Traditional toothbrush bristles are commonly manufactured from which polymer grade due to its stiffness, abrasion resistance, and moisture tolerance?

Introduction / Context:
Filament applications (e.g., toothbrush bristles, fishing line, textile fibres) require a balance of stiffness, resilience, abrasion resistance, moisture uptake, and processability. The nylon family (polyamides) has long dominated bristle applications owing to these properties.

Given Data / Assumptions:

• We consider conventional manual toothbrush bristles.
• The industry standard historically references nylon grades tailored for filament extrusion and end-rounding.

Concept / Approach:
Nylon-6 is widely used for toothbrush bristles due to its good flex-fatigue resistance, suitable moisture absorption (which softens bristles slightly in use), and ability to be precision-drawn into uniform filaments. Nylon-66 is used in some specialty filaments but is less common for standard toothbrushes. Polystyrene is brittle and unsuitable for repeated bending. PVC lacks the resilience and hygienic performance required for high-quality bristles.

Step-by-Step Solution:
Match application demands (fatigue, abrasion, moisture tolerance) with polymer properties.Select nylon-6 as the typical choice for bristles.Eliminate alternatives that lack required resilience or biocompatibility traits.

Verification / Alternative check:
Product specifications from bristle manufacturers frequently list PA6 (nylon-6) for mainstream toothbrush lines; PA612/PA610 may appear in premium variants, but PA6 remains a canonical answer in standard MCQs.

Why Other Options Are Wrong:
Nylon-66: more common in engineering fibres where higher heat resistance is needed; not the typical bristle baseline.Polystyrene: too brittle and poor fatigue performance.PVC: insufficient resilience and tactile performance for bristles.

Common Pitfalls:
Assuming any nylon works equally well; subtle differences in moisture regain and bending fatigue matter for user comfort.

Final Answer:
Nylon-6