1. Introduction

The carpet and rug industry utilizes a variety of synthetic and natural fibers for warp, weft, and pile yarns. The main difference between carpet and clothing fibers is their diameter. Generally, carpet fibers are thicker than clothing fibers. The primary fibers for carpets and rugs are nylon, polypropylene, and wool.
While natural fibers find their place in the artistry of hand-woven rugs, the realm of machine-made and tufted carpets is predominantly ruled by synthetic fibers. Among these, polypropylene has exceptional properties, making it a popular choice for pile, warp, and weft yarns. Its unique characteristics are a fascinating subject of study and application in the carpet industry.

2. Structure and Properties of Carpet Fibers

Carpets are woven from various fibers, generally categorized into two main groups: natural and synthetic. Here, we will examine some of these fibers.

Synthetic Fibers

1. Nylon

Nylon is a highly resilient polyamide, making it suitable for producing machine-made carpets. These fibers are durable, resistant to stains and shedding, and available in filament and staple.

2. Acrylic Fibers

Acrylic fibers are made from acrylonitrile and possess easy dyeability, high bulk, and washability characteristics. Due to their low resilience, acrylic fibers are not particularly suitable for carpet manufacturing but are generally used as carpet yarn.

3. Polypropylene Fibers

Polypropylene fibers are resistant to sunlight, lightweight, waterproof, and cost-effective, making them ideal for various carpets. Due to their low cost, technological improvements, and performance, polypropylene fibers are quickly gaining market share from nylon.

Table: Physical properties of carpet-grade fibers

Table: Physical properties of carpet-grade fibers 

4. Polyester Fibers

Excellent shape retention, resistance to stains, and softness are among the advantages of polyester fibers, making them suitable for high-pile carpets. However, these fibers’ low resilience and difficult dyeability are considered their weaknesses.

Natural Fibers

1. Wool
   Wool is a natural fiber obtained from the hair of animals such as sheep, goats, etc. Due to its complex chemical structure, these fibers are excellent thermal insulators. Wool is divided into two main categories: clothing wool and carpet wool. Carpet wool is used in the production of traditional hand-woven carpets. Australia, South Africa, and New Zealand are among the world’s significant producers of carpet wool. Wool is structurally composed of cortical and cuticular cells. These fibers are naturally fire-resistant.
2. Silk
   Silk is also a protein fiber obtained from the silkworm’s cocoon. These fibers are very soft, delicate, and shiny. Silk is used in the production of exquisite hand-woven carpets. Countries like India and Iran produce high-quality silk carpets.
3. Jute
   Jute is a fiber obtained from the jute plant. In the past, these fibers were used as the primary warp and weft fibers. Nowadays, synthetic fibers like polypropylene have replaced hemp in machine-made carpets. Processed jute is also used to make warp yarns for carpets and rugs. Jute carpets are known for their low-quality reputation.
4. Cotton
   Cotton is a plant fiber obtained from the cotton boll. These fibers are soft, absorbent, and breathable and are extensively used in producing clothing, various textiles, and carpets.

3. Carpet Yarn Quality and Control

Carpet yarn is the most essential raw material for carpet and rug production. A carpet is quality heavily depends on the quality of its yarn, which in turn depends primarily on the quality of the fibers used. All these criteria are interconnected.

To ensure that carpet manufacturers have suitable raw materials for their products, meticulous quality control, process control, and inspection are always recommended. Below are the most important properties to be evaluated in the fiber selection stage:

• Fiber diameter
• Fiber length
• Crimp percentage
• Dyeablity

For wool-based yarns, the properties to be evaluated include:

• Count
• Ply
• Non-wool fiber content %
• Residual grease content %
• Average fiber length
• Twist per inch
• Vegetable matter content

All of these criteria or parameters significantly impact the properties of the yarn. Each individually contributes to the final characteristics of the yarn, ultimately determining the qualities of the carpet produced.

4. Future Trends

Wool yarns will continue to have a significant share in the production of hand-woven carpets. However, another essential trend observed today is the increasing use of synthetic fibers instead of wool in carpet production. There will be a greater emphasis on producing specialty carpets and rugs in the future, leading to innovation in producing suitable yarns. Specialty carpets include:

• Medical Carpets: Using carpets in hospitals or any medical clinic, considering strict quality requirements for hygiene, traffic, and maintenance, is a very sensitive issue. Carpets specially designed for medical applications must be of a quality that does not absorb dust or any type of contamination and is also easily washable.
• Anti-static Carpets: The most common electrostatic problem associated with carpets occurs when a person walks on carpets without a cover and builds up an electric charge, resulting in a shock. Even woolen carpets are susceptible to such issues when used in low-humidity environments.
• Hot Carpets: These carpets are used for automatic heating and evoke a blanket-like feeling.
• Aircraft Carpets: These carpets must pass rigorous flammability tests.