'' Thermal and Mechanical Properties of polymeric composites

loaded with waste materials''

Presented by

Marwa mahhmoud Ibrahim abd el kader

الخواص الحرارية و الميكانيكية لمتركبات بلمرية محملة ببعض "

"المخلفات

إعداد

القادرمروة محمود ابراهيم عبد

VII

List of Tables

Page

Table (2-1): the composition of sample of NR with

different phr of recycled rubber to get (W-group) of

samples.

43

Table (2-2): the composition of sample of NR with

different phr CaCO3 to get (M-group) of samples.

44

Table (2-3): the composition of sample of NR with

different phr foaming agent to get (F-group) of samples.

45

Table (2-4): the composition of sample of NR with

different phr foaming agent+ CaCO3 to get (S-group) of

samples.

46

Table (3.1): The porosity values which give good fitting

for foamed NR and CaCO3/Foamed NR groups.

69

Table (3.2): The variation of crosslink densities as a

function of concentration for four groups of samples.

97

Table (3.3): The comparison between parameters of the

two optimum samples is summarized

104

Introduction & literature survey Chapter 1

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1.1 Introduction

Thermal insulation is the method of preventing heat from escaping a

container or from entering the container. In other words, thermal insulation can

keep an enclosed area such as a building warm, or it can keep the inside of a

container cold. Heat is transferred from one material to another by conduction,

convection and/or radiation. Insulators are used to minimize that transfer of heat

energy. In home insulation, the R-value is an indication of how well a material

insulates (1)

.

Building insulation refers broadly to any object in a building used as

insulation for any purpose. While the majority of insulation in buildings is for

thermal purposes, the term also applies to acoustic insulation, fire insulation,

and impact insulation (e.g. for vibrations caused by industrial applications).

Often an insulation material will be chosen for its ability to perform several of

these functions at once

Thermal Insulation in buildings is an important factor to achieving

thermal comfort for its occupants. Insulation reduces unwanted heat loss or gain

and can decrease the energy demands of heating and cooling systems. It does

not necessarily deal with issues of adequate ventilation and may or may not

affect the level of sound insulation (2)

.

. In a narrow sense insulation can just refer to the insulation materials

employed to slow heat loss, such as: cellulose, glass wool, rock wool,

polystyrene, urethane foam, vermiculite, and earth or soil. But it can also

involve a range of designs and techniques to address the main modes of heat

transfer - conduction, radiation and convection materials. (3, 4)

The continuous development of the industry made it very important to

have information about new materials whose properties have never been

Introduction & literature survey Chapter 1

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measured experimentally. Polymers play a very important role in the modern

society it difficult to imagine a branch of industry where it would be possible to

do without polymers especially the novel materials with previously unknown

properties.

In 1839, Charles Goodyear discovered that the addition of sulfur to raw

rubber could dramatically improve properties. The discovery of sulfur

vulcanization changed the rubber from a thermoplastic, which can be

reprocessed many times, to a thermoset, which can be shaped only once. Sulfur

vulcanization is used in current automotive tires in order to give the desired

properties and can meet the requirements for automotive tire applications.

The largest volume of thermosetting polymers in the waste stream is

generated by scrap tires. One approach to the successful reuse of recycled tire

rubber is its use as light fill in Civil engineering and highway projects. This

approach is hampered by the absence of data (5)

.

The shape of a tire allows for easy entrance and containment of

rainwater. This creates an ideal breeding habitat for mosquitoes (6)

In addition to

the nuisance caused by clouds of mosquitoes generated by scrap tire piles,

mosquitoes can carry serious diseases.

Fires emit clouds of noxious black smoke, carbon black, volatile organics, semi-

volatile organics, polynuclear aromatic hydrocarbons, oil, sulfur oxides,

nitrogen oxides, carbon oxides, and airborne particulates, such as arsenic,

cadmium, chromium, lead, zinc, iron, lead, etc, which pose serious

environmental problems to air, water and soil(7)

. So waste tiers presents a very

serious economic and environmental problem we have to re use them to help in

decreasing their hazards economically and environmentally.

