Hard rubber (ebonite) is a thermoset material produced by vulcanizing natural or synthetic rubber with a high proportion of sulfur; it cannot be re-melted and reshaped. Thermoplastic elastomers, by contrast, soften and flow when heated and are classified in Chapter 39 (plastics). Laboratory analysis of sulfur content and thermal behavior, along with the manufacturer's material specification, are the primary tools for resolving borderline cases. A CBP binding ruling is recommended when the material composition is uncertain.

Yes. The heading text explicitly includes hard rubber in all forms—rods, sheets, tubes, granules, and powder—as well as waste and scrap of hard rubber, alongside finished articles. This makes 4017 unusual within Chapter 40 in consolidating raw material, intermediate forms, and finished goods under a single subheading (401700).