Brittle tough

The quantitative results of fracture energy, which are calculated from the total area under load-displacement curves, are presented in Fig. 50. It becomes obvious, that a brittle-tough transition exists at a volume fraction of around 10%. This brittle-tough transition is observed for solvent-modifled as well as semi-porous epoxies. A brittle behavior is observed in macroporous epoxies after complete solvent removal, thus giving low fracture energies similar to the neat epoxy for each porosity. 

It might be argued that the brittle tough transition and the embrittlement upon drying is related to variations in the extent of reaction and hence to Tg. However, no significant changes in Tg as a function of solvent concentration were found (Fig. 51). 

Solvent-modified thermosets display enhanced toughness due to the incorporation of a second phase material. A brittle-tough transition has been observed which cannot be attributed to changes in the interparticle distance. The chemically induced phase separation technique offers new routes and strategies to prepare such materials and enter new areas of applications. Hence, engineered porosity is demonstrated as a research concept developed into a toolbox for material scientists. 

Is copper ductile Malleable Brittle Tough Hard or soft ... 

Is zinc hard or soft Malleable Ductile Brittle Tough Does it melt easily ... 

Plasticizers are particularly used for polymers that are in a glassy state at room temperature. These rigid polymers become flexible by strong interactions between plasticizer molecules and chain units, which lower their brittle-tough transition or brittleness temperature (Tb) (the temperature at which a sample breaks when struck) and their Tg value, and extend the temperature range for their rubbery or viscoelastic state behavior (see Figure 1.19). 

Modified PPO brittle tough resins ties such as lubricity, con-... 

Margolina, A. and Wu, S. 1988. Percolation model for brittle-tough transition in nyfon/rubber... 

Boi greve, R. J. M., Caymans, R. J., Schuijer, J., and Inden Housz, J. F. 1987. Brittle-tough transition in nylon-rubber blends Effect of rubber concentration and particle size. 28 1489-1496. 

Fig. 11.25 Temperature of brittle-tough transition as a function of the weight-average particle size for blends of PA6 and 10 wt.% rubber, with different types of rubbers , EPDM -h, EPR X, LDPE A, Keltaflex ...

Wu [175-177] proposed that the MLT, i.e., surface-to-surface inter-particle distance is a fundamental parameter. For effective toughening, mean matrix ligament thickness (x) should be less than that of the critical value (xj where brittle-tough transition occurs. The x is independent of rubber volume fraction, particle size and characteristics of the matrix alone at a given test temperature and rate of deformation. For blends with dispersed spherical particles, the x can be related to the rubber particle size and rubber volume fraction < >) by the following equation [177] ... 

Fig, 1.6, Effect of tricresyl phosphate on the brittle-tough temperature Jb) of plasticized PVC (wi = weight fraction of the plasticizer) [27]. 

Unsaturated polyester resins can be formulated to be hard and brittle, tough and resilient, or soft and flexible. By the appropriate choice of intermediates, particularly to form the linear unsaturated resin, special properties can be built into the resin system. As pointed out earlier (Table 12.2), the starting materials used with MA in polyesterifications have different effects upon the extent of isomerization of maleate to fumarate, and this in turn has a strong influence upon the final properties of the cured materials, As shown in Table 12.2, the percentage of fumarate increases considerably as more sterically hindered glycols or aromatic acids are used in the formulations. ... 

PA6 EPDM-g-MA The brittle-tough transition goes to lower temperature with increased rubber content, decreased rubber particle size and decreased rubber phase modulus 39... 

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