KEP_Product_240309

Stress (MPa)

0

2

4

6

8

10

Strain (%)

Figure 2-4. Stress-stain curves of F20-03 at various temperatures (ISO 527, Testing speed 50 mm/min)

Tensile strength (MPa)

Temperature (°C)

Figure 2-5. Tensile strength of KEPITAL versus Temperature (ISO 527, Testing speed 50 mm/min)

2-4. Impact strength

The impact strength is the energy to withstand a dynamic impact rather than static stress.

There are several ways to evaluate impact strength, and the Charpy(ISO 179) and Izod (ASTM D256) tests are mostly used to determine the toughness of plastic materials. Impact strength can be measured in either notched or un-notched sample; however, it is generally evaluated after notch-processed on a specimen so that the stress of an impact load may be concentrated.

KEPITAL has good impact resistance at low temperatures (-30 to -20 °C) as it has a very low glass transition temperature below -40 °C.

	Grade	F20-03	FG2025	TE-24
	Impact strength	6.5	8	18
	(kJ/m2)

Table 2-1. Notched Charpy impact strength of KEPITAL (ISO 179, 23 °C)

2-5. Shear strength

The maximum shear stress at which a material can be maintained prior to shearing (punching) is referred to as shear strength. Shear strength represents the maximum load required to completely shear a sample by the maximum strength of a material that is influenced by shear stress. The shear strength is determined by dividing the force required to shear the specimen by the area of the sheared edge. (ASTM D732)

Shear strength (MPa)

Temperature (°C)

Figure 2-6. Shear strength of KEPITAL F20-03 at various temperatures (ASTM D732, t 3 mm, testing speed 1.25 mm/min)

2-6. Specific volume

Specific volume (cm3/g)

Temperature (°C)

Figure 2-7. P-v-T curves of KEPITAL F20-03

As shown in Figure 2-7, the molding shrinkage of KEPITAL results from both its high crystalline alignment in solidification and its thermal shrinkage from the molten state to the solid state as a function of temperature and pressure. Furthermore, higher cooling rates or cooling under higher pressures causes less volume shrinkage. Figure 2-7 notes a steep volume shrinkage of KEPITAL around 160 °C in the specific volume curves.

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2-7. Hardness

Hardness of a plastic material is usually indicated in terms of Rockwell Hardness that measures surface pen-etration with a steel ball under specific conditions.

The Rockwell Hardness scale is dependent on ball diameter and load (ASTM D785). Rockwell Hardness of a plastic is divided into a M scale or a R scale, and the higher number the higher hardness.

The following figure shows the hardness differences as a function of the viscosity of the standard unfilled grades.

Hardness (M Scale)

Figure 2-8. Hardness of standard unfilled grades

The following figure shows the hardness differences of the impact modified grades.

Hardness (M Scale)

F20-03

TE-22

TE-24

Figure 2-9. Hardness of impact modified grades

2-8. Poisson’s ratio

Poisson’s ratio ( ) is defined as the ratio of the transverse strain to longitudinal strain of plastic materials and it is useful to calculate this physical property in perpendicular direction to loading.

Poisson’s ratio is dependent on time, temperature, stress etc. The ratio of KEPITAL F20-03 is approximately 0.35.

NH

H

L

Y=

NH/H

NL/L

NL

Figure 2-10. Poisson’s ratio

The property values of a material used for structure analysis are tensile modulus (E) and Poisson’s ratio ( ). With Poisson’s ratio ( ) and the tensile modulus (E), the material’s shear modulus (G) can be simply calculated. It is because a material deforms not only in the tensile direction but also in its perpendicular direction.

G =

E

2(1+Y)

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2-9. Behavior under long-term static stress

When static stresses are loaded to thermoplastics constantly, not only does the initial strain occur but also an incremental strain is followed as time goes by due to its viscoelastic property. Creep is the total strain of initial elastic deformation and plastic flow for loading time. The creep behavior of KEPITAL is time, temperature and load dependent. Therefore a good resilient material like KEPITAL recovers its original shape entirely or partially when the loaded stress is removed.

The influential factors on KEPITAL

(1)Stress, environmental factors; temperature, high humidity, chemicals etc.

(2)Molecular weight and filler content

(3)Part design

The following figures show the tensile creep characteristics and flexural creep characteristics of KEPITAL.

