UPDATED VERSION: This paper as originally written was presented by the author at the Functional Fillers 95 conference held in Houston, Texas December 4-6, 1995. The purpose of the paper at that time was to encourage involvement in developing ultra-performance abrasion-resistant thermoplastics alloyed with titanium carbide as the performance booster. The paper is edited herewith for brevity and to reflect changes since that time.

Resistance to mechanical wear and surface stresses, as related to advanced materials, covers a wide range of performance characteristics. Inherently, wear and frictional stresses imposed on mechanical components and machinery-parts are countered to prevent premature replacement.

Today, the polymer industry makes commonplace use of functional fillers in engineering resins to improve performance characteristics and prevent premature replacement. Increasing costs of energy, maintenance downtime and compliance with regulations have all necessitated dramatic changes in industry's approach to materials engineering. New polymer products are emerging to challenge steel and other metal alloys. Filled or alloyed plastics are increasingly replacing mechanical components and machinery-parts made from steel and metal alloys.

Today, nearly fifty-percent of newly-designed mechanical moving parts are being made using more advanced engineering polymer alloy composites. These emerging composites are lighter in weight, have excellent mechanical properties and are designed to be virtually indestructible. The combination of these lighter weight and high-performance mechanical properties results in significant cost savings in energy consumption and downtime. Mechanical components and machinery-parts made with filled or alloyed plastic composites are being manufactured at costs that are competitive and well within market tolerances.

NEW APPROACH
Increasing demands from industry to create even higher performing materials to make longer-lasting machinery-parts with reduced friction and greater abrasion resistance has led to the development of a distinctively new approach to functional fillers for thermoplastics. This new approach involves super-hard inorganic micro-particles of titanium carbide that are chemically altered with an organic material and combined with the thermoplastic host resin. The combination offers some of the best attributes of powder metallurgy interwoven with solid state polymer chemistry. Reduced friction and higher levels of abrasion resistance comes from the presence of the titanium carbide as tiny particulates in the matrix of the consolidated molded bulk structure.

This new approach has great potential in creating distinctive new grades of abrasion-resistant plastics having wear-life ratios in high-stress mechanical applications better than 4X over un-alloyed versions. The alloying product marketed as TiC-FineParticle™ alloys are produced by Pacific Particulate Materials, Ltd.; thermoplastic host resins are produced by any one of the many companies in the advanced materials and chemicals industry.

NOVEL BLENDING CONCENTRATES
Pacific Particulate Materials also offers a unique version of the alloying technology by coupling the TiC-FineParticle™ alloys with surface-modified UHMWPE [Ultra High Molecular Weight Polyethylene] particless. This forms a powdered blending concentrate that adds "muscle" when dispersed into any engineering resin of choice. Masterbatch blending concentrates can be made [by any compounder] as pelletized feedstocks that are dust-free and easier to handle in comparison to powders. Concentrates are sold to the converters for direct molding into net-shape products or extruded into stock-shapes and profiles.

ABOUT THE CONCEPT
Most people will want to invent their own distinctive grades of high-performance plastics where the use of TiC-FineParticle™ alloys hold great promise.

As lightweight, abrasion-resistant and low friction functional fillers, there are no metallic materials or inert inorganic materials contained therein to interfere with the interfacial chemical bonding process between the super-hard primary TiC-FineParticle™ alloy and the thermoplastic matrix. During consolidation, the alloy (micrograins) retains its molecular structure and is a self-bonding medium attaching to the carbon atoms of the thermoplastics.  In a tribological sense, the round-shaped, ball bearing-like alloy micrograins provide solid-state "sliding" wear resistance and reduced coefficient of friction to as low as .018 at the contact surfaces of non-rolling element or plain bearings.

Another benefit of the TiC-FineParticle™ alloys is protecting the polymer matrix from creep and erosion. Unique composites can be made virtually resistant to chemical and thermal attack.

Regardless of which thermoplastic host resin is used, the following combinations of enhanced performance characteristics will be exhibited without loss of tensile properties:

• Improved abrasion-resistant properties
• Dramatic reduction of coefficient of friction
• Higher compressive strengths
• Improved creep resistance
• Tighter,stronger interfacial bonding capability

USEFUL COMPOSITES
A useful practice of the industry is to tailor specific mechanical properties into selected com-positions. Favorable results are dependent on the compositional variations, particle size, processing and post-molding thermal treatments.

One example of a versatile carbide-polymer composite is a melt-processable polyolefin compound with a reacted-imide resin (20% by weight). The compound is comprised of various polyethylenes with molecular weight variations, including the reactive gas treated transition resin. The reacted-imide provides thermal improvement and dynamic enhancement.

The TiC-FineParticle™ hard phase alloy element provides the abrasion resistance and lubricity.

Thermoplastics based on aromatic polyketones have upper useful temperature ranges for continuous operation that exceed of 500°F (260°C). The polyketones have exceptionally high temperature stability combined with attractive flexural, tensile and fatigue properties.

