Hydrogenated and non-hydrogenated hydrocarbon resins differ fundamentally in molecular saturation, and that difference drives nearly all downstream performance. Non-hydrogenated resins retain unsaturated double bonds and aromatic rings from the cracked feedstock, giving them high tack, strong compatibility with aromatic polymers (SBS, EVA), and low cost - but also making them prone to UV-induced yellowing, oxidation, and heat discoloration [1][2]. Hydrogenated resins saturate those double bonds through catalytic hydrogenation, delivering water-white color (Gardner ≤1), UV resistance, and thermal stability, but at a higher cost and typically with reduced compatibility for high-aromatic polymers [1][3][4]. Selection is driven by three factors: color stability requirement, UV/heat exposure, and compatibility with the base polymer in your formulation [5].
1. What Is Hydrocarbon Resin?
Hydrocarbon resins are low molecular weight thermoplastic tackifiers derived from cracked refinery streams, most commonly C5 aliphatic, C9 aromatic, and DCPD (dicyclopentadiene) feedstocks [1][5]. They are produced by cationic polymerization of the cracked stream, leaving behind unsaturated double bonds and aromatic rings in the polymer backbone [1][6].
Two widely used base products are C9 Petroleum Resin and C5 Hydrocarbon Resin, and their molecular structure is where the hydrogenated vs. non-hydrogenated distinction begins.
2. Non-Hydrogenated Hydrocarbon Resins: Structure and Properties
Non-hydrogenated hydrocarbon resins retain the unsaturated double bonds and aromatic rings left over from cationic polymerization [1][6]. These structural features drive both their advantages and their limitations.
- Advantages: high tack for pressure-sensitive adhesives; strong compatibility with aromatic polymers such as SBS (styrene-butadiene-styrene) and EVA; excellent adhesion to low-energy surfaces like polyethylene and polypropylene; and low cost, since they skip the hydrogenation step [2][5][7].
- Limitations: residual unsaturation makes the resin prone to oxidation, UV-induced yellowing, and thermal discoloration. A non-hydrogenated C9 resin typically starts as a pale yellow or amber color (Gardner 8–12, 50% in toluene per ASTM D6166 [8]) and darkens over time under UV or heat exposure, making it unsuitable for clear coatings, white adhesives, or products where color consistency is non-negotiable [2][6][9].
3. Hydrogenated Hydrocarbon Resins: Structure and Properties
Hydrogenated hydrocarbon resins go through a post-polymerization hydrogenation step in which hydrogen gas is added to the unsaturated bonds in the presence of a catalyst (typically palladium or nickel on a support) [1][4]. The aromatic ring is converted to a cycloalkane structure, and olefinic double bonds are saturated. The result is a resin with dramatically improved color (Gardner ≤1, water-white) and light stability [3][4][10].
- Advantages: excellent UV resistance; excellent thermal stability for high-temperature processing (e.g., hot-melt adhesives processed at 150–200 °C); water-white color; and low odor [3][4][10][11].
- Limitations: higher cost (typically commanding a premium over non-hydrogenated variants, with the premium varying by grade, hydrogenation level, and supplier); potential for brittleness at very high hydrogenation levels; and reduced compatibility with high-aromatic polymers like SBS compared with non-hydrogenated C9 [4][5].
Dedicated C9 Hydrogenated Petroleum Resin and Hydrogenated DCPD Resin grades are specified for Gardner color, softening point (Ring and Ball), iodine value, and residual monomer limits suited to PSA, hot-melt adhesive, and coating applications [4][10][11].
4. Comparison Table: Hydrogenated vs. Non-Hydrogenated
| Property | Non-Hydrogenated C9 | Hydrogenated C9 | Hydrogenated DCPD | Reference |
|---|---|---|---|---|
| Gardner color (50% in toluene) | 8–12 (pale yellow to amber) | 0–1 (water-white) | 0–1 (water-white) | [8][10][11] |
| UV / color stability | Poor (yellows over time) | Excellent | Excellent | [3][4] |
| Thermal stability | Moderate (discolors at high processing temps) | Excellent | Excellent | [3][4][9] |
| Solubility parameter (typical) | High (aromatic-rich) | Lower (cycloalkane-rich) | Mixed aliphatic-cyclic | [5][12] |
| Best compatible polymers | SBS, EVA, aromatic-rich systems | SIS, SEBS, EVA, APAO | SIS, SEBS, EVA, APAO | [5][12][13] |
| Cost | Baseline | Premium (varies by grade and supplier) | Premium | [5] |
| Typical applications | Packaging tape, rubber compounding, industrial primers, road marking | Food packaging PSA, medical coatings, clear/white hot-melt adhesives | High-end PSA, cosmetics, premium clear coatings | [5][10][11] |
5. Compatibility: Solubility Parameter Is the Key
The compatibility difference between hydrogenated and non-hydrogenated resins is driven by solubility parameter (Hildebrand δ) [5][12]. Non-hydrogenated aromatic C9 resins have a high solubility parameter and pair well with SBS, EVA, and other aromatic-rich or medium-polarity polymers [2][5]. Hydrogenated C9 and aliphatic C5 resins have lower solubility parameters and pair better with SIS, SEBS, and EVA [12][13].
