HXTAL NYL-1 Information Sheet
What is HXTAL?
HXTAL Epoxy Adhesive is an ultra pure resin that remains water white (clear and totally transparent) over a long period of time even with exposure to direct sunlight. This is an exotic and very high-tech adhesive that is far more sophisticated than hardware store epoxy adhesive, although it is a little more than twice the cost of most of these cheaper epoxies.
How to mix HXTAL
HXTAL is supplied in two liquid parts, both of low viscosity. Hxtal epoxy should be weighed out accurately, (1 part by weight of Part B + 3 parts by weight of Part A). This assures the maximum utilization of all the adhesive purchased.
After the two parts have been weighed into a mixing jar, mix it thoroughly with a glass stirring rod. There is no rush during the mixing stage and there will also be plenty of time for the glue to sit while the bubbles rise and pop. Freshly mixed HXTAL is very thin and this is plenty of time to remove the bubbles from the mixture. The best way to do this is to use some kind of a vacuum to suck the air out of the glue.
How to apply HXTAL
Freshly mixed HXTAL has very low viscosity. If it is too thin, let it stand (covered) and it will thicken over a period of several hours. The bond strength of thick or thin HXTAL is the same but various gluing applications may require varied viscosities of the HXTAL. Thin HXTAL will penetrate cracks for some repair applications, making them virtually disappear from view. The best results are obtained when the glass is warmed to about 50° C (a hair dryer or some other heat source is reasonable if the object is not heated too much or too quickly). Then apply a drop of the freshly mixed HXTAL onto the crack. If the crack absorbs sufficient glue it will virtually disappear and the remaining HXTAL should be wiped off the surface only with a clean cloth or paper towel. Don’t forget that the glue in the crack will still take a long time to cure so just let it sit for a week before continuing any other work on that piece.
HXTAL sets slowly, at 23°C it requires about one week to achieve most of the final bond strength, (see Physical Properties). Normally HXTAL will have set sufficiently after 24 hours to hold the two parts together as long as no stress is applied to the glue joint. This is the best time to clean up if necessary. A single edge razor blade or an X-acto knife is a good tool to scrape off the excess resin. We don’t recommend the use of solvents to clean up at this stage because solvents can migrate into the glue joint and can weaken the bond. The damage may not be evident until much later and will appear as small bubbles at the edge of the joint. After 24 hours it will be extremely difficult to remove any excess glue from the object and grinding and polishing may be the only way to remove it.
Many glass artists use HXTAL to glue pieces of various glass together to form art. Often, in the process, glued assemblies of blocks are cut or sliced with diamond saws and then more blocks are glued onto the assembly. In cases where these abrasive cuts are made across HXTAL glued joints, we recommend treating all surfaces to be bonded with an A-1100 amino silane solution. We have learned from our glass artist customers that pre-treatment with the A-1100 solution eliminates tiny micro bubbles that seem to form, often much later, in the glue line along the sawn edge.
Treatment with the A-1100 solution is simplicity itself. When the glass surfaces are totally clean and ready for gluing, simply apply the A-1100 solution over the entire surface to be glued. Apply with a lint free rag, brush, etc., and allow the Isopropyl to evaporate leaving an extremely thin film of the A-1100 coating the surface of the glass. Immediately bond with HXTAL.
While bond strengths achieved with freshly mixed HXTAL appear not to be better than mixes that have been allowed to stand around for some time more viscous HXTAL does have a number of advantages If you are gluing two very large heavy pieces of glass together, the simple weight of the two pieces is often enough to squeeze out too much
HXTAL, especially if the glue is thin. Such very THIN joints are definitely weaker than standard thickness joint lines! Avoid excess squeeze out of the glue. Using thicker HXTAL is one approach. In extreme cases, consider the use of tiny bits of glass shim at the corners, especially if these edges are to be ground or sawn off in later operations. Fragments of microscope cover glasses (available inexpensively at scientific supply companies) are ideal for use as shims.
