MXPA98006985A - Method for measuring the amount of a polymeric or prepolimer composition - Google Patents

Abstract

A method for measuring the amount of a polymer or prepolymer composition within a given volume that includes the combination of the polymer or prepolymer composition with a plurality of microparticles having a ferromagnetic or non-ferrimagnetic core provided with a coating that is ferromagnetic is disclosed. , ferrimagnetic or conductive, to form a mixture in which the microparticles are dispersed substantially uniformly throughout the composition. The microparticles have a detectable electromagnetic characteristic which correlates with the amount of the composition within a given volume. Then, the electromagnetic characteristic of the microparticles is measured to determine the amount of the composition within a given volume.

Description

METHOD FOR MEASURING THE AMOUNT OF A POLYMERIC OR PREPOLIMERAL COMPOSITION BACKGROUND OF THE INVENTION The invention relates to the measurement of the amount of a polymeric or prepolymer composition within a given volume. Processes for the manufacture of polymeric compositions (e.g., adhesives, such as structural adhesives) often require the addition or combination of precise amounts of prepolymer components that form these compositions, particularly where these components react together to form the composition. The devices that supply these components may malfunction periodically and / or systematically, resulting in the deposition of an incorrect mixture of the components. These malfunctions can significantly affect the quality of the resulting products. It is also desirable to have the ability to measure the amount of a polymeric or prepolymer material in any given volume of an article incorporating the material. For example, in the case of a structural adhesive that joins two substrates together, it is desirable to measure the thickness of the adhesive throughout the adhesive seal for REF.28055 determine if the thickness is uniform. Disuniformities • can affect the performance of the board, to cause it to function defectively in some circumstances.

BRIEF DESCRIPTION OF THE INVENTION In general, the invention features a method for measuring the amount of a polymeric or prepolymer composition within a given volume, which includes the combination of the polymeric or prepolymer composition with a plurality of microparticles having a nucleus. or non-ferromagnetic or non-ferrimagnetic center provided with a coating that is ferromagnetic, ferrimagnetic or conductive, to form a mixture in which the microparticles are dispersed substantially uniformly throughout the composition. The microparticles have a detectable electromagnetic characteristic which correlates with the amount of the composition within a given volume. The electromagnetic characteristic of the microparticles is then measured to determine the amount of the composition within a given volume. As used herein, "prepolymer composition" refers to compositions whose molecular weight has not advanced sufficiently to qualify as a polymeric composition (eg, partially prepolymerized prepolymer syrups), also as individual reactants in the form of reactive monomers or oligomers with themselves or with other reagents to form a polymer composition. In preferred embodiments, the core or center of the microparticles is selected from the group consisting of glass bubbles, glass beads, glass fibers, fumed silica particles, molten silica particles, mica flakes, polymer particles and combinations of the same, glass bubbles are particularly preferred. The coating (which can be provided on substantially all or a portion of the core surface) is preferably a ferromagnetic or ferrimagnetic material. Examples of suitable ferromagnetic or ferrimagnetic materials include nickel, cobalt, iron, alloys thereof and oxides thereof. Stainless steel coatings are particularly preferred. Other preferred coatings include electrically conductive coatings. The dimensions of the microparticles preferably have a larger or longitudinal dimension of between about 10 microns and about 1 millimeter. The average thickness of the coating preferably ranges from about 0.1 nanometers to about 5 microns, more preferably from about 1 nanometer to about 200 nanometers. The amount of the microparticles provided in the mixture preferably ranges from about 0.01 to 50% by volume. In a preferred embodiment, the method is used to measure the amount of a polymer or prepolymer composition that is dispensed, for example to a reaction mixture. According to this embodiment, the mixture containing the microparticles and prepolymer or polymer composition is dispensed while measuring an electromagnetic characteristic of the microparticles to determine the amount of the polymer or prepolymer composition that is dispensed. In yet another preferred embodiment, a first polymer or prepolymer composition and a second polymer or prepolymer composition, combine to form a reaction mixture. At least one of the polymeric or prepolymer compositions is combined with the microparticles before the combination of the first and second polymer or prepolymer compositions together. In a preferred embodiment, the electromagnetic characteristic of the microparticles in the reaction mixture is measured. The microparticles can be placed in the first and second polymeric or prepolymer compositions. The microparticles in the first and second polymeric or prepolymer compositions can be different from each other. Another embodiment includes the combination of the microparticles with one of the polymeric or prepolymer compositions and the measurement of the electromagnetic characteristic of the reaction mixture to determine the ratio of the first and second polymeric or prepolymer compositions to each other. In another preferred embodiment (useful, for example, for quality control measurements), the mixture is deposited on or between a substrate and the electromagnetic characteristic of the microparticles is measured to determine the amount of the mixture deposited on the substrate. In this way, for example, variations in the thickness of the deposited material can be detected. An example of a useful polymer composition is an adhesive composition. Specific examples of preferred polymer compositions include epoxy resins (for example, epoxies cured by base, epoxies cured by acid and epoxies cured by addition), polyurethanes, acrylates, silicones and phenolic compounds. The invention provides a reliable, low cost method for measuring the amount of a polymer or prepolymer composition within a given volume using microparticle "tags" having a detectable electromagnetic characteristic. The microparticles are easily manufactured and are generally chemically inert and stable for reasonable periods of time. In addition, certain properties of the microparticles are very similar to their uncoated counterparts. For example, glass microbubbles coated with metal impart substantially the same rheological behavior and mechanical properties as their uncoated counterparts. Thus, the microparticles can be virtually substituted one by one by their uncoated counterparts on a bulk basis without adversely affecting the properties of the final composition. Other characteristics and advantages of the invention will be apparent from the following description of the preferred embodiments thereof and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph of the inductive reactance against the charge of microparticles coated in percent volumetric fraction. Figure 2 is a graph of the inductive reactance against the coating thickness. Figure 3 is a graph of the permeability against the thickness of the coating.

