MACRO
In relation to composites, denotes the gross properties of a composite as a structural element, but does not consider the individual properties or identity of the constituents.

MALE MOLD
A convex mold where the concave surface of the part is precisely defined by the mold surface.

MANDREL
The core around which paper-, fabric-, or resin-impregnated glass is wound to form pipes, tubes, or vessels; in extrusion, the central finger of a pipe or tubing die.

MASS
The quantity of matter contained in a specific body. In reference to polyesters, mass is measured in mils or inches thickness of a film or casting.

MASTER (Plug)
The permanent tool used to build molds for the manufacture of fiberglass parts.

MAT
A fibrous material for reinforced plastic consisting of randomly oriented chopped filaments or swirled filaments with a binder; and available in blankets of various widths, weights, and lengths.

MAT BINDER
Resin applied to glass fiber and cured during the manufacture of mat, to hold the fibers in place and maintain the shape of the mat.

MATCHED DIE MOLDING
Technique for producing long runs of identical parts with two finished sides.

MATCHED MOLDS
Two or more tools arranged in a set as a male and female mold.  Normally used in a press.

MATCHED METAL MOLDING
A reinforced plastics manufacturing process in which matching male and female metal molds are used ( similar to compression molding) to form the part - as opposed to low pressure laminating or spray-up.

MATERIAL ACCEPTANCE
The testing of incoming material to ensure that it meets requirements

MATERIAL QUALIFICATION
The procedures used to accept a material by a company or organization for production use.

MATERIAL SYSTEM
A specific composite material made from specifically identified constituents in specific geometric proportions and arrangements and possessed of numerically defined properties.

MATRIX
A material in which the fiber of a composite is embedded; it can be plastic, metal, ceramic, or glass.

MECHANICAL PROPERTIES
The properties of a material that are associated with elastic and inelastic reaction when force is applied, or the properties involving the relationship between stress and strain.

MEK PEROXIDE (MEKP)
Abbreviation for Methyl Ethyl Ketone Peroxide; a strong oxidizing agent (free radical source) commonly used as the catalyst for polyesters in the FRP industry.

MEK SOLVENT
Abbreviation for Methyl Ethyl Ketone; a colorless, flammable liquid commonly used in gun clean up procedures.

METAL-MATRIX COMPOSITES
Materials in which continuous carbon, silicon carbide, or ceramic fibers are embedded in a metallic matrix material.

MICRO
In relation to composites, denotes the properties of the constituents, i.e., matrix and reinforcement and interface only, as well as their effects on the composite properties.

MICROBALLOONS
Microscopic bubbles of glass, ceramic or Phenolic, used as a filler or to create syntactic foam or putty mixtures.

MICROCRACKING
Microscopic cracks formed in composites when thermal stresses locally exceed the strength of the matrix.

MICRON
One micron = .001 millimeter = .00003937 inch.

MICROSPHERES
Microscopic bubbles of glass, ceramic or phenolic, used as a filler or to create syntactic foam or putty mixtures.

MIL
The unit used in measuring film thickness and the diameter of glass fiber strands, wire, etc. (one mil = .001")

MIL THICKNESS
MILS - The unit used in measuring film thickness.  One mil equals one thousandth of an inch.  (1mil = .001).

MILLED FIBERS
Crushed glass used generally for making glass filled putty.

MODULUS
A number which expresses a measure of some property of a material: modulus of elasticity, shear modulus, etc.; a coefficient of numerical measurement of a property. (Note: The use of the word without modifying terms may be confusing; and such use should not be encouraged.)

MODULUS, CHORD
The slope of the chord drawn between any two specified points on the stress-strain curve.

MODULUS OF ELASTICITY
The ratio of the stress or load applied to the strain or deformation produced in a material that is elastically deformed. If a tensile strength of 2000 pounds per square inch results in an elongation of one percent, the modulus of elasticity is 2000 divided by 0.01, or 200,000 pounds per square inch (Young's Modulus).

MOISTURE ABSORPTION
The pick-up of water vapor from air by a material. It relates only to vapor withdrawn from the air by a material and must be distinguished from water absorption, which is the gain in weight due to the take up of water by immersion.

MOISTURE CONTENT
The amount of moisture in a material determined under prescribed condition and expressed as a percentage of the mass of the moist specimen, i.e., the mass of the dry substance plus the moisture present.

MOISTURE EQUILIBRIUM
The condition reached by a sample when it no longer takes up moisture from, or gives up moisture to, the surrounding environment.

MOLD
The cavity or matrix into or on which the plastic composition is placed and from which it takes form; to shape plastic parts or finished articles by heat and pressure; the assembly of all the parts that function collectively in the molding process.

MOLD COAT
A coat of resin over the bare mold. Used to seal the mold and make a smooth surface on which to mold parts. This is essentially the same as a gel coat.

MOLD-RELEASE AGENT
A liquid or powder used to prevent sticking of molded articles in the cavity.

MOLD SHRINKAGE
The immediate shrinkage which a molded part undergoes when it is removed from a mold and cooled to room temperature; the difference in dimensions, expressed in inches per inch between a molding and the mold cavity in which it was molded (at normal temperature measurement); the incremental difference between the dimensions of the molding and the mold from which it was made, expressed as a percentage of the dimensions of the mold.

MOLDED EDGE
An edge which is not physically altered after molding for use in final form and particularly one which does not have fiber ends along its length.

MOLDING
The process of using a mold to form a part.

MOLDING COMPOUNDS
Plastics in a wide range of forms to meet specific processing requirements. Granules or pellets are popular forms.

MOLDING CYCLE
The period of time occupied by the complete sequence of operations on a molding press requisite for the production of one set of moldings; the operations necessary to produce a set of moldings without reference to the time taken.

MOLDING PRESSURE
The pressure applied to the ram of an injection machine or press to force the softened plastic completely to fill the mold cavities.

MOLDING PRESSURE, COMPRESSION
The unit pressure applied to the molding material in the mold. The area is calculated from the projected area taken at right angles to the direction of applied force and includes all areas under pressure during complete closing of the mold. The unit pressure is calculated by dividing the total force applied by this projected area, and is expressed in pounds per square inch.

MOLD RELEASE
A wax or polymer compound that is applied to the mold surface which acts as a barrier between the mold and the part, thus preventing the part from the bonding to the mold.

MOLECULES
Chemical units composed of one or more atoms.

MONOFILAMENT
A single filament of indefinite length. Monofilaments are generally produced by extrusion.

MONOLAYER
The basic laminate unit from which cross-plied or other laminates are constructed.

MONOMER
A simple molecule which is capable of reacting with like or unlike molecules to form a polymer; the smallest repeating structure of a polymer (mers); for addition polymers, this represents the original unpolymerized compound.

MULTIFILAMENT
A yarn consisting of many continuous filaments.

MULTIPLE-CAVITY MOLD
A mold with two or more mold impressions; that is, a mold which produces more than one molding per molding cycle.

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Glossary Section (M) Last Updated: 4/13/00 3:34 PM

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