Silk Fibre Properties Analysis

Silk is a natural protein fibre derived from silkworms. Its physical characteristics determine its suitability for various applications. Let's analyze the given properties:

Property (a): Smooth Fibre

Silk fibre is known for its naturally smooth surface. This smoothness arises from the long, continuous filament structure produced by the silkworm, contributing to its lustrous appearance and soft feel.

Property (b): Moderate Elongation

Silk possesses moderate elasticity. It can stretch considerably before breaking, typically exhibiting an elongation at break ranging from 20% to 35%. This property allows fabrics made from silk to withstand moderate stress.

Property (c): Density

The density of silk fibre is approximately 1.3 - 1.4 g/cm³. While not as light as some synthetic fibres, it is generally considered to have a moderate density, not a high density compared to materials like glass or certain metals.

Property (d): Moisture Regain

Silk has a moisture regain percentage of around 10-11% at standard conditions. This is considered moderate. It absorbs moisture better than hydrophobic synthetic fibres (e.g., polyester, < 1%) but less than highly hydrophilic fibres like cotton (around 7-9%) or wool (around 13-18%). Therefore, describing it simply as 'low' can be misleading without context.

Conclusion on Silk Properties

Based on standard textile knowledge, silk is accurately described as having a smooth fibre texture and moderate elongation capabilities. Properties (c) and (d) are less precise descriptors; its density is moderate, and its moisture regain is also moderate, not distinctly low compared to all other fibres.

Therefore, the correct physical properties among the choices are (a) and (b).