Friction materials: composition, development history and technical requirements

Category Industry Insights Published 2026-04-02 Source www.boerfibre.com

Abstract

Friction materials are described as a polymer ternary composite — a physical and chemical complex made of polymer binders (resin and rubber), reinforcing fibres and friction modifiers, plus other additives. With a good friction coefficient, wear resistance, heat resistance and mechanical strength, they meet the transmission and braking requirements of vehicles and machinery, and are used on cars, trains, aircraft, oil rigs and other equipment. Functionally they are divided into brake linings and clutch facings; in the car industry they are critical safety parts.

The article traces the history: early pads used cotton, cotton cloth and leather dipped in rubber, which carbonised above 120°C; asbestos then became the main reinforcement — asbestos brake bands from 1905, moulded pads with asbestos short fibre and asphalt from 1918, and phenolic resin became the main binder in the early 1920s. By the 1960s asbestos health hazards were recognised; from the 1970s semi-metallic materials led by steel fibre were adopted abroad and occupied disc pads by the 1980s–90s; since the late 1990s NAO (non-asbestos, low-metal) materials have spread in Europe, overcoming semi-metallic drawbacks such as high specific gravity, rust, brake noise and excessive thermal conductivity.

On components: phenolic resin is the main binder, with requirements such as heat resistance, fine powder (100–200 mesh, preferably above 200 mesh), low free phenol (1–3%) and suitable cure speed (40–60 s at 150°C). Reinforcing fibres need good reinforcement, heat resistance, a basic friction coefficient, moderate hardness and processability. Fillers split into friction-increasing (Mohs hardness 3–9, e.g. alumina, zircon) and friction-reducing (below Mohs 2 — graphite, molybdenum disulfide, talc, mica). The article closes with technical requirements: friction coefficient (thermal fade above about 200°C; over-recovery; wet recovery), wear (thermal wear once the binder decomposes; the GB 5763-98 wear-rate method over 100–350°C), mechanical strength, and brake noise — generally no more than 85 dB, with noise tendency rising as the friction coefficient reaches 0.45–0.5 or higher.

Key facts

  • Definition: polymer ternary composite — binder (resin/rubber), reinforcing fibre, friction-modifying fillers
  • History: cotton/cloth/leather base (carbonises above 120°C); asbestos from 1905 (brake bands), 1918 (moulded pads); phenolic resin binder from the early 1920s
  • Asbestos-free transition: semi-metallic with steel fibre from the 1970s–80s; NAO low-metal materials from the late 1990s in Europe
  • Resin requirements: fine powder 100–200 mesh (preferably over 200); free phenol 1–3%; cure speed 40–60 s at 150°C
  • Fillers: friction-increasing Mohs 3–9 (alumina, zircon); friction-reducing below Mohs 2 (graphite, MoS2, talc, mica)
  • Friction coefficient: starts dropping above about 200°C; noise easily triggered at 0.45–0.5 or higher
  • Noise limit: generally brake noise should not exceed 85 dB
  • Wear method: GB 5763-98 wear-rate method over 100–350°C

The original article is in Chinese; see the Chinese version for the full text. This page provides the English title, abstract and key facts only — translated and compiled from the original, without full verbatim translation.