I. TITLE OF PROJECT

Multi-Walled Carbon Nanotube Synthesis from Waste HDPE for the Production of

Molybdenum-MWCNT Reinforced Corrosion Resistant and Strength Enhancing Epoxy

Coating

II. BACKGROUND

Plastics play an important role in our daily life. They are used in clothing, housing,

automobiles, aircraft, packaging, electronics, signs, recreation items, and medical implants.

Due to their superior properties and low production cost, global production have increased by

6 % (15 million tonnes to 265 million tonnes) from the year 2009 to 2010, confirming the

long term trend of plastics production growth of almost 5% per year over the past 20 years

(Plastics Europe Market Research Group (PEMRG)).

Plastics are any of a large group of materials of high molecular weight that usually

contain a synthetic or semi-synthetic organic substance made by polymerization or

condensation. They are made of compounds and thermoplastic resins that reduce the overall

weight of the product making them suitable for use in different areas, namely packaging.

Plastic packaging of materials are mostly used for only a short span of time therefore

producing waste. In the Philippines, approximately 10.67 million tons to 14.05 million tons

of waste plastics were generated on the year 2000 to 2010 demonstrating periodic increase in

the trend of waste generation (The World Bank Philippine Environment Monitor 2001).

Different countries have been studying ways to improve plastic end-of-life

management. Though plastic waste generation problems are now being addressed through

recovery, energy recovery and recycling, 42.1 % of total waste generation of plastic, still end

up on landfills (Consultic, 2010). In response to this, researchers continue to struggle for a

way not only to recycle plastics but also to up cycle them.

Up cycling is the process of converting waste materials to valuable products. In

earlier years, up cycling of plastics was done only by burning plastics to produce fuel.

Current researches, however, found a way to convert waste polyethylene plastic bags into

carbon materials – carbon nanotubes (Pol, 2010).

Carbon nanotubes (CNTs) are very thin lightweight hollow tubes made up of carbon

atoms. A carbon nanotube is like a sheet of graphite that is rolled into a cylinder, with

distinctive hexagonal latticework making up the sheet. Carbon nanotubes are extremely

small; the diameter of one carbon nanotube is one nanometer, which is one ten-thousandth

(1/10,000) the diameter of a human hair. Carbon nanotubes are classified according to their

structures: single-wall nanotubes (SWNTs), double-wall nanotubes (DWNTs), and multi-

wall nanotubes (MWNTs) which have individual properties that make the nanotubes

appropriate for different applications (Johnson).

Carbon nanotubes can be produced from waste High Density Polyethylene (HDPE),

a sturdy and reliable non-leaching translucent plastic, which is widely used in bottles of milk,

juice, shampoo and laundry products. Statistics show that 12% of the total amount of plastics

produced account for HDPE (PEMRG). CNTs produced from HDPE have higher yield as

compared to waste Low Density Polyethylene (LDPE). HDPE feedstock yields highly

graphitic tubes. Conversely, LDPE feedstock yields semi-graphitic tubes which are mixtures

of ordered and disordered carbon nanotubes (Pol and Thiyagarajan).

Carbon nanotubes, due to its unique mechanical, electrical, and thermal properties, as

well as corrosion resistant properties, can be applied in different industries—corrosion

resistance and strength being the focus of this paper.

Corrosion is defined as the destruction or deterioration of a material by direct

chemical or electrochemical reaction with their environment (McFarland). It is a naturally

occurring phenomenon that can cause dangerous and expensive damage- $2.2 trillion, the

annual cost of corrosion worldwide accounting to over 3% of the world’s GDP (World

Corrosion Organization).

Corrosion affects everything from storage tanks, pipelines, bridges, public buildings,

vehicles, water and wastewater systems, and even home appliances. Storage tanks, the

subject of interest of this study, are usually made of steel, a material highly susceptible to

corrosion. Corrosion-related damage is accelerated by factors including the tank’s interaction

with interconnected components, corrosive environmental conditions, and stray electric

currents. Over time, uncontrolled corrosion can weaken or destroy components of the tank

system, resulting in holes or possible structural failure, and release of stored products into the

environment. Corrosion poses serious consequences to materials worldwide. It causes waste

of valuable resources, loss or contamination of product, reduction in efficiency, costly

maintenance, and expensive overdesign. It can also jeopardize safety and inhibit

technological progress. Though it is a natural process that cannot be prevented, intervention

with the correct measures can control it. These control measures include the addition of

corrosion inhibitors.