Strain (%)

Loading time (h)

Figure 2-11. Tensile creep curves of KEPITAL (23 °C, 20 MPa)

Strain (%)

Loading time (h)

Figure 2-12. Tensile creep curves of KEPITAL (23 °C, 12 MPa)

F10-03H, 18 MPa

F10-03H, 13 MPa

Strain (%)

Loading time (h)

F10-03H, 18 MPa

F10-03H, 13 MPa

Strain (%)

Loading time (h)

Figure 2-13. Tensile creep behavior of KEPITAL F10-03H

(%)
Strain					F20-03	20 MPa
					F20-03	10 MPa
					FG2025 40 MPa
					FG2025 20 MPa

Loading time (h)

Figure 2-14. Flexural creep curves of KEPITAL FG2025 and F20-03

(23 °C)

The creep failure is a phenomenon in which a part strained and then eventually fractured under a constant stress for a long period. Because plastics have viscoelastic properties, creep strain is more readily exhibited than in metallic materials. In particular, when designing parts such as pressure resistant containers, screw fasteners, insert formations and insertion parts for a posttreatment process, the creep property of material must be considered in advance.

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Figure 2-15 shows the creep rupture of KEPITAL F20-03 with various loads and temperatures.

	80
	60
								23 °C
	40
(MPa)								60 °C
stress	20
								100 °C
	10
Tensile
	8
	6
	4
	1	10		102		103		104
				Time to rupture (h)

Figure 2-15. Creep rupture curve of KEPITAL F20-03

2-10. Property under cyclic stress

Designing based on a dynamic structure analysis, obtained where a part is subjected to loading once, can only provide information if a part can be used without fracture under the single loading environment.

Engineering parts are often subjected to the fatigue by stress or strain which is applied repeatedly and periodically over a long period. Fracture or failure that results from this phenomenon is called fatigue failure. Therefore, when designed, the fatigue properties of a material should be considered.

Fatigue strength of plastics is generally determined without failure and it is provided through a S-N curve (Wöhler curve). The fatigue property is dependant on the frequency of increasing temperature and various stresses ranges as shown in Figure 2-16.

In general, there are methods for evaluating the fatigue characteristic of plastics

(1)Load control method (Load control)

(2)Strain control method (Strain control)

(3)Strain control between grips method

(Position control)

	1 < R <	R 0	0 R 1
	0 max min	max 0 min	max min 0
	1	2	3
0
			t
	max = 0	max 0	min = 0

1.	Range of compression stress	3. Range of tensile stress
2.	Range of alternating stress	R : min/ max

Figure 2-16. Stress range of fatigue test

R: 0.1

Freq.: 9Hz

0

Figure 2-17 Wöhler curve of KEPITAL FG2025

Figure 2-18 shows the results of fatigue properties of KEPITAL evaluated based on the strain control method.

R: 0

Freq.: 1Hz

0

Figure 2-18. Fatigue properties based on the strain control method for unfilled grades

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3. Thermal properties

Thermal properties are important elements for establishing the processing conditions of a plastic material and service temperature of a finish part. It is important to preview all possible thermal properties; melting point, heat deflection temperature, coefficient of linear thermal expansion, thermal conductivity and long-term heat ageing resistance, prior to design.

3-1. Melting point (Melting temperature, Tm)

Thermoplastic materials are classified into amorphous and semi-crystalline polymers.

The later has both a crystalline region and an amorphous region in the final product. The melting point is the temperature at which the crystalline region melts with significant volume expansion. At the temperature of a melting point or higher, the plastic becomes molten and starts to flow to be processed. The melting point (ISO

3146) is useful information to set up processing temperatures and also determine the temperature at which it exists in a solid state.

KEPITAL has excellent strength and modulus due to its relatively high crystalinity (65 %) in the final product.

(cf. the crystallinity depends on process conditions)

Type	Tm (°C)
PP	165
POM copolymer	165
POM homopolymer	175
PA6	220

Table 3-1. Melting points of thermoplastics

3-2. Specific heat

Specific heat refers to the calories required to raise the temperature of a unit mass of material by one degree. For KEPITAL, it increases gradually from an ambient temperature up to 150 °C, and then drastically increases at its melting point. At temperatures exceeding the melting point, the specific heat in a molten state is exhibited. The specific heat of KEPITAL is 0.35 kcal/kg · K in the solid state at an ambient temperature and 0.63 kcal/kg · K in the molten phase.

3-3. Heat deflection temperature

The heat deflection temperature (ISO 75) is the temperature at which specimen exhibits flexural deflection of

0.25 mm under a prescribed load and is used for evalu ating relative heat resistance for a service temperature.

3-4. Coefficient of linear thermal expansion

(CLTE)

A plastic expands when temperature increases. If a material is used in a broad range of temperatures or if both plastic and metal parts are either assembled or

molded together, the CLTE is very important in determining tolerance, interference, dimensional changes and in forecasting parts failure.

