Fluorine-containing HDI trimers prepare water-based polyurethanes that are wet and water resistant

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Studies have shown that fluorocarbon chains have low surface free energy and can be combined with PU through fluorine-containing polyether glycols or chain extenders.
For the former, the fluorine fragments are usually fixed on the main chain of the macromolecules, resulting in surface enrichment of fluorine.
Regarding the latter, Jiang et al.

synthesized a fluorinated waterborne polyurethane (FPU) using 2,2,2-trifluoroethanol as a chain extender, but they found that the water contact angle of the solid film was about 90°, which could not be further improved.
Improvement.

So far, due to the lack of fluorinated isocyanates and fluorinated diols with longer fluoroalkyl chains, the preparation and application of WPUs with controllable surface tension and excellent water/solvent resistance have progressed slowly.
In response to these problems, Jiating Wen from the Key Laboratory of Leather Chemistry and Engineering of the Ministry of Education of Sichuan University used fluoroalcohol (TFO) and HDI trimer (HDIT) to prepare fluorinated isocyanate (F-HDIT).

The series of fluorinated waterborne polyurethanes (FWPU) provide a new way for the development of new fluorinated diisocyanates and the preparation of multiple functional polyurethanes with controllable surface tension and high water resistance.

research content

1.
Synthesis of F-HDIT

The synthetic route of F-HDIT is shown in Scheme 1.
The mixture of HDIT and butyl acetate (weight ratio 1:1) was added to a four-necked flask equipped with a magnetic stirrer, a thermometer, a dropping funnel and a nitrogen conduit.
In the mixture of TFO and butyl acetate (weight ratio 1:1), add 0.

1% bismuth neodecanoate, drop it into a four-necked flask with a constant pressure funnel for 0.
5h.

2.
Preparation of FWPU

The synthesis process of FWPU emulsion is shown in Scheme 2.
Pour F-HDIT, IPDI, PPG210, PTMG220 and BDO into a three-necked flask equipped with a mechanical stirrer, thermometer and nitrogen inlet.

F-HDIT accounts for 5%-20% of the total diisocyanate (calculated by molecular ratio).

Results discussion

1.
Characterization of F-HDIT

2.
The influence of fluorine group on the thermal stability of FWPU coating film:

3.
Dynamic mechanical analysis of FWPU coating film:

4.
The influence of fluorine group on the mechanical properties of FWPU coating film:

5.
The relationship between fluorine content and particle size:

6.
The wetting and spreading ability of FWPU on low surface energy substrates:

7.
Water and solvent resistance of FWPU coating film:

8.
Water and solvent resistance of FWPU coating film:

in conclusion:

In summary, a series of FWPU based on fluorine-containing isocyanate trimer (F-HDIT) has been successfully synthesized.
Compared with the control sample FWPU-0, the surface tension of FWPU emulsion is reduced, and the wetting ability of the coating film is improved.
At the same time, the contact angle of water and diiodomethane increased with the increase of F-HDIT content and film surface roughness, and the highest reached 121.

8° and 90.
7°, respectively.

Reference materials: 

WenJ, Sun Z, Fan H, et al.
Synthesis and characterization of a novel fluorinatedwaterborne polyurethane[J].

Progress in Organic Coatings, 2019,131:291-300.

The author's opinion:

1.
There are more and more applications of waterborne polyurethane, but there are defects such as high surface tension, poor wettability, and poor spreading ability.

The introduction of trimers or fluorine-containing compounds in the synthesis can improve these problems and promote the popularization and application of products.

2.

3.