metallized thermoplastic composite

Metallized Thermoplastic Composites

EDINBURGH NAPIER UNIVERSITY

B.ENG POLYMER ENGINEERING

3RD YEAR

FINAL REPORT ON

METALLIZED THERMOPLASTIC

COMPOSITES

METRICULATION NUMBER-40081777

NAME: RAHUL R AHUJA

EMAIL ADDRESS: [email protected]

Supervisor name: Dr. Mike Barker

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mailto:[email protected]


Acknowledgement

I would want to like acknowledge my deepest appreciation to Dr. Mike Barker, who has attitude

and the substance of a genius; he encouraged and conveyed a spirit of adventure in regards to

research, and an excitement in regard to teaching. Without his guidance and persistence this

project wouldn’t have been possible.

I also would like to thank MS Lynn for supporting in all the testing laboratory work and showing

how to measure and follow the rules of safety for taking precautions while testing. All the testing

work was demonstrated to me and was shown properly so that I can perform all the laboratory

tests accurately.

I would like to show my sincere thanks to all the faculty members of the department of Polymer

Engineering Department. I am also thankful to my parents for their constant encouragement and

support. I am also grateful to many people who have, directly or indirectly, have lent their helping

hand in this project.

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Abstract

Polymer composites were prepared from linear low density polyethylene as the base material and

utilizing 75 % graphite coated nickel metallic fillers by melt processing technique using a

Brabender mixer at 170 C and 30 RPM spindle speed. Sample sheets were formed by pressing

into 2 mm thick plates, from which samples were taken for physical, mechanical and electrical

characteristics measurements. Composite with metallic powders concentrations ranging between 0

and 50% by weight have been prepared. Samples were utilized for tensile, electrical and

mechanical testing was prepared from hydraulic press, at 160 C for 2 minutes and then cooling into

cold press for 2 minutes. Metal filled thermoplastics composite showed average mechanical

properties degradation and they showed less conductive properties.

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Table of contents

1. Introduction………………………………………………………………………………...5

1.1 The aims and objectives………………………………………………………5

2. Literature Review…………………………………………………………………………..6

2.1 How is LLDPE made and why LLDPE? ………………………………….…..6

2.2 Applications of conductive polymers……………………………………….….6

2.3 Limitations of conductive polymers……………………………………………8

2.4 Filler concentration for electro conductive polymer composites…………..9

2.5 Effect of temperature and Dielectric breakdown………………………...….10

2.6 Dissipation factor (dielectric loss tangent)…………………………..……….11

2.7 Dispersion and distribution..................................................................…...12

2.8 Polarization and Dielectric Constant ………..……………………………….13

3. Experimental Procedure …………………………………………………………………16

3.1 Processes performed for forming plaques and mixing …………………….16

3.2 Information for Brabender Mixing and its process…………………………..17

3.3 COMPRESSION MOULDING OF THERMOPLASTIC FILLED

WITH METAL FILLERS…………………………………………….………………18

3.4 PROCESS FOR TENSILE TESTING OF PLASTICS………………………19

3.5 3 Point Bend test………………………………………………………………...20

3.6 Process for CHARPY IMPACT TESTING…………………………………….20

3.7 Electrical testing of polymers………………………………..………………….21

4. Results …………………………………………………………….…………………………..22

5. Discussion………………………………………………………….………………………….41

6. Conclusion………………………………………………………….………………………….42

7. References …………………………………………………………………………………….43

8. Appendix ……………………………………………………….………………………………44

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Introduction

Thermoplastics are polymers which soften without any chemical change and harden when cooled,

and may be remoulded many times till they degrade (Katchy, 2000). They are increasingly

replacing many materials such as metal, glass, wood and paper in many applications (Obasi,

2007). The broad spectrum of properties which are offered by variety of thermoplastics together

with the techniques of compounding them with other materials has been effective and vital tool for

achieving specific balanced combination of physical properties and processing

characteristics(Obasi,2007).Combination of thermoplastic polymers and metallic fillers are new and

interesting class of materials that when combined offer wide applications in many fields e.g.

discharging static electricity, heat conduction, gas storage, electromagnetic shielding, batteries,

solders etc. Commodity thermoplastics exhibit good mechanical and electrical properties when

filled with metallic powders. Polymer composites which contain the dispersed conductive fillers it

depends on various factors like their spatial distribution inside the polymer matrix, shape and size

of the filler particles, the filler surface and its interaction with the polymer matrix, and adjacent

particles and its contact with each other. These factors can determine one particle to another

transporting charge from each other. Polymers are long chain molecules and are widely useful for

producing products like films, coatings and adhesives. Generally polymers are naturally obtained

but they mostly are synthesised. The properties can be changed to reach the end use application

of the customer.

Combination of 75% Nickel coated Graphite with L.L.D.P.E (ICORENE 3560) to produce range of

compression moulded plaques. These plaques were used for variety of mechanical and electrical

tests. The sheets are about 2mm thick and from there these standard specimens were cut out for

mechanical tests as well as electrical tests. After adding the metallic powders with different

formulations and after performing the tests we compared it with the base material that is L.L.D.P.E

keeping it as a reference. We noticed some good results and we got to know how the metal

powder affected the plastic and what changes it made to its properties.

The aims and objectives

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1. Formulation of a range of thermoplastics containing electrically conductive additives.

2. Prepare mechanical and electrical test samples from the newly compounded materials.

3. Conduct a range of mechanical and electrical tests on the conductive materials in order to

characterise their performance for specific applications.

