CHAPTER I
INTRODUCTION
A.
Background of the Study
Plastics have been one of the most important materials used by people nowadays.
Almost all things we have today are made of plastics. They are used as packaging
materials, furniture, plastic wares, and also in gadgets.
Plastics have brought big changes to us. With improving technology, they have
now become lightweight and more durable. However, without proper waste disposal, they
have caused severe problems to the society. One reason is that they are nonbiodegradable and it will take hundreds or thousands of years before plastics can be fully
decomposed. Tons and tons of garbage are accumulated every day. To ease this problem,
bioplastics have been developed in the industry. They are made from organic polymers,
unlike plastics which are made from synthetic polymer. They are also biodegradable.
Polymers are made up of long chain of molecules which can be usually found in the
starchy foods we eat like sweet potato. Bioplastics which are polymers have now been
extensively used as a food packaging material.
Sweet potato is a fleshy, edible root crop and is usually grown here in the
Philippines. Sweet potatoes are high in dry matter and a good source of energy, carotene,
niacin, thiamine, riboflavin, and starch makes up the nutritive reserves of certain
2
minerals. It is used usually as food for people, feeds for livestock and as raw material for
the manufacture of starch and alcohol.
This study is conducted to produce bioplastics from sweet potato. Using
bioplastics to replace some of the inorganic plastics can be a solution to solve global
warming and reduce pollution. With this solution in mind, the researchers are encouraged
to pursue study on bioplastics.
B.
Statement of the Problem
Main Problem:
The potential of sweet potato as bioplastic.
Sub – Problems:
1.
2.
What are the properties of different samples of bioplastics in terms of:
a.
color
b.
texture
c.
elasticity
d.
tensile strength
e.
biodegradability
Is there a significant difference among the different samples of bioplastics in
terms of its properties except biodegradability?
3
C.
Hypotheses of the Study
1.
There is no significant difference among the different samples of bioplastics
in terms of its properties except biodegradability.
D.
Significance of the Study
Petroleum plastics or petroplastic products create major environmental and
economic burdens. They create air, land, and water pollutions in our environment. There
are over 200 million tons of plastics around the world and are rapidly increasing. If this
kind of plastic is still used by the people for generations, pollution will increase and will
produce more toxic gases that can erase the ozone layer on the earth’s atmosphere which
causes the greenhouse effect.
This study helps us to reduce the pollutants in our environment that can cause this
unwanted situation in the future. Through this study, this will be able to help other people
in decreasing the use of petroleum plastics and maximizing the use of biodegradable
plastic products. Bioplastics could be an effective solution to all of these problems. They
are a much better choice than petroplastics because they are friendlier to the earth and the
environment. These kinds of plastics break down faster, and are nontoxic. With these
characteristics of biodegradable plastics, we could help save lives and the environment as
well and reduce the threat plastics give to marine life. Bioplastics from natural materials,
such as root crop derivatives, sequester CO2 during the phase when they're growing, only
to release CO2 when they're decomposing, so there is no net gain in carbon dioxide
emissions. Biodegradable plastics have a potential to minimize the pollution in our
environment and preserving earth for the next nth generations.
4
E.
Scope and Limitations of the Study
This study focuses on the production of bioplastics using sweet potato starch
extracted from the uncooked and cooked flesh and uncooked and cooked peelings.
Methods used were extraction of starch and addition of glycerin and vinegar. The set-up
was composed of four samples were the biodegradability, color, elasticity, tensile
strength and texture were assessed. Spring balance and Vernier caliper was used to
measure the tensile strength while a ruler was added to measure elasticity. In the
biodegradability setup in soil, it was assumed that the plastic was thrown away and thus
different weather conditions are beyond the controls of the researcher. The production of
bioplastic was conducted in a household kitchen. Most of the materials needed are
accessible which were bought in any supermarket except for the glycerin which was
bought at Edmar Marketing, Iligan City. The investigator limited this research to the
production of bioplastics from sweet potato only.
F.
Definition of Terms
Acid Hydrolysis
This is one of the methods of improving the
functional properties of native starch that imparts
better physical properties and for this study, vinegar
will be used.
Bioplastic
The final product formed and was evaluated. In this
study sweet potato starch was used as the main
component.
5
Biodegradability
This is the physical disintegration of bioplastics.
This test was conducted for a month and data was
obtained weekly through series of qualitative
description of the plastic. Different weather
conditions were beyond the control of researchers.
Color
It is the physical appearance imparted by the
bioplastic samples and most likely a light brown or
brown appearance.
Elasticity
The maximum stretch it could withstand without
breaking when stress is applied. A ruler was used to
measure the elasticity.
Glycerin
This is a water-soluble, clear, almost colorless,
odorless, viscous, hygroscopic liquid with a high
boiling point. This was used to improve the
properties of the bioplastic.
Plasticizers
These are small molecules that do not bind with the
polymer that disrupts the crystallinity of the
polymer and disrupts the polymer-polymer bonding
structure, which is what causes the macroscopic part
to become "softer." In this study, glycerin was used.
Starch
It is the white layer formed at the bottom of the
container after extracting. When dried, it turns into
powder.
6
Sweet Potato
This is the main subject used in the study. Starch
was extracted from it to make bioplastic.s
Texture
One of the physical properties that was evaluated. It
is the “feel” of the sample.
Tensile Strength
The maximum load that each bioplastic sample
could withstand. This was measured using a spring
balance.
Vinegar
This is a versatile liquid that is created from the
fermentation of ethanol. It was added to the
bioplastics for acid hydrolysis.
CHAPTER II
REVIEW OF RELATED LITERATURE
The sweet potato (Ipomoea batatas), or the camote, is a tuberous-rooted perennial
usually grown annually. It is adaptable and can grow under many different ecological
conditions. It has a shorter growth period than most other tuber crops (three to five
months) and under suitable climatic conditions, it shows no marked seasonality. Sweet
potatoes are high in dry matter (typically 30%) and a good source of energy, carotene,
niacin, thiamine, riboflavin, and starch makes up the nutritive reserves of certain minerals
(International Starch Institute, 2006).
Camote is one of the most important root crop in the Philippines. It is used as
food for man, as feeds for livestock and as a raw material for the manufacture of starch
and alcohol (Santiago & Rodrigo, 1958). Considering about the non-culinary uses of
sweet potato, the juice of red sweet potato can be used as a dye for cloth when mixed
with lime juice (“Non-culinary Uses of Sweet Potato”, 2011).
Sweet potato contains starch. Starch makes up the nutritive reserves of many
plants. It constitutes the major part of the carbohydrate – the rest made up of mono- and
disaccharides in particular maltose and saccharose. Typical starch content is twenty-two
percent (22%). Starch is excellent for modifying the texture of many processed and home
