Ingineria Designului de Produs (lb. eng.) [610054]

PROIECT DE DIPLOMĂ

Absolvent: [anonimizat] :
Ingineria Designului de Pr odus

Conducător științific:
conf.dr. Cristina CAZAN

Brașov
2017
Universitatea Transilvania din Brașov
FACULTATEA DE DESIGN DE PRODUS ȘI MEDIU

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CLAUDIA CRISTEA

REC ICLAREA MODULELOR PV SUB FORMA DE MATERIALE
COMPOZITE CU APLICABILITATE IN DOMENIU
CONSTRUCTIILOR

PROIECT DE DIPLOMĂ

Program studii:

Ingineria Designului de Produs (lb. eng.)

Brașov
2017

UNIVERSITATEA TRANSILVANIA DIN BRAȘOV
Facultatea Design de Produs si Mediu
Departamentul Design de Produs, Mecatronica si Mediu

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Abstract

Ever increasing amounts of plastics are being produced and used during the last decade and
today. A tendency that will only continue to manifest itself even m ore and more in the following
years, this due to the development of new technologies and the widespread use of plastics in a
wide range of applications. Waste management and recycling after the life -cycle of plastic
products is both environmentally and fin ancially interesting.

In the research done, novel composite materials were created fully based on recycled waste
materials. Polypropylene (PP) , high density polyethylene ( HDPE ) and polystyrene (PS) were
combined in different compositions and the composit es were tested to discover if these materials
have sufficient properties to be used in construction applications.

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Introduction
Pollution caused by waste materials, and in specific plastics and rubber, is getting an ever
growing problem in t he world of today. Last decades the production and consumption of these
materials increased immensely, and this trend is not unlikely going to change. It’s almost nearly
impossible to avoid the use of these materials, because they play a big role in the de velopment
and creation of new technologies. Decent and realistic solutions need to be found for the problem
of the ever growing use of plastics. In particular better ways of recycling the plastics and finding
better ways , to sustain the properties of the r eused material in comparison with the virgin
material.

Due to the characteristics of plastic materials, waste coming from these materials has a long life
span, which makes it virtually impossible to let them degenerate by themselves. Due to their
composi tion of large molecules, decomposition takes a very long time. Basically this means that
every plastic material that was ever produced, still exists today. Which proposes lots of problems
in terms of waste management and also imposes an economical deficit . Once produced and
deposed, most of these materials don’t have any economic value anymore.
An example of this problem is easily seen in the Pacific Ocean, due to ocean currents and tides,
plastic waste, other garbage and smaller plastic particles are gat hered together in patches. The
Great Pacific garbage patch is one of the biggest waste patches, where tremendous amounts of
plastic waste and particles are floating in the upper parts of the ocean.

However, thanks to recycling these materials, this waste can be reused and thus again gain an
economic value and return in the manufacturing cycle as a material of resource. Due to rising
depletion of resources, bigger companies started to see the economic value of the waste and thus
the search for ways of usin g this waste as recourse started. Nowadays a big fraction of used
plastics are recycled, although the biggest part is still left as a waste product. Due to difficulties
to conserve the material’s characteristics during the process of recycling, most materi als have
less good quality then desired. For example the mechanical properties of a recycled material are

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different from those of the corresponding original material.

The goal of this paper and the research done is to find an optimum point where the prop erties of
the recycled material are sufficient enough to be used again as construction materials and thus
can be used as if they were original materials. This point was determined by experimentation on
different combinations of recycled materials and by va rying the ratio of the materials used in the
blend.

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1. Plastics
1.1 Signification of plastics
“Plastic” is a generic term for numerous materials that differ in structure, properties, and
composition. The properties of plastics vary so widely that they are often used to replace
conventional materials, such as wood or metal.
Definition of plastics:
Plastics are materials whose essential components consist of macromolecular organic
compounds. These compounds are created synthetically or by conven tion of natural products. [1]
1.2 Composition of plastics
The basic substance for polymers are called “monomers” (mono=single, meros= part) (Fig.1) .
The term “macromolecule” is derived from the large size of these molecules (macro=large).
These large molecules re sults from the combination of many thousands of monomer molecules.
(Fig.2)

Fig. 1 Schematic monomer molecule [1]

Fig. 2 Macromolecule (chain elements) [1]

Macromolecules are formed from many identical monomers in the simple case; they consist of a
sequence o f identical chain elements. Each chain molecules has a continuous line of chain
elements.

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The basic materials for the monomers are primarily crude oil and natural gas. Because carbon is
the only element essential for polymers, it is theoretically possible to create monomers from
wood, coal. But these substances are not used because it is inexpensive to produce monomers
from gas and oil.

1.3 Raw material for plastics

In the production of plastics are natural substances, such as cellulose, coal, petroleum, and
natural gas. The molecules of the raw materials have in composition carbon (C) and hydrogen
(H). Also in the composition of materials can be involved oxygen (O), nitrogen (N) and sulfur
(S). But the most important material for plastics is petroleum. Fig.3

Fig. 3 Properties of the various products made from petroleum as percentag es of total
production

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1.4 Properties of polymers

Plastics and natural materials such as rubber or cellulose are composed of very large molecules
called polymers . Polymers are con structed from relatively small molecular fragments known as
monomers that are joined together.