4. Compare the results with alternative materials.

Literature Review

2.1 How is LLDPE made and why LLDPE?

Polyethylene is obtained from crude oil into gasoline or it is modified from natural gas. It is obtained

out directly from a refinery to a separate polymerization plant. In a commercial polyethylene,

number of repeat units ranges from 1000 to 10 000 .Polyethylene is a thermoplastic polymer and it

consists of long hydrocarbon chains. The melting point for average low-density polyethylene is 105

to 115 °C .Most polyethylene’s have good chemical resistivity, meaning they are not attacked by

strong acids and bases. Polyethylene generally burns slowly having a blue flame which has a

yellow tip and has an odor of paraffin. Polyethylene can be generalized in different categories but it

is mainly classified on density and branching. With regard to many polymers, the main types of

polyethylene grades are HDPE, LDPE and LLDPE.

LLDPE is defined by its density range of 0.915 – 0.925 g/ cm3. LLDPE has significant amount of

short branches which are linearly arranged, commonly made by copolymerization of ethylene with

short chain alpha olefins. LLDPE has very good tensile strength as it is linearly arranged and it also

exhibits higher impact and puncture resistance than LDPE.LLDPE IS used in packaging,

particularly films or bags and sheets. Cable covering, toys, lids, buckets, containers and pipe.

LLDPE is used predominantly in film applications due to its toughness, flexibility and transparency.

LLDPE has established itself in almost all the markets for polyethylene. Linear low density differs

from low density polyethylene structurally due to absence of long chain branching. There is a

different manufacturing process for LLDPE and LDPE. The copolymerisation process produces an

LLDPE polymer which has a narrower molecular weight distribution than conventional LDPE.

Linear low-density polyethylene (LLDPE), due to its cheap price and wide ranging properties, has

been widely used instead of other polyethylene family. LLDPE has unique rheological and melt

flow properties. LLDPE has less shear because it has narrower molecular weight distribution and

shorter chain branching.

2.2 Applications of conductive polymers.

There are various applications for conductive polymers which are as follows,

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Static suppression. Electrostatic discharge has been a very critical problem in the electronic

industry, as low volts like 50 volts can even damage sensitive electronic components, this amount

of volts are very common in this kind of electronic equipment’s. The protection is commonly made

by a plastic material which have been somewhat conductive with the help of weaved metal or

carbon fibres. As these plastic materials are inherently non-conductive they need to be tested

before put out on use. So that it can be assured that they continue to have conductive properties.

These types of polymers have been used to supress static on computer screens, on films, and in

windows.

Batteries: in the coming future there is a need of gigantic portability for electronics, it is very

important to have improved batteries. Now a days society seems to be continuously on the move

and they generally carry electronics with them. Hence, there has been a massive growth in laptop

computers, mobile phones, and PDA’s. Electronics have come out in all the places with which we

might spend our time with. So the portability of it plays a major role. Therefore, replacing heavy

metal components with light weight polymers which are highly desirable.

Electrodes of general batteries are made of metals.( Car batteries are made of lead,

nickel/cadmium is used for flashlight batteries, lithium is used for button cells.) In place of these

kind of metals if we use conductive polymers, the following advantages are shown, lower weight,

lower cost, more charge/discharge cycles, lower toxicity, and improved recyclability. Hence,

replacing these metals with conductive polymers is highly desirable and has also been successful

commercially. We obtain metals from the mines which far more costly and harming our

environment than obtaining of raw polymer materials from natural gas, deep oil wells, or from

residual plant materials.

Light – emitting diodes: the old backlit LCD displays have been replaced by the conductive

polymers named LED’s. These devices are having sandwich- type structure where the active

polymeric film layer lies between a semi-transparent anode and a back row cathode. The entire

device is having uniform light emitted from the device. These devices have already found

applications in cellular telephones, displays for home appliances, PDAs, and numerous industrial

devices needing a readout display.

Micro tools: The conductive polymers have a good property that they swell when they conduct, so

that means the electrical signals are modified to mechanical energy, which is similar to

piezoelectric materials. But in contrast to piezoelectric films. These conductive polymer films work

well at low voltages, thus it expands the area which is used of applicability for devices.

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Solder: Solder is massively used in the electronics industry to attach the electronic devices

physically and electrically which are printing wiring boards which connect them together. Tin and

lead mixture is used for soldering the devices. And this has been used extensively in the industry

for 13 decades. But there has been concern regarding the landfills because lead in these

electronic products is dumped there after its application, where it can leach into the water supply.

There has been much progress in finding other metal compounds for using it instead of lead for

avoiding landfills and it has also a reached a small niche which has been to use conductive

adhesives for a solder replacement. Conductive filler material loaded with epoxies are used for

making up conductive adhesives. The biggest disadvantages of these conductive adhesives is that

they are made of thermosets and then cannot be reused or remoulded for using it again and all

has to be dumped.

Generally conductive adhesives which are entering in the market are generally made of

thermoplastics; they have good potential of making a change in the old trend which has been

followed.

Printed Circuit Boards: Almost all the electronics which are in the market are attached to a “printed”

circuit boards. They are made of a composite of epoxy and fiberglass, a very thin layer made of

copper is etched to form an appropriate pattern to conduct. This process uses a costly

photographic equipment, with which various equipment are used for different types of hazardous

materials. The product which is obtained is cheap and inexpensive but there has been many recent

developments for these type of circuit boards.

2.3 Limitations of conductive polymers

The available conductive polymers in the market do not possess precision in conductance and

different applications for electronics. Whereas silicon chips are far superior in conducting electricity

with speed than the conductive polymers in the market. Hence these polymers are limited when

question of gross changes arises. So conductive polymers cannot be seen as a competitive type

but rather as a complimentary type.

Conductive polymers have some advantages when it comes to moldability and elongation but then

the polymers are weaker in mechanical strength when it comes to comparison with metals but they

are still somewhat better than devices which are silicon based.

