Development of Packaging Film Using Microcrystalline Cellulose and Pro-Oxidative Additive Using Blown Film Technique
©2017
Textbook
57 Pages
Summary
The purpose of this study is to develop a degradable Cellulose based packaging film with improved mechanical properties. A series of Linear Low Density Polyethylene (LLDPE)/Microcrystalline Cellulose composites were prepared by twin screw extrusion with the addition of maleic anhydride grafted polyethylene as compatibilizer and TiO2 as pro-oxidative additives. Polyethylene wax was used as processing aid to ease the blown film process. The film was processed via a conventional blown film machine.
Excerpt
Table Of Contents
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CHAPTER 1
INTRODUCTION
1.1 Introduction
Synthetic polymers have become technologically significant since the
1940s and packaging is one industry that has been revolutionized by oil-
based polymers such as polyethylene (PE), polypropylene (PP),
polystyrene (PS), poly (ethylene terephthalate) (PET) and poly (vinyl
chloride) (PVC). Plastics' versatility allows it to be used in everything
from the simple part, for example plastic bags, bottles and dolls to the
high-tech parts, cars, computer casing, electronic devices casing and many
more. The reason behind multiuse of plastics is unique capability to be
manufactured to meet very specific functional needs for consumers.
Plastics have been found useful in applications ranging from
transportation, packaging, building, Medical appliances, agricultures and
communication as shown. [1]
(Source: https://doi.org/10.1016/j.wasman.2015.11.041)
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Worldwide production of plastics is more than 78 million tons per year and
almost half of that is discarded within a short time, remaining in garbage
deposits and landfills for decades (more than 30 years)[2]. Furthermore,
major application of plastics is in packaging and this situation may
contribute to serious environmental problems. Thermoplastics are widely
used in packaging and fabrication of bottles and films [3] Synthetic
plastics accumulate in nature at a rate of 25 million tons per year and
polyethylene represents 64% of the produced synthetic plastics.
Petrochemical based plastics such as polyolefin, polyesters and polyamides
have been increasingly used as packaging materials because of their
availability in large quantities at low cost and favourable functionality
characteristics such as good tensile and tear strength, good barrier
properties to oxygen and aroma compounds and heat seal ability [4].
However, these plastics are made of petroleum-based materials that are not
readily biodegradable. Synthetic plastics such as polyethylene and
polypropylene have a very low water vapour transmission rate and most
importantly, so that, they are totally non-biodegradable, and therefore lead
to environmental pollution, which pose serious ecological problems.
Polyolefin are not degraded by microorganisms in the environment, which
contributes to their long lifetime of hundreds of years. There has been an
increased interest in enhancing the biodegradability of synthetic plastics by
blending them with low cost natural biopolymers.
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Table 1.1 Main plastics and their applications Plastics Applications
(Source: https://www.researchgate.net/publication/222370742)
Most light weight plastic packaging material is used for a one-time
application and discarded when its useful life is over. These materials are
durable and inert in the presence of microbes thus leading to a long term
performance [5]. Although there has been a lot of new technology and
method in recycling and reducing plastics waste, the number of these
materials is still increasing every year. Replacing plastics to other
materials such as paper and metals is less attractive because of the special
characteristics and economic factors. Recycle of products also has it
limitation such as high cost of operation, besides, the technology of
recycling are still under development.
Many packaging materials do not lend themselves to recycling because of
contamination, and the cleaning necessary prior to recycling can be very
expensive. Biodegradable plastics are plastics that can undergo a
degradation process known as biodegradation. They are defined as plastics
with similar properties to conventional plastic but which can be
decomposed after disposal to the environment by the activity of
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microorganism. It is also defined as plastics with similar properties to
conventional plastics, but it can be decomposed after disposal to the
environment by the activity of microorganisms to produce end products of
CO
2
and H
2
O. [4] Biodegradable plastics provide opportunities for
reducing municipal solid waste through biological recycling to the
ecosystem and can replace the conventional synthetic plastic products. In
addition, it is desirable that these biodegradable polymers come primarily
from agricultural or other renewable resources for a sustainable
environment. Many synthetic materials like polyolefins are not degraded
by microorganisms in the environment, which contributes to their long-life
of hundreds of years [6].
Biodegradation occurs when microorganism such as bacteria and fungi
degrade a polymer in an aerobic and an anaerobic environment, carbon
dioxide, methane and other natural products are derived from the
degradation process. Hence, biodegradation can be stated as the conversion
of the constituents of a polymer to carbon dioxide/methane, microbial
cellular components and miscellaneous by-products, by microorganisms
[7]. Microorganisms break down the polymer chains and consume the
material through several methods. Polyethylene (PE) is one of the mass
produced non-degradable polymers and various types of PE are used
extensively in many fields, including agricultural and packaging films.
Among the polyolefins, linear low density polyethylene (LLDPE) is more
susceptible to the attack of microorganisms in determined conditions.
LLDPE had been a major use of plastics materials in packaging industries.