Wool, cotton, silk, wood and leather are examples of natural polymers that have been known and
used since ancient times. This group includes biopolymers such as proteins and carbohydrates
that are constituents of all living organisms.

Synthetic polymers, which include the large group known as plastics , came into prominence in
the early twentieth century. Chemists' ability to engineer them to yield a desired set of properties
(strength, stiffness, density, heat resistance, electrical conductivity) has greatly expanded the
many roles they play in the modern industrial economy.

Let's begin by looking at an artificial polymer that is known to everyone in the form of flexible,
transparent plastic bags : polyethylene . It is also the simplest polymer, consisting of random –
length (but generally very long) chains made up of two -carbon units. Fig. 4

Fig.4 Structure of polyethylene [2]

You will notice some "fuzziness" i n the way that the polyethylene structures are represented
above , Fig.4. The squiggly lines at the ends of the long structure indicate that the same pattern

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extends indefinitely. The more compact notation on the right shows the minimal repeating unit
enclo sed in brackets overprinted with a dash; this means the same thing and is the preferred way
of depicting polymer structures.

Classification of polymers
Polymers can be classified in ways that reflect their chemical makeup, or perhaps more
importantly, th eir properties.

Chemistry:
 Nature of the monomeric units
 Average chain length and molecular weight
 Homopolymers (one kind of monomeric unit) or copolymers ;
 Chain topology: how the monomeric units are connected
 Presence or absence of cross -branching
 Metho d of polymerization
Properties:
 Density
 Thermal properties — can they soften or melt when heated?
 Electrical conductivity
 Degree of crystallinity
 Physical properties such as hardness, strength.
 Solubility, permeability to gases

Mechanical properties of p olymers
Polymers possess a wide range of mechanical behaviors and can be: strong, weak, f ragile, ductile
or combinations (fig.5)

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Fig. 5 Examples of variation of tension curves – deformation of polymers [3]

The mechanical properties for the composition of a particular polymer strongly depend on the
degree of crystall inity and the molecular weight (fig.6) .

Fig. 6 Effect of molecular weight and degree of crystallinity in the mechanical behavior of
polymers [3]

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These properties affect, in particular, the rigidity of the pine chain breaking. The short chains
present in the mass of the polymer can act as plasticizers for the molecular weight distribution
and facilitate the movement of the chains. They interact with efficient packaging of long chain
molecules.

Appl ications :
 molded and formed objects ("plastics")
 sheets and films
 elastomers (i.e., elastic polymers such as rubber)
 adhesives
 coatings, paints, inks
 fibre and yarns

Physical properties of polymers:
The physical properties of a polymer such as its streng th and flexibility depend on:
 chain length – in general, the longer the chains the stronger the polymer;
 side groups – polar side groups (including those that lead to hydrogen bonding) give
stronger attraction between polymer chains, making the polymer str onger;
 branching – straight, unbranched chains can pack together more closely than highly
branched chains, giving polymers that have higher density, are more crystalline and
therefore stronger;
 Cross -linking – if polymer chains are linked together extensive ly by covalent bonds, the
polymer is harder and more difficult to melt.

Crystalline and amorphous polymers
In a polymer the molecules are chains containing potentially millions of formula units. There is,
however a repeating unit in a polymer – the monome r from which it was made. This must be the
basis of both long and short -range order in a polymeric material.
For example, a short section of linear polyethylene it’s represented in fig.7

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Fig. 7 Section of linear polyethylene [4]

However, the conformat ion of the bonds around each carbon atom can be repre sented
schematically as follows in fig.8

Fig. 8 Newman projections [5]

These diagrams are called Newman projections. The circle is a single C -H bond; and this
diagram represents a projection along it. The se two structures thus represent one half of the
backbone continuing on either side of a C -C bond (trans), or both halves on the same side
(gauche). Note that there are two possible gauche states, labelled gauche ( -) and gauche (+).
Whilst the trans confor mation has a lower energy (since it's easier to position the hydrogen atoms
on the carbon backbone further apart), an all -trans conformation would be a considerably more
ordered structure than a random one – that is, it has a much lower entropy.

Amorphou s polymers are generally found in a random coil conformation and have a disordered
chain structure fig.9. This is the most common structure of many polymers. Crystalline polymers
are predominantly in the all -trans conformation, and the chains are arranged in lamellae, as
below :

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Fig. 9 Common structure of polymers [5]

The polymer crystal is made up from one -dimensional chain -folded sequences, shown on the
above left, where the repeat distance is given by the chain spacing. T o the above right is shown a
schematic arrangement of folded chains into a two -dimensional lamella.

An amorphous polymer has the maximum entropy conformation (given by the Boltzmann
distribution), and the chains are arrayed randomly throughout the materia l, making atomic
positions quasi -random as in any other glassy material.