The changes in the flow direction for KEPITAL F20-03 and FG2025 are shown in Figure 3-1. The CLTE of F20-

03 is higher than that of FG2025 since the glass fiber in FG2025 is aligned to the flow direction while injection processed, The CLTE in the parallel to flow direction is lower than that in the perpendicular to flow direction.

NL/L (µm/mm)

Temperature (°C)

Figure 3-1. Length changes of KEPITAL F20-03 and FG2025

10-5/°C)

Linear expansion coefficient (X

Temperature (°C)

Figure 3-2. Linear expansion coefficients of KEPITAL (perpendicular to flow direction)

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The linear expansion coefficients of KEPITAL in temperature range are shown in Figure 3-2.

CLTE of F10 to F30 in standard unfilled grades are very close, so influence of molecular weight is not expected to be considerable.

3-5. Thermal conductivity

Unlike metals, most thermoplastic materials are insulators with a low thermal conductivity.

The thermal conductivity of KEPITAL standard unfilled grades is 0.31 W/m · K in its solid state.

3-6. Heat ageing

The heat resistance of a plastic may be obtained from measurement of melting point, heat deflection temperature and linear expansion coefficient. The service temperature of plastics should be determined from long-term heat ageing experiments. When a plastic is continuously exposed to evaluated temperature, the mechanical properties gradually deteriorate. Since the degree of property deterioration depends upon environmental factors such as temperature, stress, and time, it is necessary to select a KEPITAL grade upon the designated environmental condition.

Figure 3-3 shows retention rates of tensile strength of KEPITAL F20-03 compared with its initial tensile strength in the air for a long period time. The long-term thermal property of F20-03 is stable up to 100 °C.

	(%)			150	°C
				100	°C
		50			°C
	Retention rate of tensile strength

Storage time (days)

Figure 3-3. Heat ageing resistance of KEPITAL F20-03

Another method for determining the long-term heat resistance of a plastic is RTI (Relative Temperature Index) of the UL 746B Standard. The value shown on a UL card indicates the temperature at which at least 50 % of initial property values are maintained after 100,000 continuous hours. Table 3-2 lists RTI for the electrical properties, impact strength and mechanical strength of KEPITAL F20-03 and FG2025.

	Grade	Electrical	With impact	Without impact
			strength	mechanical strength
	F20-03	110 °C	95 °C	100 °C
	FG2025	105 °C	90 °C	95 °C

Table 3-2. RTI of KEPITAL F20-03 and FG2025

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4. Tribological properties

Tribological properties are highly affected by driving conditions such as pressure on the contacted surface, velocity, temperature, surface roughness etc. The demand for longer lifetime and cost-effective products has recently increased; it has brought up the importance and interest in friction and wear characteristics, especially for self-lubricated products.

Standard unfilled KEPITAL has widely been used in sliding parts because of its inherent lubricity. Moreover, versatile KEPITAL anti-friction & wear grades have been developed for more finely turned applications requiring severe wear condition.

Grade

Description

TS-25H Silicone modified

FL2020 PTFE modified

TX-31 Special lubricant package formulated

Table 4-1. Key point to lubricated KEPITAL

4-1. Friction

Friction is the resistance to sliding of two paired surfaces and is divided by dynamical friction coefficient or static friction coefficient. In general the friction force causes

a surface temperature increases at high velocity and a squeak noise under a certain pressure.

	coefficientfrictionDynamic	Resin to Resin
		Speed: 100 mm/s

Load (N)

Dynamic friction coefficient	Resin to Metal (S45C)
	Speed: 500 mm/s
90	110	130	150

Load (N)

Figure 4-1. Dynamic friction coefficients of KEPITAL

Materials that have the low friction coefficient to particular running conditions are usually effective for good tribological behavior. TS-25H shows extremely low friction properties in sliding against itself even under high pressure in Figure 4-1.

4-2. Wear

The wear occurs from mechanism motions such as abrasion, adhesion and fatigue etc among two or more sliding materials. Specific wear rate is useful to forecast

KEPITAL’s longevity along with its performance in designated sliding condition.

	2.0	Resin to Metal (S45C)
3/N·Km)
		Speed: 500 mm/s
	1.5
rate (mm	1.0
wear
Specific	0.5
	0
	90	110	130	150

Load (N)

Figure 4-2. Specific wear rate of KEPITAL

Significant reduction in wear rate of KEPITAL FL2020 to standard unfilled grade is shown in Figure 4-2.