– cooked foods and has also been used for centuries for other purposes, including the
manufacture of paper, glue or fabric stiffener (Goodman, 2010). Polysaccharides are
8
carbohydrate polymers consisting of tens to hundreds to several thousand
monosaccharide units. All of the common polysaccharides contain glucose as the
monosaccharide unit. Starch can be separated into two fractions -- amylose and
amylopectin. Natural starches are mixtures of amylase (10 – 20%) and amylopectin (80 –
90%) (Ophardt, 2003). Starch is a polymer made by plants (Polymer Science Learning
Center, 2003). Polymers are molecules that consist of a long, repeating chain of smaller
units called monomers. They have the highest molecular weight among any molecules,
and may consist of billions of atoms. Polymers are not always straight chains of regular
repeating monomers; sometimes, they consist of chains of varying length or even chains
that branch in multiple directions (Anissimov, 2012).
Biodegradable plastics, commonly are plastics that can be broken down by
microorganisms (bacteria or fungi) into water, carbon dioxide (CO2) and some biomaterial (Scimeca, n.d.). They are environmentally friendly because, compared with
traditional plastics, their production results in the emission of less carbon dioxide, which
is thought to cause global warming (Japan Echo Inc., 2003). Bioplastics are manufactured
using biopolymers which offer a renewable and sustainable alternative to oil-based
plastics or petroplastics. The manufacturing process produces fewer greenhouse- gas
emissions than that of petroleum - based plastics, and these biomaterials don't contain an
allegedly hormone-disrupting chemical, that same regular plastics do.
In principle plastics are valued for their ability to make strong, durable products.
Biodegradability should therefore be regarded as an additional functionality when the
application demands a cheap way to dispose of the item after it has fulfilled its job.
9
Biodegradability is a material property that depends much on the circumstances of the
biological environment (Scimeca, n.d.).
Bioplastics are a form of plastics derived from renewable biomass sources, such
as vegetable oil, corn starch, pea starch or microbiota, rather than traditional plastics
which are derived from petroleum. They are used either as a direct replacement for
traditional plastics or as blends with traditional plastics. All bio-based and petroleumbased plastics are technically biodegradable, meaning they can be degraded by microbes
under suitable conditions (“Biodegradable Cutlery”, 2008). Several starch-based plastics
have been introduced into the market, and are used in some applications now. Starch
foam is one of the major starch-based packaging materials. It is produced by extrusion or
compression/explosion technology. This product has been developed as a replacement for
polystyrene which is used to produce loose-fillers and other expanded items. Another
type of starch-based plastics is produced by blending or mixing starch with synthetic
polyester. For this type of biodegradable plastics, granular starch can be directly blended
with polymer, or its granular structure can be destructurized before being incorporated
into the polymer matrix. The type of starch and synthetic polymer as well as their relative
proportions in the blends influence the properties of the resulting plastics. The last group
of starch-based plastics is polyesters that are produced from starch. The major starchderived polyesters in the market now are polylactic acid and polyhydroxyalkanoate
(Sriroth, & Sangseethong, 2006). The advantages of starch for plastic production include
its renewability, good oxygen barrier in the dry state, abundance, low cost and
biodegradability. The longstanding quest of developing starch-based biodegradable
plastics has witnessed the use of different starches in many forms such as native granular
10
starch, modified starch, plasticized starch and in blends with many synthetic polymers,
both biodegradable and nonbiodegradable, for the purpose of achieving cost effectiveness
and biodegradation respectively. In this regard, starch has been used as fillers in starchfilled polymer blends, thermoplastic starch (TPS) (produced from the combination of
starch, plasticizer and thermomechanical energy), in the production of foamed starch and
biodegradable synthetic polymer like polylactic acid (PLA) with varying results.
(Fabunmi, Tabil, Panigrahi, & Chang, 2007).
Acid Hydrolysis has been shown to be one of the methods of improving the
functional properties of native starch. It affects both the physical and chemical nature of
starch and improves its suitability for both pharmaceutical and nonpharmaceutical use. It
imparts better physical properties (flow, compressibility and compactibility) to native
starch and makes it amenable to direct compression (Olorunsola, Isah, & Allagh, 2011).
Vinegar is a versatile liquid that is created from the fermentation of ethanol. The key
ingredient is acetic acid, which gives it an acidic taste, although there may be additions of
other kinds of acid like tartaric and citric. The typical pH of vinegar ranges from 2 to 3.5.
In food preparation procedures, it is a multipurpose product as an ingredient and
condiment. Outside of cooking, vinegar has medicinal, household cleaning, and
agricultural applications. The slow fermentation process takes weeks to months and
occurs naturally. At the same time, a nontoxic slime called mother of vinegar
accumulates in the liquid. Composed of acetic acid bacteria and cellulose, mother is also
available in stores and consumed by some despite its unappetizing appearance (Chen,
2012).
11
Plasticizers are small molecules that do not bind with the polymer. It disrupts the
crystallinity of the polymer and disrupts the polymer-polymer bonding structure, which is
what causes the macroscopic part to become "softer". Plasticizers are added to some
types of plastic, to make them more flexible. The plasticizer material is simply mixed
with the plastic and forms a sort of "alloy", not unlike what happens when two different
metals are mixed. The base polymer does not change chemically. Typically, a plasticizer
works by fitting between the long chains of a polymer's molecules, and causes them to
separate slightly. This reduces the strong attraction between polymer chains, and results
in increased flexibility (Skipor, n.d.).
Physically, glycerin is a water-soluble, clear, almost colorless, odorless, viscous,
hygroscopic liquid with a high boiling point. Chemically, glycerin is a trihydric alcohol,
capable of being reacted as an alcohol yet stable under most conditions. At low
temperatures, glycerin tends to supercool, rather than crystallize. Water solutions of
glycerin resist freezing, a property responsible for glycerin’s use as permanent antifreeze
in cooling systems. It is virtually nontoxic in the digestive system and non – irritating to
the skin and sensitive membranes, except in very high concentrations when a dehydrating
effect is noted. It is also odorless and has a warm sweet taste (The Soap and Detergent
Association, n.d.).
Marzo & Duhaylungsod (2012), conducted a study on Bioplastics from Cassava
(Manihot esculenta). Acid hydrolysis and addition of plasticizer has been also used to
come up with a bioplastic. They evaluated the bioplastic in terms of color, odor, and
texture.
CHAPTER III
METHODOLOGY
A.
Research Design
This research was conducted to come up with a potential bioplastic product from
sweet potato starch. Sweet potato (Ipomoea batatas) or camote starch extracted from
uncooked and cooked flesh and uncooked and cooked peelings was used as main
ingredient. Vinegar was used for acid hydrolysis and glycerin as plasticizer to enhance
flexibility of the bioplastic product. The finished product was assessed in terms of color,
texture, elasticity, tensile strength, and biodegradability.
B.
Materials and Equipment
Materials

