Synthesis and characterization of biodegradable PVA/starch composite films reinforced with cellulose nanocrystals Bianca-Ioana Dogaru1, 2, Carmen-Mihaela Popescu1, Mirela Goanta2, Daniel Timpu1, Maria-Cristina Popescu1 1Petru Poni Institute of Macromolecular Chemistry of the Romanian Academy, Iasi, Romania 2 Al. I. Cuza University, Faculty of Chemistry, Iasi, Romania
Why PVA? Increasing government initiatives to support green packaging coupled with the biodegradable nature of PVA films is expected to drive demand over the next years. Polyvinyl alcohol (PVA) is a biodegradable synthetic polymer, non-carcinogenic, has good biocompatibility and excellent film-forming properties. A material with high technological potential as an water processable and melt-processable material PVA water-soluble film has good air barrier and resistance to oil. It could preserve food for longer time and keep fresh.
Water soluble PVA films are used for packaging in various industries; and over 66% of them are used for detergent and agrochemicals. Other applications may include : Water Soluble Laundry Bag Food packing Commodity packaging Chemical packing Packaging of Infection Control Agriculture Usage
Why Starch? Starch is economically competitive with polymers derived from petroleum for manufacture of packaging materials. Starch has been widely used in different industries due to its low cost, biodegradability and renewability. It is use to improve the properties of food such as viscosity, texture, thickness etc. However the starch granules hydrate easy, swell rapidly, lose viscosity, and produce weak bodies which create a very stringy and cohesive paste. The combination of the properties of the starch/PVA films make them one of the most popular biodegradable blend. However, some of their physical properties (mechanical properties and water resistance) are still lower than those of other synthetic polymers made from petroleum resources. Many researchers tried to resolve these problems by ultraviolet irradiation [1], by adding crosslinking agents [2], or different types of nanoparticles [3]
Materials 90% PVA/10 % S 75% PVA/25% S 50% PVA/50% S 5% CNC 10 % CNC water glycerol water 90% PVA/10 % S 75% PVA/25% S 50% PVA/50% S 5% CNC 10 % CNC 15% CNC
PVA/Starch films 90 %PVA/10% S 0 % CN 5% CNC 15% CNC
IR Spectroscopy 3300 cm-1 stretching vibration of free and bonded OH groups 1640 cm-1 bending vibration of O-H groups The bands at 1240 and 1082 cm-1 are attributed to the stretching vibration of C–O in C–O–H groups, and the band at 1020 cm-1 is related to the C–O stretching vibration of C–O–C groups of the glucose unit in starch The absorption bends appearing at 1425, 1373, and 845 cm-1 are due to the starch only and this is an ideal reference frequency to monitor starch content in the films.
deformation vibration of CH groups 1427 cm-1, 1324 cm-1, 1279 cm-1 deformation vibration of CH groups 1158 cm-1 stretching vibration of COC groups 1053 cm-1, 1000 cm-1 stretching vibration of CO groups
WAXD analysis of composite films Precursors films after dewatering: Red = S Black = CNC Blue = PVA (90% PVA / 10 % S) + 0 % CNC / 5 % CNC / 10 % CNC / 15 % CNC the increase of the signal intensities from 22.5 and 15.3 (2 theta degree) is in correlation with the increase of the CNC content the modification of the signal from 19.7 is the combinated contribution of PVA and S
AFM cross section 3D 2D hystogram phase contrast 75%PVA / 25% S surface cross section 3D 2D hystogram phase contrast
(90% PVA/ 10% S) + CNC 0 % CNC 5 % CNC 15 % CNC 10 % CNC
Standard parameters statistics Amount of sampling 65536 Max 336.085 nm Min 0 nm Peak-to-peak, Sy 336.085 nm Ten point height, Sz 169.558 nm Average 143.637 nm Average Roughness, Sa 37.9724 nm Second moment 151.875 Root Mean Square, Sq 49.3604 nm Surface skewness, Ssk 0.930533 Coefficient of kurtosis, Ska 0.635574 Entropy 11.4425 Redundance -0.364083 Standard parameters statistics - square area side: 0.5 / 1 / 2 / 5 / 10 / 20 / 50 um - 256256 pixels resolution 3 different investigation zones on the same film totally 21 data set / every film surface l (um) mean 0.5 2.97 2.10 1.85 2.31 1 2.93 8.77 6.04 5.92 2 4.59 10.93 9.35 8.29 5 23.10 27.45 25.11 25.22 10 40.13 41.26 40.05 40.48 20 55.19 64.66 46.90 55.58 50 81.98 90.31 65.01 79.10 Root Mean Square, Sq
Root Mean Square, Sq increases with the percent of CNC Sq (nm) 15 % CNC 10 % CNC 5 % CNC 0 % CNC l (m) (90% PVA + 10 % S) + % CNC Root Mean Square, Sq increases with the percent of CNC
Water vapor sorption RH - 11-94 % T=25 oC
Water vapor sorption
Water vapor sorption
Conclusions PVA/Starch/CNC composite films were prepared The interactions between the components were evidenced by infrared spectroscopy AFM indicated the surface morphology of composite films The statistical analysis evidenced the modifications in the mean rugosity as a function of composite film composition and/or CNC concentration The water vapor sorption decreased with CNC content, indicating the formation of intermolecular bonds involving OH groups between starch and PVA molecules
Thank you for your attention!