Product Introductions

Heat Resistant Acrylic Rubber
L6070
Acrylic rubber is positioned as the third rubber material

1. Introduction

following fluororubber and silicone rubber for applications

For automobiles, many rubber products are used asthat require both oil resistance and heat resistance.

important functional parts, such as oil seals, belts, hoses,

Figure1 shows the positioning of oil resistance and heatpacking, O-rings, and diaphragms. This is because ofresistance of various rubber materials.

the unique properties of rubber materials that cannot

Acrylonitrile butadiene rubber, which has been widely

be replaced by other materials, such as ① large

used as an oil-resistant rubber, lacks heat resistance for

deformation capability, ② flexibility and ③ good

automotive applications which are becoming increasingly

1）

In recent years, the demand for sealing materials has

been increasingly replaced by acrylic rubber due tobeen increasingly growing for applications used in theprice issues balancing performance and costs.

engine periphery of automobiles as they are used in everharsher environments. Such environments include not
only oil and fluid resistance but also maintenance-freelong-life characteristics, space saving in the engine
compartment, heat resistance required by higher
performance and higher output, and others. Table1 shows
the seal parts and materials used in various types of oil.

Low ← Oil Resistance → Highsophisticated in performance. Also, fluororubber has

No.41

Table1 Oil and fluid resistant rubber parts for automobiles ２）
Oil classification
Engine oil

ATF mission
OilPSF

Fuel

Coolant
Brake fluidEtc.

Part nameCrank oil seal
Cam oil seal
Valve stem seal
Oil pan packing
Head cover packing
Oil cooler hoseO-rings
Transmission oil seal
Oil cooler hoseO-ring and packing
Power stay hose
Rack end seal
Oil pump oil seal
O-ring and packing
Fuel hose
Evapo hose
Fuel pump diaphragm
Check valves
High pressure fuel hose
Regulator diaphragm
Injector seal
O-ring and packing
Radiator hose
Heater hoseBrake hose
Master cylinder cup
Wheel cylinder cup
Caliper seal

Material used
VMQ、FKM
VMQ
FKM
NBR、ACM
NBR、ACM
NBR、ACM
NBR、ACM
ACM、VMQ
NBR、ACM
NBR、ACM
NBR
U、NBR
NBR
NBR
NBR
NBR
NBR
NBR、FKM
NBR、FKM
NBR、FKMFKM
NBR、FKM
EPDM
EPDM
NR、SBR、CRSBR
SBR
EPDM

Summer 2021

damping characteristics .

Low

Figure1←Heat Resistance→HighOil resistance and heat resistance of various
rubber materials

2. Characteristics of L6070
Acrylic rubber is a copolymer composed mainly ofacrylic acid ester, and its ASTM abbreviation is ACM.
The chemical structure of acrylic rubber is shown inFigure2.

Figure2

Chemical structure of acrylic rubber
22

Heat Resistant Acrylic Rubber L6070

The characteristics of acrylic rubber differs depending

developed material L6070 and the conventional materialon the combination of three types of monomers with

L1270 are described below.

different side chains（ethyl acrylate: EA, butyl acrylate:BA, and 2-methoxyethyl acrylate: MEA）. The chemical2-1）Compression set properties

structures of the main component monomer species

As an index of the heat resistance of sealing materials,

3）

the compression set is used. Under the sameand their characteristics are shown in Figure3 .

environment, the lower the compression set is, thelonger the use you can expect as a quality sealingmaterial.
The method of measuring and calculating thecompression set is shown in Figure4 4）.

EABA
MEA
◎：Excellent○：Good△：Inferior

Figure3 C hemical structures and characteristics of acrylic
rubber monomers

Figure4 Method of measuring and calculating compression set

Since the main chain of acrylic rubber consists only ofIn general, the compression set of 80% is used as thesaturated bonds, it is necessary to introduce functional

life expectancy of materials used for sealing materials 5）.

groups with crosslinking points. Table2 summarizes theIn this report, in order to calculate the seal life and thecharacteristics of acrylic rubber according to thetime to reach the compression set of 80% under thedifferences in cure sites.

environment of 150 ℃ which is required for seals used

Table2 T ypes and characteristics of functional groups at
various cure sites3）
Cure site

Cure rate Processability

Storagestability

Compression
Heat
setresistanceactive chlorine
group

〇×△〇〇

Epoxy group

×〇

〇〇〇

Carboxyl group

〇〇〇〇

〇

Due to its characteristics, acrylic rubber has been used
for oil seals and hoses in the engine periphery ofautomobiles. Our existing acrylic rubber L1270 has also
been used as oil seals and gaskets in many engine
periphery applications, but it is becoming more difficultin the engine periphery, the compression sets of L6070
and L1270 are plotted to calculate the time to reach thecompression set of 80% from the approximate equation.