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Polymeric composites are materials made up of two or more components

and consisting of two or more phases (8)

. These composites have recently drawn

considerable attention, due to the ease with which polymer properties can be

modified to achieve characteristics that can not be achieved by a single polymer

system. The most difficult task is the development of materials with a full set of

desired properties (9)

.

1.2. Thermal properties of polymeric materials

Heat transfer is a discipline of thermal engineering that concerns the

exchange of thermal energy from one physical system to another. Heat transfer

is classified into various mechanisms, such as heat conduction, convection,

thermal radiation, and phase-change transfer. All forms of heat transfer may

occur in some systems (for example, in transparent fluids like the Earth's

atmosphere) at the same time. Heat transfer only occurs because of a

temperature-difference driving force and heat flows from the high to the low

temperature region.(10)

The fundamental modes of heat transfer are:

Conduction or diffusion:

The transfer of energy between objects that are in physical contact .

Convection:

The transfer of energy between an object and its environment, due to

circular fluid motion.

Radiation:

The transfer of energy to or from a body by means of the emission or

absorption of electromagnetic radiation.

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Mass transfer:

The transfer of energy from one location to another as a side effect of

physically moving an object containing that energy.

1.2.1Thermal Conductivity

Heat transfer by conduction involves transfer of energy within a material

without any motion of the material as a whole. The rate of heat transfer depends

upon the temperature gradient and the thermal conductivity of the material.

Thermal conductivity is a reasonably straightforward concept when you are

discussing heat loss through the walls of your house, and you can find tables

which characterize the building materials and allow you to make reasonable

calculations.

Conceptually, the thermal conductivity can be thought of as the container for the

medium-dependent properties which relate the rate of heat loss per unit area to

the rate of change of temperature.

𝛥𝑄

𝛥𝑡= −𝑘𝐴

𝛥𝑇

𝛥𝑥 (1.1)

Where;

𝛥Q/Δt is the rate of heat transfear,

ΔT/Δx is the temperature gradient,

A is the cross sectional area, and

k is thermal conductivity coefficient.

In physics, thermal conductivity, k, is the property of a material's ability

to conduct heat. It appears primarily in Fourier's Law for heat conduction.

Thermal conductivity is measured in watts per kelvin-meter (W·K−1·m−1, i.e.

W/(K·m) Multiplied by a temperature difference (in kelvins, K) and an area (in

square meters, m2), and divided by a thickness (in meters, m), the thermal

Introduction & literature survey Chapter 1

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conductivity predicts the rate of energy loss (in watts, W) through a piece of

material. (11, 12, 13)

The reciprocal of thermal conductivity is thermal resistivity

1.2.1.1Some related Definitions

a. Thermal Conductance

For general scientific use, thermal conductance is the quantity of heat

that passes in unit time through a plate of particular area and thickness when its

opposite faces differ in temperature by one kelvin. For a plate of thermal

conductivity k, area A and thickness L this is kA/L, measured in W·K−1

(equivalent to: W/°C). Thermal conductivity and conductance are analogous to

electrical conductivity (A·m−1

·V−1

) and electrical conductance (A·V−1

).

There is also a measure known as heat transfer coefficient: the quantity of heat

that passes in unit time through unit area of a plate of particular thickness when

its opposite faces differ in temperature by one Kelvin. The reciprocal is thermal

insulance. In summary:

thermal conductance = kA/L, measured in W·K−1

o thermal resistance = L/(kA), measured in K·W−1

(equivalent to:

°C/W)

heat transfer coefficient = k/L, measured in W·K−1

·m−2

o thermal insulance = L/k, measured in K·m²·W−1

.

The heat transfer coefficient is also known as thermal admittance.

Introduction & literature survey Chapter 1

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b. Thermal Resistance

When thermal resistances occur in series, they are additive. So when heat

flows through two components each with a resistance of 1 °C/W, the total

resistance is 2 °C/W.