4 trays

Strainer

Bowl

Sweet potato

Grater

Measuring cup

Frying pan

Measuring spoon

Spatula

Ruler

Stove

2 pots
13
Equipment

Analytical balance

Spring balance

Grinder

Vernier caliper

8 tsp vinegar
Chemicals
C.

2 cups water

40 g sweet potato flesh starch

8 tsp glycerin

40g sweet potato peelings starch
Experimental Setup
Table 1. Composition of the Different Samples of Bioplastic from Sweet potato
starch
COMPONENTS
SAMPLES
Source of starch
A
B
C
D
Sweet potato starch (grams)
20
20
20
20
Vinegar (tsp)
2
2
2
2
Glycerin (tsp)
2
2
2
2
Water (cups)
2
2
2
2
Type of preparation
14
D.
General Procedure
Preparation of Materials
Thirty (30) kilos of fresh sweet potatoes was bought at Pala-o Market, Iligan City.
These were washed thoroughly with tap water. One (1) kilo was used as uncooked flesh,
another one (1) kilo as cooked flesh. Fifteen (15) kilos was used as uncooked peelings
and the other fifteen (15) kilos will be used as cooked peelings. One (1) liter of glycerin
was bought at Edmar Marketing, Iligan City.
Extraction of Starch
Half of the sweet potatoes was boiled for about fifteen (15) minutes. The sweet
potatoes were then peeled off. The uncooked and cooked sweet potato peelings were
soaked in a bowl of water separately. The cooked and uncooked sweet potato flesh was
grated using a grater in separate bowls and this was then soaked in a bowl of water
separately. Using a strainer, the uncooked and cooked flesh and peelings was then
squeezed into a bowl to extract the starch. The filtered liquid was left for about ten (10)
minutes to let the starch to settle. A white layer was formed at the bottom of the container
indicating that the starch has already settled. The liquid was then decanted into another
container leaving the starch. The container with the starch was sun dried until it turns to
powder.
Confirming Tests on Presence of Starch
Production of Bioplastic
Four (4) trays was prepared for which the bioplastics was placed labeled as
Sample A, Sample B, Sample C, and Sample D. Sample A as uncooked flesh, Sample B
as uncooked peelings, Sample C as cooked flesh, and Sample D as cooked peelings.
15
Twenty (20) grams of starch, two (2) teaspoons of vinegar and two (2) cups of water was
used for each sample. The four different samples was cooked at 190oC using a non-stick
pan. The mixture was stirred the whole time until it becomes sticky and bubbles started
coming out. After which, it was then poured into the tray. It was then sun dried for about
three (3) days.
Product Evaluation
Biodegradability, color, elasticity, tensile strength, and texture were assessed by
the researchers. Each sample was cut into nine (9) equal sizes; six (6) was used for
biodegradability test and the other three (3) was used for tensile strength and elasticity
test. Color and texture was tested through sensory evaluation.
In biodegradability, each four (4) samples were placed on the soil and were also
exposed in the air. Each sample was composed of six (6) bioplastics with equal sizes;
three was put on the soil and the other three was exposed in the air. Data was gathered
every week for one month. These were assessed through sensory evaluation.
Elasticity and tensile strength were done simultaneously. Using a spring balance,
each sample was then tested. Each sample was composed of three (3) trials. The initial
length of each bioplastic will be measured first. The cross-sectional area of each
bioplastic was measured first using a Vernier caliper. While stress is being exerted on the
bioplastic, the length of elongation in centimeters was measured before it will break using
a ruler for elasticity and the amount of force exerted for tensile strength. The same
16
procedure was done to the other samples. The succeeding tables show how the elasticity
and tensile strength were recorded.
Table 2. Tensile Strength of Bioplastics
Samples
Trials
1
A
2
Uncooked Sweet Potato Flesh
3
Mean
1
B
2
Uncooked Sweet Potato Peelings
3
Mean
1
C
2
Cooked Sweet Potato Flesh
3
Mean
1
D
2
Load (N)
Cross
Sectional
Area (m2)
Tensile Strength
(Pa = N/m2)
17
Cooked Sweet Potato Peelings
3
Mean
Table 3. Elasticity of Bioplastics
Samples
Trials
1
A
2
Uncooked Sweet Potato
Flesh
3
Mean
1
B
2
Uncooked Sweet Potato
Peelings
3
Mean
1
C
2
Cooked Sweet Potato Flesh
3
Mean
1
Stress
(N/m2)
Initial
Length
(m)
Final
Length
(m)
Elongation
(m)
Strain
Young’s
Modulus
(E =N/m2)
18
D
2
Cooked Sweet Potato
Peelings
3
Mean
The following formula will be used to test the tensile strength and elasticity of the
bioplastics:
1.
Tensile Strength. This is the maximum load that each bioplastic sample could
withstand. The formula for finding this is:
TS 
2.
Load
Area
Elasticity. This is the maximum stretch it could withstand without breaking when
stress is applied. The formula for finding this is.
E
Stress
Strain
Strain 
L
Li
Where Stress is the tensile strength, ΔL is the elongation, and Li is the initial
length.
E.
Statistical Tools Used for Data Analysis
Data was gathered and analyzed using t-test through Megastat. T-test was used to
compare if there is a significant difference between bioplastics in terms of its properties:
elasticity and tensile strength.
Formula for t-test:
t
( x1  x 2 )  ( 1   2 )
s12 s 22

