C-stage polymer

Baekeland found that a relatively stable resole prepolymer could be obtained by the controlled condensation of phenol and formaldehyde under alkaline conditions. These linear polymers of phenol-formaldehyde (PF) may be converted to infusible cross-linked polymers called resites by heating or by the addition of mineral acids. As shown in structure 4.80, the initial products obtained when formaldehyde is condensed with phenol are hydroxybenzyl alcohols. The linear resole polymer is called an A-stage resin, and the cross-linked resite is called a C-stage resin. 

As shown in a previous section, fluorinated nadimides exhibit the best thermo-oxidative behavior. NR 150 linear polymers are prepared by reaction of HFDE and a mixture of para- and raefa-phenylenediamine. A semi-IPN was prepared by addition of a 150 °C staged PMR-15 to a solution of the NR 150 precursor. The solution was used for the composite manufacture. After curing at 250 °C, the DSC diagram showed two peaks in agreement with a non-miscible system. After curing, the Glc of the blend is higher than that of pure PMR-15 (Table 8) [119]. 

C stage the polymer is highly cross-linked and does not soften on heating. 

Figure 1.41. Projected equatorial structure (perpendicular to the c-axis) for (a) nominal p4mm symmetry of stage-1 alkali-metal-doped polymers (b) stage-1 alkali-metal-doped polyacetylene (c) stage-1 Cs-doped PPV (Reproduced from ref 104 with kind permission. Copyright (1992) American Physical Society.)...

FIGURE 2.14 Three stages of co-injection (sandwich) molding, (a) Short shot of skin polymer melt (shown in black) is injected into the mold (b) injection of core polymer melt until cavity is nearly filled and (c) skin polymer melt is injected again, pushing the core polymer away from the sprue. 

Figure 16.7. Stages of gelation and fusion processes, a. mixture of PVC and plasticizer - plastisol b. particles absorbed plasticizer, have been swollen, and viscosity has been increased c. partial gelation accompanied with further viscosity increase, swelling and dissolving - borders of individual particles are still visible d. fused state. [Adapted, by permission, from Marcilla A Garcia J C, Eur. Polym. J., 33, No.3, March 1997, p.357-63.]...

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