A common engineering design problem involves the selection of an appropriate

sized heat sink for a given heat source. Working in units of thermal resistance

greatly simplifies the design calculation. The following formula can be used to

estimate the performance:

c. Thermal Transmittance

A third term, thermal transmittance, incorporates the thermal

conductance of a structure along with heat transfer due to convection and

radiation. It is measured in the same units as thermal conductance and is

sometimes known as the composite thermal conductance. (14)

1.2.1.2 Theoretical consideration for thermal conductivity

measurement

There are a number of ways to measure thermal conductivity. Each of these

is suitable for a limited range of materials, depending on the thermal properties

and the medium temperature.

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a. STEADY-STATE METHOD

Determination of the thermal conductance of a sample is a solid-state

transport property measurement in which a temperature difference (ΔT) across a

sample is measured in response to an applied amount of heating power. This is

essentially a measure of the heat flow through the sample. The thermal

conductivity (k) is given by the slope of a power versus (ΔT) sweep at a fixed

base temperature with the dimensions of the specific sample taken into

account(15)

.

𝑘 =𝑄𝐿

𝐴𝛥𝑇 (1.2)

Where k: is total thermal conductivity.

Q: is the quantity of heat flowing through the sample.

A: is the cross sectional area through which power flows

ΔT: is the temperature difference measured.

b. THE COMPARATIVE TECHNIQUE

In the comparative technique a known standard is put in series between the

heater and the sample. This technique, also a steady-state heat flow technique,

achieves the best results when the thermal conductivity of the standard is

comparable to that of the sample.

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c .THE RADIAL FLOW METHOD

In the radial heat flow method, heat is applied internally to the sample,

generally minimizing radiative losses from the heat source. As presented by

Tye, (16)

radial flow methods have been applied to solids having a wide range of

thermal conductivities.

d. LASER-FLASH DIFFUSIVITY

Another technique for measuring the thermal properties of thin-film and

bulk samples is the laser-flash thermal diffusivity method. (17)

In this technique

one face of a sample is irradiated by a short (≤1 ms) laser pulse. An IR detector

monitors the temperature rise of the opposite side of the sample. The thermal

diffusivity is calculated from the temperature rise versus time profile.

Algorithms exist for correcting various losses typically present in this

measurement. The thermal conductivity is related to the thermal diffusivity, D =

k/ρd Cp, where ρd is the density, and Cp is the heat capacity.

e. Transient methods (KD2PRO Theory)

The transient techniques perform a measurement during the process of

heating up. The advantage is that measurements can be made relatively quickly.

Transient methods are usually carried out by needle probes.

Non-steady-state methods to measure the thermal conductivity do not require

the signal to obtain a constant value. Instead, the signal is studied as a function

of time. The advantage of these methods is that they can in general be performed

more quickly, since there is no need to wait for a steady-state situation. The

disadvantage is that the mathematical analysis of the data is in general more

difficult.

Introduction & literature survey Chapter 1

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Carlaw and Jaeger

(18), modeled the temperature surrounding an infinite line heat

source with constant heat output and zero mass, in an infinite medium. When a

quantity of heat Q (J/m) is instantaneously applied to the line heat source, the

temperature rise at distance, r(m)from the source is

𝛥𝑇 = (𝑄/4𝛱𝑘𝑡)𝑒(−𝑟2/4𝐷𝑡) (1.3)

Where k: is the thermal conductivity (W/mK),

D: is the thermal diffusivity (m2/s) and,

t: is time (s).

if a constant amount of heat is applied to a zero mass heater over a period of

time, rather than as an instantaneous pulse, the temperature response is

𝛥𝑇 = 𝑞

4𝛱𝑘𝑡 𝐸𝑖(−

𝑟2

4𝐷𝑡) 0 < t ≤t1 (1.4)

Where q: is the rate of heat dissipation (W/m),

t 1 : is the heating time,

Ei: is the exponential integral (19)

.

