Juliana Bonametti Olivato

Effect of organic acids as additives on the performance of thermoplastic starch/polyester blown films.

The influence of citric acid (CA), malic acid (MA) and tartaric acid (TA) in starch/poly (butylene adipate co-terephthalate) blown films was evaluated by examining the barrier, structural and mechanical properties of the films. These properties were analysed in different relative humidities. Greater concentrations of TA and CA (1.5 wt%) produced films with improved tensile strength (6.8±0.3 and 6.7±0.3 MPa, respectively), reduced water vapour permeability and a more homogeneous structure. The compatibilising effect of MA was less efficient, as shown in the scanning electron microscopy (SEM) images. Changes in the relative humidity (RH) affected the elongation of the films, which reached values of 5.7±0.5 at 33% RH and increased to 312.4±89.5% at 53% RH. The FT-IR spectra showed no additional reactions caused by the incorporation of the additives, and the observed results are attributed to the esterification reactions and/or hydrolysis of the starch, producing films with interesting properties. This process represents an alternative to the use of non-biodegradable materials.

Mixture design applied for the study of the tartaric acid effect on starch/polyester films.

Tartaric acid (TA), a dicarboxylic acid, can act as a compatibiliser in starch/polyester blends. A mixture design was proposed to evaluate the effect of TA on the properties of starch/poly (butylene adipate co-terephthalate) (PBAT) blown films plasticised with glycerol. The interaction between the starch/PBAT and the TA has a positive effect on the tensile strength and puncture force. Additionally, greater proportions of TA increased Youngs modulus. The starch+PBAT/TA and Gly/TA interactions contributed to a reduction in the water vapour permeability of the films. The inclusion of TA did not change the crystallinity of the samples. Formulations with intermediate proportions of TA (0.8 g/100 g) were shown to produce the best compatibilising effect. This was observed by DMA analysis as a consequence of the perfect equilibrium between the contributions of TA as a compatibiliser and in the acidolysis of starch, resulting in films with a tensile strength of 5.93 MPa, a possible alternative to non-biodegradable packaging.

Thermoplastic starch/polyester films: Effects of extrusion process and poly (lactic acid) addition

Biodegradable films were produced using the blown extrusion method from blends that contained cassava thermoplastic starch (TPS), poly(butylene adipate-co-terephthalate) (PBAT) and poly(lactic acid) (PLA) with two different extrusion processes. The choice of extrusion process did not have a significant effect on the mechanical properties, water vapor permeability (WVP) or viscoelasticity of the films, but the addition of PLA decreased the elongation, blow-up ratio (BUR) and opacity and increased the elastic modulus, tensile strength and viscoelastic parameters of the films. The films with 20% PLA exhibited a lower WVP due to the hydrophobic nature of this polymer. Morphological analyses revealed the incompatibility between the polymers used.

Physical and structural characterisation of starch/polyester blends with tartaric acid

Starch/PBAT blends were produced by reactive extrusion with tartaric acid (TA) as an additive. The effects of TA, glycerol and starch+PBAT on the mechanical, optical and structural properties of the films were evaluated, with formulations based in a constrained mixture design. Tartaric acid acts as a compatibiliser and promotes the acid hydrolysis of starch chains. These two functions explain the observed film resistance and opacity. TA reduced the weight loss in water. Scanning electron microscopy (SEM) images showed that TA reduces the interfacial tension between the polymeric phases, resulting in more homogeneous films. Nuclear magnetic resonance ((13)C CPMAS) and Fourier transform infrared spectroscopy (FT-IR) suggest that tartaric acid is able to react with the hydroxyl groups of the starch by esterification/transesterification reactions, confirming its role as a compatibiliser. The addition of TA results in materials with better properties that are suitable for use in food packaging.

Using glycerol produced from biodiesel as a plasticiser in extruded biodegradable films

The demand for renewably sourced biodegradable materials has increased the need to produce materials that combine appropriate functional properties at competitive costs. Thermoplastic starch and polyester blends are an interesting alternative to current materials due to the low cost of starch and the functional properties and processability of the resulting blends. Producing thermoplastic starch (TPS) requires using a plasticiser at concentrations between 20 and 30%wt (in relation to starch). Glycerol is the most common plasticiser due to its high plasticising capacity and thermal stability at processing temperatures. The objective of this study was to evaluate glycerol waste from the biodiesel industry, with different degrees of purification, as plasticisers for TPS / poly (butylene adipate-co-terephthalate) (PBAT) blends. Different purities of glycerol produced films with similar mechanical, optical and barrier properties to those made with purified glycerol (99.7%). Therefore, crude glycerol is a renewable alternative plasticiser that reduces the cost of plasticisation by 6-fold.