As a result of the difference between the amorphous and crystalline arrangements of polymer
chains, the X -ray diffraction patterns of the two phases are very different. The amorphou s phase
contains no long -range order, meaning that there are no regular crystalline planes to diffract X –
rays. Thus the incident X -rays are scattered randomly and there are no sharp peaks in the
diffraction pattern. In the crystalline phase, the repeating lamellar chains provide a regular
structure, thus the diffraction pattern will contain sharp, prominent signature peaks, the position
of which depends on the exact spacing between chains. As the degree of crystallinity of a
polymer affects its properties, accurately determining it is important. X -ray diffraction can be
used to determine the degree of crystallinity of a sample. Thermal analysis techniques such as
differential scanning calorime try (DSC) can also be used. The two determinations may not
necessarily be in agreement, and the reasons for this are complex. [5]

Thermal Properties of Polymers
Thermoplastics:
Plastics consisting of macromolecules with linear or branched chains held togethe r by
intermolecular forces are called ‘thermoplastics”. The strength of the intermolecular forces
depends on the type and number of branches or side chains, among other facts.

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A thermoplastic polymer is a type of plastic that changes properties when heated and cooled.
Thermoplastics become soft when heat is applied and have a smooth, hard finish when cooled.
There are a wide range of available thermoplastic formulas that have been created for many
different applications. To produce composite materials using thermoplastics, high pressures and
temperatures are necessary.

Fig. 10 Structure of amorphous and semicrystalline thermoplastics [1]

Thermosets:
Thermosetting resins (in short: thermosets) do not melt on heating, but ultimately disintegrate.
From a molec ular point of view, most thermosets consist of relatively short chains ensuring the
non-cured polymers to have very low viscosity. Curing is carried out by initiating a chemical
reaction, in which the short chains form bonds and create a three -dimensional ‘cross -linked’
network. The temperature is often regulated during curing.

Glass transition temperature (T g)
The glass transition temperature (Tg) is the temperature at which a resin passes from the 'glassy'
state (rigid and brittle, i.e. little plastic de formation at fracture) to the 'rubbery' state (slack and
tough). It is not recommended to use a composite in the vicinity of or above this temperature.
The effect of exceeding the glass transition temperature is much stronger with thermoplastics
than with thermosets, but is reduced for both by the reinforcing material. The glass transition

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temperature depends on the circumstances during curing (for thermosets). A higher glass
transition temperature can be achieved by curing at higher temperatures and with l onger periods
of heating.

Thermal behavior of polymers :
Polymers are characterized by two important temperatures:
 The melting temperature – at which the transition between the solid polymer and the
liquid occurs.
 The glass transition temperature – at whic h transition occurs between regions where the
polymer is relatively rigid (under Tg) and those in which it is relatively similar to rubber /
plasticized (over T g).
This temperature is also affected by the molecular weight of the polymer mass fig.11

Fig. 11 Effect of molecular weight on melting and glass transition temperature [3]

1.5 Life cycle of a product

According to the World Commission on Environment and Development (WCED), sustainable
development is : "development that meets the needs of the present witho ut compromising the
ability of future generations to meet their needs" .
From the designer point of view, the significance of the concept of sustainable development is to
design products using less resources Fig.12 . Sustainable development has 3 components :
economic, ecological and social .

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Fig. 12 Consumption of renewable resources

A product system goes through a number of consecutive and interlinked stages potentially
ecologically dangerous Fig.13. These stages are called "Life -cycle of a Product" becau se a
product has a life that starts from " raw material acquisition or generation of natural resources,
over manufacture, transport, and use to the final disposal

Fig. 13 Life cycle of a product

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A product has a life that starts with the raw materials extr action, passes through the
manufacturing process and assembly, the purchase of the complete product (including
transportation, packaging, advertising etc.), the use or consumption and the end-of-life. Finally
the product can be ‘reborn’ by reus e or recycli ng the materials and so the circle is closed forming
the so called Life Cycle .

All the stages of the product Life -Cycle are potentially dangerous for the environment. LCA is
the abbreviation for the Life-Cycle Assessment which represents the evaluation of the
environmental impact during all stages of the Life Cycle of a product.

The materials used for eco -products:
 Should come from renewable/sustainable sources;
 Their environmental impact during extraction, transportation and processing should be
reduced;
 Must not be hazardous for humans and environment (both as a product or waste);
 Must permit recycling.

A clean technology /process responds to human needs (connecting it with sustainable design):
 Avoids waste (efficient use of materials);
 Minimises emiss ions;
 Ensures an efficient use of energy.

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2. Recycling
2.1 Meaning of recycling:

Recycling means the process of converting waste materials into new materials and objects in
order to save materials and help lower greenhouse gas emission. By recycling we can pr event the
waste of potentially useful materials and reduce the consumption of fresh raw materials, thereby
reducing the energy usage, air and water pollution.

