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Return to Terminology
R
- Radar
- Radar (radio detection and ranging), system or technique for
detecting the position, motion, and nature of a remote object by means of radio waves
reflected from its surface. Radar systems transmit pulses of electromagnetic waves by
means of directional Antennas; some of the pulses are reflected by objects in the
path of the beam. Reflections are received by the radar unit, processed electronically,
and converted into images on a Cathode-Ray Tube. The
distance of the object from the radar source is determined by measuring the time required
for the radar signal to reach the target and return. The direction of the object with
respect to the radar unit is determined from the direction in which the pulses were
transmitted. In most units, the beam of pulses is continuously rotated at a constant
speed, or it is scanned (swung back and forth) over a sector at a constant rate. The
velocity of the object is sometimes determined by the Doppler Effect:
if the object is approaching the radar unit, the frequency of the returned signal is
greater than the frequency of the transmitted signal; if the object is receding, the
returned frequency is less; and if the object is not moving relative to the radar unit,
the frequency of the returned signal is the same as the frequency of the transmitted
signal. Most radar units operate on microwave frequencies.
- Radial Velocity
- Radial velocity, the speed with which a star moves toward or
away from the sun. It is measured from the Red Shift or
blue shift in the star's spectrum. Also Proper Motion.
- Radiation
- Radiation is the emission or transmission of energy in the
form of Waves through space or through a material medium; the
term also applies to the radiated energy itself. The term includes electromagnetic,
acoustic, and particle radiation, and all forms of ionizing radiation. According to Quantum Theory,Electromagnetic
Radiation may be viewed as made up of Photons. Acoustic
radiation is propagated as sound waves. Examples of particle radiation are alpha and beta
rays in Radioactivity, and Cosmic
Rays.
- Radiation Sickness
- Radiation sickness is the illness caused by the effects of
radiation on body tissues. It may be acute, delayed, or chronic and may occur after
repeated (cumulative) exposure to small doses of radiation (as in a plant, a laboratory,
or the environment); undue exposure to solar radiation; or exposure to a nuclear
explosion. Symptoms may be mild and transitory, or severe, depending on the type of
radiation, the dose, and the rate at which exposure is experienced. They include weakness,
loss of appetite, vomiting, diarrhea, a tendency to bleed, increased susceptibility to
infection, and—in severe cases—brain damage and death. Mild radiation sickness
is a common side effect of radiation therapy for Cancer. Exposure to radiation is of
concern even in small doses because of possible long-term genetic effects.
- Radio
- Radio, transmission or reception of Electromagnetic Radiation in the radio frequency range
from one place to another without wires. For the propagation and interception of radio
waves, a transmitter and receiver are employed. A radio wave carries information-bearing
signals; the information may be encoded directly on the wave by periodically interrupting
its transmission ( Telegraph) or impressed on the carrier frequency by a process
called Modulation, e.g., amplitude modulation (AM) or frequency modulation (FM). In
its most common form, radio transmits sounds (voice and music) and pictures ( Television). The sounds (or images) are converted into
electrical signals by a Microphone (or camera tube), amplified ( Amplifier),
and used to modulate a carrier wave that has been generated by a transmitter. The
modulated carrier is also amplified, then applied to an Antenna that converts the
electrical signals to electromagnetic waves that radiate into space at the speed of light.
Receiving antennas intercept part of this radiation, convert it back into electrical
signals, and feed it to a receiver. Once the basic signals have been separated from the
carrier wave, they are fed to a Loudspeaker or Cathode-Ray
Tube, where they are converted into sound and visual images, respectively. Some
celestial bodies and interstellar gases emit relatively strong radio waves that are
observed with radio telescopes composed of very sensitive receivers and large directional
antennas ( Radio Astronomy). Long-range radio signals enable communications between
astronauts and ground-based controllers and carry information from Space Probes as
they travel to and encounter distant planets. The invention of the Transistor and
other microelectronic devices ( Micro) led to the development of portable
transmitters and receivers. Military applications of radio include the proximity fuse and
various types of Reconnaissance Satellites. Citizens band
(CB) radios, operating at frequencies near 27 megahertz, are used in vehicles for
communication while traveling. Also Broadcasting; Communications
- Radio Waves
- The use of electromagnetic waves in the approximate frequency
range from 10 kilocycles/second to 300,000 megacycles/second to transmit or receive
electric signals without wires connecting the points of transmission and reception.