Starch/polyester films: simultaneous optimisation of the properties for the production of biodegradable plastic bags

Blends of starch/polyester have been of great interest in the development of biodegradable packaging. A method based on multiple responses optimisation (Desirability) was used to evaluate the properties of tensile strength, perforation force, elongation and seal strength of cassava starch/poly(butylene adipate-co-terephthalate) (PBAT) blown films produced via a one-step reactive extrusion using tartaric acid (TA) as a compatibiliser. Maximum results for all the properties were set as more desirable, with an optimal formulation being obtained which contained (55:45) starch/PBAT (88.2 wt. (%)), glycerol (11.0 wt. (%)) and TA (0.8 wt. (%)). Biodegradable plastic bags were produced using the film with this formulation, and analysed according to the standard method of the Associacao Brasileira de Normas Tecnicas (ABNT). The bags exhibited a 45% failure rate in free-falling dart impact tests, a 10% of failure rate in dynamic load tests and no failure in static load tests. These results meet the specifications set by the standard. Thus, the biodegradable plastic bags fabricated with an optimised formulation could be useful as an alternative to those made from non-biodegradable materials if the nominal capacity declared for this material is considered.

Sensibilidade ao rachamento de bagas das videiras 'Concord', 'Isabel' e 'BRS Rúbea'

In order to evaluate the sensitivity of fruit cracking, different laboratory tests were performed in grape berries of the processing varieties Concord, Isabel and BRS Rubea. To determine the cracking index, ripe berries were dipped in distilled water and evaluated every hour during a period of ten hours. Mechanical tests were performed using a texturometer. In compression tests, at the cracking time, pressing pressure, strain energy, maximum force of compression and compression strain were evaluated. With a smaller diameter probe, berries were drilled to the breakup of the skin resulting in maximum force of drilling and drilling strain. In stress relaxation tests the degree of solidity and initial stress decay rate were evaluated. The correlations between the cracking index and mechanical testing were evaluated too. Both the cracking index and mechanical testing pointed to the BRS Rubea as the most resistant to cracking and the Concord cultivar as the most susceptible. Isabel presented intermediate resistance. The cracking index showed strong correlation with the parameters evaluated in the mechanical tests and has good potential for assessing the sensitivity to cracking of different grape cultivars.

Biodegradable bags for the production of plant seedlings

The production of plant seedlings has traditionally used polyethylene bags, which are thrown out in the soil or burned after transplant because the large amount of organic material attached to the bags makes recycling difficult. Additionally, when a seedling is taken from the bag for transplant, there is the risk of root damage, which compromises the plants development. In this study, we developed biodegradable bags to be used in seedling production, and we verify their influence on the development of Brazilian ginseng (Pfaffia glomerata (Spreng) Pedersen), when the plant is planted without being removed from the bag. Both black and white biodegradable bags remained intact throughout the seedling production period (60 days). After being transplanted into containers (240 days), they were completely biodegraded, and there was no significant difference between the dry mass of these plants and that of plants that were transplanted without the bags. The plants that were cultivated without being removed from the polyethylene bags had root development difficulties, and the wrapping showed no signs of degradation. The use of biodegradable films is an alternative for the production of bags for seedlings, as these can then be transplanted directly into the soil without removing the bag, reducing the risk of damage to the roots during the moment of transplant.

Poly(lactic acid)/thermoplastic starch sheets: effect of adipate esters on the morphological, mechanical and barrier properties

Blends of poly(lactic acid) (PLA) and thermoplastic starch (TPS) plasticized with adipate esters (diisodecyl adipate and diethyl adipate) having different molecular weight were used to produce sheets. The calendering-extrusion process at a pilot scale was used, and the mechanical, barrier, and morphological characterization of the obtained materials were performed. The increase in the TPS content affected the mechanical properties of the sheets by increasing the elongation and decreasing the rigidity. TPS conferred a more hydrophilic character to the sheets, as observed from the water vapor permeability results. The sheets plasticized with diisodecyl adipate (DIA), having a higher molecular weight, had better mechanical and barrier properties than diethyl adipate (DEA) plasticized sheets, indicating that DIA was more effective as plasticizer. Micrographs obtained by confocal laser microscopy and scanning electron microscopy showed different morphologies when different proportions of PLA and TPS were used (dispersed or co-continuous structures), which were strongly associated with the mechanical and barrier properties.

Influence of microcrystalline cellulose in thermoplastic starch/polyester blown films

). The films were characterised for their mechanical, structural and barrier properties. Increasing fibres concentration reduced the tensile strength (6.9 to 4.6 MPa), the elongation at break (568 to 147%) and weight loss in water (12.8 to 11.1%) of the films. The rigidity of the films increased from 19.8 MPa (without MCC) to 79.2 MPa in the samples with 10 g.100 g