Common Milkweed as an Alternative Cellulose Fiber Source for Making Paper with Strength and Moisture Resistance
Hans Kellogg, Heather Hendrixson,and Renmei Xu, Ball State University;
Maruthi Srivatsan Mogundan and Paul D. Fleming, III, Western Michigan University
With increased interest in sustainability, researchers look to alternative fiber sources such as the common milkweed as an alternative material for making paper1, 2. Extremely prolific, milkweed grows in varied climates from far south to the northern plains, flourishing in both wet and dry climates3. Currently the plant is considered a noxious weed, and farmers work to eliminate it from their fields as it competes with plants grown for commercial value. However, there is interest to the use of the common milkweed because of the concern for the dwindling population of Monarch butterflies. The Monarch larva use only milkweed as their source of sustenance4. While this study did not deal directly with the declining Monarch populations, interest in planting milkweed would increase the viability of using this plant for making paper. Research has shown that milkweed is easily cultivated and can be commercially grown with the intent to maximize the output of cellulose fiber2.
This study explores two specific portions of the plant containing cellulose. One is the plant’s stem5, with its long fibers lend itself to an increase strength. The other is the floss6, where buoyant white fibers are attached to the seeds and utilize their light weight and hollow structure to catch the wind, transporting the seeds away from the plant to begin germination. During WWII, the floss was used for life preservers as the Japanese cut off shipping of traditional materials used for life vests. Naturally resistance to moisture, the paper produced with these fibers would be proven beneficial to specific areas of packaging, where moisture protection is crucial. When combined together, fibers from the floss and stems could produce a paper that is both strong and moisture resistant, lending itself for use in packaging where these attributes are advantageous.
Waiting until the plants had died back, common milkweed was collected for processing. Separating the two portions of the plants, the material was then broken into manageable sized portions and bagged, ready to process. Using traditional papermaking techniques, the fibrous plant material was processed through a Holland Beater with water added to produce a slurry of approximately 97% water and 3% consistency cellulose plant fiber. At that point, numerous hand sheets were produced to create a suitable number of samples for testing. During the creation of hand sheets, sizing was added to produce paper that would be defined as slack-sized, and hard-sized. Once dried, each of the hand sheets was tested for moisture resistance using the contact angle method. Surface energy of the paper was determined from the contact angle measurements. For evaluation of the strength of the hand sheets, the samples were tested for wet tensile breaking strength and tensile energy absorption (TEA).
Cobb, Emco DPM and and MVTR (Moisture Vapor Transmission Rate) tests were also performed. The Kappa number was determined to measure lignin content. Fibers were also analyzed with a Fiber Quality Analyzer and Microscopy.
While further testing is necessary, test results indicated an increase in moisture resistance and strength (both wet and dry) resulted in a paper material that would be suitable for use in packaging where both strength and moisture resistance are critical.
Printability tests were performed with various processes used for packaging.
- Michael Alan Hermans, Robert Dale Sauer, Shafi Ul Hossain and John Dennis Litvay, “Tissue products made from low-coarseness fibers” US004001672B2
- Narendra Reddy and Yiqi Yang, “Extraction and characterization of natural cellulose fibers from common milkweed stems”, Polymer Engineering and Science, 49:11 (2009), pp. 2212–2217.
- David Taylor “Common Milkweed (Asclepias syriaca L.)”, downloaded Oct. 5, 2018 from https://www.fs.fed.us/wildflowers/plant-of-the-week/asclepias_syriaca.shtml.
- Marjie Ducey, “Monarch food shortage has butterfly advocates planting milkweed ‘from Nebraska to Pennsylvania’”, downloaded Oct. 5, 2018 from https://www.omaha.com/living/monarch-food-shortage-has-butterfly-advocates-planting-milkweed-from-nebraska/article_e74bafe3-0ef9-56eb-9d60-dbc4b86695de.html
- Michelle Stevens, “COMMON MILKWEED”, downloaded Oct. 5, 2018 from https://plants.usda.gov/plantguide/pdf/cs_assy.pdf.
- Patricia Cox Crews, Shiela A. Sievert, and Lisa T. Woeppel, Elizabeth A. McCullough “Evaluation of Milkweed Flossasan Insulative Fill Material”, Textile Research Journal 61, no.4 (April 1991), pp. 203–210.