The Kraton G (SEBS) family illustrates this principle: as the hydrogenated form of SBS, Kraton G grades are documented as offering "better compatibility with more polar chemistries" compared with unhydrogenated SBS, which is consistent with the solubility-parameter shift caused by hydrogenation [13]. Suppliers such as Eastman document equivalent behavior in their Regalite (hydrogenated C9) and Plastolyn (aromatic C9) tackifier lines [4][5].
Practical rule of thumb: SBS/EVA-based formulations → non-hydrogenated aromatic C9 or hydrogenated DCPD; SIS/SEBS/EVA-based formulations → hydrogenated C9 or hydrogenated aliphatic C5 [5][12]. Trial formulation remains essential, since solubility parameter is only one component of compatibility.
6. Selection Criteria: When to Choose Which
| Application | Recommended resin type | Key rationale |
|---|---|---|
| Cardboard packaging hot-melt adhesive | Non-hydrogenated C9 or C5 | Cost-driven; color stability not required [2][5] |
| Hidden-view packaging tape | Non-hydrogenated C9 or C5 | Cost-driven; UV exposure minimal [2][5] |
| Tire inner liner / industrial hose rubber compound | Non-hydrogenated C9 | Tack and compatibility priority [2] |
| Road marking paint | Non-hydrogenated C9 | Aromatic content supports substrate adhesion [2][6] |
| White or clear hot-melt adhesive (indoor) | Hydrogenated C9 | Water-white color required [10][11] |
| Food packaging pressure-sensitive label | Hydrogenated C9 or hydrogenated DCPD | Water-white color; FDA compliance; low migration [10][14] |
| Medical device coating | Hydrogenated C9 or hydrogenated DCPD | Purity and low extractables [10][11] |
| Outdoor construction sealant | Hydrogenated C9 or hydrogenated DCPD | UV and thermal stability required [3][4] |
| High-temperature processing adhesive (150–200 °C) | Hydrogenated C9 | Thermal discoloration resistance [3][4] |
7. FDA Food-Contact Compliance
Hydrogenated hydrocarbon resins are used in food-contact adhesive and coating applications under specific FDA provisions. The relevant U.S. regulations are:
- 21 CFR 175.105 (Adhesives): covers adhesives used in food packaging applications, including indirect food contact scenarios [14].
- 21 CFR 175.320 (Resinous and Polymeric Coatings): covers resinous and polymeric coatings for food-contact surfaces, including coatings for polyolefin films [14].
- 21 CFR 176.170 (Components of Paper and Paperboard in Contact with Aqueous and Fatty Foods): relevant for paper and paperboard food packaging [14].
- 21 CFR 176.180 (Components of Paper and Paperboard in Contact with Dry Food): relevant for dry-food paper packaging [14].
- 21 CFR 177.1520 (Olefin Polymers): relevant for polyolefin-based food packaging systems [14].
Compliance is grade-specific and application-specific. Request supplier FDA compliance statements for the specific grade and use case [14]. Non-hydrogenated C9 resins are also covered under these regulations, but their yellowing behavior and higher residual unsaturation make them less commonly selected for visible food-packaging applications.
8. Quality Parameters to Request Before Evaluation
| Parameter | Typical method | What it tells you |
|---|---|---|
| Gardner color | ASTM D1544-04(2018); alternatively ASTM D6166 (50% in toluene) | Color quality; direct indicator of hydrogenation completeness [7][8][15] |
| Softening point | ASTM E28 (Ring and Ball) | Thermal performance and processing window [10] |
| Iodine value / bromine number | Titration | Residual unsaturation; direct indicator of hydrogenation degree [1][3] |
| Acid value | Titration (mg KOH/g) | Residual acidity; adhesion and stability indicator [10] |
| Molecular weight distribution | GPC | Tack, viscosity, and compatibility behavior [1] |
| Solubility parameter (δ) | Calculated or supplier-specified | Compatibility prediction with base polymer [5][12] |
| FDA compliance statement | Supplier regulatory letter | Confirms applicability under specific CFR sections [14] |
| Batch-specific COA | Supplier COA | Confirms actual values for delivered batch |
9. What This Article Does NOT Claim
- No universal "best" resin claim. Hydrogenated is not always better; non-hydrogenated is the correct choice for cost-driven, color-insensitive applications [2][5].
- No specific percentage cost or performance improvement is claimed for any customer case. Actual cost premium and performance gain vary by grade, supplier, and application.
- No claim that hydrogenation guarantees FDA compliance. Compliance is grade-specific and requires supplier documentation [14].
- No claim that solubility parameter alone predicts compatibility. Trial formulation is always required [5][12].
- No claim that all hydrogenated grades are equivalent. Full vs. partial hydrogenation, feedstock purity, and molecular weight distribution all affect performance [1][4].
