Epoxy polymers structure

These examples barely touch the wide variety of epoxy polymer structures and curing reactions. They illustrate the point that the latent functionality of the prepolymers and the chemical and mechanical properties of the linal polymeric structures will vary with the choice of ingredients and reaction conditions. 

The introduction of a phenylene group into an epoxy polymer structure raises the sound speed. These polymers and other phenylene-containing polymers, such as polycarbonate, polysulfone, and polylether sulfone), all have relatively high sound speeds (65). The aromatic ring imparts a conformational rigidity to the backbone structure of these poljuners, which is responsible for the high sound speed. 

The authors of Ref [9] conducted cross-linked polymers microhardness description within the frameworks of the fractal (structural) models and the indicated parameter intercommunication with structure and mechanical characteristics clarification. The epoxy polymers structure description is given within the frameworks of the cluster model of polymers amorphous state structure [10], which allows to consider polymer as natural nanocomposites, in which nanoclusters play nanofiller role (this question will be considered in detail in chapter fifteen). 

It can be assumed that epoxy polymers structure loosely packed matrix sustains the main load in indentor pressing process as the least stiff its component. Its dimension f can be calculated according to the mixtures rule [9] ... 

Pakter, M. K., Beloshenko, V. A., Beresnev, B. I., Zaika, T. R., Abdrakhmanova, L. A., Berai, N. I. (1990). Influence of Hydrostatic Processing on Densely Cross-Linked Epoxy Polymers Structural Organization Formation. Vysokomolek. Soed. F, 32(N10), 2039-2046. 

M.K. Pakter, Y.M. Paramonov and E.S. Belaya in Epoxy Polymers Structure, NIITEKhIM, Moscow, Russia, 1984, p.46. 

Let us consider further the application of irreversible aggregation models for the description of epoxy polymer structure. This was partly carried out above (for... 

Unsaturated groups are very interesting for application development because this specific functionality opens up a broad range of possibilities for further (chemical) modification of the polymer structure, and therefore its physical and material properties. The direct microbial incorporation of other functional substituents to the polymer side chains, e.g. epoxy-, hydroxy-, aromatic-, and halogen functional groups, influences the physical and material properties of poly(HAMCL) even further [28,33,35,39-41]. This features many possibilities to produce tailor-made polymers, depending on the essential material properties that are needed for the development of a specific application. 

Epoxy resins find a large number of uses because of their remarkable chemical resistance and good adhesion. Epoxy resins are excellent structural adhesives. When properly cured, epoxy resins can yield very tough materials. They are used in industrial floorings, foams, potting materials for electrical insulations, etc. One of the principal constituents in many of the Fibre-reinforced plastics (FRP) is an epoxy polymer. 

The measured G(x) value of representative epoxy polymers is approximately 10, but this value depends strongly on the structure of the polymer, its glass transition temperature and other characteristics. Since the crosslinking reaction that characterizes the COP resist functionality is a chain reaction, in theory, a single, electron-initiated event could result in the insolublization of an entire film of the resist material. Fortunately, because of the existence of chain terminating reactions, this does not occur and high resolution imaging of the resist material can be accomplished. 

BMI polymers have glass transition temperatures in excess of 260°C and continuous-use temperatures of 200-230°C. BMI polymers lend themselves to processing by the same techniques used for epoxy polymers. They are finding applications in high-performance structural composites and adhesives (e.g., for aircraft, aerospace, and defense applications) used at tem-peratrues beyond the 150-180°C range for the epoxies. Bisnadimide (BNI) polymers are similar materials based on bisnadimides instead of bismaleimides. 

Fig. 12. C- 13 spectrum of the piperidine (PIP) cured DGEBA epoxy polymer at room temperature. The assignments have been discussed and the structure indicates a possible polymerization mechanism 2 ...

The structure of the epoxy polymers formed in the curing process has been thoroughly investigated using phenylglycidyl ether polymerization as an example. 

Morgan, R. J., Mones, E. T. The Cure Reactions, Network Structure and Mechanical Response of Diami nodiphenyl Sulfone Cured Tetraglycidyl 4,4 Diaminodiphenyl Methane Epoxies, Polymer (submitted)... 

Thermosetting epoxy polymers are widely employed in structural engineering applications and thus a knowledge of the mechanics and mechanisms of the fracture of such materials is of vital importance. The present Chapter discusses the fracture of epoxy polymers, concentrating on the use of a continuum fracture mechanics approach for elucidating the micromechanisms of crack growth and identifying pertinent failure criteria. 

The theory has been examined by measuring the ratio K,c/Klcs as a function of j/g, as shown in Fig. 17. The theoretical lines have been fitted to the experimental points by choosing suitable values of the critical distance, c, which is the only fitting parameter. The agreement between theory and experiment has been found to be equally good for many different epoxy polymers cured with many different hardeners, both unmodified 44- 45,51), rubber-modified 45) and containing glass particles 22) and even, under certain circumstances, for structural adhesive joints S3). Values of critical stress, ct,c, and distance, c, for various epoxy materials, obtained from bulk and... 

Vinyl ester resins arc manufactured through an addition reaction of an epoxy resin with an acrylic monomer, such as acrylic acid, methaciylic add. or the half-ester product of an hydroxyalkyl acrylate and anhydride. In contrast, the polyester resins are condensation products of dibasic acids and palyhydric alcohols. The relatively low-molecular-weight precise polymer structure of the vinyl ester resins is in contrast to the high-molecular-weight random structure of the polyesters. 

The synthesis of polymers containing diaza-crown ether groups in the main chain, i.e., poly(diaza-crown ether)s, has been recently achieved by incorporating these groups into macromolecular structures of conventional type, such as epoxy polymers 48,49,50) p0iyethers, and polyamides51>. In the former case, water soluble polymers could be obtained. 

Hydrogen bonds are one of the most representative structural features of epoxy polymers. Each step of the cure reaction involving epoxy ring opening forms one OH group, whose concentration in a cured polymer is high. 

Other interesting examples of the behaviour of the considered samples are given in Fig. 32. Samples with high Tg which are chemically less defective have lower E25 values. These anomalies in the mechanical properties of epoxy polymers prepared at low Tcure are very difficult to understand in terms of conventional concepts of the relationship between the structure of polymer glasses with their mechanical properties. 

H. S. Chu, Processing-Structure-Property Relations for High Performance Amine-Cured Epoxy Polymers, M. S. Thesis, Department of Chemical Engineering, University of Washington, Seattle, Washington, (1980). 

---