The temperature rise after the heat is turned off is given by

𝛥𝑇 = 𝑞

4𝛱𝑘𝑡 (𝐸𝑖 −

𝑟2

4𝐷𝑡 + 𝐸𝑖 −

𝑟2

4𝐷(𝑡−t1) t > t1 (1.5)

Material thermal properties are determined by fitting the time series temperature

data during heating to eq. (1.4), and during cooling to eq. (1.5). Thermal

conductivity can be obtained from the temperature of the heated needle (single

needle), with r taken as the radius of the needle. Diffusivity is best obtained by

fitting the temperature measured a fixed distance from the heated needle (k is

also determined from this data). Volumetric specific heat (W/m3K) is

determined from K& D

Introduction & literature survey Chapter 1

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𝐶 = 𝑘/𝐷 (1.6)

In each case, k & D are obtained by anon linear least squares procedure (20)

which searches for values of k and D which minimize the difference between

modeled and measured sensor temperatures. An additional linear drift factor is

included in the inverse procedure.

The theory introduced above is based on heat flow from an infinite line heat

source. For the analytical solution just given to accurately describe the physical

behavior of a system, the heat source must closely approximate an infinitely

long, thin line. Kluitenberg et al (21)

give solutions for pulsed cylindrical sources

that are not ideal line heat sources.

1.2.2Heat capacity

Heat capacity (usually denoted by a capital C, often with subscripts), or

thermal capacity, is the measurable physical quantity that characterizes the

amount of heat required to change a body's temperature by a given amount. In

the International System of Units (SI), heat capacity is expressed in units of

joules per kelvin.

𝐶 = 𝑄/∆𝑇 (1.7)

Derived quantities that specify heat capacity as an intensive property,

independent of the size of a sample, are the molar heat capacity, which is the

heat capacity per mole of a pure substance, and the specific heat capacity, often

simply called specific heat, which is the heat capacity per unit mass of a

material.

For many experimental and theoretical purposes it is more convenient to report

heat capacity as an intensive property, as an intrinsically characteristic property

Introduction & literature survey Chapter 1

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of a particular substance. This is most often accomplished by the specification of

the property per a unit of mass. In science and engineering, such properties are

often prefixed with the term specific.(22)

International standards now recommend

that specific heat capacity always refer to division by mass.(23)

The units for the

specific heat capacity are

𝐶 = 𝐽/𝐾𝑔.𝐾 (1.8)

1.2.3Density

Is a physical property of matter, as each element and compound has a

unique density associated with it. Density defined in a qualitative manner as the

measure of the relative "heaviness" of objects with a constant volume.

Mathematical Definition of Density

The formal definition of density is mass per unit volume. Usually the

density is expressed in grams per mL or cc. (cc is a cubic centimeter) and is

equal to a mL Therefore, (24)

𝜌 =𝑚

𝑣 (1.9)

Where ρ: is density in Kg/m3

m: is mass in Kg

V: is volume in m3

Relative Density (Specific Gravity)

Introduction & literature survey Chapter 1

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Relative density of a substance is the ratio of the substance to the density of

water at 4oC.

1.2.4Specific Weight

Specific Weight is defined as weight per unit volume. Weight is a force.

y= ρ g (1.10)

Where

y : specific weight (N/m3)

ρ :density (kg/m3)

g : acceleration of gravity (m/s2)

1.3 literature survey for thermal properties

Saxena et al (25)

studied Thermal conductivity of styrene butadiene rubber

compounds with natural rubber prophylactics waste as filler

Efforts on a large

scale have been made by the polymer industry to develop cost effective

techniques to convert waste and used rubber into processable forms. Some of the

authors have developed a cost effective technique for the reuse of natural rubber

(NR) latex condom waste as potential filler in styrene butadine rubber (SBR). It

has been proved that waste NR particles do reinforce SBR matrix. For

optimizing cryo system performance of the blends, characterization of the

composites in terms of thermal behavior is important. Thermal conductivity of

SBR filled with lightly cross-linked NR latex waste is measured using the

transient plane source (TPS) method in the temperature range of 100±300 K. It

has been found that the thermal conductivity of SBR composites increases

Introduction & literature survey Chapter 1

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linearly with temperature to a peak value at a temperature which lies well within

the glass transition region of SBR. With further increase of temperature the

thermal conductivity decreases asymptotically to a constant value near 300 K. It

has been found that the thermal conductiveness of the SBR composites falls to a

minimum at 10 phr of NR particle content and further addition of NR particles

results in compensating this fall in thermal conductivity due to the decrease in

cross linking density of the composites with increasing filler content.