 Corrosion inhibitors are compounds which reduce the rate at which corrosion occurs,

and block early corrosion damage. They can be applied to the material by alloying or by

adding it to the material coating. Existing coating technology however, experience common

failures that eventually lead to corrosion of the coated material. This includes chalking,

blistering, algae & fungi growth, and crating (Building & Construction Authority).

Studies concerning a new series of corrosion control coating containing CNTs is

being developed and made available for end-user sampling. These coatings have enhanced

strength and electrical conductivity due to the inclusion of CNTs, while also incorporating

sacrificial metal particles (e.g., Zn, Al, Mg) for corrosion inhibition via cathodic protection.

CNTs allow sacrificial metal-filled primers to be formulated at much reduced metal content

as compared to traditional systems.

The new hybrid coating technology combines superior physical performance

properties as a barrier coating with a high degree of cathodic protection as a sacrificial

coating. The resulting nanocoating primer provides the foundation for a coating system that

can deliver corrosion protection to a multitude of steel or aluminum surfaces—everything

from fuel storage tanks and bridges to aircraft and ships.

Molybdenum is a refractory metal recognized for its excellent strength at high

temperatures. Molybdates, are non-toxic and are less aggressive oxidants than chromates

toward organic additives that may be used in corrosion inhibiting formulations. Molybdates

are used to inhibit corrosion in water-based hydraulic systems and in automobile engine anti-

freeze.

Modern corrosion control combines historically proven methods with state-of-the-art

technology to prevent tanks from deteriorating. Corrosion-control strategies are used

individually or in combination with one another. Common strategies include corrosion-

resistant materials, application of coatings and/or linings as a barrier to the environment,

various forms of cathodic protection to prevent deterioration of tank components in contact

with the soil, and use of inhibiting chemicals in stored substances to control corrosion of the

tank interior. Though, corrosion resistant materials such as Hastelloy, Inconel and Monel

display superior corrosion inhibiting abilities, their expensive price limit their use.

Due to the aforementioned disadvantage, the research aims to produce a cheap and

effective Molybdenum- Carbon Nanotube (Mo-MWCNT) based epoxy coating with

corrosion resistant and strength enhancing capabilities.

III. OBJECTIVES, RESEARCH QUESTIONS AND HYPOTHESES

The study generally aims to up cycle waste High Density Polyethylene plastics

through the production of Mo-MWCNT reinforced corrosion resistant and strength

enhancing epoxy coating. Specifically, it aims to answer the following problems:

1. What is the production ratio of MWCNT to waste high density polyethylene plastic?

2. Is there a significant difference between purified and unpurified MWCNT in terms of

their corrosion resistant and strength-enhancing characteristics?

Hypothesis: There is a significant difference between the purified and unpurified

MWCNT in terms of their corrosion resistant and strength-enhancing characteristics.

3. Is there a significant difference between pure MWCNT and Mo-MWCNT as epoxy

coating additive in terms of their corrosion resistant and strength-enhancing

characteristics?

Hypothesis: There is a significant difference between the CNT and Mo-CNT in terms

of their corrosion resistant and strength-enhancing characteristics.

4. What ratio of Mo-MWCNT to epoxy coating gives best results with respect to

corrosion-resistant and strength- enhancing properties when applied to aluminum

alloy?

5. Is there a significant difference between the Mo-MWCNT reinforced epoxy coated

aluminum alloy and the control metal (316SST) in terms of their corrosion resistant

and strength characteristics?

Hypothesis: There is a significant difference between Mo-MWCNT reinfirced epoxy

coated aluminum alloy and the control metal (316SST) in terms of their corrosion

resistant and strength characteristics.

6. Is there a significant difference between the Mo-MWCNT reinforced epoxy coated

aluminum alloy and the control epoxy coated aluminum alloy in terms of their

corrosion resistant and strength characteristics?

Hypothesis: There is a significant difference between Mo-MWCNT reinforced epoxy

coated aluminum alloy and the control epoxy coated aluminum alloy in terms of their

corrosion resistant and strength characteristics.