Compression set（%）

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Heat resistance Oil resistance Cold resistance
◎
○
△
○
△
◎△
◎
○

for it to meet specifications under the high temperatureenvironment near the engine in recent years.
By utilizing our unique compound design technologythat we have cultivated over the years, we havedeveloped L6070 acrylic rubber, which has improved
heat resistance while maintaining the oil resistance ofacrylic rubber. The various characteristics of the23Time（hr）

Figure5Compression set at 150℃ in Air

Product Introductions

Table3 T ime at compression set of 80% at 150℃
Approximate
expression

Rubber CodeL6070

y＝1.1575x0.4304

L1270

y＝1.83x0.44

Time at compression
set of 80%

The API standard is a standard to classify quality,
setting the fuel efficiency, heat resistance, and wear

4

resistance of engine oil. It had classifications from SA to5.35×103

SP, but some of them have been abolished by 2020.

1.88×10ILSAC is a standard that requires additional fuelCalculated from an approximate equation, the time toefficiency and classifies the SH to SP classifications ofreach the compression set of 80% in air at 150 ℃ is

API into GF-1 to GF-6. Table5 shows the quality

1.88×104 hours for L6070 and 5.35×103 hours for L1270.

classification of automotive engine oil 6），7）.

This indicates that the life of L6070 is expected to be
more than 3.5 times longer.
L6070 has good compression set properties even in ahigh temperature environment of 150 ℃ or higher.
When evaluated under the same test time, thecompression set of L6070 and that of L1270 areequivalent, respectively 170 ℃ and 150 ℃, which meansthat an increase in service temperature can beexpected. The results of the compression set test under

API standard and ILSAC standard
ILSAC standard

Performance

Low

GF-1
GF-2
GF-3
GF-4

Performance

GF-5

High

GF-6

As for the SAE standard for classifying viscosity, theCompression set（%）

SAE J300 standard established by SAE is used. Forexample, in the case that it is noted as 5W-30, theSummer 2021

high temperature environments are shown in Figure6.

Table5
API standardSASBSCSDSESFSGSHSJSLSMSNSNPlus
SP

notation on the left side indicates viscosity at lowtemperatures while the notation on the right side
indicates viscosity at high temperatures. Both indicatethat the higher the number is, the harder the engine
oil becomes. Table6 shows the viscosity classificationof automotive engine oil8）.
Figure6Temperature dependency of compression set

For the evaluation of engine oil resistance properties,2-2）Engine oil resistance propertiesthe following standards were used from the viewpoint

Automotive engine oil is classified by standards eachof availability: API: SN/CF（for simultaneous use offor its quality and viscosity. Each standard is shown inboth gasoline and diesel vehicles）, ILSAC: GF-5（fuelTable4.

efficiency, exhaust gas purification, oil degradation
Table4

Type ofstandard

Classification of engine oil

Standard name

Description

prevention, heat resistance and wear resistance）and
SAE: 5W-30（usable even at −30℃ outside temperature

Performance classification
API：American Petroleum
standards for internationallyInstituteused engine oilsQuality
standard ILSAC：InternationalStandards that require more
Lubricant Standardization fuel-efficient performanceand Approval Committee
than API+ medium viscosity at high temperature）.

Viscosity SAE：Society of Automotive Standards for classifying oilstandard Engineers
viscosity

resistant. Figure7 shows the change of volume of both

The change of volume of both L6070 and L1270 after
the immersion test at 150℃ for 70 hours was small（lessthan 10%）, confirming that both materials werematerials after the immersion test.
24No.41

Heat Resistant Acrylic Rubber L6070

Table6SAE2-4）Product shapeJ300Low temperature
High temperature viscosity
viscosity
SAE
Pumping
Kinematic viscosity
Viscosity atviscosity CCS viscosity（cP）/viscosity（cP） （cSt）（100℃） high shear（cP）
grade
temperature /temperature（150℃、Minimum Maximun 106S-1min.）（℃）（℃）

