Improve your performance with Stahl Carbodiimide Crosslinkers (CDI)

Improved performance with Carbodiimide Crosslinkers (CDI)
Crosslinkers help to improve performances like adhesion, toughness, abrasion and chemical resistance. Reactive groups of traditional crosslinkers make them harmful, irritant, sensitizing or even toxic to humans or to the environment. Compared to traditional crosslinkers, such as aziridine, isocyanates, and melamines, polycarbodiimide crosslinkers have a number of advantages.

Stahl Polymers new carbodiimide crosslinkers set a new standard, being the most sustainable, safe and easy-to-use option for high-performance crosslinking. Stahl Polymers recently had the privilege to support some leading global coating producers to make a successful transition from traditional isocyanates and aziridines towards the carbodiimide technology. 

Carbodiimides are defined as non-hazardous under GHS (Global Harmonized System), and most of Stahl Polymers portfolio is Swiss Ordinance compliant for indirect food contact applications. Carbodiimides react at low temperature and offer extended pot life, which make them easy-to-use to formulate high-performance inks, paints and coatings, from do-it-yourself to high-end industrial applications.

Traditional crosslinkers

Often used isocyanate crosslinkers have the disadvantages of having a limited pot life and high-sensibility to moisture. Aziridines have also been the standard for performant crosslinking for a long time. However, their use is decreasing enormously in specific applications due to their toxicity, handling limitations and serious health risks for employees and customers. Even the latest aziridine market developments are still classified.

How does Crosslinking work?

Crosslinking is in fact connecting the polymers through reactive chemistry, this makes sure it strengthens the network of a specific coating. In the case of polycarbodiimides, each molecule contains many reactive groups (-N=C=N-) and reacts with multiple polymer chains, that results in a 3D polymer-crosslinker network via covalent chemical bonds.

Polycarbodiimides (CDI) selectively react with carboxylic acid (-COOH) groups in polymer chains. Due to the high reactivity, crosslinking reaction can take place at room temperature.

Key Benefits of Carbodiimide Crosslinkers

• Low toxicity reduces labeling requirements
• Improve chemical and scratch resistance
• Quick and efficient processing: crosslinks at room temperature don’t need stoving
• Outstanding adhesion to wide range of substrates
• Excellent pot life: up to several weeks depending on the pH
• Swiss ordinance compliant for indirect food contact

Crosslinkers chemistries overview

Carbodiimide crosslinkers are an excellent alternative to more hazardous crosslinkers. In addition, standard carbodiimides are not sensitive to the presence of water and are able to achieve long pot life. In adapted pH conditions, carbodiimides can be stable in formulation for several weeks.

	Aziridine	Melamine	Isocyanate	Carbodiimide*
Reacts with	-COOH	-OH	-OH, -NH, Water	-COOH
Pot life	Up to 12 hours	Very long	1 to 6 hours	Up to several weeks
GHS Symbols				None
R-phrases	Muta Cat. 3, R68, R43, R41, R38	Carc. Cat 2, R43/45/52/53	R43, R52/53	None
Moisture sensitivity	High	Low	Very high	Low
Yellowing	High	Low	Low	Low
Gas release	None	None	CO2	None
Compatibility glossy resin	Good	Good	Medium	Good

* Not all products have all properties

Carbodiimide crosslinkers potfolio overview

Product name	Type	Solids (%)	Viscosity (cP)	Solvent system	VOC (%)	Swiss Ordinance comptiant*	Label on product**
Picassian® XL-701	Multifunctional	50	25 - 300	MPA	49.9	Yes
Picassian® XL-702	Standard	40	25 - 300	H2O	0	Yes	-
Picassian® XL-721	Standard	40	0 - 500	H2O	0	Yes	-
Picassian® XL-725	Multifunctional	50	50 - 400	PGDA	48.1	Yes	-
Picassian® XL-732	Multifunctional	100	500 - 2,000	-	0.5	No
Picassian® XL-752	Standard	30	0 - 150	H2O	0	Yes	-
Picassian® XL-755	Multifunctional	100	6,000 - 12,000	-	0	Yes	-
Picassian® XL-762	Standard	100	15,000 - 20,000	-	0	No	-

* For indirect food contact
** Labeling due to solvent or additive, not because of CDI polymer