Material information

The materials of SKT products, which are generally made of synthetic rubber, PTFE, leather, cork, felt or fabric-reinforced rubber. The designation of materials is shown in the below figure:


rubber	PTFE	leather	cork	felt	fabric-reinforced rubber	Code letter indicates the material used at the lip section of the seal.

Figure 1

Type of material	ASTM abbreviations	Trade marks(*)	SKT material coding
Nitrile rubber	NBR	Perbunan, Krynac, EuropreneN, Nipol	N
Hydrogenated nitrile rubber	HNBR	Therban	H
Polyacrylic rubber	ACM	HyTemp	P
Silicone rubber	MQ, VMQ, PVM	Silopren, Rhodorsil	S
Fluorocarbon rubber	FKM	Tecnoflon, Viton	V
Ethylene-propylene rubber	EPM, EPDM	Keltan, Nordel	E
Styrene-butadiene rubber	SBR	Kosyn	R
Natural rubber	NR	SMR	T
Thermoplastic Polyurethane	TPU	Desmopan	L
Polytetrafluoroethylene	PTFE	Algoflon, Teflon, Fluon	F
Polyamide	PA	Nylon	C
Leather	-	-	D
Cork	-	-	M
Felt	-	-	K

(*) Trade names are for information only. SKT does not necessarily use or endorse the mentioned products.

Table 1

Properties of the materials used by SKT (See Note 1)

Material code: N

Nitrile rubber (NBR)

Nitrile rubber is a general purpose material resistant to a large variety of oils and greases. It is the workhorse of oil sealing owing to cost/performance compromise. Different nitrile compounds are available for fuels and for industrial fluids. Nitrile rubber is generally serviceable between -40°C and 105°C; it can withstand 120°C intermittently. It is not recommended for glycol-based brake fluids and EP-type lubricants. (See Note 2)

Material code: P

Polyacrylic rubber (ACM)

Polyacrylic rubber possesses greater resistance to heat and to EP-type lubricants than nitrile rubber. Its' service temperature limit is 150°C. Ozone resistance is good, but low-temperature performance, fuel resistance and water resistance are poor. The material finds popular application in gear box seals.

Material code: S

Silicone rubber (MQ, VMQ, PVMQ)

Silicone rubber can be used in the range of -60°C to 200°C. Temperatures up to 250°C are tolerated intermittently. The main field of application is crankshaft seals. Silicone rubber exhibits high elasticity and good resistance to air and ozone. Relatively poor mechanical properties and vulnerability to fuels and EP-type oils are among the disadvantages.

Material code: V

Fluorocarbon rubber (FKM)

Fluorocarbon rubber can operate between -30°C and 220°C. It is resistant to majority of greases, fuels, oils and chemicals. It is recommended for crankshaft seals at high temperature and high RPM. The high cost of fluorocarbon rubber is usually justified by its all around performance. The material is not suitable for ketones, amines, esters and ethers.

Material code: E

Ethylene propylene rubber (EPM, EPDM)

Ethylene propylene rubber can be employed between -40°C and 150°C in media where resistance to phosphate-ester fluids, glycol-based brake fluids, steam, oxygen and ozone is required. Its resistance is poor in fuels and petroleum-based oils.

Material code: R

Styrene butadiene rubber (SBR)

Styrene-butadiene rubber possesses good resistance to glycol-based brake fluids, bases and alcohol. The service temperature is -50°C to 100°C. It is not suitable for fuels and petroleum based oils.

Material code: T

Natural rubber (NR)

Naturel rubber is similar to SBR in chemical resistance, and is used between -60°C and 90°C where good resilience and mechanical properties are demanded.

Material code: F

Polytetrafluoroethylene (PTFE)

Polytetrafluoroethylene resistant to practically all industrial chemicals. It is serviceable between -260°C and 260°C. PTFE is an ideal material for non-lubricated bearings owing to its extremely low coefficient of friction and free of stick-slip. Certain types are excellent in electrical insulation. PTFE is used virgin or filled with glass fibre, carbon, graphite, bronze or molybdenum sulphide depending on the application.

Material code: C

Polyamide (PA)

Polyamide is commonly known as "NYLON". It can be used in the range of -20°C to 90°C. Special types can function up to 140°C. Polyamide has good friction and abrasion properties. It is resistant to oils, fuels, esters and ketones.

Material code: D

Leather

Leather receives special treatment in order to attain the outstanding properties of endurance, resistance to wear and oil retention. The leather seals of SKT can function between -70°C and 100°C in applications involving intermittent lubrication and worn-out shafts. Nevertheless, leather can not be considered a perfectly reliable material because of natural heterogenity.

Material code: K

Felt

Felt generally serves to keep off dust, dirt, and to prevent oil splashes. It is not recommended for use in continious and wobbly shafts.

Material code: H

Hydrogenated nitrile rubber (HNBR)

Hydrogenated nitrile rubber is derived from normal NBR polymers. The materials so prepared are characterised by high mechanical strength and by improved abrasion resistance. Media resistance is as NBR. Its' service temperature limit is 150ºC.

Material code: L

Thermoplastic polyurethane (TPU)

TPU has good mechanical properties with opportunities for efficient processing by injection moulding. The essential advantages of TPU are high abrasion resistance, flexibility over a wide temperature range, good resistance to oils, greases and many solvents and good resistance to weathering. It is not recommended for acids, alkalis and hot water or steam.

Note 1: The given information is intended only as a guide. The properties of materials can vary greatly depending on the compound. The service temperature ranges are affected appreciably by the media of application. In case there are doubts about the suitability of a material for a particular application, SKT should be consulted for assessment.

Note 2: Sealing elements of nitrile rubber, constituting the majority of SKT products, do not bear the material code letter (N) in the code numbers. Products made of other materials are identified by respective material code letters appearing at the end of the code numbers.

Examples:

The rotary shaft seal 047383 is made of nitrile rubber.

The rotary shaft seal 047383-S is made of silicone rubber.

The O-ring 4H-776-V is made of fluorocarbon rubber.

Note 3: Letter (-Z) means that the garter spring is of stainless steel.

SKT Yedek Parça ve Makina Sanayi ve Ticaret A.Ş.

Organize Sanayi Bölgesi, Yeşil Cad., No: 17, 16140 Bursa.
Phone: (+90 224) 2434100 - Fax: (+90 224) 2431424
E-mail: skt@skt.com.tr URL: www.skt.com.tr

SKT A.Ş. is a company of Diniz Holding.

Site last updated: August 2, 2007
Database last updated: July 22, 2008