Curing phase

A typical resin has an initial molecular weight of 150 to perhaps 1500. For systems of unsubstituted phenols, the final cross-link density is 150—300 atomic mass units (amu) per cross-link. In other words, 25—75% of the ring-joining reactions occur during the cure phase. 

Equations 5.9-5.12 can be used for conservation of total mass of the resin under various conditions. To keep track of the degree of cure of the resin we need to write a separate mass balance for the cured phase a ... 

Bulky side chains in the hard segment will tend to make the hydrogen bonding more difficult. The bulky side chains of Ethacure 300 will lower the hardness of a material by several points compared to that of a material cured with MOCA. The use of triols or macro diols in the curing phase will have a softening effect. If a trifuctional isocyanate or hydroxyl is used in the initial preparation of the prepolymers, this softening does not happen. 

Morrall67 concluded that the initial adsorption step for 7-aminopropyltriethoxysilane (APTS) takes less than 18 s, which was the shortest measurable time. The ultimate orientation of the aminopropylchain (amine near the surface or pointing away from it) is determined by the presence of water in the reaction and curing phase.72 Kallury73 demonstrated that the addition of a base in the reaction also reduces the amount of... 

Concluding, the processes occurring under various curing conditions have been modelled. In the curing phase, the aminosilane layer is stabilized by covalent bonding to the surface. Siloxane bonds are formed between silane and silica surface atoms. The velocity of the siloxane formation is dependent on the initial number of ethoxy... 

However, if the refractive indices of the two components are identical Rayleigh scattering will not occur [110]. Due to the various values of refractive indices of epoxy and polyimides quoted in the literature [2] (this is speculated to be a function of crosslink density, monomers used and state of cure) phase separation of epoxy systems can only be inferred and not quantitatively determined visually. 

The swelling is simulated mathematically by repeating the stress calculation with the elastic modulus for the noted layers temporarily considered as zero. This second calculation reflects the actual stresses in the layers at the end of the cure phase. For subsequent calculations the elastic moduli are restored to their original values. 

Table 47-4 displays the stresses in the layers after the cure phase has cooled to the installation temperature. These stresses can be used as a base from which stress changes can be calculated for all other conditions. 

The role of the triphenylphosphine is similar in the rubber-modification reaction. In this case however the betaine abstracts a proton from the carboxylic acid. The carboxylate anion attacks the electrophilic carbon attached to the phosphorus forming an ester linkage and regenerating the catalyst. The rubber is terminated on both ends by epoxides and can later be crosslinked into the epoxy matrix during the coating and curing phases. This sequence is shown in Reaction Scheme 5. 

In an acidic curing phase, the precondensates enriched on the surface of the drops are further reacted to form a dense network. 

For in-situ monitoring processes such as curing, phase separation or even ageing, the interpretation of the spectra and the assignment of the bands are critical. 

The engineer will be concerned with the behaviour and performance of the selected adhesive from the time he first purchases it from the manufacturer, through the mixing, application and curing phases to its properties in the hardened state within a joint over the intended design life. Thus the properties of interest in approximate chronological order are likely to include ... 

Benzoxazine Single Tgi Tm-depression Miscible before curing phase separadcHi after curing Lu and Zheng (2003)... 

Batch systems using the prepolymer route plus the addition of a catalyst to reduce the chain-extension time and, in particular, to reduce or eliminate the post-curing phase. 

Something similar can be done using different approaches for example, the immediate use of a silicon substrate allows the avoidance of the curing phase (Arstad et al., 2006). 

Automation considerations. The layup of a composite, the actual placement of plies in their expected final position in the laminate, cannot be separated from the total manufacturing process in some procedures, e.g., filament winding or pultrusion. In other techniques, e.g., automatic tape laydown or RTM, the layup process is a separate batch process and is completely separate from the compaction and cure phase. AU composite manufacturing processes can be automated to some extent, and the amount of automation depends on how amenable the optimum manufacturing technique is to total or partial automation, the capital costs of the automation machinery, eventual total number of piece parts to be manufactured, the expected cost of each, the time frame available, and a host of other factors. 

---