by polysulphide at about 45% of this market with hot melt butyl, polyurethane, and others competing for this market. The total market in 1986 was about 47 million lbs of sealant. Permapol which is a sealant system based on a mercaptane terminated urethane and Swiggle strip which is a patented all inclusive spacer-desiccant-butyl strip are more recent systems in this market area. 2 History Polysulfide rubbers in paste form were first used in making insulation glass units as early as 1975 in Canada where insulation glass was necessary. It was not until the late 40 s that liquid polymers became available and were used instead. This market was developed in Canada but by the early 60 s had become a factor in the US. The quality of the units left much to be desired and the reputation of the industry was at stake. A group of manufacturers decided to form SIGMA (Sealed Insulation Glass Manufacturers Association) in the 60 s in order to establish minimum quality standards for this industry. By 1975 the market for insulation glass had grown to 12.5 million lbs of sealants with polysulphide having close to 85% of the market. Butyl hot melts were becoming a factor but proper equipment for extruding the hot melt compounds was lacking and equipment for extruding sealant at 300F was still not available. What was available caused problems with spacer sagging with larger units because of poorer quality sealant. H.B. Fuller developed equipment, which solved this problem, and by 1981 butyl hot melts had a market of 3 million lbs of sealant. By 1981 butyl/silicone had reached 2 million lbs of sealant and Permapol, which was developed in the early 70 s, had reached sales of 1 million lbs in Urethanes were first tried in the middle 70 s but the sealants were not satisfactory until the systems were changed to a 100% polymer system with no solvent. In 1981 urethane had a 1 million lb market.

2 3 Discussion Table 1 shows the volumes of the various synthetic polymers used, including predictions for Table 1. Insulating glass sealants (millions of lbs) Polysulfide ,5 12 Butyl hot melt Silicone sm Urethane sm Polyisobutylene 0,5 1 1,5 2 Permapol sm 1 3,5 5,5 Swiggle strip Total The architect has cognisance of high quality units for high rise buildings and this is where butyl/silicone has its greatest demand, but this market is about 33% of the total sealant market. Other sealant systems, which also compete for this area, include polysulphide, butyl/polysulphide, urethane, butyl/urethane, some hot melts, Permapol, and Swiggle Strip. The largest area is the home market and replacement windows and this is where hot melts along with the others are more readily used. This is a competitive area and price as well as availability play an important part. It is expensive to ship units to a greater distance so that this explains the large number of unit manufacturers in the US. At the moment there may be as many as 1000 manufacturers in the States. Since the total production of these companies greatly surpasses production demands, it is not surprising to find that about a third have been in business more than 5 years, one third have been in the business for less than 5 years and one third will be out of business in several years. Part of the reason for companies going out of business is a planned strategy. Companies give a long term guarantee but go out of business before any of their units begin to fail. Surprisingly, many of these same companies reorganise under a new name and are back in business same as usual. The units supplied by these fly-by-night companies find their way into new construction and the home owner has no idea who made the units when they failed or who to sue. By that time the home warranty has expired and the home owner is out on his own. There are many good quality houses that take pride in their work, and usually the larger manufacturer makes good quality units. But there are many companies whose guarantee is only as good as the distance to the door. Over the years the sealant supplier was also involved in making equipment available to the smaller manufacturer and also supplied assistance in keeping the equipment running. Some companies had mechanics that spent a good deal of their time repairing and keeping equipment running. This was a part of technical service, and a means of maintaining sales. H. B. Fuller, a manufacturer of hot melt butyl compounds was instrumental in developing equipment for handling and extruding the compound at 300F onto units in a completely automated assembly. This was necessary in order to de-

