Thermosets partially cured

The cloud point curves of the epoxy monomer/PEI blend and BPACY monomer/PEI blend exhibited an upper critical solution temperature (UCST) behavior, whereas partially cured epoxy/PEI blend and BPACY/PEI blend showed bimodal UCST curves with two critical compositions, ft is attributed to the fact that, at lower conversion, thermoset resin has a bimodal distribution of molecular weight in which unreacted thermoset monomer and partially reacted thermoset dimer or trimer exist simultaneously. The rubber/epoxy systems that shows bimodal UCST behavior have been reported in previous papers [40,46]. Figure 3.7 shows the cloud point curve of epoxy/PEI system. With the increase in conversion (molecular weight) of epoxy resin, the bimodal UCST curve shifts to higher temperature region. 

Polyurea Polyurethane Porosity Post cure glycols, glycerol, and polyesters. A polymer containing the urea group -NH-CO-NH-. A polymer containing the urethane group -NH-CO-O-. The presence of numerous small cavities. Heat treatment to which a cured or partially cured thermosetting plastic or rubber composition is subjected to enhance the level of one or more properties. 

In-mold decoration can be done with either injection molding of thermoplastics or compression molding of thermosets. Thermosetting plastics are decorated with a two-stage process. For melamine products, for example, the mold is loaded with the molding powder in the usual manner and closed. It is opened after a partial cure, and the decorative "foil or overlay is placed in position. 

First, in terms of their physical form, adhesives may be either pastes or preforms (also known as films or tapes). Pastes are semisolid materials, easily dispensed through a needle or applied by screen or stencil printing. Film adhesives are solid sheets of thermoplastic or partially cured (B-staged) thermosetting polymers that can be cut to size and generally used to attach large-area components, substrates, and lids. 

Post-curing n. Completing the cure of a thermosetting casting or molding after removal from the mold in which a partial cure has been accomphshed. Post-curing usually... 

Prepreg molding n. A type of matched-metal-die molding in which the fibrous mat is pre-impregnated with a partially cured, thermosetting resin. 

Later stages of reaction are termed B-stage (partially cured or advanced to a relatively dry state but still flowable under heat and pressure conditions) and C-stage (fully cured to a nonflowable thermoset plastic). 

A number of companies supply carbon filaments that have been impregnated with a thermoset resin. A common configuration consists of unidirectional thin tape, with the resin partially cured to a B-stage condition. The use of these prepregs permits better quality control of the resin and the resin content in the molded part. Unidirectional carbon filament prepreg composites offer very high strength and moduli and relatively low density. 

For thermosetting prepregs, the resin is partially cured to a B-stage condition and supplied to the fabricator, who lays up the finished shape using the required layers of prepreg. (See Fig. P.22.) Prepreg may also be in the form of cord, thread, or tape. The fabricator then completes the cure with heat and pressure. 

Since the equipment to measure the temperature-induced dimension variation employs an LVDT displacement sensor, the requirement of a solid sample is mandatory. The effects of post-cure reaction on the measurement, instead, need much more detail and discussion. For a partially cured thermosetting resin, a post-cure reaction is expected when the actual temperature rises above the corresponding glass-transition temperature, Tg. Above this temperature, the volume variation due to post-cure reactions is superimposed upon thermal expansion (18). For this reason, TMA is a technique for measuring the CTE of the partially cured sample that is suitable only within the glassy region (T < Tg), while for a fiilly cured sample useful information can also be obtained for the CTE in the rubbery... 

Curing. The polymer bumps are then either fully cured or partially cured to the so-called B-stage for thermosetting polymer bumps. For thermoplastic polymer bumps, after stencil printing the solvent is removed to form solid bumps. Bump heights are typically 50-75 pm and process can accommodate pitches down to 5 mil. Bump densities of up to 80,000 bumps/wafer have been formed with excellent coplanarity. 

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