Biodegradable polymers are considerably more expensive than competitive
non-biodegradable polymers. New mechanisms for production and
processing of synthetic polymer and natural polymer will be interesting
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alternatives to reduce the cost of biodegradable polymers in the market.
Blending of low density polyethylene with a cheap natural biopolymer
such as cellulose will enhance the biodegradability of this material.
Incorporation of cellulose will accelerate the attack of microorganisms to
LLDPE. Furthermore, cellulose is being a good choice since it is an
abundant and low cost material in the market, so, it will reduce the cost of
production of LLDPE/cellulose biodegradable polymer. Research on
biodegradable plastics based on cellulose began in the 1970s and continues
today at various laboratories all over the world. Cellulose satisfies the
requirements of having adequate thermal stability with minimum
interference of melt properties and negligible disturbance of product
quality and has been considered as a material candidate in certain
thermoplastic applications because it is known biodegradability,
availability and low cost. The excellent physical properties of polyolefin
make them suitable as packaging and film materials. Polyethylene (PE)
blended with cellulose is already found to be a potential candidate to
replace non-degradable thermoplastics in the areas of packaging. Cellulose
is hydrophilic polymer, mainly due to the hydroxyls contains. In contrast,
polyethylene is hydrophobic. Because of this totally different polar
character of the polymers, they are immiscible. Addition of coupling agent
will improve the incorporation of cellulose in LLDPE and also enhancing
the biodegradability of the blends.
Low molecular weight plastic additives like plasticizers and fillers are
usually susceptible to microbial attack. This leads to physical
embrittlement of the polymer, leaving a porous and mechanically
weakened the polymer. The microbes, in turn, release nonspecific
oxidative enzymes that could attack synthetic polymers. Films of
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polyethylene/cellulose blends with compatibilizer were prepared using
blow film extrusion machine. The degradation of the films under thermo
oxidative treatment, ultraviolet light exposure, high temperature, high
humidity and natural ambience (soil burial) were increased. Cellulose are
polymers that naturally occur in a variety of botanical sources and it is a
renewable resource widely available and can be obtained from different
left over of harvesting and raw material industrialization. The
incorporation of cellulose, as naturally biodegradable polymers with
synthetic polymers, such as polyethylene will produce a biodegradable
film with excellent mechanical properties, can be easily process through
polymer processing techniques and biodegradable. However, due to its
poor melt processability, the properties of LLDPE/cellulose blends will be
affected. Plasticizers reduce the brittleness of the film by interfering with
the hydrogen bonding between the lipid and hydrocolloid molecules and
increase film flexibility due to their ability to reduce internal hydrogen
bonding between polymer chains while increasing molecular volume [4].
1.2 Problem Statement
With the growing concern about environmental pollution, the
accumulation of plastics waste needs immediate resolution. Plastics
packaging has become major contribution to accumulation of plastics
waste in landfills. Increasing public concern over dwindling landfill space
and accumulation of surface litter has promoted the development of
degradable plastics. Biodegradable plastics offer one solution to managing
packaging waste. Biodegradable plastics are plastics that can undergo a
degradation process known as biodegradation. Thus, in the last 20-30
years, there has been an increased interest in the production and use of
fully biodegradable polymers with the main goal being replacement of
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non-biodegradable plastics, especially those used in packaging materials.
However, although these polymers possess the required properties and can
be used for the production of blown film, there are not widely used due to
their high cost. Biodegradable polymers are estimated to be four to six
times more expensive than polyethylene and polypropylene, which are the
most widely, used plastics for packaging applications. Therefore, many
research attempts have been focused on the use of natural biopolymers
such as starch, cellulose, lignin and chitin, which are also fully
biodegradable. In addition, these materials are also very cheap and they are
produced from renewable, natural sources [8]. However, due to its poor
properties, these materials are not suitable for most uses in the plastics
industry. Addition of cellulose as a filler in polyethylene blend will
increase the biodegradability of the film and it is suitable for packaging
industry. Cellulose has become a potential use as a matrix for the
development of biodegradable polymers because of its fully biodegradable
properties and low cost of production. Cellulose had been widely studied
by many researchers in edible films and coatings, being used to protect
food products [9].
In this study, maleic anhydride grafted polyethylene will be used as
processing aids to improve the strength of the LLDPE/Cellulose biofilms.
High content of cellulose in the polyethylene blends will enhance the
biodegradability of the LLDPE/cellulose biofilms. Cellulose is susceptible
to microorganisms, thus, when these blends are deposited in the
environment; various microorganisms consume the cellulose, which leaves
the polymer blend in a form which is full of holes. This form enables the
easier disintegration of the material into small pieces. It also increases the
total surface area accessible to oxygen. As a result, the oxidation of
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polyethylene becomes easier. Increasing the amount of cellulose causes a
decrease in both tensile strength and elongation at break. As a result, the
produced materials lose their ability to produce blown films. This decrease
arises from poor adhesion between cellulose and linear low density
polyethylene (LLDPE) due to different polar character of cellulose and
LLDPE [8]. The addition of processing aids will improve the compatibility
between the two materials. Processing aids in LLDPE/cellulose blending
also improve the ability of the material to be process via blow film
technique. Cellulose blended polyethylene films have been reported by
many researchers, but there is lack of literature on their application in food
packaging.