Plastics are generally soft and so they are more susceptible to get damaged by scratching and

fracture when it comes to comparison with metals. Moreover, these devices are kept in a case

made of glass for avoiding scratches and physical damage made by the environment.

There is one more factor which affects conductivity in polymers is that these polymers are

generally conductive in two dimension or in a single dimension but metal are fully conductive in

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three dimensions. The polymers have dimensional restriction and that is because they have a fixed

structure like linear or planar so the delocalized electrons follow the network which polymer has

formed.

There have been many researchers which have reached a stage where they have discovered new

methods for casing the electronic information. This has a very bright future for having fast storage

and retrieval devices. The conductive polymers are seen as devices which detect light which can

be used for various commercial and military applications.

As these conductive polymers are a very exciting development and as they become more common

they may enter into the market at a whole new level such as fiberglass composite products which

are presently manufactured. Labels can be made which have an electronic display or the boat can

change its colour if the veil is made of conductive plastics.

Packing Density

Efficiency of continuous network formation for a particulate material is inversely related to how densely it packs. Those that pack densely are inefficient network formers, while those that pack loosely are efficient network formers.

2.4 Filler concentration for electro conductive polymer composites

Almost all polymers are insulating thermally and electrically. Many technological applications have

emerged to make polymers having dispersed fillers to make it conductive. Various methods of

manufacturing composites has emerged for improving the processing which can reduce the cost by

decreasing the ratio of conductive filler is used but effective.

The filler concentration and conductivity are not directly proportional to each other since there is a

narrow range of filler concentration where composite changes from insulator to conductor. As the

amount of filler added to the material is increased the resistivity of the composite stays constant up

to a certain filler concentration level known as the critical concentration. At the critical

concentration resistivity drops sharply however further increase in the filler concentration causes

reduction in resistivity at a much lower rate. The transition from resistor to insulator takes place due

to network formation amongst the conducting filler particles. In this network the filler particles need

not be in physical contact. The path includes large gaps between filler particles.

The composite resistivity is determined by insulating polymer matrix material. At the critical

concentration, dependent on filler morphology and other factors, the number of interparticle

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contacts increases sharply over a narrow range of filler concentration. The conductive path now

consists of a network of filler particles that either are touching or are separated by very small gaps

and the resistivity falls sharply as a result. Once an extensive conductive network has formed,

further increases in filler concentration increase the average cross section of the conductive

network by increasing the number of parallel pathways and the volume resistivity gradually falls

accordingly.

In the percolation process the network formation is very important. In the percolation model the

continuous formation is necessary through the lattice for taking in account of the concentrations for

both the materials which are compromised in the network. For the conductive filler, the critical

concentration is very sensitive to its aspect ratio, which is defined as the ratio of the long

dimension to the short dimension of the filler particles.

The resistivity versus filler concentration relationship remains about the same as the aspect ratio

changes. Network formation begins at lower filler concentrations as the aspect ratio increases.

The polymers conductivity does not increase continuously as we increase the conductive filler

contents, rather the relationship in nonlinear. The percolation threshold is at which conductivity

increases in order of magnitude from insulating range to semi conductive or conductive ranges.

There is a need to monitor the homogeneity and a composite, which determines the morphology,

remained unchanged and the filler dispersion should be uniform. The void level has to be verified

which also influences electro conductivity, within the samples. The density of the samples is to be

measured with weight in water and in air using proper balancing equipment.

2.5 Effect of temperature and Dielectric breakdown

Dielectric constant is affected by temperature change, higher the temperature the polymer chain

gets broken which enhances the thermal agitation. The change in electric field polar group will be

affected and will get free to orient. Polymers are long chained structures so when the temperature

goes low, the chains get frozen and it reduces the dielectric constant. Even at very high

temperature dielectric constant is affected due to high motion in chains that leads to disturbance in

orientation of dipoles. Though the measured frequency and temperature, electronic and atomic

polarization is spontaneous, kinetic energy is a necessity to induce segmental movement. The

dielectric loss can be seen more with respect to relaxation mechanism and temperature when it is

high.

Electrical breakdown occurs when the dielectric strength which is the maximum electric field

applicable on dielectric material is exceeded and may lead to catastrophic failure like short circuit.

It occurs only when heat generated by applied voltage is lower than the heat by losses and thus

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dielectric is unable to reach a state of internal thermal equilibrium. This failure happens due to

large thickness of dielectric, high temperature of surrounding and dielectric, continuous application

of high voltage. Even high humidity in air can affect dielectric breakdown through electrolytic

process.

2.6 Dissipation factor (dielectric loss tangent)

The apparent power consumed in the material to the real power consumed is known as dissipation

factor. When voltage i applied to dielectric current that flows at 90° out of phase with voltage.

When the current to voltage is leading less than 90° the reason can be because of imperfect

insulating material and degree of polarization. Polarization involves movement of charged particles

which oscillate in an external field where the particles which carry the charge move between the

two configurations, and for that they dissipate the energy.

Charges generally oscillate back and forth in their alternative configurations. In an electric field if there

were no losses the charge motion would be 90 o out of phase in regards with the voltage. In dielectrics

energy is dissipated just like a current in resistor which gives a small phase shift .The loss tangent,

, also called the dissipation factor, .

The Loss Factor L is the most useful which is the loss tangent times the dielectric constant:

It shows us how much energy is dissipated in an oscillating field by a dielectric. If the material has

to be found out to minimize or maximize dielectric loss, L is needed to be found out.

So as the dielectric material is inserted in a electric field which is cyclic then amplitude and

frequency P power is dissipated

The dielectric constant is for the material and for loss tangent it is tan .Throughout the material

power dissipates it in the form of heat energy and it is uniform as well. So the greater we have the

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loss factor the frequency increases and so there is heat loss. Dielectric loss is manipulated

in processing e.g. radio frequency welding for polymers .