2.2 WASTE MANAGEMENT

In Romania, the Ministry of Environment and Forests promoted public intere st documents, such
as eco -guide public official Eco -tourist guide and guide eco -citizen, containing recommendations
on:
 Energy consumption reduction and energy waste and waste material avoidance, applied
to both institutions and citizens;
 Separate collec tion of all types of waste, especially Waste Electrical and Electronic;
 Limiting environmental pollution through voluntary actions for waste management,
reducing resource consumption, using biodegradable materials, the practice of
responsible eco -tourism activities as against nature;

Basic principles of environmental policy in Romania are set in accordance with European and
international provisions, ensuring protection and nature conservation, biological diversity and
sustainable use of its components.

Currently, the waste hierarchy shall apply as a priority order, in four steps to according Directive
2006/12/CEE, but by the end of 2010, following the transposition of the new waste directive
2008/98/CEE there will be applied the five -step waste hierarchy: prevention, preparation for
reuse, recycling, other recovery and disposal operations.

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According to the legislation in force, the waste producers have the responsibility management of
waste including waste prevention, recycling, and dis posal. In 2007, ove r 419,000 tones of
hazardous waste were generated; representing a 0.15 % of total of generated waste Tab.1 . Most
of this hazardous waste was co -incineration or incineration in the producer own facilities or
private operators’ facilities, or landfilled. [6]

In the Tab. 1, 2, 3 and the F ig.14, 15, 16 are represented the total waste management in R omania
for a period of 5 years (2003 -2007)

Table 1 Management of hazardous industrial waste, 2003 -2007 [6]
YEAR Total of produced
hazardous industrial
waste Total of recovered
hazardous industrial waste Total of disposed
hazardous industrial waste
2003 730226 461628 514004
2004 1048400 2218000 7244000
2005 736787 458508 461668
2006 555227 337149 410787
2007 407837 406450 149824

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Fig. 14 Management of hazardo us industrial waste, 2003 -2007 [6]
Table 2 Management of non -hazardous industrial waste, 2003 -2007 [6]

Fig. 15 Management of non -hazardous industrial waste, 2003 -2007 [6]

Table 3 Management of municipal waste, 2003 -2007 [6]

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Fig.16 Management of municipal waste, 2003 -2007[ 6]

2.3 Recycling of materials

Process of recycling :
The first step in recycling is to decide to recycle. The next step is to make sure the items are
recycled correctly.
Focusing on plastic materials we have to know what do the sy mbols on the bottom of plastic
bottles and containers mean Tab.4 . The resin number is contained in a triangle Fig.17.

Table 4 Resin identification code [2]
SPI Resin Identification Code 1 2 3 4 5 6 7
Type of Resin Content PET HDPE Vinyl LDPE PP PS OTHE R
 PET – Polyethylene
Terephthalate
 HDPE -High -density
Polyethylene  LDPE – Low-density
Polyethylene
 PP – Polypropylene
 PS – Polystyrene
 Other – Mixed Plastics

*society of the plastic industry

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Fig. 17 Plastic symbols with resin identification cod [7]

2.4 What can recycled material become:
HDPE: using raw resources we can save landfill space, energy, water, resources, and reduces
pollution. Some of the products that can be made from recycling HDPE ( Fig.18 ):
 Crates
 Film plastic and sheeting
 Floor tiles
 Gardening tools, flower pots, and hardscape materials
 Non-food bottles – shampoo, conditioner, cleaning products, laundry cleaners, motor oil,
antifreeze
 Pipe
 Plastic lumber – used for playgrounds, outdoor patios, picnic tables, etc.
 Recycling bins[4]

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Fig. 18 HDPE transformation after recycling [8]

PP: Some of the products that can be made from recycling PP plastic:
 Auto parts – battery cases, signal lights, battery cables
 Bike racks
 Brooms and brushes
 Film sheeting
 Garden rakes
 Ice scrapers
 Plastic trays
 Shipping containers and pallets
 Storage bins

PS: Some of the products that can be made from recycling PS plastic:
 Casings for electronics – cameras, video cassettes
 Desk trays
 Foodservice items – foamed egg cartons
 License plate frames
 Light switch plates
 Packaging material – expandable polystyrene foam (EPS)
 Plastic mouldings – architectural
 Rulers
 Thermal insulation

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 Thermometers
 Vents

Properties of the chosen materials:
In this table will find further information about the chosen materials (HDPE, PP, PS ) Tab.5.

Table 5 Properties of chosen materials
Polyethylene
high density (HDPE) Polypropylene
(PP) different grades Polystyrene
(PS)
Formula –(CH 2-CH 2)n– –[CH 2-CH(CH 3)]n– –[CH 2-CH(C 6H5)]n–
Structure

Tg (șC) _100 _10 90
Densities g/cm3 0.93 to 0.97 0.90-0.99 0.96–1.04 g/cm3
Young’s modulus (E)
[N/mm2] 0.8 1.5-2 3-3.5
After recycling process this materials HDPE, PP, PS will be the main components for the
composite materials.

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3. Composite materials
3.1 Signification of composite materials:

A co mposite material is a combination of two or more materials of the same type or different
from a physical and chemical point of view. The two materials work together to give the
composite unique properties.
Composite materials have been designed to replace, in a growing proportion, traditional ferrous
and non -ferrous materials.

