Mechanical Properties |

Tensile strength

The stress-strain curve (hereinafter referred to as S-S curve) from the tension test for SUMIKASUPER LCP is shown. Stress and strain are proportional until the stress reaches a certain level. When designing plastic strength, it is important to remember that there are portions where the stress and strain are not proportional.
Figures 3-2-2 and 3-2-3 show the temperature dependence of the tensile strength for E6008 and E5008. The tension properties change according to the environmental temperature, but SUMIKASUPER LCP maintains high tensile strength over a wide temperature range.

Figure 3-2-1 S-S Curve of SUMIKASUPER LCP

Figure 3-2-1 S-S Curve of SUMIKASUPER LCP

Figure 3-2-2 Temperature Dependence of Tensile Strength of E6008

Figure 3-2-2 Temperature Dependence of Tensile Strength of E6008

Figure 3-2-3 Temperature Dependence of Tensile Strength of E5008

Figure 3-2-3 Temperature Dependence of Tensile Strength of E5008

Thickness Dependence of Moldings

The molecules of SUMIKASUPER LCP are easily oriented due to shearing forces at the time of melting. The thinner the walls of moldings, the greater the percentage of the skin layer. This skin layer has a very uniform molecular orientation, therefore providing greater relative strength per area of cross section. Table 3-2-1 shows the tensile properties of SUMIKASUPER LCP in thin walls. Figure 3-2-4 and Table 3-2-2 show the thickness dependence of tensile strength and flexural strength.

Table 3-2-1 Thin-wall Tensile Strength of SUMIKASUPER LCP

Item Thickness
(mm)
E5008L E5008 E4008 E6008 E6006L E6007LHF E6807LHF SV6808THF SZ6505HF
Tensile strength
(MPa)
0.5 151 161 178 199 215 153 144 130 140
0.8 151 139 171 184 194 141 139 123 137
1.2 135 119 158 164 172 141 127 116 144
1.6 132 113 131 149 160 144 126 114 144
Tensile elongation
(%)
0.5 2.4 2.9 3.0 3.0 2.4 2.7 2.8 2.1 4.8
0.8 2.7 3.1 3.7 3.5 2.8 3.6 4.1 2.8 5.7
1.2 2.8 3.3 4.1 4.0 3.4 3.8 4.1 3.3 6.2
1.6 3.1 3.5 4.5 4.2 3.7 4.2 4.3 3.6 6.8
Tensile modulus
(GPa)
0.5 18.6 17.6 19.5 18.6 21.7 17.7 16.9 15.8 14.9
0.8 16.1 15.4 17.1 16.5 15.8 15.2 14.8 12.0 13.2
1.2 14.1 12.4 13.4 12.4 12.2 11.9 11.1 10.5 11.8
1.6 11.6 11.0 10.8 11.0 9.8 11.0 10.0 9.5 10.6
Molding temperature
(°C)
400 380 350

Figure 3-2-4 Thickness Dependence of Tensile Strength of SUMIKASUPER LCP

Figure 3-2-4 Thickness Dependence of Tensile Strength of SUMIKASUPER LCP

Figure 3-2-5 Skin/Core Diagram

Figure 3-2-5 Skin/Core Diagram

Table 3-2-2 Thickness Dependence of Flexural Strength of SUMIKASUPER LCP

Item Thickness
(mm)
E6007LHF E6807LHF E6808LHF E6808UHF E6808GHF E6810KHF SV6808THF SZ6505HF SZ6506HF
Flexural strength
(MPa)
0.5 234 198 220 131 184 174 160 155 153
0.8 234 202 216 126 177 174 163 155 155
1.2 224 198 201 121 168 165 160 157 162
1.6 217 188 194 124 170 159 157 169 173
Flexural modulus
(GPa)
0.5 25.4 20.5 24.8 16.5 20.3 21.5 12.9 18.4 19.2
0.8 21.0 16.6 18.7 12.6 16.7 17.7 11.3 15.7 16.0
1.2 17.6 14.4 15.4 9.6 13.1 14.2 10.4 12.6 13.7
1.6 14.8 11.7 12.9 8.7 11.7 12.4 8.9 12.0 13.2

