1. About NOVADURAN
1.1 Features of NOVADURAN
NOVADURAN® is a name of a polybutylene terephthalate (PBT) resin made and sold by Mitsubishi
Engineering Plastics. PBT resin is a polyester resin that can be attained by polycondensing terephthalic acid
(TPA) or dimethylterephthalate (DMT) with 1,4-Butanediol (1,4-BG), and have following characteristics.
（1） Good mechanical property
（2） Good heat resistance
（3） Good moldability with fast crystallization speed and good liquidity
（4） Good dimension stability with small water absorption rate
（5） Good staining property with good surface gloss
（6） Good oil resistance and solvent resistance which hardly get affected by chemicals
（7） Good electrical property
（8） Good frictional and wear property
（9） Able to provide good flame resisting grade
There are variety of grade for NOVADURAN, such as unreinforced, GF reinforced, flame resisting grade, low
gas type, hydrolysis resistant type, and low warpage type, so choosing an appropriate grade depending on usage
is possible. Table 1-1 is a list of NOVADURAN major grade lineup.
Category
Feature
Grade Name
Unreinforced
Standard
High cycle
Tough
Flexible （copolymerization）
5010R3，5010R5，5010R5L
5010CR2
5010TRXA，5010TRX5
5010R8S，5010R8M，5010R8L
Unreinforced
High toughness （V-2）
Flame resisting （V-0）
Non bromine flame resistant
5010N5
5010N6-3X
SEF-500
Standard
Hydrolysis resistant
Tough
Heat shock resistant
Low warpage
Voltage resistant
Tracking resistant
5010G15，5010G30，5010G45
5010G30X4
5010GT15，5010GT30
5010GT15X，5010G30TZ
5010F6X4
5010FMT30
5010GP20
Standard
Low gas emission
Tough
Tracking resistant
Low warpage
Glow-wire resistant
Non bromine flame resistant
5010GN1-15AM，5010GN1-30AM
5010GN6-15M8AM，5010GN6-30M8AM
5010GN6-15TM4，5010GN6-30TM4
5010GPN33
5010FN2-M9
5830GN6-40
SEF-515，SEF-530
Good appearance
Super glossy
Low warpage, good appearance
Super low warpage, good appearance
Low warpage, low specific gravity
Low warpage, flame resistant
5308G30
5308F20
5710G30S2
5710F40
5810G30，5820G30H
5810GN6-30
flame resisting
GF reinforced
GF reinforced
flame resisting
Alloy
Table 1-1 Major grade line up of NOVADURAN
－ 1 －
2. Physical PROPERTY
2.1 Molecular weight and melting viscosity
Molecular weight of polymeric molecule generally has a certain distribution, so normally get represented by its
average molecular weight. There are several types of molecular weight from how it is measured.
（1） Number average molecular weight （Mn）
： Osmotic measurement, end group determination method
（2） Weight-average molecular weight （Mw）
： Light scattering method, ultracentrifugation method
（3） Viscosity average molecular weight （Mv） ： Viscosity method
Relation between each average molecular weight will generally be Mn＜Mv＜Mw.
Average molecular weight measurement of PBT is often done by the viscosity method. About melting viscosity,
relation of intrinsic viscosity [η] and molecular weight M is [η] ＝ K・Mα, and PBT average molecular weight
can
be
calculated
by
measuring
the
melting
viscosity.
For
instance,
melting
viscosity
of
phenol/tetrachloroethane (1/1) under 30℃ inside the solvent, the value K＝4.3×10-4、α＝0.76 has been
reported.
2.2 Specific weight and crystalline
Specific weight of PBT will differ by crystalline phase and amorphous phase, and several values are being
reported. Followings are the typical value.
Specific weight of crystalline phase
1.40 g/cm3
Specific weight of amorphous phase
1.28 g/cm3
Specific weight of standard molded product
1.31 g/cm3
Specific weight of the molded product will differ by its crystallinity, but crystallinity of PBT is almost within 15
to 30%. Specific weight of a general injection-molded product is about 1.31g/cm3, and in this case, crystallinity
will be 28%. Crystallinity will get affected by the molding condition, so if high-cycle molded under low mold
temperature, crystallinity will drop because it get cooled rapidly, and conversely, if cooled slowly, crystallinity
will rise. Also, if annealed by high temperature after molding, recrystallization will make progress and crystallinity
will rise.