Water Based Soy Inks for Packaging
Rahul Pingale, Alexandra Pekarovicova, and Paul D. Fleming, III, Western Michigan University
Many printing inks use volatile solvents in the formulation, which are hazardous to the environment from emission of VOC’s and at the same time, synthetic resins in these inks are not biodegradable. These problems and particularly the fluctuating and rising price of petroleum are main reasons to look for new resources for making more environmentally friendly printing inks. The majority of the commercially available water based inks are formulated based on using acrylic resins, synthetic colorants, solvents/water and additives, which are the common main components for formulating printing inks. Soybean protein is a potential renewable raw material for replacement of acrylic resins. Soy oil is already successfully implemented in lithographic printing processes, including litho inks for printing newspapers, books, magazines and newborn baby footprints (Swiatek,1992; Browner,1992; Erhan, 1995). Newsprint soy inks can be successfully deinked and newsprint can be recycled and reused. Soy protein is known to be employed in paper coating formulations.
Soybeans include about 40% protein and 20% oil. They contain three natural surfactants: soy protein, soy lecithin, and soy saponin. Soy proteins are obtained through the extraction of soybean oil. They form the byproduct that remains after the removal of the hulls and oil from the flake (Xu,2011; Kinsella,1972). Soy protein concentrate is made by removing the aqueous liquid part of the soybeans and it contains approximately 65-72% protein. Soy protein isolate is made from defatted soy flour by removing the carbohydrates of the bean. It is the most refined form of soy proteins and it contains 90% protein (Xu,2011; Kinsella,1972). Soy protein is used in a variety of foods, such as salad dressings, frozen desserts, breads, and breakfast cereals; also, it can be used as a natural polymeric emulsifier, foaming agent, and texture-enhancer. The other industrial products that use soy protein include adhesives, asphalt additives, resins, cleaning materials, cosmetics, inks, paints, plastics, polyesters and textile fibers (Smith,1996).The basic application of industrial-grade protein is as a binder in paper coatings. Proteins are built by condensation reaction of amino acid monomers, which create peptide bonds. Water molecules are released as a result of condensation reaction between amino acids (Graham,1983).Soy protein has a complex 3-D shape and contains 19 different amino acids, which are held together in a coiled structure by peptide bonds. Proteins contain positive and negative functional groups. The functional groups found in soy protein consist of: amino, carboxyl, hydroxyl, phenyl and sulfhydryl (Graham,1983).
In this research, soy proteins were tested for their suitability to partially or fully replace acrylic emulsion resins in water based packaging inks. The focus was on formulating inks for linerboards, because linerboard is a substrate printed with 100% water based ink formulations, and the linerboard packaging sector is exponentially growing. The first step was formulating water based ink based on fully acrylic solution and emulsion polymers as resins. Next, the letdown portion of the ink was formulated with soy polymers, adding them in increments 10-20-30 up to 100% replacement of acrylic emulsion portion of fluid packaging ink. A cyan process color ink was formulated, and its printability, rheology, and end use properties such as rub resistance, gloss, and adhesion were tested and compared to fully acrylic formulations. It was found that the soy polymer did not affect the final color of packaging ink, measured as delta E. Delta E for all soy formulations was less than 1.5, when fully acrylic formulation was used as a standard. Rub resistance of soy inks was similar to fully acrylic formulations. This research will help to achieve the formulation of a truly environmentally friendly water based ink, while eliminating emission of VOCs.
- Browner Sharen, “Soy ink based art media”, US Patent US 5167704A, December 1992.
- Erhan Sevim, Marvin Bagby, “Vegetable-oil-based printing ink formulation and degradation”, Industrial Crops and Products 3, no. 4 (1995): 237-246.
- Graham, Paul M. Thomas L. Krinski, “Heat coagulable paper coating composition with a soy protein adhesive binder”, US patent US 4421564 A, December 1983.
- Kinsella, John E.” Functional properties of soy proteins.” Journal of the American Oil Chemists’ Society 56, no. 3 (1979): 242-258.
- Smith, Keith “Industrial uses of soy protein: New idea”, 87th AOCS Annual meeting & Expo,1996; 7(11):1212-1223.
- Swiatek Jeff, “Farmers Help Soy Ink makes its Mark,” Indianapolis Star, January 26, 1992.
- Xu, Qingyi, Mitsutoshi Nakajima, Zengshe Liu, and Takeo Shiina, “Soybean-based surfactants and their applications”, Soybean-Applications and Technology, Prof. Tzi Bun Ng (Ed.), ISBN: 978-953-307-207-4, Book Chapter (2011) Chapter 20:341-364, Available from: http://www.intechopen.com/books/soybean-applicationsand-technology/soybean-based-surfactants-and-their-applications.