EoW May 2010

technical article

The special features of enhanced FR TPE-S are: RoHS compliance • Pass UL 94 V-0 rating at 0.06" • Meet VW-1 and 1061 cable flame test, • without dripping Brittle point below –50˚C • Exhibit good retention of tensile • properties upon heat ageing at 136˚C for 7 days and also at 158˚C for 7 days Show excellent electrical properties • 3.2 VW-1 and method 1061 cable flammability tests and coil cords Wire and cable extrusion trials verified these properties and also indicated good processability. These compounds are ideal for flexible cords, coil cords, robotics cables, power tools, high-flex cables, low temperature applications, and connector parts and components requiring a V-0 flame rating. In VW-1 and 1061 cable flammability tests, the wire or cable must pass the criteria of retention of more than 75% of the indicator flag without dripping. For illustration, Figures 6 and 7 show a burned wire and a burned cable made of EL-1392B compound. The retention of the indicator flag upon VW-1 and 1061 cable flammability test is achieved without dripping. Figure 8 shows a coil cord made with EL-1392B for insulation and jacketing. It has very good retract performance.

Increasing FR technologies

Shear rate, 1/s

Figure 3 ▲ ▲ : Viscosity of FR TPE-S (200˚C)

3 Enhanced flame retardant TPE-S 3.1 Properties

Control

Control FR Technologies

The material technologies and their underlying principles discussed above are used to develop enhanced flame retardant TPE-S. These enhanced FR TPE-S compounds use an RoHS-compliant flame retardant. Specific examples are highlighted below. See Table 2 for the typical properties of several enhanced flame retardant TPE-S.

Foil

Crack

Figure 4 ▲ ▲ : Char formation for conventional and combined FR technologies

Eliminating dripping: • As demonstrated in Figure 3 , the incorporation of combined FR technologies in TPEs increases the viscosity at low shear rates. This is translated to reduced drip under UL 94 vertical burning. Enhancing char formation and char • integrity: Char formation and integrity is desirable for improved flame retar- dancy. The incorporation of combined FR technologies to flame-retardant TPE compounds can promote char formation when exposed to a flame. Figure 4 compares the char of con- ventional FR TPE-S to that of the new flame-retardant TPE-S technology. The dark portion is char, and the white portion is ash or cracks in the char. The char for the combined FR technology is much thicker than that of a conventional FR TPE-S and shows less cracking. Reducing peak heat release rate: • Figure 5 shows the cone calorimeter peak heat release rate (PHRR) data of a conventional FR TPE-S versus the new combined FR TPE-S technology. The results show that the incorporation of combined ingredients reduces the peak heat release rate. It can also slightly increase the flame out time.

Table 2 ▼ ▼ : Typical property values of enhanced flame retardant TPE-S

Property

EL-1392B EL-1934E

EL-1934F

RoHS compliance

yes

yes

yes

Sp. Gr

1.24

1.32

1.30

Hardness, Shore A Tensile strength, psi

86

82

73

1540

1480 630 98% 92% 97% 87%

1220

Elongation %

540

680

Tensile strength retention *

99 % 95% 100%

105%

Elongation retention *

95%

Tensile strength retention * Elongation retention **

104%

95%

92%

Brittle point °C Melt Index # DC, 1 Mega Hz DF 1 Mega Hz DC, 1 kilo Hz

-51

-59

-60

14

14

20

2.42

2.41

2.40

0.003

0.0032

0.003

2.43

2.43

2.41

DF, 1 kilo Hz

0.0029

0.0043

0.0027

Oxygen Index, % oxygen

28 V0

30 V0

27 V0

UL 94 ##

* 136ºC 7 days ageing ** 156ºC 7 days ageing # 200ºC 5kg, g/10 min

## thickness 0.060 "

DC= dielectric constant

DF= dielectric dissipation factor

62

EuroWire – May 2010