The addition of TiC-FineParticle™ alloys adds greater versatility to the ketones. The most commercially important member of the aromatic polyketones is PEEK

Polyimide engineering resins have outstanding mechanical properties for high-performance component parts. These high-temperature polyimides stand as a class by themselves with glass transition temperatures higher than 660°F (350°C). Polyimides can be expected to withstand continuous exposure to surface temperatures to 700°F (371°C).

The inclusion of TiC-FineParticle™ alloys favors improved abrasion resistance of the polyimide blends. These polyimide blends include the fluoroplastic resins, polyamide-imides and thermo-plastic molded and cast polyurethanes. Reduction of the coefficient of friction to as low as .018 can be accomplished when TiC-FineParticle™ alloys and polyimide is included in the blend.

ABRASION WEAR TEST DATA
A very aggressive accelerated "simulative" wear test method was used to measure comparative abrasion wear behavior of various engineering thermoplastic composites. Aggressive, because both the wearing surface [specimen compact] and the abrasive carrier [described below] are moving against each other. Compact wear specimens were molded using the following materials:

• P84 Polyimide [HP Polymer,Inc.] without TiC-FineParticle™ Alloy
• P84 Polyimide 30% Carbon Fiber without TiC-FineParticle™ Alloy
• P84 Polyimide 30% TiC-FineParticle™ Alloy in Transition Blending Concentrate
• P84 Polyimide 30% Carbon Fiber 30% TiC-FineParticle™ Alloy in Concentrate
• PEEK 450P [Victrex] without TiC-FineParticle™ Alloy
• PEEK 450P 30% Carbon Fiber [CF] without TiC-FineParticle™ Alloy
• PEEK 450P 30% TiC-FineParticle™ Alloy in Transition Blending Concentrate
• PEEK 450P 30% CF 30% TiC-FineParticle™ Alloy in Concentrate
• UHMWPE GUR4150 [Ticona] without TiC-FineParticle™ Alloy
• UHMWPE GUR4150 with TiC-FineParticle™ Alloy in Concentrate
• PEEK 450P 50% TiC-FineParticle™ Alloy in Transition Blending Concentrate
• PEEK 450P 15% Fine Diamond Powder 15% Transition Blending Concentrate

Each compact was molded 1 1/4" diameter x approximately 3/8" thick. The contact surface area at the wear interface is 1.227 square inches. The contact surface area is cleaned and the edge is slightly chamfered.

The test uses a 240 grit, 8 inch diameter abrasive-on-disk rotating at 125 rpm. The compact is mounted in a fixture and loaded under 40 lb. of force. When tests are conducted, the compact is oscillating across abrasive-on-disk and rotating at 40 rpm. The disk can be water-flushed to remove unwanted worn-off particles and keep the wearing surface clean and cool. Each test is 8 minutes. Specimen compacts are weighed "before and after" and weight losses are determined.

Densities are calculated or determined by the liquid displacement method. Wear rates are calculated from the measured mass losses and densities.

OTHER CHARACTERIZATION WORK

Engineering Data
UHMWPE [GUR 4150]	Unfilled	15% TiC-Fine Particle Alloy	30% TiC-Fine Particle Alloy
Tensile at Yield (psi)	4245	4311	4380
% Elongation at Yield	31.5	30	28.9
% Elongation at Break	80.1	58.8	46.5
Flexural Modulus (psi)	13517	12493	3519
Flexural Strength [ft/lb/in2]	3959	4052	4260
Gardner Impact	176	156	136
Abrasion Resistance (in/hr)	0.181	0.056	0.022
PTE AND P84 POLYMIDE 2nd RESIN	Unfilled	15% TiC-Fine Particle Alloy	30% TiC-Fine Particle Alloy
Tensile Strength (psi)	3500	3600	4200
% Elongation (break)	350	289	255
Abrasion Resistance (in/hr)	0.756	0.48	0.396

Even the lowest priced resins can be converted into ultra-performance abrasion resistant composites with reduced friction without sacrificing tensile properties. When compared to other functional fillers, TiC-FineParticle™ alloys will enable the following effects:

• Isotropic properties throughout molded bulk structures
• Microstructural homogeneity (primary alloy to matrix)
• Same tribological properties throughout molded bulk structure
• Increased rigidity
• A one-to-ten percent increase in glass transition temperature
• Chemical compatibility of concentrate and matrix
• Polished, mirror-like finishes attainable

Microscopic examinations confirmed that the TiC-FineParticle™ alloy, when introduced to the thermoplastic host resin, forms a truly significant chemical bond. No other super-hard material known is able to bond with the same tenacity. Both composite powders and molded test specimens were observed by scanning electron microscopy and optical metallography. The super-hard micro-grains in the final composite structure will indeed react together [at a molding temperature of 474°F or greater] causing favorable phase relationships between the inorganic hard-phase and the organic continuous-phase. Indications from the studies were that little or no degradation of thermal properties occurred. The studies showed that transition resins [surface modified as described herein] would enhance the ultimate bonding capability. This bonding provides a stronger means over the mechanically interlocking varieties of fillers that may claim improved wear-resistance.

