Fibers treated with polymerization compounds and fiber reinforced composites made therefrom

Abstract

Methods of making fiber reinforced composite articles are described. The methods may include treating fibers with a sizing composition that includes a polymerization compound, and introducing the treated fibers to a pre-polymerized composition. The combination of the treated fibers and pre-polymerized composition may then undergo a temperature adjustment to a polymerization temperature at which the pre-polymerized composition polymerizes into a plastic around the fibers to form the fiber-reinforced composite article. Techniques for introducing the treated fibers to the pre-polymerized composition may include pultrusion, filament winding, reactive injection molding (RIM), structural reactive injection molding (SRIM), resin transfer molding (RTM), vacuum-assisted resin transfer molding (VARTM), long fiber injection (LFI), sheet molding compound (SMC) molding, bulk molding compound (BMC) molding, a spray-up application, and / or a hand lay-up application, among other techniques.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS[0001]This application is a continuation-in-part of prior U.S. application Ser. No. 12 / 881,736 filed Sep. 14, 2010, which is a continuation-in-part of prior U.S. application Ser. No. 12 / 724,024 filed Mar. 15, 2010, which is a continuation-in-part of U.S. application Ser. No. 12 / 008,041 filed Jan. 8, 2008. The entire contents of the above-identified applications are herein incorporated by reference for all purposes.BACKGROUND OF THE INVENTION[0002]Fiber-reinforced composites are used in a variety of parts and equipment, including automotive parts, boat parts, building elements, and aircraft parts, among other types of articles. One well established method of making these articles is to place the bare fibers in a mold and then flow in the liquid precursors of a thermoset polymer. Once the precursors have infused through the fibers and filled the mold, a curing stage ensues where the precursor polymerize into a thermoset polymer matrix surroundin...

AI Technical Summary

Problems solved by technology

Still, there are significant disadvantages associated with making fiber-reinforced thermoset articles, as well as deficiencies with the composites in many applications.

One considerable disadvantage with making these articles is the health and safety problems posed by working with uncured thermoset resins.

Outgasing VOCs are particularly problematic during curing processes when exothermic polymerization reactions raise the temperature of the composite and increase rate which these compounds evaporate into the surrounding atmosphere.

In order to prevent VOC concentrations from exceeding safe limits, expensive ventilation and air treatment equipment is required.

This equipment is particularly costly and difficult to maintain for the manufacture of larger composite articles, such as boat hulls and wind-turbine blades.

Another significant problem with making fiber-reinforced thermoset composites is the large amounts of unrecyclable waste they generate.

Glass reinforced polyester and epoxy wastes do not easily decompose, making them expensive to landfill.

When they are contaminated with toxic precursors, such as epoxy prepregs, they present an even greater environmental challenge.

The inability to recycle most fiber-reinforced thermosets also presents a disposal challenge when the articles made from these composites reach the end of their useful lives.

The size of this challenge only increases with the size of the articles that must be discarded.

Larger-sized articles present additional challenges for thermoset composites.

Thermosets in general cannot be welded or melted, which makes it very difficult, if not impossible, to modify or repair thermoset parts once they have been cured.

The high degree of crystallinity that is characteristic of many thermoset polymers also makes the composites prone to fractures that cannot easily be repaired.

When fractures and other defects form in larger thermoset articles, often the only option is to replace the article at significant cost.

Thermoplastics are generally also recyclable, which significantly decreases environmental impact and waste disposal costs both during manufacturing as well as at the end of an article's lifecycle.

Unfortunately, thermoplastics also have production challenges including significantly higher flow viscosities than uncured thermoset resins.

The higher flow viscosities makes it difficult for thermoplastic resins to infiltrate a fiber mat and produce a homogeneous polymer matrix composite that is free of voids and seams.

Oftentimes, it is necessary to introduce the thermoplastic resin under high temperature or high vacuum, which increases the costs and complexity of manufacturing processes.

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