Attempts to achieve new super -performance materials have led to the development of a class
known as commodities called Composite Materials. By definition, the concept of "composite" is
attributed to a complex system, made up of several materials of a different nature. In this
category comes a very large class of products. This is due to the fact that the possibilities of
changing the fundamental components, of the "assembly" and manuf acturing techniques, the
level of performance and cost are practically infinite.

From a technical point of view, the notion of composite materials refers to materials possessing
the following properties:
 Are artificially created by combining different com ponents
 Is a combination of at least two chemically distinct materials
 Presents properties that no separate components can have

Advantages and disadvantages:
In addition, it is necessary to know both the advantages and disadvantages of a material. The
table below resumes a number of these possible pros and cons. Tab.6

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Table 6 Advantages and disadvantages of composite materials
Advantages Disadvantages
Weight saving High material costs
High degree of freedom in form, material and
process Sophisticate d computational methods
sometimes required
Easy to color Colo r and gloss preservation not always
predictable
Translucent Relatively limited kno wledge on structural
behavio r of details and connection methods
High degree of integration of functions
possib le Finishing not yet well developed
Strength, stiffness, thermal and electrical
resistance can be designed Stiffness and failure behavio r can be
undesirable; sensitive to temperature, fire and
lightning strike
Low total maintenance costs High costs of raw materials
Water – and chemically resistant Sensitive to UV light
Use of durable materials possible Recycling not yet well developed
Automated manufacturing possible Sometimes capital intensive production
methods (e.g. automated methods)

In the above table are mentioned general advantages and disadvantages, but we have to make
distinction in the design process because some characteristics are not applicable or they aren’t
incompatible in some case. Changes could appear in the weight of the produc t. Furthermore,
costs and sustainability of a design should always be considered throughout the life cycle. The
costs of components or life -cycle phases can soar (e.g. investments in a mould) or materials may
not be sustainable. [9]

The number of advantages a nd disadvantages don’t have a powerful impact on the perception of
man, the biggest defining impact for the humans is given by the design of the object that can be a
grate, success or not.

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3.2 Structure of composite materials, classification:

A composite , in the present context, is a multiphase material that is artificially made, as opposed
to one that occurs or forms naturally. In addition, the constituent phases must be chemically
dissimilar and separated by a distinct interface. Thus, most metallic all oys and many ceramics do
not fit this definition because their multiple phases are formed as a consequence of natural
phenomena

The main advantages of composite materials are their high strength and stiffness, combined with
low density, when compared with bulk materials. In the general case the constituents are
reinforcement and a matrix.

One simple scheme for the classification of composite m aterials is shown in Fig. 19, which
consists of three main divisions: particle -reinforced, fiber -reinforced, and st ructural composites;
also, at least two subdivisions exist for each.

Fig. 19 Classification of composite materials

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3.3 properties of composite materials
The reinforcing phase provides the strength and stiffness. In most cases, the reinforcement is
harder, stronger, and stiffer than the matrix. The reinforcement is usually:
 Particulate: They may be spherical, platelets, or any other regular or irregular geometry.
Particulate composites tend to be much weaker and less stiff than continuous fiber
compo sites, but they are usually much less expensive. fig.20
 Fiber: A fiber has a length that is much greater than its diameter. The length -to-diameter
(l/d) ratio is known as the aspect ratio. As a general rule, the smaller the diameter of the
fiber, the high er its strength, but often the cost increases as the diameter becomes smaller.
Continuous -fiber composites are often made into laminates by stacking single sheets of
continuous fibers in different orientations. Typical fibers include glass, aramid, and
carbon, which may be continuous or discontinuous. fig. 20

Fig. 20 Typical types of fiber [9]

 Matrix Phase: The continuous phase is the matrix, which is a polymer, metal, or ceramic.
Polymers have low strength and stiffness, metals have intermediate strength a nd stiffness
but high ductility, and ceramics have high strength and stiffness but are brittle.
 In polymer and metal matrix composites that form a strong bond between the fiber and
the matrix, the matrix transmits loads from the matrix to the fibers throug h shear loading
at the interface. In ceramic matrix composites, the objective is often to increase the

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toughness rather than the strength and stiffness; therefore, a low interfacial strength bond
is desirable.

Both the reinforcement type and the matrix af fect processing. The major processing routes for
polymer matrix comp osites are shown in Fig. 21
Two types of polymer matrices are shown: thermosets and thermoplastics.
 A thermoset resin sets up and cures during processing, it cannot be reprocessed by
rehea ting. By comparison, a thermoplastic can be reheated above its melting temperatu re
for additional processing.
 In general, because metal and ceramic matrix composites require very high temperatures
and sometimes high pressures for processing, they are norm ally much more expensive
than polymer matrix composites.