2.3 Melting viscosity
PBT has relatively good liquidity when molding. Viscosity or liquidity of PBT under a molten state will change
depending on flow velocity (shear velocity) and pressure (shear stress). Melting viscosity can be measured using
a capillary rheometer. Viscosity curve (flow curve) can be attained from this measurement method by measuring
a stress in a particular flow velocity (shear velocity) and changing the shear velocity and temperature. Typical
flow curve of NOVADURAN will be as the following (Figure 2-1, Figure 2-2).
－ 2 －
Figure 2-1 Flow curve of 5010R5
Figure 2-2 Flow curve of 5010G30
2.4 Water, moisture absorption rate
PBT is a resin with very low water absorption rate, and its equilibrium water absorption rate in the atmosphere
is about 0.2%. However, if exposed under a high temperature when absorbing the water, physicality will drop
because the molecular weight decreases by hydrolytic degradation, so require drying before molding until the
moisture amount becomes less than 0.02%. In the case of functional component, drying until the moisture amount
becomes less than 0.01% is preferred.
Figure 2-3 indicates water absorption curve of NOVADURAN, and Figure 2-4 indicates double logarithmic
plot of them. If double logarithmic plot the water absorption rate and immersion time, relation of almost straight
line can be seen. Figure 2-5 and Figure 2-6 indicate water absorption curve under each condition, and relation
of water absorption rate and dimension change. NOVADURAN's water absorption rate is quite small, and
dimension change by water absorption is also very low. Following indicates the comparison of water absorption
rate between other resins. But, this water absorption rate measuring method does not always set water
absorption rate zero as a basis, so if measured by Karl Fischer Method, the value might be bigger than the
following one.
Resin
Water absorption rate （%）
PP
< 0.01
PE
0.01～0.08
PS
0.03～0.04
ABS
0.2
PMMA
0.2～0.4
PBT
0.1
PA
1.5～2.3
POM
0.4
PC
0.2
m-PPE
< 0.1
－ 3 －
Figure 2-3 Water absorption curve of each grade
Figure 2-4 Water absorption curve of each grade
（double logarithmic plot)
Figure 2-5 Water absorption rate in each condition Figure 2-6 Water absorption rate and dimension change
－ 4 －
3. Mechanical PROPERTY
3.1 Tensile strength
Tensile strength is the most basic and important property in the mechanical property. In stress-strain curve
attained from tensile test, different curve can be seen if the deformation pattern changes by the material.
Figure 3-1 shows typical tensile stress-strain curve of reinforced PBT. Strain until the destruction is relatively
small, and indicates a form of brittle fracture that stands up linearly and just fracture. On the other hand, Figure
3-2 shows typical tensile stress-strain curve of unreinforced PBT. Strain until the destruction is relatively big,
and indicates a form of ductile fracture. Area reduction will occur by the localized necking phenomenon after
passing the yield point, but the stress will rise again after the propagation of constriction is done, and end up with
brittle fracture. Tensile strength can be calculated by the formula below.
Tensile stress σ＝ P／A
P ： Destruction or yield load
A ： Cross-section area of specimen
Figure 3-1 Example of reinforced PBT's tensile
Figure 3-2 Example of unreinforced PBT's tensile
stress-strain curve
stress-strain curve
There is a temperature dependency on the tensile strength. Strain tend to increase (become softer) under a
high temperature because the strength will degrade, and conversely, strength will improve under a low
temperature and strain tend to decrease (become harder). Tensile stress-strain curve of NOVADURAN typical
grade is indicated in Figure 3-3 to Figure 3-5, and Figure 3-6 indicates their tensile property and temperature
dependency.
The weld part often get generated in a general molded product and the strength there will sometimes degrade.
Figure 3-7 indicates the temperature dependency of PBT weld strength. Generally, in the case of GF reinforced
PBT, strength will degrade by the disarray of GF orientation. Strength degradation will be smaller in unreinforced
PBT, but if the pressure on the weld part is not enough because of the molding condition or shape, the weld
strength might degrade.
Also, resin flow direction and anisotropy will make a difference in strength. Anisotropy ratio of transverse
－ 5 －
direction and machine direction is smaller than 100%, and transverse direction strength tend to be smaller.
Anisotropy ratio in unreinforced PBT will be almost 100%, but talking about GF reinforced PBT, there is an
anisotropy on GF reinforcing effect, so anisotropy ratio of GF 15% reinforced grade is about 75%, and 50% for GF
30% reinforced grade (Figure 3-8).
Actual product have to be designed caring about the strength degradation by the weld part and flow
orientation effect as stated above.
