Effect of the Addition of Different Natural Waxes on the Mechanical and Rheological Behavior of PLA-A Comparative Study.

In this study, poly(lactic acid) (PLA) blended with different natural waxes (beeswax, candelilla, carnauba, and cocoa) was investigated. Different wax amounts, 3, 5, 10, and 15 wt%, were incorporated into the PLA using a Brabender internal mixer. The blends were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), rotational rheometer (RR), dynamic mechanical analysis (DMA), and contact angle to observe the effect of the different waxes on the PLA physicochemical, rheological, mechanical behavior, and wetting properties. The complex viscosity of the blends was studied by employing a RR. The effect of the addition of the waxes on the mechanical properties of PLA was evaluated by DMA in the tension modality. A slight decrease in the thermal stability of PLA was observed with the addition of the waxes. However, in the case of the mechanical properties, the cocoa wax showed a considerable effect, especially in the elongation at break of PLA. Likewise, waxes had an essential impact on the water affinity of PLA. Specifically, with the addition of cocoa, the PLA became more hydrophilic, while the rest of the waxes increased the hydrophobic character.

Progress of Polyaniline Glucose Sensors for Diabetes Mellitus Management Utilizing Enzymatic and Non-Enzymatic Detection.

Glucose measurement is a fundamental tool in the daily care of Diabetes Mellitus (DM) patients and healthcare professionals. While there is an established market for glucose sensors, the rising number of DM cases has promoted intensive research to provide accurate systems for glucose monitoring. Polyaniline (PAni) is a conductive polymer with a linear conjugated backbone with sequences of single C-C and double C=C bonds. This unique structure produces attractive features for the design of sensing systems such as conductivity, biocompatibility, environmental stability, tunable electrochemical properties, and antibacterial activity. PAni-based glucose sensors (PBGS) were actively developed in past years, using either enzymatic or non-enzymatic principles. In these devices, PAni played roles as a conductive material for electron transfer, biocompatible matrix for enzymatic immobilization, or sensitive layer for detection. In this review, we covered the development of PBGS from 2015 to the present, and it is not even exhaustive; it provides an overview of advances and achievements for enzymatic and non-enzymatic PBGB PBGS for self-monitoring and continuous blood glucose monitoring. Additionally, the limitations of PBGB PBGS to advance into robust and stable technology and the challenges associated with their implementation are presented and discussed.

Stiff-Elongated Balance of PLA-Based Polymer Blends.

In this study, polymer blends with a mechanical property balance based on poly(lactic acid) (PLA), stiff polymer, and elongated polymer were developed. First, the binary blends PLA-elongated polymer [ethyl vinyl acetate (EVA) or polyethylene], or PLA-stiff polymer [polystyrene or poly(styrene-co-methyl methacrylate) (SMMA)] blends were studied using dynamic mechanic analysis (DMA) and analyzed using Minitab statistical software to determine the factors influencing the elongation or stiffness of the blends. Then, ternary blends such as elongation-poly(lactic acid)-stiff, were made from the binary blends that presented optimal performance. In addition, three blends [EVA-PLA-SMMA (EPS)] were elaborated by studying the mixing time (5, 15, and 15 min) and the added time of the SMMA (0, 0, and 10 min). Specifically, the mixing time for EPS 1, EPS 2, and EPS 3 is 5 min, 15 min, and 15 min (first EVA + PLA for 10 min, plus 5 min PLA-EVA and SMMA), respectively. Mechanical, thermal, rheological, and morphological properties of the blends were studied. According to DMA, the results show an increase in elongation at break (εb) and do not decrease the elastic module of poly(lactic acid). Nevertheless, EPS 3 excels in all properties, with an εb of 67% and modulus of elasticity similar to PLA. SMMA has a significant role as a compatibilizing agent and improves PLA processability.

Thermoplastic Starch-Based Blends with Improved Thermal and Thermomechanical Properties.

This research focused on the development of biomaterials based on cassava starch and corn starch and on the effect of the incorporation of polycaprolactone (PCL) on the thermal and thermomechanical properties of the blends. The results indicated partial compatibility in the blends, especially with cassava starch at a content of 20 wt% as reflected by the maintenance of tensile strength and elongation. In addition, the changes in the crystal quality of PCL and the displacement of the absorption bands of the carbonyl groups of PCL in the infrared (989-1000 cm-1), attributed to the formation of hydrogen bonds between these groups and the hydroxyl groups of starches, were also associated with compatibility. It was observed that the crystallinity of PLC in the presence of cassava and corn starch was 38% and 62%, respectively; a crystallinity greater than that of PCL was related to an improved nucleation at the interface. Based on these properties, the blends are expected to be functional for the manufacture of short-term use products by conventional thermoplastic processing methods.