Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-11-08
2001-01-09
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S242000, C428S902000, C428S911000, C264S136000, C264S258000
Reexamination Certificate
active
06172163
ABSTRACT:
The present invention relates to novel polyolefin composites. More particularly, the invention relates to novel polyolefin composites material based on fiber and matrix of ultra-high molecular weight of polyolefin and to a process for the manufacture thereof.
BACKGROUND OF THE INVENTION
Polyolefins are considered non-polar polymers, used for many purposes such as, filaments, tapes, fibers, films, etc. One of the main field of polyolefins use is in the manufacturing of composite materials.
As known, a main problem encountered with production of composites, is the non-polarity of the polyolefins, which causes difficulties in obtaining a good adhesion between the non-polar polyolefins and the extraneous materials, such as plastic or resin, which generally are more polar than the polyolefins.
Ultra-high molecular weight polyethylene (hereinafter referred to UHMWPE) is a linear high density polyethylene (HDPE) with a molecular mass in the range of between 1×10
6
to 16×10
6
. Its very high molecular mass imparts an exceptional impact strength and abrasion resistance as well as special processing characteristics. These unusual properties preclude the use of conventional extrusion and moulding techniques.
Fibers made from this type of polyethylene are characterized by their high modulus and strength, light weight and high energy dissipation in comparison with other polymer fibers. However, the standard extrusion and molding techniques for obtaining fibers of UHMWPE are not applicable.
A main deficiency of UHMWPE fibers in its use as reinforcement in composites materials, is their relatively poor adhesion to the matrix in a composite and their chemical inertness as mentioned in a recent review (D. N. Hild et al, J. Adhesion Sci. Technol. 6, p. 879, 1992). As known, the stress-transfer ability of the fiber-matrix interface and accordingly the mechanical properties of such composites are greatly affected by the level of the fiber-matrix adhesion. The compatibility between the thermoplastic UHMWPE fiber and the thermoset resins is also limited due to the non-polar property of the polyethylene.
Composites of polyethylene and UHMWPE, obtained by hot compression molding at a temperature between the melting points of the fibers and the polyethylene matrix, were found to comprise a uniform transcrystalline layer of the polyethylene melt on the UHMWPE fiber surface (Teishev et al. J. Appl. Polym. Sci., 50, 1993, p.503).
The European Patent Application Number 313,915 is suggesting a process to improve the adhesion of polyolefin objects to polar polymer matrices. The process involves a treatment of the surface of polyolefin objects obtained from a solution or melt, having a molecular weight of at least 400,000 g/mol, by its immersion into a solvent at a temperature above that of the polyolefin dissolution. A most preferred solvent which is suggested is xylene. It is claimed that the treated objects according to this process retain their adhesive strength to the polar matrices for a long period of time.
In the U.S. Pat. No. 4,563,392, it is described a method for obtaining a coated polyolefin fiber having an increased adhesion to matrix materials. According to this method the multifilament fiber having a molecular weight of above 500,000, is coated with a polymer possessing the ethylene or propylene crystallinity, said coating being between 0.1% to about 200% by weight of the fiber.
According to a very recent paper by Roger S. Porter et al (Polymer, 35, 23, 1994, p.4979-84), high-modulus and high-strength UHMWPE bars or films are obtained, by a two-stage drawing technique: by direct compaction followed by calendering at a temperature below the melting point.
In another recent paper by B. L. Lee et. al. (Journal of Composite Materials, Vol. 28, No. 13.1994, p. 1202-26), there are described tests which were carried out on polyethylene fiber-reinforced composites and examined under ballistic impact loading.
The above brief review, illustrates that the subject of fiber and matrix of UHMWPE composite material is indeed considered an interesting problem which indicates that it requires more investigation.
It is an object of the present invention to provide novel composite materials based on fiber and matrix of UHMWPE. It is another object of the present invention to provide a process for obtaining composite materials based on UHMWPE having improved mechanical properties. It is yet another object of the present invention to provide a process for obtaining a material based on fibers of UHMWPE with improved adhesion property to a polymer matrix.
BRIEF DESCRIPTION OF THE INVENTION
The file of this patent contains at least one drawing executed in black and white photographs. Copies of this patent with the photograph(s) will be provided by the Patent and Trademark Office upon request and payment of necessary fee.
The invention relates to a polyolefin composite material based on fiber and matrix (hereafter referred to composite material) of a polyolefin selected from polyethylene and polypropylene possessing improved mechanical properties, comprising a net-work of fibers and matrix having a molecular weight of above 500,000, said net-work being held together by compressed and crystallized molecular brush layers obtained by swelling of the external surface of said fibers and reciprocal entanglement with it of the polymer matrix. According to a preferred embodiment, the tensile strength of said composite material is at least 75% of the volume average tenacity of the polyolefin fiber net work and matrix. A process for obtaining the polyolefin composite material as well as the significant advantages thereof are also described.
REFERENCES:
patent: 5160472 (1992-11-01), Zachariades
Vaykhansky et al, “Retardatioin of Dissolution and Surface Modification of High Modulus Poly(ethylene) Fiber by the Synergetic Action of Solvent and Stress”,J. Polymer Science: Part B, Polymer Physics, 33: 1031-1037, 1995.
Teishev et al, “Polyethylene Fibers- Polyethylene Matrix Composites: Preparation and Physical Properties”,J. Applied Polymer Science, 50: 503-512, 1993.
Marais et al, “Manufacturing and Mechanical Characterization of Unidirectional Polyethylene-Fibre/Polyethelyne-Matrix Composites”,Composites Science&Technology, 45: 247-255, 1992.
Cohen Yachin
Rein Dimitry
Vaykhansky Ley
Asinovsky Olga
Friedman Mark M.
Seidleck James J.
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