| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系 === 102 === Study of Bamboo Fiber Reinforced Polylactic Acid Composite
Yu-Chi Tsao
Wen-Bin Young
Department of Aeronautics and Astronautics, NCKU
SUMMARY
Bamboo fiber (BF) is a good candidate as the reinforcement for green composites. The applications of bamboo fibers as fabric or structural reinforcements are being widely investigated. This study went through the process from the bamboo strips to the fibers and compounded with the PLA to form the composite pallets for the following injection molding process. The alkali-treated BF at 100 °C for 12 h could properly delignified the bamboo fiber strips, resulting in the required bamboo fiber bundles. After compounding with PLA using a banbury mixer with different temperature , the resulting composite after injection molded composites can improve the mechanical properties the tensile strength, tensile modulus with compounding temperature 180℃. Another mechanical properties ,flexural strength, flexural modulus impact strength are also improved, adding 36% fire retardant in the composite can pass the fire preventing test . The reinforced effect of the BF on PLA was quite apparent in our experiments. A simple rule of mixture was used to approximate the tensile modulus and strength of the PLA/BF composite.
Key word：Polylactic, Bamboo fiber, compounding temperature, Biocomposite, injection molding
INTRODUCTION
In recently years, eco-friendly materials that can be efficiently recycled are getting more attention and have been extensively discussed. Poly lactic acid (PLA) is a commercially available biodegradable material derived from corn fibers. The glass transition temperature of PLA is around 55~60℃ that is higher than other biodegradable material. However, relatively high price, brittleness, and low toughness of PLA limit its application. Bamboo fiber is a good candidate as the reinforcement for green composites. The applications of bamboo fibers as fabric or structural reinforcements are being widely investigated. Bamboo fibers can be processed into different form for applications. The node and epidermis portions of the bamboo are often removed with the remaining culm used for the following extracting process. BF can be extracted from the bamboo strips by chemical or mechanical methods. Both the raw and dignified BF could be used. In this study we use bamboo fibers as reinforcement in polymeric composite to improve PLA’s properties.
MATERIAL AND METHOD
Materials
Polylactic acid, was thermoplastic aliphatic polyester made from renewable resources, such as corn starch. The injection grade PLA polymer (IngeoTm biopolymer 3001D from natural works LLC) was used in this study.
Thorny bamboo is treated by alkaline peroxide by adding sodium hydroxide at 100℃for 12hrs and then washed by water, mechanical force is applied to scrub the bamboo bundle into fibers. The BF is dried before compounding with PLA.
Method
Bamboo fibers/ Polylactice acid (PLA) biocomposite material were prepared by Banbury mixer. Compounding bamboo fibers with PLA using a banbury mixer , then using injection molded to fabricate BF-PLA biocomposite The effect of compounding temperature, on the microstructure, fiber distribution and fiber length of the composite were examined by specimen analysis. The mechanical and thermal properties of the resulting composites were investigated for different bamboo fiber contents (10wt%, 20wt%, 30wt%). The effect of adding fire retardant in the composite was tested as well of fire prevention.
RESULT AND DISCUSSION
compounding temperature
Figure 4-5 shows the tensile strength from the tensile strength test for the PLA/BF composite with different compounding temperature. With low compounding temperature 140℃＆160℃, as the fiber content 20% and 30%, the tensile strength is lower than the PLA polymer, however, with high temperature 180℃, the tensile strength is higher than PLA polymer. The specimen analysis shows that the higher compounding temperature the fiber length is longer, the distribution of bamboo fiber in the specimen is all lying along the flow path.
Another mechanical properties
After compare different compounding temperature, we found that when compounding temperature is 180℃, bamboo fiber can enhance PLA’s tensile strength. In this chapter, we want to compare other mechanical properties such as flexural strength, impact strength and dynamic mechanical properties, the result is shown as figure 4-18, 4-19, 4-20, the tensile strength, flexural strength, flexural modulus, impact strength, storage modulus and ten delta increase with the BF content increase.
Adding fire retardant
In this part, we use UL-94 standard as fire prevention standard. We added 18% and 36% fire retardant in the PLA/BF composite, the test result is shown in table 4-3,4-4,4-5, adding 36% fire retardant no matter what fiber contents is, all specimen can pass the fire prevention test, the effect of fire prevention is better than adding 18% fire retardant.
CONCULSION
Bamboo fiber reinforced PLA composite is one of the green materials that can reduce the environmental impact. This study went through the process from bamboo strips to the fibers and compounded with PLA to form the composite pallets for the following injection molding process, we found that compounding temperature influence the result of composite very much, and from the result, the compounding temperature must high enough (180) to enhance the tensile strength of BF-PLA composite, for another mechanical properties, flexural strength, flexural modulus and impact strength increased with BF fibers content increased, BF PLA composite adding 36% fire retardant has better fire prevention.
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