3 velop sales and this has reflected in excellent sales of their product. PRC decided to improve on the polysulphide polymer by patenting their own version by introducing a finished sealant on the market based on a mercaptane terminated urethane polymer, which cures up using typical polysulphide chemistry. This has been termed a polysulphide and sometime is included as a polysulphide. This sealant performs better than a Thiokol but also demands a slightly higher price. PRC also makes sealants based on Thiokol polysulphide polymer. Tremco decided to introduce an all-purpose spacer, which included the metal, the desiccant, and the butyl rubber to act as the MVT barrier. This system is called Swiggle Strip. All that is needed is a table, a heater plate and glass. This eliminates the need for spacers, sealant or desiccant. The Swiggle Strip is sold in a roll and protected from the air until used. The Strip is very useful for small volume producers, for odd shapes, but has been put into plant production on a volume basis and supposedly can compete with other systems. 4 Specifications and performance The original specification for I.G. units was developed by Sigma using a test assembly designed by P.R.C. Eventually the specification with modifications was adopted in 1981 by ASTM under the designation E-774 and includes E-773, which is the test method, and E-546, which is the Dew Point Test Method. The requirements of E-774 rate performance in 3 classes are shown in Table 2. Table 2 gives the requirements for the 3 classes covered by ASTM E-774. Table 2. Requirements for classifications Class High humidityaccelerated test - days test cycles C < -30F B (additional) < -20F A (additional) < -20F final dew point In addition the test specimen must exhibit no visible fog for 7 days in the fog test. While there is no correlative of the classification to durability, some people believe the following relationship is valid. Classification Durability - years C 7-10 B A 15 plus The author has tested hundreds of test units involving all the various sealant systems and feels that E-774 is not rigorous enough to differentiate between the various systems. The test cycles that were used by the author consisted of the following: 1. week at 100% RH and continuous UV 2. week at 158f and continuous UV

4 3. week at 100% UV and a low pressure/high pressure cycle of ± 5 inches of water with continuous cycles of 1 cycle every 30 seconds for a solid week 4. week in a weatherometer with 4 cycles daily ranging from -20F to 140F Using the above test cycles in which all units were first placed in cycle No. 1, the best polysulphides both single and dual seal lasted about 16 weeks. Average polysulphides lasted about 8 weeks and poor polysulphides broke down in 1 or 2 weeks. Good hot melt butyl s lasted about 16 weeks, but poorer hot melt compounds only lasted 4-6 weeks. Two urethanes lasted 8 weeks, one urethane only lasted 1 day. Banded dual-seal hot melts lasted over 30 weeks. Butyl/silicone systems lasted over 30 weeks and testing had to be discontinued to make room for other systems. All polysulphide, urethane and hot melt systems eventually failed in adhesion. The butyl/silicone systems never failed in adhesion. The performance of the butyl/silicone units was so superior that production was started at 3 plants in 1974 using the acetoxy silicone with polyisobutylene as the other part of the system. Units tested for dew point on the job site of several buildings a year later gave -90F Dew Point. Molecular sieve was used as the desiccant in these units. This company has changed names and now consists of 6 plants across the US and all plants have been certified for this system with IGCC. 5 General observations The best systems are butyl/silicone using Molecular Sieve desiccant, using welded or soldered corners and made in a low RH environment. There are a number of plants that meet this requirements and several are completely automated to eliminate the human factor. The other extreme is production in an open plant at all times of the year with little attention given to protect the desiccant. The exposure of a frame containing desiccant without RH protection can cause the desiccant to lose 25% of effectiveness in 2 hours until the frame is placed between sheets of glass and sealed. This can be easily proved by checking the efficiency of the sieve by removal and testing according to the Union Carbide test procedure. Poor mixing, improper mixing ratios, and insufficient sealant due to very shallow sealant depth are all factors the lead to poor performance of the unit. One of the biggest problems is poor housekeeping. There are 3 types of manufacturers of units. One group are only interested in the price of sealant. Unless you are lower, you might just as well leave. The second group is the well established manufacturer who sells a good quality unit. He will not change any component unless he has done considerable testing to justify the substitution. The last group contains the newcomers who are looking for service, price, technical data, and credit. 6 Status of insulating glass systems

