Plastics are everywhere, shaping our world in countless ways. But did you know that many of the properties we love about plastics—their flexibility, durability, and ease of processing—are thanks to a special type of additive called a plasticizer?
The Secret to Soft and Supple Plastics:
Plasticizers are the unsung heroes of the plastics industry. These essential additives work by softening and increasing the flexibility of rigid polymers, making them easier to process and use. They’re found in countless products, from food packaging to medical devices, and even in the coatings on your car.
A Shift Towards Sustainability:
For years, the most common plasticizers were phthalates, but concerns about their potential health effects have spurred a major shift towards safer, more sustainable alternatives. Enter high-molecular plasticizers—the next generation of these essential additives.
High-Molecular Plasticizers: The Green Solution:
High-molecular plasticizers offer several key advantages:
- Superior Plasticizing Power: They provide excellent flexibility and processability, often exceeding the performance of traditional phthalates.
- Enhanced Durability: They create plastics that are more resistant to wear and tear, extending the lifespan of products.
- Environmental Friendliness: They are designed to be safer for both people and the planet.
Meet the Stars:
Several types of high-molecular plasticizers are making waves:
- Polyester Plasticizers: Offering excellent performance and compatibility with various polymers.
- Liquid Nitrile Rubber: Known for its excellent oil and solvent resistance.
- PNBR: Providing a combination of flexibility, durability, and environmental friendliness.
The Future is Flexible and Sustainable:
High-molecular plasticizers are rapidly gaining popularity, driven by the increasing demand for safer and more sustainable plastics. They are revolutionizing the plastics industry, making it possible to create high-performance materials with a reduced environmental footprint.
A Greener Future for Plastics:
The development of high-molecular plasticizers represents a significant step forward in the quest for safer and more sustainable plastics. These innovative materials are paving the way for a future where plastics are both flexible and environmentally responsible.
Plasticizers are the most commonly used types of plastic additives. The main function of plasticizer is to weaken the secondary valence bonds between resin molecules, increase the mobility of resin molecular bonds, reduce the crystallinity of resin molecules, increase the plasticity of resin molecules, make them more flexible, easy to process, and can be used legally Industrial use, widely used in food packaging, cosmetics, medical equipment, etc.
Among traditional plasticizers, o-phenyl esters are used in the largest amount, accounting for about 80% of the total plasticizer production . However, in recent years, it has been discovered that o-benzene plasticizers may cause cancer . Europe, the United States, Japan, and South Korea have enacted laws to restrict their application in areas related to human health.
At present, people have developed a variety of environmentally friendly plasticizers, and the ideal ones include the following varieties: epoxy plasticizers, polymer plasticizers, citrate plasticizers , etc. The following mainly introduces polymer plasticizers.
Compared with small molecule plasticizers, polymer plasticizers not only have a good plasticizing effect, but also have excellent resistance to extraction. There are many types of polymer plasticizers, including polyester plasticizer , liquid nitrile rubber (LNBR) , powder nitrile rubber (PNBR) , ethylene – vinyl acetate – carbon monoxide terpolymer (EVA-CO) and Ethylene – n- butyl acrylate – carbon monoxide terpolymer (EnBA-CO) , etc. In some situations where oil resistance and solvent resistance are required, such as when in contact with food and medicine, polymer plasticizers can be used instead of commonly used small molecule plasticizers.
1. Polyester plasticizer
Polyester plasticizer is an early-used polymer plasticizer with a molecular weight of around 3000. It is mainly made from dibasic acids and diols through condensation reactions . Common types include adipic acid polyester and phthalic anhydride. Polyesters, etc., among which adipic acid polyester has the largest variety, and propylene glycol adipate polyester is the most important.
Different from ordinary plasticizers, polyester plasticizers have good durability, weather resistance, migration resistance and oil resistance due to their higher average molecular weight. Commonly used in PVC and other polar materials. It does not contain any o-benzene and is an environmentally friendly plasticizer.
Compared with benzene plasticizers such as DOP , DINP and DOTP , polyester plasticizers have excellent weather resistance, precipitation resistance and migration resistance. Due to its high molecular weight, polyester plasticizers have strong stability against various oils and solvents and are not easy to precipitate and extract, thus extending the service life of the product.
Polyester plasticizer used in PVC can reduce the migration of small molecule plasticizers in soft PVC and improve the processing performance of PVC . It is suitable for oil-resistant, water-resistant and solvent-resistant plastic products such as leather, toys, medicine and food, etc. industry, the addition amount can reach 70% when used in soft PVC .
