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Automotive Weatherstrips
Automotive WeatherstripsRubber has for many years been used for sealing purposes in a vehicle. It is flexible and resilient and can be extruded relatively easily. The seals for automotive windows, door, light, boot, etc., may all be considered as weatherstrips or weatherseals. In the early '70s, automotive weatherstrip was made from a single rubber, mainly natural rubber which has excellent resilience but relatively poor weathering resistance. Towards the end of the 70s, EPDM had become dominant primarily because of its superior weathering and ozone resistance coupled with its high filler acceptance and wide processing capabilities.
Manufacturing process

Modern automotive weatherstrip for door and boot seals commonly consists of solid or co-extruded solid and cellular profiles whilst window seal profiles can contain a metal insert for added stiffness or be multiple co-extrusions of different hardness compounds. Rapid curing of the extruded profile is achieved at high temperature by a continuous vulcanisation procedure such as microwave, liquid curing medium (LCM) or the fluidised bed (Ballotini) method.
  • Preparation of rubber compound

  • In choosing a compound for use as weatherstrip, a number of considerations have to be made. In its uncured state, the extruded profile must possess high green strength to prevent collapse and so maintain its correct shape. The surface finish of the extruded profile must also be very good. Mixing of the rubber compound can be carried out on a two-roll mill or in an internal mixer. In the case of an internal mixer, it can be done in a single-stage or a double-stage mixing. Curatives are normally added on a two roll mill.

  • Determination of scorch time, cure characteristics and physical testing (e.g., hardness, tensile properties, tear resistance, rebound resilience, compression set, flex-cracking resistant and ozone resistance).

  • The above properties are necessary before the compounds can proceed to the subsequent fabrication process such as extrusion.

Door Outer
Door Outer

Tail gate/trunk lid
Tail gate/trunk lid

Door opening inner
Door opening inner


  • Fabrication and curing of the weatherstrip

  • The profiles are extruded and good surface finish appearance is required especially if the product is used in a highly visible part of a car where aesthetic appearance is highly important. Curing is normally carried out continuously using microwave, LCM or Ballotini. A single extruder or a combination of extruders are commonly used to produce weatherstrip, depending on whether the product is of one solid profile, co-extruded solid and cellular profiles or one that contains two or more solid profiles of different hardnesses.

  • Jointing

  • The extruded profile is then transferred to the jointing presses whereby the cut pieces are joined together by the presses into its finished form.

  • Assembly on the vehicle
Other Info
  Processing Flow Chart
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