n1 n2
19
Where
x1 = mean of Sample A
s12 = variance of Sample A
x 2 = mean of Sample B
s 22 = variance of Sample B
1 = population mean of Sample A
n1 = number of subjects in Sample A
 2 = population mean of Sample B
n 2 = number of subjects in Sample B
Peeling of Sweet Potato
Grating of Sweet Potato
Extraction of Starch
Drying of Starch
Production of Bioplastic
Drying of Bioplastic
20
Testing and Evaluation
Figure 1. Methodology Flowchart
CHAPTER IV
RESULTS AND DISCUSSIONS
This chapter talks about the comparison on the physical properties, tensile
strength, elasticity and biodegradability of the bioplastics coming from the starch
obtained from uncooked sweet potato flesh, uncooked sweet potato peelings, cooked
sweet potato flesh, and cooked sweet potato peelings.
Table 4. Comparison of Physical Properties of Bioplastics coming from Different
Sources of Sweet Potato Starch
Characteristics
Samples
A
B
C
D
Odor
Sour Smell
Sour Smell
X
X
Texture
Rough
Rough
X
X
Table 4 shows the comparison of physical properties of bioplastics coming from
different sources of sweet potato starch.
Sample A came from uncooked sweet potato flesh and Sample B came from
uncooked sweet potato peelings. Sample C came from cooked sweet potato flesh and
Sample D came from cooked sweet potato peelings.
A difference in the source of starch in Samples A and B only affects the color
between the two physical characteristics assessed.
22
No data was obtained from Samples C and D due to no starch can be obtained
from cooked sweet potato.
Table 5. Mean Tensile Strength of Bioplastics from Uncooked Sweet Potato Flesh
and Peelings
Samples
A
Uncooked Sweet Potato Flesh
B
Uncooked Sweet Potato Peelings
Trials
Load
(N)
Area
(m2)
Tensile Strength
(Pa = N/m2)
Mean
8.591
1.22917E-05
726,804.678
Mean
6.207
1.04167E-05
639,191.919
Table 6 shows the mean tensile strength of bioplastics from uncooked sweet
potato flesh and peelings. The table shows that the mean tensile strength for Sample A is
726,804.678 Pa which appears to be higher than the mean tensile strength of Sample B
which is 639,191.919 Pa. This implies that the bioplastic made from sweet potato flesh is
much stronger than the bioplastics made from sweet potato peelings.
Table 6. Mean Elasticity of Bioplastics from Uncooked Sweet Potato Flesh and
Peelings
Samples
Trials
Stress
(N/m2)
Initial
Final
Length Length Elongation
(m)
(m)
(m)
Strain
Young’s
Modulus
(E = N/m2)
A
Uncooked Sweet
Potato Flesh
Mean 726,804.678
0.06
0.069
0.009
0.156 5,109,754.386
Mean 639,191.919
0.06
0.068
0.008
0.139 5,311,515.152
B
Uncooked Sweet
Potato Peelings
The table above shows the elasticity of bioplastics from uncooked sweet potato
flesh and peelings. Result shows that the mean elasticity for Sample A is 5,109,754.386
23
N/m2 which is slightly lower than the mean elasticity of Sample B which is
5,311,515.152 N/m2. This means that the bioplastic made from uncooked sweet potato
peelings is more elastic than the bioplastic made from uncooked sweet flesh.
Table 7. Hypothesis Testing for Tensile Strength of Bioplastic from Uncooked Sweet
Potato Flesh and Peelings using T-test
Samples
n
Mean
Std. Dev.
A
3
726,804.678
253,781.545
B
3
639,191.919
222,719.326
t-value
p-value
0.45
.6764
α = 0.05
The table shows the comparison of tensile strength of bioplastics made from
uncooked sweet potato starch flesh and peelings using T-test. Sample A has a mean of
726,804.678 with a standard deviation of 253,781.545. Sample B has a mean of
639,191.919 and a standard deviation of 222,719.326. With a t-value of 0.45 and a
corresponding p-value of .6764, at α = 0.05, the null hypothesis is not rejected. This
implies that the mean for tensile strength of bioplastics made from uncooked sweet potato
flesh and uncooked sweet potato peelings are statistically the same. This means that a
bioplastic made from uncooked sweet potato flesh has no significant difference with
bioplastic made from uncooked sweet potato peelings in terms of tensile strength.
24
Table 8. Hypothesis Testing for Elasticity of Bioplastic from Uncooked Sweet Potato
Flesh and Peelings using T-test
Samples
n
Mean
Std. Dev.
A
3
5,109,754.386
3,085,392.677
B
3
5,311,515.152
3,311,961.459
t-value
p-value
-0.08
.9422
α = 0.05
The table above shows the comparison for elasticity of bioplastic from uncooked
sweet potato flesh and peelings. Sample A has a mean of 5,109,754.386 and a
corresponding standard deviation of 3,085,392.677. Sample B has a mean of