Figure 4 is a graph of the inductive reactance against permeability. Figure 5 is a scan of the Eddyscope apparatus in an aluminum-epoxy-aluminum structure. Figure 6 is a plot of the inductance against the charge of microparticles coated in percent by volume fraction. Figure 7 is a graph of the capacitance against the charge of microparticles coated in percent volumetric fraction. Figure 8 is a scan of the Eddyscope apparatus of a plastic tray. Figure 9 is a physical map of the tray of Figure 8 prepared using the readings of the Eddyscope apparatus. Figure 10 is a graph of the capacitance against displacement along the width of the tray of Figure 8, with a schematic view of the cross section of the tray shown below the graph. Figure 11 is a scan of the Eddyscope apparatus indicating the different reading obtained with different ratios of a component of an adhesive blended with a second component of an adhesive.

Figure 12 is a scan of the Eddyscope apparatus indicating the different readings obtained from a volume of composition containing several charges of coated microparticles.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Materials Preferred microparticles have a non-ferromagnetic or non-ferrimagnetic core and a coating that is ferromagnetic, ferrimagnetic or electrically conductive. In general, the microparticles may have a variety of shapes, in which substantially spherical, elongated or flat shapes are included. The shape can be selected to impart desired flow properties to the corresponding mixture given a selected concentration of microparticles in the mixture. The dimensions of the microparticles may vary, but the preferred microparticles have a longitudinal or principal dimension less than 1 centimeter and more preferably 10 microns to 1 millimeter. The coating will preferably have an average thickness of between about 1 nanometer and 5 microns and more preferably between about 1 and 200 nanometers. The coating can, but does not need to cover the entire surface of the non-metallic core. For example, the coating can form islands on the surface of the core or the coating material can cover substantially the entire surface. further, the microparticles may have multiple coatings, partial coatings or combinations thereof having different metals. Suitable cores include materials normally used as reinforcing agents, rheology modifiers or other additives in polymeric and prepolymer compositions. examples include glass bubbles, glass beads, glass fibers, sulfurized silica particles, molten silica particles, mica flakes, polymer particles and combinations thereof. Preferred cores include hollow structures (e.g., in the form of bubbles) to minimize the total amount of material added to the prepolymer or polymer composition. Preferred core materials are glass microbubbles, for example, commercially available from 3M Company, Saint Paul, Minnesota under the brand name Scotchlite ™. Preferred core materials include materials that are already within the compositions of interest, such that the coated microparticles can be replaced by the uncoated microparticles in the composition. In this way, the composition can be labeled without requiring reformulation of the composition to obtain the desired rheological properties. The coating for the microparticles can be in general any ferromagnetic, ferrimagnetic or electrically conductive material that can be coated on the surface of the microparticle core. A preferred coating must be chemically inert in the relevant compositions under the relevant conditions and stable with respect to degradation and leaching. Suitable ferromagnetic materials include iron, nickel, cobalt, alloys that include one or more of these metals, and oxides that include one or more of these metals. Suitable electrically conductive materials include metals that can be coated, metal alloys and metal compounds, such as carbides, oxides, nitrides and silicides. Preferred conductive metals for use in coatings include copper, aluminum and silver. The preferred material for the coating is stainless steel, which is electrically conductive and ferromagnetic. If the coating material "is ferromagnetic or ferrimagnetic, the core can be an electrically conductive, non-ferromagnetic, non-ferrimagnetic material, a case in which the measurements will depend on the ferromagnetic or ferrimagnetic properties of the coating.

