Molecular design of environmental friendly green plasticizers

Abstract

<p indent="0mm">Plasticizers are substances that can increase the plasticity and processibility of the polymer materials. Plasticizer is one of the largest chemical additives for plastic processing industry, which can effectively improve its processing performance and has great economic and social significance. Ideal plasticizer should have good compatibility with the polymer. It should have high plasticization efficiency and light, heat, weather resistance. Low volatility, slow migration rate, excellent electrical insulation, non-toxicity, being odorless, tasteless and colorless, excellent stain resistance as well as being cheap and easily available are desirable properties ideal plasticizer would have. Among thousands of compounds that being able to be taken as plasticizers, there are only less than 100 kinds that subjecting to wide application. Phthalic acid esters plasticizers (such as dibutyl phthalate, dioctyl phthalate) are used in the largest amount. The advantages and disadvantages of the main commercial plasticizers are analyzed, especially phthalate plasticizers. However, recently phthalate plasticizers have been restricted in many countries and regions due to their toxic side effects and impacts on human health and environment. Some phthalate plasticizers can kill soil and aquatic organisms when they degrade into relatively persistent toxic metabolites. By designing green plasticizers, researchers are finding alternatives to conventional plasticizers that may alleviate health concerns. In this review, the research progress of environmental friendly green plasticizers is summarized from the molecular design perspective. Firstly, the working principle of plasticizer is elucidated and the lubrication theory, gel theory and free volume theory are discussed. The basic working mechanism is the insertion of the plasticizer molecules between the chains of polymers, making the interaction between polymer chains weakened, and thus decrease the aggregation of molecular chains, and increase the movement property, softness of molecular chains, making the plastic materials more easily to be processed. Polar plasticizer can weak the polarization effect between polar polymer chains and the non-polar plasticizer can increase the space volume between polymer chains. Environmental friendly green plasticizers are alternative solution to gradually replace traditional petroleum based plasticizers in the future. Bio-based plasticizers with renewable resources have attracted significant attention. These plasticizers have the advantages of renewable, easily degradable, non-toxic, and migration resistance, and are promising substitutes for phthalate plasticizers. This review summarizes the latest research progress of plant oil based plasticizers such as soybean oil and castor oil. The distinctive structure and property features of hyperbranched polyester plasticizers (such as adipic acid type and ε-caprolactone type polyester plasticizers) are described. In addition, due to the unique structure, hyperbranched polyester plasticizers have strong anti-migration ability and play an important role in applications that require high migration resistance, such as children’s products, food packaging and medicine. Specific examples of design and application of plasticizers based on cashew phenol, waste edible oil, lactic acid, rosin and tartaric acid are highlighted. Finally, the relationship between chemical structure and properties of plasticizer is analyzed. It is proposed that molecular design will be promising approach for novel plasticizer design. The replacement of petroleum-based plasticizers with bio-based environmental friendly green plasticizers is the future direction in plastic industrial. This review analyzes the relationship between the characteristic molecular motifs and properties and performances of plasticizer. The approach and perspectives of designing next generation of plasticizers are proposed and future trend and outlook are predicted.