The Essential Guide to Oligomers for UV/EB Systems

October 23, 2025

Author: Felix Adam

Oligomers—often called UV-curable oligomers or reactive diluents—are short, multifunctional chains that convert rapidly into hard, durable networks under ultraviolet (UV) light or electron beam (EB). Because they’re liquids with controlled viscosity and multiple reactive sites, they let you fine-tune cure speed, hardness, flexibility, adhesion, and chemical resistance while keeping VOC low.


What are oligomers?


Oligomers sit between small monomers and long polymers. In UV/EB systems they act as reactive diluents (lowering viscosity while still reacting into the film) and crosslinkers (raising network density for performance). Typical families include di- and tri-(meth)acrylates such as TEGDMA, BDDMA, TMPTMA, and HDDA.



How UV/EB curing works


Photoinitiators (UV) or direct EB energy generate radicals that open the (meth)acrylate double bonds on your oligomers and comonomers. Chains grow and crosslink within milliseconds to seconds, yielding a solid film with targeted properties. No bake necessary, low energy input, high throughput.



The big property trade-offs


  • Viscosity vs. solids: Low-viscosity oligomers (e.g., TEGDMA, HDDA) increase solids and flow without adding solvent.
  • Cure speed vs. control: Acrylates (e.g., HDDA) generally cure faster than methacrylates (TEGDMA/BDDMA/TMPTMA).
  • Crosslink density vs. toughness: Tri-functional TMPTMA drives hardness/chemical resistance but can raise brittleness and shrinkage; di-functionals (TEGDMA/BDDMA/HDDA) help balance.
  • Tg/heat resistance vs. flexibility: Short/rigid spacers (BDDMA, TMPTMA) raise Tg; longer/aliphatic spacers (TEGDMA, HDDA) add flexibility.
  • Adhesion & yellowing: HDDA is a go-to for adhesion to metals/plastics and low yellowing; blends help tailor results.



Choosing the right oligomer


  • TEGDMA (triethylene glycol dimethacrylate): low viscosity, good flow/leveling, fast through-cure; great as a reactive diluent to lift conversion and hardness.
  • BDDMA (1,4-butanediol dimethacrylate): more rigid spacer → higher Tg, gloss retention, and chemical resistance; ideal where film strength and heat resistance matter.
  • TMPTMA (trimethylolpropane trimethacrylate): tri-functional crosslinker for maximum hardness, solvent resistance, and line speed—use judiciously to manage brittleness.
  • HDDA (hexanediol diacrylate): very fast cure, low viscosity, strong adhesion to plastics/metals, low yellowing; balances speed and processability.



Core applications (and how to deploy oligomers)



Coatings & printing inks


Use oligomer blends to hit viscosity targets, throughput, and end-use durability.


  • Target outcome: fast cure, smooth laydown, high hardness/chemical resistance, low VOC.
  • Typical picks: HDDA for speed/adhesion and low yellowing; TMPTMA to push hardness/solvent resistance; TEGDMA to improve flow and through-cure; BDDMA to raise Tg and mar resistance.
  • Deep dive: Coatings & Printing Inks hub



Adhesives & sealants


Dial in fixture time, strength, and temperature/chemical performance.


  • Target outcome: rapid set, strong bonds on metals/PC/ABS, durable service.
  • Typical picks: HDDA for wicking and fast fixture with strong substrate adhesion; BDDMA for higher Tg and long-term strength; TEGDMA for wet-out and gap fill; TMPTMA when you need instant green strength and high final hardness.
  • Deep dive: Adhesives & Sealants hub



3D-printing & photolithography resins (SLA/DLP)


Balance resolution, green strength, and final mechanics.


  • Target outcome: fine features, predictable shrinkage, tuned stiffness/HDT.
  • Typical picks: TEGDMA or HDDA to reduce viscosity and improve print fidelity; BDDMA to boost stiffness/HDT; TMPTMA to maximize dimensional stability (blend to control brittleness).
  • Deep dive: 3D Printing & Photolithography hub



Formulation starting points


  • Reactive diluent role: TEGDMA or HDDA at ~5–30% to hit application viscosity and cure speed.
  • Raise hardness/Tg: Add BDDMA (rigidity/chemical resistance) and a small fraction of TMPTMA (high crosslink).
  • Balance brittleness: Offset TMPTMA with TEGDMA/HDDA; consider flexibilizers if impact resistance is critical.
  • Adhesion tuning: Start with HDDA for plastics/metals; adjust surface prep/photoinitiator package as needed.



Safety & compliance


All four are skin/respiratory sensitizers; use gloves, goggles, and ventilation. Ensure labeling and registration alignment for your market (e.g., REACH) and maintain robust QC (viscosity, acid value, residual monomer, color, gel fraction).