A variety of techniques can be used to apply the coating to the core. These techniques include electronic deposition (or sputtering), vapor deposition, deposition without electrodes, and chemical vapor deposition. The microparticles are added to a polymeric or prepolymer composition to form a mixture that is a labeled composition. The blend will preferably include between about 0.01 and 50 volume percent of the microparticles and more preferably between about 0.1 and 30 volume percent of the microparticles. A wide variety of prepolymer and polymer compositions can be used in conjunction with the microparticles. Preferred polymeric additive compositions include crosslinked systems, such as epoxies (in which are included epoxies cured by base, epoxies cured by acid and epoxies cured by addition), polyurethanes, silicone resins, acrylate polymers, polysiloxanes and phenolics, also as mixtures of these types of systems. Thermal fusion adhesives include various polyolefins, polyesters, polyamides, polycarbonates, polyvinylacetates, higher molecular weight waxes and copolymers and related mixtures. Additionally, the applicable adhesive compositions would be those which are formed into films and tapes.

Other useful polymeric compositions include sealants, plastisols, structural polymers used in filling spaces and stamping materials, coatings, fibers, gaskets, washers and laminates of various kinds. This invention is applicable to polymeric compositions which are formed by extrusion, molding, calendering, emptying and other processes in three-dimensional forms. An appropriate class includes adhesive compositions, such as structural adhesives which include epoxy resins (eg, derived from diglycidyl ethers of Bisphenol A or novolak resins). Structural adhesives are used in a variety of manufacturing situations that include significant use in the automotive industry to jointly join the parts to reduce the need for welding. These materials, which are well known, are usually prepared at • reacting two or more prepolymer reagents with one another to form an intermediate "step B" resin, which subsequently cures additionally to form the final product. The prepolymer and polymer compositions may contain various adjuvants designed to improve the properties of the resin before or after curing, in which reactive and non-reactive diluents, plasticizers, curing agents and coupling agents are included. Other materials which can be added to the composition include thixotropic agents to provide flow control (eg, fumed silica), pigments, fillers (eg, talc, silica, magnesium, calcium sulfate, beryllium aluminum silicate). , clays, glass and ceramic particles (for example, beads, bubbles and fibers) and reinforcing materials (for example, organic and inorganic fibers).

Use The microparticles described above can be used in a variety of measurement protocols. The measurement of the electromagnetic properties of the microparticles provides a measure of the number of microparticles. The microparticles may be present at a known concentration within the composition to be measured to provide the determination of the amount of the composition. Similarly, the microparticles can be used in a fixed concentration, wherein the amount of the composition incorporating the microparticles is determined from a standard curve produced using the material with the same fixed concentration. If the composition containing microparticles to be measured is mobile (is in motion), the measurement will provide information regarding the flow and correspondingly, the deposition rate. If the composition is fixed relative to a substrate or container, the measurements can provide information regarding the distribution of the composition throughout the substrate or container. A particularly useful application is in the context of the assortment of polymeric or prepolymer compositions, such as adhesive and pre-adhesive compositions. The material to be supplied may be a single polymeric or prepolymer composition which may or may not be polymerized or subsequently crosslinked. This individual composition will be used to form the mixture that includes the microparticles. Alternatively, the material that is dispensed may include two or more polymeric or prepolymer compositions that are mixed to form a curable resin, for example, an intermediate "B" resin. One or more of the components within the curable resin can be combined with a given volume fraction of microparticles. Then, the electromagnetic properties of the microparticles can be checked to measure the amount of the reactant (s) supplied to the reaction mixture. If one of two components is provided with microparticles, the microparticles coated in the reaction mixture can be measured to determine the amount of the reaction mixture. Based on the quantity measurements of the component and the reaction mixture, it can be determined whether the two components were mixed in the appropriate ratio. Alternatively, each component can be mixed with the same or different microparticles. Then, each component can be measured, with or without an additional measurement of the curable resin mixture, to determine if the components have been mixed together in the correct ratio. Any variation of the desired quantity can be noticed and / or used to adjust the quantity that is supplied or fed. If microparticles with different electromagnetic characteristics are placed, for example, a ferromagnetic and the other non-ferromagnetic, in the two different components, the measurements with respect to the two components that are supplied can be determined if the correct component of the dispenser is supplied or supplied. particular. Another application involves the use of microparticles in non-destructive testing of articles that incorporate a polymeric or prepolymeric composition. The measurements can be used to determine a variety of properties of the composition within the article, in which thickness, integrity, orientation and continuity are included. Similarly, a map indicating the location of the composition can be obtained. For example, in the case of structural adhesives forming a joint line for joining together two parts, the properties of the bond line can be examined. The electrical or magnetic properties of the microparticles can be used to carry out the measurement. For example, in the case of ferromagnetic or ferrimagnetic microparticles, magnetic permeability can be measured. Magnetic permeability is a function of the number of ferromagnetic microparticles and the amount of metal coating on the particles. It can be measured using a magnetic alternating current hysteresis measuring caterpillar, for example a Gerard Electronic MH ™ measuring caterpillar operating at a frequency of 10 KHz and an applied field strength of 10 gauss. Normally, the magnetic field is applied with a frequency between 1 and 10 KHz. Alternatively, the inductive reactance can be measured using a swirl current instrument (for example, an impedance plane swirl current instrument, North 19T11 Eddyscope ™, equipped with an Nortee OD / 100KHz / A / l .73 cm probe (0.682 inches)) to measure the amount of microparticles (and thus the amount of the prepolymer or polymer composition) within a given volume. With the proper calibration, the vertical response of the Eddyscope is proportional to the inductive reactance; this response is referred to hereinafter as the inductive reactance. The inductive reactance, that is, the response of the Eddyscope is approximately proportional to the charge of the microparticles and the coating thickness on the individual microparticles. Another way to carry out the measurement is by measuring the dielectric properties of the microparticles. The electrically conductive coatings on the microparticles increase the dielectric constant, which is related to the charge of microparticles. This can be determined, for example, by measuring the capacitance of a parallel plate capacitor containing the microparticles. An advantage of the dielectric measurement method with respect to the magnetic permeability method in certain applications is that the response • Magnetic is related to the amount of magnetic material coated on the microparticles, while the dielectric constant is approximately independent of the thickness of the coating. Accordingly, much thinner electrically conductive coatings can be used when dielectric measurements are used. Other aspects of the electromagnetic properties can be used to carry out the measurements. For example, certain metals can disperse X-rays sufficiently, so that X-ray transmission measurements can be used to quantify the amount of metal-coated microparticles present within a material. Alternatively, coatings can be selected to minimize interference with the transmission of x-rays, so that articles can be examined with x-rays with minimal interference by the coated microparticles. In addition, microwave or induction heating methods can be used to heat the microparticles, after which the associated infrared emissions can be measured to quantitate the amount of microparticles (and thus the amount of polymer or prepolymer composition).

