Special Issue

Polymer Materials Technology

Development of Lightweight Fire-resistant Putty
Hidenobu Mochigase*1, Yutaka Suzuki*1, Eiji Miki*2,
Shota Mitsumune*2, Yoshihiko Ohba*2, Yukihiko Inoue*2

For the fire protection measure method of cables and through-holes of wall andfloor (closing the openings), it is necessary to use the fire-resistant materials
from the viewpoint of fire regulations. However, because the fire-resistant putty which is commonly used has large specific gravity and is heavy, the need of lightweight putty is very highfrom the viewpoint of carrying and workability during the construction. Therefore, the fire-resistant putty “DANSEAL-KP” which achieved a significant weight reduction and has half the weightin comparison to the conventional one has been developed. As a fire protection measure method at the various penetrations of wall and floor, the Minister of Land, Infrastructure, Transport
and Tourism certificate of the fire-resistant property defined in the Building Standards Act has
been obtained.

ABSTRACTINTRODUCTION
1.1. INTRODUCTION
In the buildings, when the various types of cables andpipes are installed, the through-holes (openings) will becreated at the wall or floor which divides the rooms or themachines. If these openings are not sealed properly forthe fire protection, the material such as a cable jacket
gets burned like fuse and the fire will spread to the next
room. Therefore, the opening filling material requires thefire-resistant property as per the Building Standards Act
and it is mandatory to take fire protection measures using
the material and construction method which obtained apublic certification1).
A typical construction method is to fill the openings withputty which has a fire-resistant property (Figure 1). This
fire-resistant putty consists of resins such as a liquid rubber or oil, inorganic filler and a flame retardant material.
There are curable and non-curable putties after construction. Curable putty can hold the openings firmly after construction, but because the dismantling is difficult, there isa drawback that it cannot cope with the re-construction
associated with renovation of building or expansion of theequipment (cable re-installation). On the other hand, thecontractor prefers non-curable putty because the dismantling and the re-construction for the cable re-installation
are easy. Because of the large amount of flame retardantmaterial which has large specific gravity to maintainenough fire-resistant property, many non-curable putty
products have large specific gravity and are heavy in*1 Furukawa Electric Co., Ltd. Research & Development Div.
Polymer Materials R&D Laboratories*2 Furukawa Techno Material Co., Ltd. Fire Prevention Div.

comparison to curable putty. In the fire-resistant measures at the high elevation place such as the ceiling or
the narrow space, the heavy putty has the disadvantage
for carrying and construction so there is a need to develop the lightweight putty.
In addition, several requirements listed below were considered.

Fire-resistant compartment (Building Standards Act）
Co-housing compartment (Fire Service Act）

3Ｆ

2Ｆ

1Ｆ

Residence

Residence

OfficeElectric room
BF

Figure1

CubicleCommonareas（MB）

Usage example of fire-resistant putty.

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Development of Lightweight Fire-resistant Putty

1. To work comfortably even at the construction site at
the low temperature.
2. The putty is hard to come off with good adhesion
between cables and building materials.
3. To have long term stability such as insulating properties and waterproof properties.
As for the fire-resistant property, the performance whichis capable to seal the openings effectively without burningout and without losing the shape in the fire-resistant testof one hour was targeted and the examination of thecomposition was conducted repeatedly. As a result, wehave succeeded in the development of a putty which hasa specific gravity of lower than 1.0. The product is lighter
than before and has an excellent fire-resistant property.

of weight-saving effect (specific gravity) and share resistance (collapse resistance), the artificial inorganic hollow
filler L3 and the organic hollow filler L4 were selected as
candidate materials.
Table 1

List of weight-saving materials.

size Specific Share
Weight-saving material Material Particle(um)gravity resistance Shape
L1(Artificial inorganic hollow filler) Inorganic

15-135

0.1-0.5×Spherical
form

L2(Natural inorganic hollow filler) Inorganic

150(ave.)

0.5-1.0

×Indeterminate
form

L3(Artificial inorganic hollow filler) Inorganic

5-300

0.5-1.0△

Spherical
form

50-70

0.1-0.2◎

Spherical
form

L4(Organic hollow filler)

Organic

INVESTIGATIONOF
OF COMPETITOR’SCOMPETITOR’S
2.2. INVESTIGATIONPRODUCTSPRODUCTS◎：No collapsing

In recent years, new fire-resistant putty manufacturers
entered the market and dealt with similar products. Our
main product is non-curable fire-resistant putty, but it
becomes difficult to differentiate the putty only by its fireresistant property. Therefore, we investigated the distribution of the specific gravity and the price per usage for thecompetitor’s fire-resistant putty in order to find an areathat can differentiate us from other companies (Figure 2).
As a result, it was found that there is no rival product in
the area where the specific gravity is less than 1.0 and theprice is inexpensive. So we targeted the area to develop
the putty which performance falls in this area.