Relative molecular weight and degree of branching affect the plasticizing effect of polyester plasticizer . As the relative molecular weight of polyester plasticizer increases, the glass transition temperature of soft PVC decreases, and the plasticizing effect, heat resistance, and solvent resistance increase. The increase in branching degree of polyester plasticizer also improves the heat resistance of soft PVC .
Polyester plasticizer is used in rubber products. It can give rubber vulcanization heat resistance, oil resistance, swelling resistance and migration resistance, and can improve the processing performance of rubber materials , such as reducing the viscosity of rubber materials and improving the resilience of vulcanization. And elongation, the tensile strength and tear strength of the rubber are reduced less, and it is often used in styrene – butadiene rubber and nitrile rubber products.
In EVA-VC graft copolymer resin, polyester plasticizer can be used as a hard modifier and used in the formulation of special-shaped materials such as PVC doors and windows. Add 6 to 10 parts of polyester plasticizer as an auxiliary agent. Finally, its products have excellent weather resistance and impact resistance; polyester plasticizer can be added in an amount of 20% to 40% in soft PVC products.
2. LNBR plasticizer
Liquid nitrile series ( LNBR ) is a rubber with a main chain structure of butadiene and acrylonitrile, with or without other functional groups , and is in a viscous liquid state at room temperature. Its number average molecular weight is usually below 10,000 . LNBR is a new type of low molecular liquid toughening, plasticizer and rubber softener. Liquid nitrile is a viscous liquid rubber developed on the basis of nitrile rubber. It is slightly yellow, transparent and odorless. Liquid nitrile function: reactive plasticizer and softener.
Liquid nitrile ( LNBR ) can not only replace DOP , DBP , DOA , DOS and solid plasticizer powder nitrile rubber, but also improve the cold resistance, heat / light / aging performance, oil resistance of PVC , and improve the quality of the product. Resilience, impact resistance and surface molding effect of products, and can improve the migration of plasticizers in products. Can produce: wire / cable materials, automobile dashboards, automobile bumpers, plastic films, irrigation water hoses, mining conveyor belt cores, shoemaking industry, brake pad industry, etc.
In terms of “plasticizer”, liquid nitrile is a high molecular weight rubber with plasticizer function. Liquid nitrile is “vulcanizable” (can be co-vulcanized with sulfur or peroxide) during rubber vulcanization . In terms of “operating aids”, liquid nitrile is a physical and chemical modifier with softener function, which can improve processing operability (fluidity of rubber, stiffness of low-hardness rubber, flexibility of high-hardness rubber, Self-adhesiveness during rubber processing, etc.), as well as improving the physical properties and processing performance of low-hardness rubber products.
Liquid nitrile rubber is synthesized through free radical emulsion polymerization. It has a small relative molecular weight and is fluid at room temperature. The earliest varieties were without functional groups and random functional groups. Later, they were mainly end-functional groups, such as hydroxyl-terminated liquid nitrile rubber (HTBN) , carboxyl-terminated liquid nitrile rubber (CTBN) , thiol-terminated liquid nitrile rubber (MTBN) and Amino-terminated liquid nitrile rubber (ATBN) , etc. When this kind of rubber containing end-functional groups is cured, the functional groups at the end of the molecules participate in cross-linking, so that the relative molecular mass between the cross-linking points without free chain ends in the cross-linked network of the vulcanized rubber is larger than that of ordinary rubber, and the structure is regular and No short chains, so softness is great.
3. PNBR plasticizer
Powdered nitrile rubber ( PNBR ) is a polar copolymer of acrylonitrile and butadiene, which can be used to modify thermoplastic materials such as PVC , epoxy and phenolic resins. Due to its polarity, it shows very good compatibility with PVC and is widely used in the shoemaking industry, hoses, wires and cables, conveyor belts, profiles, friction materials and other resin modified materials to increase the elasticity of the product. , impact resistance, aging resistance, weather resistance, oil resistance, low temperature brittleness resistance, etc.
The American Goodyear Company uses polyester plasticizer to produce special nitrile rubber powder P8300 ( relative molecular weight is about 200,000 ) , which can be used as a modifier for PVC , ABS resin, phenolic resin , etc., and can increase material toughness and improve cold impact sex. Adding 20 parts of special nitrile rubber powder to PVC , the weight loss of the sample after soaking in isooctane for 22 hours can be reduced from the original 8% to 0.6% , which shows that the nitrile powder produced with polyester plasticizer It is an ideal raw material for manufacturing oil-resistant products.