The displacement of charge or of molecules carries a dipole

moment when a material is in the electric field. An alternating field

makes the charge swash back and forth: It shows the

displacements in the shown direction A) when the polarity gets

reversed, the negative ions displaced upwards and positive ions

travel upwards. B) When there is an oscillating field the ions

oscillate in that. If these oscillations oscillate exactly in the same

phase then no energy would be lost but often there is a

considerable phase shift.

Materials which have considerable dielectric loss they usually

then have awkwardly shaped molecules and they possess a

dipole moment. They generally respond in an oscillating field in

which they rotate, because of the shape they interact with each

other and heat energy is dissipated like microwave heating. As

the equation suggests that when energy is dissipated it is directly

dependent on its frequency so higher the power is dissipated. Michael F. Ashby, 2009)

2.7 Dispersion and distribution

In Processing of polymers the mixing is a very important operation which affects the material

properties to combine the properties with other plastics and enhance the physical characteristics.

To impart some specific properties to the material polymers are mixed with some enhanced

additives to improve its mechanical properties. There is dispersive mixing and non-dispersive

mixing and they are very much different from each other. The identification of these mechanisms is

very important for enhancing its process characteristics. When multiphase system is concerned,

dispersion mixing shows decrease in size of the cohesive minor component and because of it

these clusters of particles are generally solid or in form of liquid droplets.To have a good spatial

distribution the minor component has to be spread out throughout the matrix that is called

distributive mixing, which is shown in the figure below. Mixing in any mechanism can occur either

stepwise or simultaneously. The stage at which this dispersive mixing is achieved the balance is

determined by the cohesive forces which hold the agglomerates together and the disruptive

hydrodynamic forces. For droplet size distribution the applied stresses have a crucial role. When

the mixing equipment is being used the flow geometry shows a field pattern which shows a

superposition for flow raging from a pure rotation to pure elongation.

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A distribution of stress for elongation flow gives us only a global perspective on mixing efficiency in

various types of equipment’s. For having accurate mixing and to check its efficiency we need to

track the elements in the minor phase during their entire residence time in the equipment and will

have to follow the dynamics of the break up. However, its global perspective is generalized by

using the efficiency of mixing provides one means to discriminate between various designs and

processing conditions for mixing equipment.

Fig 3. Figure showing dispersion in different polymer matrices

2.8 Polarization and Dielectric Constant

The material which can polarise in response to a applied field which is expressed as permittivity

and it relates to dielectric constant. The permittivity of the dielectric to the permittivity of a vacuum

is known as Dielectric constant. The dielectric constant depends on the polarization of material,

higher the polarization in an applied field higher the dielectric constant and its strength. In the past

the materials were normally mica and silicon dioxide but now polymers are most widely used as

dielectric constant. This is because of ease in process ability, flexibility, able to tailor made for

specific uses and better resistance to chemical attack. Nearly 50years back, it was polyvinyl

fluoride and aromatic polymers that were used in capacitor for dielectric constant. Polymers is easy

to make and fabricate into film with solution casting and spin coating which is further immersed in

organic substrate, electron, UV or glow discharge methods. It is possible mainly due to its low Tg

and Tm. Ceramics can also be used as dielectric constant but they have high thermal properties

and high processing costs whereas polymers are cheap, have good thermal properties and is easy

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to process even at high or low temperatures. The ceramic materials have a large coefficient of

thermal expansion which makes it susceptible to degradation in atmosphere.

Electric field consisting a dielectric material which has arrangement of a free space management of

electric dipoles and they are made of charges which are positive and negative and their centres do

not coincide. These charges cannot contribute to the conduction as they are not free. Rather these

charges are bound in a place by atomic and molecular forces and they only shift positions in

external fields. Hence these charges are known as bound charges. (A. Orliukas, 1993)

The effect of an externally applied electric field on a dielectric material is twofold:- first, the

formation of electric dipoles in the material as a result of the finite separation of bound charges and

tendency of these induced dipoles to orient themselves in the direction of the field; second, the

orientation, if possible, of dipoles already existing in the material. This total effect is referred to as

polarization. The polarization P in a solid is defined as the dipole moment per unit volume. It has

the same units as the surface charge density and is, in fact, equivalent to the surface charge

density.

In view of the above, a dielectric may be defined as a material that can be polarized. A

characteristic common to all dielectric materials whether they are solid, liquid, gas, crystalline or

amorphous, is their ability to store electric energy. This electric energy storage characteristic is the

result of the polarization of a dielectric material in the presence of an externally applied electric

field. Fig 4. illustrates the concepts involved when a material is assumed to be placed between two

charged metallic plates. When the intervening space is free of matter, equal and opposite free

surface charge densities, +σ and –σ, are present on the plates. The electric intensity, Eo, is

uniform and is given by σ/εo (εo is the vacuum dielectric constant) (D. H. Tamboulian, 1965)

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Fig 4.A figure showing representation of distribution of charges between the two plates

a) Vacuum Filled Space b) Dielectric filled space c) applied electronic filed d) electronic flux density

(D. H. Tamboulian, 1965)

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3. Experimental Procedure

3.1 Processes performed for forming plaques and mixing are as follows:

Type Of

Plaque

Nickel +

LLDPE

Weight of metal powders and

plastic powders(grams)