- Radioactivity
- Radioactivity, the spontaneous disintegration or decay of the
nucleus of an atom by emission of particles, usually accompanied by . Electromagnetic Radiation. Natural radioactivity is
exhibited by several elements, including Radium and Uranium. The radiation produced is of three types: the alpha
particle, which is a nucleus (two protons and two neutrons) of an ordinary helium atom;
the beta particle, which is a high-speed electron or, in some cases, a positron (the
electron's antiparticle); and Gamma Radiation, which is a type
of electromagnetic radiation with very short wavelengths. The rate of disintegration of a
radioactive substance is commonly designated by its half-life, which is the time required
for one half of a given quantity of the substance to decay. Radioactivity may be induced
in stable elements by bombardment with particles of high energy. Also Dating;
Isotope.
- Radiometer
- An instrument for the detection or measurement of Electromagnetic Radiation, particularly Infrared Radiation. Radiometers that function by increasing the
temperature of the device are called thermal detectors; examples include the bolometer and
the Thermocouple.
- Radio Frequency Energy (RF)
- The energy transferred by electromagnetic wave in the radio
frequency spectrum.
- Radio Frequency Transmitter
- An electronic device that radiates radio frequency waves; the
device may be fixed (stationary) or mobile.
- Radium
- Radium (Ra), is a radioactive metallic element, discovered in
Pitchblende in 1898 by Pierre and Marie Curie. It is a rare, lustrous, white Alkaline-Earth Metal that resembles barium in its chemical
properties. Radium compounds are found in uranium ores. The Radioactivity
of radium and its compounds is used in the treatment of cancer. Radium compounds are mixed
with a phosphor in luminous paints. In its radioactive decay, radium emits alpha, beta,
and gamma rays and produces heat. Element; Periodic Table.
- Radon
- (Rn), gaseous radioactive element, discovered by Ernest
Rutherford in 1899. A colorless, chemically unreactive Inert Gas, it is the densest
gas known. Highly radioactive (emitting alpha rays), it is used chiefly in the treatment
of cancer by radiotherapy. In homes and other buildings in some areas of the U.S. radon
produced by the radioactive decay of uranium-238 present in soil and rock can reach levels
regarded as dangerous, but the seriousness of the problem is unclear.
- Ram
- 1.) To push into position.
- 2.) To seal a projectile in the bore of a gun.
- Rammer
- 1.) Device for driving a projectile into position in a gun. It
may be hand- or power-operated or a part of the receiver mechanism.
- 2.) Tool used to remove live projectiles from the bore of a
gun.
- Random Sample
- Sample selected without bias or prejudice.
- Range
- The difference between the smallest and largest measurements
in the sample.
- Rare Earth Oxides of the
Rare-Earth Metals
- . The name of an earth is formed from the name of its element
by replacing -um with -a. Once thought to be very scarce, they are widely distributed and
fairly abundant in the earth's crust. Rare-earth minerals include bastnasite, cerite,
euxenite, gadolinite, monazite, and samarskite. Mixed rare earths are used in glassmaking,
ceramic glazes, and glass-polishing abrasives, and as catalysts
for petroleum refining. Individual purified rare earths are used in lasers and as
color-television picture-tube phosphors.
