It would be best if the plastic and CNF had a flame retardant that was highly effective at the same time.
However, many plastic flame retardants have a high environmental impact and do not want to use them much. In that case, it is necessary to impart flame retardancy to the CNF with a unique flame retardant.

The effective flame retardant for cellulose is boric acid or phosphoric acid. Many of the flame retardants used in the manufacture of non-combustible wood are boric acid or phosphoric acid or a mixture thereof. Curiously, there is little interaction with the chemical industry regarding flame retardant technology for non-combustible wood, and non-combustible wood is being researched independently by each company.
In addition, since few companies sell only drugs, the details of these flame retardants are not well understood.

However, these flame retardants are not perfect, and there are various issues regarding flame retardancy of wood.

Generally, boric acid is said to be effective. Phosphoric acid also appears to be effective, but is not preferred because it can cause leaching problems and adversely affect the material.
However, there is almost no flame retardant made of boric acid alone, so demand is concentrated on some products.

We also do a little testing.
The results are good so far.
However, we have not yet constructed data that can be displayed on the table.
Do you mix with powder? Mix with aqueous solution? And so on.

As a flame retardant that is highly effective for cellulose, couldn’t it be expected to be effective for cellulose nanofibers?

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①Lightweight and 5 times stronger than iron
② Less deformation due to heat
③ Low environmental load due to plant origin
④ Abundant resources

Is this around here? Some products have actually been commercialized, and it appears that the joint research between Chuetsu Pulp and Paper Industry and Idemitsu Lion Composite has begun production of high-strength resin into which cellulose nanofibers are kneaded.

Isn’t cost a challenge?

Since it is not yet in mass production, it is expected that the price will be over 3,000 yen to 5,000 yen / kg in gel form.
Also, it is difficult to knead with resin because it is a gel, and its concentration is about 2 to 10%, so it seems that it is difficult to get on the experimental table for development.
It seems that powder type cellulose nanofiber has been developed to increase the concentration of CNF, but the price is tens of thousands of yen / kg.

Raw materials are abundant materials, so the price will drop sharply when entering mass production. Because it is an important technology in Japan, we want to somehow commercialize it before other countries and distribute it to the general public.

Another issue is that it is flammable because it is cellulose. Although it is known that mixing a certain amount in plastics increases the strength, development seems to be suspended sometimes because flame retardancy cannot be provided.
We believe that a flame retardant that is highly effective for cellulosic materials is compatible.

Boric acid is known to have a high flame retardant effect on cellulose. Boric acid has long been recognized as having an effect on cellulose. However, in the flame retardant industry, there are almost no flame retardants that use boric acid as the main raw material, and the current situation is that they rely on halogens, phosphorus compounds, antimony, and the like.

We think that the compatibility with our sodium polyborate is good.
Isn’t dispersibility good if you settle well on cnf? I believe.

We have conducted tests to give the flame retardancy of cellulose nanofiber.
Samples were provided by several cellulose nanofiber manufacturers.

Aqueous flame retardant is made by mixing cellulose nanofiber and soufa. It was applied to a PP plate and subjected to a 45 ° C combustion test. There was no fire penetration.
The process of imparting hydrophilicity to PP by plasma treatment was necessary, but we will continue to study various materials in the future. The flame retardant mechanism is oxygen blocking by the firing of sodium polyborate and carbonization promotion by cellulose nanofiber functioning as a carbonizing agent. Originally, it was known that sodium polyborate can promote carbonization when used in combination with starch, so we thought that it could be applied to cellulose nanofibers with a similar structure.
Although the effect was almost the same as starch, it seems that there are some materials where cellulose nanofibers are more effective.

The application with cellulose nanofibers will be addressed in the future.

Since boric acid is also effective for wood preservation and insect repellency, isn’t it quite compatible with CNF?

No literature on the flame retardancy studies of cellulose nanofibers has yet been seen, so it can be seen as an indication of where to start. I hope that if flame retardancy can be achieved, it may be used as a material for automobiles and jet aircraft that require flame retardancy.
 

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When these are mass-produced, it may not be long before they will be used in building materials and automotive parts. What is not to be missed here is flame retardancy.
For example, the above polypropylene burns well. Cellulose nanofibers basically burn, too. surely.
Then it can be said that these composite resins burn well.

I think flame retardancy will be an important theme in the future when applying cellulose nanofibers to automobiles and railways.
Is a flame retardant added to the PP side or a flame retardant to the CNF side? Or should we put an effective flame retardant in both at the same time?

CNF is also attracting attention as an environmentally friendly material, so you will not add halogen flame retardants. Then, phosphorus-based, aluminum hydroxide, magnesium hydroxide, antimony, etc. can be mentioned, but it is not known how effective.
It is thought that boric acid, which is mainly used as a wood flame retardant, is effective for cellulose nanofibers. However, there are many types of boric acid, so I think that boric acid alone is not very effective. Isn’t boric acid based flame retardant that is distributed as a flame retardant well applied?

Any water-soluble flame retardant that is easily soluble in water will work well with CNF.

• Added May 2017
  We received a sample from a certain company, so we applied a flame retardant mixture of cellulose nanofiber and soufa to a PP plate and performed a 45 ° C combustion test.
  The material treated to impart hydrophilicity was able to withstand the test for 5 minutes without penetrating because the flame retardant remained uniformly on the surface.
  It is a material that has not been verified yet, but we want to keep an eye on it in the future.

The post Is there a starlight PMC cellulose nanofiber issue? first appeared on SOUFA INC.Boric acid flameretardant& Termiticide.

Flame was applied for 5 minutes by the combustion test method according to the 45 ° C combustion test method and JIS L1091, and the back surface temperature, penetration, and after-flame time were measured. Evaluate performance based on mass reduction rate and unit price area. There was no penetration of the plasma-treated material on the surface, and it was possible to demonstrate flame retardancy due to the foaming phenomenon unique to sodium polyborate. The test lasted 5 minutes.

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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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