The invention will now be described by means of the following examples.

EXAMPLES Example 1 This example demonstrates that glass bubbles can be coated with a very thin magnetic stainless steel coating. Scotchlite ™ K37 glass bubbles, (sold by 3M, Saint Paul, Minnesota) are coated by deposition with 304 stainless steel, according to the procedure generally described in U.S. Patent No. 4,618,525. In this specific case, a target or target of 304 stainless steel was coated by electron deposition by direct current magnetron for 7.0 hours at 8.0 KW, at an electron deposition gas pressure of 5 millitorricellis argon over 415 grams of glass bubbles Scotchlite K37. The white of the 304 stainless steel electronic deposition was cubic with a centered, austenitic, non-magnetic face, but it is deposited as the cubic form centered in the body, ferritic, magnetic. These materials have been described in a publication by T.W. Barbee, B.E. Jacobson and D.L. Keith, 63 Thin Solid Films 143-150 (1979). The resulting stainless steel coated bubbles have an iron content of 7.86% by weight (determined by inductively coupled plasma emission spectroscopy), corresponding to 11.2% by weight of stainless steel (which is 70% by weight of iron) . The surface area of the glass bubbles is determined by the method of B.E.T. which is 0.55 square meters per gram. The density of the coated bubbles is measured using a Beckman Model 930 air comparison pignometer. The density of the uncoated bubbles was 0.36 g / cc and that of the coated bubbles was 0.41 g / cc. The thickness of the metal coating can be calculated from the relevant relationship described in U.S. Patent No. 5,409,968. In this case, it is determined that the thickness of the coating is 29 nm.

Example 2 This example demonstrates the effect of the volume loading of bubbles coated with stainless steel on the inductive reactance. Glass bubbles are used with a 29 nm thick stainless steel coating. Devcon ™ 5 minute epoxy (ITW Devcon, Danvers, Massachusetts) is used to prepare samples with various volumetric loads of coated bubbles. This mixture is placed in Pyrex ^ M glass tubes of 80 mm long with 13.2 mm internal diameter and an external diameter of 16.0 mm. Then, the inductive reactance is measured using an Eddyscope Nortee apparatus. You can optimize several variables in the Eddyscope. For a given specimen, these are (1) frequency, (2) gain and (3) drive voltage of the specimen. The rotation (knob "Rot" on the instrument) is used to calibrate the Eddyscope apparatus, such that the displacement along the y-axis provides a measure of the inductive reactance. The inductive reactance in unscaled units was read from the screen of the Eddyscope device. Barium ferrite, which is magnetic, but not electrically conductive in any significant way, was chosen as a calibration material. With a fixed frequency at 100 KHz, the rotation is varied until the introduction of the barium ferrite sample results in a purely vertical response on the Eddyscope screen (rotation = 311 degrees). The Eddyscope settings included a gain of 76. 0 dB with "Mid" probe drive. The reactance against the charge of microparticles is plotted in figure 1. This illustrates the linear relationship between the two variables. It shows that the reactance can be used as a good measure of bubble content.