- Rare-Earth Metals
- Group of chemical elements including those in the Lanthanide series, usually yttrium, sometimes scandium and
thorium, and rarely zirconium. Promethium, which is not found in nature, is not usually
considered a rare-earth metal. The metals occur together in minerals as their oxides Rare
Earths and are difficult to separate because of their chemical similarity. The cerium
metals are a subgroup, consisting of the elements with atomic numbers between 57 and 63
and ytterbium.
- Rarefraction
- Pertaining (among others) to the atmosphere at high altitude
or relatively low pressure pulse following a shock wave.
- Rated Maximum Pressure
- For any type gun, that value of the maximum pressure which is
specified in the propellant specification as the upper limit of average pressure which may
be developed by an acceptable propellant in the form of propelling charges which will
impart the specified muzzle velocity to the specified projectile. The smokeless propellant
in propelling charges which, in the acceptance test, develops an average maximum pressure
exceeding this value is considered as having failed to pass the test.
- RDF (Reinforced Detonating Fuse)
- Most frequently applied to reinforced MDF.
- RDX (Cyclotrimethylenetrinitramine)
- Secondary high explosive used extensively by the military.
- A high explosive compound, the term RDX originated as an
acronym for research development explosive by the U.S. military. In reality RDX is
Cyclotrimethylenetrinitramine - for short cyclonite and is expressed as the empirical
formula C3H6N6O6. Cyclonite is a colorless
crystal, with a molecular weight of 222.1, density of 1.82 g/cm3, oxygen
balance: -21.6%, nitrogen content: 37.84%, volume of detonation gases: 900 l/kg.
Detonation velocity, confined: 8,750 m/s = 28,700 ft/s at r = 1.76 g/cm3.
Critical diameter of steel sleeve test: 8mm, impact sensitivity 7.5 N m. RDX is very
stable, insoluble in water, sparingly soluble in alcohol, ether and benzene, and soluble
in acetone. Cyclohexanone, nitrobenzene and glycol are solvents at elevated temperatures.
- RDX is probably the most important high-brisance explosive;
its brisant power is owed to its high density and high detonating velocity. It is
relatively insensitive (as compared to PETN - an explosive of
similar strength). Its performance properties are only slightly inferior to those of the
homologous Octogen (HMX).
- Reaction Engine
- An engine that develops thrust by its reaction to ejection of
a substance from it; specifically, such an engine that ejects a jet or stream of gases
created by the burning of fuel within the engine.
- Recommended Firing Current (Or Energy)
- In an EED, the current (or energy) which must be applied to a
bridge circuit to cause operation within a specified time.
- Recommended Test Current (Or Energy)
- In an EED, the current (or energy) that can be applied to a
bridge circuit for extended periods without degrading the explosive material or firing
device.
- Reconnaissance Satellite
- An artificial Satellite launched
by a country to provide intelligence information on the military activities of foreign
countries. There are four major types. Early-warning satellites detect enemy missile
launchings. Nuclear-explosion detection satellites are designed to detect and identify
nuclear explosions in space. Photo-surveillance satellites provide photographs of enemy
military activities, e.g., the deployment of intercontinental ballistic missiles (ICBMs).
There are two subtypes: close-look satellites provide high-resolution photographs that are
returned to earth via a re-entry capsule, whereas area-survey satellites provide
lower-resolution photographs that are transmitted to earth via radio. Later satellites
have combined these two functions. Electronic-reconnaissance (ferret) satellites pickup
and record radio and radar transmissions while passing over a foreign country. The U.S.
and the USSR have launched numerous reconnaissance satellites since 1960.
- Rectifier
- Rectifier, component of an Electric
Circuit that changes alternating current to direct current. Rectifiers operate on
the principle that current passes through them freely in one direction, but only slightly
or not at all in the opposite direction. Also Diode; Electron Tube.
- Red Shift
- Red shift, the systematic increase in the wavelength of all
light received from a celestial object; it is observed in the shifting of individual lines
in the Spectrum of the object toward the red, or
longer-wavelength, end of the visible spectrum. Most observed red shifts are the result of
the Doppler Effect;
they are also produced by gravitation in accordance with the general theory of Relativity. Also Hubble’s Law; Quasar.
