Flame retardation of cellulose nanofiber

The following is a discussion of the coating type flame retardant using cellulose nanofiber (CNF).

Base material: Polypropylene plate (PP plate) ignition point 300-400 ℃, melting point 160 ℃
Size: 200mm * 140mm * 1mm

CNF Water content 94.58

50 g of a 2 wt% CNF aqueous solution was generated, and about 13 g of bestboron was mixed to prepare a coating type flame retardant.
Although the color is white, it becomes a transparent coating film when completed. It has sufficient viscosity for coating operation.

This is applied by the following method.

However, since the wettability of the PP plate was low, the surface was modified by plasma treatment.

After coating, dry in a dry oven for 24 hours. The temperature was set at 75 ° C.

The photograph of the PP board after drying is shown.

The flame retardancy was evaluated using the 45 ° C combustion test method. This is a combustion test method in accordance with JIS L1091, in which a flame is applied for 5 minutes to evaluate the back surface temperature and the presence or absence of penetration.
The tester used was as follows.

The test results are shown below.

A fire layer was formed at the same time as the flame hit the surface of the PP plate, and the two layers of the carbonized layer formed afterwards could withstand a 5-minute combustion test by blocking the flame.

In a test conducted at the same time, starch was used instead of CNF. Here’s a similar effect, but with a different look.

The mechanism of flame retardance is shown below.


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