NYLON-12 NANOCOMPOSITE THIN FILMS AS PROTECTIVE BARRIERS by Dr. - - PowerPoint PPT Presentation

NYLON-12 NANOCOMPOSITE THIN FILMS AS PROTECTIVE BARRIERS

by

• Dr. Cecilia L. Stevens, Polymer Engineering Company
• Dr. Marek J. Gnatowski, Polymer Engineering Company
• Dr. Scott Duncan, Defence Research and Development

Canada

Concept product example

Current technology Target technology

Thicknesses of barrier films: an evolution

1270 µm (1.27 mm) 1980’s glove 500 µm (0.5 mm)

1990’s glove

25 µm (0.025 mm)

thin film

Tortuous path theorem

Tortuous path Exfoliated Platelets Polymer film

f

V W L ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + = 2 1 τ

Equipment used for sample blending: potential differences in performance

Batch blender (BB) Single-screw extruder (SS) Compounding twin-screw (D6/2) Twin-screw extruder (TSE)

Film casting

TEM images (1):

Exfoliation issues

BB SS

TEM images (2)

D6/2 TSE

Platelet width: ‘greater shear’ gives smaller platelets

90 110 130 150 170 190 210 BB SS D6/2 TSE Blending method Observed platelet width (nm)

0.2 0.4 0.6 0.8 1 1.2 BB SS D6/2 TSE Blending method FTIR Peak Height

FTIR clay peak:

greater shear gives a higher peak

SSNMR:

greater shear gives better dispersion and a lower T1

H relaxation time

340 350 360 370 380 390 400 410 420 BB SS D6/2 TSE Blending method T1H relaxation time (ms)

Penetration and re-emission testing

Nylon-12 had no detectable re-emission of sulphur mustard in 24 hours.

Penetration curves

1 2 3 4 5 6 5 10 15 20 25 Time (h) Penetration (ug) 100% nylon-12 BB SS D6/2 TSE

Breakthrough time:

strongly affected by exfoliation; not directly correlated to dispersion

2 4 6 8 10 12 14 16 BB SS D6/2 TSE Blending method Breakthrough time (h) 100% nylon

Breakthrough time:

dependent on clay loading

2 4 6 8 10 12 14 2 4 6 8 10 Clay concentration (%) Breakthrough time (h)

Tensile strength:

Not directly dependent on dispersion.

10 20 30 40 50 60 BB SS D6/2 TSE Blending method Yield stress (MPa) 100% nylon *Apparent correlation to breakthrough time is deceptive.

Tensile strength:

responsive to clay loading

40 42 44 46 48 50 52 54 2 4 6 8 10

Clay concentration (%) Stress at yield (MPa)

Tensile Modulus (stiffness):

Similar to tensile strength

200 400 600 800 1000 1200 1400 1600 1800 BB SS D6/2 TSE Blending method Modulus (MPa) 100% nylon

Tensile Modulus (stiffness):

increases with clay loading

600 700 800 900 1000 1100 1200 1300 1400 1500 1600 2 4 6 8 10

Clay concentration (%) Modulus (MPa)

Tear strength:

Similar to tensile strength and modulus

100% nylon MD TD 0.0 50.0 100.0 150.0 200.0 250.0 300.0 350.0 BB SS D6/2 TSE Blending method Tear strength (N/mm)

Extrusion direction Transverse direction

Tear strength:

increases slightly with clay loading

50 100 150 200 250 300 350 2 4 6 8 10 Clay concentration (%) Tear strength (N/mm)

Machine direction Transverse direction

Transparency

2.5% clay 5.0% clay 7.5% clay 10.0% clay

Conclusions

Nylon-12 is a suitable material for use in warfare agent barrier technology. Montmorillonite nanoclay can greatly improve the barrier and mechanical properties of nylon-12 thin films. Effective exfoliation and dispersion of the clay is critical to the film performance. Dispersion, barrier properties, and mechanical properties are not directly related. Optimal clay loading may be below 10%. Optical transparency is excellent even at 10% clay loading

Acknowledgements

PEC David Lesewick Beverley Start Kate Mao DRDC Ben Lacroix W.C. Brabender Andrew Yacykewych UBC SSNMR Colin Fyfe Richard Darton UBC TEM Kim Rensing Derrick Horne Garnet Martens