This document discusses toughening bioplastic materials with nanosprings for improved strength qualities. It finds that adding 1% nanosprings to PHBV bioplastic resulted in higher nucleation densities, smaller crystal spherulites, and increased toughness while decreasing average tensile stress and modulus of elasticity. Tensile tests showed that PHBV composites with 1% nanosprings required more energy to break and were less brittle. The nanosprings created more nucleation sites that allowed for better coupling and a less brittle material.

1. Toughening Bioplastic Materials with Nanosprings for Improved
Strength Qualities
Bryce Dinger
Renewable Materials Program, University of Idaho, Moscow ID 83844-1132
• Issues with Conventional Plastic
 Environmental pollution both terrestrial and marine
• How to Overcome These Issues
 Substitute non-degradable petrochemical based polymers
with bioplastics (biodegradable and/or bioderived plastics)
• Bioplastics
 Good biodegradability qualities
 Generate fuel by anaerobic digestion
 Divert waste from landfills
 Can contribute to healthier rural economies
 Can be made from a variety of renewable resources
Introduction
Bioplastics and Nanosprings
3-hydroxybutyrate-co-3-
hydroxyvalerate (PHBV)
Problems with PHBV
1. Formation of large
spherulites
2. Low nucleation densities
3. Low toughness (brittle)
Tensile Tests
Spherulite Morphology
Images taken from hot-stage polarized light optical microscopy
DSC Curves
Conclusions
• It was found that nanosprings resulted in
higher nucleation densities allowing more
sites for crystal spherulites.
• Through tensile tests it was found that the
PHBV + 1% NS composites required more
energy to break (tougher) than PHBV
controls, whilst having a decreased average
tensile stress and modulus of elasticity.
• The spherulites morphology of PHBV + 1% NS
composites showed smaller, densely packed
spherulites increasing its strength properties
making it less likely for cracks to propagate.
Acknowledgments
• University of Idaho OUR program for financial
support
• Dr. Armando McDonald (Renewable Materials
Program) as a faculty mentor
• Dr. David Mcilroy (Physics Department) for
supplying the nanosprings
• Ms. Shupin Luo (visiting scholar from Beijing
Forestry University) for her technical help
PHBV
Sample Preparation via Compound &
Injection Molding
RESIN MATRIX
Nanosprings
Propagating crack
Crack stopped propagating
Silica-
Nanosprings
Carbon Cycle of PHBV
Plant derived raw material
Bacteria
Fermentation
PHA polymer
(granules)
Biodegradation
Photosynthesis
RECYCLED
• Biocomposites preparation:
 Compound using a Dynisco lab
mixing extruder/molder (LMM)
 Nanosprings (NS): 0.01 wt%
 Processing temperature: 175 C
 Processing time: 7 min
 Sample injection molded into dog-
bone specimens
PHBV PHBV + 1% NS
PHBV + 1% NS PHBV
• PHBV pictured here show
large fractured spherulites
averaging 0.56 mm in
width.
• PHBV + 1% NS showed high
nucleation densities and much
smaller spherulites with an
average width of 0.16 mm.
• PHBV showed slightly higher average maximum tensile stress than PHBV +
1% NS. PHBV also had a significantly larger Modulus of Elasticity than
PHBV + 1% NS.
• The PHBV + 1% NS showed a
higher average energy at
break. This is consistent with
the microscopy because the
denser nucleation sites allowed
for better coupling and a less
brittle sample than the control
(PHBV).
• Differential scanning calorimetry (DCS) tests showed that
addition of 1% NS reduced PHBV crystallinity from 64% to
59%. This was consistent with the microscopy findings since
the NS created a greater amount of nucleation sites and
thus formed smaller spherulites with lower crystalynity.
PHBV Heat Flow Diagram PHBV NS Heat Flow Diagram

2. PHBV NS
Carbonfibers
Carbonfibers
nanospring
RESIN MATRIX
Interlayer
RESINMATRIX
Nanosprings
Propagatingcrack
Crackstoppedpropagating