To investigate the effect of the weight-saving and thefire-resistant properties, oil, inorganic filler and weightsaving material are mixed and processed into a putty-likeand then it was evaluated. As the inorganic filler, thematerial which there was a good effect on the shape stability after burning of putty in the past examination is used
(M2 in Table 3 of next chapter). When only artificial inorganic hollow filler L3 which has high fire-resistant property
is used as a weight-saving material, the specific gravity ofthe putty is calculated as 0.99, but the actual one was
1.16. From this fact, L3 is easily collapsed and it isexpected that it cannot withstand the kneading process.
On the other hand, in the case that only organic hollow
filler L4 is used as weight-saving material, the actual specific gravity after kneading was exactly same as the calculated value. From this fact, it was confirmed that the L4 ishard to collapse, even after kneading process. However,since L4 is organic, it is burnt out in a fire so its fire-resistant property was insufficient. In order to take an advantage of those 2 hollow fillers and compensate for the disadvantage, the mixing composition of 2 hollow fillers is
examined. As a result, the fire-resistant putty which has a
specific gravity exactly same as the calculated value andholds the shape after a fire has been developed. It was
found from above results that the putty which has simultaneously a lightweight and a fire-resistant property can beobtained by mixing the 2 types of weight-saving materials.

Investigation of competitor’s products

Setting the development goals (cost and specific gravity)
2.0

Our product and competitor’s products
Specific gravity and price

Heavy

Specific gravity

1.5

1.0

0.5

Area which is not in
the competitor’s
non-curable putty
Targeted specific gravity
is less than 1.0

2,000

4,000

Thermal expansion type putty
Competitor’s curable putty
Competitor’s non-curable putty
DANSEAL-P (non-curable putty)

6,000

8,000

10,000Price per usage（Yen/L）△：Partial collapsing

×：Collapsing

Expensive

Figure 2 Investigation result of competitor’s products(Relationship between price per usage and specificgravity)3.

3.

EXAMINATION OF WEIGHT-SAVINGEXAMINATIONOF WEIGHT-SAVING MATERIALSMATERIALS

For weight-saving, the survey results of weight-saving
materials are summarized in Table 1. From the view point
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Development of Lightweight Fire-resistant Putty③The cube is removed from the furnace after the predetermined time and observed.

List of experiment for weight-saving material
examination.

Artificial inorganic
hollow filler L3

Organic hollow
filler L4

L3+L4 Mixed
Composition

Wt.% (Oil, L3 ,M2)
30.2%, 32.1%,
37.7%
Gravity
Cal culated : 0.99
Actual : 1.16

Wt.% (Oil, L4,M2)
42.4%, 4.5%,
53.1%
GravityCalculated : 0.99
Actual : 0.99

Wt.% (Oil, L3, L4, M2)
41.0%, 3.8%,
3.8%, 51.3%
GravityCalculated : 0.99
Actual : 0.99

× Hollow filler
collapsed→ Little effect forweight-saving◎ Not burn out◎ Hollow filler notcollapsed× Burn out◎ Hollow filler notcollapsed○ There is residue

4.4. OPTIMIZATIONOPTIMIZATIONEXPERIMENTS
EXPERIMENTSOF
OFFIRERESISTANT
PUTTY
COMPOSITION
FIRE-RESISTANT PUTTY COMPOSITION
The inorganic filler other than the oil and the weight-saving material described above is used for the constituent
materials of the fire-resistant putty. Optimum amount of
the inorganic filler was examined. The inorganic fillers
which were investigated this time are listed in Table 3. M1(aluminum hydroxide) and M3 (magnesium hydroxide)
which are metal hydroxide among inorganic fillers areuseful because they exhibit a flame retardant effect by adehydration endothermic reaction2)-4). This time, M1 which
has a material cost lower than M3 is selected as one of
the inorganic filler. Also, by mixing M2 into the putty, theeffect that the residue of putty during the combustion
becomes hard to collapse was confirmed. Therefore, it
was decided to adopt the combination of M1 and M2.
Then the basic composition of oil, weight-saving material,
inorganic filler M1 and M2 are selected and the optimization experiment of inorganic filler mixing ratio was conducted.
Table 3The evaluation was done by checking the shape of theresidue after heating visually and by rating the easiness ofcollapse when touching it.
As illustrated in the pictures of before and after test, alarge difference of the residues after heating test wasobserved (Figure 3). In this evaluation, the composition
which is already broken when removed from the electric
furnace or collapses easily when the residue is touched,
has a poor fire-resistant property also in the case that it issubjected to a combustion test simulating the actual construction conditions. On the other hand, in the case when
the residue keeps the shape without collapsing and does
not shrink even after this test, the tendency that the fireresistant property is improved in the combustion test of
actual construction conditions was confirmed. The results
were summarized in Figure 4. It was found that if the ratioof the inorganic materials (total volume of artificial inorganic hollow filler L3, inorganic filler M1 and M2) is morethan 25 volume % and the ratio of M2 within the inorganic
fillers is more than 0.4 (to be 1 by adding M1 and M2), thefire-resistant putty can be obtained.

