2. 2
Hydrogen is the smallest stable atom we know, combined
with oxygen , we get water where there are two hydrogen
atoms and a small imbalance in charge , that causes a
hydrogen bond as shown in the diagram .
This is great for us, as the hydrogen bonding in water
makes it a liquid and without water we would not exist on
this planet Earth. The hydrogen bonds are not permanent,
like the covalent bond between the hydrogen and oxygen
molecule, so the bond forms liquids with a known viscosity
at certain temperatures . The bond can be broken and
reformed.
Hydrogen bonding also occurs between many other
molecules , and we show for example the hydrogen
bonding in methanol , which is a very useful small
molecule for us as we will show below. Without the
hydrogen bonding , methanol would be a gas at room
temperature. Hydrogen bonding also occurs in mixtures of
Chemicals and Polymers.
Here we will address the hydrogen bonding that develops
in some polymers, Particularly Polyurethanes and the
newly developed silane terminated polyurethanes. The
hydrogen bonding is very useful and gives Polyurethanes
some excellent physical properties when the adhesives or
sealants are cured.
INTRODUCTION
Water hydrogen bond
Methanol hydrogen bonds
Polyurethane Polymers are very good chemical products that Chemical Engineers invented many
years ago, Otto Bayer was the inventor and Father of the large Bayer Polyurethanes Company.
These polyurethane polymers are used to make many articles that include Paints, adhesives,
sealants ,hard and soft rubber foams and other products . However they have several issues and
are not always the best product to use considering Consumer Health.
3. 3
1. Polyurethanes use long chains of non toxic
polypropylene glycols and Isocyanate monomers
with NCO groups to build chains, where there are
some unreacted NCO groups left, and these are
toxic to people and carcinogenic in small quantities.
The unreacted NCO groups in SPUR resins have
been reacted with methoxy and ethoxy containing
silane molecules and these are very much less toxic
products. Good we have solved this problem, and
the new polymers are called HYBRID technology
polymers. They use the best features of
polyurethanes and also silicone polymers.
Two main Problems with Polyurethanes
2. The second problem is also important , the
hydrogen bonding of urethane and urea groups
causes these resins to be very thick ,as in the
common chemistry a hydrogen atom attached to a
nitrogen atom on one chain has a weak attachment
to an oxygen atom on another Chain. Thus the
polymer chains are not able to slip easily over each
other. We get thick resins like honey consistency.
silane terminated polyether molecules
STP POLYMER
There are two problems that are very significant in
Industries using these Polyurethane polymers.
Hydrogen bonding
4. Solutions
A common solution to the thick polyurethane resins has been to add solvents, and in particular the
solvent Xylene has been found to reduce viscosity at about 10 percent addition level. However we
are now in a stage where such solvents need to be eliminated, as xylene is harmful and is a big
problem to human health where there are some emissions of xylene. It has also been the practice
in PU resins to leave some unreacted NCO containing monomer , as It also helps reduce
prepolymer viscosity. The combination of xylene and some unreacted NCO monomer like TDI is
considered a serious toxicity issue in PU construction sealants.
THE SOLUTIONS
We have fixed the problem of Isocyanate toxicity by
manufacturing trimethoxy , dimethoxy and triethoxy silane
terminated polyether and polyurethane chains that are now
called Hybrid polymers.
We now fix the high viscosity of these polymers by blocking
the hydrogen bonding with some cleaver molecular
engineering.
By adding a small amount of about 0.5 percent of methanol
shown above, hydrogen bonding between chains are
blocked by the methanol hydrogen bonding to the polymer
chain so each polymer chain is able to slip relative to the
other chains, a little bit like cooked spaghetti where you
have added some oil or butter to make the spaghetti slip
better. The methanol can be removed in processing so the
polymer has good creep resistance when finally cross
linked. The methanol also reacts with any free NCO groups
so we can claim NCO free resins or polymers.
The solution is very simple and not complicated , and makes it easier for Factory workers to use
STP and SPUR Polymers to make sealants and adhesives. We show a picture below of the clear
sealants made with our STP resins .We do also have a patent on this simple Technology in
Australia .
Spaghetti
Clear STP sealant
