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    Plastics Replacement by Biomass Substances (Hemp)
    High School Lab Experiments & Background Information
    For Science Labs, Lesson Plans, Class Activities & Science Fair Projects







    This experiment is courtesy of 

    An Alternative to Some Plastics

    Developers:

    Lakshmi Pillalamarri
    University City High School
    Philadelphia, PA

    Eugene Dougherty
    Modifiers Research
    Rohm and Haas Company

     

    Grade Levels:

    9 to 12

     

    Disciplines:

    Biology, Chemistry, Physics, Environmental Science, and Physical Science

     

    Goals:

    A. This project provides students an understanding of how the scientific method is applied to the solution of a scientific problem.

    B. This project gives students an opportunity to see that some plastics [synthetic substances] can be replaced by almost equally efficient biomasses [natural substances]

     

    Specific Objectives:

    Upon completion of these activities the student will be able to:

    1. conduct a controlled scientific experiment
    2. test the tensile strength of the fibers of biomass in comparison to the tensile strengths of polypropylene and tuffal.
    3. test the degradability of the fibers of biomass.
    4. find a best method for preparing paper using biomass.
    5. make a Nitrocellulose using the chosen biomass.

     

    Introduction:

    The following projects developed previously under Project Labs will help students to understand the structure and behavior of different types of plastics.

    1. Polystyrene - 1990 (pages 27 to 28)
    2. Plastics Recycling - 1990 (pages 17 to 20)
    3. Bouncing Balls - 1991 (pages 97 to 99)
    4. Plastics - 1994 (pages 149 to 168)

    To know the effects of plastics on the environment and to recognize a need for finding an alternative to plastics, it is helpful for students to examine the following projects developed previously under Project Labs.

    1. " How Degrading " by Marilyn Krupnick
    2. " Biodegradability. The Elusive Disappearing Act " by Sister John Anne Proach
    3. " 6 Pack Loop Rings Photodegradable? " By Sister Francis Boyle

    This project serves as an extension of the solutions to the scientific problem stated in the above projects.

    Development of plastics began with a search for a satisfactorily substitute for ivory. John Wesley Hyatt (1837-1920) developed a method of pressure working Proxylin a cellulose nitrate of low nitration, that has been plasticized with camphor and alcohol solvent. Patented as celluloid it achieved a notable commercial success. Other plastics were developed gradually over a few decades.

    High strength to density ratios, excellent thermal and electrical insulation properties, and good resistance to acids, alkalies, and solvents characterize plastics. But the major problem caused by plastics is their inability to degrade. Some types of plastic materials, once produced, will not start degrading for about 10,000 years.

    The above fact has led to the question addressed in this project. Is there any substance which has similar properties to plastics but can degrade easily in short period of times?

     

    Background:

    Biomass is a substance obtained from a living organism. Since biomasses are easily biodegradable, scientists are looking for biomasses, which can compete with plastics. Some possibilities are Kenny, Sisal, Henequen, Agave, Bagasse, Jute, Swiss Grass and Sanseviera. But the most promising one is Hemp due to its higher efficiency in converting the sun's energy to biomass than any other plant. It has a very high yield at the rate of ten tons per acre in approximately four months.

    Hemp is the common name for an Asian annual herb that is often called True Hemp or Indian Hemp. Hemp stems are hollow and have a fibrous inner bark. Strong course fibers are obtained from mature plants while soft fibers are obtained from Hemp harvested at the time of pollination. A study of the chemical composition of hemp reveals two parts called Bast and Core. The bast contains higher percent of cellulose whereas the core contains higher percent of hemicellulose, both having some lignin content. Hemp fibers

    (yarn and tow) are obtained from hemp bast and hemp hurd is obtained from hemp core.

     

    Activity 1: Literature search on the background of Hemp

    Answer the following questions with detailed information in one or two paragraphs for each question.

     

    Biology

    1. What is Hemp?
    2. Give its scientific classification of Class, Phylum, and Family.
    3. What are the differences between Hemp and Marijuana?
    4. What climate conditions are needed to grow Hemp?
    5. Why is Hemp preferable than other fibrous plants such as Kenaf, Jute, and Sisal? Give a detailed explanation.
    6. Environmentally, what are the advantages of growing Hemp as compared to Cottonand other biomasses?