Test Conditions of a

Brabender Mixer

Test conditions

of a

Compression

Press

Test Conditions

for cooling

Metal

Powder

LLDPE

Powder

5% 57.5 2.5 170 C – set temperature

170 C – actual

30 RPM for 10 Minutes

In Brabender Mixer

160 C

temperature

1 Min low pressure

1 Min high

pressure

Cold Press

2 Mins High

Pressure

25C temperature

water cooled

15% 50.5 9.5 170 C – set temperature

170 C – actual


In Brabender Mixer

160 C

temperature

1 Min low pressure

1 Min high

pressure

Cold Press

2 Mins High

Pressure

25C temperature

water cooled

30% 41 19 170 C – set temperature

170 C – actual


In Brabender Mixer

160 C

temperature

1 Min low pressure

1 Min high

pressure

Cold Press

2 Mins High

Pressure

25C temperature

water cooled

40% 36 24 170 C – set temperature

170 C – actual


In Brabender Mixer

160 C

temperature

1 Min low pressure

1 Min high

pressure

Cold Press

2 Mins High

Pressure

25C temperature

water cooled

50 % 35.5 35.5 170 C – set temperature

170 C – actual


In Brabender Mixer

160 C

temperature

1 Min low pressure

1 Min high

pressure

Cold Press

2 Mins High

Pressure

25C temperature

water cooled

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Firstly the metal powders and thermoplastic powders were weighed out using the weighing

balance.

After the powders were weighed according to their ratio for mixing the material were put in

the dry high speed mixer for mixing.

After 2 mins of dry mixing the material was collected from the mixer and poured in the

Brabender mixer for homogenous mixing.

Then little amount of the material was poured into the brabender mixer for checking its

mixing and homogeneity of the melt.

After melting is achieved more material is allowed to be poured for homogenous melt and

filled up till its capacity and pressed with the seal.

The brabender mixer is allowed to mix the material for 10 Mins at 30 RPM.

Then the material is taken out from the brabender mixer and manually pressed for

collecting and storing it together.

Then taking the material after homogenous mixing it is taken to the compression press for

making 2mm thick plaques.

The hot plates are taken out from the compression press and kept in the cold press for 2

mins for cooling the plates.

After cooling the plates it is ejected from the frame and weighed for performing certain

mechanical and electrical tests.

3.2 Information for Brabender Mixing and its process

Equipment

Plasticorders PL2000 using electical heating with mixer type W50 (volume 55cc)

Brabender mixer was used for shear mixing and for homogenous melt. Brabender mixer has

interchangeable measuring heads which shear the plastic with certain temperature and shear of

the screw at specific rpm. The mixer is cost effective, reliable and little expenditure of time and

material. The mixer consists of as mixer back stand with gear unit and a mixer bowl. For safety

system they have a connection with a drive unit through a shear pin coupling protecting both mixer

and drive unit from damage due to overload. The blades are generally made of stainless steel. For

excellent compounding and for good shear the blade rotates in counter rotation. Heating or cooling

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is done either through a cold circulation thermostat or electrically. The measuring principle is based

on creating the visible resistance in which the material opposes to the rotating blades. The

dynamometer moves out of its zero position because of the corresponding torque.

Method for using Brabender Mixer

For initial mixing cycle the sample weight was weighed out to fill the chamber. Then mixer

temperature should be achieved to melt the sample sufficiently. Then speed of rotor was verified to

have melt properly homogenised. Then the material was poured inside at 170 C with slow rotor

speed of 10 RPM. The slow speed is kept so that the material starts getting in molten form. As the

material is being poured and filled the pressure ram is used to load the sample gradually into the

mixer by pressurizing it down to the chamber. This

is continued till all the weighed out sample is

loaded then keeps the pressure ram in position to

close mixing chamber and weight of 20 kg is

placed on the lever arm. Then rotor speed was

increased to 30 RPM for 10 minutes. After mixing

time completes rotor was switched off and

chamber was opened to remove the sample. Then

the chambers and rotors were cleaned with brass

brush/ Knife.

(Fig5 BRABENDER MIXER AND ITS PARTS

REF: www.brabender.com)

3.3 COMPRESSION MOULDING OF THERMOPLASTIC FILLED WITH METAL FILLERS:

Equipment’s used

2 Steel plates, 2 Aluminium plates – optional (to be placed each side of template),

Templates, Heat Resistant Gloves

Procedure

Different percentage of 5, 10, 15, 30, 40, and 50 of 75% Nickel coated graphite with LLDPE. The

temperature required was set for hot press at 160 C for the LLDPE mixed with metal fillers. To

open press pull black handle forward. Wear heat resistant gloves provided to remove plates from

press onto table and open plates. Plates and templates were kept in heated press filled with the

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http://www.brabender.com/


material; hydraulic pump is switched on and is closely pressed. Stop when top plate is in contact

with press top platen for low pressure of 0-4 tons for 1 minute. Then the templates are kept for 1

minute at full pressure of 20 tons. Switch off. After approximately 1 minute, turn red handle to

unlock, pull black handle forwards to open press. Place the hot plates in adjacent cold press and

apply full pressure (15 Tons).Turn on cooling water. When plates are cool enough, remove plates

from press and remove thermoplastic plaque. Replace plates in hot press and close press for next

plaque.

3.4 PROCESS FOR TENSILE TESTING OF PLASTICS ARE AS FOLLOWS:

Fig 6 Tensile Tester

Procedure

The width and thickness of each specimen has to be measured and cross sectional area has to be

calculated in mm2. Appropriate crosshead speed is needed to be calculated , for the first set of test

this is usually 20 mm/min). Specimen has to be mounted in vice grips by raising or lowering the

crosshead. START button has to be pressed and load and extension is to be recorded until the

specimen breaks. It has to be verified that the crosshead speed does not alter during the test. The

broken specimen is to be removed from the grips. After that the test piece is to be checked for

flaws and mode of failure (ductile; brittle; stress whitened etc.). Then the procedure can be

repeated for the next sample at the same crosshead speed.

