Any substance that can increase the plasticity of plastic by adding it to plastic can be called a plastic plasticizer.

Introduction

The main function of plasticizers is to weaken the secondary bond between polymer molecules, namely the van der Waals force, thereby increasing the mobility of polymer molecular chains and reducing the crystallinity of polymer molecular chains, that is, increasing the plasticity of polymers, which is manifested in the decrease of hardness, modulus, softening temperature and brittle temperature of polymers, while the elongation, flexibility and toughness are improved.

Plastic plasticizers can be divided into two major types according to their mode of action, namely internal plasticizers and external plasticizers.

Internal plasticizers are actually part of polymers. Generally, internal plasticizers are the second monomers introduced during the polymerization process of polymers. Since the second monomer is copolymerized in the molecular structure of the polymer, the regularity of the polymer molecular chain is reduced, that is, the crystallinity of the polymer molecular chain is reduced. For example, vinyl chloride-vinyl acetate copolymer is softer than vinyl chloride homopolymer. The use temperature range of internal plasticizers is relatively narrow, and they must be added during the polymerization process, so internal plasticizers are used less.

An external plasticizer is a low molecular weight compound or polymer. When added to a polymer that needs plasticization, it can increase the plasticity of the polymer. External plasticizers are generally a high-boiling, less volatile liquid or a low-melting-point solid, and most of them are ester organic compounds. Usually they do not react chemically with polymers, and their interaction with polymers is mainly swelling at elevated temperatures, forming a solid solution with the polymer. External plasticizers have comprehensive properties and are easy to produce and use, so they are widely used. The plasticizers people generally refer to are external plasticizers. Dioctyl phthalate (DOP) and dibutyl phthalate (DBP) are both external plasticizers.

An ideal plasticizer should have the following properties: (1) good compatibility with resin; (2) high plasticizing efficiency; (3) stable to heat and light; (4) low volatility; (5) low migration; (6) resistant to extraction of water, oil and organic solvents; (7) good low-temperature flexibility; (8) good flame retardancy; (9) good electrical insulation; (10) colorless, odorless and non-toxic; (11) good mold resistance; (12) good pollution resistance; (13) good viscosity stability of plasticizer paste; (14) low price.

Development

Plasticizers are the largest category of plastic additives in terms of quantity, output and consumption. By 2012, the global total plasticizer production capacity was about 7.5 million tons/year, and the global total plasticizer output was 5.9 million tons/year, of which North America accounted for 22%, Asia-Pacific accounted for 38%, Europe accounted for 25%, and other regions accounted for 15%. PVC is the largest user of plasticizers, accounting for 95% of the total global plasticizer usage, and slightly more than 90% in North America. Polyolefins, styrenes, engineering plastics, polyvinyl butyral and cellulose use very little plasticizer. In the plasticizer market, phthalates account for the majority, accounting for 69%, followed by aliphatics at 8%, epoxies at 7%, trimellitates at 4%, and others at 2%.

Because plasticizers are closely related to the very mature soft PVC market, they have developed slowly, but have maintained a steady growth momentum and are expected to grow at an average annual rate of 2.5%, reaching 6.1 million tons in 2009.

Plasticizer production trends are developing towards large-scale, continuous, and microcomputer-controlled production, with a single set of production capacity reaching more than 100,000 tons/year. Multi-variety serial production has the characteristics of strong market adaptability and great production flexibility to meet the needs of different plastic processing products for special functional plasticizer varieties. Due to its better cost-effectiveness, DOP still occupies a leading position in the production and consumption of phthalates, followed by DINP (diisononyl phthalate) and DIDP (diisodecyl phthalate). In addition, the development of straight-chain alcohol esters is also very fast and is expected to become an important variety of phthalates. In addition to phthalate plasticizers, fatty acid esters with excellent cold resistance, epoxy esters with strong non-toxic stability, trimellitic acid esters with high temperature resistance, polyesters without migration, and phosphate esters with good flame retardancy all account for a certain proportion in the plasticizer structure, forming a rationally structured plasticizer production system.

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