5,311,515.152 with a corresponding standard deviation of 3,311,961.459. With a t-value
of -0.08 and a corresponding p-value of 0.9422, the null hypothesis is not rejected at α =
0.05. This implies that the mean for elasticity of bioplastics are statistically the same.
This means that the bioplastic made from uncooked sweet potato flesh does not differ
with bioplastic made from uncooked sweet potato peelings in terms of elasticity.
Figure 2. Sample ABiodegradability of flesh in soil
(week 4)
Figure 3. Sample BBiodegradability of peeling in
soil (week 4)
The figures above show the biodegradability in soil of bioplastics for uncooked
sweet potato flesh and peelings. Each sample was not conducted at the same time.
Sample A shows a sign of rapid disintegration as compared to Sample B. During the first
25
week, Sample A encountered a very cold and rainy weather and Sample B experienced
slight rain. Based upon the remarks, different weather conditions affect the rate of
biodegradability.
Figure 4. Sample ABiodegradability of flesh
exposed on air (week 4)
Figure 5. Sample BBiodegradability of peelings
exposed on air (week 4)
The figures above show the biodegradability (suspended in the air) of bioplastics
from uncooked sweet potato flesh and peelings. Both Samples A and B showed no signs
of being degraded but they possessed molds. In Sample A, the molds occurred during the
first week in all the three trials while in Sample B, the molds occurred during the third
week already.
CHAPTER V
CONCLUSION AND RECOMMENDATION
A.
Summary
This study aimed to produce biodegradable plastic using sweet potato starch. It
also aimed to compare the quality of the biodegradable plastic obtained from uncooked
sweet potato flesh, uncooked sweet potato peelings, cooked sweet potato flesh, and
cooked sweet potato peelings in terms of texture, color, tensile strength, elasticity, and
biodegradability. It sought to determine whether the bioplastic made from the four types
of sub-sources (flesh and peelings-uncooked and flesh and peelings-cooked) of sweet
potato do have significant difference or not and do these bioplastic have the potential in
replacing or substituting conventional plastics in the market.
Below are the summaries of findings:
1.
In Sample A which is from uncooked sweet potato flesh, had an average tensile
strength of 726,804.678 N/m2 while in sample B, from uncooked sweet potato
peelings, had an average tensile strength of 639,191.919 N/m2. This implies that
the bioplastic made from sweet potato flesh is stronger than the biodegradable
plastic made from sweet potato peelings.
2.
In terms of elasticity, the bioplastic of Sample A, from uncooked sweet potato
flesh, had an elasticity of 5,109,754.386 N/m2 while Sample B, from uncooked
sweet potato peelings, was 5,311,515.152 N/m2. This means that the
27
biodegradable plastic made from uncooked sweet potato peelings is more elastic
than the biodegradable plastic made from uncooked sweet potato flesh.
3.
Bioplastic made from uncooked sweet potato flesh has no significant difference
with bioplastic made from uncooked sweet potato peelings in terms of tensile
strength and elasticity.
4.
The difference in the weather conditions is one factor that greatly affects the
biodegradability in soil of bioplastics. Specifically, a cold and rainy weather deals
much greater effect as compared to a hot and dry weather. Bioplastics made from
uncooked sweet potato flesh easily gets molds as compared to bioplastics made
from uncooked sweet potato peelings for the biodegradability exposed in the air.
B.
Conclusion
With the study conducted, it is found that bioplastic made from sweet potato flesh
is stronger than the bioplastic made from sweet potato peelings in terms of tensile
strength. Furthermore, bioplastic made from uncooked sweet potato peelings is more
elastic than the bioplastic made from uncooked sweet potato flesh. On the other hand,
bioplastic made from uncooked sweet potato flesh has no significant difference with
bioplastic made from uncooked sweet potato peelings in terms of tensile strength and
elasticity. With the quality of the bioplastic produce, bioplastic from sweet potato can be
a good alternative to plastic sold commonly in the market.
28
C.
Recommendations
Based on the results, the researchers would like to recommend further studies
relating to this study which includes the following:

