EXOTHANE Elastomers Conversion, Shrinkage Data - Sponsored Whitepaper

Previous testing revealed that the new EXOTHANE ™ Elastomers demonstrated superior mechanical properties in regards to toughness, hardness, color, tensile strength and percent elongation. Now, additional testing has confirmed that these materials also have low percent volumetric shrinkage, low shrinkage stress and high conversion.

As in the previous studies, the following data was collected by testing our pure EXOTHANE Elastomers alongside the standards, Urethane Dimethacrylate (UDMA) and a 70:30 wt% blend of bisphenol A glycidyl methacrylate and triethylene glycol dimethacrylate (BisGMA:TEGDMA Blend). Each material was formulated with 3% (w/w) Esacure KTO46 as a photoinitiator package. The data that follows focuses on Exothane 8, 9, 26 and 32. Identical testing on Exothane 10 and 32 is pending.

Volumetric shrinkage was measured using a linometer (ACTA). A constant volume of each material was sandwiched between an aluminum disc and a glass cover through which, the curing light irradiated the resin. A mercury arc lamp (Acticure 4000) at an incident irradiance of 20 mW/cm2 was used to irradiate the materials. Degree of conversion and dynamic volumetric shrinkage were monitored simultaneously.

Volumetric shrinkage values were unobtainable using this process for the UDMA and BisGMA:TEGDMA Blend specimens as each shrunk enough to detach themselves from the glass cover before data could be collected. Separate specimens, half the thickness of the Exothanes specimens, were tested to obtain comparison data. The percent volumetric shrinkage for the UDMA and BisGMA:TEGDMA Blend specimens were 5.8% and 7.1% respectively.

The EXOTHANE Elastomers displayed lower percent volumetric shrinkage while maintaining high conversion values (Figure 1). This is the most ideal scenario for applications requiring low shrinkage and low residual monomers after polymerization. This is also ideal for coating formulations where pull-back and curling are encountered.