Leong et al (26) studied Mechanical and thermal properties of talc and

calcium carbonate filled polypropylene hybrid composites they compare the

mechanical and thermal properties of hybrid polypropylene (PP) composites

and single-filler PP composites. With two main types of mineral fillers—

calcium carbonate (CaCO3) and talc—PP composites of different filler weight

ratios (talc/CaCO3) were compounded with a twin-screw extruder and then

injection-molded into dumbbell specimens with an injection-molding machine.

Tensile, flexural, and impact tests were performed to determine and compare

the mechanical properties of the hybrid and single-filler PP composites. A

synergistic hybridization effect was successfully achieved; the flexural strength

and impact strength were highest among the hybrids when the PP/talc/CaCO3

weight ratio was 70:15:15. The nucleating ability of the fillers and its effects on

the mechanical properties were also studied with differential scanning

calorimetry. Because of the influence of talc as the main nucleating agent, the

hybrid fillers showed significant improvements in terms of the nucleating

ability, and this contributed to the increase in or retention of the mechanical

properties of the hybrid composites.

Goyanes et al(27)

studied Thermal properties in cured natural

rubber/styrene butadiene rubber blends Blends of natural rubber (NR) and

Introduction & literature survey Chapter 1

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styrene butadiene rubber (SBR) were prepared with sulfur and n-t-butyl-2-

benzothiazolesulfonamide (TBBS) as accelerator, varying the amount of each

polymer in the blend. Samples were analyzed by rheometer curing at 433 K until

their maximum torque was reached. The miscibility among the constituent

polymers of the cured compounds was studied in a broad range of temperatures

by means of differential scanning calorimetry, analyzing the glass transition

temperatures of the samples. The specific heat capacity of the compounds was

also determined. Thermal diffusivity of the samples was measured in the

temperature range from 130 to 400 K with a new device that performs

measurements in vacuum. In NR/SBR blends prepared with TBBS(accelerator)/

sulfur and vulcanized at 433 K, there is not aunique glass transition temperature

measured with DSC. Two glass transitions are obtained, each one corresponding

to each phase of the blend. These temperatures are not the same in all the blends.

The thermal diffusivity was measured in the NR/ SBR cured blends and its

variation with temperature shows clearly the transition zone. However, it was

not possible to distinguish the Tg of each phase.. A serial thermal conduction,

model considering the weight fraction of each elastomer and their thermal

diffusivity, can be used to explain the thermal diffusivity of the blend in the

transition and glassy zones.

Yesilata et al (28)

studied Thermal insulation enhancement in concretes by

adding waste PET and rubber pieces they investigated experimentally the

relative change in insulation property of the ordinary concrete due to adding

polymeric based waste material. The polyethylene (PET) bottle and automobile

tire pieces, which can easily be obtained from the environment with almost no

cost, are shredded and added into ordinary concrete to examine heat insulation

behaviors of specimens. Five different concrete samples (one ordinary concrete,

one concrete with scrap rubber pieces and three concretes with waste PET bottle

Introduction & literature survey Chapter 1

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pieces of various geometries) are considered. The adiabatic hot-box technique is

used for comparing

effective thermal transmittances of these concrete samples. The results reveal

that proper addition of selected waste materials into concrete can significantly

reduce heat loss or improve thermal insulation performance. The degree of

improvement in thermal insulation is found to vary with the added waste

material and geometry of shredded-pieces.