Thicker HXTAL joint lines are also advantageous when joining materials with different coefficients of thermal expansion, such as glass to metal joints. We urge caution in making these types of joints! HXTAL adheres so strongly to glass that when these joints fail, as they often do when subjected to temperature differentials, almost always the HXTAL adheres to the glass and pulls a large, well fractured piece of glass out of the joint area!
You can improve the survival chances of these dissimilar joints by using a thick joint line - as much as 1mm thick. Fully cured HXTAL is not brittle, but rather quite tough. We believe that this lack of brittleness allows the thick joint line to better accommodate slight expansion and contraction during its lifetime.
Attempts to speed up the set of HXTAL must be approached with caution, NEVER attempt to heat freshly mixed HXTAL with an open flame, a heat lamp, a hot plate, a hair dryer or similar heating devices. Subjected to high temperatures HXTAL will begin to cure unevenly and may even ignite.
If you feel that you must heat the mixed HXTAL to speed the thickening, use only a water bath at 50°C. Heat initially for 15 minutes, remove the container and continue stirring for a few minutes. Observe the new, thicker viscosity at room temperature and decide if an additional 5 minute period is needed to reach the viscosity suitable for your specific job. Be very careful with these additional 5 minute heating periods! Once thickening has begun, it proceeds more rapidly with each subsequent heating period. Be more cautious when you mix larger batches of HXTAL as the mixture has a tendency to exothermic reaction. Keep a cold water bath handy when working with batch sizes over 100 grams.
Reduce curing time
It is also possible to reduce total curing time by placing the object in a warm (35°C) area for a 24 hour period. Be sure that your piece is properly aligned as the initial heat will thin out the HXTAL somewhat and allow pieces to move more easily. Once the piece has had 24 hours at this temperature remove it and let it cool to room temperature for 24 hours. This will successfully give you a 90% bond cure in two days. You will have a slight discolouration of the adhesive since you have increased the reaction rate, but in thinner joints, this will never be seen.
We are pleased to be able to offer you the first epoxy adhesive made specifically for conservation uses, not borrowed from another field. HXTAL NYL-1 is exceptionally clear and yellows the least upon weathering of any epoxy known to us. The primary use for
HXTAL is glass and china repair but many other uses for such a clear epoxy resin have been found. For example HXTAL makes an excellent coating resin and can be air brushed on quite nicely from ketones and aromatic solvents. This low viscosity, hard colourless glasslike epoxy resin also adheres strongly to metals wood, ivory, ceramics and marble.
Unused, mixed HXTAL can be kept for 4 to 5 days in the freezer.
It is most important that the mix container be tightly closed. The cured resin does not become brittle with time and is very resistant to yellowing and surface degradation, even after prolonged exposure outdoors. HXTAL has an initial
which remains unchanged after 1600 hours of Weather exposure rising slowly to 13 to 14 at 3,000 hours. The best competitive epoxy has an initial Yellowness of 9 which rises to over 40 after 800 hours at which point the coating begins to erode.
When pigmented with titanium oxide the resin can be made to match the finest porcelain in colour, translucency and surface appearance. With or without pigment, HXTAL NYL-1 can be used as a glaze that is highly resistant to water and most solvents.
The cured resin can be removed from hard surfaces with an epoxy remover (such as Hxtal Epoxy Solvent Attack Ref. No. 900.374) but prolonged soaking may be required to soften joints.
TENSILE STRENGTH 5400 PSI
TENSILE MODULUS 316,000 PSI
INDEX OF REFRACTION 1.515
FLEXURAL STRENGTH 10,100 PSI
FLEXURAL MODULUS 365,000 PSI
IMPACT STRENGTH 0.14 FT LBS/IN
SHORE D. HARDNESS 78
CURE OF 0.2MM FILM AT 25ºC:
SET TO TOUCH 17 HOURS
DRY TO TOUCH 30.9 HOURS
FULL CURE 14 DAYS