Laminates: When there is a single ply or a lay -up in which all of the layers or plies are stacked in
the same orientation, the lay -up is called a lamina. When the plies are stacked at various angles ,
the lay -up is called a laminate. Unidirectional (0°) laminae are extremely strong and stiff in the
0° direction. However, they are very weak in the 90° direction because the load must be carried
by the much weaker polymeric matrix. Plies in the 0°, +45°, –45°, and 90° degrees directions is
called a quasi -isotropic laminate, because it carries equal loads in all four directions. Fig.21

Fig. 21 Structures of laminates composites [9]

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Composites versus Metals:
The physical characteristics of composites and m etals are significantly different.
Therefore, because the fatigue threshold of composites is a high percentage of their static or
damaged residual strength, they are usually not fatigue critical. In metal structures, fatigue is
typically a critical design consideration. Fig.22

Fig. 22 Stress – strain curves for Al and carbon/epoxy [9]

Process of obtaining composite materials:
 Extrusion
 Injection molding
 Thermoforming
The chosen process for this study is injection molding.

3.4 Injection Molding

Injection molding is the most important process for the manufacturing of molded parts from
plastic, about 60% of all plastics processing machines are injection molding types. Injection
molding it’s one of the primary processing methods. With this machine we have the possibility to

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manufacture molded parts weighing from a few mg to 90 kg. The injection molding process it’s
represented schematically below. Fig.

Fig. 23 Injection molding process [1]

Most plastics processed by injection molding are thermoplas tics, but thermosets and elastomers
can also be injection molded

3.4.1 Injection molding machine

Most injection machine (fig.24) are general purpose machines. The tasks they perform include
the batch manufacture of molded parts

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1 injection molding machine; 2 machine base; 3 clamping unit; 4 mold; 5 injection unit; 6
controller
Fig. 24 Components of an injection molding machine [10]

Clamping unit:
 The clamping unit with mold mounting platens accommodates the mold.
Injection unit:
 The injection unit consists of a feed hopper, cylinder, screw, nozzle, heater bands and
servo -electric or hydraulic drives and serves the purpose of melting the molding
compound and injecting it into the mold.

Machine base with hydraulic system:
 The machine base supports the clamp ing and injection units.

Components of an injection molding machine
Clamping unit: The clamping unit (fig.25) contains the mold and carries out the following
operations:
 mold closing
 clamping force build -up and locking of the clamping unit
 absorption of the locking force
 mold opening
 part ejection

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Clamping unit with direct hydraulic system
 Here the clamping force is built up by elastic deformation of the clamping unit (including
mold).
 With hydraulic force -fit systems, the clamping force is applied dire ctly by hydraulic force

Fig. 25 Clamping unit [10]
Clamping force:
 The clamping force is the total of all forces acting on the tie -bars of the clamping unit
under strain when the mold is closed (before injection).
 The clamping force is also the force which p resses the two mold halves together.
Locking force:
 The locking force is the total of all forces acting on the tie -bars of the clamping unit when
the part is being molded.
The locking force required during injection depends on:
 The max. lifting force ins ide the mold (counter force inside the cavity as the melt flows
inside)
 The type of clamping system,
 The rigidity of the clamping unit and mold.
Injection unit:
 The injection unit plasticized the molding compound and injects it into the mold.
 Generally speaking, injection units can be equipped with different sized plasticising
cylinders, with different screw diameters (fig.26) . The larger the cylinder the greater the
attainable weight of the molded part, but the smaller the maximum injection pressure.

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Screw (piston) -type injection unit

Fig. 26 Screw type injection unit [10]

During the injection process, the screw acts as a piston, which is pushed forward by the hydraulic
pressure in the stroke cylinder and presses the material presently facing it through th e Nozzle tip
in the mold until it is filled volumetrically (injection phase) and the melt is compressed
(compression phase).

In the plasticization process the material is supplied in granular form, filled into the feed hopper
of the injection unit. From h ere it goes into the cylinder inside which a screw rotates. The
rotating screw plasticizes the material with the aid of the active cylinder heater bands and in
doing so, conveys it forwards to the space at the front of the screw. Fig.27

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Fig. 27 Injection unit [10]

3.5 Applications of composite materials

Composite materials have a large domain of utilization:
 Auto industry
 Aircraft industry (fig.28)
 Bridge structure
 Doors and door frames (fig.29)
 Medical industry (fig. 30)

Fig. 28 Cockpit made of
compos ite material [11] Fig. 29 Door made of
composite materials [11] Fig. 30 Composite artificial
limbs [11]

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4 Purpose and objectives of the paper

38
5 Technological flow

HDPE
50% PP:25%
PS:25%
Packaging Agitator

Injection machine
Deburring machine Cyclone
Centrifu gal dryer

Mill with blades Containers
Manual sorting
Site mill with knives
Separation
Cyclon Purified water Biological
treatment
Filtering Water bath
Dry air jet
Atmosphere Waste
Tank
Deposit Mill
Waste

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A technological flo w represents a s uccession of technological operations through which raw
materials, materials, semi -products, su bassemblies, etc. pass through i n the process of
manufacturing a product or executing a work.
5.1 Description of unit operations
The description of the unit operations shall be carried out in the order of the projected
technological flow of plastics processing, the technological flow is organized according to a
logical scheme of raw materials and auxiliary materials, from the collection of plastic bot tles to
obtaining the finished product.

