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PBT is the best material to make a loose tube for fiber. The Optical fiber cable relies on the fiber to transmit information. In order to protect the fiber from getting damaged when the cable is inserted, it is required to put a piece or some pieces of fiber into a loose tube filled with petroleum jelly to let the fiber move freely inside the tube made out of PBT. 

Technical Characteristics Table:

Number Item Unit Result
1 Density g/cm³ 1.25-1.35
2 Melt Index (250°C, 2160g) g/10 min 7.0-15.0
3 Water Content % ≤0.1
4 Saturated water absorptivity % ≤0.5
5 Yield Strength Mpa ≥50
Yield Elongation % 5.0-10
Elongation at Break % ≥100
Tensile modules of elasticity Mpa ≥2100
6 Flexural Modulus Mpa ≥2200
Flexural Strength at 3.5% Bending Strain Mpa ≥60
7 Melt Point °C 210-230
8 Shore Hardness Hp / ≥70
9 Cantilever beam impact strength
23°C KJ/m² ≥5.0
Minus 40°C ≥4.0
10 Coefficient of linear expansion
10-4K-1 ≤2.0
11 Volume Resistance ?•cm ≥1x1015
12 Heat deflection temperature
1.8MPa °C ≥55
0.45MPa ≥170
13 Compatibility with Filling Compound
Yield Strength Mpa ≥50
Elongation at Break % ≥100
14 Appearance   Cream white, pale yellow, colorless & transparent columned granular 
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