10. Conclusion
As the preceding sections show, the difference between hydrogenated and non-hydrogenated hydrocarbon resin is fundamentally a question of molecular saturation. Non-hydrogenated resins retain unsaturated double bonds and aromatic rings, giving them high tack, low cost, and strong compatibility with aromatic polymers like SBS - but also making them prone to UV yellowing, oxidation, and thermal discoloration. Hydrogenated resins saturate those bonds, delivering water-white color (Gardner ≤1), UV and thermal stability, and better suitability for clear or food-contact applications - but at a higher cost and with a solubility-parameter shift that favors SIS/SEBS/EVA over SBS-rich systems. Selection should be driven by three questions: does the application need color stability? what is the UV/heat exposure profile? which base polymer is being used? The solubility-parameter rule (aromatic C9 with SBS/EVA; hydrogenated C9 or aliphatic C5 with SIS/SEBS/EVA) is a useful first screen, but trial formulation on the actual system remains the deciding step. For food-contact applications, FDA compliance under 21 CFR 175.105, 175.320, 176.170, 176.180, and 177.1520 must be confirmed with the supplier. Every value in this article is a typical published range or standard requirement; selection must be validated against the supplier TDS, batch COA, and a structured trial on the actual formulation.
11. Next Step
If you are evaluating C9 Petroleum Resin, C9 Hydrogenated Petroleum Resin, for your application, send us:
- Application type (PSA, hot-melt adhesive, coating, rubber compound, ink)
- Base polymer system (SBS, SIS, SEBS, EVA, APAO, NR, other)
- Color stability requirement (water-white, clear, non-yellowing, or color-agnostic)
- UV / heat exposure conditions
- Food-contact or regulatory requirement (21 CFR 175.105 / 175.320 / 176.170 / 176.180 / 177.1520, or other)
- Target softening point (Ring and Ball)
- Required documentation (TDS, COA, FDA compliance letter)
We will recommend a suitable grade and provide batch-specific COA data for your evaluation.
Request Hydrocarbon Resin TDS and COA →
References
- Brandrup, J.; Immergut, E. H.; Grulke, E. A. (Eds.). Polymer Handbook, 4th ed. John Wiley and Sons, New York, 1999. ISBN 0-471-16628-6.
- Kerton Industry. A Comprehensive Guide to Petroleum Resin: Principles, Types and Uses (industry technical background; non-hydrogenated C9 yellowing behavior, feedstock classification). [Industry background.]
- Jiang, M.; et al. "C9 Petroleum Resin Hydrogenation Over a PEG1000-Modified Catalyst." ACS Omega, 2020 (cited 35+). DOI: 10.1021/acsomega.0c02193. [Documents Gardner color reduction from No. 11 to No. 1 upon hydrogenation.]
- Eastman Chemical Company. Regalite and Plastolyn Hydrogenated Hydrocarbon Resins - Product Brochure (partial vs. full hydrogenation grades; compatibility data). Kingsport, TN: Eastman. [Supplier background.]
- Foreverest Resources Ltd. How to Choose Tackifier Resins for Non-Woven Adhesives (Hildebrand solubility parameter of common tackifiers; compatibility chart for SBCs and APAOs). [Industry background.]
- Ecopowerchem. Characteristics and Application Fields of Various Petroleum Resins (industry technical background). [Industry background.]
- ASTM International. ASTM D1544-04(2018) - Standard Test Method for Color of Transparent Liquids (Gardner Color Scale). West Conshohocken, PA: ASTM.
- Eastman Chemical Company. Picco AR-85 Hydrocarbon Resin - Sales Specification 75072-8 (Color Gardner, 50% in Toluene: 12 MAX per ASTM D-6166; Softening Point: 80–90 °C per ASTM D-6493). Kingsport, TN: Eastman. [Supplier TDS.]
- Lanxingco. The Ultimate Showdown: C5 vs. C9 Petroleum Resin (industry comparison; current revision). [Industry background.]
- iSuoChem. Hydrogenated C9 Hydrocarbon Resin for Pressure Sensitive Adhesives (S-90 to S-140 grades; Color Gardner 0#). [Supplier TDS.]
- Mardan BV. C9 Hydrogenated Hydrocarbon Resin - Water-White Velrez (product data; color stability, low odour, high thermal resistance). [Supplier TDS.]
- Kuraray. What Is a Tackifier? (industry technical background; compatibility of tackifiers with SIS, SBS, SEBS, EVA, APAO). [Industry background.]
- Kraton Polymers. Product Guide - Polymers (Kraton G grades; documents "better compatibility with more polar chemistries" for hydrogenated SEBS vs. unhydrogenated SBS). [Supplier background.]
- U.S. Code of Federal Regulations. Title 21 (Food and Drugs): 21 CFR 175.105 (Adhesives); 175.320 (Resinous and Polymeric Coatings); 176.170 (Paper and Paperboard, Aqueous and Fatty Food); 176.180 (Paper and Paperboard, Dry Food); 177.1520 (Olefin Polymers). Washington, DC: U.S. Government Publishing Office.
- ASTM International. ASTM D6166 - Standard Test Method for Color of Naval Stores and Related Products (Instrumental Evaluation of Gardner Color Scale). West Conshohocken, PA: ASTM.