Figure 3-3 Tensile stress-strain curve of
Figure 3-4 Tensile stress-strain curve of
5010R5
5010G30
－ 6 －
Figure 3-5
Tensile stress-strain curve of
5010G15
Figure 3-6 Temperature dependency of tensile
strength
－ 7 －
(MPa)
(MPa)
Figure 3-7 Temperature dependency of weld strength
Figure 3-8 Anisotropy of strength and elastic modulus
3.2 Flexural strength
There are two ways to test flexural strength. One is three-point bending test, and the other one is four-point
bending test, but measuring by three-point bending test is general. Flexural strength will be calculated by the
following formula if the flexure is small.
Flexural stress σ＝
3・P・L
2・b・h
2
P ： Maximum load，
L ： Fulcrum distance
b ： Specimen width，
h ： Specimen thickness
Flexural stress-strain curve of PBT tend to be similar to the tensile test case, but the localized necking
phenomenon cannot be seen in the flexural case. Like the tensile property, flexural property also has a
temperature dependency. Furthermore, flexural modulus can be calculated from a gradient of initial straight
portion in flexural stress-strain curve, and used as a barometer of the material stiffness. Flexural stress-strain
curves of NOVADURAN typical grade are indicated in Figure 3-9 to Figure 3-11, and temperature dependency
of flexural property is indicated in Figure 3-12 and Figure 3-13.
3.3 Compressive strength
Load direction of compression is the opposite to the tension, so compressive strength can be calculated by the
following formula like the tension case. Temperature dependency of compressive strength is indicated in Figure
3-14.
Compressive stress σ＝ P／A
P ： Destruction or yield load
A ： Cross-section area of specimen
3.4 Shear strength
Force that punch and cut off the molded product is called shear force. Measurement of the shear strength is
done by punching out the circular plate from the center of the flat plate specimen. Shear strength can be
－ 8 －
calculated by the following formula. Figure 3-15 indicates temperature dependency of shear strength.
Shear stress σ＝
P
π・D・h
P ： Maximum load
D ： Diameter of punch circular plate
h ： Specimen thickness
In addition, relation of shear elastic modulus (modulus of rigidity) G and tensile elastic modulus (modulus of
longitudinal elasticity) E will be shown as below using a Poisson ratio (0.35 to 0.40 in PBT case)
G ＝
E
2（1＋ν）
3.5 Impact strength
Impact strength shows material strength in fast deformation. Compared to the metal case, impact resistance
often becomes a problem in the plastic case. The followings are some typical impact testing method, but normally,
measured value of Izod impact test or Charpy impact test is used as a reference.
（1） Impact test by pendulum motion energy
： Izod impact test, Charphy impact test
（2） Impact test by falling body motion energy ： Weight-drop impact test, falling ball impact test
（3） Impact test by fast deformation
： Tensile impact test
If there is a sharp corner such as a notch on the molded product, the stress will concentrate when it receives
an impact, and tend to cause destruction. Generally, dependency (notch sensitivity) on a notch angle and
roundness on the corner part can be seen on the impact strength, so making the corner part is important to
strengthen the impact resistance of the molded product. Figure 3-16 and Figure 3-17 indicates the temperature
and notch roundness dependency of PBT's impact strength.
－ 9 －
Figure 3-9 Flexural stress-strain curve of 5010R5
Figure 3-11 Flexural stress-strain curve of 5010G15
Figure 3-10 Flexural stress-strain curve of 5010G30
Figure 3-12 Temperature dependency of flexural strength
－ 10 －
Figure 3-14 Temperature dependency of compressive
strength
Figure 3-13 Temperature dependency of flexural modulus
Figure 3-16 Temperature dependency of impact strength
Figure 3-15 Temperature dependency of shear strength
Figure 3-17 Notch roundness dependency of impact
strength
3.6 Effect of GF contained amount against strength
Strength and heat resistance of PBT will considerably rise by GF reinforcement. Strength will rise as the GF
content increases, but if it get too much, progress in strength will slow down. On the other hand, elastic modulus
will rise almost as much as the GF amount increases. The deflection temperature under load, which is a
barometer of the heat resistance, will rise drastically as the GF amount increases, and in more than GF15%, high
level is kept. Figure 3-18 to Figure 3-21 indicate static strength and impact strength, elastic modulus, and GF
－ 11 －
content dependency of deflection temperature under load.
Figure 3-18 GF content dependency of static strength
Figure 3-19 GF content dependency of impact strength
Figure 3-20 GF content dependency of elastic
Figure 3-21 GF content dependency of deflection
modulus
temperature under load
3.7 Fatigue endurance property
Fatigue degradation will occur on the part where gets loaded repetitively, so destruction might happen even if
the stress is below fracture stress of resin. Part design that get repetitively loaded will need to consider the
fatigue strength. Figure 3-22 and Figure 3-23 indicate Fatigue property of NOVADURAN. Putting the stress
loading of both tension and compression will progress the fatigue degradation than putting the stress loading of
tension or compression. If the both stress loadings are put, destruction will occur by putting only half stress of
the static destruction stress.
