Short-term deformation

Tensile Test

The stress-strain curve (hereinafter referred to as SS curve) in a tensile test of SUMIKAEXCEL PES is shown below. Until the stress reaches a certain level, the relationship between strain and stress is proportional. When designing the strength of PES, it is necessary to take into consideration that there are some areas where the relationship between stress and strain is not proportional.

Temperature dependence of flexural modulus

Its heat distortion temperature is 200-220°C, and its continuous use temperature is UL temperature index certified at 180-190°C.
The elastic modulus hardly changes in the temperature range from -100 to 200°C. In particular, at temperatures above 100°C, it is at the highest level of any thermoplastic resin.

Figure 3-2-3 Temperature dependence of flexural modulus

Impact strength

Weld Strength

When injection molding, the strength of welds (resin joints) is lower than that of non-welds. The strength of welds in glass fiber reinforced grades decreases depending on the glass fiber content. Figure 3-2-7 shows a comparison of non-weld and weld strength, and Table 3-2-1 shows the tensile strength of the welds of SUMIKAEXCEL PES.
We can see that SUMIKAEXCEL PES has extremely high weld strength compared to other resins. In particular, the unreinforced grade shows almost no loss in reinforcement in the welds, and has the same strength as the non-weld areas.

Weld tensile strength

Weld bending strength

Figure 3-2-8 Shape of molded product for weld evaluation

Table 3-2-2 Bending strength and Izod impact strength of welded and non-weld parts

Weld strength of thin-walled molded products

Figure 3-2-9 Relationship between molded product thickness and tensile strength of welds

Improved weld strength

If the reduction in strength caused by welds becomes a practical problem, the following methods may be able to improve the situation.

• Improvement by annealing
  The strength of the welds in glass fiber reinforced grades can be improved by 15 to 20% by annealing at 150 to 180°C.
  Suitable annealing conditions are 150°C x 20 minutes for a wall thickness of 0.5 to 1.5 mm, and 180°C x 180 minutes for a wall thickness of 2 mm.

Table 3-2-3 Improvement in tensile strength of welds by annealing

• Improvement by mold temperature
  The weld strength increases when the mold temperature during molding is higher, so try raising the mold temperature to 160-180°C.

Long-term deformation

Creep

When calculating the strength of practical parts, it is necessary to avoid using only the strength and modulus of elasticity obtained by standard tests (e.g. ASTM). When determining the optimal design, it is necessary to consider the dimensional and strength changes of the molded product under the conditions of use, based on the creep properties and the property changes due to temperature. Figure 3-2-10 shows the tensile creep properties of the unreinforced grade 4800G at 20℃ and 150℃. As is clear from the figure, SUMIKAEXCEL PES has excellent creep resistance. For the unreinforced grade, the creep deformation after three years at 20℃ and a load of 20MPa is only 1%, and at 150℃, the creep deformation after three years at a load of 10MPa is only 1%. Figure 3-2-11 shows the bending creep properties of the glass fiber reinforced grades (3601GL30, 4101GL30) at 150℃. It can be seen that SUMIKAEXCEL PES has excellent creep properties compared to crystalline PPS (40% glass fiber reinforced grade).

Fatigue properties

Materials subjected to long-term fluctuating loads will undergo fatigue failure. The stress-life curve from a tensile fatigue test is shown below.
At a temperature of 23±1°C and humidity of 60±5%, it will not break down due to fatigue up to approximately 1.0× ¹⁰⁷ times even when subjected to a repeated load of 30 MPa.

* A symbol with a right arrow (→) indicates that the test specimen did not break during that number of repetitions.