Soft touch coating /paint is also known as rubber coating, is ployurethane based two part industrial grade material. It’s widely used on decorative items surface finishing such as game handle, mouse, hair dryer, pen and electronic devices etc. Unlike those traditional coatings, there’re specific process of rubber coating application. Here we’ll provide detailed guides how to handle the process in professional way.
Soft touch coating properties
| Test Item | Method | Common | Advance |
| Adhesion | 1MM² Cross-Cut | 100/100 | 100/100 |
| Hardness | Mitsubishi Pencil | HB | 1H |
| Hand sweat resistance | By hand | 48 Hr no change | 96 Hr no change |
| Alcohol Test | 99.7% Alcohol wiping | ≥100 | 200 |
| Abrasion resistance | 500g press | 200S no change | 400S no change |
| Humidity resistance | 40℃*98%RH*240H | No change | No change |
| Heat resistance | (-30℃*2h~60℃*2h)*40S | No change | No change |
| Shampoo | 50% | 200S no change | 400S no change |
| ROHS | EU standards | PASS | PASS |
Rubber coating will produce sediment during storage. So after we open the drum, we need to use a clean mixer to have it properly mixed before further application. If we can’t use up one drum amount, we need to seal it properly and mix it again in next operation.
Ratio – Rubber coating must be properly mixed with thinner, or else the soft touch feel and color will vary. For instance, if the hardner is insufficient, color and drying speed will reduce, the physical strength will reduce a bit. If the hardner is over enough, the hardness will be too high and loose its soft touch feel. If thinner is insufficient, the soft feel will increase but the paint consumption will be higher which is a waste. On the other side, if we mixed with extra more thinner, the paint layer will be very thin thus loose its soft feel.
Filtering – It’s recommended to filter with 300 mesh filter.
Object surface preparation – It must be properly degreased and clean up any dust or water.
Spraying Device
Rubber coating spraying is no difference with other coatings. However we need to pay attention to the following in order to receive desired finishing:
Spray gun FAN size should be set smaller so the object can get coated well, single surface should be sprayed 2-3 times.
- spray gun nozzle: we recommend 1.2mm diameter
- air pressure: 2.5-4.0kg/CM²
After spraying, there will be 5-10 minutes stay which we call it leveling. During this period, the paint will flow on the surface till it’s flat with matt color.
The most important part is the paint spraying skills. Because it’s easy to get color difference by manual spray, we highly recommend automatic spray machine for even and stable quality control.
Curing Device
It’s the best to stay in sealed oven chamber device which will provide a stable and accurate temperature environment. Stable temperature is crucial for rubber coating curing process. If we set for mass production by conveyorised oven, the temperature controller must be well set to work with a proper temperature. Following is a table list of rubber coating curing conditions under different temperatures:
- 80℃ – 25 Min
- 70℃ – 30 Min
- 65℃ – 35~40 Min
- 50℃ – 45~50 Min
If we let it natural drying in room temperature, 24 hours will be required. After curing, there will be 0.5~3 hours cooling required before packing.
Inspection Method
1- glossiness
Normally by eye observation which is direct judgement by required finishing
2- Anti scratch
use an eraser with 500g strength to scratch by 3cm speed, note down the times.
use QHQ-A pencil to scratch 3 times on different areas then erase the mark via eraser. See if there’s break (H class pencil with 500g strength by 45°angle)
3- Adhesion
By cross-cut method using 3M sticker. It’s passed if there’s no drop.
4- Chemical resistance
Chemical agent like alcohol/shampoo/washing powder/salt water/NaOH etc
Method: use a cotton cloth to we with 99.7% alcohol then wipe with 500g strength, note down the times(same way for other chemicals)