－ 12 －
Figure 3-22 Flexural fatigue property
Figure 3-23 Temperature dependency of
flexural fatigue property
3.8 Creep property
If the product is left for long time putting the stress on, gradually the creep deformation will occur. The long
stress loaded time might cause destruction, even if it is below the fracture stress of the resin. Require a special
attention if the part is designed to be steady loaded, because it might cause deformation and destruction by
creep.
Figure 3-24 and Figure 3-25 indicate flexural creep strain property of unreinforced PBT （5010R5） and GF
reinforced PBT （5010G30）. The amount of creep strain will differ by the stress and temperature, but if the
temperature and stress is relatively low, strain amount will almost be proportional to the stress, so can be shown
by using creep elastic modulus (Figure 3-26, Figure 3-27), and calculating the strain amount in any stress is
possible.
Appearance creep elastic modulus＝
Stress
Creep strain
If the temperature or stress is extremely high, phenomenon that end up with destruction by a rapid strain
occurrence (acceleration creep) will happen, so be careful. Figure 3-28 and 3-29 indicate the creep destruction
curve of tensile creep in unreinforced PBT （5010R5） and GF reinforced PBT （5010G30）. Calculation by the
creep elastic modulus shown above is only possible if the load stress is less than half of the creep destruction
stress.
Creep property depends extensively on material elastic modulus, so if the GF amount increases, the creep
strain will be smaller. Figure 3-30 indicates GF amount dependency of creep strain.
－ 13 －
Figure 3-24 Flexural creep strain property of 5010R5
Figure 3-25 Flexural creep strain property of
5010G30
Figure 3-26 Flexural creep modulus of 5010R5
Figure 3-27 Flexural creep modulus of 5010G30
Figure 3-28 Tensile creep fracture property of 5010R5 Figure 3-29 Tensile creep fracture property of 5010G30
－ 14 －
Figure 3-30 GF amount dependency of flexural creep property
3.9 Stress relaxation
The strain will occur on the product if a certain stress is put, but if that strain amount is kept for long time,
internal stress will be relaxed by the creep property of the material. This property is called stress relaxation
property. Figure 3-31 and Figure 3-32 indicate tensile stress relaxation property of unreinforced PBT
（5010R5） and GF reinforced PBT（5010G30）
Figure 3-31 Stress relaxation curve of 5010R5
Figure 3-32 Stress relaxation curve of 5010G30
3.10 Friction and abrasion resistant property
To evaluate the sliding property, there are several methods to suit each sliding form such as the Taber
abrasion, thrust sliding, pin-plate sliding, but here indicates the result of PBT sliding property (Table 3-1 to
Table 3-3) by the thrust sliding test. In the thrust sliding test, a ring shaped resin molded product like indicated
in Figure 3-33 is used, and evaluate sliding property by rotating the part while the other part is held under a face
pressure. Representative items that shows sliding property is written below.
（1） Coefficient of kinetic friction
： Shows the size of the frictional drag that occurs when sliding.
（2） Specific wear rate
： Shows the sliding abrasion quantity under a certain condition.
－ 15 －
Value which is normalized by face pressure and sliding distance is used, and also called wear coefficient.
（3） PV limit value ： Shows the sliding limit that makes the test stop because the molded product get molten
by the sliding friction heat under a condition of face pressure P and linear velocity V.
PBT coefficient of kinetic friction will be about 0.1 to 0.4. Wear volume tend to be smaller against different
resin (such as POM) than the same resin (PBT and PBT), so selecting a different resin is preferred if the
conditions of the sliding parts are strict. Wear volume tend to be bigger in GF reinforced PBT than unreinforced
PBT if against metal sliding. On the other hand, sliding limit (PV limit value) will be higher than against resin
because of the good radiation performance.
Table 3-1 Coefficient of kinetic friction
Table 3-2 Specific wear rate (mm3/kg・km) ： implemented 20hrs
Table 3-3 PV limit value （MPa・m/s）
φ26mm
※ General-purpose POM ： Iupital F20-03
φ20mm
※ The values in Table 3-1 to Table 3-3 are the result
15mm
examples by the written specimen, and the actual value might
differ by the molded product shape and surface situation.
Sliding face
Rotation axis
Figure 3-33 Thrust sliding test method
－ 16 －
4. Thermal PROPERTY
4.1 Melting point, crystallization temperature, glass-transition point
Generally, the melting point of PBT (Tm) is often calculated from the location of the melting endothermic peak,
measured by differential scanning calorimeter (DSC) and the melting point will be about 224℃.
