Tetrafunctional resins

Shell Epikote 1031 is a tetrafunctional resin and with appropriate curing agents (e.g., DDS/BF3MEA or MNA/BDMA) produces composites with excellent thermal stability and has been used for filament winding rocket motor cases. 

Another very popular tetrafunctional resin, tetraglyddylmethylenedianiline (TGMDA) (e.g., Ciba s MY720), has found widespread use in many prepreg systems used with carbon fiber composites and is available in different grades of purity. 

A highly functional resin useful for prepreg formulation is Celanese SU8  

Cycloaliphatic epoxies are prepared by converting tetrahydrobenzaldehyde by a Tisotenko condensation to form as an olefin which is epoxidised with a peradd. 

The product, 3,4-cyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, marketed as Ciba CY179, has a very low viscosity and can be used as a diluent, since it is an excellent solvent for other resin families and also is a good solvent for the curing agent 4,4 -diaminodiphenyl-sulfone (DDS). The absence of an aromatic ring is noticeable. Unfortunately, the range of cycloaliphatic resins on the market has been almost terminated due to difficulties in their manufacture. 

---

More recently, trifunctional and tetrafunctional resins (Tactix 742, namely the triglycidyl ether of tn 5(hydroxyphenyl) methane, and Shell 1153, namely a diaryl-methylene-bridged DGEBA) have been trialled, but the alternative approach of curing glycidyl amine resins with aromatic amines has proven to be more widely employed to achieve high Tg. These resins were shown earlier in Scheme 1.4. 

When the crosslinking density is high, as in the case of tetrafunctional resins, toughness can he increased with the use of ductile glassy polymers capable of reacting with the epoxy resin in order to produce a strong interfacial adhesion between the two phases. 

This compound is soluble in most organic solvents and may be easily copolymerized with other vinyl monomers to introduce reactive side groups on the polymer chain (18). Such reactive polymer chains may then be used to modify other polymers including other amino resins. It may be desirable to produce the cross-links first. Thus, A/-methylolacrylamide can react with more acrylamide to produce methylenebisacrylamide, a tetrafunctional vinyl monomer. 

In the 1960s, CIBA Products Co. marketed and manufactured glycidylated o-cresol novolak resins, which had been developed by Koppers Co. as high temperature-resistant polymers. Dow offered glycidylated phenol novolak resins, SheU introduced polyglycidyl ethers of tetrafunctional phenols, and Union Carbide developed a triglycidyl p- am in oph en o1 resin. 

Fissure sealants are clear, low-viscosity, photocurable liquids, based on a mixture of tetrafunctional and difunctional methacrylates. Other dental photocurable materials are cements, adhesives and denture base resins.66-68... 

Silicone resins can be made from pure polyorganic siloxanes with a high percentage of tri- and tetrafunctional siloxy groups, which are crosslinked in the presence of a catalyst by heating at 250 °C for a long time. They can also be made from a mixture of polyorganic siloxanes with polyesters. 

Cross-linked resins of polyamidoamine structure can be prepared in the same way as the linear polymers by partly substituting a, m-diaminoalkanes for the same quantity of difunctional aminic monomers in the polymerization process. According to the general scheme of poly(amido-amine)synthesis, bis(primary amine)s, having four mobile hydrogens, act as tetrafunctional monomers 47). 

Glycidyl Ether of Tetraphenolethane. A large number of polyhydric phenols have been used to prepare diglycidyl ethers. The polyphenol, l l,2 2-(p-hydroxyphenol)ethane, is used to prepare a tetrafunctional epoxy resin, tetraglycidyl ether of tetraphenolethane. The functionality of commercial resins (e.g., EPON Resin 1031, Resolution Performance Products, LLC) is about 3.5. This forms a solid resin (melting point of 80°C) with a structure as shown in Fig. 2.6. Commercial products are solid resins and solutions. 

The resin cured with excess DICY (assuming DICY is tetrafunctional) is a single phase system while the resins cured with DICY with epoxy groups in excess are two-phase systems which exhibit two maxima in tan 8. Since the IR analysis shows that all NH and epoxy groups disappear, the main reaction is assumed to be the addition reaction of the epoxy groups to the NH groups. 

Fig. 9a and b. TBA spectra for a series of isothermal cures showing changes in (a) the relative rigidity and (b) the logarithmic decrement vs. time. Gelation and vitrification are evident in the 80, 125 and 150 °C scans, but only vitrification is observed in the 200 and 250 °C scans. The system studied was a trifunctional epoxy resin, XD7342 [triglycidyl ether of tris(hydroxyphenyl)-methane, Dow Chemical Co.], cured with a tetrafunctional aromatic amine, DDS (diamin iphenyl sulfone, Aldrich Chemical Co.)... 

DihydroquinazoHnes have been synthesized by aza-Wittig coupling to form the carbodiimide and subsequent addition of a secondary amine to induce an intramolecular Michael addition of 157 [202], Elements of diversity are therefore added upon treating the iminophosphoranes with isocyanates or thioisocyanates, and upon the subsequent reaction of the carbodiimide with an excess of a secondary amine. 1,4-DihydroquinazoHnes have been prepared using a tetrafunctional scaffold cyclized with aryl isothiocyanates on Rink resin [204],... 

Scheme 1.4. Structures of typical difimctional, trifunctional and tetrafunctional epoxy resins.

Such TTT diagrams have also been useful in describing the cure of polyimide systems, as shown in Palmese (1987), which shows the TTT diagram of a polyamicacid/polyimide system. The TTT diagram of a polycyanurate system is developed by Simon (1993) on the basis of FT-IR, DSC and torsional braid measurements. Kim et al (1993) developed a TTT diagram for a thermoset-thermoplastic blend, specifically a tetrafunctional epoxy-resin/poly(ether sulfone)/dicyandiamide thermoset-thermoplastic blend (Figure 2.9). 

A very recent study based on FTIR analysis of the isothermal co-reaction between tetrafunctional epoxy and cyanate ester resins at different stoichiometric ratios and temperatures substantiates some of these findings. Rheological char-... 

The properties of a tetrafunctional epoxy (Narmco 5208), cured according to a manufacturer s suggested procedure, are also included in Table I for comparison. Although the cured phthalonitrile resins are only marginally tougher than the epoxy and comparable in stiffness, they offer higher use temperature (or Tg). The exceptional case was the bisphenol-A6F linked resin, which is extemely brittle and has a very low glass transition temperature. 

---