Discussion on the Influence of Different Loose Agents on the Performance of Powder Coatings

In the production and use of powder coatings, it is often encountered due to the poor fluidity and storage stability of the powder coatings, which results in poor fluidization during powder coating, which is prone to spitting or even agglomeration of powder coatings.
A series of problems affect the quality of coating products
.

Generally, as the temperature rises, especially in the hot summer, the frequency of such problems increases significantly

1 Test part

1.
1 Test materials

The test powder coating used outdoor powder coating products produced by Shandong Qianjiang Powder Technology Co.
, Ltd.
, and the loosening additives used products provided by different manufacturers
.

1.
2 Test method

1) The influence of different types of loosening agents on the flow index R of powder coatings

Choose commonly used outdoor powder coating products, add different types of loosener products at 0.
05%, 0.
1%, 0.
2%, 0.
4% addition amount, mix well and pass through a screen to determine the flow index R of the powder coating
.

2) The effect of different loosening agents on the flow index R of different powder coatings

Choose 7 kinds of commonly used outdoor powder coating products, add loosening additives according to the addition amount of 0%, 0, 2%, 0.
4% respectively, and then measure the flow index R of the powder coating after mixing the base powder and the loosening agent evenly
.

3) The effect of different loosening agents on the powder coating rate of electrostatic spraying of powder coatings

Test method: select the test board specification: 18Cm*25Cm, use the same board for repeated spraying, directly weigh the mass of the board and the adsorbed powder after spraying, and subtract the mass of the blank board to obtain the mass of the adsorbed powder for each sprayed board
.

The amount of powder used for each spraying is 13g, a sample is measured 5 times, the maximum value and the minimum value are used as the rejection data, and the average value of the other three sets of data is the powder quality of the sample powder
.

The formula for calculating the popularity rate is as follows:

4) The influence of different loosening agents on the appearance of different coatings

Choose common outdoor powder coating products by adding different loosener products in the same amount, mix them evenly and pass through a sieve.
After the sieved powder, use the same process to spray 5 samples with different film thicknesses, and measure the film thickness after fully curing.
Film thickness and gloss
.

Observe the leveling and sand particles on the surface of the coating film and compare with the base powder sample plate without loosening agent
.

5) The influence of different loosening agents on the appearance of the coating film in different adding processes

Choose the same loosening agent in the common outdoor powder coating products according to the same addition amount, choose different addition methods to add to the powder coating, and compare the appearance of the coating film after spraying the sample powder from different addition methods
.

6) The influence of different loosening agents on the stability of powder flow index R after storage

After selecting the same outdoor powder coating and adding different loosening agents in the same way to prepare sample powder, the flow index R of the powder coating is measured, and the flow index is tested and recorded at regular intervals
.

7) Influence of loosening agent on different powder coating varieties

Choose different types of outdoor powder coatings (sand grain, flat, matte, bright), and add the same loosening agent in the same way to prepare powder spraying samples
.
Compare the appearance of the coating film after spraying the sample powder with the sample powder before and after the loosening agent is added
.

2 Test results and discussion

2.
1 The influence of different loosening agent varieties and dosages on powder flow index R

Using test method 1), 4 kinds of loosening agent varieties and different addition amounts were tested.
The tested powder flow index R results are shown in Table 1
.

The test results from Table 1 show that:

① Adding a certain amount of loosening agent to the powder coating system can significantly improve the flow index R of the powder coating.
With the increase of the amount of loosening agent, the flow index R of the powder increases significantly
.

②The improvement effect of the powder flow index R value between different loosening agents is quite different.
When loosening agent D is added 0.
4%, the effect of powder flow index R reaching 177 is the best, and loosening agent A is only 125 the worst
.

③ Loose agent B, loose agent C and loose agent D can meet the requirements of general powder coatings by adding only 0.
2%
.
Good and bad effects of the following order of relaxer: relaxer D> relaxer C> relaxer B> A relaxer
.

2.
2 The influence of the added amount of loosening agent on the flow index R of different powder coatings

Using test method 2), loosening agent D and 7 powder coatings (including sand texture, flat gloss, low gloss, high gloss, etc.
) were selected for testing.
The test results are shown in Table 2 below
.

The test results from Table 2 show that:

①For different types of powder coatings, the flow index R value of the powder coatings has been significantly improved after the loosening agent is added, and the flow index R of the powder has a corresponding increase with the increase in the amount of loosening agent
.

②The same loosening agent has different influences on the powder flow index R of different powder coatings.
For example, when 0.
4% is added, the high is 173 and the low is 133.
For different products, different amounts of loosening agent should be added.
In order to meet the requirements of powder fluidity
.

2.
3 The effect of different loosening agents on the powder uptake rate

Choose 4 kinds of loosening agents, using test method 3), 5 kinds of different dosages, test the powder coating sample powder 8#, the test results of different loosening agents on powder electrostatic spraying powder rate are shown in Table 3
.