- Reflection
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Reflection, return of a wave, such
as light, from a surface it strikes into the medium through which it has traveled. The law
of reflection states that the angle of reflection (the angle between the reflected ray and
the normal, or line perpendicular, to the surface at the point of reflection) is equal to
the angle of incidence (the angle between the incident ray and the normal). Echo; Mirror; Refraction. |
- Refraction
- Refraction, the deflection of a wave on passing obliquely from
one transparent medium into a second medium in which its speed is different, as the
passage of a light ray from air into glass. The index of refraction of a transparent
medium is equal to the ratio of the speed of light in a vacuum to the speed of light in
the medium. Snell's law states that the ratio of the sine of the angle i of
incidence (angle between the incident ray and the normal, or line perpendicular to the
boundary between the two mediums at the point of refraction) to the sine of the angle r
of refraction (angle between the refracted ray and the normal) is equal to the ratio of
the refracting medium's index of refraction nr to the original medium's index of
refraction ni.
- Refractory
- Very resistant especially to high temperatures; refractive
pertains to optics.
- Regenerative Cooling
- A system for keeping liquid rocket engines cool in which one
of the liquid propellants is circulated through the engine thrust chamber walls to protect
the metal of the walls from melting under high combustion temperatures.
- Regressive Burning
- Burning of a propellant grain in such a manner that the
surface area decreases as burning progresses.
- Relative Force
- Ratio of observed maximum pressure developed by a propellant
under test to the maximum pressure developed by a standard propellant under identical test
conditions.
- Relative Strength
- The chart below is based on US military explosives used for
demolition purposes (tactical breaching is a significantly different task than military
demolition).
RELATIVE EFFECTIVENESS FACTOR OF
VARIOUS EXPLOSIVES
| Explosive Name |
Principal Use |
V.O.D. m/s f/s |
Relative Effectiveness as breaching charge (TNT=1) |
Intensity Of Poisonous Fumes |
Water Resistance |
| TNT |
Demolition charge and composition explosives |
6,900 m/s 22,600
f/s |
1.00 |
Dangerous |
Excellent |
| PETN |
Det cord, blasting caps and demolition charges |
8,300 m/s 27,200
f/s |
1.66 |
Slight |
Excellent |
| PETN |
Demolition charges as M118 block or M186 roll |
7,100 m/s 23,000
f/s |
1.14 |
Slight |
Excellent |
| RDX |
Det cord, blasting caps and demolition charges |
8,350 m/s 27,400
f/s |
1.60 |
Dangerous |
Excellent |
| RDX |
Demolition charges as M118 block or M186 roll |
7,100 m/s 23,000
f/s |
1.14 |
Dangerous |
Excellent |
| Tetryl |
Booster charge and composition explosives |
7,100 mm/s 23,300
f/s |
1.25 |
Dangerous |
Excellent |
| Tetrytol 75/25 |
Demolition charge, M2
block |
7,000 m/s 23,000
f/s |
1.20 |
Dangerous |
Excellent |
| Amatol 80/20 |
Bursting charge |
4,900 mm/s 16,000
f/s |
1.17 |
Dangerous |
Very Poor |
| Pentolite 50/50 |
Booster charge and bursting charge |
7,450 m/s 24,400
f/s |
--------------- |
Dangerous |
Excellent |
| Composition A3 |
Booster charge and bursting charge |
8,100 m/s 26,500
f/s |
--------------- |
Dangerous |
Good |
| Composition B |
Bursting charge |
7,800 m/s 25,600
f/s |
1.35 |
Dangerous |
Excellent |
| Composition C3 |
