Abstract: In this study, acids with various chain lengths (C6, C8, C10 and C12) modified by methane sulfonic acid (MSA) and temperature were used to modify tapioca starch (TPS), then the glycerol (GA) were added into modified starch, to prepare new blends. The mechanical properties, thermal properties and physical properties of blends were studied. This investigation was divided into two parts. First, the biodegradable materials were used such as starch and glycerol with hexanedioic acid (HA), suberic acid (SBA), sebacic acid (SA), decanedicarboxylic acid (DA) manufacturing with different temperatures (90, 110 and 130 °C). And then, the solution was added into modified starch to prepare the blends by using single-screw extruder. The FT-IR patterns indicated that the characteristic peak of C=O in ester was observed at 1730 cm-1. It is proved that different chain length acids (C6, C8, C10 and C12) reacted with glycerol by esterification and these are used to plasticize blends during extrusion. In addition, the blends would improve the hydrolysis and thermal stability. The water contact angle increased from 43.0° to 64.0°. Second, the HA (110 °C), SBA (110 °C), SA (110 °C), and DA blends (130 °C) were used in study, because they possessed good mechanical properties, water resistances and thermal stability. On the other hand, the various contents (0, 0.005, 0.010, 0.020 g) of MSA were also used to modify the mechanical properties of blends. We observed that the blends were added to MSA, and then the FT-IR patterns indicated that the C=O ester appeared at 1730 cm-1. For this reason, the hydrophobic blends were produced. The water contact angle of the MSA blends increased from 55.0° to 71.0°. Although break elongation of the MSA blends reduced from the original 220% to 128%, the stress increased from 2.5 MPa to 5.1 MPa. Therefore, the optimal composition of blends was the DA blend (130 °C) with adding of MSA (0.005 g).
Abstract: Thermoplastic starch (TPS) plasticized by 1-ethyl-3-methylimidazolium acetate [Emim][OAc] were obtained through gelatinization process. The gelatinization process occurred in the presence of water and [Emim][OAc] as plasticizer at high temperature (90˚C). The influence of [Emim][OAc] and water on the gelatinization and interactions with starch have been studied over a range of compositions. The homogenous mass was obtained for the samples containing 35, 40 and 43.5 % of water contents which showed that water plays important role in gelatinization process. Detailed IR spectroscopy analysis showed decrease in hydrogen bonding intensity and strong interaction between acetate anion in [Emim][OAc] and starch hydroxyl groups in the presence of [Emim][OAc]. Starch-[Emim][OAc]-water mixture at 10-3-8.7 presented homogenous mass, less hydrogen bonding intensity and strong interaction between acetate anion in [Emim][OAc] and starch hydroxyl groups.
Abstract: Polylactic acid (PLA) is the most commercially
available bio-based and biodegradable plastic at present. PLA has
been used in plastic related industries including single-used
containers, disposable and environmentally friendly packaging owing
to its renewability, compostability, biodegradability, and safety.
Although PLA demonstrates reasonably good optical, physical,
mechanical and barrier properties comparable to the existing
petroleum-based plastics, its brittleness and mold shrinkage as well as
its price are the points to be concerned for the production of rigid and
semi-rigid packaging. Blending PLA with other bio-based polymers
including thermoplastic starch (TPS) is an alternative not only to
achieve a complete bio-based plastic, but also to reduce the
brittleness, shrinkage during molding and production cost of the
PLA-based products. TPS is a material produced mainly from starch
which is cheap, renewable, biodegradable, compostable, and nontoxic.
It is commonly prepared by a plasticization of starch under
applying heat and shear force. Although glycerol has been reported as
one of the most plasticizers used for preparing TPS, its migration
caused the surface stickiness of the TPS products. In some cases,
mixed plasticizers or natural fibers have been applied to impede the
retrogradation of starch or reduce the migration of glycerol. The
introduction of fibers into TPS-based materials could reinforce the
polymer matrix as well. Therefore, the objective of the present
research is to study the effect of starch type (i.e. native starch and
phosphate starch), plasticizer type (i.e. glycerol and xylitol with a
weight ratio of glycerol to xylitol of 100:0, 75:25, 50:50, 25:75 and
0:100) and fiber content (i.e. in the range of 1-25 %wt) on properties
of PLA/TPS blend and composite. PLA/TPS blends and composites
were prepared using a twin-screw extruder and then converted into
dumbbell-shaped specimens using an injection molding machine. The
PLA/TPS blends prepared by using phosphate starch showed higher
tensile strength and stiffness than the blends prepared by using native
one. In contrast, the blends from native starch exhibited higher
extensibility and heat distortion temperature (HDT) than those from
the modified starch. Increasing xylitol content resulted in enhanced
tensile strength, stiffness and water resistance, but decreased
extensibility and HDT of the PLA/TPS blend. Tensile properties and
hydrophobicity of the blend could be improved by incorporating
silane treated-jute fibers.
Abstract: Thermoplastic starch, polylactic acid glycerol and
maleic anhydride (MA) were compounded with natural
montmorillonite (MMT) through a twin screw extruder to investigate
the effects of different loading of MMT on structure, thermal and
absorption behavior of the nanocomposites. X-ray diffraction analysis
(XRD) showed that sample with MMT loading 4phr exhibited
exfoliated structure while sample that contained MMT 8 phr
exhibited intercalated structure. FESEM images showed big lump
when MMT loading was at 8 phr. The thermal properties were
characterized by using differential scanning calorimeter (DSC). The
results showed that MMT increased melting temperature and
crystallization temperature of matrix but reduction in glass transition
temperature was observed Meanwhile the addition of MMT has
improved the water barrier property. The nanosize MMT particle is
also able to block a tortuous pathway for water to enter the starch
chain, thus reducing the water uptake and improved the physical
barrier of nanocomposite.