Properties resins, glassy

The polymers of the 2-cyanoacryhc esters, more commonly known as the alkyl 2-cyaiioacrylates, are hard glassy resins that exhibit excellent adhesion to a wide variety of materials. The polymers are spontaneously formed when their Hquid precursors or monomers are placed between two closely fitting surfaces. The spontaneous polymerisation of these very reactive Hquids and the excellent adhesion properties of the cured resins combine to make these compounds a unique class of single-component, ambient-temperature-curing adhesives of great versatiUty. The materials that can be bonded mn the gamut from metals, plastics, most elastomers, fabrics, and woods to many ceramics. 

Mechanical Properties of Cured Epoxy Resins in the Glassy State.194... 

It is known that in the glassy state below the glass transition temperature the physical properties of epoxy resin as well as other amorphous polymers are generally little dependent on temperature and structure 1,28). Also, the modulus of elasticity (E) does only weakly depend on the crosslinking density. 

Cured epoxy resins are often used as structural materials and their performance is determined by their mechanical properties in the glassy state. However, as mentioned in Chapter 5, the mechanical properties of unfilled resins in the glassy state are almost equal and do not depend much on the chemical structure and degree of crosslinking. 

On reaction of oxypropylated EGG with molten MDI (stoichiometric ratio, r = 1.01) at 50 °C for 5 minutes followed by curing at 90 °C for 14 hours, a transparent, amber, glassy polyurethane resin was obtained. The T of the resin by DSC was 57 °C, and its mechanical properties (23 °C) were similar to poly(methyl methacrylate) with a Young s modulus of 2.78 GPa, tensile strength of 46.3 MPa, ultimate elongation of 2.6%, and Charpy impact energy of 1.5 kJ-m-2. 

Like HIPS, acrylonitrile-styrene-butadiene (ABS) polymers have polybutadiene rubber incorporated into styrene-acrylonitrile copolymer (SAN), giving a resin consisting of a two-phase system with inclusions of rubber in a continuous glassy matrix. Again, development of the best properties requires grafting between the glassy and rubbery phases. 

Knot et al. (51) converted soybean oil to several monomers for use in structural applications. They prepared rigid thermosetting resins by using free radical copolymerization of maleates with styrene. The maleates are obtained by glycerol trans-esterification of the soybean oil, followed by esterification with maleric anhydride. They also synthesized several TAG-based polymers and composites and compared their properties. It was found that the moduli and glass transition temperature (Tg) of the polymers varied and depended on the particular monomer and the resin composition. They proposed that the transition from glassy to rubbery behavior was extremely broad for these polymers as a result of the TAG molecules acting both as cross-linkers as well as plasticizers in the system. 

---