Similarly, the crystallization temperature of PBT （Tc） is often calculated from the peak location of the
crystallization heat generation, measured by DSC. Tc will also differ by the grade, and basically about 170℃ to
175℃ in base resin case, 185℃ to 195℃ in compound product case. Tc value is thought as a indication of the
crystallization speed, and generally, crystallization will start from high temperature as the Tc value gets high, so
crystallization speed will be faster. PBT is a resin with relatively fast crystallization speed, and suitable for high
cycle molding. DSC is also used in measuring the crystallization speed, and the result of half crystallizing time
measurement using DSC showed that crystallization is fast next to the polyacetal (POM).
Glass-transition point of PBT (Tg) differs by the measurement method, and value of 37℃ to 53℃ has been
reported.
4.2 Melting heat, specific heat, thermal conductivity
Melting heat and crystallization heat of PBT that can be calculated by DSC measurement will be about 50 J/g.
In the case of compound product, the value tend to be smaller because of the effect of GF and the other
component addition, and if GF 30% reinforced PBT, the value will be 35 J/g.
Specific heat can also be calculated by the DSC measurement. Specific heat will change by the temperature
(Figure 4-1) but PBT specific heat in operating temperature range will be about 1.2 J/（g・℃）. This value has no
big difference to general synthetic resin, and is nearly equivalent to three times of the typical metal (iron, copper,
aluminum). Furthermore, The value of the specific heat will slightly decrease if the crystallinity becomes higher.
Thermal conductivity of PBT within the operating temperature range is about 22 W/（m・K）, and it will be
about 0.29 W/（m・K） in the case of GF reinforced PBT. This value also has no big difference to general
synthetic resin, but is about several hundredth or thousandth part of typical metal, which is very small compared
to the metal.
－ 17 －
Figure 4-1 Temperature dependency of specific heat （5010R5）
4.3 Coefficient of thermal expansion, PVT curve
Coefficient of thermal expansion of PBT slightly has a temperature dependency, but only about 1.1×10-4
（1/℃） in 23℃. This value is five to ten times bigger, compared to the typical metal. Linear expansion
coefficient will be smaller in GF reinforced PBT, and anisotropy will get generated by the flow orientation, so
linear expansion coefficient of machine direction will be close to the value of the metal. Figure 4-2 and Figure
4-3 indicate temperature dependency and GF content dependency of linear expansion coefficient. Also, PVT
curve that shows relation of pressure (P), volume (V), and temperature (T) is indicated in Figure 4-4 and Figure
4-5.
Figure 4-2 Temperature dependency of linear
Figure 4-3 GF content dependency of linear
expansion coefficient
expansion coefficient
Figure 4-4 PVT curve of 5010R5
Figure 4-5 PVT curve of 5010G30
－ 18 －
4.4 Heat distortion temperature
The value of deflection temperature under load is often used as a heat distortion temperature which will be a
barometer of heat resistance property. Heat resistance of PBT will drastically improve by GF reinforcing (Figure
4-6). PBT deflection temperature under load will be almost as below.
Unreinforced PBT
Reinforced PBT
(5010R5)
(5010G30)
1.8MPa
54℃
202℃
0.45MPa
136℃
220℃
Stress
Figure 4-6 GF content dependency of deflection temperature under load
4.5 Heat degradation, flammability
If PBT is left in a temperature of higher than melting point, heat degradation will gradually occur. Figure 4-7
indicates the result of molecular weight decrease by heat degradation that occurred by leaving PBT inside the
molding machine cylinder, which is measured by melting viscosity. This turns out that as the temperature rises,
heat degradation tends to progress. Also, from thermogravimetric (TG) analysis, heat degradation starting
temperature will be about 390℃ in nitrogen atmosphere 20℃/min (Figure 4-8).
Figure 4-7 Melting viscosity degradation of
Figure 4-8
5010G30 by retention
thermogravimetric (TG)
－ 19 －
Decreasing curve of PBT
UL94 standard is representative for the scale of resin flame resistance. PBT has HB level flame resistance in
UL94, but V-2 or V-0 level is achieved in the flame resisting grade. As another scale of the flame resistance,
limiting oxygen index (LOI) is sometimes used, and PBT LOI that correspond to each UL standard level will be
the following.
UL standard HB level （unreinforced）
LOI ＝ about 23
UL standard HB level （reinforced）
LOI ＝ about 18 to 19
UL standard V-2 level
LOI ＝ more than 24
UL standard V-0 level
LOI ＝ more than 30
Flammable tetrahydrofuran (THF) is the major element of the gas that generates by PBT heat degradation.