Judgment of fireproof
property Is the shapemaintained?
(Is spherical form
maintained?)

Inorganic filler

Specific
gravity

M1 (Metal hydroxide)

2.0-3.0◎

Hardness ofcollapsing after
combustion△

M2 (Natural mineral)

2.0-3.0○◎

M3 (Metal hydroxide)

2.0-3.0◎△

M4 (Natural mineral)

2.0-3.0△

×◎：Excellent○：Good △：Slightly poor

×：Poor

A simplified fire-resistant test was conducted by using
an electric furnace. The evaluation method is described
below.
①The obtained composition is formed into a cube.
②The cube is put into the preheated furnace and left
for a certain time.

×

Ruptureandcollapse×

Crazing
Electric furnace : 400℃
（10 min.）Shaperetaining
GOOD○

Figure 3 Judgment criteria of the electric furnace test.

List of inorganic fillers.
Flameretardant
property

Expansion
andexplosion

ＮＧ
Ｎ

35
Inorganic filler mixing ratio (volume %)Table 2

Symbol meaning
Blue ：Pass
Yellow：Insufficient
red ：Inappropriate

Inorganic
material ratio
64 vol%30
25Inorganic material ratio
more than 25 vol. %M2 ratio more than 0.4

20
15
10
0

0.2

0.4
0.6
M2/（M1＋M2）

0.8

1

Figure 4 Optimization experiment for inorganic filler mixing ratio.

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Development of Lightweight Fire-resistant Putty

Hand100 mixing
or more impossible

110or more 109 109

Competitor’s putty A
Competitor’s putty B
DANSEAL-KP

100

80

A littlebit
60 hardHand40 mixing
easy
20

Available range

In addition to the fire-resistant property, the fire-resistantputty requires the easy workability without hardening
even at the construction site at the low temperature of thewinter season. Because many conventional types of putty
become hard at the low temperature, they are usuallyused after warming. Therefore, it is necessary to examine
the hardness at the low temperature for this development.
Thus, by conducting the test to investigate the easinessof compression (easiness of collapse) of putty, the comparison with competitor’s product was carried out. The
testing method is shown below (Figure 5).

Compression test

Force (N)5.5. WORKABILITY
AT THETHE
WORKABILITYEVALUATIONEVALUATION AT
LOW
LOWTEMPERATURETEMPERATURE (TEMPERATURE(TEMPERATURE
DEPENDENCE
HARDNESS)
DEPENDENCEOF
OF PUTTY
PUTTY HARDNESS)

70
61
59

45.5
39

－10℃

0℃
10℃
Temperature
（℃）

39
32
20℃

33
29
26
40℃

Figure 6 Relationship between workability of putty and working
temperature.

6.6. EXAMINATIONFORFLAME
FLAMERETARDANCYRETARDANEXAMINATION FOR
CY
IMPROVEMENT
OF THEFIREIMPROVEMENT
OF THE
FIRE-RESISTANTRESISTANTPUTTYCOMPOSITIONPUTTY COMPOSITION
①

③

④

⑤

V-0 of UL 94 vertical flame test is mentioned as one of themost severe flame retardant level. The study was conducted to meet this flame retardant level. The testing
method is to broil the putty formed in a strip as shown in
Figure 7 in the flame for a certain period of time frombelow, to measure the combustion time and to make thedetermination whether the fire disappears within a prescribed time in seconds.

Figure 5 Testing method of compression.