Using other sources other than root crops which may contain starch like fruits,
vegetables or any parts of a plant which is a possible source for starch.

Conduct biodegradability test for more than one month. If possible try to have a
detailed observation like noting the kind of weather and measuring the
temperature of surroundings which might affect the rate of biodegradability. It can
also be that the weather is controlled and each bioplastics will be weigh when
gathering data to determine if there is a decrease on the weight.

Varying the amounts of components of bioplastic and subjecting to different tests
to come up with a desirable bioplastic that could be a possible substitute for
commercial plastics.
29
REFERENCES
Book:
Santiago, A., & Rodrigo, P. (1958) 1837 Singalong St., Malate, Maynila, JONEF
Publications. Our Plants Our Wealth.
Journal:
Olorunsola, E.O., Isah, A.B. & Allagh. (2011, March). “Effects of varying
conditions of acid hydrolysis on some physicochemical properties of
Ipomoea batatas starch.” Nigerian Journal of Pharmaceutical Sciences, 9,
73-80. Retrieved from http://www.abu.edu.ng/journals/njps/pdf/94.pdf
Related Studies
Marzo, S. & Duhaylungsod L. (March 2012). Bioplastics from Cassava (Manihot
eculenta), A Research Paper, IDS, MSU-IIT. Retrieved October 16, 2012.
Website:
Annisimov (2012) What are polymers?. Retrieved September 13, 2012, Retrieved
from http://www.wisegeek.com/what-are-polymers.htm
Biodegradable Cutlery (2011, March 31) Retrieved September 13, 2012 from
30
http://biodegradableplastics.wordpress.com/2008/08/09/biodegradable-cutlery/
Chen, Y. (2012) What is vinegar? Retrieved September 13, 2012, Retrieved from
http://www.wisegeek.com/what-is-vinegar.htm
Goodman, S. (2010, April 29). Starch: a structural mystery. Retrieved September
11, 2012. Retrieved from
http://www.scienceinschool.org/2010/issue14/starch
International Starch Institute. (n.d.). Sweet potato starch production. Retrieved
July 23, 2012. Retrieved from
http://www.starch.dk/isi/papers/TM22-3e%20sweet%20potato.pdf
Japan Echo Inc. (2003). Trends in Japan. Bioplastic - Eco-Friendly Material Has
a Bright Future (2003, December 16) Retrieved September 13, 2012 from
http://web-japan.org/trends/science/sci031212.html
Olayide O. Fabunmi, Lope G. Tabil Jr., Satyanarayan Panigrahi and Peter R.
Chang, (2007, October 12) Developing Biodegradable Plastics from
starch, 2007, Retrieved September 13, 2012 from
http://www.ageng.ndsu.nodak.edu/ASABE/RRV/Papers_files/RRV07130.pdf
31
Ophardt, C. (2003). Starch. Retrieved July 22, 2012, Retrieved from
http://www.elmhurst.edu/~chm/vchembook/547starch.html
Polymer Science Learning Center (2003). Starch. Retrieved September 13, 2012,
Retrieved from
http://www.pslc.ws/macrog/kidsmac/starch.htm
Scimeca, S. (n.d.). FuturEnergia. Biodegradable plastics: are they better for the
environment? Retrieved September 13, 2012 from
http://www.futurenergia.org/ww/en/pub/futurenergia/chats/bio_plastics.htm
Skipor, A. (2012) Newton and Ask a Scientist (n.d.). Polymers and Plasticizer.
Retrieved July 20, 2012 from
http://www.newton.dep.anl.gov/askasci/mats05/mats05215.htm
Sriroth, K. and Sangseethong, K. 2006. BIODEGRADABLE PLASTICS FROM
CASSAVA STARCH. Retrieved September 13, 2012 from
http://www.actahort.org/books/703/703_16.htm
Non-culinary uses of sweet potato. (2011) Retrieved September 11, 2012.
Retrieved from
http://sweetsp.com/sweetsp-site-offering-complete-information-sweet.html
32
The Soap and Detergent Association (n.d.). Glycerine: an overview. Retrieved
July 22, 2012. Retrieved from
http://www.aciscience.org/docs/Glycerine_-_an_overview.pdf
33
APPENDIX A
Pictures
Figure 6. Washed Sweet Potato
Figure 9. Gathered Sweet Potato Flesh
(grated)
Figure 7. Peeled Sweet Potato
Figure 10. Addition of Water to the
Grated Sweet Potato Flesh
Figure 8. Grating of Sweet Potato Flesh
Figure 11. Extraction of Starch
34
Figure 12. Filtering the Liquid and
