Добавил:
ivanov666
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Materials processing and manufacturing technologies. Учебное пособие
.pdf
61
pellets or granules, consisting of solid particles. The injection
molding process of polyurethanes, epoxies, polyesters and nylons
under pressure is considered to be the most efficient for high-speed
molding of plastics. Due to this technique, it is possible to mold
several parts simultaneously. The method does not impose higher
requirements for postforming operations. Another important
advantage of the method is high production speed.
Extrusion process includes fluidization and homogenization
of plastic granules or pellets. During all the process they are
continuously formed. Pipes, sheets, wires, profile shapes, substrate
coatings and tubing are produced in this way.
Blow molding. This process results in forming a hollow object
with a definite size and shape. Firstly, a tube (called a parison) is
formed. Secondly, air or other gas is blown to cause the tube to
expand.
Thermoforming is the process under the effects of heat and
pressure to form plastics sheets.
Rotational molding. It is the process of thermal melting or
fusing finely ground powders in rotating moulds. The term “slush
molding” is applied to liquid materials molding. The melted or
fused resin uniformly coats the inner surface of the mould. When
cooled, a hollow finished part is removed.
Compression and transfer molding. Plastics powder or plug
is charged into a mould cavity. A mating mould half is closed. The
process of plastics shaping which matches the cavity shape, occurs
due to applying pressure for compression, heat, and cause flow of
the plastics.
Foam processes. The use of foamed plastics materials in
industry is constantly growing thank to their good physical and
chemical properties. Foams can be made in a range from soft and
flexible to hard and rigid. There are three types of cellular plastics:
blown, syntactic and structural.
62
Reinforced plastics/composites fabrication procedure. The
more generalized resins and reinforcements are called composites.
Their mechanical properties are significantly improved because of
the inclusion of fibrous reinforcements.
Casting and encapsulation. Casting of plastic materials
occurs at low-pressure. The process requires nothing more than a
container of the desired shape. Encapsulation means the precision
plastic injection molding process, where one material is molded
over another one.
Calendering. The process starts when plastic is masticated
between two rolls. These rolls then squeeze it out into a film. One
or several additional rolls are sometimes necessary. The film passes
around before being stripped off as a continuous film. The latter
rolls are used for paper or fabric in order to impregnate them with
the plastic.
Task 1. Choose the correct word(s) in each sentence.
1. Additives/binders added to plastic materials influence their
properties.
2. Injection molding process consists of heating/cooling and
homogenizing plastic granules in a cylinder until they are
sufficiently hard/fluid.
3. The main raw material for injection moldable plastics is
solid/soft particles, in the form of pellets or granules.
4. The major advantages/disadvantages of the injection-
molding process are the speed of production, and minimal
requirements for postmolding operations.
5. Extrusion can result in the highest/lowest output rate of any
plastics/ceramics processes.
63
6. Thermoforming is the forming of plastics sheets into parts
through the application of cold/heat and pressure/splitting.
7. Foams can be made in a range from liquid/soft and flexible
to hard and rigid/fluid.
8. There are three types of cellular plastics: brown/blown,
syntactic/natural, and inorganic/structural.
9. Casting is a low-pressure/high-pressure process.
Task 2. Match the words (1–8) with their definitions (A–H).
1 – polymer
3 – composite
5 – compression
7 – foam
2 – plastics
4 – casting
6 – encapsulation
8 – moulding
A: a manufacturing process in which a liquid material is
usually poured into a mould, which contains a hollow
cavity of the desired shape, and then allowed to solidify.
B: a wide range of synthetic or semi-synthetic materials that
use polymers as a main ingredient.
C: dipping a material into a resin system where a thick coating
completely surrounds the unit.
D: forming an object out of malleable material.
E: a class of natural or synthetic substances composed of very
large molecules, called macromolecules, that are multiples
of simpler chemical units called monomers.
F: a decrease in volume of any object or substance resulting
from applied stress.
64
G: a material formed by trapping pockets of gas in a liquid
o solid.
H: a material which is produced from two or more constituent
materials.
Task 3. Match the type of processing in English with its Russian
translation.
1. Injection Moulding
a) изготовление
армированного пластика
2. Extrusion
b) горячее формование
3. Blow Moulding
c) процесс вспенивания
4. Thermoforming
d) литье с раздувом
5. Rotational Moulding
e) литье под давлением
6. Compression Moulding
f) формование прессованием
7. Foam Process
g) капсулирование
8. Reinforced Plastic
Fabrication
h) литье
9. Casting
i) непрерывное профильное
прессование
10. Encapsulation
j) изготовление пленочного
или листового материала
11. Calendaring
k) центробежное формование
65
Task 4. Read the journal article. Then, choose the correct
answers.
