Why Liquid and Solid Silicone Rubber Share the Same HS Code?
Introduction
The Harmonized System (HS) is a globally standardized classification system used for trade tariffs and customs documentation. Interestingly, both Liquid Silicone Rubber (LSR) and Solid Silicone Rubber (SSR) often fall under the same HS code, even though they differ significantly in physical state and processing methods. This article explores why these two forms of silicone rubber are classified together despite their distinct properties.
1. HS Code Classification Principles
The HS code system categorizes goods based on:
Material composition (primary factor)
Function and application (secondary factor)
Form (liquid/solid) is often less critical than chemical structure
Since both LSR and SSR are fundamentally polysiloxane-based elastomers, they are grouped together under the same broad category, typically:
HS Code 3910.00 (Silicones in primary forms)
HS Code 4006.10 (Rubber in primary forms, if classified as rubber rather than plastic)
2. Why Form (Liquid vs. Solid) Doesn't Always Change the HS Code
A. Same Chemical Base Material
Both LSR and SSR are made from polydimethylsiloxane (PDMS).
The HS system prioritizes chemical composition over physical state.
B. Intended Use in Manufacturing
LSR is typically a two-part liquid that cures into a solid elastomer.
SSR is a pre-vulcanized solid that requires further molding.
However, both are intermediate materials, not final products, so they fall under the same "primary forms" classification.
C. Packaging and Handling Differences Are Not Classification Factors
LSR is shipped in barrels or cartridges (liquid).
SSR is shipped as sheets, strips, or bales (solid).
Customs focuses on what the material is, not how it is packaged.
3. When Do LSR and SSR Have Different HS Codes?
While they often share the same code, exceptions occur based on:
| Scenario | LSR Classification | SSR Classification | Reason |
|---|---|---|---|
| Precursor vs. Processed Material | 3910.00 (silicone prepolymer) | 4006.10 (rubber in primary forms) | If SSR is already partially cured |
| Medical vs. Industrial Grade | 3006.70 (medical devices) | 4016.93 (industrial rubber parts) | Different end-use applications |
| Additives & Reinforcements | 3910.00 (pure LSR) | 4006.91 (filled SSR) | Additives like silica can shift classification |
4. Practical Implications for Importers & Exporters
A. Potential Misclassification Risks
Assuming all silicone rubber is classified under 4006.10 (some may fall under 3910.00).
Overlooking additives that could change the HS code.
B. Best Practices for Accurate Classification
Check the curing mechanism (LSR is often a reactive liquid, SSR is pre-vulcanized).
Verify end-use applications (medical, automotive, etc.).
Consult customs rulings for specific product classifications.
Conclusion
Although Liquid Silicone Rubber (LSR) and Solid Silicone Rubber (SSR) differ in form, they frequently share the same HS code because customs classification prioritizes chemical composition over physical state. However, variations in curing mechanisms, additives, and end-use applications can sometimes lead to different classifications. Businesses trading silicone rubber should carefully analyze their product's exact specifications to ensure correct HS code assignment and avoid customs disputes.