Wooster et al (29)

studied Thermal, mechanical, and conductivity

properties of cyanate ester composites ,Cyanate ester resins have been widely

proposed as replacements for epoxy resins in high temperature applications. One

such application, semiconductor encapsulation, uses a large amount of inorganic

filler, typically 65 wt%. The effect of filler incorporation, on the properties of

cyanate ester composites, was assessed incrementally in this work. It was found

that, as is the case with epoxy based encapsulants, silica filler increased cyanate

ester composite thermal conductivity, Young’s modulus, and dielectric constant

(slightly), and decreased encapsulant thermal expansion. It was also found that

silica addition resulted in a marginal decrease in strength. This indicated a high

degree of interfacial adhesion between the untreated silica filler and the cyanate

ester matrix.

Agari et al(30)

studied Thermal conductivity of polymer filled with

carbon materials they measured Effect of conductive particle chains on thermal

conductivity Thermal and electric conductivities of polyethylene and poly(vinyl

chloride) filled with carbon materials over a wide range in order to study the

effect of formed conductive particle chains on thermal conductivities of the

composites. With increase of content of carbon particles, the amount of formed

conductive chains exponentially increases and the conductive chains tend

largely to increase thermal conductivity of a composite. Some models proposed

Introduction & literature survey Chapter 1

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to predict thermal conductivity of a composite in a two-phase system could not

be applied to the system with high volume content of particles. In this study, a

new thermal conduction model is proposed to correctly predict thermal

conductivity of a composite which contains various amounts of particles ranging

from a small content, to the region in which conductive chains largely effect a

thermal conductivity of a composite. Thermal conductivity of a polymer filled

with high volume content of particles largely decreased with a rise in

temperature. This phenomenon can be referred to as a PTC phenomenon in

thermal resistance.

Sarkhel et al (31)

deals with the mechanical, thermal and viscoelastic

properties of ternary composites based on low density polyethylene (LDPE)-

ethylene-propylene-diene terpolymer (EPDM) blend and high density

polyethylene (HDPE)-EPDM blend reinforced with short jute fibers. For all the

untreated and compatibilizer treated composites, the variation of mechanical and

viscoelastic properties as a function of fiber loading (10, 20 and 30 wt %) and

compatibilizer concentration (1, 2, and 3%) were evaluated. The flexural

strength, flexural modulus, impact strength, and hardness increased with

increasing both the fiber loading and the compatibilizer dose. The storage

modulus (E ) and loss modulus (E ) of the HDPE-EPDM/jute fiber composites

were recorded higher compared to those of the LDPE-EPDM/jute fiber

composites at all level of fiber loading and compatibilizer doses. The tan

(damping efficiency) spectra showed a strong influence of the fiber loading and

compatibilizer dose on the relaxation process of polymer matrix in the

composite. The thermo-oxidative stability was significantly enhanced for treated

composites compared to untreated composites. Scanning electron microscopy

investigation confirmed that the higher values of mechanical and viscoelastic

Introduction & literature survey Chapter 1

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properties of the treated composites compared to untreated composites is caused

by improvement of fiber-matrix adhesion as result of compatibilizer treatment.

Eiermann, et al (32)

made a Systematic measurements of the thermal

conductivity of plastics by various methods and checked against each other.

Between −180 and +100°C. The thermal conductivity depends only slightly on

the temperature. For instance, amorphous plastics and natural rubber show a

break in the curve at the second-order transition temperature. This break

probably is connected with the break in the volume versus temperature curve. In

stretched samples, the thermal conductivity was found to be larger when

stretching was in a direction parallel than perpendicular to the chains. Partially

crystalline plastics show a more complex behavior.

Najidha, et al (33)

they investigated the thermal transport properties of

Natural Rubber/Polyaniline and Natural Rubber/Polyaniline/Carbon black

composites by Transient Plane Source (TPS) Technique at room temperature.

The samples of different weight percentage (typically 20,30,40,50 and 60%) of

fillers have been taken. The composites were prepared by dry mill mixing in a

roll-mill and vulcanized in a hot press. It has been found that the effective

thermal conductivity and effective thermal diffusivity of the both the composites

increase as the fraction of filler increases.