Since acrylic rubber L6070 has the same level of0W

6,200/−35 60,000/−403.8――

5W

6,600/−30 60,000/−353.8――

and large-diameter products such as O-ring（VALQUA

10W 7,000/−25 60,000/−304.1――

15W 7,000/−20 60,000/−255.6――

20W 9,500/−15 60,000/−205.6――

25W 13,000/−10 60,000/−159.3

―

―

4

<6.1

1.7

processability as that of general synthetic rubber, it canbe used to manufacture various cross-sectional shapesNo. 640）, V-packing（VALQUA No. 2631）, and X-ring（VALQUA No. 641）.
2-5）Mechanical properties

8―

―

12―

―

5

<7.1

2.0

The results of physical properties and various durability

16―

―

6.1

<8.2

2.3

20―

―

6.9

<9.3

2.6

tests of L6070 and L1270 are shown in Table8.

30―

―

9.3

<12.5

Table840

―

―

12.5

<16.3

Characteristic40――

12.5

50

―

―

16.3

2.9
3.5（0W-40, 5W-40,10W-40）
3.7（15W-40, 20W-40,<16.3
25W-40, 40monograde）
<21.9
3.7

60

―

―

21.9

<26.1

3.7

Comparison of physical properties

Hardness
Tensile strength
Elongation

Test method

Unit

L6070

L1270

JIS K 6253

SHORE A71

72

MPa

11.8

11.0%

250

190

%

712POINT＋1＋2%－3＋3%－6－3

POINT－4±0SN/CF,
GF－5%＋1－65W－30 oil%－6－12150℃ x70h%＋3.6＋2.5

JIS K 6261℃

－21.5 －20.7

JIS K 6251

Oil resistance

Volume change（%）

Summer 2021

Condition:150℃× 70hr
Test piece:50mm × 25mm × 2t

Heat resistanceCompression
set factor

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Figure7 Change of volume after gasoline oil immersion test2-3）Low temperature properties

JIS K 6262
25% compression 150℃ x70h
φ29×h12.5
Change ofhardness
Change oftensile strength
Change ofelongation
Change ofhardness
Change oftensile strength
Change ofelongation
Change ofvolumeLowtemperature TR10 value
properties

JIS K 6257
150℃ x70h

JIS K 6258

※ These are measured values, not standard values

The low-temperature properties were confirmed by thetemperature restraction test（TR test）. L6070 showed
the same TR10 value as L1270, and it was confirmed to3. Applications

have the low-temperature properties that can be used

The newly developed acrylic rubber L6070 is expected

as a sealing material in the engine periphery. Table7

to be applied to the automotive market（especiallyshows the TR values for L6070 and L1270.

engine periphery）.
※O‌ i l f i l t e r g a s k e t s （a u t o m o b i l e s , c o n s t r u c t i o nTable725machinery, agricultural machinery, etc.）head coverComparison of TR values
L6070

L1270

TR10（℃）

－21.5

－20.7

TR30（℃）

－16.5

－16.1

TR50（℃）

－12.9

－12.9

TR70（℃）

－8.7

－9.3

gaskets, oil seals, oil pump gaskets, etc.

Product Introductions

4. Conclusion

5. References

The acrylic rubber L6070 introduced here is a material1）K oda Tadashi, Journal of the Society of Rubberwith upgraded heat resistance properties while

Science and Technology, Japan, 55, 689-697, 1982

maintaining the same level of oil resistance as that of2）Hiroshi Yoshida, Journal of the Society of Rubber

conventional materials. In automotive applications,

Science and Technology, Japan, 58, 141-147, 1985

there is a trend where the operating environment is3）Mamoru Sugiyama, Journal of the Society of Rubber

becoming hotter and hotter and thus seal materials are
required to have high heat resistance. We believe that

Science and Technology, Japan, 89, 22-27, 20164）Hirofumi Zushi, Valqua Technology News, No.36, 25-

this new material can handle the environment

28, 2019

adequately. In addition, the quality standard for engine

5）Toshio Kawamura, Valqua Review, Vol.26, No.6, 1982

oil was revised in October 2020. Since this revision has6）American Petroleum Institute, 2020

introduced stricter standards for the environment and7）I nternational Lubricant Standardization andoil performance has been improved, it is expected thatthe requirements for sealing products are also going toApproval Committee, 20208）SAE International, SURFACE VEHICLE STANDARD,change. We, as a seal manufacturer, will continue toSAE J300, 2015

strive to develop new materials and improve existingmaterials by quickly capturing the latest trends in theSummer 2021

market in order to meet the demands of our users.

Hirofumi Zushi
Elastomer Team,
Product Development Division
Research and Development Department

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