① Loose agent A: As loose in the range of the old% of the addition amount, but when the addition amount is greater than 0.
1%, the powdering rate decreases with the increase of the loose agent
.

② Loose agent B: With the increase of loose agent within the range of 0.
05%, the powdering rate will increase
.
But when the addition amount is greater than 0.
05%, the powdering rate decreases with the increase of the loosening agent
.

③ Loose agent C: With the increase of loose agent in the range of 0.
1%, the powdering rate increases
.
But when the addition amount is greater than 0.
1%, the powdering rate decreases slightly with the increase of the loosening agent
.

④ Loose agent D: With the increase of loose agent in the range of 0.
1%, the powdering rate increases
.
But when the addition amount is greater than 0.
1%, the powdering rate decreases slightly with the increase of the loosening agent
.

The above experiments show that adding a small amount of loosening agent to powder coatings can help increase the powdering rate of powder coatings, but when the amount of addition exceeds a certain amount, the powdering rate of some varieties tends to decrease
.

It shows that different kinds of loosening agents have different effects on the powdering rate
.
The loosening agents C and D have less negative influence on the powdering rate when the added amount is large
.

2.
4 The influence of different loosening agents on the appearance of different coatings

Using test method 4), the experiment was conducted on the combination of 4 loosening agents and sample powder 9# (verified powder number)
.
The test results of the influence of different loosening agents on the appearance of the coating film are shown in Table 4 .

The test in Table 4 shows that: different loosening agents added to the powder coating have a very different effect on the appearance of the powder coating.
The effect of loosening agent C and loosening agent D is very good, and the effect of loosening agent A and loosening agent B is poor
.

This is because the quality of loosening agents varies greatly.
Some loosening agents have poor dispersibility.
After being added to powder coatings, the agglomeration of loosening agents causes sand particles in the coating film
.
The looser with better quality has little or no effect on the surface of the coating film after being added to the powder coating
.

2.
5 The influence of different loosening agents on the appearance of the coating film in different adding processes

Using the method of test 5), the test results of the effect of different addition methods on the appearance of the coating film are shown in Table 5 below
.

The test results in Table 5 show that the influence of the loosening agent added to the powder coating on the appearance of the coating film is not only related to the type of powder coating, but also has a great relationship with the way of adding
.

There is no obvious difference between the coating film and the control group (without the loosening agent) after adding the loosening agent according to method one
.
However, adding loosening agent according to method two will cause the surface of the coating film to have poor leveling and sand particles
.
Therefore, choosing the appropriate loosening agent addition method has a very important influence on the appearance of the powder coating
.

2.
6 The influence of different loosening agents on the flow index R of the powder after storage

Using test method 6), for 4 different loosening agents, the addition amount in the powder coating is 0.
2%.
After storing for different periods of time, the powder flow index R is tested.
The test results are as follows in Table 6 below
.

The test results from Table 6 show that:

①The flow index of the powder without loosening agent can meet the standard requirements in a short time, but when the storage time is a little longer, the flow index R of the powder coating can only reach 105, indicating that the storage stability of the powder is poor
.

②The loosening agent A does not significantly improve the flow index R of the powder coating in a short time, but it improves the storage stability of the powder coating greatly.
When the powder coating is stored for a long time, the flow index R of the powder coating does not decrease significantly
.

③The loosening agents C and D significantly improve the flow index R of powder coatings, and the flow index R of powder coatings does not change much as the storage time of powder coatings increases, indicating that these two loosening agents have better effects on improving the index R of powder coatings
.

The experimental results show that adding loosening agents to powder coatings can significantly improve the flow index R of powder coatings, but different loosening agents have very different effects on improving the flow index R of powder coatings
.

2.
7 The influence of loosening agent on different powder coating varieties

Using test method 7), the addition amount of loosening agent A in different types of powder coatings is 0.
2%
.
The experimental records after preparing the sample powder spraying sample board are shown in Table 7
.

The test results from Table 7 show that:

① The loosening agent has different effects on the flow index R of different types of powder coatings.
When the amount of loosening agent is increased, the flow index R of the powder will increase significantly
.
Adjust the appropriate dosage according to the type of coating .

②The loosening agent has no obvious adverse effect on the appearance and gloss of the coating film
.

3 Conclusion

From the above-mentioned different loosening agents, different addition amounts, the test results of different powder coatings and different addition methods show that: in order to improve the fluidity of powder coatings, loosening agents are a component that must be added in the formulation;

Different loosening agents and different dosages have different effects on the fluidity and powdering rate of powder coatings.
Therefore, the appropriate loosening agent varieties and dosages must be selected according to the types of powder coatings;

The addition process (method) of the loosening agent has a great influence on the appearance of the coating film.
Choose the appropriate adding process (method) according to the variety of the loosening agent
.

Source: Wen/Long Haibo, Yang Jun, South China Shandong Qianjiang Powder Technology Co.
, Ltd.