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.

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

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

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

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

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

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