Applied polymer science: which low-molecular-weight (below about 10^4), soft and waxy polymer is commonly used as a chewing-gum base ingredient?

Introduction:
Chewing-gum formulations rely on a food-grade, soft, and slightly tacky polymer base. The question checks recognition of PVAc as a classic gum base polymer due to its mouthfeel, film-forming ability, and safety profile in regulated applications.

Given Data / Assumptions:

• Target polymer is soft/waxy and low in molecular weight (sub-10^4 region).
• Food-contact compliance and taste neutrality are required.
• Processing involves plasticizers and flavors added to the base.

Concept / Approach:
Polyvinyl acetate provides suitable viscoelastic properties, acceptable adhesion, and compatibility with plasticizers. Alternatives like PVC or Thiokol are not food-grade choices; cellulose acetate can be film-forming but is not the standard gum base polymer in this context.

Step-by-Step Solution:
Identify candidate with food use track record: PVAc is widely cited as a gum base.Screen out engineering/industrial polymers (PVC, Thiokol) unsuited for ingestion.Confirm low-MW PVAc grades exhibit the soft, waxy characteristics described.Select PVAc as correct.

Verification / Alternative check:
Food additive references list PVAc (and certain elastomers) as common chewing-gum base components, blended with plasticizers like triacetin and resins.

Why Other Options Are Wrong:

• Cellulose acetate: used for films/coatings; not the principal gum base polymer.
• Thiokol: sulfur-based polysulfide rubber with strong odor, not food-grade gum base.
• PVC and LDPE: unsuitable for chewing gum bases under typical food regulations and performance needs.

Common Pitfalls:
Assuming any soft thermoplastic can serve as gum base; regulatory and sensory requirements are stringent.

Final Answer:
Polyvinyl acetate (PVAc)