Flash temperature of PBT is more than 300℃, and ignition temperature is more than 400℃.
－ 20 －
5. Electrical PROPERTY
5.1 Dielectric strength
To evaluate the dielectric strength, there are measurements dielectric breakdown strength and withstand
voltage, and the former value will be little higher than the latter. Dielectric breakdown strength of PBT is about
20MV/m, and this is the same level as the other general-purpose engineering plastics. The comparison with
other materials are shown in Figure 5-1. Dielectric strength will improve by containing GF, and its value will be
higher compared to the unreinforced ones. Also, if PBT degrades by hydrolysis, the dielectric breakdown
strength will decrease. Figure 5-4 and Figure 5-5 indicate the value after left in a high temperature, and the
hygrothermal process.
Figure 5-1 Comparison of dielectric breakdown strength in each material
Figure 5-2 Temperature dependency of dielectric
Figure 5-3 Thickness dependency of dielectric
breakdown strength
breakdown strength
－ 21 －
Figure 5-4 Dielectric breakdown strength after left Figure 5-5 Dielectric breakdown strength after
in high temperature
hygrothermal process
5.2 Dielectric resistance
When the voltage is applied by placing two electrodes on the insulation, a current flowing in the insulation will
be the same as the sum of internal current and surface current. The resistance value against the internal current
is called volume resistance, and resistivity against the surface current is called surface resistance. Resistivity of
PBT, the insulation, is high, and volume resistivity in the ambient temperature is about 10-14Ω・m, and surface
resistivity is about 10-15 Ω. Comparison to the other material is indicated in Figure 5-6. Temperature
dependency is also seen in these resistivity （Figure 5-7, Figure 5-8）.
Figure 5-6 Resistivity comparison of each material
－ 22 －
Figure 5-7 Temperature dependency of volume resistivity
Figure 5-8 Temperature dependency of surface resistivity
5.3 Dielectric property
The phenomenon that generates positive and negative electrical charge on the surface of the insulation when a
voltage is applied, is called dielectric polarization. Permittivity （ε） indicates the size of this dielectric
polarization, and relative permittivity is indicated by the ratio of vacuum to permittivity （ε0＝8.854pF/m）.
Tangent of a phase difference （δ） of the late actual current to the applied voltage when the AC voltage is
applied as a voltage, is called dielectric tangent （tanδ）. If high-frequency AC voltage is applied to the
dielectrics, produce a heat as much as a loss of electrical energy (dielectrics) proportional to ε×tanδ, so
insulating material with smaller ε and tanδ is preferred for high voltage and high-frequency device.
Relative permittivity of PBT in the ambient temperature of 1MHz is 3.2, and dielectric tangent is about 0.02.
Comparison to the other materials is indicated in Figure 5-9. Dielectric property also has dependency to the
temperature and the frequency (Figure 5-10 to Figure 5-13）.
Figure 5-9 Permittivity comparison of each material （60～106 Hz）
－ 23 －
Figure 5-10 Temperature dependency of permittivity Figure 5-11 Temperature dependency of dielectric tangent
Figure 5-12 Frequency dependency of permittivity
Figure 5-13 Frequency dependency of dielectric tangent
5.4 Tracking resistance
When contaminated material (water, salt, dust) is attached to the insulator surface, the property that degrades
by the leaked current even if the voltage is relatively low, is called tracking property. Tracking resistance is
important in the insulation with relay case or switching basis. There is IEC method to measure the tracking
property, and get indicated by index such as CTI （Comparative Tracking Index）. UL standard ranks by CTI
value as the following.
CTI ：more than 600V
PLC rank ：0
600～400V
1
400～250V
2
250～175V
3
・
・
・
・
・
・
Non flame resisting grade of PBT has almost same or more quality with PLC1, but flame resisting grade
sometimes worth below PLC3.
－ 24 －
5.5 Arc resistance
If arc discharged on the surface of the plastic, it will degrade by the arc heat and form a conduction by
carbonizing, and the arc will disappear. This arc disappearing time will be the barometer of plastic's arc
resistance. The arc resistance of PBT non flame resisting grade is almost more than 120 sec, but in a flame
resisting grade, sometimes it gets below 120 sec. Table 5-1 indicates comparison of arc resistance to the other
resin.