As an elastomer , PNBR forms an “island” structure when blended with PVC , significantly improving the flexibility of PVC . PNBR contains a large amount of -CN groups, which can significantly improve the oil resistance and solvent resistance of PVC . There is no flexible and elastic chain structure in PVC molecules, so its performance at low temperatures is poor. After adding PNBR elastomer, its low temperature resistance is improved. When PVC is used alone, its insulation is not very ideal. Adding PNBR can improve the resistance performance of the product. PNBR can significantly improve the wear resistance of PVC and extend the service life of the product.PNBR can significantly improve the anti-skid performance of PVC . The anti-skid performance of PNBR/PVC is comparable to that of thermoplastic rubber ( TPR ).
After adding PNBR as a macromolecular plasticizer to plasticized PVC, the aging resistance of the mixture is improved. During the photoaging process of plasticized PVC , the small molecule plasticizer DOP degrades and migrates under light, which reduces the mechanical properties and elasticity of plasticized PVC . As a macromolecular plasticizer, PNBR not only improves the plasticization PVC has improved oil resistance and extraction resistance, and its toughness has also been improved. At the same time, during the aging process, the mechanical properties of the PVC/PNBR blend remain better. However, because the PNBR structure contains a large amount of 1,4- trans-butadiene, it is easy to cause the blend to produce conjugated double bonds during aging, causing the product to turn yellow.
4. Ethylene terpolymer
According to the different comonomers, ethylene terpolymers can be divided into ethylene – vinyl acetate – carbon monoxide ( EVA-CO ) ethylene – n- butyl acrylate – carbon monoxide ( EnBA-CO ) and ethylene – n-butyl acrylate glycidyl ester ( EnBA-GMA ) three categories.
Among them , EVA-CO is mainly used as a plasticizer for PVC . The relative molecular mass of EVA-CO terpolymer is about 250,000 , and it has good compatibility with PVC . At the same time, with the addition of EVA-CO in the blend As the mass fraction increases, the glass transition temperature of the blend system also decreases . When the mass ratio of PVC/EVA-CO is 70:30 , the Tg of the blend is -6 °C. When the ratio of the two is 50:50 , the Tg of the blend drops to -29 °C. In terms of mechanical properties, the addition of EVA-CO reduces the hardness, tensile strength, tear strength and modulus stress of the PVC/DOP system, but increases the elongation.Each component of EVA-CO resin for soft PVC modification is VA (20 ± 2)% and CO (10 ± 2)% .
EVA-CO terpolymer, DuPont’s brands are EIvaloy®741 and Elvalo®742 , etc., known as PVC polymer cold-resistant environmentally friendly plasticizer. In the 1990s , China also developed domestically produced EVACO , which is divided into two types: plasticized type and toughened type.
EIvaloy® is a non-phthalate solid polymer modifier. It can be used as a permanent plasticizer to provide durable and superior properties for soft PVC . It can also be used as an impact modifier and processing aid to improve rigid PVC products. performance and productivity.
The molecular weight of PVC is between 50,000 -150,000 , and that of Elvaloy® is between 250,000-400,000 . This is a far cry from low molecular weight or polyester plasticizers. The high molecular weight brings stable molecular structure and non-migration, and also greatly enhances the chemical resistance of the product.
EIvaloy® does not contain phthalates, and there is no worry of harmful VOC substances being released during long-term use. Elvaloy® has obtained FDA certification, helping PVC to create an environmentally friendly and healthy product image.
EIvaloy® is widely used in PVC single-layer roofs, geomembranes, cable sheaths, hoses, automotive interiors, children’s toys, footwear and other application fields.
DuPont Elvaloy® ethylene terpolymer in the United States now belongs to DOW Chemicals and has many brands. The main brands are HP441 , HP661 , HP4051 , 741 , 742 , 4924 , AM , etc.Mainly used for plasticizing and toughening PVC , PET , ABS , SAN , PVC/ABS alloys and polyolefin blend modification systems. It can significantly improve the polarity and processing width of the blend system; improve the cold resistance and wear resistance of the product. , oil resistance, UV resistance, chemical and microbial corrosion resistance; improve the fluidity, thermal stability and impact resistance of the blend system; the molecular weight is equivalent to PVC , plasticizing, anti-migration, giving the product a rubber-like feel and extending the use of the product life.
5. Write at the end
Although the plasticizing effect of polymer plasticizers is not as good as that of small molecule plasticizers, it is better than small molecule plasticizers in improving the strength, oil resistance, solvent resistance and heat resistance of soft PVC . Therefore, with the improvement of environmental awareness in various countries and the promulgation and implementation of a series of regulations, restrictions on toxic and harmful plasticizers in PVC products have made the development and growth of polymer plasticizers imperative.