Interfacial layer adhesion parameter

Figure 12.7 Dependence of the strength, (c ), of an interfacial layer on adhesion parameter A for PHE-Gr-I (1, 3) and PHE-Gr-II (2, 3). 1, 2 calculated from Equation 12.13, 3 from Leidner-Woodham equation at K= 2 [22].

Figure 12.8 Dependence of the adhesion parameter (A) on the thickness of the interfacial layer (IJ ), for 1 PHE-Gr-I and 2 PHE-Gr-II.

Figure 12.8 gives the dependence of the parameter A on the value of the thickness of an interfacial layer for composites of PHE-Gr. It is seen that increasing A (diminishing adhesion) with increasing the thickness of an interphase layer Ij is observed. 

Let us consider the main aspects of reinforcing of polymer/organoclay nanocomposites. As for all multiphase systems, the level of interfacial adhesion between the polymer matrix and the nanofiller is a crucial factor in the degree of reinforcement [2, 3]. In paper [4] it has been shown that good adhesion results in reinforcement of composites, and poor adhesion in the absence of reinforcing and the absence of interfacial adhesion weakens the polymer composite, i.e., the elasticity modulus for the composite is lower than the corresponding parameter for a matrix polymer. In the general case such behaviour is connected with stress transfer conditions in the interfacial boundary. For allowance of this factor an additional aspect appears for nanocomposites interfacial layer formation in the polymer-nanofiller boundary. 

This quick overview stresses the importance of a detailed understanding, from a fundamental point of view, of the conditions under which a stable interface forms, the parameters which control the adhesion and more generally the atomic and electronic structure in the interfacial layers. 

Although lap-shear evaluations are more familiar, they do not necessarily evalnate the strength of adherent/adhesive interfaces. Cohesive failnre of the weaker component of an assembly can be a complicating factor, tearing of the PU layer being a possibility in certain of the present measurements. In principle, the detachment of the adhesive in the blister test is a pure interfacial event and one that can be quantified provided parameters... 

Kulkarni et al. [83] studied the failure processes occurring at the micro-scale in heterogeneous adhesives using a multi-scale cohesive scheme. They also considered failure effect on the macroscopic cohesive response. Investigating the representative volume element (RVE) size has demonstrated that for the macroscopic response to represent the loading histories, the microscopic domain width needs to be 2 or 3 times the layer thickness. Additionally, they analyzed the effect of particle size, volume fraction and particle-matrix interfacial parameters on the failure response as well as effective... 

Interlayer adhesion between a polycarbonate (PC) layer and a PC-ABS blend layer, in 3-layer films made by melt coextrusion in a multi-manifold die, was analyzed using nonlinear viscoelastic (NLVE) die-flow simulations with POLYFLOW. These simulations showed significant extensional stresses in the interface vicinity where the two melt layers come into contact for the first time. A Viscosity Normalized Nonlinearity Ratio parameter was defined to correlate the simulated interfacial melt stresses and the observed adhesion behavior. Larger deviation of this parameter from a value of 1.0 (large disparities in melt extensional configuration across the interface) corresponded to poorer observed peel strength. 

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