5.2 Processing of plastics
Waste collection involves the collection, processing and transport of waste for recycling.
Collecting can be:
 Primary – collecting residues in small containers at the place of production;
 Secondary – the collection of waste in containers (bins) located in the yard or on the
streets
 Proper – the collection of waste from secondary collection points and their transport to
storage, or recycling platforms, depending on the situation and waste.
Sepa ration:
 can be done manually using mechanical techniques in dry (airflow, magnetic separation)
or wet (flotation).At this stage on the conveyor belt the impurities such as labels, plugs
are removed manually
Rough cutting:
 This coarse cutting step is desig ned to reduce the size of plastic waste for the purpose of
transporting or feeding the next steps.

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Washing:
It is a washing operation using warm water and detergent. The warm water and the detergent are
used to remove paper, paper glue from HDPE bottles. W ashing is done in a vertical, cylindrical
water bath with a paddle shaker.
Drying
 After washing, 70% of the wash solution remains mechanically entrained on the surface
of the washed material. Removing it can be done by free, mechanical or air drying.
 The c entrifugal drier consists of a truncated sieve, two blades fixed on the conical body
inside it. Drying occurs due to the rotation movement of a site and a body inside it
because the water is mechanically entrained on the surface of the material and thrown
towards the wall of the site. Drying is accentuated by the hot air produced by the pallets
mounted on the conical body.
Fine grinding
 Milling is a mandatory step in the technological process of plastic waste processing and is
the operation of diminishing t he dimensions of solid materials. Grinding is carried out in
mills with knives and a site with a holes diameter of 2 -4 mm, thus obtaining granules of
material of about 4 mm
Mixing
 Mixing is a stage of preparation of the processing process, this ensures the uniform
distribution of the ingredients. Mixing is a complex process influenced by the
characteristics of the materials (nature, density, granulation, coefficient of friction), the
characteristics of the equipment used to mix the materials and its operati ng parameters.
This operation is performed with the mixer that calculates the required volume of a batch.

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Injection
 The injection of plastic materials is carried out by means of a horizontal injection
machine which is characterized by the existence of tw o basic units: the injection unit of
the feeder device, the thermoplastics equipment and the injection and closing system
comprising the system Injection molding closing and opening of a mold, injection
molding device and protective system.
 The injection m achine can operate with a manual, semi -automatic or automatic cycle.
The manual is used to adjust the machine, the semiautomatic cycle is used when the
working parameters have to be changed, and the automatic cycle works after a
predetermined program.
Debu gging
 Debugging is the operation of removing the excess material from the finished product
obtained by injection. This operation can be done manually on a conveyor belt or more
modern, automatically with the deburring machine.
Packaging
 Is the technology of enclosing or protecting products for distribution, storage, sale or use.
Packaging can be described as a coordinated system of preparing goods for transport,
warehousing, logistics, sale, and end use.

5.3 Scheme of the installation
The s cheme of the installation it’s based on the technological flow process

42

Fig. 31 Scheme of the installation

43

6. Design and sizing
The 3D design of the house was made in the 3D modeling software called Catia V5R19.
The modeling software made possible to design a multiple variation of forms. All these forms
can be used to obtain a modular house.
The main step is to obtain modules that make possible the construction of the house in an easy
way.
It will be used modular elements, making possible an easier mounting process.
The future hous e will look like in figure below .

Fig. 32The 3D model made in the Catia program
The rooms will be pla ced in a cross shape, to make that possible the main room will have
symmetrical octagonal shape .
The height of each room will be of 3 meters and the width of 3 meters. The roof of the roo m is a
dome shaped one. (Figure . 32)

44

Fig. 33 The section view of the room wall
For each room takes three modules of 1 -meter length showed in the following picture fig. 34.

Fig. 34 Module used for the walls .

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The walls are made of two layers. First layer represents the interior of the house. (Fig. 33)

Fig.35 The interior side of the first module
The firs layer has a thickness of 15 cm. In order to obtain a good isolation, between the two
layers is a gap of 10 cm. (Fig.36 )

Fig. 36 The gap between the two elements .

46

Second layer will have contact with the first one and with the exterior. Both modules have
similar construction, on the first layer to make a gap between the two modules it is used spacers
with a width of 10 cm. On the second layers’ same spacers can be found but in this case it will be
used to hold the soul use d to cover the house making this way eco -friendlier.
The main octagonal body will be made by using two types of modules.
The first type has the f ollowing shape showed in fig. 37

Fig. 37 The 3D shape of the beam
It will be mounted into the ground and represents the corners of the house.