Temperature Dependence of Flexural Modulus

The elastic modulus of liquid crystalline polyester, such as SUMIKASUPER LCP, does not dramatically decrease at the glass transition temperature like crystalline and amorphous polymers. Rather, it tends to decrease gradually as the temperature increases. Each series has a practical flexural modulus even at 250°C, so it ranks high among heat-resistant engineering plastics. In addition, when thermal treatment is applied to a product after molding, the skin structure becomes harder and the elastic modulus tends to improve. There is a similar tendency as the elastic modulus with strength, thermal deformation temperature, and creep properties.

Figure 3-2-6 Temperature Dependence of Flexural Modulus of SUMIKASUPER LCP

Figure 3-2-6 Temperature Dependence of Flexural Modulus of SUMIKASUPER LCP

Anisotropy of physical properties

The anisotropic properties of SUMIKASUPER LCP are shown in the table below. It is apparent that the values for the flow direction (MD) differ greatly from the values perpendicular to the flow direction (TD). Please ensure that the gates are positioned properly when designing molds used in the injection molding process.

Table 3-2-3 Anisotropy of Physical Properties of SUMIKASUPER LCP

Item Unit Measurement
direction
E5008L E5008 E4008 E6008 E6006L E6007LHF
Mold shrinkage % MD 0.05 0.06 0.10 0.18 0.19 0.20
% TD 0.81 1.25 1.32 1.16 0.74 0.60
Flexural strength MPa MD 137 130 138 136 156 158
MPa TD 58 56 57 61 92 95
Flexural modulus GPa MD 13.4 12.6 12.7 12.2 11.4 14.0
GPa TD 3.7 3.3 3.0 4.4 4.7 5.1
Mold shrinkage test piece: 64 x 64 x 3mm (1mm film gate)
Flexural property test piece: 13w x 3t x 64Lmm
Distance between fulcrums: 40mm
Injection molding machine: Nissei Plastic Industry PS40E5ASE

Weld strength

Generally, since LCP has a high solidification rate with high anisotropy, it tends to have low weld strength. Since the mechanical properties of the weld tend to lose strength due to poor adhesion, sufficient consideration needs to be given when designing products and manufacturing molds.
This shows the weld flexural strength of SUMIKASUPER LCP. Two types of welds are evaluated: weld 1 where the LCP resin converges at the opening and begins to flow again, and weld 2 at the flow end where the LCP resin converges at the opening and stops flowing.

Figure 3-2-7 Weld Flexural Strength of SUMIKASUPER LCP (3mm thickness)

Figure 3-2-7 Weld Flexural Strength of SUMIKASUPER LCP (3mm thickness)

Figure 3-2-8 Test Pieces for Weld Evaluation of SUMIKASUPER LCP

Figure 3-2-8 Test Pieces for Weld Evaluation of SUMIKASUPER LCP

Figure 3-2-9 Weld flexural Strength of SUMIKASUPER LCP (0.5mm thickness)

Figure 3-2-9 Weld flexural Strength of SUMIKASUPER LCP (0.5mm thickness)

Creep properties

When calculating the strength of practical parts, it is necessary to consider changes to the dimensions and strength of the moldings under use conditions based on the creep properties and property changes caused by temperature. Figure 3-2-10 shows the flexural creep properties at 150°C for E6006L, which is a glass fiber reinforced grade. SUMIKASUPER LCP demonstrates excellent creep properties compared to crystalline PPS (40% glass fiber reinforced grade) and SUMIKAEXCEL PES (30% glass fiber reinforced grade).

Figure 3-2-10 Creep Properties of SUMIKASUPER LCP

Figure 3-2-10 Creep Properties of SUMIKASUPER LCP

Fatigue Properties

Materials under loads that fluctuate over a long period of time experience fatigue fractures. The stress-life curve from a tensile fatigue test for SUMIKASUPER LCP E6006L is shown.

Figure 3-2-11 Fatigue Properties of SUMIKASUPER LCP

Figure 3-2-11 Fatigue Properties of SUMIKASUPER LCP
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