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3.5 PROCESS FOR 3-POINT BEND TEST ARE AS FOLLOWS:

Fig 7 Sketch of 3 Point Bend Test

Procedure

First the Tensile Tester was set up with the 3 point bend attachment. Dimensions b, h and L

are needed to be measured.Lay test bar symmetrically across supports. Set up PC, with Lloyd

Nexygen software and open console. Raise cross-head so that test bar is almost touching

centre bar.Zero load and extension. Start test and record load deflection curve until sample

breaks or selected % strain is reached.

3.6 Process for CHARPY IMPACT TESTING

Fig 8 Impact Tester

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We require Rectangular section injection moulded bars – unnotched and notched.

Nominal dimensions:

Height (h)=6 mm

Dimensions perpendicular to the direction of the notch (minus the notch depth)

Breadth (b)=6 mm

Specimen dimensions parallel to the direction of the notch

Length (L)=50 mm

The test specimen is to be notched for checking its impact at which it breaks. After that test specimen is to be placed between the base in which notch should be in the centre, facing away from the pendulum. The arm of the pendulum is to be raised till it sticks into its position. The arrest knobs are to be released simultaneously, which releases the pendulum. Once the specimen has broken the movement is to be stopped by the brake.

3.7 Electrical testing of polymers are as follows

Experimental procedure

Find the capacitance of air gap using the capacitance meter. Insert one of the plastic discs into the

gap between the plates, and find the capacitance for each sample. Then measurement is carried

out several times and average is taken. For each material calculate the relative permittivity where,

Relative permittivity= Cmean/c0

Find the cross sectional area of the metal plates, using the micrometer. Find the average value of

capacitance for each sample, by inserting the sample into the gap between the plates and using

the meter, as before and taking many measurements. The relative permittivity of each material can

be calculated by using the formula Cmean=(A/d)

21


Results

Mechanical Tests

Tensile test

Tensile test was performed on the test specimens for measuring its properties with respect

to the 100% LLDPE test specimen and comparing it with the metal powder incorporated

test specimens.

Key

Emod = Elastic modulus

Fy = Yield load

Fmax =Maximum Load

m= Maximum load/tensile strength

dL at Fmax= strain at maximum load

FBreak =load at break/ rupture load

B =stress at break

dL at break = strain at break/ extension

22


S0 = Cross sectional area

For 100% LLDPE without 75% Nickel coated graphite the results are as follows:

Parameter table:

E-Modulus speed : 200 mm/min

Test speed : 200 mm/min

Results table:

EMod FY Fmax M dL at Fmax FBreak B dL at break S0

No. MPa N N MPa % N MPa % mm²

1 209 114 126 19.52 1043.6 121 18.62 1061.4 6.48

2 206 112 112 17.51 20.1 79.7 12.46 823.2 6.40

3 187 112 131 20.40 1023.0 118 18.40 1046.7 6.44

23


Curve graph:

For 5 % of 75% Nickel coated graphite with LLDPE the results are as follows:

Parameter table:



Results table:


Nr MPa N N MPa % N MPa % mm²

1 137 97.6 97.6 17.65 20.9 58.5 10.57 927.7 5.53

2 114 105 106 19.21 1042.1 90.4 16.35 1061.0 5.53

3 120 106 106 16.38 21.7 81.9 12.65 886.8 6.48

24


Statistics table:

Series EMod FY Fmax M dL at Fmax FBreak B dL at break S0

n = 3 MPa N N MPa % N MPa % mm²

x 124 101 103 17.75 361.6 76.9 13.19 958.5 5.85

s 11.9 4.92 4.94 1.42 589.4 16.6 2.93 91.1 0.55

9.64 4.87 4.78 7.99 163.00 21.52 22.20 9.50 9.38

Curve graph:

For 15% of 75%Nickel Coated Graphite with LLDPE the Results are as follows:

Test Conditions:E-Modulus speed : 200 mm/min


Results table:



1 137 101 101 15.56 20.5 61.8 9.55 652.5 6.47

2 142 102 102 15.85 20.4 67.1 10.40 565.3 6.45

3 164 102 102 15.81 19.4 80.5 12.49 786.4 6.45

25


Statistics table:

Series EMod FY Fmax M dL at

Fmax

FBreak B dL at

break

S0


x 148 102 102 15.74 20.1 69.8 10.81 668.1 6.46

s 14.0 0.172 0.793 0.16 0.6 9.67 1.51 111.4 0.01

9.48 0.17 0.78 1.00 3.03 13.86 13.99 16.67 0.18

Curve graph:

For 30 % 0f 75 %Nickel coated Graphite with LLDPE the results are as follows:

Test Conditions:



26


Results table:

EMod FY Fmax M dL at Fmax FBreak B dL at

break

S0


1 123 93.9 93.9 14.52 20.1 36.9 5.71 120.7 6.46

2 160 95.4 95.4 14.75 19.0 57.6 8.90 167.7 6.46

3 141 94.7 94.7 14.64 19.1 58.9 9.11 42.4 6.46

Statistics table:

Serie

s

EMod FY Fmax M dL at Fmax FBreak B dL at

break

S0

n = 3 MPa N N MPa % N MPa % mm

²

x 141 94.6 94.6 14.6

4

19.4 51.1 7.91 110.3 6.46

s 18.1 0.746 0.746 0.12 0.6 12.3 1.91 63.3 0.00

12.85 0.79 0.79 0.79 3.14 24.0

6

24.1

0

57.40 0.00

Curve graph:

27


For 40 % of 75% Nickel coated graphite with LLDPE the results are as follows:

Parameter table:



Results table:



1 100 85.8 85.8 12.97 21.1 59.6 9.01 245.5 6.61

2 109 86.6 86.6 13.17 20.7 60.4 9.19 170.2 6.58

3 110 86.7 86.7 13.19 20.2 60.9 9.32 179.6 6.67

Statistics table:

Serie

s

EMod FY Fmax M dL at

Fmax

FBreak B dL at

break

S0


x 105 86.6 86.2 13.07 20.9 60.0 9.10 207.9 6.60

s 6.23 0.58 0.587 0.14 0.3 0.618 0.13 53.2 0.02

5.96 0.68 0.68 1.08 1.35 1.03 1.40 25.62 0.32

Curve graph:

28


50 % of 75% Nickel coated Graphite with LLDPE.

