Initial tack, long lasting adhesion
Tack is a valuable property when assembling as it helps maintain the parts together and keep them in position. But an assembly can only be validated if there is durable adhesion over time.
Luvitec® PVP is a transparent compound which does not alter in colour with time. As such, Luvitec® products will not affect the colour stability, nor the product's aesthetics.
From a technical point of view, Luvitec® PVP does not evolve in colour as it does not absorb the light and UV as the spectrum is totally flat. Therefore formulations containing Luvitec® will not be affected in colour over time.
Luvitec® PVP does not present any hazard if absorbed or inhaled. It has been used for many years in pharmaceutical applications. It is also component of products being used by children. More specifically Luvitec® grades present the following features: Very low acute oral toxicity, non-irritating to the skin as well as to the eye.
Chemical, biological inertness
Luvitec® products are chemically and biologically inert. They are very stable in a wide temperature and pH range which is due to the polyethylene polymer backbone. There is no hazard risk in case of body contact. PVP has been used for many years in cosmetics and hair care applications. Luvitec® PVP provides the following features: Non-sensitizing, no evidence of mutagenic potential and non-toxic to aquatic organisms.
Compatibility with many media
One of the outstanding properties of Luvitec® PVP is its universal solubility both in hydrophobic and in extremely hydrophilic solvents. Luvitec® products are soluble in water and polar solvents:
- In solutions, excellent wetting properties and film forming
- In powder, absorbs up to 18% of its weight of atmospheric water
With higher molecular weight PVP and when producing concentrated solutions, the rate of dissolving can be significantly increased by raising the temperature to 50-60° C. This universal solubility makes it good as a coating or as an additive to coatings at it can be blended with many polymers, in particular with polyacrylics.
Luvitec® PVP can react with the matrix according to a physical interaction with hydrogen dipolar links. Therefore, it won't migrate and crosslinability has a positive impact on tack duration and quality which is a very important aspect in terms of process reliability and manufacturing.
Moreover, when crosslinked, Luvitec® PVP is capable of swelling in polar solvent such as water. On account of its outstanding adhesion and physiological compatibility, such weakly crosslinked PVP with high water content forms hydrogel and is employed as a skin-adhesive gel.
Luvitec® PVP exhibits strictly Newtonian behaviour and will therefore not affect the rheology of the base formulation.
The rise in viscosity with increasing concentration depends essentially on the molecular weight or K value. While in the case of low molecular weight, such as the Luvitec® K30 grade, an increase in concentration for example from 5% to 10% has only a slight effect on the viscosity, changes by a factor of 5 or more can be found for a high molecular weight Luvitec® K90 type.