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Chromacol Seal Properties

Seal Hardness
The hardness testing of plastics is most commonly measured by the Shore (Durometer) test.This method measures the resistance of plastics toward indentation and provides an empirical hardness value. Shore Hardness, is the preferred method for rubbers/elastomers and is also commonly used for 'softer' plastics such as fluoropolymers. Most septa hardness values are stated in Shore A. The results obtained from this test are a useful measure of relative resistance to piercing of various grades of polymers.This gives guidance on the type of needle that will penetrate the seal and whether thinner gauge needles may be used.


Seals in 8mm, 9mm, 11mm, 12mm Caps
Seal Material Shore Hardness Thickness (mm)
–TST1 Red PTFE/white silicone/red PTFE 57 1
–CBT1 Chlorobutyl/PTFE 52 1
–ST14 Blue silicone/PTFE 50 1.2
–6RT1/AC6 Natural rubber/PTFE 38 1
–ST101Blue silicone/PTFE 30 1
-ST143 White silicone/PTFE 20 1.4
–ST144 Blue silicone/redPTFE 20 1.4
Seal Material Shore Hardness Thickness (mm)
–V1 Viton 62 1
–AC7 Natural rubber/PTFE 60 1
–8RT1 Natural rubber/PTFE 58 1
–ST2 White silicone/red PTFE 57 2
–ST18 White silicone/red PTFE 57 1.8
–ST15 White silicone/red PTFE 57 1.5
–ST1 White silicone/red PTFE 57 1
 
Seals in 20mm Caps
 
Seal Material Shore Hardness Thickness (mm) Max Temp (°C)
–CBT3B Chlorobutyl/PTFE 52 3 120
–CBT3 Chlorobutyl/PTFE 52 3 120
–CB3 Chlorobutyl/PTFE 52 3 120
–ST3 Blue silicone/PTFE 45 3 200
Seal Material Shore Hardness Thickness (mm) Max Temp (°C)
–ST3HT Red silicone/PTFE 45 3 250
–ST3(W)White silicone/PTFE 57 3 200
–AS3 White silicone/ aluminium 45 3 <170
–ASH3 Red silicone/ aluminium 45 3 >170
 
Seal Properties
 
Rubber Used primarily for routine analysis in gas chromatography. Offers moderate resealability and good chemical inertness. Not recommended for multiple injections or holding samples for further analysis. PTFE is protective layer that once broken exposes rubber to chemical attack.
PTFE/Red rubber -AC6, 6RT1 Low durometer of rubber allows ease of needle penetration.A popular and economical septa for general GC purposes.
PTFE/red rubber -AC7, 8RT1 Harder grade of rubber for use with piercing needle. Most popular and economical septa for general GC purposes in Agilent systems.
Pre-slit PTFE/red rubber - 8RT1X Pre-slit, high quality red rubber with a thin (0.003") layer PTFE. For applications using a very thin-gauge syringe needle or in instances when a vacuum may form in the vial.
Silicone rubber High quality, silicone rubber laminated to PTFE. Use when excellent resealing qualities are a must. Septum resists coring and is recommended when multiple injections are required. Preferred septa for use in liquid chromatography applications.
PTFE/silicone - ST1, ST15, ST18, ST2 A white medium hardness silicone with red PTFE protective layer available in a range of thickness.
PTFE/silicone - ST101, ST14 A very pure soft silicone laminated to PTFE. Septum resists coring and is recommended for instruments with fine gauge needles. Also recommended for LC-MS and GC-MS due to high purity.
PTFE /silicone/PTFE -ST143,ST144 A very soft silicone laminated to PTFE. Use with flexible needle.
PTFE /silicone/PTFE -TST1,TST11 A layer of PTFE on each side of medium hardness silicone. Most resistant to coring with above average resealing characteristics. Recommended for most demanding applications such as trace analysis, longer time between injections or for internal standards. Use with Gilson instruments and with any autosampler using large diameter, blunt-tip syringe needles.
Pre-slit PTFE/Silicone - ST1X, ST101X, ST14X Pre-slit, high quality pure white silicone faced with PTFE. For applications using a very thin-gauge syringe needle or in instances when a vacuum may form in the vial. Highly recommended for Shimadzu and Hitachi autosampler units.
PTFE and fluoropolymers Very good chemical resistance and used as a protective layer for less resistant elastomers.
PTFE – T, T02 For single injections and short sample cycles.This type of septa is not resealable.
Viton -V1 Viton provides the best chemical resistance with limited resealability. Recommended for chlorinated solvents. Due to Viton®'s intrinsic hardness, these septa are not suitable for 32-gauge syringe needles.
Integral plastic seal Moulded as part of the cap.
Polyethylene – PE, Polypropylene – PP Chemically resistant but for one time use only with no resealability.
 
20mm seal selection for Headspace applications
 
Butyl rubber/chlorobutyl rubber An economical choice for low temperature (< 125°C) or low-pressure applications. Not suitable for alkanes, benzene, chlorinated solvents or cyclohexane without a protective PTFE layer.
Grey butyl stopper - B3P Does not provide PTFE barrier.
Blue chlorobutyl -CB3 Does not provide PTFE barrier.
Blue chlorobutyl/natural PTFE -CBT3 Has PTFE barrier that makes it suitable for work with general organic solvents.
Grey PTFE/chlorobutyl molded -CBT3B Specially molded seal with PTFE insert. Sealing surface of Butyl and PTFE affects a more positive seal than non-PTFE-faced septa. Ideal choice for temperatures below 125°C. Good sealing characteristics, excellent resistance to most solvents and coring, and high puncture tolerance. PTFE provides increased chemical resistance.
Silicone rubber Excellent septa choice for volatiles with very low background peaks and low permeability.Also ideal for alcohols and aqueous samples. Good resealing characteristics and resistant to coring.
Natural PTFE/blue silicone – ST3 Best septa choice when temperatures are over 125°C.
Natural PTFE/red silicone - ST3HT High temperature formulated seal with low bleed.. Best septa choice when temperatures are up to 250°C.
Blue Silicone/red PTFE - ST15 Thin 1.4mm seal with PTFE face for use with Fisons/ Carlo Erba Instruments. Resealing capability limited due to thinner silicone layer.
Aluminium/white silicone -AS3 Reflective aluminium face protects the silicone seal.The white silicone is suitable for use up to 170°C
Aluminium/red silicone -ASH3 Reflective aluminium face protects the silicone seal.The red silicone is suitable for use at temperatures of >170°C
Blue silicone/natural PTFE – ST101 Soft silicone with clean formulation for minimal interference.Thinner seal suitable for solvent washing, solvent extraction and SPME applications with some resealing. Not for direct headspace applications.
Freezer bungs - 2FB3 Butyl bungs for sealing of lyophilized products. Compatible with low storage temperatures.
PTFE/silicone ring – LLX Thin PTFE layer with sealing ring to give secure closure for strong solvents. For use in liquid extraction or SPME stage during sample preparation. Does not reseal.
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