The effect of interface characteristics on the morphology, rheology and thermal behavior of three‐component polymer alloys

Abstract

Immiscible polymer blends are interesting multiphase host systems for fillers. Such systems exhibit, within a certain composition limits, either a separate dispersion of the two minor phases or a dispersion of encapsulated filler particles within the minor polymer phase. Both thermodynamic (e.g. interfacial tension) and kinetic (e.g. relative viscosity) considerations determine the morphology developed during the blending process.The effect of interfacial characteristics on the structure‐property relationships of ternary polymer alloys and blends comprising polypropylene (PP), ethylene‐vinyl alcohol copolymer (EVOH) and glass beads (GB), or fibers (GF), was investigated. The system studied was based on a binary PP/EVOH immiscible blend, representing a blend of a semi‐crystalline apolar polymer with a semicrystalline highly polar copolymer. Modification of the interfacial properties was obtained through using silane coupling agents for the EVOH/glass interface and compatibilization using a maleic anhydride grafted PP (MA‐g‐PP) for the PP/EVOH interface. The compatibilizer was added in a procedure aimed to preserves the encapsulated EVOH/glass structure. Blends were prepared by melt extrusion compounding and specimens by injection molding. The morphology was characterized using scanning electron microscopy (SEM) and high resolution SEM (HRSEM), the shear viscosity by capillary rheometry and the thermal behavior using differential scanning calorimetry (DSC).The system studied consisted of filler particles encapsulated by EVOH, with some of the minor EVOH component separately dispersed within the PP matrix. Modification of the interfaces resulted in unique morphologies. The aminosilane glass surface treatment enhanced the encapsulation in the ternary [PP/EVOH]GB blends, resulting in an encapsulated morphology with no separtely dispersed EVOH particles. The addition of a MA‐g‐PP compatibilizer preserves the encapsulated morphology in the ternary blends with some finely dispersed EVOH particles and enhanced PP/EVOH interphase interactions.The viscosity of the binary and ternary blends was closely related to the blend's morphology and the level of shear rate. The treated glass surfaces showed increased viscosity compared to the cleaned glass surfaces in both GB and GF containing ternary blends.Both EVOH and glass serve as nucleating agents for the PP matrix, affecting its crystallization process but not its crystalline structure. The aminosilane glass surface treatment completely inhibited the EVOH crystallization process in the ternary blend.In summary, the structure of the multicomponent blends studied has a significant effect on their behavior as depicted by the rheological and thermal behavior. The structure‐performance relationships in the three‐component blends can be controlled and varied.

Mechanical and fracture properties of ternary PE/PA6/GF composites

“…Applying again the 'Rule of mixtures' to this system one can estimate 2 that the thickness of the PA6 layer surrounding the fibers is 3 lm. Similar values (3-10 lm) for the thickness of the encapsulating layer are reported also by Fisher et al [25] for (polypropylene)/(ethylene vinyl alcohol copolymer)/(glass beads) ternary composites with similar available total surface of the glass filler and similar preparation procedure. For the second approach, the shear lag model (e.g.…”

Mixing, rheology, and stability of highly filled thermal pastes

“…Similarly, only a few studies [15][16][17][18][19][20][21] exist on the rheology of thermal pastes, although their flow behavior is critical in attaining the narrow gap thickness required to reduce the thermal resistance between a computer chip and a cooled surface, or ''hat.'' Most reported studies [15][16][17][18][19][20][21] have been carried out on highly filled systems of a very different nature, such as phase-change materials [15], thermal gels [16], and other polymer-based systems [17][18][19][20][21].…”

“…Most reported studies [15][16][17][18][19][20][21] have been carried out on highly filled systems of a very different nature, such as phase-change materials [15], thermal gels [16], and other polymer-based systems [17][18][19][20][21]. In this paper, we discuss what is relevant to understanding the rheology of thermal pastes.…”

Effects of calcium carbonate and compounding sequence on the phase morphology and properties of maleic anhydride‐grafted polypropylene compatibilized polyamide 6/polypropylene blend

“…Besides, PP phase which was recovered by dissolving PA6 phase using HFIP was also characterized by FESEM. [24][25][26][27] The skin layer is quite a thin layer which is formed when molten material enters mould, undergoes stretching to some extent and solidifies quickly. It has been reported that during the process of injection molding, a hierarchical structure of morphology called skin-core structure [including skin, subskin (or shear zone), and core] is often formed.…”