Example 3 This example demonstrates the effect of the thickness of the coating on the inductive reactance. Procedures similar to that in Example 1 are carried out to make glass bubbles coated with stainless steel with coating thicknesses of 59 and 86 nanometers The density for each of the samples of coated bubbles was 0.44 and 0.49 g / cc, respectively. In addition, glass bubbles with a 29 nm thick stainless steel coating were used as in Example 1. The parameters of the Eddyscope are adjusted as in Example 2, except that the gain was 70.0 dB. Epoxy 5-minute epoxy test samples are prepared at 10% by volume loading for each of the three coated bubble samples. The inductive reactance is measured and plotted as a function of the thickness of the stainless steel coating in figure 1. The inductive reactance increases monotonically with the thickness of the stainless steel.

Example 4 In this example, the use of needle particles is demonstrated. Ground glass fibers (Type 731 DD 0.1587 cm (1/16 inch)) obtained from Owens / Corning Corporation (Anderson, South Carolina) are obtained. They have an aspect ratio range of approximately 1 to 40, with a fiber diameter of 15.8 microns. Stainless steel is deposited on 1570 grams of these fibers for 20 hours at 8.0 KW in the manner previously described in Example 1.

It is determined that the weight percent of iron is 6.2%, corresponding to 8.9% by weight of stainless steel. The surface area of the uncoated fibers was 0.10 square meters per gram. The ground glass fibers coated with stainless steel are dispersed in Devcon 5 minute epoxy at a volumetric load of 10%. The mixture is placed in glass tubes as described in example 2. The Eddyscope is adjusted to a gain of 68.0 dB with a "high" specimen drive. It is determined that the inductive reactance is 8.9.

Example 5 In this example, the use of a magnetic cobalt coating is demonstrated. Ground glass fibers are coated by electron deposition with cobalt, as described in Example 1, using a 7.6 cm (3 inch) Magnetron Electrodeposition Source (US Thin Film Products Ine, Campbell, California). It is determined that the cobalt weight percent is 5.6% corresponding to a coating thickness over the fibers of 67 nm. Cobalt-coated ground glass fibers are dispersed at 10% by volume in Devcon 5 minute epoxy and charged to a glass tube as described in Example 4. The Eddyscope is adjusted to the same conditions as in Example 4 , except that the gain is raised to a value of 80.0 dB. It is determined that the inductive reactance is 9.6.

Example 6 In this example, flake-like, flat particles are used. Silicone rubber, instead of epoxy, is used as the polymer component. The stainless steel is deposited on 460 grams of mica flakes 200HK Suzorite ™ (Suzorite Mica, Inc., Hunt, Valley, Maryland) for 13.5 hours at a power of 8.0 KW in the manner described in example 1. The mica flakes, coated with stainless steel, are dispersed at a volumetric load of 10. % in RTV 615 ™, a silicone rubber available from Dow Corning Corporation. This is loaded into a glass tube as described in example 3. The Eddyscope is set to the same conditions as in example 4, except that the gain is set to a value of 60.0. It is determined that the inductive reactance is 8.4.

Example 7 This example illustrates the relationship between the measured magnetic permeability and the thickness of the stainless steel coating on the glass bubbles. The three samples of bubbles covered with stainless steel, described in example 3, are combined with Devcon 5-minute epoxy at a volumetric load of 10%. The material is used to fill tubes (straws) with an internal diameter of 5 mm at a depth of 70 mm. Permeability is determined from a hysteresis curve using a Gerard Electronic MH caterpillar operating at a frequency of 10 KHz and an applied field strength of 10 gauss. The permeability is calculated from the maximum applied field in gauss and the maximum magnetization in emu / cc. A BH measuring caterpillar could also be used. The permeability is plotted against the coating thickness of stainless steel in Figure 3. It is seen that the permeability increases monotonically with the thickness of the coating. This shows that these very thin magnetic coatings can provide significant and reproducible permeabilities. Higher coating thicknesses provide higher permeabilities.

Example 8 This example demonstrates that the inductive reactance for the coated particles is directly related to their magnetic permeability. Magnetic permeability is a fundamental magnetic property of coated microparticles incorporated in an adhesive. The magnetic permeability is related to the response of the Eddyscope, which is the inductive reactance. To demonstrate this relationship, the magnetic permeability measurements of Example 7 are plotted in Figure 4 against the inductive reactance measurements of Example 3 using the same stainless steel coating thicknesses on glass bubbles. The inductive reactance is monotonic and almost proportional to the permeability.