1.3 Objectives of the Study
The main objective of this study is to develop biodegradable low density
polyethylene (LDPE)/cellulose packaging film with enhanced mechanical
properties via blow film extrusion process.
This objective is divided into;
(i) To determine the optimum loading of cellulose in LLDPE/cellulose
blends that can give good mechanical properties for packaging and can be
processed using blow film machine.
(ii) To characterize the mechanical, morphological, thermal properties of
LLDPE/cellulose films before and after they are subjected to
biodegradation tests.
(iii) To investigate the biodegradability of LLDPE/cellulose films.
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1.4 Scopes of the Study
Scopes of this study are;
i). Compounding of LLDPE/ cellulose blends using twin screw extruder
and processability studies on blow film machine. Prior to compounding, all
the ingredients will be mixed using twin screw extruder. Then, the
compounded samples will be blown using blow film machine to study the
effect of it on the processability.
ii). Mechanical properties study of LLDPE/cellulose biodegradable films.
(a) Tensile strength and elongation at break
(b) Water absorption analysis
iii). Characterization of LLDPE/cellulose biodegradable films
(a) Melt flow index analysis after compounding process to investigate its
Suitability for blown film process.
iv. Biodegradation studies of LLDPE/cellulose films
(a) Natural weathering studies
(b) Exposure to fungi environment
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CHAPTER 2
LITERATURE REVIEW
2.1 Plastics and Environment
Plastics are synthetic substances produced by chemical reactions. Almost
all plastics are made from petroleum. "Plastics" earned their name because
they can be moulded, cast, extruded or processed into a variety of forms,
including solid objects, films and filaments. These properties arise from
their molecular structure. Plastics are polymers, very long chain molecules
that consist of subunits (monomers) linked together by chemical bonds.
Plastics, depending on their physical properties, may be classified as
thermoplastic or thermosetting materials. Thermoplastic materials can be
formed into desired shapes under heat and pressure and become solids on
cooling. If they are subjected to the same conditions of heat and pressure,
they can be remoulded. Thermosetting materials acquire infallibility under
heat and pressure and cannot be remoulded. Plastics are widely used,
economical materials characterized by excellent all round properties, easy
moulding and manufacturing. Approximately 140 million tons of synthetic
polymers are produced worldwide each year to replace more traditional
materials, particularly in packaging [10].
Over 60% of post-consumer Plastics waste is produced by households and
most of it as single use packaging. [3]Plastics are manufactured and
designed to resist the environmental degradation and also more economical
than metal, woods and glasses in term of manufacturing costs and energy
required. Due to these issues, plastics resins have become one of the most
popular materials used in packaging. Plastics packaging has a cycle less
than a year and continuously enter the waste stream on a short turnout of
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time. The continuous growing of plastics industries has lead to the increase
volume of plastics waste in the landfill. However, the durability, strength,
low cost, water and chemicals resistance, welding properties, lesser energy
and heavy chemicals requirements in manufacture, fewer atmosphere
emissions and light weight are advantages of plastic materials, cause these
material most preferable especially in packaging industries. Reuse strategy
also has it limitation. Many plastics application are not designed to reuse
because of the impurities and contamination. Food packaging, disposable
diapers, medical appliances and agricultural mulch bags and covers are the
most common plastics products that not suitable for reusing it.
These are examples why plastics waste could be in the waste streams very
fast. Recycling of plastics after final use is possible, but plastic bags, in
particular, are rarely recycled. Furthermore, the technology of sorting,
collecting and recycling the plastics waste is still being developed and will
cost a lot of money. Collecting and sorting used plastics is an expensive
and time-consuming process. While about 27 percent of aluminium
products, 45 percent of paper products and 23 percent of glass products are
recycled in the United States, only about 5 percent of plastics are currently
recovered and recycled. Once plastic products are thrown away, they must
be collected and then separated by plastic type [11]. Most modern
automated plastic sorting systems are not capable of differentiating
between many different types of plastics. If plastic types are not
segregated, the recycled plastic cannot achieve high remoulding
performance, which results in decreased market value of the recycled
plastics.
Details
- Pages
- Type of Edition
- Erstausgabe
- Year
- 2017
- ISBN (PDF)
- 9783960676881
- ISBN (Softcover)
- 9783960671886
- File size
- 1.8 MB
- Language
- English
- Institution / College
- Gujarat University – Central Institute of Plastics Engineering and Technology (CIPET) Ahmedabad
- Publication date
- 2017 (September)
- Grade
- 70.00
- Keywords
- Microcrystalline Cellulose Pro-Oxidative Additives Compatibilizer Bio Degradable Packaging Film Linear Low Density Polyethylene LLDPE