4-3. PV limits

In terms of frictional behavior, if pressure and speed gradually increase, at a certain point a material cannot withstand any further and start to molten. The maximum value where operation is still possible is called the PV limit. A material with a high PV limit illustrates that it can be utilized under more severe operating conditions.

	5.0	Resin to Resin
(MPa)	4.5
	4.0
pressure	3.5
	3.0
	2.5
Surface	2.0
	1.5
	1.0
	0.5
	00	100	200	300	400	500			600
				Speed (mm/s)

Figure 4-3. PV limits of KEPITAL

Higher PV limit of TS-25H than standard unfilled grade of

F20-03 and other lubricated grades is shown in Figure 4-3.

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5. Electrical properties

KEPITAL has good electrical insulating properties and dielectric strength. Moreover, with recent development in electrical applications, requirements on static dissipative or conductive materials are expanding since the combination of mechanical property and electrical property of KEPITAL is attractive to the electrical markets. KEPITAL provides the broad range of specialties to satisfy those needs.

5-1. Surface Resistivity

Surface resistivity (ASTM D257) is insulation resistance when certain voltage is applied across the surface of material. In general, it is a most widely used characteristic to identify the electrical behavior of plastics. The electrical properties of KEPITAL are shown based on the surface resistivity in Table 5-1.

	102~105	106~109/1010~1012	Higher 1014
	Conductive	Static dissipative/	Insulator
		Anti-static
	ET-20A	ED-10	F20-03 etc.
	FA-20	ES-20

Table 5-1. Surface resistivity of KEPITAL (unit: Ω)

In particular, KEPITAL ET-20A is designed for fuel delivery systems in passenger cars to have stable electrical conductivity and significant resistance in contact with fuels.

KEPITAL FA-20 is reinforced to have high rigidity with electrical conductivity as to meet requirement for high mechanical strength and low tendency to creep.

5-2. Volume Resistivity

Volume resistivity refers to the electrical resistance of a material that is measured when an electric field is applied across the unit cube of a test specimen. Volume resistivity (ASTM D257) is the resistance measured based on the internal current of a material alone, and it may be used to determine its applicability as an insulator.

5-3. Dielectric Strength

When a voltage is applied to an insulator and incrementally increased, if a certain limit is exceeded, large current suddenly flows to break down its insulation, and the limiting value of such voltage is referred to as dielectric strength. Dielectric strength measurement (ASTM D149) of plastic is determined by dividing the voltage with a specimen thickness that incurs current when a test specimen prepared by injection molding is placed between two electrodes, and a voltage is incrementally increased from 0.

5-4. Dielectric Constant

If an insulator is inserted in an electric field, electric charges in the insulator are separated into opposite electric charge directions of the electric field. Dielectric constant (ASTM D150) represents the extent of separation between positive charges and negative charges that are induced at this time.

5-5. Arc Resistance

Arc resistance (ASTM D495) represents the time taken for insulation characteristics to be broken down by

the current applied to the surface of an insulator. Arc resistance may sometimes be influenced by moisture, dust, etc. that is on the surface of the sample.

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6. Resistance to fuels and chemicals

A thermoplastic material may show the changes in mechanical properties and dimensions in environments in contact with specific chemicals. Temperature and soaking time have an influence on those properties.

KEPITAL displays the outstanding resistance to fuels and a variety of neutral organic and inorganic chemicals.

6-1. Fuel resistance

Retention rate (%)

Immersion time (h)

Figure 6-1. Changes of KEPITAL F20-03 in tensile strength

Retention rate (%)

Immersion time (h)

Figure 6-2. Changes of KEPITAL F20-03 in weight

Automotive fuels in gasoline and diesel diversify their compositions upon regions and OEM’s specification. To promote consistent tests with respect to differences in composition, testing fuels have been selected and used.

KEPITAL F20-03 has distinctive resistance with respect to various testing fuels, including gasoline and diesel. The test results of F20-03 to gasoline and diesel are shown in Figures 6-1 and 6-2.

KEPITAL has the good stability in terms of mechanical properties and dimensions in contact with fuels even at evaluated temperature. Therefore, KEPITAL has been used in various automotive fuel applications.

6-2. Chemical resistance

KEPITAL exhibits good resistance to the following chemicals;

·Organic solvents: Alcohols, Esters, Ketones, Aliphatic and Aromatic hydrocarbons

·Automotive fluids: Washer fluid, Oils and Coolant etc.

However, strong acids, oxidizing agents and halogens are strongly recommended to be kept away from KEPITAL since those break up the chemical structure of KEPITAL. The changes in physical properties to various chemicals are illustrated in Table 6-1.