Demolition charge, M3
block |
7,625 m/s 25,000
f/s |
1.34 |
Dangerous |
Good |
| Composition C4 |
Demolition charge, M5A1 block and M112 block |
8,040 m/s 26,400
f/s |
1.34 |
Slight |
Excellent |
| Black Powder |
Time blasting fuse |
400 m/s 1,300
f/s |
0.55 |
Dangerous |
Poor |
| Ammonium Nitrate |
Demolition charge and composition explosives |
2,700 m/s 8,900
f/s |
--------------- |
Dangerous |
None |
| Ammonium Nitrate |
Demolition charge |
3,400 m/s 11,000
f/s |
0.42 |
Dangerous |
None |
| Military Dynamite, M1 |
Demolition charge |
6,100 m/s 20,000
f/s |
0.92 |
Dangerous |
Good |
| Nitroglycerine |
Commercial dynamites |
7,700 m/s 25,200
f/s |
1.50 |
Dangerous |
Good |
| Straight Dynamite (Commercial
40%) |
Demolition charge |
4,600 m/s 15,000
f/s |
0.65 |
Dangerous |
Good if fired within 24 hours |
| Straight Dynamite (Commercial
50%) |
Demolition charge |
5,500 m/s 18,000
f/s |
0.79 |
Dangerous |
Good if fired within 24 hours |
| Straight Dynamite (Commercial
60%) |
Demolition charge |
5,800 m/s 19,000
f/s |
0.83 |
Dangerous |
Good if fired within 24 hours |
| Ammonia Dynamite (Commercial
40%) |
Demolition charge |
2,700 m/s 8,900
f/s |
0.41 |
Dangerous |
Poor |
| Ammonia Dynamite (Commercial
50%) |
Demolition charge |
3,400 m/s 11,000
f/s |
0.46 |
Dangerous |
Poor |
| Ammonia Dynamite (Commercial
60%) |
Demolition charge |
3,700 m/s 12,000
f/s |
0.53 |
Dangerous |
Poor |
| Gelatine Dynamite (Commercial
40%) |
Demolition charge |
2,400 m/s 7,900
f/s |
0.42 |
Slight |
Poor |
| Gelatine Dynamite (Commercial
50%) |
Demolition charge |
2,700 m/s 8,900
f/s |
0.47 |
Slight |
Poor |
| Gelatine Dynamite (Commercial
60%) |
Demolition charge |
4,900 m/s 16,000
f/s |
0.76 |
Slight |
Poor |
| Ammonia Geletine Dynamite(Commercial 40%) |
Demolition charge |
4,900 m/s 16,000
f/s |
--------------- |
Slight |
Excellent |
| Ammonia Geletine Dynamite(Commercial 60%) |
Demolition charge |
5,700 m/s 18,700
f/s |
--------------- |
Slight |
Excellent |
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Relativity
Relativity, physical theory, introduced by Albert Einstein, that discards the
concept of absolute motion and instead treats only relative motion between two systems or
frames of reference. Space and time are no longer viewed as separate, independent entities
but rather as forming a four-dimensional continuum called Space Time. In 1905
Einstein enunciated the special relativity theory, in which the hypothesis that the laws
of nature are the same in different moving systems also applies to the propagation of
light, so that the measured speed of light is constant for all observers regardless of the
motion of the observer or of the source of light. From these hypotheses Einstein
reformulated the mathematical equations of physics. In most phenomena of ordinary
experience the results from the special theory approximate those based on Newtonian
dynamics, but the results deviate greatly for phenomena occurring at velocities
approaching the speed of light. Among the assertions and consequences of the special
theory are the propositions that the maximum velocity attainable in the universe is that
of light; that mass increases with velocity; that mass and energy are equivalent; that
objects appear to contract in the direction of motion; that the rate of a moving clock
seems to decrease as its velocity increases; that events that appear simultaneous to an
observer in one system may not appear simultaneous to an observer in another system.
