Tri-iso distributes a wide range of polycaprolactone polyols that allow formulators to produce high quality polyurethane adhesives. Polyols contain reactive hydroxyl (OH) groups which react with isocyanate (NCO) groups on isocyanates to form polyurethane adhesives.
Polycaprolactones are a special high performance class of polyester polyols. From a chemical structure point of view, polycaprolactone polyols are hexane glycol adipates. The method by which polycaprolactone polyols are produced compared to standard glycol adipates determines their enhanced physical properties. Polycaprolactone polyols are formed by a ring opening of a heterocycle ring (caprolactone monomer) by a glycol initiator. The nature of this reaction results in a low polydispersity (narrow molecular weight distribution). The lack of the high molecular weight tail found in standard polyester polyols results in the lower viscosities found in polycaprolactone polyols. Moreover, the lack of the low molecular weight tail results in better low and high temperature performance. Additionally, polycaprolactone polyols exhibit enhanced hydrolytic stability compared to standard glycol adipates because they are made under mild conditons and without acid catalysis.
Additionally, since polycaprolactones are polyester polyols, they also produce polyurethane adhesives with enhanced UV resistance, excellent resistance to oils and fuels, and better abrasion resistance and tensile and tear strength compared to polyether-based polyurethane adhesives.
There are several key characteristics which define what performance properties a given polycaprolactone polyol will impart in a given polyurethane adhesive. These characteristics include: the hydroxyl number or hydroxyl value (OH value), OH equivalent weight, molecular weight, and the functionality of the polyol.
Hydroxyl number (OH ) is the measure of the hydroxyl group content of gram of polyol. Hydroxyl value is measured by titrating a known mass of polyol against potassium hydroxide (KOH), and is expressed as mg KOH/g. Lower hydroxyl values indicates lower hydroxyl content and a higher molecular weight for the overall polyol.
OH equivalent weight is the number of grams of a given product that contains one equivalent of hydroxyl groups (NCO). Equivalent weight = 56100/OH
Molecular Weight is determined by multiplying the equivalent weight by the polyol functionality
Polyol functionality refers to the number of OH groups per molecule. Increasing the number of OH groups results in greater crosslinking. Greater crosslinking yields stiffer, harder products with enhanced chemical and thermal resistance. Polyols that contain 2 hydroxyl groups are called diols, polyols with 3 functional groups are called triols, polyol groups with 4 hydroxyl groups are called tetrols.
Your Tri-iso Technical Sales Representative is available to assist you in the selection of the appropriate polycaprolactone polyol that will provide the specific properties you are trying to obtain. Click here to request a quote.