The effect of citrate ester plasticizers on the thermal and mechanical properties of poly(DL-lactide)

Optimization of the ductile properties of poly(lactic acid) (PLA) using green citrate-based plasticizers and itaconic anhydride grafted PLA (PLA-g-IA)

Certain miscellaneous beans have a low glycemic index (GI) and may reduce the risk of chronic metabolic disorders, including type 2 diabetes and obesity, by modulating postprandial glucose homeostasis and blood lipid levels. In this study, red kidney bean flour and wheat gluten were used as raw materials, and long-chain inulin phosphate monoester (PFXL) was added to improve the quality of red kidney bean dough, prepare high-quality steamed bread, and explore its health effect on type 2 diabetes. The results showed that the addition of PFXL improved the water distribution and rheological properties of coarse grain dough and enriched the flavor of coarse grain steamed bread. In addition, the optimized steamed bread exhibited a low glycemic index (eGI = 51.76), which could reduce fasting blood glucose and glycated serum protein by 21.55 % and 26.11 %, respectively, and could significantly improve oral glucose tolerance and blood lipid levels in diabetic mice and had a certain protective effect on liver injury. Overall, these findings provide a scientific basis for the development of functional foods.

Rational design of PLA-based ASDs for pharmaceutical 3D printing: Insights from phase diagram modeling

The integration of 3D printing into the pharmaceutical sciences opens new possibilities for personalized medicine. Poly(lactide) (PLA), a biodegradable and biocompatible polymer, is highly suitable for biomedical applications, particularly in the context of 3D printing. However, its processability often requires the addition of plasticizers. This study investigates the use of phase diagram modeling as a tool to guide the rational selection of plasticizers and to assess their impact on the thermodynamic and kinetic stability of PLA-based amorphous solid dispersions (ASDs) containing active pharmaceutical ingredients (APIs). Thermodynamic stability against API recrystallization was predicted based on the API solubility in PLA and Plasticizer-PLA carriers using the Conductor-like Screening Model for Real Solvents (COSMO-RS), while the kinetic stability of the ASDs was evaluated by modeling the glass transition temperatures of the mixtures. Two APIs, indomethacin (IND) and naproxen (NAP), with differing glass-forming abilities (i.e., recrystallization tendencies), and three plasticizers, triacetin (TA), triethyl citrate (TEC), and poly(L-lactide-co-caprolactone) (PLCL), were selected for investigation. The physical stability of ASD formulations containing 9 wt% API and plasticizer to PLA in two ratios, 10:81 and 20:71 w/w %, was monitored over time using differential scanning calorimetry and X-ray powder diffraction and compared with phase diagram predictions. All formulations were predicted to be thermodynamically unstable; however, those containing no plasticizer or with TEC and TA at 10 wt% were predicted to exhibit some degree of kinetic stability. Long-term physical studies corroborated these predictions. The correlation between the predicted phase behavior and long-term physical stability highlights the potential of phase diagram modeling as a tool for the rational design of ASDs in pharmaceutical 3D printing.

Recent Approaches to the Plasticization of Poly(lactic Acid) (PLA) (A Review)

Poly(lactic acid) (PLA) is a polyester attracting growing interest every year in different application fields, such as packaging, cosmetics, food, medicine, etc. Despite its significant advantages, it has low elasticity that may hinder further development and a corresponding rise in volume of consumption. This review opens a discussion of basic approaches to PLA plasticization. These considerations include copolymerization and blending with flexible polymers, introducing oligomers and low-molecular additives, as well as structural modification. It was demonstrated that each approach has its advantages, such as simplicity and low cost, but with disadvantages, including complex processing and the need for additional reagents. According to the analysis of different approaches, it was concluded that the optimal option is the application of copolymers as the additives obtained via reactive mixing to PLA and its blends with other polymers.

Improvement of the Ductility of Environmentally Friendly Poly(lactide) Composites with Posidonia oceanica Wastes Plasticized with an Ester of Cinnamic Acid

New composite materials were developed with poly(lactide) (PLA) and Posidonia oceanica fibers through reactive extrusion in the presence of dicumyl peroxide (DCP) and subsequent injection molding. The effect of different amounts of methyl trans-cinnamate (MTC) on the mechanical, thermal, thermomechanical, and wettability properties was studied. The results showed that the presence of Posidonia oceanica fibers generated disruptions in the PLA matrix, causing a decrease in the tensile mechanical properties and causing an impact on the strength due to the stress concentration phenomenon. Reactive extrusion with DCP improved the PO/PLA interaction, diminishing the gap between the fibers and the surrounding matrix, as corroborated by field emission scanning electron microscopy (FESEM). It was observed that 20 phr (parts by weight of the MTC, per one hundred parts by weight of the PO/PLA composite) led to a noticeable plasticizing effect, significantly increasing the elongation at break from 7.1% of neat PLA to 31.1%, which means an improvement of 338%. A considerable decrease in the glass transition temperature, from 61.1 °C of neat PLA to 41.6 °C, was also observed. Thermogravimetric analysis (TGA) showed a loss of thermal stability of the plasticized composites, mainly due to the volatility of the cinnamate ester, leading to a decrease in the onset degradation temperature above 10 phr MTC.