Einstein expanded the special theory of relativity into a general theory (completed in
1915) that is principally concerned with the large-scale effects of Gravitation
( Also Cosmology). The general theory recognizes the equivalence of gravitational
and inertial mass, and asserts that material bodies produce the curvature of the
space-time continuum and that the path of a body is determined by this curvature. The
theory predicts that a ray of light is deflected by a gravitational field; observations of
starlight passing near the sun, first made by Arthur Eddington and colleagues
during a 1919 eclipse of the sun, confirmed this. The theory also predicts a Red Shift of spectral lines of substances in a gravitational
field, a result confirmed by observation of light from white dwarf stars. Finally, the
theory also accounts for the entire observed perihelion motion of the planet Mercury, only
part of which could be explained by Newtonian Celestial Mechanics.
Also Motion.
- Relay, (electrical)
- Material to be added.
- Relay, electromechanical
- Switch in which the variation of current in one Electric Circuit controls the flow of electricity in another
circuit. A relay consists of a movable contact connected to an Electromagnet by a
spring. When the electromagnet is energized by the controlling current, it exerts a force
on the contact that overcomes the pull of the spring and moves the contact so as to either
complete or break a circuit. When the electromagnet is de-energized, the contact returns
to its original position.
- Relay, (explosive)
- An element of a fuze explosive train which augments an outside
and otherwise inadequate output of a prior explosive component so as to reliably initiate
a succeeding train component. Relays, in general, contain a small single explosive charge
such as lead azide and are not usually employed to initiate high explosive charges.
- Reliability
- A statistical evaluation of the probability of a device
performing its design function.
- Remaining Velocity
- Speed of a projectile at any point along its path of flight.
Remaining velocity is usually measured in feet per second.
- Remover
- An explosive telescoping device designed to remove a canopy
from an aircraft.
- Resin
- Resin, any of a class of amorphous solids or semisolids.
Natural resins occur as plant exudations (e.g., of pines and firs), and are also obtained
from certain scale insects. They are typically yellow to brown in color, tasteless, and
translucent or transparent. Oleoresins contain essential oils and are often sticky or
plastic; other resins are exceedingly hard, brittle, and resistant to most solvents.
Resins are used in varnish, shellac, and lacquer and in medicine. Synthetic resins, e.g.,
bakerlite, are widely used in making Plastics.
- Resistance
- The property of an electric conductor by which it opposes flow
of electricity and dissipates electrical energy away from the Electric
Circuit, usually as heat. Resistance is basically the same for alternating- and
direct-current circuits. A high-frequency alternating current, however, tends to travel
near the surface of a conductor. Because such a current uses less of the available cross
section of the conductor, it meets with more resistance than direct current. The unit of
resistance is the OHM. Also Conduction; Impedance; OHM’s Law; Superconductivity.
Resistance Of Copper & Iron Wire Ohms / 1000’
of wire
| AWG |
Copper |
Iron |
| #6 |
0.395 |
1.4 |
| #8 |
0.628 |
3.7 |
| #10 |
0.999 |
6.1 |
| #12 |
1.590 |
9.8 |
| #14 |
2.530 |
15.6 |
| #16 |
4.020 |
24.8 |
| #18 |
6.380 |
39.5 |
| #20 |
10.150 |
62.7 |
| #21 |
12.800 |
76.1 |
| #22 |
16.140 |
100.0 |
| #23 |
20.360 |
126.0 |
| #24 |
25.670 |
159.0 |
- Resistor
- Resistor, two-terminal Electric
Circuit component that generates heat by offering opposition to an electric
current. The most common forms of resistors are made from fine wires of special alloys
wound onto cylindrical forms or from a molded composition material containing carbon and
other substances in varying amounts. Resistors are rated for the maximum amount of power
that they can safely handle.
- Restricted Burning Grain
- A solid propellant grain in which certain surfaces are
restricted or inhibited to provide particular burning characteristics.
- Restricted Burning Rate
- A solid propellant grain in which certain surfaces are
restricted or inhibited to provide particular burning characteristics.
- Retrofit
- A partial change in older equipment.
- Retrorocket
- A rocket fired in a direction opposite to the line of flight
of the vehicle to which it is attached.
