High solids and nonsolvent systems emit fewer VOCs and maintain performance

In addition to reduced VOC emissions, high solids systems can be processed using the same production equipment as traditional systems with minor adjustments, saving formulators time and money. Low-viscosity Desmodur® polyisocyanates are used as crosslinkers for suitable polyols in a variety of high solids coating systems. The latest generation of Desmodur® polyisocyanate crosslinkers, which has been optimized for numerous applications, makes it possible to significantly reduce the VOC content of coatings systems while maintaining their properties. High solids and even systems without solvents can be formulated with Desmophen® NH polyaspartic esters in combination with low-viscosity polyisocyanate crosslinkers.

Today, two-component (2K) polyurethane (PU) systems based on aliphatic polyisocyanates are the standard choice for automotive OEM, car refinish, plastics, furniture, commercial vehicle and general industrial high-quality coating applications. Low-viscosity aliphatic, hydrophobic polyisocyanates are suitable for formulating high-solid coating systems that meet environmental demands. Low-viscosity crosslinkers are defined as having a viscosity below approximately 1500mPas. The quality of a final coating with low VOC emissions is largely dependent on the functionality and viscosity of the polyisocyanate. We offer the Desmodur® product line of low-viscosity polyisocyanates with different chemical structures for achieving VOC-compliant systems. Chemical structures in our Desmodur® crosslinkers based on hexamethylene diisocyanate (HDI) include low-viscosity isocyanurate, allophanates, asymmetric trimer and uretdiones. The ability to achieve low viscosity while maintaining functionality leads to a better property balance in the final coating formulation. 

The selection of a specific grade of our Desmodur® polyisocyanate crosslinkers influences the final properties of high solids coatings. Once the required properties have been defined, it is possible to choose the most suitable grade of polyisocyanate. Coatings prepared with Desmodur® low-viscosity polyisocyanates are formulated to achieve the desired performance characteristics, such as chemical resistance, abrasion resistance, weather resistance, gloss retention, and resistance to yellowing and chalking.

Reducing solvent emissions is a constant challenge in the development of environmentally friendly coating systems. The low viscosity of polyaspartic binders makes it possible to formulate systems for ultra-high-solids and even near-zero VOC coatings. Our Desmodur® co-reactants enhance the performance level of these coatings. Polyaspartics represent a class of binders that combine low to zero VOC content with high productivity, while maintaining the flexibility, durability and chemical resistance that users expect from polyurethane coatings. The chemistry of polyaspartic coatings is based on the reaction of an aliphatic polyisocyanate with a polyaspartic ester to create an aliphatic polyurea. However, coatings based on polyaspartics differ greatly from conventional polyureas, which are based on aromatic polyisocyanates, in their application and performance properties. The property profiles of polyaspartics can be influenced by the selection of the polyisocyanate curing agent. Fine-tuning of the pot life and reactivity of the formulation can achieved with the appropriate Desmophen® NH co-reactant.In terms of performance, the primary attribute of a polyaspartic is its high reactivity, which enables increased job site productivity thanks to reduced drying times. 

Some additional benefits of polyaspartics include: 
• Greater film thickness 
• Low color value 
• Good weatherability 

Even with their ultra-high-solids content, polyaspartic coatings can still be easily applied with conventional coating equipment used in many applications. Polyaspartic technology is primarily used in anti-corrosion coatings, as coatings for commercial vehicles, agricultural and construction equipment, wind power stations and the construction industry. Due to its rapid curing characteristics, even at ambient temperatures, this technology is also highly attractive for the automotive refinish coatings market.