Mixing region, interphase

In the present study, the effects of composition, molecular weight, and heat treatment on the relaxation behavior of styrene—butadiene-styrene (SBS) block polymers are investigated. There is evidence (e.g., 6,7,8) that these types of multicomponent multiphase systems exhibit unusual phenomena in their dynamic mechanical behavior and in other physical properties. These are apparently related to the presence of the so-called interphase mixing region between the elastomeric and glassy domains. Similar evidence has been obtained by gas diffusion and sorption studies on the copolymer samples used in this investigation (9). 

The concept sounds attractive, but there is a flaw in the explanation. Assuming an equilibrium situation between the two bulk phases and the interphase, complex formation at the interfacial region requires the same complexes are formed also in the bulk phases. Consequently, in order to produce a considerable amount of the mixed species MA, xBx in the liquid-liquid boundary layer some B must be dissolved in the aqueous, as weU as some A in the organic phase. Since by definition this condition is not met, the relative amount of M present at the interphase region as MAn xBx must be negligible. However, now the metal ion will be distributed between MA in the aqueous phase and MBp in the organic layer (n and p are the... 

Tsitsilianis [93] used DSC to study the phase behavior of (polybutylmethacr-ylate)n(polystyrene)n and (polybutylacrylate)n(polystyrene)n miktoarm stars with varying n. The Tg of the PS phase was found to be much lower than in the homopolymer and the width of the transition was increased. In some cases an intermediate Tg was observed due to the extended interphase region in these materials, as a result of mixing of the different arms in the vicinity of the star cores. 

A study of the phase behavior of (poly-f-butylmethacrylate)n - (polystyrene)n and (poly-t-butylacrylate)n - (polystyrene), miktoarm stars by differential scanning calorimetry has shown a remarkable decrease in the Tg of the polystyrene phase, in comparison with linear precursors, and an increase in the width of the glass transition [360]. An intermediate Tg was observed in some cases for microphase separated samples. The above phenomenon was attributed to an extended interphase region in these materials, due to partial mixing of the different chains around the cores of the stars. 

To account for the apparent restricted mobility of the PBD region attention must be paid to the interphase between pure PS domains and the pure PBD continuum. The presence of a significant interfacial region of mixed composition separating the PS domains from the PBD continuum has been demonstrated by analysis of dynamic viscoelastic behavior (25,26), TgS (27,28), and small angle x-ray scattering data (29,... 

The results show a significant correlation between the penetration behavior and the degree of condensation (molecular size, viscosity) of the resins. The higher the degree of condensation, the lower is the penetration possibility, expressed as Average penetration depth (AP). The portion of filled tracheids in the radial direction on both sides of the bondline ( Filled interphase region , FIR) however, did not depend statistically on the viscosity of the resin mix. 

Average size of the interphase region (IR) and the sum of fiUed lumens and rays (A) in fir as evaluated for the adhesive mixes based on the three resins UF1, UF It and UF 111... 

A similar increase in viscosity as for the resins themselves is seen for the adhesive mixes (UF I 545 mPa s UF II 745 mPa s UF HI 1644 mPa s), measured just after mixing. The viscosities of the different adhesive mixes were taken here as a measure of the DOC in order to show its influence on the Average penetration depth (AP) in radial direction and on the Filled interphase region (FIR). 

Table 2 summarizes the overall results for the Average penetration depth (AP) and the Filled interphase region (FIR) for penetration into beech for the three adhesive mixes based on the resins with different degrees of condensation. 

Figure 5 shows the Filled interphase region (HR) for beech as a function of molar masses (different degrees of condensation) of the UF adhesive mixes inves-... 

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