Wettability of Glass Fibers in Reactive Thermoplastic/Polyester Blends: Comparison between Compatible and Incompatible Thermoplastics

The evolution of morphology of reactive thermoplastic/unsaturated polyester blends at the surface of glass fibers is investigated during curing. The study focuses on two different types of thermoplastics, incompatible and compatible respectively with the polyester resin. Poly(dimethylsiloxane) and poly(methyl methacrylate) are chosen as incompatible thermoplastics, and poly(vinyl acetate) as a compatible thermoplastic. In the presence of incompatible thermoplastics, the blends form an emulsion during the entire course of curing. In that case, a correlation exists between the surface tensions of the components of the blend measured before curing and the final morphology at the surface of the fibers. For a compatible thermoplastic, on the other hand, a reactioninduced phase separation occurs during curing. In that case, the morphology at the surface of the fiber after phase separation cannot be fully determined by the surface tensions of the components.

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Xavier Bulliard, Jan-Anders Månson, Véronique Michaud
2005
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https://infoscience.epfl.ch/record/87917?ln=fr

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Phase separation at the fiber-matrix interface in composites based on a thermoplastic/polyester blend

Xavier Bulliard, Jan-Anders Månson, Véronique Michaud

A study of the microstructure developing at the surface of glass fibers in a poly(vinyl acetate) (PVAc)/polyester blend is presented. Three different experimental methods are used: a technique based on the Wilhelmy method to measure the wettability of the fibers before curing, and both optical microscopy and atomic force microscopy in the pulsed-force mode to characterize potential phases splitting at the fibermatrix interface after curing. It was found that, depending on the curing conditions and the concentration in PVAc, the surface treatment of the fiber could have a significant influence on the microstructure. For a concentration in PVAc lower than 5 wt% and a curing temperature of 80°C, extreme cases, such as the development of layers of one of the phases at the surface or the formation of lenses of one phase, were observed. In other cases, in particular for elevated temperatures and higher concentrations in PVAc, the fibers did not exert a significant influence on the morphology. It was also found that in such a reactive system, surface tension considerations alone are insufficient to explain the configuration of the phases at the surface of the fibers.

2005

Chargement

A life cycle analysis of novel lightweight composite processes: Reducing the environmental footprint of automotive structures

Baris Çaglar, Colin Gomez, Véronique Michaud, Christian Rytka, Vincent Werlen

In this study, three novel thermoplastic impregnation processes were analyzed towards automotive applications. The first process is thermoplastic compression resin transfer molding in which a glass fiber mat is impregnated in through thickness by a thermoplastic polymer. The second process is a melt-thermoplastic Resin Transfer Molding (RTM) process in which the glass fibers are impregnated in plane with the help of a spacer. The third process, stamp forming of hybrid bicomponent fibers, coats the fibers individually during the glass fiber production. The coated fibers are used to produce a fabric, which is then further processed by stamp forming. These three processes were compared in a life cycle analysis (LCA) against conventional resin compression resin transfer molding with either glass or carbon fibers and metal processes with either steel or aluminum that can be new, partly or fully recycled using the case study of the production, life and disposal of a car bonnet. The presented LCA includes the main phases of the process: extraction and preparation of the raw materials, production and preparation of the mold, process, and energy losses. To include the life of the analyzed bonnet, the amount of diesel that is used to drive the weight of the bonnet for 300 ' 000 km is calculated. In this LCA, the disposal of the bonnet is integrated by analyzing the used energy for the recycling and the incineration. The results show the potential of the developed thermoplastic impregnation processes producing automobile parts, as the used energy producing a thermoplastic bonnet is in the same range as the steel production.

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Low-Profile mechanisms in a PVAc/polyester blend

Xavier Bulliard, Jan-Anders Månson, Véronique Michaud

The different steps associated with the curing of a PVAc/polyester blend are identified and correlated to the mechanism of shrinkage control in the presence of a low-profile additive (LPA). Poly(vinyl acetate) (PVAc) is used as a LPA and is shown to induce a phase separation upon curing that leads to an interconnected globule morphology. This morphology strongly modifies the rheokinetics of the blend compared to that of the neat polyester resin. In particular, the presence of PVAc delays the cure kinetics and the gel time. A comparison between these delays, called shift times, demonstrates an increase in the gel conversion of polyester in the presence of PVAc. This, coupled to the thermal expansion of PVAc at the early stages of curing, contributes to the low-profile effect. Microvoids in the LPA-rich phase, which are believed to play a key role in the mechanism of shrinkage control, are efficient at the later stages of curing and during cooling and complete the low-profile effect. However, it is also shown that the formation of microvoids may indirectly induce macroscopic voids that could be at the origin of pinholes at the surface of the parts molded with this material.

2006

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Thermoplastique

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Fiber

Fiber or fibre (British English; from fibra) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other ma

Fibre de verre

La fibre de verre est un filament de verre. Par extension, les plastiques à renfort de verre sont aussi appelés fibre de verre. Les fibres de verre, constituent avec les verres creux, les verres pl