		Immer-	Tempe-	Measurements
				Retention rate (%)
	Chemical	sion	rature
		time (h)	(°C)	Tensile	Weight	Length
				strength
	Fuel C	360	60	95	102	102
	SME20	5,040	90	93	100	100
	Iso-octane	19,680	23	97	100,1	100,2
	Gasoline	1,000	65	92	101	100
	Diesel	1,000	90	100	100	100
	Methanol	8,760	50	88	102	101
	Ethanol	8,760	50	89	102	101
	Acetone	8,760	23	83	104	102
	Toluene	8,760	50	90	103	102
	Benzene	6,600	60	90	104	102
	Carbon tetrachloride	8,760	23	98	102	100
	Ethylene glycol	480	120	89	–	–
	(100%)
	Acetic acid 1%	8,760	23	101	100	100
	Sulfuric acid 1%	4,320	23	100	100	100
	Hydrochlorid acid 10%	960	40	100	99	100
	Sodium hydroxide	552	23	102	100	100
	10%
	Sodium hypochlorite
	(Effective chlorine	552	23	100	100	–
	3 ppm)
	One-Luber No. 2	2,400	100	105	100	100
	Dow Corning FS-	2,400	100	106	100	100
	44MA
	Cosmo Limax No. 2	2,880	120	101	99	99
	Cutting fluid Yushiro	552	23	100	100	100
	EE56
	Silicon oil	3,120	130	106	100	99
	Food grade salad oil	1,920	80	104	–	–
	Copy diazo develop-	552	23	96	–	–
	ment solution SD
	Photographic develop-	1,200	50	101	102	101
	ment solution
	Photographic fixing	960	40	101	100	100
	solution
	Hot water	1,000	85	103	100	100
	Anti-freeze	5,000	23	103	–	–
	Engine oil	5,000	23	105	–	–
	Gear oil	5,000	23	103	–	–

Please consider to make practical tests with application under real circumstances to make sure that part will last for a certain period without failure as the above result will change by testing conditions, temperature, the concentrate of chemical and immersing period etc. and unexpected effects.

Table 6-1. Chemical resistance of KEPITAL after immersion in various chemicals

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7. Resistance to light and weather

With exposure to sunlight, plastics become very sensitive to ultraviolet rays. The UV causes discoloration and surface chalking resulting in decomposition, and finally serious deterioration of mechanical properties.

KEPITAL UV-stabilized formulations can prolong the service life of applications with specially formulated UV-packages. Resistance to light and weather is usually evaluated through accelerated weathering tests and outdoor exposures for specific times. In general OEM specification recommends the outdoor testing be conducted by means of weather-o-meter or outdoor exposure in

Florida and Arizona.

Weather	Florida	Arizona
Rate of annual sunny days	69 %	85 %
Annual UV radiation (385 nm)	280 MJ/m2	334 MJ/m2
Annual sunlight radiation	6588 MJ/m2	8004 MJ/m2
Average temperature in summer	32 °C	40 °C
Annual raining days	111	32

Table 7-1. Outdoor exposure test environment

The accelerated weathering equipment can have three light sources such as carbon arc, xenon lamp, and UV lamp. Recently, the xenon lamp, with a spectrum similar to that of sunlight, is generally used. Radiation intensity and other conditions; filter combinations, temperature, cycle configuration, are specifically set up according to the test method.

The SAE (Society of Automotive Engineers) standards prescribe that different conditions which reflect the outdoor environment be applied to the accelerated weathering test depending upon the interior or exterior application. For interior applications, the cyclic conditions take day and night into account, while for the exterior applications, the water shower has been taken to simulate raining. For light resistance and weather resistance of plastics, changes in colorfastness, surface gloss or mechanical properties are measured after exposure to outdoor or accelerated weathering.

7-1. Light resistance grade

KEPITAL Fxx-52 and Fxx-52G are products with light resistance and are intended for interior applications. In addition to natural colors, they are processed with various colors.

The color changes of F20-52 in beige, gray and red are less than that of F20-52 in natural color after accel-

erated weathering according to SAE J2412 in Figure 7-1.

Exposure time (h)

Figure 7-1. Color changes of F20-52 and F30-52

7-2. Weather resistance grade

KEPITAL Fxx-51 and Fxx-51U are products in black with UV-stabilization and were developed for exterior applications.

The weather resistance of F20-51U in colorfastness was measured according to accelerated weathering SAE J2527 in Figure 7-2.

Exposure time (h)

7-2. Color changes of F20-51U

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