Figure 15. Wet Starch
Extracting the Starch
Figure 13. Letting the Starch to Settle
after Filtering
Figure 16. Dried Starch
Figure 17. Gathering sweet potato
peelings
Figure 14. Decanting the Liquid after
Letting the Starch to settle at the Bottom
35
Figure 18. Grinding the sweet potato
Figure 21. Dried Starch (peelings)
peelings
Figure 22. Set-up for Making Bioplastic
Figure 19. Grinded peelings
Figure 23. Mixing of all the Components
Figure 20. Same process--soaking,
decanting, drying
in the Mixture
36
Figure 24. Cooking the Bioplastic
Figure 27. Cooked Bioplastic Mixture
Ready for Drying
Figure 25. Bioplastic Mixture becomes
Thick and Sticky indicating that it is
Figure 28. Trials from sample A for
almost done
tensile strength test
Figure 26. Pouring the Cooked
Figure 29. Trials from sample A for
Bioplastic Mixture into the tray
elasticity test
37
Figure 30. Trials from sample A for
Figure 33. Trials from sample B for
biodegradability test (soil)
elasticity test
Figure 34. Trials from sample B for
Figure 31. Trials from sample A for
biodegradability test (soil)
biodegradability test (suspended)
Figure 35. Trials from sample B for
Figure 32. Trials from sample B for
tensile strength test
biodegradability test (suspended)
38
Figure 39. Biodegradability Set-up for
Figure 36. Conducting Tensile strength
Uncooked Sweet Potato Peelings
and elasticity test of sweet potato flesh
Figure 40. Week 1 Biodegradability Test
in soil (Flesh)
Figure 37. Conducting Tensile strength
and elasticity test of sweet potato
peelings
Figure 41. Week 2 Biodegradability Test
in soil (Flesh)
Figure 38. Biodegradability Set-up for
Uncooked Sweet Potato Flesh
39
Figure 42. Week 3 Biodegradability Test
Figure 45. Week 2 Biodegradability Test
in soil (Flesh)
in soil (Peelings)
Figure 43. Week 4 Biodegradability Test
Figure 46. Week 3 Biodegradability Test
in soil (Peelings)
(Flesh)
Figure 44. Week 1 Biodegradability Test
in soil (peelings)
Figure 47. Week 4 Biodegradability Test
in soil (Peelings)
40
Figure 48. Week 1 Biodegradability Test
Figure 51. Week 4 Biodegradability Test
exposed on air (Flesh)
exposed on air (Flesh)
Figure 49. Week 2 Biodegradability Test
exposed on air (Flesh)
Figure 52. Week 1 Biodegradability Test
exposed on air (Peelings)
Figure 50. Week 3 Biodegradability Test
exposed on air (Flesh)
Figure 53. Week 2 Biodegradability Test
exposed on air (Peelings)
41
Figure 54. Week 3 Biodegradability Test
exposed on air (Peelings)
Figure 55. Week 4 Biodegradability Test
exposed on air (Peelings)
42
APPENDIX B
Data Gathered During Experimentation
Table 11. Cross-Sectional Area of Bioplastics
Trials
Length (m)
Width / Thickness
(m)
Area (m2)
1
0.02
0.00075
0.000015
A
2
0.0165
0.00075
0.000012375
Uncooked Sweet Potato Flesh
3
0.019
0.0005
0.0000095
Mean
0.0185
0.000666667
1.22917E-05
1
0.025
0.00055
0.00001375
B
2
0.021
0.0005
0.0000105
Uncooked Sweet Potato Peelings
3
0.02
0.00035
0.000007
Mean
0.022
0.000466667
1.04167E-05
Samples
Table 12. Tensile Strength of Bioplastics from Uncooked Sweet Potato Flesh and
Peelings
Trials
Load
(N)
Area
(m2)
Tensile Strength
(Pa = N/m2)
1
9.702
0.000015
646,800
A
2
6.468
0.000012375
522,666.667
Uncooked Sweet Potato Flesh
3
9.604
0.0000095
1,010,947.368
Mean
8.591
1.22917E-05
726,804.678
1
6.86
0.00001375
498,909.091
B
2
5.488
0.0000105
522,666.667
Uncooked Sweet Potato Peelings
3
6.272
0.000007
896,000
Mean
6.207
1.04167E-05
639,191.919
Samples
43
Table 13. Elasticity of Bioplastics from Uncooked Sweet Potato Flesh and Peelings
Trials
Stress
(N/m2)
Initial
Length
(m)
Final
Length
(m)
Elongation
(m)
Strain
Young’s
Modulus
(E = N/m2)
1
646,800
0.06
0.071
0.011
0.183
3,528,000
A
2
522,666.667
0.06
0.07
0.01
0.167
3,136,000
Uncooked Sweet
Potato Flesh
3
1,010,947.368
0.06
0.067
0.007
0.117
8,665,263.158
Mean
726,804.678
0.06
0.069
0.009
0.156
5,109,754.386
1
498,909.091
0.06
0.072
0.012
0.2
2,494,545.455
B
2
522,666.667
0.06
0.067
0.007
0.117
4,480,000