EXAMPLE 9 This example demonstrates the use of magnetic coated microparticles in an adhesive for non-destructive testing. These could be used as a form of non-destructive testing to determine the continuity of the adhesive bond line. Devcon 5 minute epoxy is used to make an adhesive having a volumetric loading of 26% glass bubbles with a 29 nm thick stainless steel coating prepared as described in Example 1. Approximately 1% by volume of beads of glass of 60-100 microns in diameter are added as separators. A cord of this material is laid on an aluminum strip measuring 0.61 mm thick, 19 mm wide and 31 cm long. In the middle part, the adhesive is separated from a space of approximately 3 cm. An identical piece of aluminum is pressed onto the adhesive on the first piece to make an aluminum-epoxy-aluminum sandwich structure. The adhesive which is exuded from both edges of the structure separates after the adhesive has cured. A Nortee SPO-5781 ™ rim specimen of 1 KHZ - 50 KHz is used to explore the structure. The Eddyscope adjusts to 5 KHZ with rotation of 0 degrees and test drive in "Hi". The scan is presented as a screen print in Figure 5. The space in the adhesive between the two pieces of aluminum is clearly shown.

Example 10 This example demonstrates the use of a single solenoid coil in place of a swirl current instrument, such as an Eddyscope, to determine the charge of the coated microbubbles.

A solenoid coil is prepared by winding an insulated copper wire of number 36 (0.127 mm in diameter) on a glass tube with an external diameter of 19.0 mm. The coil has 333 turns in four layers over a length of 3.0 cm. The two coil conductors are connected to a Tenmark 72-370 ™ digital LCR meter. An LCR meter is a portable device capable of measuring inductance, capacitance or resistance when connected to an appropriate sensing device. Glass tubes of 80 mm long, 16.0 mm outer diameter, containing Devcon epoxy with various loads of glass bubbles provided with a stainless steel coating of 29 nm thickness are inserted into a tube (centered in the region of the coil) which has an internal diameter of 16.5 mm. The inductance is read from the LCR meter and plotted against the volumetric load in Figure 6. The approximately linear relationship between the inductance and the load demonstrates the fundamental relationship between the two. This also shows that other equipment than the swirl current instrument can be used to detect charges on the adhesives containing the microparticles.

Example 11 This example demonstrates that capacitance, rather than inductive, measurements can be used to determine the loading of microparticles in the adhesives. A two-plate capacitor is made to detect the capacitance of an adhesive material. Two pieces of copper sheet coated with adhesive are cut to form rectangles 2.0 cm wide x 3.0 cm long. These are fixed outside of a glass tube of the same dimensions as the longest glass tube of example 10. They are set opposite each other to form a curved plate instead of the parallel plate capacitor. The electrical conductors of each plate are connected to the same LCR meter described in example 10. This detection apparatus is loaded with several samples of adhesives containing coated microparticles as described in example 10. The capacitance is read from the LCR meter and it is plotted against the loading of the coated microparticles in the adhesive in FIG. 7. The approximately linear relationship between the two shows that the measurement of the capacitance provides other means for determining the concentration.

Example 13 This example demonstrates the ability of an object made with a material that incorporates microparticles to be represented when using an Eddyscope. It also demonstrates the use of a thermoplastic resin, instead of a thermosetting resin. You get a rectangular plastic tray 3M Company, St. Paul, MN. It is identified as Thin PQFP ™ 131 21002-203. It is 32.3 cm wide by 0.85 cm thick. Contains 24% by volume of ground glass fibers, coated with stainless steel, dispersed in Mindel S1000, a thermoplastic resin obtained from Amoco Chemical Company, Chicago, IL. A Nortee S-300 ™ Hz - 10 KHz / .62 surface specimen is oriented vertically 1 mm above the surface of the tray, so that the tray is allowed to be scanned below it. The Eddyscope device is adjusted with a frequency of 1.0 KHz, a gain of 90 dB, a test drive "Hi" and rotation of 18 degrees. The tray is manually scanned below the specimen, the inductive reactance is recorded against time. "The scan (figure 8) shows a map of the presence of high and hollow points in the tray, as well as a physical map of the tray from the upper side by comparison in figure 9. The scan is made in a straight line from one end of the tray to the other on the second row from the top, as indicated by the horizontal arrow.

Example 13 This example demonstrates the ability of a material that incorporates microparticles to be represented, when using capacitance, in place of an Eddyscope apparatus. A parallel plate capacitor is adjusted for the purpose of scanning the tray of example 12. The upper electrode consists of a rectangle measuring 1.4 cm by 1.0 cm and the bottom electrode measures 15 cm by 15 cm. The spacing between the electrodes is 0.8 cm. The capacitance is measured using the meter described in example 10. The tray is moved through the detector capacitor, the capacitance is recorded in increments of 0.5 cm. The capacitance map is shown in Figure 10 together with a schematic cross section of the tray. The gaps, peaks and valleys on the surface of the tray are clearly indicated in this scan (within the resolution of the upper electrode).

