Pot life Determination

Before making the castings, pot life determinations were performed to determine the processing window of the prepolymer and chain extender materials. As a standard practice, both the prepolymer and chain extender were preheated to the desired temperatures, degassed thoroughly, mixed at the desired stoichiometry (90 or 95%) and poured into a thermostatted vial. The viscosity was measnred, nsing a Brookfield viscometer, as a function of time. The measurements were terminated when either the time of measurement reached 20 minutes or the viscosity of the mix reached 0.1 Pa-s. 

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Pot life determinations were done using a Brookfield viscometer at controlled temperatures. 

The experimental details on the pot life determination and elastomer casting conditions... 

When formulating a silicone adhesive, sealant, or coating, based on hydrosilylation addition cure, one must consider the following properties of the uncured product pot life, dispensing technique, rheology, extrusion rate, cure performance. These characteristics directly affect the processing properties of the polymer base or crosslinker parts. The degree of cure conversion at the temperature of interest is determined by properties such as tack free time, cure profile and cure time. Once... 

Two-component systems consist of (1) polyol or polyamine, and (2) isocyanate. The hardening starts with the mixing of the two components. Due to the low viscosities of the two components, they can be used without addition of solvents. The mass ratio between the two components determines the properties of the bond line. Linear polyols and a lower surplus of isocyanates give flexible bond lines, whereas branched polyols and higher amounts of isocyanates lead to hard and brittle bond lines. The pot life of the two-component systems is determined by the reactivity of the two components, the temperature and the addition of catalysts. The pot life can vary between 0.5 and 24 h. The cure at room temperature is completed within 3 to 20 h. 

The target of the development of adhesive resins is to achieve high reactivities mitigated by consideration of the storage stability of the resin or the pot life of the glue mix. The reactivity of a glue resin and of a glue mix is determined by various parameters ... 

In order to prolong the pot life of the system, a reduction in polydispersity is quite important. Shape polydispersity of the polymer, which is determined by the distribution of topological isomers, is expressed through a quantity Frechet and coworkers originally termed degree of branching [78], which reaches unity for... 

The supplier s recommendations should be noted so that an adequate pour time is obtained. Pot life times quoted on the specification sheet are in many cases determined by laboratory size samples where the effect of the bulk of material is less than in a large mix. In a large mix, the poor conductivity of... 

Many different test methods are used to measure the reactivity or cure rate of the epoxy adhesive. Some of these, such as working life or pot life, are very practical and are used to plan the production process. Others, such as exotherm, are used to determine reaction kinetics. Still others are used to characterize the epoxy network as it cures for the purposes of determining the degree of crosslinking and the rheological properties of the curing adhesive. 

Solids content Viscosity pH Gel time and pot life Dr5lng the sample for 2h at 120°C results can be influenced by the test parameters Using a rotation viscometer or Ford cup (DIN cup) Direct measurement using pH electrodes Simplified method to determine the resin s gel time Gel time at 100°C or at 70°C Pot life at 20°C or at 30°C B-time for PF resins at 100 to 140°C ... 

The importance of monol content in 4,T-MDI/BDO cured elastomer systems was determined by comparing 4000-MW PPG diols prepared via ultra-low monol technology, DMC and potassium hydroxide. They are designated as ultra-low monol, low monol and conventional and have monol contents of 0.005,0.016 and 0.085 meq/g, respectively. This corresponds to functionalities of 1.98, 1.94 and 1.71. We prepared 6% NCO 4,4"-MDI prepolymers and chain extended with BDO at an isocyanate to hydroxyl ratio (NCO OH) of 1.03 [15]. Table 9.3 summarises the monol effect on elastomer processing characteristics (pot life and demould time), and physical properties. 

Table 2.4. Pot life in minutes for a range of adhesives, determined by various methods (Ref. 14)... 

British Standards Institution. BS 5350 Part B4, British Standard Test Methods for Adhesives Determination of Pot Life, BSI, London, 1976. 

Two processes are available which use liquid resin systems. In the first the reinforcement is drawn through an impregnating bath containing catalysed resin. For this process, a resin system with a long pot-life at room temperature is necessary. The reinforcement is then drawn through a heated die which removes excess resin, determines the cross-sectional shape and cures the resin system. 

One-part epoxy adhesives include solvent-free liquid resins, solutions in solvent, liquid resin pastes, fusible powders, sticks, pellets and paste, supported and unsupported films, and preformed shapes to fit a particular joint. Two-part epoxy adhesives are usually comprised of the resin and the curing agent, which are mixed just prior to use. The components may be liquids, putties, or liquid and hardener powder. They may also contain plasticizers, reactive diluents, fillers, and resinous modifiers. The processing conditions are determined by the curing agent employed. In general, two-part systems are mixed, applied within the recommended pot life (a few minutes to several hours), and cured at room temperature for up to 24 hours, or at elevated temperatures to reduce the cure time. Typical cure conditions range from 3 hours at 60°C to 20 minutes at 100 C. ... 

Tests on adhesives to determine their curing or setting behaviour, for example, tack-free time, skin-over time, pot life, and so on. 

The typical pot life of many two-component polyurethane elastomer resins is a few minutes and the initial viscosity is in the vicinity of 20,000 cps at 20°C. Obviously, drops of such resin types cannot be used with narrow glass applicators or the knotting method. Typical viscosities of epoxy resins are in the range between 500 and 1000 cps and pot lives between 15 and 60 min. In order to determine the adhesion of elastomer resins, it was necessary to develop a new method. A further aim was to investigate the influence of the characteristics of the fiber surface on the mechanical properties of elastomer composites. 

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