樹脂
Resin
耐アーク性
Arc
resistance（sec）
(sec)
PP
＞ 140
PE
＞ 130
PS
＞ 130
ABS
93
PMMA
＞ 130
PBT
125
PA6
140
PA66
＞ 140
POM
＞ 240
PC
110
変性PPE
m-PPE
67
Table 5-1 Arc resistance comparison of each resin
5.6 Corona resistance
If the charge concentrates on a part of the conductor, the gas touching that part will cause insulation
breakdown, and local discharge will occur. This is called corona discharge. Oxygen atom, ozone, nitric oxide, and
ion will be generated when the corona discharge happens, so the plastic degradation will accelerate and end up
with insulation breakdown.
Corona resistance is tend to get affected by the dielectric loss, so PBT with glass-transition point (Tg) close
to the ambient temperature which increases the dielectric loss, has no good corona resistance. If using PBT with
the electric part that high voltage AC wave or continuous pulse is applied, require an attention to the
countermeasure against the discharge.
－ 25 －
6. Chemical PROPERTY
6.1 Hygrothermal resistance
PBT sometimes degrade in physicality by the hydrolysis under a high temperature and high humidity
environment, so usage environment must be considered carefully. Especially if the usage environment is severe,
using hydrolysis resistance grade like 5010G30X4 is preferred. Figure 6-1 to Figure 6-4 indicate strength
change of NOVADURAN by hygrothermal process （ 85 ℃ ， 95%RH ） and pressure cooker test （ PCT ）
acceleration procedure （121℃，2atm，100%RH）. PCT process is 15 to 20 times accelerated test compared to
the hygrothermal process above.
Figure 6-1 Strength change after hygrothermal
Figure 6-2 Strength change after pressure
process
cooker process
Figure 6-3 Physicality change after hygrothermal
Figure 6-4 Physicality change after pressure
process
cooker process
6.2 Chemical resistance
PBT has good chemical resistance since it is crystalline resin, and has resistance to almost every organic
solvent and oil. However, it might get affected by strong acid or alkali because it has an ester linkage. Table 6-1
to Table 6-2 indicate typical chemical resistance of NOVADURAN.
－ 26 －
Grade
Chemical name
Immersion
temperature
(℃)
5010R5
Immersion
days
(day)
Immersion
temperature
(%)
Weight
gain rate
(%)
5010G30
Immersion
temperature
(%)
Weight
gain rate
(%)
< Inorganic chemical >
10% hydrochloric acid
23
10% acetic acid
23
10% sulfuric acid
23
23
70
36% sulfuric acid
5% ammonia
23
10%NaOH
23
7
30
7
30
30
30
30
7
30
7
30
96
96
92
91
94
99
92
97
95
94
93
0.2
0.3
0.2
0.4
0.3
0.2
0.3
0.1
0.2
0.2
0.2
95
89
94
89
97
97
84
97
95
34
2
0.1
0.1
0.1
0.1
0.1
0.1
1.1
0.1
0.2
1.6
0.9
7
30
7
30
7
30
7
30
7
30
7
30
7
30
7
30
7
30
7
30
7
30
7
30
7
30
7
30
90
77
61
39
97
98
93
87
100
100
78
70
82
73
85
76
83
73
32
33
98
100
100
100
96
100
100
100
0.7
1.3
6.1
11.3
0.2
0.6
0.5
1.0
0.0
0.1
1.0
1.9
1.5
2.6
0.3
0.6
0.8
1.5
27.4
25.8
0.0
0.0
0.0
0.0
0.1
0.2
0.0
0.0
99
96
80
62
100
98
96
95
100
98
89
86
91
91
92
91
93
90
55
54
98
100
100
100
100
99
100
100
0.3
0.7
2.9
5.2
0.2
0.3
0.2
0.5
0.0
0.1
0.6
1.1
0.7
1.3
0.3
0.5
0.4
0.8
13.4
13.0
0.0
0.0
0.0
0.0
0.1
0.2
0.0
0.0
< Organic chemical >
Ethyl acetate
23
1.2 dichloroethane
23
Tetrachloroethylene
23
Toluene
23
Heptane
23
Acetone
23
Chlorobenzene
23
Methanol
23
Methyl ethyl ketone
23
Methylene chloride
23
1.4 butanediol
23
Ethylene glycol
（antifreeze 100%）
23
Ethylene glycol：Water＝1：1
23
Isopropyl alcohol
23
Table 6-1 Chemical resistance of NOVADURAN （No. 1）
－ 27 －
5010R5
Grade
Chemical name
Immersion
temperature
(℃)
Immersion
days
(day)
Immersion
temperature
(%)
Weight
gain rate
(%)
5010G30
Immersion
temperature
(%)
Weight
gain rate
(%)
< Gasoline/Oil >
Gasoline (leaded)
23
Gasoline (nonleaded)
23
Regula gasoline (nonleaded)
60
High-octane gasoline (nonleaded)
60
Regular gasoline： Methanol
＝85：15
60
Regular gasoline： Ethanol
＝80：20
60
23
Transmission fluid
120
150
23
Power steering fluid
70
150
23
Brake fluid
70