Example 14 This example demonstrates how a displaced relation mixing event can be detected when the adhesive contains coated glass bubbles. The following two component adhesive formulation is prepared by using glass bubbles with a 29 nm stainless steel coating. Part B Parts fR) Density (g / cc) Volume Epon 828 DGEBA 80 1.17 63.38 Epoxy diluent Heloxy 107 20 1.09 18.35 Smoked silica TS-720 2 1.8 1.11 Glass beads 0.25 mm 3 2.5 1.20 Frosted silica GP-71 20 2.2 9.09 Glass bubbles coated with 21.7 0.41 52.93 stainless steel. of 29 nm Total 146.7 151.05 Part A Parts (g) Density (g / cc) Volume Polyamidoamine 40 1.0 40.00 Amina H221 6 0.98 6.12 Tertiary amine Ancamine K54 8 0.97 8.25 Liquid rubber ATBN 1300x16 10 0.96 10.42 Smoked silica TS-720 3 1.8 1.67 Fused silica GP-71 20 2.2 9.09 Total 87 75.54 Epon 828 ™ is a diglycidyl ether of bisphenol A available from Shell Chemical Company. Heloxy 107 is a cyclohexane diglycidyl ether available from Shell Chemical Company. TS-720 is a hydrophobic smoked silica available from Cabot Corporation. The glass beads have a nominal diameter of 0.025 cm (0.01 inches), available from Cataphote, Inc. GP-71 ™ is an amorphous silicon dioxide available from Harbison-Walker Corporation. Glass bubbles are hollow glass microspheres available from 2M Corporation. The polyamidoamine is a polyamide terminated in amine. H221 is 4, 7, 10-trioxatridecane 1,3-diamine available from BASF. Ancamine K52 is 2, 4, 6-trimethylaminomethylphenol available from Air Products Chemical Inc. ATBN 1300x16 is a liquid butadiene rubber terminated in acrylonitrile available from B.F. Goodrich Company. The proper mixing ratio of this adhesive, by weight, is 146.7 / 87 or 1.69 B: A, obtained by dividing the formula weight of Part B by the formula weight of Part A. (In volume, by a similar procedure, the volumetric mixing ratio is 151.05 / 75.54 or 2.0 B: A). By increasing or decreasing 1.69 by 10%, it can be determined that a B: A ratio of 1.86: 1.00 represents a displaced ratio plus 10%, while 1.52: 1.00 represents a displaced ratio minus 10%.

Mixtures of Part A and Part B above are prepared at mixing ratios by weight of B: A of 1.52: 1.00, 1.69: 1.00 and 1.86: 1.00; degassed as they mix; and are subjected to vacuum in three separate static mixer nozzles of 2.7 cm (one half inch). After being filled, the nozzles are inserted into the swirl current specimen as described in example 2. The response of the Eddyscope apparatus was somewhat more consistent when the mixing elements are separated from the static mixing nozzles because the filling of the The nozzles are more uniform without the mixing elements. In a dynamic situation where many liters (or gallons) of mixing adhesive is pumped through a given nozzle, a steady-state response could be obtained. To simulate this dynamic response, the nozzle is moved longitudinally in the specimen. As shown in Figure 11, the responses of the Eddyscope corresponding to the adhesives mixed under the appropriate mixing ratio (control), displacement ratio at -10% and displacement ratio + 10% are easily differentiated from each other. The measured responses can provide a process window within which the mixing ratio can be established and maintained using an adhesive containing coated glass bubbles.

EXAMPLE 15 This example demonstrates the replacement of various amounts of glass bubbles coated by the uncoated glass bubbles already present. A two-component adhesive (16-1) is made using uncoated glass bubbles and corresponding versions (16-2 to 16-6) are made by replacing some or all of the uncoated glass bubbles found in the component B adhesive, with glass bubbles coated with stainless steel that have a stainless steel coating of 29 nanometers. Adhesive component B contained a volumetric fraction of 0.35 glass bubbles.

Parts by weight (g) in component B 16-1 16-2 16-3 16-4 16-5 16-6 Epon 828 DGEBA 80 80 80 80 80 80 Epoxy Diluent Heloxy 107 2200 20 20 20 20 20 Smoked silica TS-720 2 2 2 2 2 2 Glass beads 0.25 nm 3 3 3 3 3 3 Fused silica GP-71 20 20 20 20 20 20 Glass bubbles K37 19.6 19.4 18.6 17.6 9.8 0 Coated glass bubbles 0 0.2 1.1 2.2 10.9 21.7 Tables with stainless steel (29 nm coating) Total foor weight (g) 144.6 144.6 144.7 144.8 145.7 146.7 B: A in weight 1.66: 1 1.66: 1 1.66: 1 1.66: 1 1.67: 1 1.69: 1 B: A in volume 2: 1 2: 1 2: 1 2: 1 2: 1 2: 1 Total volumetric fraction 0.35 0.35 0.35 0.35 0.35 0.35 Bubbles on side B Volumetric fraction of 0.0 0.0035 0.0175 0.035 0.175 0.35 coated bubbles Substitution level on base 0 1 5 10 50 100 to the total volume of bubbles (percent) Part A is given below and used in the mixing ratio given with each of the previous B Parts to form a 2: 1 mixture by volume. The nature of the ingredients of compositions A and B is further described in example 14.