     

    History

    1. Where is Hemp grown at present?
    2. What is the cost per acre for growing Hemp? How do you compare this with the cost of raw materials used for the production of plastics?
    3. Find the cost of Hemp fibers, Hurds, and Tow per pound.
    4. Name some things that are made of Hemp and are available in the market.
    5. Where is Hemp grown on the American Continent?
    6. When was the growing of Hemp started in U.S.A. and where?
    7. Is it legal to grow Hemp in the U.S.A.? Give a detailed explanation for your answer.
    8. Do you think Hemp will be grown in the future in U.S.A.? Support your answer with proper reasons.

     

    Activity 2: Tensile Strength

    Question:

    Are the fibers of Hemp plant as strong as the fibers of plastics?

     

    Hypothesis:

    Hemp fibers have strength comparable to polypropylene fibers if not exactly equal.

     

    Materials:

    Polypropylene yarn
    G clamp (or Wooden clamp with support)

    Hemp yarn
    Hemp single fibers
    Beam balance
    Graduated cylinder
    Ruler
    Forty gallon bucket
    One or two-liter mug Electronic Balance (optional)

     

    Procedure:

    First we have to determine the radius and area of cross section of the fibers. This has to be done in an indirect method because we cannot measure the radius accurately by using a ruler. If you have an electronic balance use fibers of about sixty to seventy centimeter long. If you use a normal beam balance use about 10 pieces of hemp fibers, hemp yarn and about five to six meters long polypropylene yarn.

    Measure the length of hemp fibers in centimeters. Measure the mass in grams of each hemp fiber separately up to four significant figures using the electronic balance. Using the density of hemp, calculate the volume and then find the area of the cross section of each fiber. If you do not have an electronic balance you have to use very long fibers and yarns to give considerable mass to measure. Repeat the same for three pieces of hemp yarn.

    Unwind the polypropylene yarn to make it into thinner strings. Get two or three single fibers, measure the length and mass of each fiber accurately. Using the density of polypropylene determine the volume and the area of cross section of each single fiber of polypropylene.

    Take two or three pieces of polypropylene yarn of about the same thickness as hemp yarn and repeat the same steps to determine their area of cross section. Tabulate your reading

    Measure the mass of a forty-gallon bucket. Fix the G-clamp at the end of a table of about 1.5 meters height. Take one single fiber of Hemp; tie one end of this fiber to the clamp screw using a suicide knot. If you are using a board with support, tie one end of the fiber to the screw attached to the board. At the bottom end of the fiber tie the 40-gallon bucket using the same kind of knot. A double knot will give a firm grip. Make sure the bottom of the bucket is 6 to 7 inches above the floor.

    Take a one-liter container and fill it with water. (You can use a bottle, a beaker, or a can). Measure the volume of water that filled the mug. Since the density of water is close to 1.0 kg / L we can convert the volume to mass.

    Add water slowly and in small amounts into the forty-gallon bucket. Keep track of the number of containers of water being added. When you feel that you are close to the breaking point, add smaller amounts of water. Keep adding water till the fiber breaks and the bucket drops to the floor.

    Measure the volume of the left over water in the container at the time of breaking. Repeat the above steps for each fiber of hemp and each fiber of polypropylene separately.

    Do the same for hemp and polypropylene yarn also. Tabulate the readings. Measure the tensile strength in N/sq. and in lb./sq.in . Compare the results with the tensile strength of Tuffal as measured by Instron 1125 tensile tester at Rohm and Haas.

     

    Conclusion:

    ________________________________________
    ________________________________________
    ________________________________________
    ________________________________________
    ________________________________________
    ________________________________________

    Activity 3: Biodegradability of Hemp

    Question:

    Can Hemp be easily decomposed to simpler and safer substances as compared to plastics?

     

    Hypothesis:

    Since Hemp is a biomass it decomposes easily to simple sugars.

     

    Materials:

    Hemp Yarns
    Polypropylene yarns
    Balance
    12 beakers
    Cardboard box with lid
    Oven
    Distilled water
    Paper towels

    Salt water
    Aluminum trays

    UV lamp

     

    Procedure:

    Make a one- percent salt solution by adding ten grams of NaCl to one liter of water.

    Measure the mass of each yarn separately. If you do not have an accurate balance you might have to use four or five yarns together instead of one to place in a beaker.

    Label six beakers 1 through 6. Add 100 ml of distilled water to each beaker. In beakers 1, 3, and 5 put Hemp yarn of known mass. In the other three beakers labeled 2, 4, and 6 put polypropylene yarns of known mass.

    One beaker of polypropylene and one beaker of Hemp yarn (beakers labeled 1 and 2) should be placed in normal light (fluorescent light). Make sure the light is kept on day and night, throughout your experiment.

