Improve Your UV Curables with Cellulose Acetate Butyrate
The Market for UV Curables is Expanding
UV-curable inks and coatings are experiencing rapid growth and adoption due to their many advantages. For example, higher productivity due to near-instantaneous UV curing makes coating and printing processes more economical. Also, the lack of heat in curing is ideal for heat-sensitive materials, such as plastics. In addition, UV-cured coating and ink systems can form very tough surfaces on substrates. For these reasons and more, UV-cured coatings and inks are a great option in a variety of applications and industries.
However, there are some drawbacks that one should consider when formulating a UV curable coating or ink. The absence of solvent and speed of cure can lead to poor wetting, leveling, flow, and pigment dispersion. Due to the high cross link density UV coatings and inks can also shrink upon cure causing adhesion issues. Ultimately these issues can lead to a coating or ink with sub optimal appearance and performance.
Why Use Cellulose Esters? The Benefits are Twofold
Improved Appearance
Increased flow and leveling for fewer surface defects
Better gloss and reflection
Optimal metallic and pearlescent flake alignment
Improved pigment dispersion
Better Performance
Reduced shrinkage, fewer adhesion failures
Increased hardness and abrasion resistance
Improved weathering and chemical resistance
FDA approved for direct and indirect food contact
Eastman™ Cellulose esters (CE’s) with high butyryl content will dissolve in and tolerate common UV curable monomers such as styrene and acrylates. When formulated into UV curable applications such as inks and OPVs, CE's help improve the flow and leveling leading to surfaces with fewer defects and higher gloss. CEs will improve pigment orientation and flop allowing for brightly colored metallic and pearlescent finishes. CE's also act as fillers to help reduce the shrinkage of coatings and inks upon cross link and cure. In addition, Eastman’s cGMP compliance allow ink and coating formulations for direct and indirect food contact.
Cellulose acetate butyrates are typically dissolved in monomer as a masterbatch. This masterbatch is then used as an additive for the UV-curable system. Typical additive use levels are 0.1–2.0 wt% of the final formulation. In some instances, additive levels as low as 0.1–0.5 wt% have improved formulation properties. The table below lists Brookfield viscosities of the recommended grades used at 5% concentration in common monomers. Cellulose esters with lower molecular weights can be used in applications where viscosity is a limitation.
Monomer
CAB 381-0.1
CAB 551-0.01
CAB 551-0.2
HDDA
60
30
90
TMPTA
1670
660
2,080
DPGDA
110
40
140
TPGDA
180
60
200
IBOA
I
40
350
Styrene
I
7
30
Legend
Value = Brookfield Viscosity at 24° C
I = Insoluble
Summary
UV-curable inks and coatings provide many benefits over solvent- and water-based inks in terms of efficiency with faster cure times, better abrasion resistance, and higher versatility when applied on heat-sensitive substrates. Eastman's cellulose acetate butyrate (CAB) can minimize issues of shrinkage that occur with UV-curable inks and coatings while helping to improve flow, leveling, wetting, and pigment dispersion properties. Click below to request more information and start working with a sample for your formulation.
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