Felt Used in the Automotive Industry

Felt, known as one of the oldest textile materials, is a highly functional and versatile material. Some of the main areas where felt is used include musical instruments to reduce vibrations, clothing and tents, the automotive industry, and many other fields. In this article, we will focus specifically on the types of felt used in the automotive sector. Felt is also widely used in automotive filters.

Filters are mostly produced from polypropylene and polyester felt due to their compatibility with fluids and chemicals. During the production of felt filters, no adhesives, binders, or silicone materials are used.

Benefits of Automotive Filters Made from Felt

The advantages of automotive filters produced using felt can be listed as follows:

• They do not form mold, bacteria, or fungi
• They are organic and natural
• They are harmless to human health and the environment
• They are breathable and allow air permeability
• They are suitable for all climate conditions
• They are soft, lightweight, and voluminous
• They are suitable for all types of washing and dry cleaning

Air filters are required to operate reliably even under the harshest conditions. For this reason, a pre-separator is additionally used in dusty and challenging environments. This component, which may consist of a foam layer or a metal or plastic mesh, serves to provide support in the airflow direction. In very humid regions, filters coated with waterproof felt materials act as pre-filters.

In addition to air filtration, filters are also expected to reduce intake noise. For example, in commercial vehicles, durable air filter systems made from recyclable materials and optimized for weight are commonly used. These filters are generally designed in cylindrical shapes and equipped with radial seals. Due to shrinking installation spaces, flatter filter designs have become more common in recent years. Additionally, during filter maintenance and replacement, a special felt is used to protect the clean side of the filter.

SMF filter papers are designed with a pleated structure to retain dirt and create a larger surface area within a small space. If these pleats are not sufficiently stable, pleat deformation may occur. Pressure differences can compress the pleats excessively, restricting or completely blocking airflow through the filter. As a result, filtration performance deteriorates, filter lifespan is reduced, fuel consumption increases, and harmful emissions rise. Therefore, pleats in passenger vehicle air filters are often reinforced with adhesive.

Automotive Felt Usage

First, cellulose is impregnated with a special resin using a complex process. This treatment helps maintain pleat stability and prevents deformation. Next comes the preheating stage, which prepares the paper for the shaping process known as embossing. After that, the paper is folded according to the required design. Once folding is complete, a curing process is applied to provide mechanical strength as well as chemical and thermal resistance.

Filter felts are made from synthetic fibers whose thickness is measured in microns. The finer the fiber, the better the separation performance. Felts are manufactured in layers, with density and fineness increasing from the dirty side to the clean side. This phenomenon, known as the “funnel effect,” enables high dirt-holding capacity while maintaining low airflow resistance. Multilayer filter materials consist of a combination of paper and felt. Although their production processes are quite complex, compared to traditional paper filters, they can offer up to 40% higher dirt-holding capacity at a similar level of filtration efficiency.