    Take the cardboard box and fix the UV lamp on its lid using duct tape, so that when the lid is closed only UV light will fall inside the box. Take the second polypropylene beaker and the second Hemp beaker (beakers labeled 3 and 4) and put them inside the cardboard box with the UV light on. The UV light should be kept on, day and night, throughout your experiment.

    The third polypropylene beaker and the third Hemp yarn beaker (beakers labeled 5 and 6) should be placed in a dark corner with no light.

    Label the other six beakers 7 through 12. Add 100 ml of 1% salt solution to each beaker. In three beakers labeled 7, 9, and 11 put Hemp fibers of known mass. In the other three beakers labeled 8, 10, and 12 put polypropylene yarn of known mass.

    One beaker of polypropylene and one beaker of Hemp yarn with salt water (beakers 7 and 8) should be placed in normal light.

    The second beaker of polypropylene and the second beaker of Hemp (beakers 9 and 10) should be placed in the card board box with UV light on.

    The third beaker of polypropylene and the third beaker of hemp yarn (beakers 11, and 12) should be placed in the dark corner of the room with no light.

    Once or twice a week depending on the rate of evaporation of water take the Hemp yarn out of the beaker and dry it on a paper towel separately. When you take the yarn out of salt water it is better to rinse it in fresh water before drying, just to remove any salt sticking to the fiber which could cause an error in the mass. After all the water is absorbed by the paper towel put the hemp yarn in a tray and place it in the oven for 10 minutes at 120 degrees Celsius to drive off any left over moisture. Take it out and let it cool for about 10 minutes. Measure the mass of the yarn after cooling. Add some water to the beaker to bring the level back to 100 ml. Make sure not to add salt water into the distilled water beaker or vice versa. Put the hemp yarn back into the beaker and place it back in its appropriate position.

    Repeat this process for all Hemp yarns (all odd numbered beakers) one at a time. Make sure to put the yarn back into the same beaker from which you took it; and to put the beakers in the same place where they belong.

    Take polypropylene yarn from its beaker and follow the same steps as above to find it's mass. Add enough water to bring the level back to 100 ml and place the yarn back into the beaker. Put back the beaker in its position. Repeat for all even numbered beakers.

    Record the date and the time on the clock while measuring the mass of each yarn.

    Repeat the whole process for about 10-15 weeks or longer, until considerable changes in the masses are noticed. Tabulate the results.

    Graph the results with mass versus time and find the equation of the best-fit curve. (Try exponential, quadratic, logarithmic and linear functions.) If this is a linear regression find the slope and explain the significance of slope for this experiment.

    Calculate the total time needed to completely decompose the hemp yarns by extrapolating the graph and also by using the equation. (TI-83 graphing calculator will be helpful in processing this data.)

     

    Conclusions:

    In your conclusions address the following questions:

    1. Among the 12 beakers of your experiment, which conditions showed the greatest change in the mass of the yarn?
    2. Did you notice considerable difference in the change of the mass for those placed in UV light versus those placed in the normal light?
    3. Do you think salt water acted different than the distilled water? Support your answer with a proper explanation.
    4. What is the cause for the change in the mass of the yarns? Give a proper scientific reason.
    5. Does the change in mass violate the law of conservation of mass? Explain.

     

    Activity 4: Preparation of Nitrocellulose

    Question:

    Can we prepare nitrocellulose using Hemp?

     

    Hypothesis:

    (Formulate your own.)

     

    Materials:

    Concentrated Sulfuric Acid
    Nitric Acid (fuming or > 50 % concentration)
    Distilled water
    Hemp Tow
    Dessicator
    3 Beakers of 50 ml
    3 Beakers of 25 ml
    Beam balance

    Gloves
    Goggles
    Apron

    Oven
    3 eye droppers

    Procedure:

    Dry the Hemp tow at 100�C till all the moisture evaporates. Allow it to cool in the dessicator. Weight three samples of about 0.25g of Hemp. Take one beaker, add 15g of water to the beaker and place one sample of 0.25g of hemp into the water. Mix well; label the beaker A.

    Take the second beaker and label it B. Add 10g of water. Then put the beaker under a ventilated hood and slowly add 5g of sulfuric acid. (Remember always that the acid should be added to the water and not the water to the acid.) Mix it. Place the second sample of 0.25g of Hemp tow in beaker B. Mix it well and put it aside.

