Rheological, mechanical, and adhesive properties of thermoplastic‐LCP blends filled by glass fibers

Abstract

Rheological, mechanical, and adhesive properties have been studied of two‐phase polymer blends containing a liquid crystal copolyester of poly(ethylelene terephthalate) and p‐hydroxybenzoic acid plus isotactic polypropylene (PP) with varying compositions and concentrations of glass fibers. Perfect fibrillation of the disperse LC‐phase into the PP‐matrix in capillary flow was observed at LCP concentrations >20 wt% and temperatures >488 K. This effect leads to a decrease of blend viscosity and a reinforcing of the extrudate's mechanical characteristics. At the same time, more essential reinforcement is achieved by the simultaneous addition of the reinforcing agents both of the LCP and glass fibers. Processing of PP is not impaired. It was found that the adhesive strength increases substantially when the amount of LCP in the blend exceeds a definite level, corresponding to a phase inversion. The results are explained by the formation near the interface of two adhesion layers: the first is composed of pure LCP having a higher surface tension, whereas the second layer represents the blend of various compositions. At small amounts of LCP, the adhesion failure proceeds in the interphase between the LCP and the blend. After the phase inversion, where adhesion strongly increases, the failure of adhesion joints proceeds near the interface between LCP and the glass.

Effect of a filler on the rheological and mechanical properties of the liquid-crystalline polyester-poly(methyl methacrylate) blends

“…From what has been said in preceding sections it may be suggested that fibrillization of isotropic PMMA melt due to LCP presence exerts the reinforcing effect. In this relation this system differs from the polypropylene-LCP blends, 11 probably due to stronger interactions between PMMA and LCP and higher adhesion strength at the interface between components. Really, the strength of adhesion bonds between polypropylene and LCP is 1.25 MPa, 11 whereas between PMMA and LCP 3.1 MPa (unpublished data).…”

“…In this relation this system differs from the polypropylene-LCP blends, 11 probably due to stronger interactions between PMMA and LCP and higher adhesion strength at the interface between components. Really, the strength of adhesion bonds between polypropylene and LCP is 1.25 MPa, 11 whereas between PMMA and LCP 3.1 MPa (unpublished data). Figure 11 gives the dependencies of the mechanical characteristics of solid extrudates on the whisker concentration for pure components and PMMA /LCP blend 7/3.…”

“…Similar results have been obtained for the ternary mixture polypropylene-LCP-glass fiber. 11 Consider now the rheological behavior by capillary flow for filled blends. Figure 4 shows the flow curves for filled LCP (A), PMMA (B), and 7/3 PMMA/LCP blend (C).…”

Wear and mechanical properties of reactive thermotropic liquid crystalline polymer/unsaturated polyester/glass fiber hybrid composites

“…This is because of the low viscosity of TLCP attribute to the structure consist of linear semirigid rod-like molecules that can improve the processability of composites system and extend into fibrous structures and orient in the flow direction. 5,6 Many studies related to hybrid composites reinforced with fiber and TLCP, the matrix polymers such as polypropylene (PP), [7][8][9] high density polyethylene, 10 Polycarbonate (PC), 11 etc. had been done.…”

Micro-Rheological Study on Fully Exfoliated Organoclay Modified Thermotropic Liquid Crystalline Polymer and Its Viscosity Reduction Effect on High Molecular Mass Polyethylene

“…The addition of inorganic fillers not only enhanced the mechanical properties of the blends but also reduced the anisotropy of the resulting materials [5]. Rheological characterization revealed that TLCP could reduce the melt viscosity of glass-filled thermoplastics [6]. Much work has been published on TLCP systems containing different inorganic solid reinforcements, such as glass fibres [7], carbon black [8], whiskers [9] and silica [10].…”