IV. SIGNIFICANCE

Plastic has become the most common material since the beginning of the 20th century

and modern life. Plastic is useful due to its durability, light weight and low cost at the same

time problematic considering its long life span which takes years for the item to decompose.

This becoming a global issue, researchers are finding a way to reduce the volume of waste

plastics.

Recycling plastics has been one way to reduce waste plastics, though up cycling is a

better option. Waste plastics have been found not only as a source of energy but also as a

source of carbon. Being a source of carbon, researchers used plastic bags to make Carbon

Nanotubes(CNTs).

Carbon nanotubes exhibit properties such as strength and corrosion resistance greater

than other materials. These properties make it a possible additive in the coating used in

industrial tanks such as storage tanks and reactors to enhance its corrosion resistance and

strength properties.

Corrosion problems worldwide are becoming severe with direct annual costs over

$400 billion per year in the US alone. Though current corrosion inhibitors as well as

corrosion resistant materials are commercially available, they are expensive and still pose

problems.

Recent studies regarding CNT-based coatings for corrosion-control applications

generate significant interest within the industry but despite having superior characteristics as

compared to normal epoxy coatings, CNT based coatings are affected by common reasons

for failure of coatings. One of which is due abrasion or impact which removes or damages

the coating therefore creating corrosion site within the material. In response to this, the

research reinforced the coating with Molybdenum to enhance its strength.

In line with the above concerns, this research aims to produce a Molybdenum-Multi-

walled Carbon Nanotube reinforced Epoxy Coating which is cheaper, and more lightweight

than conventional chemical coating and gives corrosion resistant and strength enhancing

properties to industrial storage tanks and reactors.

V. RESEARCH DESIGN AND METHODOLOGY

This study is an experimental research. It aims to investigate the possible cause-and-

effect relationship between research parameters and is accomplished by manipulating,

controlling, and quantifying variables by statistical means.

Variables, namely the ratio of Mo- MWCNT to Epoxy and duration of soaking in

corrosion testing, are manipulated in this research to determine their effect on the properties

of Mo- MWCNT reinforced epoxy coating in terms of its corrosion resistance and strength

enhancing properties. Comparison of the Mo-MWCNT reinforced epoxy coating to the

commercially available 316 SST and the control epoxy coating was also employed.

This study involved the following: collection of waste high density polyethylene

plastics, preparation of catalyst, synthesis of MWCNT, purification of MWCNT, synthesis of

Mo-MWCNT, synthesis of reinforced Mo-MWCNT Epoxy Coating, preparation of metal

specimens, corrosion inhibition testing, and tensile strength testing.

The waste high density polyethylene plastics were washed with water, oven dried,

and reduced into small size. The catalyst was mixed with the substrate forming a composite

which was then placed and heated in a muffle furnace at 850 °C. Half of the prepared

composites were purified. Purified and unpurified carbonaceous nanomaterial were mixed

with Ammonium Molybdate and placed in an oven at 180 °C for 48 hours. Mo-MWCNT

Epoxy Coating were done through dispersion under ultrasonic system. Characterization of

MWCNT, Mo-MWCNT and Mo-MWCNT—Epoxy was done in SEM and FTIR. The test

media were prepared Testing

Data Gathering Tools

Every procedure in the experiment was performed in the Chemical Engineering

Laboratory(I and II) , Natural Sciences Research Unit and in Environmental Research

Laboratory at Saint Louis University. The aluminum alloy sheets which were used as test

specimens were cut and drilled at the Mechanical Engineering Laboratory.

This research is made possible through various sources including books, documents,

articles journals, and previous researches. Several related documents were also obtained

using the internet. Through the help of these aids, factual details were obtained and utilized

in this study.

Data Gathering Procedures

A. Collection of Raw Material

Waste high density polyethylene plastics were collected from the households around

the city of Baguio. The plastic materials were washed, and reduced into small size. The

plastics were then initially air-dried.