    Take the third beaker and label it C. Add 1.5g of water. Place the beaker under a hood and then add 3g of nitric acid slowly (Remember always that the acid should be added to the water and not the water to the acid.) Then add 9g of concentrated sulfuric acid to beaker C. This is called the nitrating mixture. Now add the third sample of 0.25g of Hemp Tow to this nitrating mixture. Mix it well and put it aside.

    Leave the beakers in a very safe place under a ventilated hood for 24 hrs. The next day take the Hemp tow from beaker A and squeeze the water out. Place it in a dessicator for drying.

    Take the Hemp tow from beaker B containing sulfuric acid, wash it well in cold water and then in hot water several times until all the acid is removed. Then wipe any left over water by squeezing in paper towels. Place this Hemp tow in another dessicator.

    Take the Hemp tow from beaker C and wash it in cold water well and then in hot water several times until all the acid leaves the tow. Free it from all water and put it in a third dessicator. After several hours when the hemp tow is perfectly dry, measure the masses of each sample separately and very accurately. Observe any changes in the color, and texture. Record your observations in a table.

     

    Conclusion:

    ________________________________________
    ________________________________________
    ________________________________________
    ________________________________________
    ________________________________________
    ________________________________________

    Activity 5: Preparation of Paper

    Question:

    Which is the best technique to prepare paper using hemp hurds?

     

    Hypothesis:

    To be formulated by students with the help from teacher.

     

    Materials:

    Hemp Hurds
    Water
    Corn starch
    All-purpose flour
    Fenugrick seeds (Indian Spice called Methi)
    Blender
    Pressure cooker (or Pot with lid)
    Bunsen Burner
    Stand
    Sponge (8" by 11")
    Felt cloth
    Cheesecloth (12" by 15")
    Rolling pin

     

    Procedure:

    A. Take one cup of hemp hurds and soak them in three cups of water for several hours. (Test what time will give the best results) Soak one tablespoon of Fenugrick seeds in a cup of water for several hours.

    Place the hurds and water in a pressure cooker and cook them for 30 minutes. Shut off the pressure cooker and wait till it cools. If you do not have pressure cooker use a pot with a lid. Add more water and cook for a longer time.

    Remove the hemp hurds from the cooker and put them in a blender with just enough water (1 cup). You can use the water that is left in the pressure cooker. Blend the hurds for five minutes.

    Then add the soaked Fenugrick seeds and continue blending until you see a fine paste. This is called pulp slurry.

    Take the cheesecloth and place it on the piece of sponge (8" by 11"). Pour the pulp slurry onto the cheesecloth and press lightly to remove excess water. Squeeze the sponge A couple of times to keep it dry and to be able to absorb water from the pulp slurry.

    Now place the cheesecloth containing the pulp between two pieces of felt. Gently roll out pulp to a thickness of 2 millimeters. Wring out excess liquid from felt.

    Remove the cheesecloth containing the paper from the felt cloth. Set the cheesecloth with the paper out to dry overnight. Stacking layers together will help to keep paper flat. Gently remove the paper from cheesecloth the next day while it is damp to prevent it from sticking to the cheesecloth.

    B. Repeat the process using cornstarch instead of Fenugrick seeds.

    C. Take one tablespoon of all-purpose flour and add it to one cup of water. Add this solution to the hemp hurds while cooking them in water. Then blend them in the blender without adding Fenugrick seeds and follow the same steps given in procedure (A) after preparing the pulp slurry.

    D. Repeat the same process in C and use Fenugrick seeds while blending the mixture in the blender. Follow the rest of the procedure as in (A).

    E. Repeat the same process as in (A), but add 3% sodium hydroxide solution to the pulp slurry.

     

    Conclusions:

    Your conclusions should address the following:

    1. Test your hemp papers made through processes A to E to decide their quality. What tests do you plan to perform ?
    2. Which one do you feel is the best process? Give all possible reasons to support your answer.
    3. Compare the hemp paper you made with that made by paper wasps. Give the similarities and differences.
    4. Try to recycle the Hemp paper you made. Write your observations while recycling your paper.
    5. Give a brief procedure you followed to recycle your Hemp paper.
    6. 6. What are the ecological implications of using Hemp instead of wood for making paper?
    7. 7. What are the economical implications using Hemp instead of wood for making paper?
    8. (Questions 6 and 7 need some research on how normal paper is made and the effects of the process.)
    9. In what way can you link this activity of making Hemp paper, to the main goal of finding an alternative to plastics?
    This experiment is courtesy of 



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