Uncooked Sweet
Potato Peelings
3
896,000
0.06
0.066
0.006
0.1
8,960,000
Mean
639,191.919
0.06
0.068
0.008
0.139
5,311,515.152
Samples
44
Table 14. Biodegradability (soil) of Bioplastic from Uncooked Sweet Potato Flesh
and Peelings
Samples Trials
Week 1
Biodegradability (soil)
Remarks
Week 2
Rolled Edges
with Big Holes
Week 3
Week 4
Rolled Edges
with Big Holes
Disintegrated
Slightly
Disintegrated
Very Much
Disintegrated
Much
Disintegrated
Very Much
Disintegrated
Extremely
Disintegrated
Extremely
Rolled Edges
with Medium
Holes
Rolled Edges
with Big Holes
Disintegrated
Slightly
Disintegrated
Very Much
1
Rolled Edges
with Small Holes
Rolled Edges
with Medium
Holes
Disintegrated
Slightly
2
Rolled Edges
Rolled Edges
with Small Holes
Rolled Edges
with Big Holes
3
Rolled Edges
Rolled Edges
Rolled Edges
1
A
Uncooked
Sweet Potato
Flesh
2
3
B
Uncooked
Sweet Potato
Peelings
45
Table 15. Biodegradability (suspended in the air) of Bioplastic from Uncooked
Sweet Potato Flesh and Peelings
Samples Trials
Biodegradability (suspended in the air)
Remarks
Week 1
Week 2
Week 3
No signs of
being degraded
but with molds
Week 4
1
No signs of
being degraded
but with molds
No signs of
being degraded
but with molds
No signs of
being degraded
but with molds
2
No signs of
being degraded
but with molds
No signs of
being degraded
but with molds
No signs of
being degraded
but with molds
No signs of
being degraded
but with molds
3
No signs of
being degraded
but with molds
No signs of
being degraded
but with molds
No signs of
being degraded
but with molds
No signs of
being degraded
but with molds
1
No signs of
being degraded
No signs of
being degraded
No signs of
being degraded
but with molds
2
No signs of
being degraded
No signs of
being degraded
No signs of
being degraded
but with molds
3
No signs of
being degraded
No signs of
being degraded
No signs of
being degraded
but with molds
A
Uncooked
Sweet Potato
Flesh
B
Uncooked
Sweet Potato
Peelings
46
Table 16. Hyptohesis Testing for Tensile Strength of Bioplastics using T-test
Hypothesis Test: Independent Groups (t-test, pooled variance)
Sample A
726,804.678363
253,781.544535
3
Sample B
639,191.919192
222,719.326458
3
4
87,612.7591707
57,004,485,362.0397000
238,756.1210986
194,943.5565526
0
0.45
.6764
mean
std. dev.
n
df
difference (Sample A - Sample
B)
pooled variance
pooled std. dev.
standard error of difference
hypothesized difference
t
p-value (twotailed)
Table 17. Hyptohesis Testing for Elasticity of Bioplastics using T-test
Hypothesis Test: Independent Groups (t-test, pooled variance)
Sample A
5,109,754.385965
3,085,392.676865
3
Sample B
5,311,515.151515
3,311,961.458899
3
4
-201,760.7655502
10,244,368,337,843.3000000
3,200,682.4800101
2,613,346.3015635
0
-0.08
.9422
mean
std. dev.
n
df
difference (Sample A - Sample
B)
pooled variance
pooled std. dev.
standard error of difference
hypothesized difference
t
p-value (twotailed)
47
CURRICULUM VITAE
Full Name: Frederick Irving L. Rico
Nickname: Rick, Rico
Religion: Born again Christian
Birthdate: February 16, 1997
Father’s Name: Cristito C. Rico
Mother’s Name: Adelaida L. Rico
Address: Purok 6, First river, Pala-o, Iligan City
Contact Number: +639056473470
Educational Background
Elementary
Name of School: Dona Juana Actub Lluch Memorial Central School
Address: Pala-o, Iligan City
Secondary
Name of School: MSU-IIT Integrated Developmental School
Address: A. Bonifacio Avenue, Tibanga, Iligan City
48
CURRICULUM VITAE
Name: Mike Martin C. Diangco
Nickname: Martin, Macmac
Religion: Roman Catholic
Birthdate: November 13, 1997
Father’s Name: Felix A. Diangco
Mother’s Name: Emma C. Diangco
Address: Purok 12, Barangay Santiago, Iligan City
Contact Number: 09265241018 / 222-0483
Educational Background
Elementary
Name of School: Iligan City East Central School (ICECS)
Address: Tambo, Iligan City
Secondary
Name of School: MSU-IIT Integrated Developmental School
Address: Andres Bonifacio Ave., Tibanga, Iligan City