Cross-link density coatings

Permeabilities of Model Coatings Effect of Cross-link Density and Polarity... 

Figure 7. Elastically effective cross-link density versus bake temperature for an acrylic-urethane coating as a function of polyol to isocyanate ratio.

The multifunctionality contributes higher reactivity and cross-link density. These factors are especially critical when formulating systems that require improved thermal performance over conventional epichlorohydrin—bisphenol A systems. The melt viscosity of these resins, which are solids at room temperature, decreases sharply with increasing temperature. This affords the formula tor an excellent tool for controlling flow of molding compounds, and facilitating the incorporation of ECN resins into other epoxies, eg, for powder coatings. 

At an optimum addition level of only 1.5 w t %, nano-size magnesium-aluminum LDHs have been shown to enhance char formation and fire-resisting properties in flame-retarding coatings, based on an intumescent formulation of ammonium polyphosphate, pentaerythritol, and melamine.89 The coating material comprised a mixture of acrylate resin, melamine formaldehyde resin, and silicone resin with titanium dioxide and solvent. It was reported that the nano-LDH could catalyze the esterification reaction between ammonium polyphosphate and pentaerythritol greatly increasing carbon content and char cross-link density. 

In this paper the recently developed techniques to characterize the mar resistance of coating systems were presented. The techniques base on methods that create a single scratch onto a surface. Characteristic values like the critical load as a measure for the transition from plastic behaviour to brittle fracture can be determined and used to rank different clearcoat systems and to compare these results with other physical properties. In the field of mar resistance the cross-linking density of the... 

It has been suggested that the decrease in the S parameter on exposure time is a result of the decrease in the defect (free volume) size or concentration due to irradiation [30]. This is a result of a net increase in the cross-linking density of the samples as a result of photodegradation. It has been demonstrated that there is a direct relationship between the decrease in the S parameter (loss of free volume) and an increase in the cross-linking density due to degradation for polyurethane coatings [32], We can postulate... 

As mentioned earlier, UV-curable resin formulations are very attractive for fiber coating because of the rapid cross-linking rates that are achievable. Most commonly, epoxy- or urethane-acrylate resins are employed (18-22), and viscosity and cross-link density are controlled through the addition of reactive diluents. With these systems work has focused on producing low modulus, low T properties (20-22) through the incorporation of appropriate chemical constituents to enhance higher chain flexibility, for example, ether linkages. 

The results of an abrasion test (ASTM D4060-01) carried out for 500 test cycles are presented in Table 11.4. Wear index decreased monotonically with the increase in the HDDA content in the coating formulation, which showed that the abrasion resistance property of BDGDA improved in the presence of HDDA. Improvement in abrasion resistance of the coating with increase in HDDA content is attributed to the increase in the cross-link density on addition of HDDA. 

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