The energy necessary to degrade the strongly-bonded TiC-FineParticle™ alloy during mech-anical operations are higher, thereby allowing longer periods of time before dislodging the super-hard particles and rendering a mechanical-part out of service.

LABORATORY
Microscopic examinations confirmed that the TiC-FineParticle™ alloys, when introduced to any thermoplastic resin matrix, forms a truly significant chemical bond. No other super-hard material known is able to bond with the same tenacity.

Both composite powders and molded test specimens were observed by scanning electron microscopy and optical metallography. The super-hard micro-grains in the final composite structure will indeed react together causing favorable phase relationships between the inorganic hard-phase and the organic continuous-phase. Indications from the studies were that little or no degradation of thermal properties occurred. This bonding provides a stronger means over the mechanically interlocking varieties of fillers that may claim improved wear-resistance.

Further analysis of laboratory work performed confirmed that the inclusion of TiC-FineParticle™ alloys in any thermoplastic composite will maintain or slightly improve tensile strength - indicating composite homogeneity and improved rigidity in a bulk molded end-product.

TECHNOECONOMICS
TiC-FineParticle™ alloys are designed to reduce costs by improving tribological properties that lower end-use operating costs. The use of TiC-FineParticle™ alloys in demanding plastics applications as replacements for metal alloys and steel is an engineering economics decision.

DESIGNING MACHINERY-PARTS
When designing machinery-parts for extreme operating conditions, the same principals are applied in the use of engineering plastics as with alloy steel billets, bars, tubing, castings, forgings and most other mill products.  Even in welding, engineering plastics can be welded using ultrasonic, friction and hot-plate welding techniques. The same processing principles are also involved in plastics applied by flame spraying.

In most applications, the molded part must be fully consolidated and not remain in the "green" state. This may require post thermal heat treatments in the same manner that metals are heat-treated.

Machineability of the carbide-polymer composite must be considered; and, with some resins, the molded shape may require annealing or stress relieving to improve machineability rates and relieve molded-in stresses and/or, the machined-in stresses.

Surface characterization of the finished machinery-part must be considered - especially because TiC-FineParticle™ alloy-loaded plastic surfaces can be polished to smooth, mirror-like finishes if needed.

Typically, when plastics rub against plastics in moving part applications, wear on the opposing counter-faces is much more severe than in plastic to metal couples. However, TiC-FineParticle™ alloy formulations can be designed to match and achieve frictional and load-bearing properties in plastic-to-plastic counter surface applications.

Each resin has its own distinctive characteristics and design features. TiC-FineParticle™ alloys and concentrates are intended to supplement these distinctions (and not be detrimental to important design properties). For example, most functional fillers with less than adequate adhesion qualities will be detrimental to ultimate elongation of the polymer composite. This is because filler particles tend to interfere with matrix deformation and act as crack initiation sites.

TiC-FineParticle™ concentrates with their ultra-fine rounded particles and superior chemical bonding characteristics to the matrix have features that make for outstanding machinery-part designs from multiphase carbide-polymer composites.

ABOUT TITANIUM CARBIDE
The TiC-FineParticle™ alloys are first derived by a reaction technology using titanium dioxide powders and carbon powders as starting materials. Carburization results in the formation of inert carbides.

A unique chemistry is applied during the reaction cycle converting the inorganic surfaces to organic surfaces. As distinguished from other alloying systems, the process provides the added advantage of chemical bonding between the TiC-FineParticle™ surfaces and the resin matrix.
Properties:

• Hardness (Vickers) = 3400 VHN (1/2 Diamond)
• Melt Temperature = 5400°F (3100°C)
• Density = 4.79 or .173 pci
• Modulus = 67 x 106 psi
• Chemically inert - Oxidation-resistant - Conductive [anti-static]
• Thermal Conductivity @ 20°C = .041 cal/s-cm-°C
• Coefficient of Linear Thermal Expansion = 4.1x10µin/in/°F [.02%@600°F]

Comparative CLTE:

• Carbon and Graphite 1.5
• Alloy Steel 6-8.0
• Polyimide/Carbon Fibered 6.0
• Superalloys 8-10.0
• Zinc and Aluminum 11-19.0
• UHMWPE/Glass Fibered 24.0
• Polyimide 28
• Copper 100-200

CONCLUSION
The number of advanced engineering plastic materials and the opportunities for use in metal-replacement applications are increasing.

The use of super-hard inorganic materials as functional fillers for creating distinctive grades of abrasion-resistant plastics enhances the prospects.  The TiC-FineParticle™ technology enables manufacturers to produce high-performance plastics for critical moving part applications with considerable cost savings in energy consumption and replacement.

They can compete with metals and ceramics for applications operating under extreme conditions where abrasion, friction, creep and high loadings conspire to lower economic performance.

Reduced downtimes for repair and replacement offsets added cost of TiC-FineParticle™ alloys.

ACKNOWLEDGMENTS
Distinguished colleagues who have made it possible to bring the TiC-FineParticle™ alloying technology to the commercialization stage at practical economic levels.

Contact PPM

Phone Number: 1-604-937-5530