5 It is estimated that there are about 1000 manufacturers of insulation glass units in the US. Many of these companies are too small to afford to join Sigma and have their units tested and certified by IGCC (Insulation Glass Certification Council). The latest list of certified insulating glass manufacturers in August of 1987 listed 100 companies throughout the US with 162 sealant systems and units approved. Many of these companies have very large capacities and it is estimated that these 100 companies account for about 75% of the total volume of sealant and number of units made. The following table 3 gives the number of companies using various sealant systems, corner treatment, spacer and types of desiccant. Table 3. Components of IG units by number of companies Sealant system used Corner key treatment 20 Polysulfide 89 Nylon key 30 butyl/polysulphide 27 Soldered aluminium key 20 Urethane 14 Die cast key 16 Butyl/urethane 10 Welded corners 17 Butyl hot melt 7 Plastic key 56 Butyl/silicone 5 aluminium key 2 Butyl sealant spacer 5 based sections 1 Butyl/hot melt butyl 5 miscellaneous Swiggle Strip was used as the butyl sealer spacer. All but 1 company used aluminium spacer, the remaining company used a steel spacer. 15 companies used as combination of coated glass and plain glass, the remaining 147 companies used plain glass. 116 companies used straight molecular sieve as desiccant while the remaining 44 used a blend of Molecular Sieve and Silica gel. The Swiggle Strip has the desiccant in the combination spacer. 159 sealant systems passed the requirements for all three classes namely C, B and A. This evaluation shows that the certification system cannot separate between the systems and yet in the opinion of the author the butyl/silicone is vastly superior than any of the others. 7 Predictions The market for insulation glass sealants is expected to grow to 655 million lbs by Polysulfide is expected to drop partly because of the price of the polymer and partly because hot melt butyl and urethane is expected to grow at the expense of polysulphide. Hot melt is cheaper, while urethane may show better performance by formulation improvement. Silicone will increase because of the superior performance of the butyl/silicone system. Permapol and Swiggle Strip will also show growth. Permapol is a better sealant while Swiggle Strip has a lot of versatility. 8 New information

6 Additional information was recently obtained on the Associated Laboratories Inc. list of approved manufacturers and the components used to make their window insulation glass units. This Association is more involved with smaller window units. This Association is more involved with smaller window units and the testing of units for insulation values, which is reflected in the large number of units, approved using HMB (hot melt butyl), butyl (Swiggle Strip) and polysulphide. The total number of manufacturers is approximately 230. Here again the fact that all three classes can be met by the same system indicates that the testing is not severe enough to differentiate between the various polymers used to make the units. The data is summarised in table 4. Table 4. Data Sealant Class ABC Class BC Class C HMB B PIB/PS PS PU PIB/HMB PIB/S PIB/PU Total All Spacers are aluminium Desiccant: MS MS/SG Corners: nylon - 204, zinc - 12, no corners - 20, others - 3 Associated Laboratories Inc. Sealant Class ABC Class BC Class A HMB B (Swiggle) PIB/PS PS PU PIB/HMB PIB/S PIB/PU Total Spacers - Aluminium Desiccant: MS MS/SG Corners: nylon - 204, zinc - 12, others - 23 Insulating glass requirements (ASTM E-774) Class High humidityaccelerated test -Final dew point

7 test - days cycles C < -30F B < -20F A < -20F Also no fog after 7 days in fog test chamber IGCC certification program Sealant Corners Desiccant 20 PS 86 nylon MS PIB/PS 27 soldered MS/SG PU 14 zinc 17 HMB 10 welded 56 PIB/S 7 plastic 2 B (Swiggle) 5 aluminium 17 PIB/PU 5 brazed 5 misc. Note: all systems passed classes C,B,A Insulating glass sealants Polysulfide ,5 12 Hot melt butyl Silicone sm Polyurethane sm Polyisobutylene 0,5 1 1,5 2 Permapol sm 1 3,5 5,5 Swiggle strip Total Note: all values in millions of lbs of sealant.