Fig. 38 The beam used to obtain the form of the house

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Dimensions of the beam is represented in the following figure

Fig.39 The beam main dimensions
The total length of the module is 3.6 meters. The second module is a cross beam used to
construct the walls. (fig.40 )

Fig. 40 The beam used to construct the wall
Each module has a length of 4 meters and width of 40 cm. To make possible a stabile connection
the bodies will have the form show ed in fig. 41

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Fig.41 The form of the beam
One side will have a groove to increase the sta bile connection between the two element s.
The entrance will be mounted on e of the sides, the other three will be used for rooms.
To reach more sun light in the rooms, on each room side will be mounted semi lucid glass.
On the main body will be mounted one roof made from glass in order to increase the interior
light. All these elements mounted together results the assembly showed in the figure below. Fig .
Fig.42 The real 3D model

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7. Experimental part
7.1 Working method
The specimens were obtained in the laboratory of the Transilvania University Research Institute,
using the injection machine. These were made of granules of High -density Polyethylene
Recycled , Polypropylene Recycled and Polystyrene Recycled .
For the experimental testing of the composite material , the percentage for the materials are
HDPE -50%, PP -25% and PS -25%. After the manual mixing of the composition , the injection
machine needs to be prepared. Fig 30

Fig. 43 The interface of the injection machine
In the plastification process the material is supplied in granular form, filled into the feed hopper
of the injection unit . From here it goes into the cylinder inside which a screw rotates. The
rotatin g screw plasticises the material with the aid of the active cylinder heater bands . After this
step t he specimens is automatically re leased from the mold .

50
After the injection molding process, by varying the working parameters (tab. 7) have resulted 11
specimens of type HDPE: PP: PS=50:25:25 %, with a quantity of 1.5 kg of granular recycled
materials (750g HDPE, 375g PP, 375g PS) .

Tab. 7 Parameters of the 11 specimens
In the T ab.7 are represented the variation of working parameters for the 11 specimens.
Signification of the arrows:
 The red arrow represents the lower values for the different types of parameters
 The yellow arrow represents the medium values for the different types of parameters
 The green arrow represents the high values for the different types of parameters
The injec tion temperature of plastics (HDPE, PP and PS) is in the range between 200 – 270
degrees Celsius.
7.2 Specimen testing
The specimens were tested on the following machines :
 Traction machine – compression (Z020, Zwich/Roell )
 Impact test equipment

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Traction machine – compression:
The specimens were subjected to mechanical tests on the traction and compression machine
(Z020, Zwich / Roell).
The principle of the traction test method is to stretch the specimen along its main axis until it
breaks or until the deformation reaches a pred etermined value. The supported load (force) and
elongation of the specimen are recorded.
The traction device is composed of two jaws, an actuator jaw and a clamping jaw, between the
two jaws being attached to the specimen.
The shape and size of the specime n is determined by the nature of the material from which it is
made. In the case of composite materials based on HDPE, PP and PS recycled, the dumbbell
shape specimen is used, the elongation or rupture takes place in the c enter zone, the narrower
zone .
The princi ple of the compression test method consists in compressing the specimen along its
main axis to breakage or until tension or deformation (compression) reaches a predetermined
value. Recorded load and compression of specimen are recorded.
Impact test equipment
The principle of this method consists in positioning the horizontal specimen on the two strings
and subjected to a shock test by a single hit. The specimen is fixed at one end, the other being
free, this free part will be hit by the pendulum hammer. This method determines the impact
energy absorbed by the sampl e up to the moment of rupture .
The impact test is used to determine the behavior of materials at high deformation rates. With
this appliance, it is possible to test plastic, ceram ic and composite impact.

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53

54

55

56
References :
[1] W. Michaeli, L. Walters, H. Greif, F.J. Vosseburger, Plastics Technology
[2] http://www.chem1.com/acad/webtext/states/index.html [18:22 / 10.01.2017]
[3] Donald R. Askeland – Pradeep P. Phulé . The Science and Engineering of Materials, 4th ed.
Brooks/Cole. Ch.15 – Polymers. 2003
[4]https ://www.bing.com/images/search?view=detailV2&ccid=qVgK1mlO&id=0B920BE1DC6
6F656E9D1485767D1A49A76C68EA5&thid=OIP.qVgK1mlOmVQj84qIto2AeQEsA8&q=shor
t+section+of+linear+poly(ethylene)&simid=608030133567751889&selectedIndex=19&ajaxhist
=0 [13:08 / 12.01.2017]
[5] https://www.doitpoms.ac.uk/ [19:58 / 12.01.2017]
[6] https://sustainabledevelopment.un.org/ [16:21 / 29.01.2017]
[7]https://www.bing.com/images/search?view=detailV2&ccid=2by5ZTJF&id=55CCC7583C876
E0271643DCA8BB12E125B849570&thid=OIP.2by5ZTJF31ls Mc1rPJr_jgEsCE&q=coduri+reci
clare+plastic&simid=608051389343467103&selectedIndex=2&ajaxhist=0 [20:07 / 23.02.2017]
[8]https://www.bing.com/images/search?view=detailV2&ccid=0UBSAn53&id=F8D2D27E9234
F80CE98B5359D07B38B22F7E38 B3&thid=OIP.0UBSAn53qzAwDTL –
WvSwdQEsC1&q=products+made+from+recycled+plastic+%232&simid=60800517125990076
2&selectedIndex=0
[9] R. P. L. Nijssen , Composite Materials. An Introduction
[10] https://www.arburg.com/en/
[11]http://www.nptel.ac.in/ courses/Webcourse contents/IISc BANG/Composite%20Materials/pdf/
Lecture_Notes/LNm11.pdf