Sticky tapes extend their usefulness

New adhesive tapes can indicate whether something has got water soaked, transfer heat or electric current at the same time as providing secure joints, and permanently bond non wetting plastics. Applications for the latest products seem to be mainly in electronic products. It seems that most things can be stuck together with a something coming on a roll, and if nothing suitable seems to exist at present, vendors and manufacturers are quite prepared to find solutions, and if necessary, invent new ones. Some of the most ingenious developments come from masters of sticky tape, 3M. Steve Barwick, Sales and Marketing Manager of vendors Parafix, based in Lancing, was waxing eloquent of the virtues of Water Contact Indicator Tape 3M 5557 at the just held Southern Manufacturing Show. This material changes from white to red when water comes into contact with the edges of the tape, or if pinholes are added, with the face, but is not affected by damp. It is intended to show whether items such as mobile phones, laptops or other electronic consumable durables have been dropped in water, voiding their warranty, as opposed to failing due to susceptibility to mere damp or other environmental effects. The tape is manufactured in four layers: a PET printable top film, a paper backing to transport water but not damp, an acrylic adhesive and a polyester film liner. 3M has also recently developed thermally and electrically conducting adhesive tapes, that conduct heat and/or electricity at the same time as achieving good mechanical bonds. Barwick told Eureka that until recently, such materials either did one or the other well, but not both at the same time, because a high loading of conducting material tended to ruin mechanical strength. Now, however, Thermally Conductive Adhesive Tapes such 3M 8820 has a thermal conductivity of 0.60W/mºK and a 90º peel adhesion on aluminium of 17N/25mm at room temperature. It also survives soldering temperatures. It consists of a pressure sensitive acrylic adhesive carrier loaded with thermally conductive ceramic fillers, held between silicone treated polyester liners. Its electrical resistivity is 3.8 x 1011 ?-cm. Ground Heat Sink Bonding Film 7373 on the other hand is a hybrid epoxy/acrylate adhesive filled with silver coated glass beads to give it Z-axis electrical conductivity. Unlike straight epoxies, it has a 30% elongation to break, and a low angle peel strength of 44N/25mm width. In the non electrical sector, Davies Industrial Supplies, based in Letchworth told Eureka that as well as offering a range of more than 4,000 different adhesive tapes, they had a policy of responding to customer needs, by scouring the world to find whatever product would provide best solutions. Their latest offering, currently given the temporary designation, T7, is a modified rubber with 'scrim' (reinforcing cross threads) which is already being used to bond ABS to ABS to seal the edges of display screens, and is also capable of bonding polypropylene to polypropylene. Parafix Tapes and Conversions Davies Industrial Supplies Pointers * New 3M tape product indicates that a product has been immersed in water * Improved tapes for electronics combine both good thermal or electrical conductivity with good bond strengths * Products now exist capable of bonding normally non wetting plastics