- Ricochet
- Glancing rebound of a projectile after impact.
- Rifle
- 1.) Any firearm that has rifling in the bore designed to give
a spin to the projectile for greater accuracy of fire and longer range (not extensively
used in this manner, except for shoulder arms).
- 2.) To cut spiral grooves (rifling) in the bore of a gun in
order to give a spin to the projectile so that it will have a greater accuracy of fire and
longer range.
- Rifling
- Spiral grooves in the bore of a weapon designed to give a spin
to the projectile for greater accuracy. Rifling includes both the grooves and the ridges
between, called lands.
- Rocket
- A missile containing combustibles, independent of atmospheric
oxygen, which on being ignited, liberate gases producing thrust.
- Rocket Propellant
- Any agency used for consumption or combustion in a rocket and
from which the rocket derives its thrust, such as a fuel oxidizer, additive, catalyst, or any compound or mixture of these. "Rocket
propellant" is often shortened to "propellant."
- Roll
- The rolling of a launch vehicle about its axis as the vehicle
continues on its flight path.
- Rope (as it pertains to ballistics)
- Electromagnetic wave reflectors consisting of long strips of
metal foil. Similar to window or chaff, but longer. Dropped from planes or shot into the
air in projectile, a small parachute or other device may be attached to each strip to
reduce rate of fall.
- Rotating Band
- Soft metal band around a projectile near its base. The
rotating band makes the projectile fit tightly in the bore by centering the projectile,
thus preventing escape of gas and giving the projectile its spin as it engages in the
rifling.
- Round
- 1.) All the parts that make up the ammunition necessary in
firing one shot (also called Complete Round).
- 2.) One shot fired by a weapon.
- Round Of Ammunition
- Round.
- Rubber
- Rubber, any solid substance, usually elastic, that can be
vulcanized to improve its elasticity and add strength; the term includes natural rubber,
or caoutchouc, and a wide variety of synthetic rubbers, which have similar properties.
Rubbers are composed chiefly of Carbonand Hydrogen, but some
synthetics also have other elements, e.g., chlorine, fluorine, nitrogen, or silicon. All
are compounds of high molecular weight; each consists of a
series of one kind of molecule (e.g., isoprene in natural rubber) hooked together in a
long chain to form a very flexible, larger molecule, the Polymer. Natural
rubber is obtained as latex, a milky suspension of rubber globules found in a large
variety of plants, chiefly tropical and subtropical. An important source is the Para
Rubber Tree. Latex can be shipped for processing either as a liquid or coagulated by
acid and rolled into sheets. For most purposes rubber is ground, dissolved in a solvent,
and compounded with other ingredients, e.g., fillers, Pigments, and plasticizers.
Known by pre-Columbian Indians of South and Central America, rubber first attracted
interest in Europe in the 18th cent. Vulcanization, a process invented (1839) by Charles
Goodyear revolutionized the rubber industry. It usually involves heating raw or compounded
rubber with Sulfur, causing sulfur bridges to form between molecules. The product
is nonsticky, elastic, and resistant to heat and cold. Natural rubber is used chiefly to
make tires and inner tubes because it is cheaper than synthetic rubber and has greater
resistance to tearing when hot. Natural rubber can be treated to make foam rubber and
sponge rubber. The first synthetic rubber was made in Germany in World War I. Today
synthetics, e.g., Buna S, neoprene, butyl, and nitrile, account for most of the world's
rubber production. Made from Coal, Petroleum, Natural Gas, and Acetylene, synthetic
rubbers are resilient over a wider temperature range than natural rubber and are more
resistant to aging, weathering, and attack by certain substances, notably, oil, solvents,
oxygen, and ozone. Silicone rubbers are used in insulation. Polyurethanes are
used in tires, in shoes, and as foams. Neoprene is used for making hose and tank linings.
Butyl rubber is used in inner tubes and as insulation.
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