Substrate temperature with cure time

Variation of Substrate Temperature with Cure Time. For a thin substrate placed in an oven,set at a constant temperature,... 

Depending on the scale of production, HTV can be used for all applications as described in Section 11.4. The only limitation is the speed of curing and the respective moulding temperatures. In all cases HTV cures slower and at higher temperatures than LR. In most cases this moulding temperature and curing time is responsible for the fact that it is hard to combine plastics with HTV. Most typically, metals, steel, iron, etc., will be the substrates. 

Polished steel substrates primed with plasma polymerized acetylene films were immersed into a stirred mixture of these materials at a temperature of 155 5°C to simulate the curing of rubber against a primed steel substrate. During the reaction, the mixture was continuously purged with nitrogen to reduce oxidation. At appropriate times between 1 and 100 min, substrates were removed from the mixture, rinsed with hexane ultrasonically for 5 min to remove materials that had not reacted, dried, and examined using RAIR. The RAIR spectra obtained after reaction times of 0, 15, 30, and 45 min are shown in Fig. 13. 

Silicone adhesives are generally applied in a liquid and uncured state. It is therefore the physical and chemical properties of the polymers, or more precisely of the polymer formulation, that guide the various processes leading to the formation of the cured silicone network. The choice of the cure system can be guided by a variety of parameters that includes cure time and temperature, rheological properties in relation with the application process, substrates, the environment the adhesive joints will be subjected to and its subsequent durability, and of course, cost. 

Lithographic Evaluation. Films were spin-coated onto silicon substrates from 10% solutions in chlorobenzene and prebaked at temperatures between 90 °C and 100°C for 1 hour to ensure solvent removal. The thickness of each film was about 5000 A. Electron beam exposures were performed on the AT T Bell Laboratories electron beam exposure system (EBES-I) operating at 20 kV with a beam adress and spot size both equal to 0.25 . A minimal cure time was required since there is no post-exposure reaction (4,16). 

Once the tape or film is in place between the substrates, the joint is heated under pressure so that the adhesive becomes slightly fluid, flows into the microroughness on the substrate, and wets the substrate. With additional time at the curing temperature, the adhesive completely crosslinks to a thermosetting condition. 

Consequently, relatively short cycles at lower temperatures allow the use of polymer substrates with lower melting temperatures and less sensitivity to heat treatment as the contact times (curing times) decrease much more than the cycle times. 

Ex. 1. Tuftane film is ideally suited for bonding emblems, numerals, and letters to many fabrics by heat and pressure alone. It also flame-bonds well to both polyester- and polyether-urethane foams at commercial bonding speeds. Since it contains no volatiles it does not require cure times as do solvent- or water-based adhesive systems. All Tuftane films can be adhered thermally by hot bar, thermal impulse, ultrasonic, or dielectric methods over a wide range of temperatures. Adhesive lamination to many substrates is possible by the heated drum, curing oven, or multiple can methods. Fabric bonds made with Tuftane are strong and withstand laundering and dry cleaning. 

Majof silicone suppliers have been developing radiation-curable coatings for some time now the solventless systems lend themselves to this approach since all the space radiant energy can be directed at the polymer system for curing, and none wasted for solvent evaporation or in the substrate. The energy source referred to may be either ultraviolet or electron-beam radiation, and the objective is a very rapid zero-temperature controllable cure, with much of the control occurring through the intensity of the source. 

Once the joint is formed, the adhesive is cured according to the manufacturer s instructions. Adhesive data sheets usually specify a recommended cure schedule (temperature and time) and often a recommended pressure to be applied to the joint. Sometimes a range of cure schedules are quoted. It is important to ensure that the adhesive layer (as opposed to just the oven or even the jigging) reaches the cure temperature for sufficient time for full cure to be achieved. Massive jigs and large metallic substrates can very much increase the thermal inertia of the joint and the time taken for full cure to be achieved. A thermocouple wire placed in one end of the bondline can be used to confirm the thermal history of the adhesive layer during manufacture. When the cure is complete, the joints are removed from the jig and the adhesive fillets are removed to make a joint with smooth sides. 

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