BUILDING WITH THE TIMES
Fig. 14. Types of modern plastics
Many designers prefer traditional building materials. They
choose wood and metal instead of plastics. This was once
reasonable, since early plastics were often brittle. However, today’s
technology makes plastics both durable and flexible. A wise
architect understands the benefits of building with plastics.
Some plastics are opaque and others are transparent. That
means some can be used to construct walls and others can be used
to make windows. Plastics also vary in hardness. Rigid plastics
create strong solid structures. More elastic products make excellent
insulators and sealants.
Plastics are also easy to work with because they are often
lightweight. However, they are often stronger than many other
heavy materials.
66
1. What is the article mainly about?
A – Advantages of building with new types of structural
materials.
B – Methods of building with traditional materials.
C – Processes for manufacturing different building materials.
D – Advertisement for available building materials from
a famous company.
2. Which of the following is NOT a feature of plastics?
A – They come in different degrees of hardness.
B – They are made into flexible sealants.
C – They can be used to create windows.
D – They are usually heavier than other building materials.
3. According to the article, what is true about older plastics?
A – They were usually transparent.
B – They were more flexible than today’s plastics.
C – They were sometimes brittle.
D – They were more popular than wood and metal.
67
Text 8. Read the text.
INNOVATIVE BUILDING MATERIALS
AND TECHNOLOGIES
Fig. 15. Innovative building materials
Over the ages, the construction industry has continuously had
a series of innovations. We can see how technological advancements
have impacted the construction industry, from durable concrete used
in ancient structures to steel used in bridges and skyscrapers. Some
materials evolve with time, but others are new to the industry.
The production of building and finishing materials is constantly
developing. In a competitive environment, different manufacturers
68
offer new solutions and patent innovative developments that are
aimed at improving the appearance and properties of materials, as
well as creating unique product.
Some of the emerging innovative building materials are
presented in this text.
Self-healing concrete. Specialists
from Holland have developed an
amazing technology for concrete
restoring without human intervention.
Thanks to this technology calcium
lactate is added into the composition of
the concrete, and then live bacteria
feeding this additive, are introduced.
These microorganisms close up cracks
and cavities when processing it into
limestone. The invention makes it
possible to abandon repair work.
Transparent concrete (litracon)
is a fairly new material, appeared in
2005. It has already gained popularity in
the building materials market due to its
strength and water resistance. This
composite material consists of a mixture
of cement mortar and glass fiber optic
strands that transmit light. It is widely
used for the construction of ultramodern buildings, basements, mansard
roofs and facades with internal
illumination, fences, etc. Transparent
concrete does not absorb moisture and does not collapse at low
temperatures.
Fig. 16. Self-healing concrete
Fig. 17. Transparent concrete
69
Ceramic bricks are obtained in
various ways: by plastic molding, dry
pressing, firing with the addition of
sawdust, etc. Various properties of
bricks such as porosity, frost resistance,
and moisture resistance are achieved
due to these techniques. The material is
characterized by high strength, frost
resistance, it does not crack when
exposed to temperature changes. It is
used in the construction of internal
walls and load-bearing structures.
Glass tile is a unique building
material for the roofing of buildings. It
is equipped with built-in photocells
that accumulate the energy of sunlight.
This tile is made of tempered impactresistant glass; therefore, it is not
inferior in strength to traditional
ceramic counterparts.
Flexible ceramic tile is
a composite product called Flexi Clay,
made from traditional clay, where
a plasticizer, giving the product
elasticity, is added. Durable fiberglass
is used for reinforcement. The novelty
can be used for both interior and
exterior decoration. Flexible tiles can
be bent at right angles without risk of
cracking. Its average service life is
about 20 years.
Fig. 18. Ceramic brick
Fig. 19. Glass tile
Fig. 20. Flexible ceramic tile
70
Smart glass is referred to another
new technology used in construction
for the production of windows, glass
doors and partitions. Its main
advantage is the ability to change
optical characteristics (heat absorption,
haze, light transmission) under the
influence of environmental conditions.
This category also includes selfcleaning, self-heating and automatically
opening windows. Thanks to their use,
it is possible to reduce heat loss, reduce
the cost of air conditioning, and even replace the usual curtains
and blinds.
Flexible stone is one of the
modern finishing technologies, which
belongs to a type of wallpaper and
imitates the structure and color of
different types of stone (sandstone,
slate, clinker bricks, etc.). It is made on
the basis of sandstone and an ecofriendly polymer, due to which the new
material is flexible, durable, light and
easy to use. The flexible stone has
a thickness of 1.5–3 mm and is applied
in stripes to the walls, previously coated
with an adhesive, after which all joints are rubbed. It is resistant to
abrasion and fading, therefore it is suitable for finishing any
premises and parts of the house (bathrooms, kitchens, saunas, pools,
fireplaces).
Fig. 21. Smart glass
Fig. 22. Flexible stone
Соседние файлы в предмете [НЕСОРТИРОВАННОЕ]