Improving the Processability and Performance of Micronized Fiber-Reinforced Green Composites through the Use of Biobased Additives

Green composites made of bioplastics reinforced with natural fibers have gained considerable attention over recent years. However, the use of natural fibers in composites usually compromise some key properties, such as the impact strength and the processability of the final materials. In the present study, two distinct additives, namely an epoxidized linseed oil (ELO) and a sugar-based surfactant, viz. GlucoPure^® Sense (GPS), were tested in composite formulations of poly(lactic acid) (PLA) or poly(hydroxybutyrate) (PHB) reinforced with micronized pulp fibers. Both additives showed a plasticizing effect, which led to a decrease in the Young’s and flexural moduli and strengths. At the same time, the elongation and flexural strain at break were considerably improved on some formulations. The melt flow rate was also remarkably improved with the incorporation of the additives. In the PHB-based composites, an increment of 230% was observed upon incorporation of 7.5 wt.% ELO and, in composites based on PLA, an increase of around 155% was achieved with the introduction of 2.5 wt.% GPS. ELO also increased the impact strength to a maximum of 29 kJ m⁻², in formulations with PLA. For most composites, a faster degradation rate was observed on the formulations with the additives, reaching, in the case of PHB composites with GPS, a noteworthy weight loss over 75% under burial testing in compost medium at room temperature.

Plasticization of Polylactide after Solidification: An Effectiveness and Utilization for Correct Interpretation of Thermal Properties

Polylactide/triethyl citrate (PLA/TEC) systems were prepared in two ways by introducing TEC to solidified polymer matrix (SS) and by blending in a molten state (MS) to investigate the effectiveness of the plasticization process after solidification of polylactide. The plasticization processes, independently of way of introducing the TEC into PLA matrix, leads to systems characterized by similar stability, morphology and properties. Some differences in mechanical properties between MS and SS systems result primarily from the difference in the degree of crystallinity/crystal thickness of the PLA matrix itself. Based on the presented results, it was concluded that the plasticization process after solidification of polylactide is an alternative to the conventional method of modification-blending in a molten state. Then, this new approach to plasticization process was utilized for interpretation of thermal properties of PLA and PLA/TEC systems. It turned out that double melting peak observed at DSC thermograms does not result from the melting of a double population of crystals with different lamellar thickness, or the melting of both the α' and α crystalline phase (commonly used explanations in literature), but is associated with the improvement of perfection of crystalline structure of PLA during heating process.

Combined Effects of Drugs and Plasticizers on the Properties of Drug Delivery Films

Formation of scar tissue may be reduced or prevented if wounds were locally treated with a combination of molecules tuned to the different healing phases, guiding tissue regeneration along a scar free path. To this end, drug delivery devices made of cellulose acetate phthalate and Pluronic F-127 were loaded with either quercetin or pirfenidone and plasticized with either triethyl citrate (TEC) or tributyl citrate (TBC). Quercetin inhibits oxidative stress, and pirfenidone has been shown to reduce production of pro-inflammatory and fibrogenic molecules. The combined effects of drug and plasticizer on erosion, release, and mechanical properties of the drug delivery films were investigated. TEC-plasticized films containing quercetin released drug at a slower rate than did TBC films. Pirfenidone-loaded films released drug at a faster rate than erosion occurred for both types of plasticizers. Higher plasticizer contents of both TEC and TBC increased the elongation and decreased the elastic modulus. In contrast, increased pirfenidone loading in both TEC and TBC films resulted in a significantly higher modulus, an anti-plasticizer effect. Adding pirfenidone significantly decreased elongation for all film types, but quercetin-loaded samples had significantly greater elongation with increasing drug content. Films containing quercetin elongated more than did pirfenidone-loaded films. Quercetin is over 1.5 times larger than pirfenidone, has water solubility over 12 times lower, and has 6 times more bonding sites than pirfenidone. These differences affected how the two drugs interacted with cellulose acetate phthalate and Pluronic F-127 and thereby determined polymer properties. Drug release, erosion, and mechanical properties of association polymer films can be tailored by the characteristics of the drugs and plasticizers included in the system.

Plasticizing effects of citrate esters on properties of poly(lactic acid)

Triethyl citrate (TEC) and acetyl tributyl citrate (ATBC) were used as plasticizer for poly(lactic acid) (PLA). The treated and plasticized PLA at various concentrations were analyzed by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and opacity. DSC was used to evaluate the crystallinity and thermal property of all the samples. It was found that the glass transition temperature (Tg) and the melting temperature (Tm) decreased as the amount of citrate esters increased. Additionally, the presence of TEC or ATBC tended to increase the crystallinity of PLA. This result was supported by XRD. DMA of plasticized PLA indicates that a decrease in Tg is obtained with increasing plasticizer content. FTIR spectra indicate that there are some molecular interactions by intermolecular hydrogen bonds between PLA and citrate esters. The effect of the concentration of plasticizer on the opacity of the films was negligible.