Research ArticleMATERIALS ENGINEERING

Biomimetic nanocoatings with exceptional mechanical, barrier, and flame-retardant properties from large-scale one-step coassembly

See allHide authors and affiliations

Science Advances  19 Jul 2017:
Vol. 3, no. 7, e1701212
DOI: 10.1126/sciadv.1701212
  • Fig. 1 Schematic of large-scale one-step coassembly.

    Flow-induced formation of a hybrid nanocoating with a well-oriented layered structure containing a high concentration of nanosheets (not drawn to scale).

  • Fig. 2 UV-Vis and XRD characterization of the formed nanocoatings.

    (A) UV-Vis spectra and (B) XRD patterns of the coated PLA films. a.u., arbitrary units. The inset in (A) shows a digital image of PLA-PVA/MMT-50-C film placed above a printed rainbow pattern, exhibiting high transparency along the entire visible spectrum range.

  • Fig. 3 TEM images of the cross section of the nanocoatings.

    (A) PVA/MMT-20-C. (B) PVA/MMT-30-C. (C) PVA/MMT-50-C. (D) PVA/MMT-50-C (low magnification); the inset shows the grayscale analysis of the interlayer distance along the red line marked in (C). (E) PVA/MMT-60-C. (F) PVA/MMT-70-C.

  • Fig. 4 SAXS patterns of the formed nanocoatings.

    (A) PVA/MMT-20-C. (B) PVA/MMT-50-C. (C) PVA/MMT-70-C. (D) Scattered intensity as a function of incident beam to sample angle, where solid lines are the best Lorentz fits. The R2 values for the fitting for PVA/MMT-20-C, PVA/MMT-50-C, and PVA/MMT-70-C are 0.9997, 0.8912, and 0.8910, respectively.

  • Fig. 5 Integration of the PVA/MMT nanocoatings and mechanical properties of the freestanding films.

    (A) Cross-linking reaction between PVA and MMT using GA. (B) Schematic of the formation of an integrated structure after the co–cross-linking between MMT nanosheets and PVA chains. Representative stress–strain curves of (C) freestanding film samples with various MMT concentrations and (D) freestanding film samples with and without cross-linking.

  • Fig. 6 Flame-retardant performance of the coated parts.

    SEM images of the cross section of PVA/MMT-50-C before (A) and after (B) vertical combustibility testing; digital image of the PET-PVA/MMT-50-C film after 30 s of vertical combustibility testing (C). Digital image of the neat PU foam after horizontal combustibility testing: front view (D) and side view (E). Digital image of the treated PU foam after horizontal combustibility testing: front view (F) and side view (G).

  • Table 1 Mechanical properties of the freestanding nanocoatings.

    The Mechanical property data of aluminum alloy and stainless steel for comparison are from bulky materials.

    SampleTensile strength
    (MPa)
    Young’s modulus
    (GPa)
    Strain
    (%)
    Density
    (g/cm3)
    Specific strength
    (MPa·cm3/g)
    Specific modulus
    (GPa·cm3/g)
    PVA24.8 ± 2.20.5 ± 0.119.8 ± 2.3
    PVA-C32.3 ± 2.61.5 ± 0.26.7 ± 0.8
    PVA/MMT-20-C224.6 ± 18.616.8 ± 2.12.7 ± 0.51.4315811.8
    PVA/MMT-30-C241.4 ± 24.120.0 ± 2.82.2 ± 0.31.5215913.2
    PVA/MMT-50-N185.9 ± 20.620.0 ± 2.51.0 ± 0.21.7510611.5
    PVA/MMT-50-C315.7 ± 28.265.0 ± 4.80.5 ± 0.11.7518137.2
    Nacre80–135 (52)60–70 (52)0.2–0.9 (52, 53)2.65 (54)30.2–50.922.6–26.4
    Aluminum alloy 2014 (annealed) (55)185702.7367.826
    Stainless steel type 304 (55)5501957.9069.625
  • Table 2 Barrier properties of the coated plastic films.