Part A Polyamidoamine 40 Amine H221 6 Tertiary amine Ancamine K54 8 Liquid rubber ATBN 1300x16 10 Smoked silica TS-720 3 Melted silica GP-71 20 Total 87 The volume fraction of the total glass bubbles is kept as close as possible to a value constant for all B components using calculations involving the density of 0.37 g / cc of the uncoated glass bubbles and the density of 0.41 g / cc of the glass bubbles coated with stainless steel.

The parts of all the bubble components are rounded to the nearest 0.1 g. When using the listed mixing ratios and a multiplication factor of 30, the samples of components B 16-1 to 16-6 are mixed under vacuum with the appropriate amount of component A and deposited in bottom plastic weighing disks flat. Mixtures of components are allowed to cure at room temperature to a solid mass of approximately 6.35 cm (2.5 inches) in diameter and at least 1.3 cm (0.5 inches) in thickness. After curing, the disc is detached from the hardened adhesive to present a flat surface which was tested when using a flat surface specimen, North # 954769, S / l KKz - 50 KHz / 0.31. The Eddyscope adjusts to a frequency of 50 KHz, a gain of 67.0 and a rotation of 64 degrees. The adjustment to zero in air and the adjustment of the surface specimen against the flat backgrounds of each of the molded samples containing the coated glass bubbles in turn produce the results shown in Figure 12. (The signal for the material 16-2 is weak due to the desire to adjust the data for all samples on the same screen / graph, but it could be increased by adjusting the gain to a level greater than 67.0.) The data clearly shows the systematic way in which the signal is increased with the increased replacement of bubbles coated by uncoated bubbles, for example, with the signal for 10% substitution which is approximately twice that for 5%, the signal for 50% is approximately five times that for 10% and so on.The sample prepared using 16-1 mixed with Part A did not give a measurable Eddyscope response.

Equivalent Several modifications and alterations to this invention will become apparent to those skilled in the art, without departing from the scope and essence of this invention. It should be understood that this invention is not intended to be unduly limited by the illustrative embodiments and examples summarized herein and that such examples and embodiments are presented by way of examples only, the scope of the invention being proposed to be limited only by the claims summarized below. It is noted that, in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following

Claims (10)

1. Claims 1. A method for measuring the amount of a polymeric or prepolymer composition within a given volume, characterized in that it comprises the steps of: (a) combining the polymer or prepolymer composition with a plurality of microparticles comprising a non-ferromagnetic core or not ferrimagnetic provided with a coating that is ferromagnetic, ferrimagnetic, electrically conductive or a combination thereof, to form a mixture in which the microparticles are dispersed substantially uniformly throughout the composition, the microparticles have a detectable electromagnetic characteristic, which correlates with the amount of the composition within a given volume; (b) measuring the electromagnetic characteristic of the microparticles to determine the amount of the composition within a given volume.
2. 2. The method according to claim 1, characterized in that the core of the microparticles is selected from the group consisting of glass bubbles, glass beads, glass fibers, fumed silica particles, fused silica particles, flakes of mica, polymer particles and combinations thereof.
3. 3. The method according to claim 1, characterized in that the coating comprises an electrically conductive coating.
4. 4. The method according to claim 1, characterized in that the coating comprises a ferromagnetic or ferrimagnetic coating.
5. 5. The method according to claim 1, characterized in that the coating comprises stainless steel.
6. 6. The method of compliance with the claim 1, characterized in that the microparticles comprise glass bubbles coated with metal. The method according to claim 1, characterized in that the coating comprises a ferromagnetic or ferrimagnetic composition, selected from the group consisting of nickel, iron, cobalt, alloys thereof and oxides thereof. The method according to claim 1, characterized in that it comprises the combination of a first polymeric or prepolymer composition with a second polymeric or prepolymer composition, to form a reaction mixture, the method co-compares the combination of at least one of the polymeric or prepolymer compositions with the microparticles before the combination of the first and second polymeric or prepolymer compositions together. The method according to claim 8, characterized in that the microparticles in the first polymeric or prepolymer compositions are different from the microparticles in the second polymer or prepolymer composition. The method according to claim 1, characterized in that it comprises the deposition of the mixture on a substrate and the measurement of the electromagnetic characteristic of the microparticles, to determine the quantity of the mixture deposited on the substrate.