Biodegradable Hydrogenated Dimer Acid-Based Plasticizers for PLA with Excellent Plasticization, Thermal Stability and Gas Resistance.

The use of vegetable oil-dervied plasticizers to enhance the flexibility of polylactic acid (PLA) has received much attention due to their renewability, inexpensiveness and biodegradation. However, the double bonds in vegetable oil-based plasticizers limit their compatibility with PLA, resulting in PLA-derived products with reduced flexibility. Herein, we examined soybean oil-derived hydrogenated dimer acid-based polyethylene glycol methyl ether esters (HDA-2n, 2n = 2, 4, 6 or 8, referring to the ethoxy units) developed via the direct esterification of saturated hydrogenated dimer acid and polyethylene glycol monomethyl ethers. The resulting HDA-2n was first used as a plasticizer for PLA, and the effects of the ethoxy units in HDA-2n on the overall performance of the plasticized PLA were systematically investigated. The results showed that, compared with PLA blended with dioctyl terephthalate (DOTP), the PLA plasticized by HDA-8 with the maximum number of ethoxy units (PLA/HDA-8) exhibited better low-temperature resistance (40.1 °C vs. 15.3 °C), thermal stability (246.8 °C vs. 327.6 °C) and gas barrier properties. Additionally, the biodegradation results showed that HDA-8 could be biodegraded by directly burying it in soil. All results suggest that HDA-8 could be used as green alternative to the traditional petroleum-based plasticizer DOTP, which is applied in the PLA industry.

Experimental and numerical study on Cu and Cd migration in different functional-area soils under simulated rainfall conditions.

Natural rainfall exerts a significant influence on the migration of heavy metals in soil. However, the knowledge of migration characteristics and release kinetics of heavy metals in contaminated soils under different rainfall intensities still remains unclear. In this study, the simulated rainfall of different intensities was designed to experimentally and numerically investigate Cu and Cd movements in different functional-area (agriculture, industrial, urban) soils. A HYDRUS-2D model was optimized to simulate the migration process of Cu and Cd in soil under different rainfall conditions. The hydraulic properties and solute transport parameters used in the model were estimated based on isothermal adsorption and chloride ion penetration experimental measurements and related model fitting. Furthermore, Cu and Cd BTCs (Breakthrough Curves) were fitted using the HYDRUS-2D inverse solution function with two-site model. The results showed that the order of the migration capacity of Cu and Cd in different functional-area soils was agriculture soil > industrial soil > urban soil, and Cd had a greater risk of groundwater pollution than Cu. With the increase of rainfall intensity, the high proportion of the exchangeable state of Cu and Cd in contaminated soil is easy to be released. Furthermore, the model was proved to describe the distribution of Cu and Cd in the soil profile very well. The present results can improve understanding of the environmental behavior of Cu and Cd in different functional-areas soils and can be used as a basis for risk assessment of Cu and Cd polluting groundwater.

Cellulose-based polypropoxy ether carboxylates as highly compatible, effective, and migration-resistant plasticizers for poly (lactic acid).

The utilization of cellulose for enhancing the strength, the PLA has received significant attention, however, poor interfacial compatibility of solid cellulose with PLA matrix still hinders their broader application. Herein, highly compatible cellulose-based polypropoxy ether carboxylates (CPPEC) were firstly manufactured via propoxylation of cellulose and following esterification with acetic acid, butyric acid, as well as oleic acid, respectively. Liquid CPPEC delivered excellent performances to PLA, especially, the values of elongation at break and low-temperature resistance of PLA blended with cellulose-based polypropoxy ether acetate (PLA/CPPEA) were respectively increased by 630.9 % and 146.3 % compared with those of neat PLA due to the synergistic effect of propyl and methyl groups in CPPEC with PLA matrix. Additionally, migration resistance of PLA/CPPEA increased 14.3 and 11.2 times, respectively, compared with those of PLA specimens blended with epoxidized soybean oil and dioctyl phthalate. All findings suggest that the CPPEC is suitable for large-scale application in the PLA industry.