Application
Numerous OH-terminated polyester and acrylics can be used to achieve weather-resistant decorative powder coatings with excellent physical properties. These polyols have a determining influence on the performance of the coating.
Formulations
Crosslinker and polyester are used in equivalent amounts. Empirically determined“under indexing” (up toNCO:OH =0.8:1)yields economical coatinas which exhibit excellent physical properties meeting the required performance profile.
| Specification | |||
| Property | Value | Unit | Test method |
| NCO content(latent) | 15.2-17.0 | % wt | according to DIN EN ISO 11 909 |
| NCO content (free) | <1 | % wt | DIN EN ISO 11 909 |
| Glass transition temperature | 78-90 | ℃ | DSC |
| Colour index | <600 | Hazen | DIN EN ISO 6271 |
| Typical properties | |||
| NcO-equivalent | ~275 | g/Eq | - |
| Density | 1.07 | g/cm3 | DIN EN ISO 1183 |
| Bulk density | ~570 | kg/m3 | DIN EN ISO 60 |
| Melting range | 90-112 | ℃ | DIN EN ISO 3146 |
| Flashpoint | >150 | ℃ | DIN EN ISO 2592 |
| Ignition temperature | 450 | ℃ | DIN 51 794 |
| Examples of formulation for binder combinations | |||
| Crosslinking ratio(NCO:OH) | 1:1 | 0.8:1 | |
| VESTAGONBF 1540 | 13 20 | 11 17 | parts |
| Polyol (OH number 30) | 87 - | 89 - | parts |
| Polyol (OH number 50) | - 80 | - 83 | parts |
Up to 1 % by weight degasser is often used in pigmented powder coatings to minimize surface imperfections.
The use of a catalyst to accelerate the formation of urethane bonds is recommended.Dibutyltindilaurate (DBTL) has been proven to be a useful accelerator. The maximum suggested use level is 0.15 % by weight based on the total formulation.
Curing
The curing temperature for PUR powder coatings based on VESTAGON®BF 1540 lies above the splitting temperature of about 160 C. A prerequisite for good physical properties of a coating is sufficient curing in the range of 170℃,25 minutes up to 210°C,8 minutes total oven time, according to the following standard procedures.
Premixing: MTI-Mixer 2'-500 rpm
Extrusion: W&P ZSK 30 90°C-250 rpm
Application: Manual spray gun 80 kV;steel panels 0.8 mm
Curing: Air-circulated Heraeus oven;coating thickness 55-75 um
Special Notice
The extrusion temperature must be selected to ensure that a mass temperature of minimum 130 ℃ is maintained. Otherwise, inadequate dispersion may result in reduced gloss and mechanical properties of the coatings.
Applications for Polyurethane Powder Coatings
PUR powder coatings have been successfully used for many years in both exterior and interior applications such as:
· motor vehicle parts
· fittings
· bicycle frames
· fork lift trucks
· exterior furniture and lawn equipment
· agricultural machinery
· appliances
· telephone booths
Storage and Packaging
The product is delivered in flat bags, net weight 20 kg. If kept cool (0 - 40°C) and dry in closed bags the product can be stored for at least 1 year in accordance to the specification. All opened bags should be carefully resealed immediately after use.
Safety and Handling
Please refer to our Safety Data Sheet.