Motor oil (Shell)
Silicon oil
(Toray silicon SH200)
Aqueous cutting oil
(Kyoseki soul cut W-11)
23
23
70
23
70
7
30
7
30
7
30
7
30
7
30
7
30
7
30
7
30
7
30
7
30
7
30
7
30
7
30
7
30
30
7
30
7
30
7
30
7
30
100
100
100
100
－
－
－
－
－
－
－
－
100
100
100
100
100
99
99
100
96
99
100
52
100
100
92
87
100
100
100
100
100
100
100
100
100
Table 6-2 Chemical resistance of NOVADURAN （No. 2）
－ 28 －
0.0
0.0
0.0
0.1
－
－
－
－
－
－
－
－
0.0
0.0
0.4
0.7
0.9
1.2
0.0
0.0
0.0
0.0
0.6
0.8
0.0
0.0
0.3
0.6
0.0
0.1
0.1
0.0
0.0
0.0
0.0
0.2
0.2
100
100
100
100
89
81
89
81
72
57
80
66
100
100
100
100
100
75
100
100
96
99
100
64
100
100
100
100
100
100
100
100
100
100
100
100
100
0.0
0.0
0.0
0.1
0.6
1.1
0.4
1.0
1.9
3.3
1.1
2.5
0.0
0.1
0.3
0.6
0.6
0.8
0.0
0.0
0.0
0.4
0.4
0.7
0.0
0.0
0.2
0.4
0.1
0.1
0.0
0.0
0.0
0.0
0.0
0.1
0.2
7. Optical PROPERTY
7.1 Light transmittance
Injection-molded product of PBT is basically opaque because it is a crystalline resin, but if the film is very thin,
there is chance to become transparent. Transmittance of visible light depend on the thickness, and it is about
20% to 30% in 1mm thick unreinforced PBT. In GF reinforced type, transmittance will be a bit smaller (Figure 7-1
and Figure 7-2). Transmittance gets affected by crystallinity, so it might change by the molding conditions as
well. Also, transmittance of the normal colored item will be extremely small, and will be almost zero if the color is
black.
Figure 7-1 Light transmittance （5010R5/NA）
Figure 7-2 Light transmittance （5010G30/NA）
7.2 Weather and light resistance
PBT has relatively good ultraviolet light resistance, but will degrade gradually if exposed to ultraviolet light
such as the solar ray, for long time. As a ways to evaluate the degradation property by the solar ray, there is a
method that actually expose under the sunlight, or an accelerating test using an artificial ultraviolet light. Carbon
arc and xenon arc is commonly used as the ultraviolet light. As testing methods, there are test with rain which is
thinking about using it outdoor (weather resistance test) and test without rain which is thinking about using it
indoor or environment that will not get affected by rain (light resistance test).
Figure 7-3 and Figure 7-4 indicate the results of accelerated weather resistance test (carbon arc) and outdoor
exposure test. Looking at tensile strain property degradation of unreinforced PBT (5010R5), in acceleration test,
it is becoming about ten times of acceleration test compared to the actual exposure. Strength degradation of PBT
by weather resistance process is relatively small, but degrade in tensile strain can be seen. There is almost no
strength problem in GF reinforced PBT, but need an attention to the decrease of allowable displacement, if
unreinforced PBT.
Weather resistance of PBT will differ by the coloring and molecular weight (Figure 7-5 and Figure 7-6).
－ 29 －
Generally, colored grade is better in weather resistance compared to the natural grade, and especially the black
is good. Also, about natural grade, appearance change by color change, and physicality degradation tend to be
bigger than the colored grade, so be careful. Weather resistance tend to be better as the molecular weight of
PBT get larger, but liquidity will drop, so grade selection should be made thinking about product design.
Figure 7-7 and Figure 7-8 indicate the result of light resistance test. Like in the weather resistance,
degradation in tensile strain is notable, and tend to be better in color black, than the natural color.
Figure 7-3 Weather resistance (weather resistance
Figure 7-4 Weather resistance (outdoor exposure
accelerating test)
test)
Figure 7-5 Effect of color and viscosity to
Figure 7-6 Effect of color and viscosity to
weather resistance
weather resistance
Figure 7-7 Light resistance (tensile strength)
Figure 7-8 Light resistance (tensile strain)
－ 30 －