Polymer Additives Isosorbide: a sustainable, safe, high-performance coatings and plastics additive

The use of isosorbide as an additive for coatings gives products better resistance to UV, to abrasion, to scratching and to impact, as well as better adhesion and improved properties for water-based formulations, while in plastic packaging it can be used to modify the properties of PET to produce a material with enhanced thermal properties


he demands on today’s coatings, adhesives, sealants and elastomers (CASE) create a long list of desirable properties for a ‘would be’ feedstock, which is where isosorbide comes in. Perfectly safe and produced from an annually renewable feedstock, isosorbide has a unique combination of properties that offers excellent potential for a range of CASE applications. Isosorbide also has a number of potential uses in plastic packaging applications.

What is isosorbide and how is it made?

Isosorbide is a plant starch-derived bicyclic diol (Figure 1) with rich functionality for a range of applications in the CASE, packaging and automotive sectors.

life cycle analysis methodology, peer-reviewed by an external auditor). However, isosorbide shows other significant benefits in addition to these environmental credentials: Isosorbide is:

• Non-toxic • Non-carginogenic • Non-endocrine disruptor • REACH compliant • Suitable for food contact and for the manufacture of cosmetics and pharmaceuticals.

These attributes make the performance benefits of isosorbide of interest and value in a diverse range of applications.

What are the properties of isosorbide and how can it be used?

Isosorbide can be incorporated alongside other monomers to modify the properties of, for example, polyethylene terephthalate (PET), polycarbonates (PC), polyurethanes (PU) and epoxy resins. When used in this way it can enhance:

• Thermal properties, for example, increasing Tg, the glass transition temperature

Isosorbide C6 H10

146.14g/mol CAS 652.67-5

Figure 1. Isosorbide is a bicyclic diol derived from plant starch.

To synthesize isosorbide, starch from annually renewable feedstocks is hydrolyzed to produce glucose which is then converted to sorbitol and on to isosorbide by hydrogenation (Figure 2). Over the past two decades, isosorbide manufacturer Roquette has refined and optimized this manufacturing route to produce stable, high-purity isosorbide in industrial quantities. The company’s flagship plant produces isosorbide of three different grades, each tailored to specific industrial applications. As a plant-based, sustainable feedstock with a carbon footprint of only 0.09 kg CO2

/kg of product, isosorbide is an attractive substitute for

monomers such as bisphenol A, which has a carbon footprint about 60 times higher (as determined in an internal comparative study based on



O OH O O OH O HO Figure 2. Synthesis of POLYSORB isosorbide. 36 March/April 2021 • Issue 2 OH O OH GLUCOSE SORBITOL HO HO OH O HO OH OH OH OH OH OH O HO O OH 04

• Chemical resistance to both water and organic solvents (such as acetones and esters)

• Optical performance, including characteristics such as transparency and birefringence • UV resistance, with reduced yellowing upon exposure to the sun • Mechanical properties, such as scratch, impact and bending resistance • Adhesion, a crucial property for the CASE sector. • Appearance, for instance imparting high gloss

Isosorbide can reduce the environmental burden associated with the use of existing materials, while maintaining performance, or enable the realization of new performance profiles, to meet the exacting requirements of different markets.

Industrial applications for isosorbide

The CASE market is characterized by diversity with products formulated specifically to meet precisely defined, sometimes unique applications.

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