    All films were coated on both sides. The number of MMT layers was estimated on the basis of the coating thickness and the interlayer distance of the MMT layers from the corresponding XRD patterns. WVTR, water vapor transmission rate; BOPP, biaxially oriented polypropylene; HDPE, high-density polyethylene; LDPE, low-density polyethylene; STP, standard temperature and pressure; PET, polyethylene terephthalate.

    Formulation in graftNanocoating
    thickness (nm)
    Number of
    clay layers
    WVTR
    [g/(m2·day)]
    OTR
    [ml/(m2·day)]
    O2 permeability
    of coated film
    [10−16 cm3(STP)·cm/
    cm2·s·Pa]
    O2 permeability
    of coating layer
    [10−16 cm3(STP)·cm/
    cm2·s·Pa]
    BIF
    PLA (20 μm)98.21205.0275.29
    PLA-PVA450 ± 2534.89.42.200.0488125
    PLA-PVA-C510 ± 2631.47.41.730.0433159
    PLA-PVA/MMT-20-C560 ± 34140 ± 826.43.60.850.0232324
    PLA-PVA/MMT-30-C600 ± 30166 ± 818.91.50.350.0102787
    PLA-PVA/MMT-40-C608 ± 24187 ± 714.50.60.140.00411966
    PLA-PVA/MMT-50590 ± 32220 ± 1217.20.20.050.00145506
    PLA-PVA/MMT-50-C620 ± 23212 ± 813.10.20.050.00155506
    PLA-PVA/MMT-60610 ± 24260 ± 1015.60.20.050.00155506
    PLA-PVA/MMT-60-C620 ± 31251 ± 1310.90.20.050.00155506
    PLA-PVA/MMT-70-C650 ± 25293 ± 1110.10.10.020.000613765
    PET (24 μm)4.164.016.08
    PET-PVA-C596 ± 293.114.83.820.13114
    PET-PVA/MMT-50-C625 ± 20213 ± 72.60.10.030.0008585
    BOPP (20 μm)1.11860.0424.93
    BOPP-PVA-C570 ± 300.445.010.570.300240
    BOPP-PVA/MMT-50-C615 ± 25210 ± 80.60.20.050.00158499
    HDPE (25.4 μm)0.62530.0734.05
    HDPE-PVA-C625 ± 330.433.09.810.238775
    HDPE-PVA/MMT-50-C680 ± 26239 ± 90.50.40.120.00316117
    LDPE (25.4 μm)2.14050.01175.06
    LDPE-PVA-C600 ± 281.740.812.120.282597
    LDPE-PVA/MMT-50-C625 ± 22213 ± 71.30.10.030.000739169

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/7/e1701212/DC1

    fig. S1. SEM image of a nacre acquired on a pearl.

    fig. S2. Dimensions of MMT nanosheets.

    fig. S3. Characterization of the integrated PVA/MMT nanocoatings.

    fig. S4. Comparison of mechanical properties of the materials.

    fig. S5. Surface morphology of the noncoated and coated PU foams.

    fig. S6. Comparison of horizontal and vertical casting.

    table S1. Estimated density of the nanocoatings.

    movie S1. Vertical combustibility testing of the noncoated PET film.

    movie S2. Vertical combustibility testing of the coated PET film.

    movie S3. Horizontal combustibility testing of the noncoated PU foam.

    movie S4. Horizontal combustibility testing of the coated PU foam.

    References (5660)

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. SEM image of a nacre acquired on a pearl.
    • fig. S2. Dimensions of MMT nanosheets.
    • fig. S3. Characterization of the integrated PVA/MMT nanocoatings.
    • fig. S4. Comparison of mechanical properties of the materials.
    • fig. S5. Surface morphology of the noncoated and coated PU foams.
    • fig. S6. Comparison of horizontal and vertical casting.
    • table S1. Estimated density of the nanocoatings.
    • Legends for movies S1 to S4
    • References (5660)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • movie S1 (.avi format). Vertical combustibility testing of the noncoated PET film.
    • movie S2 (.avi format). Vertical combustibility testing of the coated PET film.
    • movie S3 (.avi format). Horizontal combustibility testing of the noncoated PU foam.
    • movie S4(.avi format). Horizontal combustibility testing of the coated PU foam.

    Files in this Data Supplement:

Navigate This Article