Bioplastics reinforced with filler enhance the mechanical properties of starch but reduce its hydrophilicity. In recent years, utilization of nano-sized fillers has bloomed in the fabrication of bioplastic due to their merits, such as low density, excellent mechanical properties, low abrasive nature and reactive surface for ease of modification. Numerous studies had reported that nano-sized fillers have a larger surface area than the conventional micro-sized fillers, thus enhancing the properties due to better interfacial interactions with the polymer matrix. Besides enhancing the mechanical and barrier properties, fillers are also capable of imparting specific functional properties to the bioplastics, e.g., electric conductivity or an antimicrobial character. Another added advantage of filler with nanoscale is in retaining the inherent transparency of the film, especially for the neat matrix.
Nanofiller | Proposed Application | Findings/Enhancement as Compared to the Control Film | Ref. |
---|---|---|---|
Layered silicates | |||
Nanoclay | Food packaging film | Reduction of water vapour permeability (WVP) by 14% Reduction of OP by 15% Presence of microbial growth against C. albicans Reduction of microbial growth against S. aureus and E. coli (bacteriostatic effect) |
[24] |
Nanoclay | Packaging material | Improvement of tensile strength from 5.2 to 6.3 MPa Increase in moisture absorption from 44.44% to 69.58% Complete degradation of thermoplastic starch (TPS)/nanoclay film on the 6th day |
[10] |
Nanosilica (nano-SiO2) | Packaging material | TPS film with hydrophilic nano-SiO2 had lower retrogradation rate than that with hydrophobic nano-SiO2. | [25] |
MMT | Packaging material | Improvement of tensile strength by 32% with MMT loading of 5 wt.% Improvement of Young’s modulus from 2338 to 3237 MPa Improvement of surface hydrophobicity of film (from 51.97° to 67.77°) Reduction of moisture uptake by 11% |
[26] |
Organic nanofillers | |||
Cellulose nanofibers (CNF) | Packaging material | Improvement of tensile strength by 33% with CNF loading of 3 wt.% Improvement of Young’s modulus from 2338 to 3173 MPa Improvement of surface hydrophobicity of film (from 51.97° to 53.89°) Reduction of moisture uptake by 13% |
[26] |
Cellulose nanocrystals (CNC) | Packaging film | Reduction of water absorption and water solubility by 21% and 50% with CNC loading of 20 wt.%, respectively Reduction of WVP by 8% with CNC loading of 15 wt.%.; WVP value increased with 20 wt.% CNC loading Optimum tensile strength of 4.59 MPa at 10 wt.% CNC loading; reduction in tensile strength with addition of 15 and 20 wt.% CNC loadings |
[27] |
Cellulose nanocrystals (CNC) | Food packaging film | Improvement of tensile strength by 56% with CNC loading of 10 vol.% Reduction of WVP by 17% |
[28] |
Chitosan | Packaging film | Improvement of tensile strength by 17% with chitosan loading of 10 wt.% Improvement of Young’s modulus by 13% Reduction of WVP by 35% TPS/chitosan film had higher opacity than TPS film Reduction of microbial growth against S. aureus and Escherichia coli |
[29] |
Chitosan | Packaging film | Optimum tensile strength of ~6.79 MPa at TPS/chitosan ratio of 4:6 Higher biodegradation rate with increase of starch content |
[1] |
Inorganic nanofillers | |||
Zinc oxide (ZnO) nanorods | Food packaging film | Improvement of tensile strength (47 to 90 MPa) and Young’s modulus (2.1 to 3.2 MPa) Slight reduction of elongation at break from 50% to 47%. Reduction of WVP by 42%. Improvement of antimicrobial activity against E. coli from 1.5 × 107 to 9 × 105 CFU/mL |
[30] |
Silver nanoparticles (Ag-NP) | Active packaging film | Improvement of tensile strength (2.8 to 9.0 MPa) and Young’s modulus (50 to 530 MPa) Reduction of EB from 63% to 20% Improvement of antibacterial activity against E. coli from 5.0 × 107 to 1.5 × 106 CFU/mL Film with AgNP disintegrated slower than the control film in soil (after 2 weeks vs. after 1 week) |
[31] |
Ag-NP | Food packaging film | Reduction of WVP by 16% Reduction of OP by 11% No microorganism growth against S. aureus, E. coli and C. albicans (microbiostatic effect) |
[24] |
Ag-NP/nanoclay | Food packaging film | Reduction of WVP by 33% Reduction of OP by 35% No microorganism growth against S. aureus, E. coli and C. albicans (microbiostatic effect) |
[24] |
Carbonaceous fillers | |||
Multi-walled carbon nanotubes (MWCNT) | For packaging and electroconductive applications | Improvement of tensile strength by 327% and Young’s modulus by 2484% at MWCNT loading of 0.5 wt.% Highest electrical conductivity of 56.3 S/m with 5 wt.% loading as compared to control film (1.08 × 10−3 S/m) Shifting of thermal degradation temperature to lower temperature with increasing MWCNT loading |
[32] |
Multi-walled carbon nanotubes functionalized with cetyltrimethylammonium bromide (MWCNT-CTAB) | Production of conductive film | Improvement of 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity (from ~2.5% to 30.2% after 1.5 h) Improvement of electrical conductivity (from 2.03 × 10−6 S/m to 14.75 S/m) |
[33] |
Multi-walled carbon nanotubes functionalized with ascorbic acid (MWCNT-AA) | As adsorbent for removal of methylene blue (MB) dye from aqueous solution | Enhancement of thermal stability Suitable to be used as adsorbent for removal of MB dye but not reusable |
[34] |
Multi-walled carbon nanotubes functionalized with ascorbic acid (MWCNT-AA) | As adsorbent for removal of methylene range (MO) dye from aqueous solution | Enhancement of thermal stability Suitable to be used as adsorbent for removal of MO dye but not reusable |
[35] |
Multi-walled carbon nanotubes functionalized with fructose (MWCNT-Fr) | As adsorbent for dye removal from aqueous solution | Film was too brittle for tensile test | [36] |
Multi-walled carbon nanotubes functionalized with Valine (MWCNT-Valine) | As adsorbent for removal of copper ions from aqueous solution | Enhancement of thermal stability Suitable to be used as adsorbent for removal of copper ions but not reusable |
[37] |
Graphene oxide (GO) | Food packaging film | Improvement of tensile strength (from 57.97 to 76.09 MPa) and Young’s modulus (from 20.59 to 35.91 MPa). Slight reduction of EB from 6.60% to 3.13%. Enhancement of thermal stability Improvement of surface hydrophobicity of film (from 71.33° to 112.04°) Improvement of water vapour permeability Starch/gelatin/GO film had lower biodegradability than the control film (~30% vs. 50%) after 6 weeks of soil burial degradation. |
[38] |
This entry is adapted from the peer-reviewed paper 10.3390/polym14040664