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