Abstract: A new class of high modulus polypropylene multifilament fiber and/or yarn is provided. Such a multifilament fiber and/or yarn exhibits an exceptional combination of high strength and toughness with low weight and density. The inventive fibers thus permit replacement of expensive polymeric fibers within certain applications with lower cost alternatives, or replacement of high density components with such low density fibers, without sacrificing strength or durability. Such multifilament fibers are produced through melt-spinning processes and exhibit highly unique microstructures therein, including significant void volumes, interspersed and crossed voids, and nanofilament bridges within such voids. Such microstructural characteristics appear to impart the exceptional properties noted above.

Abstract: A new class of high modulus polypropylene multifilament fiber and/or yarn is provided. Such a multifilament fiber and/or yarn exhibits an exceptional combination of high strength and toughness with low weight and density. The inventive fibers thus permit replacement of expensive polymeric fibers within certain applications with lower cost alternatives, or replacement of high density components with such low density fibers, without sacrificing strength or durability. Such multifilament fibers are produced through melt-spinning processes and exhibit highly unique microstructures therein, including significant void volumes, interspersed and crossed voids, and nanofilament bridges within such voids. Such microstructural characteristics appear to impart the exceptional properties noted above.

Abstract: Disclosed are composites that can exhibit low transmission energy loss and can also be temperature resistant. The composites include reinforcement fibers held in a polymeric matrix. The reinforcement fibers can include an amorphous polymer component. The fibers can be woven or knit to form a fabric or can be included in a nonwoven fabric. The composites can include other fibers as well, such as fiberglass. The composites can be multi-layer structures and can include layers of other materials, for instance layers formed of polyaramids, fiberglass, or carbon fiber wovens or nonwovens. The composites can advantageously be utilized in low loss dielectric applications, such as in forming circuit board substrates.