Test Conditions:



Results table:



1 159 85.2 85.2 12.72 14.0 52.1 7.77 46.2 6.70

2 174 78.7 78.7 11.73 10.5 52.7 7.86 21.6 6.70

3 149 83.9 83.9 12.67 14.8 26.9 4.06 49.5 6.62

Curve graph:

29


Statistics table:

Bend Test

Bend test was performed on the test specimen for comparing the material

stiffness when the metal powders were incorporated with comparison to the

100% LLDPE. There were 3 test specimens for each plaque and the average

was then taken for maintaining accuracy in the results.

Sample

Informatio

n

Sample

Reference

Load at Limit

(N)

Deflection at Limit

(mm)

100%

LLDPE 1 3.59 5

2 4.30 5

3 3.73 5

Average 3.87 5

100 % LLDPE

30

Serie

s



x 161 82.6 82.6 12.37 13.1 43.9 6.56 39.1 6.67

s 12.3 3.49 3.49 0.56 2.3 14.7 2.17 15.2 0.05

7.67 4.22 4.22 4.51 17.46 33.54 33.04 38.99 0.69


Sample

Information Sample Reference Load at Limit (N) Deflection at Limit (mm)

5% of 75%

Nickel coated

Graphite with

LLDPE

1 3.99 5

2 3.89 5

3 4.23 5

Average 4.03

5% of 75% Graphite coated Nickel with LLDPE

31


Sample Information Sample Reference Load at Limit (N) Deflection at Limit (mm)

15 % of 75% nickel

coated Graphite

with LLDPE

1 4.01 5

2 4.38 5

3 4.42 5

Average 4.27 5

32


Sample

Information Sample Reference Load at Limit (N) Deflection at Limit (mm)

30 % of 75 %

75% Nickel

coated Graphite

with LLDPE

1 4.97 5

2 5.25 5

3 4.85 5

Average 5.02 5

33


34

Sample

Information

Sample

Reference Load at Limit (N) Deflection at Limit (mm)

40% of 75% of

Nickel coated

Graphite

With LLDPE

1 6.22 5

2 7.09 5

3 6.34 5

Average 6.55 5


35

Sample

Information

Sample

Reference Load at Limit (N) Deflection at Limit (mm)

50% of 75 Nickel

coated Graphite

With LLDPE

1 8.09 5

2 7.31 5

3 8.27 5

Average 7.89 5


100% LLDPE

5% Metal Filler

15% Metal filler

30 % Metalfiller

40% Metal filler

50% Metal filler

Load (N) 3.87 4.03 4.27 5.02 6.55 7.89

Length(mm) 65.8 65.2 65.9 65.7 65.6 65.8

Breadth(mm) 25.89 25.4 25.8 25.3 25.2 25.9

Depth (mm) 1.75 1.55 1.57 1.62 1.7 1.66

Deflection(mm)

5 5 5 5 5 5

Gradient(L/D)

0.774 0.806 0.854 1.004 1.31 1.57

Flexural stress (MPa)

4.81 6.45 6.637 7.451 8.850 10.91

Flexural strain 0.012 0.011 0.011 0.011 0.012 0.012

Flexural modulus(MPa)

397.24

590.45 611.97 661.766 746.750 948.63

36


Impact test

Impact test was carried out to compare the metal incorporated plaques with

the 100% LLDPE for knowing how it is affected with respect to the plastic

plaque. The results are as follows:

0% of 75% Nickel

coated Graphite with

LLDPE

Notched(1) Notched(2) Notched(3)

Width(W) 3.45 3.24 3.79

Thick(T) 7.22 7.33 7.79

Impact Strength 30.18Kj/m2 29.85 Kj/m2 32.36 Kj/m2

Average 30.79 KJ/m2

5% of 75% Nickel


LLDPE


Width(W) 3.44 3.29 3.77

Thick(T) 7.50 7.80 7.55

Impact Strength 18.8Kj/m2 13.9 Kj/m2 23.3 Kj/m2

Average 18.6 Kj/m2

15% of 75% Nickel


LLDPE


Width(W) 3.42 3.67 3.78

Thick(T) 7.77 7.78 7.72

Impact Strength 11.6 Kj/m2 12.7 Kj/m2 12.3 Kj/m2

Average 12.2 Kj/m2

37


30% of 75% Nickel


LLDPE


Width(W) 3.67 3.62 3.73

Thick(T) 7.74 7.72 7.68


Average 11 Kj/m2

50% of 75% Nickel


LLDPE


Width(W) 3.87 3.79 3.94

Thick(T) 7.70 7.78 7.64


Average 9.2 Kj/m2

100% LLDPE 5% metal filler

15 % metal filler

30 % metal filler

40% metal filler

50% metal filler

0

5

10

15

20

25

30

35

30.79

18.6

12.2 11 119.2

impact strength

impact strength

75 % Nickel Coated Graphite with LLDPE Powder

Impa

ct st

rent

in k

J/m

2

38

40% of 75% Nickel


LLDPE


Width(W) 3.92 3.54 3.67

Thick(T) 7.77 7.62 7.74


Average 11 Kj/m2


Electrical Test

1. 5% of 75% Nickel coated Graphite

Frequency 20Hz

Material inside - Capacitance 20.9 pF

Material out- Capacitance 17.2 pF

Capacitance = Material IN/Material OUT = 1.21 pF

Frequency 300Hz

Material inside – Capacitance 35.5 pF

Material outside – Capacitance 31.85 pF



Frequency 20Hz




Frequency 300Hz





Frequency 20Hz




39


Frequency 300Hz

Material inside – Capacitance 38 pF




Frequency 20Hz




Frequency 300Hz





Frequency 20Hz




Frequency 300Hz




40


Discussion

The above work shows that there has been some degradation in the mechanical properties of the

