Crystallisation of celluloid (a nitrate–camphor plastic) is undesirable; which additive is traditionally used to prevent crystallisation and maintain flexibility?

Introduction / Context:
Celluloid, one of the earliest commercial plastics, is based on cellulose nitrate plasticised with camphor. Control of crystallisation and brittleness was a key historical challenge; plasticisers disrupt chain packing, improving flexibility and processability.

Given Data / Assumptions:

• Celluloid = nitrocellulose + plasticiser.
• We seek the classic additive that prevents crystallisation and embrittlement.
• Options include common additives and components.

Concept / Approach:
Camphor acts as a plasticiser: it interposes between polymer chains, reduces intermolecular attractions, and inhibits ordered packing, thereby limiting crystallisation. This maintains clarity and flexibility. Glycerol plasticises some hydrophilic polymers but is not the traditional agent in celluloid. Nitrocellulose is the polymer itself, not an additive. “None” is invalid because the well-known plasticiser is camphor.

Step-by-Step Solution:
Recall composition of celluloid: nitrocellulose + camphor.Recognise camphor’s role in suppressing crystallisation and brittleness.Eliminate distractors that are either base polymer or unrelated plasticisers.

Verification / Alternative check:
Historical manufacturing notes and museum conservation literature cite camphor as the principal plasticiser in celluloid objects.

Why Other Options Are Wrong:
Glycerol: used with PVA or gelatin systems, not classic for celluloid.Nitrocellulose: not an additive; it is the base polymer.None: incorrect because camphor is correct.

Common Pitfalls:
Confusing moisture plasticisation (e.g., glycerol in hydrophilic polymers) with organic plasticisers used in early plastics.

Final Answer:
Camphor