Adhesives, Tape, and Other Polymer Evidence

Laboratories and analysts allocate their time and effort to those areas which appear most promising. On the basis of the preceding discussion, it should not be surprising that some types of fiber evidence are deemed too common to be of evidentiary value. A 2001 survey revealed that about half the responding laboratories in the United States and Europe did not routinely examine undyed cotton fibers. Blue denim is not routinely analyzed in 20% of U.S., and nearly 50% of European, laboratories. The decision to analyze or not to analyze a particular kind of fiber is based on knowledge of the background environmental level of the fiber. 

Synthetic fibers and textiles are not the only type of polymer evidence analyzed by forensic chemists. All kinds of materials, such as building materials and PVC pipes, may be submitted as exhibits. Among the more frequent types of evidence are adhesives and tapes, most of which are based on or include polymeric substances. Tape is also frequently used to collect evidence fibers are often collected by adhesion to inside-out rolls of tape. Gunshot residue can also be collected this way. Tapes of the most forensic interest consist of a polymer backing with a pressure-sensitive adhesive coated on one or both sides, as in the case of double-sided tape. Within this group are foimd cellophane tape (informally, Scotch tape ), as well as duct, packing, and electrical tape. 

Source Regert, M., and C. Rolando, Identification of Archaeological Adhesives Using Direct Inlet Electron Ionization Mass Spectrometry, Analytical Clianishy 74 (2002), 965-975. 

Super glue is used to close wounds and to develop fingerprints on substrates such as aluminum cans. How does this process work  

Answer The same way that super glue works to bind cellulose with available —OH groups which act as initiators. Recall that proteins are composed of amino acids that have —COOH groups which can act as initiators. Fingerprints contain residual proteins that polymerize into a white plasticky polymer that can be hirther developed to enhance visualization. 

---