IHDIV, NSWC's Rheological Capabilities
Suzanne E. PrickettBill Newton
IHDIV NSWC
PDCS TSE User's Group Meeting
October 30th, 2002
Rheology
• The Study of Flow and Deformation of Materials• Yield Stress• Viscoplasticisity• Shear Rate• Wall Slip• Activation Energy
• Hershel Bulkley Constitutive Equation – (w = o + mow
n)
• Necessary for Die Design and Modeling
IHDIV NSWC Rheological Capabilities
• Capillary Dies Used in Conjunction with the 2" Vertical Press (~7 years)
• Slit Die Rheometer Used with 40 mm Twin Screw Extruder (redesigned last year)
• Torque Rheometer (~5 years)
• Small Scale Capillary Rheometer (~1 year – not yet approved for use with energetics)
Capillary Dies w/2" Press
• Dies and Press Jacketed for Temperature Control (ambient to 270ºF)
• Automated Data Acquisition System• Dies Instrumented with Dynisco
Temperature/Pressure Transducer at Capillary Entrance
• Need ~ 4 – 10 Pounds of Material to Fully Characterize Rheological Behavior
• Characterized ~ 10 Types of Energetic Materials as a Function of Temperature, Solvent Level, Formulation Variations, and Processing Technique
• Currently Characterizing AA-2 for ESTCP Nitrocellulose Based Propellant Manufacturing Waste Minimization Processing
Capillary Dies w/2" Press
Diameter
Length
PressureProbe
Diameter
Length
PressureProbe
2/40 3/40 4/40 5/40 6/405/25
9/12* 8/12* 7/12 6/12 5/12
*On Order
x/y: x = die diameter (mm)y = length to diameter ratio
To determine wall slip
To determine end effects
Capillary Dies w/2" Press
Solvent Based Materials• Lova (EX-99)• PAX-2A• Shredder Propellant• LI-10 (EX-98)
Double Base• AA-2• AA-6
TPE Based Materials• GEM Gun Propellant
• GEM Rocket Propellant
• TPEMACS Gun Propellant– polyBAMO/AMMO
– Hytrel®
Extruded Composite
Materials Characterized Include:
On-Line Adjustable Gap Die Used in Conjunction with 40 mm TSE
Distance, (cm)
Fixed gap width (W)Known volumetric flow rate (Q)Change gap height (H)Measure pressure, P(z) Determine apparent shear rate ( )
pressure gradient ( )shear stress (w )shear sensitivity index (n)
Change throughput, Q, to determine wall slip
a
z
P
Slit Die Used in Conjunction with 40 mm TSE
• Determine Rheological Behavior of Materials Processed on the TSE– Energetics containing solvents (e.g., Lova) must be
tested on-line or batch processed and tested in a capillary die
• Solvent loss• Are material properties the same (batch vs. continuous?)
– Energetics based on TPEs can be processed on the TSE and then tested in a capillary die
• Are material properties the same (batch vs. continuous?)• Do rheological properties change due to heating & cooling?
Slit Die Used in Conjunction with 40 mm TSE
• Characterized Lova and Airbag Simulant as a Function of Temperature and %Solvent with the On-Line Slit Die
Pressure (P) vs Distance (z)Lova, 6.8 kg/hr, 13 wt% solvent, 49 C
Haake Torque Rheometer
• Old Machine – 2+ generations from latest model• To date, mostly used as a small scale compounder
(~ 60 cm3)• Variety of formulations
– GEM Rocket Propellant– Lova– Thermobarics– ESEM IM Propellant– Nanoaluminum Formulation– Red Phosphorous Flares
Haake Torque Rheometer
ESEM IM Propellant76% RDX/24% Binder
0
20
40
60
80
100
120
140
0:00:00 0:10:00 0:20:00 0:30:00 0:40:00 0:50:00 1:00:00 1:10:00
Time (h:mm:ss)
Tem
per
atu
re (
C)
Ro
tor
Sp
eed
(rp
m)
0
200
400
600
800
1000
1200
1400
1600
1800
To
rqu
e (m
*g)
Speed (rpm)
Oil Temp.(degC)Mix Temp.(degC)Torque (m*g)
Premix 61.7% RDX
38.3% Binder
1/5 RDX
1/5 RDX
1/5 RDX
1/5 RDX
1/5 RDX
Monitor Torque vs. TimeBinder MeltSolids Incorporation
Haake Torque Rheometer
• Procuring New Haake Torque Rheometer– November/December '02 Delivery Date– Includes New Design Features– Up-to-Date Data Acquisition System– Includes Optional Clear Front Plate for Flow
Visualization
Lab Scale Capillary Rheometer
3/10 2/10 1/10
2/5
2/15 1/20 0.5/20
x/y: x = die diameter (mm)y = length to diameter ratio
To determine wall slip
To determine end effects
Procured/Installed a Goettfert Lab Scale Triple Bore Capillary Rheometer
Material Can Be Extruded through 3 Capillary Dies Simultaneously
Requires ~100 grams for Preliminary Characterization – Use when only small amounts of material are available
Dies:
• Using to investigate the effect of nanoparticles on formulation viscosity
Lab Scale Capillary Rheometer
Shear Stress vs Shear RateH3 Aluminum
8.5
9
9.5
10
10.5
11
11.5
12
12.5
0 1 2 3 4 5 6
ln (Corrected Shear Rate)
ln (
Co
rre
cte
d S
he
ar
Str
es
s)
55vol% 90C
30/2/15/90
20/2/10/90
55 Vol% 100C
30/2/15/100
20/2/10/100
10/2/5/100
25 Vol% 90C
30/2/15/90
20/2/10/90
10/2/5/90
Linear (55vol% 90C)
Linear (55 Vol%100C)Linear (25 Vol% 90C)
Solids Temperature Loading (C) m n 55 vol% 90 9,300 0.56 55 vol% 100 4,000 0.67 25 vol% 90 160 1.04
55 vol%, 90C
55 vol%, 100C 25 vol%, 90C
Rheological Capabilities @ IHDIV NSWC
• Continuing to Expand Rheological Capabilities– Procuring Additional Capillary Dies for the 2" Press to
Determine the Wall Slip Behavior of Highly Viscous Material (e.g., double base)
– Procuring a New Haake Torque Rheometer• Higher Resolution of Torque
• Improved Safety Features
– Improved the Design of the On-Line Slit Die
– Obtaining Permission to Process Energetic Materials in the Lab Scale Capillary Rheometer