Tailoring the Properties of Thermo-Compressed Polylactide Films for Food Packaging Applications by Individual and Combined Additions of Lactic Acid Oligomer and Halloysite Nanotubes

Abstract

In this work, films of polylactide (PLA) prepared by extrusion and thermo-compression were plasticized with oligomer of lactic acid (OLA) at contents of 5, 10, and 20 wt%. The PLA sample containing 20 wt% of OLA was also reinforced with 3, 6, and 9 parts per hundred resin (phr) of halloysite nanotubes (HNTs) to increase the mechanical strength and thermal stability of the films. Prior to melt mixing, ultrasound-assisted dispersion of the nanoclays in OLA was carried out at 100 • C to promote the HNTs dispersion in PLA and the resultant films were characterized with the aim to ascertain their potential in food packaging. It was observed that either the individual addition of OLA or combined with 3 phr of HNTs did not significantly affect the optical properties of the PLA films, whereas higher nanoclay contents reduced lightness and induced certain green and blue tonalities. The addition of 20 wt% of OLA increased ductility of the PLA film by nearly 75% and also decreased the glass transition temperature (T g ) by over 18 • C. The incorporation of 3 phr of HNTs into the OLA-containing PLA films delayed thermal degradation by 7 • C and additionally reduced the permeabilities to water and limonene vapors by approximately 8% and 47%, respectively. Interestingly, the highest barrier performance was attained for the unfilled PLA film plasticized with 10 wt% of OLA, which was attributed to a crystallinity increase and an effect of "antiplasticization". However, loadings of 6 and 9 phr of HNTs resulted in the formation of small aggregates that impaired the performance of the blend films. The here-attained results demonstrates that the properties of ternary systems of PLA/OLA/HNTs can be tuned when the plasticizer and nanofiller contents are carefully chosen and the resultant nanocomposite films can be proposed as a bio-sourced alternative for compostable packaging applications.

On the Use of Phenolic Compounds Present in Citrus Fruits and Grapes as Natural Antioxidants for Thermo-Compressed Bio-Based High-Density Polyethylene Films

“…Bio-HDPE films were obtained by thermo-compression of the melt-compounded pellets using a 10-ton hydraulic press from Robima S.A. (Valencia, Spain) equipped with two hot aluminum plates and a temperature controller from Dupra S.A. (Castalla, Spain) [ 30 ]. The process was carried out at 130 °C, in which approximately 5 g of pellets were placed between the two hot plates and a pressure of 40 MPa was applied for 3 min.…”

“…Summary of compositions according to the weight (wt%) of bio-based high-density polyethylene (bio-HDPE) in which naringin (NAR), gallic acid (GA), caffeic acid (CA), and quercetin (QUER) were added as parts per hundred resin (phr) of bio-HDPE. Bio-HDPE films were obtained by thermo-compression of the melt-compounded pellets using a 10-ton hydraulic press from Robima S.A. (Valencia, Spain) equipped with two hot aluminum plates and a temperature controller from Dupra S.A. (Castalla, Spain) [30]. The process was carried out at 130 • C, in which approximately 5 g of pellets were placed between the two hot plates and a pressure of 40 MPa was applied for 3 min.…”

Assessment of the Mechanical and Thermal Properties of Injection-Molded Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)/Hydroxyapatite Nanoparticles Parts for Use in Bone Tissue Engineering

“…Testing was performed under inert atmosphere using a nitrogen flow of 50 mL/min. The degree of crystallinity ( X C_max ) was calculated using Equation (1) [ 37 ]: where ∆ H m (J/g) corresponds to the melting enthalpy of P(3HB- co -3HHx), ∆ H m 0 (J/g) is the theoretical value of a fully crystalline of P(3HB- co -3HHx), taken as 146 J/g [ 38 ], an 1 − w indicates the weight fraction of P(3HB- co -3HHx) in the sample.…”

Torrefaction of Coffee Husk Flour for the Development of Injection-Molded Green Composite Pieces of Polylactide with High Sustainability

“…In fact, the lower T m values attained at the highest contents, that is, 40 wt% and 50 wt% of TCHF, in combination with the higher ∆H cc values, suggest that the biopolymer chains were immobilized onto the surface of the lignocellulosic fillers. The maximum degree of crystallinity, that is, X C_max , which does not consider the crystals that are formed during cold crystallization [50], increased progressively up to a TCHF content of 30 wt% and then slightly lower values were observed. This result indicates that the lignocellulosic fillers induced a nucleating effect that favored the formation of crystals in the green composites.…”