plaques which were made in the laboratory. The thermoplastic material which was weighed out

and mixed with the Nickel coated graphite metal powder made the weight of the plack increase as

we increased the ratio of metal powders. So accuracy was maintained while mixing but the

brabender mixer had a limit of material which was poured. Moreover the LLDPE material was very

sticky when we mixed in the Brabender as it stuck on the surface when it was being removed for

further process. As the ratio of metal powder was increased it became less sticky on the surface

and was easily removed from the brabender mixer. The color also changed as we increased the

ratio of metal powders in LLDPE powders.

The tensile strength of 100 % LLDPE was 19.11 Mpa but as we mix 5 % of metal powder its tensile

strength comes down to 17.74 Mpa, for 15 % metal filler its tensile is 15.78 Mpa, for 30 % metal

41


filler it is 14.69 Mpa, 40 % metal filled has tensile strength of 13.06Mpa , 50 % metal filled has

tensile strength 11.9 Mpa. So as the ratio of metal powder was increased the plack became stiffer

and brittle. As the percentage of metal powder increases from 5% to 50% the load at limit in bend

test increased from 3.78 N to 7.89 N which indicates that metal powder makes the product more

stiff and brittle to fracture. The plaques were before made of 2mm thin sheets from which specimen

was cut out for impact test but we noticed that the sheet was too thin for having accurate results as

the specimen used to come out from the impact tester. So new sheets of 4 mm were made for

having accuracy and the specimen did not move out of its place. These specimens were then also

used for electrical testing. There was no significant conductance with increase in metal powders

rather there was degradation in mechanical properties of the plack.

Conclusion

Thus report can be concluded by mentioning that there was no significant change in the

thermoplastic by adding the metal fillers. The material became more brittle and it was more

susceptible to fracture. The dispersion and distribution of the metal filler was not proper and that

resulted into less conductivity. The Brabender mixer couldn’t allow proper dispersive mixing and

that made the polymer having clusters of metal particles at one end and so there was not enough

distance between two atoms to transfer the charge which did not allow the current to conduct from

one end to the other. So this caused clusters of thermoplastic polymers and hence conductivity

wasn’t found which also resulted in less mechanical properties because it made bonding between

atoms weak.

42


Reference

Literature review

1. http://www.ceresana.com/en/market-studies/plastics/polyethylene-lldpe//

[Accessed March 3,2013]

2. Obasi, H. O. B. (2007). Studies on the mechanical and Transport Properties of natural

Rubber / Linear Low Density polyethylene Blends. M. Sc Thesis, FUTO, Nigeria.

3. Katchy, E. M. (2000). Principles of polymer Science, EL’DEMAK Ltd, Nigeria.

5. Yaukey, John, USA Today, August 15, 2000.

(D. H. Tamboulian, Electric and Magnetic Fields, Harcourt, Brace and World Inc.,

43

http://www.ceresana.com/en/market-studies/plastics/polyethylene-lldpe//


New York, USA (1965))

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8. Kaner, Richard B. and Alan G. MacDiarmid, “Plastics That Conduct Electricity,” Scientific

American, p. 106, 1988.

9. De Gaspari, John, “New alternatives In Conductive Plastics,” Plastics Technology, p. 13-

15,November 1997.

10. “Conductive Polymers Spark New Ideas,” Technology Edge, p.13, April 1993.

11. “Electrically Conductive Polyimide Films,” NASA Tech Briefs, p. 57, August 1993.

12. Shirakawa, Hideki, et al, J.C.S. Chem. Comm., 1977.

Budinski, K.G. and Budinski, M.K. (2009) Engineering Materials: Properties and Selection,

9th edition, Prentice Hall, Upper Saddle River, New Jersey, USA. ISBN-10: 0137128428,

ISBN-13: 9780137128426

13. http://www.rheology.org/sor/publications/rheology_b/jan97/mixing.pdf

[Accessed April 24, 2013]

14. http://www.kfm.p.lodz.pl/projekty/Yevgen%20Mamunya%20-%20lecture1.pdf

[Accessed march 21,2013]

15. http://www.sciencedirect.com/science/article/pii/B9780750681490000064

[Accessed April 17,2013]

16.

http://www.sciencedirect.com/science/article/pii/095522199390127D (Relaxation dispersion of ionic conductivity in a Zr0·85Ca0·15O1·85single crystal)[Accessed April 24,2013]

44

http://www.sciencedirect.com/science/article/pii/095522199390127D

http://www.sciencedirect.com/science/article/pii/B9780750681490000064

http://www.kfm.p.lodz.pl/projekty/Yevgen%20Mamunya%20-%20lecture1.pdf

http://www.rheology.org/sor/publications/rheology_b/jan97/mixing.pdf

http://www.brabender.com/fileadmin/dateien/gb/download/kunststoff/download/broschueren/kneter/25061_E_Measuring_Mixer.pdf

http://www.brabender.com/fileadmin/dateien/gb/download/kunststoff/download/broschueren/kneter/25061_E_Measuring_Mixer.pdf

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