Background Commonly Used Fabric Tests Thermal Physical Test Methods Objective Limitations Conclusions 9/16/2016

Transcription

1 Dominique Adams Product Development Engineer Industrial Fabrics September 21, 2016 AATCC Flammability Symposium Background Commonly Used Fabric Tests Thermal Physical Test Methods Objective Limitations Conclusions 1

2 Characterization of fabric protection must be based upon a multitude of tests. Each test evaluates the fabric s thermal protection or physical performance. All tests have benefits and limitations. Vertical Flammability ASTM D6413 Thermal Protective /Heat Transfer Performance ASTM F1060 ASTM F2700 Thermal Shrinkage ASTM F2894 Thermal Manikin ASTM F1930 Electric Arc Testing ASTM F1959 2

3 Self Extinguish : Vertical Flammability Does not sustain combustion No melt, drip, or stick Char Stability : Vertical Flammability Integrity after flame exposure Brittle vs Supple Char Thermal Insulation : Thermal Protective/Heat Transfer Performance Insulation capacity Strength during and after exposure Thermal Shrinkage : Oven Test Dimensional stability after convective heat exposure Fabric characteristics after high heat exposure Burn Injury: Thermal Manikin Measures % body burn with 2 cal/sec/cm 2 thermal exposure Demonstrates flame shrinkage Burn Injury: Electric Arc Testing Measures probability of 2 nd degree burn during extremely short duration, high radiant energy exposure Provides arc rating for fabric 3

4 ASTM D6413 Test Objective: Propensity of fabric to combust Designed for edge ignition evaluation Observe fabric damage and stability during/after flame exposure Strength of char Procedure 12 sec. exposure, methane flame 1.5 inch height Sample edge held in stationary frame Record afterflame, afterglow, char length Use weights for char length tear based on fabric weight 4

5 ASTM D6413 Fabric may burn and/or shrink away from flame Progressive vs stationary afterglow Duration of test may mask afterflame 5

6 ASTM F1060/ASTM F2700 Test Objective Measures fabric thermal insulative capability Pain/burn threshold time Procedure 2.0 cal/cm 2 /sec exposure on fabric face 6 x 6 exposure Comparison of heat rate through fabric with existing data for time to pain/burn (Stoll curve) Contact and Spaced configuration in HTP ASTM F1060/ASTM F2700 Material static during thermal exposure No evaluation of physical property changes due to thermal exposure No measure of flame shrinkage Results are mass dependent, not material dependent In contact configuration 6

7 ASTM F2894 Test Objective Heat resistance of fabric / thermal exposure characteristics Ignition, melting, dripping, charring, separation Dimensional stability after hot air oven Procedure Expose fabric to 500 F in circulating air oven for 5 minutes Observe fabric characteristics after oven exposure Measure change in length and width dimensions ASTM F2894 No indication of fabric flame resistance Does not measure flame shrinkage Does not represent shrinkage observed during manikin burn Fabric characteristics can only be observed after exposure, not during Materials test 7

8 ASTM F1930 Test Objective Provides % predicted body burn for given exposure time Measures garment thermal insulative capability Procedure 2.0 cal/cm 2 /sec exposure Manikin contains multiple calorimeters on surface to measure heat flux Comparison of heat rate through fabric with existing time to pain/ burn (Stoll) data Uses specified garment size to dress manikin ASTM F1930 Large variation in results observed between different manikin/sensor technologies Results dependent on garment fit Does not quantify char stability or thermal shrinkage 8

9 all fabrics approximately 6.5 osy % Thermal Shrinkage (F2894) % Manikin Body Burn (F1930) Aramid /FR Rayon Modacrylic Blend 100% Aramid ASTM F1959 Test Objective Use fabric thermal insulative capability during arc flash to provide arc rating Propensity to break open during electric arc exposure Procedure Generates heat flux from cal/cm 2 *s Two calorimeters in each of the three test panels Comparison of heat rate through fabric with existing time to second degree burn (Stoll) data Arc rating is the observed incident energy on a fabric resulting in 50% probability onset of second degree burn 9

10 ASTM F1959 Repeatability of test is difficult due to high amount of energy distribution between panels Limited controllability No temperature/humidity conditioning Performance dependent on weight 10

11 Breaking Strength : Tensile Strength Maximum force required to break all yarns in width of specimen Constant rate of extension, constant rate of load, constant rate of traverse Grab, Strip, etc. Resistance to Tear : Tear Strength Force required to propagate a single tear in the fabric Falling pendulum type, constant rate of extension type Elmendorf, Trap, Trouser, etc. Not a good measure of strength for fabrics with high elongation/stretch (knits) No direct correlation between tensile strength values and physical performance of fabric 11

12 Propagation of rip vs initiation of rip No direct correlation between tear strength and durability of fabric Performance depends on type of machine used Constant rate of extension vs Pendulum Perfect fabric thermal or physical test does not exist Existing tests do provide useful information Characterize fabric thermal resistance with the following: Multiple Test Evaluation Inspection of Post Test Samples Thermal and Physical Test Combinations New test needed: Dynamic, thermal exposure measurement, bench scale Bench scale electric arc 12