Crosslinking behavior

Also, because of their non-crosslinking behavior in many polymer analogous reactions and... 

EHA), vinyl acetate (VAc) and acrylic acid (AA), and with varying contents of 2-hydroxyefhyl methacrylate (2-HEMA) and an unsaturated benzophenone derivative (P-36). The UV-crosslinking behavior of the PSAs was monitored by FTIR-ATR and PSA performance was evaluated by probe tack, peel strength, and shear adhesion failure temperature (SAFT) after exposure to various UV doses. 

PA-MI/PA-F cross-linked polymers showed thermally reversible crosslinking behavior via DA and retro-DA reactions. Cross-linked PA-MI/PA-F films exhibited enhanced toughness and mechanical properties over PA-MI and PA-F precursors. Moreover, PA-MI/PA-F films also showed excellent thermal self-repairing behavior. 

TSA 06] Tsai C.-J., Chen Y., Luminescent poly(p-phenylenevinylene) with 4-methylcoumarin side groups synthesis, optical properties and photo-crosslinking behaviors , Reactive Functional Polymers, vol. 66, no. 11, pp. 1327-1335, 2006. 

Vitamin E is an effective free radical scavenger, and its ability to stabilize UHMWPE at extremely low concentrations also results in its tendency to reduce the efficiency of crosslinking during irradiation. The ability of vitamin E to reduce crosslinking efficiency has been noted by several previous authors [2, 7, 8]. Because the crosslinking behavior of UHMWPE is related to its wear resistance, the development of vitamin-E-blended materials involves a potential tradeoff in wear resistance versus oxidation stabihty, as illustrated schematically by Figure 16.2, for concentrations of up to 3000 ppm. 

In the rubbery plateau, a new impediment to movement must be overcome entanglements along the polymer chain. In discussing the effects of entanglements in Chap. 2, we compared them to crosslinks. Is it any surprise, then, that rubbery behavior similar to that shown by cross-linked elastomers characterizes this region ... 

The plateau compliance is characteristic of rubbery behavior where chain entanglements play the role of effective crosslinks. 

Between T j, and Tg, depending on the regularity of the polymer and on the experimental conditions, this domain may be anything from almost 100% crystalline to 100% amorphous. The amorphous fraction, whatever its abundance, behaves like a supercooled liquid in this region. The presence of a certain degree of crystallinity mimics the effect of crosslinking with respect to the mechanical behavior of a sample. 

In the last three chapters we have examined the mechanical properties of bulk polymers. Although the structure of individual molecules has not been our primary concern, we have sought to understand the influence of molecular properties on the mechanical behavior of polymeric materials. We have seen, for example, how the viscosity of a liquid polymer depends on the substituents along the chain backbone, how the elasticity depends on crosslinking, and how the crystallinity depends on the stereoregularity of the polymer. In the preceding chapters we took the existence of these polymers for granted and focused attention on their bulk behavior. In the next three chapters these priorities are reversed Our main concern is some of the reactions which produce polymers and the structures of the products formed. 

Fig. 22. Nomialized pull-off energy measured for polyethylene-polyethylene contact measured using the SFA. (a) P versus rate of crack propagation for PE-PE contact. Change in the rate of separation does not seem to affect the measured pull-off force, (b) Normalized pull-off energy, Pn as a function of contact time for PE-PE contact. At shorter contact times, P does not significantly depend on contact time. However, as the surfaces remain in contact for long times, the pull-off energy increases with time. In seinicrystalline PE, the crystalline domains act as physical crosslinks for the relatively mobile amorphous domains. These amorphous domains can interdiffuse across the interface and thereby increase the adhesion of the interface. This time dependence of the adhesion strength is different from viscoelastic behavior in the sense that it is independent of rate of crack propagation.

Depending on the formulations various grades of water resistance can be achieved according to EN 204 (D1-D4) [172], For the two-component PVAc adhesives crosslinking and hence a duroplastic behavior is effectuated by addition of hardening resins (e.g. on basis of formaldehyde), complex forming salts (based... 

This transitory behavior was observed to arise from all the weathering agents considered in this study except ozone. Instead, test coupons exposed to ozone exhibited an initial decline in the crosslink density of the silicone with the formation of surface cracks, which were difficult to distinguish with the naked eye. With continued exposure to ozone, however, the material would begin to crosslink. We proposed that ozone s greatest affinity... 

In another case where the twin-screw extruder was used, the rubber and plastic were melt mixed with all ingredients in a similar manner as described in blend compositions for static vulcanizations. The product was then dumped, cooled, and granulated. The premixed granules were then fed into a twin-screw extruder where a very narrow temperature profile was maintained with a relative high compression (2 1), and the screw speed was adjusted depending on the final torque and the flow behavior of the extruded stock. The stock was cured by shear force and temperature enforced by the twin-screw extruder. The dynamically crosslinked blend was taken out in the form of a strip or solid rod to determine the... 

Flow Behavior of Polymer Blends as Affected by Interchain Crosslinking... 

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