A 2026 ACS Omega study shows why a bio-based plasticizer should be approved by epoxidation degree and end-use evidence, not by renewable content alone. Buyers comparing hot-melt PSA systems should review flow, softening point, tack, peel and shear together, then confirm the result in the intended SIS or SBS formulation.
Direct answer for bio-based hot-melt PSA buyers
Compare the oil’s epoxidation degree, the formulation’s viscosity and softening point, and the resulting tack, peel and shear under the same test conditions. The 2026 ACS Omega study found that refined soybean oil and partially epoxidized soybean oil changed these properties in different directions. A renewable feedstock label does not predict whether a formulation will run, bond or release as required.
What the 2026 soybean oil study measured
The study compared mineral oil with refined soybean oil and soybean oil at epoxidation degrees from 0 to 6.7% in a fixed hot-melt pressure-sensitive adhesive formulation. It measured viscosity, softening point, tack, 180-degree peel, shear, glass-transition temperature and rheological behavior. The formulation basis was held constant so the plasticizer effect could be examined.
Relative to mineral oil, refined soybean oil reduced viscosity from 3998 ± 302 to 2580 ± 143 mPa.s and reduced softening point from 63.7 ± 0.8 to 45.6 ± 0.3 °C. Those changes may support lower application temperatures in the tested system, but the paper does not establish a universal processing temperature for every SIS or SBS grade.
For freezer-tape and label comparisons, the paper reported higher tack and lower glass-transition temperature for refined soybean oil and soybean oils with 0, 2.0 and 3.7% epoxidation than for the mineral-oil control. It also reported lower shear for those formulations. Fully epoxidized soybean oil showed lower tack and lower peel strength in the reported formulation, a direction the authors associated with removable tape potential. These are study results under the stated formulation and test conditions, not a grade approval.
Why epoxidation degree changes the buyer question
Epoxidation changes the soybean oil chemistry and therefore its interaction with the polymer and tackifier package. In a hot-melt PSA, a plasticizer can affect melt flow, wet-out, glass transition, cohesive strength and failure mode at the same time. The useful question is not whether the oil is bio-based. It is where the chosen oil sits in the balance between processability and bond performance.
| Evidence field | What it tells the buyer | Question to record |
|---|---|---|
| Epoxidation degree | Defines the plasticizer variant being compared and helps explain differences between batches or suppliers. | What method and reporting basis define the percentage? |
| Viscosity and softening point | Shows whether the compound can be mixed, pumped and coated within the line’s thermal window. | At what temperature, shear rate and test method were they measured? |
| Tack and peel | Describes rapid contact and separation on a defined substrate. | What substrate, dwell time, coat weight and peel speed were used? |
| Shear and glass transition | Helps assess load holding, low-temperature behavior and the risk of trading cohesion for wet-out. | What load, area, temperature and failure definition apply? |
Connect rheology to the application test
The open-access study in PMC explains why PSA buyers should request more than one rheology number. Storage modulus, G’, describes the elastic response. Loss modulus, G”, describes the viscous response. Their ratio, tan delta, helps show how the material dissipates energy at a chosen temperature and time scale.
That 2024 study used dynamic mechanical analysis and time-temperature superposition to relate viscoelastic behavior to shear, peel and tack in an SBS model adhesive and commercial systems. The authors reported that the correlations depend on the test frequency and application property being considered. Use that approach as a test-plan guide, then confirm the result with the actual plasticizer, tackifier, substrate and coating process.
For procurement, a supplier report should make the test conditions visible. A viscosity measured at one temperature cannot replace a coating-window study. A tack result without dwell time or substrate information cannot predict a label or tape line. The data file should also identify the formulation revision and sample date.
Where SIS and SBS fit
The Kraton polymer adhesives brochure gives a supplier-specific starting point: it presents SIS polymers for PSA properties and high-speed extrusion suitability, and SBS polymers for high cohesive strength and solvent coating. The brochure also lists compatibility, melt viscosity and the balance of tack, peel and shear as formulation considerations.
That positioning does not decide the grade for a customer. Jusage SIS grades and SBS grades should be reviewed against the coating route, substrate, service temperature and required failure mode. A bio-based plasticizer can change the balance in either family, so the supplier sample must be tested in the intended polymer and tackifier package.
Bio-based hot-melt PSA buyer checklist
Application context and next step
For labels and tapes, review the Labels and Tapes application page with the intended liner, facestock and service temperature. For packaging, the Packaging application page provides the process context. Jusage’s Download Center and Customized Service page provide routes for technical files and application discussion.
Send the polymer family, plasticizer type, epoxidation basis, substrate, process temperature, coat weight and test plan through the contact page. Jusage can discuss whether an SIS or SBS direction fits the trial and which sample or technical file to review first. The final approval remains dependent on the customer’s formulation and validation work.
Frequently asked questions
Does a higher epoxidation degree always improve a hot-melt PSA?
No. The 2026 study found different trade-offs across the tested epoxidation degrees. Fully epoxidized soybean oil showed lower tack and peel in the reported formulation, while some lower-degree variants showed higher tack and lower glass-transition temperature than the mineral-oil control.
Can the study’s viscosity and tack numbers be used as a grade specification?
No. They describe one fixed formulation and its test conditions. Use the values to define a comparison plan, then request supplier data and run the intended substrate and process.
Should a bio-based plasticizer be tested differently in SIS and SBS?
Yes. Polymer family, tackifier compatibility, coating route and failure mode can change the result. Treat SIS and SBS as separate formulation discussions and keep the process and end-use tests comparable.
Approve the evidence, not the label
The 2026 research gives buyers a practical starting point: a bio-based plasticizer is a formulation variable with measurable effects on flow and adhesion. Approve the epoxidation basis, rheology window and application tests together. When the supplier can show those links, the SIS or SBS grade discussion becomes specific enough for a controlled trial.