B. Preparation of Catalyst

The Ni/Mo/MgO catalyst was prepared by a combustion method. Ethylene glycol,

was used in this work as a combustion additive and to dissolve the metal salts. The right

amounts of Mg(NO3)2•6H2O, (NH3)6Mo7O24•4H2O, Ni(NO3)2•6H2O were dissolved in

Ethylene glycol to yield the molar ratios Mg/Mo/Ni/Ethylene glycol = 1.0/1.2/0.1/1.0. The

solution was subsequently placed in a muffle heated at 650 °C for 10 minutes. Finally,

faintly green, foamy materials were obtained and ground to fine powders.

C. Synthesis of Multi-walled Carbon Nanotubes

The catalyst was mixed with the substrate to form a composite. The composite was

then placed in a crucible and heated in a muffle furnace at 850 °C for 5 min. After cooling to

room temperature the produced black powder materials were obtained and ground to fine

powders.

D. Purification of Multi-walled Carbon Nanotubes

In purification of the sample, the raw material was first heated under an air

atmosphere at 400 °C for 2 hours and then stirred in dilute HCl to remove the catalyst. The

sample was finally washed with deionized water and dried in oven.

E. Carbon Nanotubes characterization through Scanning Electron Microscopy (SEM)

The nanostructure and morphology of CNTs were observed under scanning electron

microscopy.

F. Carbon Nanotubes characterization through Electrical Conductivity

Approximately 4 mg of the carbonaceous nanomaterials was dissolved in 20 mL of

methanol assisted by sonication. The solution was then transferred to a beaker and

evaporated at a temperature of 40 to 45 °C. A layer covering the whole bottom of the beaker

was formed and its conductivity across the diameter measured using a two probe diameter

and a standard digital multimeter.

G. Synthesis of Ammonium Molybdate- Multi-walled Carbon Nanotubes

100 mg carbon nanotube with 10 mL deionized water and homogenized about 5

minutes by an ultrasonic system. Then 20 mL of saturated solution of ammonium molybdate

hepta hydrate was prepared. Both prepared solutions was mixed and transferred to a vessel

which was sealed and placed for 48 hours in an oven at 180 °C. The precipitate was filtered,

rinsed, dried, and then analyzed.

H. Mo-MWCNT characterization through Fourier Transform Infrared (FTIR)

The binding of Multiwalled Carbon Nanotubes and molybdenum were observed using the

Fourier Transform Infrared System.

I. Preparation of Mo-MWCNT – Epoxy Nanocomposites Solution

For the preparation of the colloidal solution, 1% and 1.5% wt Mo-MWCNT were added

to the epoxy. The solution was then subjected to an ultrasonic system for 24 hours.

J. Preparation of Test Media

4000ml each of 2N HCl and 2N H2SO4 solutions were prepared using analytical grade

HCl, H2SO4 and distilled water. The resulting solutions were kept in stoppered reagent

bottles.

K. Preparation of Metal Specimen

For the samples preparation, the samples were polished with 800 grit sand papers,

degreased with absolute ethanol, sonicated in acetone and distilled water for 5 min. The pre-

treated samples were kept over a hot plate at 200 ºC for 10 min to eliminate the moisture and

entrapped air from the surfaces of substrate.

L. Metal Specimen Coating

Coating was conducted by dipping the aluminum alloy substrates into the Mo-CNT

epoxy coating at ambient temperature and environmental condition.

The aluminum alloy was immersed into the coating for 25 s to allow the wetting. In order

to obtain a stain-free surface, the specimens were slowly pulled out of the solution.

M. Corrosion Testing

The Mo-MWCNT-epoxy coated aluminum alloys were soaked in 2N H2SO4 and 2N HCl

solutions for a period of 1 month. Data were recorded in a daily basis

N. Strength Testing

The strength of the coated aluminum sheet was subjected to tensile test and fatigue test in

order to estimate the additional strength given by the Mo-CNT based epoxy coating.

O. Treatment of Data

After the experimentation was conducted, the data collected were subjected to

computational and statistical analysis.

Percentage Yield

In the determination of percentage yield of HDPE and CNT, the following equation

was used:

Yield= CNT produced

HDPE feedx 100 %

Analysis of variance and Tukey’s Honest Significant Difference Test

In the determination of the existence of a significant difference in the inhibition

efficiencies of the varied concentrations of the extract, the results were statistically

treated using the One- way Analysis of Variance(ANOVA) and Tukey’s Honest

Significant Difference (HSD) Test.