①The putty is formed into cylindrical shape.
②Leave it at measuring temperature for a certain period of time.
③The sample is placed into the center of a steel pipe
which is shorter than sample as shown in the pictureand has a margin space in a diameter.
④Press the push-pull gauge just above the sample andcrush the sample at a constant rate.
⑤Crush the sample till the height of putty reaches thesame height of the steel pipe and measure the maximum force. (The force N which requires collapsing
putty.)
In case of the competitor’s product of A and B, theforce became more than 100 N (Figure 6), which is difficult for hand mixing. On the other hand, it was confirmedthat the newly developed “DANSEAL-KP” is difficult tobecome hard (about 70 N) and has an excellent workability at the low temperature by optimizing the combinationof the resin components.

Figure 7 Vertical flame test (UL-94).

The samples, for which the types of flame retardantmaterials and quantity were modified, were prepared andthe combustion test was conducted. The flame retardantmaterials which can achieve V-0 were F2 and F4 which
are phosphorous-based. F2 is treated as a dangerous
material in some areas and needs attention in handling.
Therefore, F4 is used as the flame retardant material by
mixing it to the resin at a weight ratio of more than 5% byweight this time.
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Development of Lightweight Fire-resistant Putty

Physical property list of flame retardant materials.

Flame retardant materiala

Specific gravity

Flame retardant
property

F1 (Phosphorous based)

1.0-2.0

×F2 (Phosphorous based)

2.0-3.0○

F3 (Inorganic)

2.0-3.0

×

F4 (Phosphorous based)

1.0-2.0○○：Acceptable

×：Failure

1200
1000
Temperature（℃）

Table 4

800
600
400
200
0

FIREPROOFTEST
TEST
7.7. FIREPROOF
Assuming the setup of the actual situation where theround hole of 160 mm in diameter is set through the autoclaved lightweight concrete of 75 mm thickness, the fireresistant putty is applied to the testing specimen throughwhich the cable and pipe are penetrating as shown in
Figure 8. The 60 minutes fire-resistant test based on thetesting method certified by the Minister of Land,
Infrastructure, Transport and Tourism was conducted. The
heating was performed according to the standard heating
curve based on ISO 834 in Figure 9 and heated to 945℃.
As a backup material to prevent putty fall, a block of aceramic blanket wrapped by nonwoven fabric is built inthe openings and the developed putty was filled in it witha thickness of 10 mm, 20 mm and 50 mm. As per the
result of the fire-resistant test (Figure 10), it was confirmed that even the putty of 10 mm thickness has a sufficient fire-resistant property (Table 5). This is one third filling thickness in comparison to the conventional construction method. As per these testing results, it is confirmedthat this newly developed product, consisting of a weightsaving material, an inorganic material and a flame retardant material mixed into the base oil at optimum ratio,
has an excellent fire-resistant property and also has a
specific gravity of less than 1.0. This means the fire-resistant and lightweight properties are both satisfied.

Cable
Compartment A

20

40

60
80
Time
（min.）

100

120

Figure 9 Standard heating curve based on ISO834.

Figure 10 Pictures of fire-resistant test.
Above Upper view
Below Entire view

Table 5
Support blanket
Concrete0

Optimization of putty thickness.
DANSEAL-KP

Used Putty

DANSEAL-KP

Filling
thickness（mm）

Backup material

Beforetest
Picture

10

20

50

Furukawa Review, No. 45

2014Compartment B
Figure 8 Example of construction method.

After
test
Picture6

Development of Lightweight Fire-resistant Putty

CONCLUSION
8.8. CONCLUSION
By this development, the non-curable putty which is notavailable in the current market and has a specific gravityof less than 1.0 has been developed. This newly developed product has an advantage that there is a property
which is difficult to harden even at the low temperature.
This product can be used in the construction method ofround hole in wall and in floor, and has obtained theMinister of Land, Infrastructure, Transport and Tourism
certificate. This product has been already commercialized
as a part of the materials for the kit of “ICHIJIKAN PAT”
and “ICHIJIKAN MARUYUKA”. In the future, we will try to
get certification of other construction methods in order to
use it in various other applications.

REFERENCES
1) Building Standard Low Enforcement Ordinances, Article 129-2-5,
Section 1, Paragraph 72) Hitoshi Nishizawa: “Flame Retardant, Flame Retardant Materials
Utilizing Technology” CMC Publishing Co., Ltd., (2004), 119 (inJapanese)
3) Hitoshi Nishizawa: “Development of New Polymer Materials Flame
Retardant Technology –State of the Art Technology, Materials,
Recycling, Evaluation, Patent and Regulatory”, GIJYUTUKYOUIKUSYUPPANNSHA, (2006), 125 (in Japanese)
4) Hitoshi Nishizawa: “Flame Retardant Polymer =Its Chemistry andActual Technology=”, TAISEISYA LTD. (1989), 71 (in Japanese)

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