A Naturally Low Gloss Dispersion for Polyamide Polyurethane Coatings

Posted by Lubrizol Performance Coatings Team on 12/12/2018

Matte finishes are popular in any number of applications for their dull, low-gloss, and natural look that is achieved with most of the light diffusing in a range of angles.

To achieve a matte finish, the requirement to include a significant amount of additives for low gloss properties comes with its own inherent challenges—like susceptibility to scratches and chemical exposures. That means the typical matte finish in products like auto interiors, wood coatings, industrial metal and more won’t stand up well to everyday use.

Matting additives in low gloss coatings typically consist of segmented polymers that include segments of soft and hard blocks. The physical and mechanical properties of these additives are dependent on segment properties and intermolecular interactions. An example of segmented polymers is TPU and water-borne polyurethane dispersion, with chemical and physical properties strongly influenced by the soft segment. Common soft segments in polyurethane dispersions (PUDs) are made of polyester, polyether, or polycarbonate polyols.

Polyamide polyol technology has long been thought to be unsuitable for use as a soft segment in PUDs. There have been many reports on attempts to make polyamide-urethane polymers, but with little commercial success for many reasons. They have a tendency to form crystalline, high melting structures due to strong intermolecular hydrogen bonding. Their viscosity is usually too high to handle in common PUD processes and an additional synthesis step is needed to convert amine or carboxyl chain-ends to hydroxyl.

The polyamide-urethane polymers that have hit the market use large particle sizes suspended in small particle sizes to make a low gloss surface. The problem is they aren’t stable, leading to a very short shelf life because the large particles fall out of solution.

Overcoming Polyamide Polyol Challenges

Lubrizol has overcome these traditional polyamide polyol challenges with water-borne polyurethane/urea dispersions made of telechelic polyamides. A series of telechelic polyamides were developed with amine or hydroxyl terminations and a controlled level of:

  • Molecular weight
  • Hydrophobicity
  • Hydrogen bonding
  • Branching/rings

The result was a self-matting water-borne amide urethane with reduced gloss generated by protruding surface features. This new type of resin offers the possibility for matte finish without the use of a matting agent.

As the resin progresses over a span of 35 minutes, the protruding surface features show and generate the surface features. Without a matting agent, the resin can achieve a gloss of 13-18 on the 60° angle and 25-40 on the 85° angle while offering exceptional clarity, hardness, toughness, and chemical resistance.

Lubrizol recently brought a new, proprietary polyamide technology to market as Aptalon™ W8030. This resin is a water-borne, self-crosslinking polyurethane dispersion that provides matting to coating systems without the need for additional matting additives.

Aptalon W8030 can be used as the primary resin in a water-borne coating, or can be blended into standard PUD or acrylic systems to provide the desired level of matting with a corresponding increase in film properties. Gloss units of 13-18 can be further reduced with the addition of select matting additives at significantly lower levels than normally needed to achieve a similar gloss level.

This polyamide technology has proven to work well in a number of challenging applications, like fiberglass doors, textured finishes on autos, faux leather effects, brushed stainless accents, and wood floors with a low gloss finish. But, the possibilities for its unique capabilities go well beyond these applications.

Aptalon W8030 is just the latest in the Aptalon family of resins, which already includes Aptalon™ W8060 for high gloss clear systems, and Aptalon™ M8100 for gloss or matt pigmented metal topcoat systems.

View more information about Aptalon W8030 or contact your local Lubrizol account manager to learn more about matting for coating systems without the need for additional matting additives.

Lubrizol Performance Coatings Team

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