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|PRODUCT DATA of 11: Adhesive tapes and films|
|Material||11: Adhesive tapes and films|
|General Information||Tapes can be an integral part of a flight assembly or be used as a temporary aid during the assembly of parts.|
|Use in Spacecraft||In existing satellites, adhesive tapes are used mainly in the thermal-control subsystems. They function either as thermal-control surfaces themselves or are used in assembling thermal blankets. They can also be used in electrical insulators. Such tapes can be used extensively during qualification tests as a means of attaching sensors and temporary wiring to the spacecraft. Adhesive tapes are easy to handle, can be cut to size and used to make patterns. They can be removed easily after temporary use.
Some conductive adhesive tapes are used for electrical grounding.
|Main Categories||The backing of adhesive tapes can be made from polyester, polyimide, polyolefin, fluorinated polymers, fibreglass cloth, metal sheet, metallized (aluminized, gold-plated) polymers and pigmented polymers.
Most common tapes have a "pressure-sensitive" adhesive based on rubber-like polymers containing a number of additives (e.g. tackifiers and plasticisers), and the composition is normally proprietary. Basic rubber-like polymers used are, for example, natural rubber, acrylates, acrylic rubbers, silicones and butyl.
Adhesive tapes are sold in rolls of different widths with or without an intermediate liner. Some can be heat or solvent activated. Thermosetting adhesive tapes also exist. Transfer tapes (2 adhesive sides), supported or unsupported, find extensive use in the bonding of metallized films.
|Processing and Assembly||The processing and use of adhesive tapes appear to be extremely simple; cut to size and apply. One should, however, ensure that the adherent surface is clean enough, that the application pressure is even and that the tape surface is not damaged during the application.Sometimes tapes shall be perforated all over their surfaces; this allows evacuation of trapped or generated gas bubbles under vacuum (particularly with metal-backed tapes).|
|Precautions||Because of the complex and frequently unknown nature of their adhesives, use of tapes should be minimized and then only with great care in their choice and application. When an adhesive tape is applied temporarily, it generally contaminates the underlying surface which shall be carefully cleaned after tape removal. When tape is applied permanently it can be displaced by creep and leaves a dirty spot. Cleaning solvents can accidentally damage the adhesive or the tape, or be absorbed into them and diffuse out when vacuum exposure takes place. The top face of some adhesive tapes is coatedwith a release agent that can discolour during subsequent vacuum or UV exposure - this should be removed|
|Hazardous and Precluded||Polyvinylchloride backing tapes which are frequently used for electrical insulation shall not be applied to space vehicles. Also cellulose (cellophane), cellulose acetate,
Paper and fabric should be avoided. Tape of unknown origin shall not be used.
|Effects of Space environment||Vacuum exposure can draw products out of the backing when it is a polymer and also out of the adhesive. When the tape is applied, outgassing takes place through the backing by diffusion when it is permeable and also through the bond line. Outgassing products and entrapped air can lift the tape or bubble it unless the tape is perforated. Adhesives mainly generate condensable products which are dangerous contaminants for optics and electronics. The release of such products, which are frequently plasticisers or tackifiers, can harden the adhesive layer and render it inoperative. Practically each new type of tape shall be tested for outgassing: present results do not allow a generalized statement to bemade regarding safe tapes for space application, but acrylic adhesives seem to be the better choice.
|Some Representative Products||Materials which can be considered: