High buoyancy composite materials
Ballistic resistant composite materials having high positive buoyancy in water are provided. More particularly, provided are foam-free, buoyant composite materials fabricated using dry processing techniques. The materials comprise fibrous plies that are partially coated with a particulate binder that is thermopressed to transform a portion of the binder into raised, discontinuous patches bonded to fiber/tape surfaces, while another portion of the particulate binder remains on the fibers/tapes as unmelted particles. The presence of the unmelted binder particles maintains empty spaces within the composite materials which increases the positive buoyancy of the composites in water.
1 . A buoyant ballistic resistant article having positive buoyancy in water, said article comprising a buoyant ballistic resistant material having positive buoyancy in water, wherein said article incorporates one or more armor plates, said armor plates having neutral or negative buoyancy in water, said buoyant ballistic resistant material comprising at least one fibrous ply, each fibrous ply comprising a plurality of fibers and/or a plurality of tapes, wherein one or more of said fibers/tapes have surfaces that are partially covered by raised, discontinuous patches of a polymeric binder bonded to and extending from the fiber/tape surfaces, and wherein the material further comprises a plurality of polymer particles on and/or between said fibers/tapes, wherein at least some of said polymer particles are softened and/or melted;
wherein said buoyant ballistic resistant material has a volume that partially comprises empty space, and wherein said buoyant ballistic resistant article is foam-free and has said positive buoyancy in water without air bladder inserts or other buoyancy enhancing components.
2 . The buoyant ballistic resistant article of claim 1 wherein the patches have an aspect ratio of less than 10:1 and are formed on the fiber/tape surfaces by softening and/or melting a dry, solvent-free polymeric powder.
3 . The buoyant ballistic resistant article of claim 1 wherein said empty space comprises greater than 20% of said buoyant ballistic resistant material.
4 . The buoyant ballistic resistant article of claim 1 wherein said polymeric binder and said polymer particles comprise different polymers and wherein all of said polymer particles are softened and/or melted.
5 . The buoyant ballistic resistant article of claim 1 wherein said polymeric binder and said polymer particles comprise the same polymer and wherein all of said polymer particles are softened and/or melted.
6 . The buoyant ballistic resistant article of claim 1 wherein less than 50% of the surface area of each of said fibers/tapes is covered by said patches.
7 . The buoyant ballistic resistant article of claim 1 wherein each fibrous ply is non-woven and comprises a plurality of adjacent, parallel fibers/tapes.
8 . The buoyant ballistic resistant article of claim 1 wherein each fibrous ply has a fiber areal density of less than 80 g/m 2 and a total areal density of less than 100 g/m 2 and wherein all of said polymer particles are melted.
9 . The buoyant ballistic resistant article of claim 1 wherein the patches of polymeric binder and the plurality of polymer particles combined comprise about 6 wt. % or less by weight of the ballistic resistant material, wherein said fibers comprise ultra-high molecular weight polyethylene fibers, and wherein said polymeric binder and said polymer particles each comprise very low density polyethylene (VLDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), poly(methylene), metallocene-low density polyethylene (m-LDPE), metallocene-linear low density polyethylene (m-LLDPE), metallocene-medium density polyethylene (m-MDPE), or a cyclic olefin copolymer (COC).
10 . The buoyant ballistic resistant article of claim 1 wherein said armor plates have negative buoyancy in water.
11 . The buoyant ballistic resistant article of claim 1 wherein each fibrous ply of the ballistic resistant material has a fiber areal density of less than 80 g/m 2 and a total areal density of less than 100 g/m 2 and wherein all of said polymer particles are melted.
12 . A buoyant ballistic resistant article having positive buoyancy in water, said article comprising a buoyant ballistic resistant material having positive buoyancy in water, wherein said article incorporates one or more armor plates, said armor plates having neutral or negative buoyancy in water, said buoyant ballistic resistant material comprising:
a) a plurality of non-woven plies, each ply comprising a plurality of adjacent, unidirectional fibers and/or a plurality of adjacent, unidirectional tapes, wherein one or more of said fibers/tapes have surfaces that are partially covered by discontinuous patches of a polymeric binder bonded to the fiber/tape surfaces; each ply having an outer top surface and an outer bottom surface; and
b) at least one thermoplastic overlay bonded to at least one surface of at least one of said plies, wherein said at least one thermoplastic overlay only partially covers said at least one surface, and wherein said at least one thermoplastic overlay has a melting point below a melting point of said polymeric binder;
wherein said buoyant ballistic resistant material has a volume that partially comprises empty space, and wherein said buoyant ballistic resistant article is foam-free and has said positive buoyancy in water without air bladder inserts or other buoyancy enhancing components.
13 . The buoyant ballistic resistant article of claim 12 wherein the thermoplastic overlay is a non-woven, discontinuous adhesive web.
14 . The buoyant ballistic resistant article of claim 12 wherein the thermoplastic overlay consists of one or more binding elongate bodies having a melting point below a melting point of said polymeric binder.
15 . The buoyant ballistic resistant article of claim 12 wherein the non-woven plies of the buoyant ballistic resistant material are consolidated and wherein said buoyant ballistic resistant material has a volume that partially comprises empty space, wherein said empty space comprises greater than 20% of said buoyant ballistic resistant material.
16 . The buoyant ballistic resistant article of claim 15 wherein said buoyant ballistic resistant material has a fiber areal density of less than about 80 g/m 2 .
17 . The buoyant ballistic resistant article of claim 12 wherein the patches have an aspect ratio of less than 10:1 and are formed on the fiber/tape surfaces by softening and/or melting a dry, solvent-free polymeric powder.
18 . The buoyant ballistic resistant article of claim 12 wherein the material further comprises a plurality of polymer particles on and/or between said fibers/tapes of each fibrous ply, wherein all of said polymer particles are softened but not fully melted.
19 . The buoyant ballistic resistant article of claim 1 wherein the patches have an aspect ratio of from about 3:1 to about 10:1.
20 . The buoyant ballistic resistant article of claim 12 wherein said armor plates have negative buoyancy in water.