Epoxidized soybean oil (ESO) is a renewable raw material with abundant resources, low cost, non-toxicity, environmental friendliness, good thermal stability and good solvent resistance. The main components of soybean oil are linoleic acid (51%-57%, mass fraction), oleic acid (32%-36%), palmitic acid (2.4%-2.8%), stearic acid (4.4%-4.6%).
According to statistics, epoxy plasticizers accounted for 8.4% of the plasticizers used in my country in 2020, the second most used among non-collar benzene plasticizers. my country is rich in oil resources and has many varieties, especially the output of soybean oil is in the forefront of the world, which is very beneficial to the development of epoxidized soybean oil. As a commonly used auxiliary plasticizer, epoxidized soybean oil has the advantages of low price, low volatility, less migration, good stability, and resistance to extraction. It has become the second largest plasticizer in developed countries such as Europe and the United States.
Epoxidized soybean oil for TPS/PLA
Blending polylactic acid and thermoplastic starch is a commonly used biodegradable material modification system. However, the poor toughness and difficult processing of TPS/PLA system limit the further application of composite materials. Epoxidized soybean oil (ESO) is an environmentally friendly lipophilic plasticizer and is a commonly used plastic plasticizer, which can effectively improve the comprehensive properties of TPS/PLA composites.
Improve composite compatibility
When no epoxidized soybean oil was added, the samples contained a large number of starch granules, indicating that the plasticizing properties of thermoplastic starch in the composite were poor. With the increase of epoxidized soybean oil content, the number of plasticized starch granules decreased. When the addition amount reaches 8 parts, the compatibility of ESO to the composite material is improved the best, and the starch granules basically disappear. The brittle cross section of the composite material becomes extremely uneven with the continuous addition of epoxidized soybean oil, resulting in a decrease in the performance of the composite material.
Improve the degradation performance of composite materials
The study found that the residual quality of the composite material decreased slightly at different composting times after adding epoxidized soybean oil, and with the increase of the content of epoxidized soybean oil, the residual quality of the composite material was lower at the same composting time. When the soybean oil content is 10 parts, the composite material can be completely decomposed in 210 days. The reason for this phenomenon is that compared with PLA, TPS has a smaller molecular weight and is easier to decompose.
With the increase of epoxidized soybean oil content, the compatibility of thermoplastic starch with PLA is improved, the surface area of the phase interface with PLA is larger, and more colony erosion points are generated. Therefore, it is more easily decomposed by microorganisms. Secondly, thermoplastic starch is also a small molecule adjuvant with biodegradable properties, which can further promote the decomposition of composite materials.
Improve the tensile strength and other properties of composite materials
The study found that the tensile strength of the composite material increased with the increase of the content of epoxidized soybean oil, and reached a maximum value when the content of epoxidized soybean oil was 6 phr. Epoxidized soybean oil can significantly improve the heat resistance and water resistance of the composite material. However, too high content of epoxidized soybean oil will reduce the oil resistance of the composite material. When the ESO content in the composite material is 4-6 phr, the heat resistance, water resistance and oil resistance are the best.
