Biodegradation in Landfilled of Biodegradable Micro-braided Yarn Academic research paper on "Materials engineering"

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Energy Procedia 89 (2016) 282 - 290

CoE on Sustainable Energy System (Thai-Japan), Faculty of Engineering, Rajamangala University

of Technology Thanyaburi (RMUTT), Thailand

Biodegradation in Landfilled of Biodegradable Micro-braided Yarn

Sommai Pivsa-Art1*, Jutamas Kord-Sa-Ard1, Wanida Sijong1, Weraporn Pivsa-Art1,

Hitomi Ohara2, and Hideki Yamane2

department of Chemical and Materials Engineering, Faculty of Engineering, Rajamangala University of Technology Thanyaburi,

Pathumthani 12110, Thailand 2Department of BiobasedMaterials Science, Kyoto Institute of Technology, Matsugasaki, Kyoto, 606-8585, Japan

Abstract

Biodegradable polymer yarns of polymer blends of poly(lactic acid) (PLA) and poly(butylene succinate-co-adipate) (PBSA) reinforced with natural fiber were prepared by a micro braiding technique. The biodegradation of the micro-braid yarn was studied by field tests. The yarn are prepared from polymer blends of PLA:PBSA with ratios of 100:0, 90:10, and 85:15 (wt%) by a single screw extruder. Braided samples were prepared using jute as a braided core fiber. The mechanical property analysis showed tensile strength of polymer yarn with jute fiber higher than polymer yarn without jute. Biodegradation of micro-braiding yarn with and without jute fiber was studied by buried under controlled conditions compared with cellulose. The field biodegradation test was carried out for 28 days with period of 7 days sampling. It was found that humidity and soil temperature affected the biodegradability of polymers. Analysis of samples confirmed that buried at low temperature position showed higher degradation than at high temperature. High humidity enhanced the degradability due to hydrolysis reaction. Micro-braided polymer yarns of PLA:PBSA (85:15) and PLA:PBSA (85:15)/jute showed similar biodegradability confirmed that the mechanism of biodegradation from surface of the yarn was priority.

© 2016 The Authors.Publishedby Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee of the 12th EMSES 2015 Keywords: biodegradable polymer; poly(lactic acid); poly(butylene succinate-co-adipate); jute fiber

* Corresponding author. Tel.: +66-2549-3005; fax: +66-2549-4045. E-mail address: sommai.p@en.rmutt.ac.th

1876-6102 © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee of the 12th EMSES 2015 doi:10.1016/j.egypro.2016.05.036

1. Introduction

Composite materials produced from bio-based and biodegradable polymers are important due to they are friendly to environment from their origin of starting materials and the post-consumer products. Poly(lactic acid) (PLA) is one of the well-known bio-based materials. Lactic acid is first produced from various starches, sugars, and other biomass materials through biological fermentation, and then is chemically converted to poly(lactic acid) [1,2]. PLA has high transparency and elastic modulus, can be thermoplastically processed like conventional plastics, and has been widely used in the development of disposable products, such as disposable cutlery, cups, and films [3-5].

However, since PLA is quite brittle (low strain at break and high modulus) at room temperature and easily hydrolyzable, its applicability has been somewhat limited [6]. Thus, blending of PLA with various soft and tough polymers can enhance mechanical properties and biodegradability [7,8].

On the other hand, poly(butylene succinate -co -adipate) (PBS A) is commercially available aliphatic polyester synthesized from diacids and diols with high flexibility, excellent impact strength, melt processability, thermal, chemical resistance and low melting point of 90°C, which is more readily biodegraded than PLA [9]. They have excellent processability and can be moulded into a variety of products using conventional equipment applicable to polyolefins [10]. Weraporn Pivsa-Art, et al. reported the preparation of polymer blends of PLA and PBSA using a twin screw extruder. The blends were fabricated into compression molded parts and melt-spunfiber. The impact strength of the compression molded parts was improved by the addition of soft PBSA. Crystallinity of the blend fibers was affected by the post drawing condition as well as the PBSA content [11]. Yun-Xuan Weng, et al. reported a biodegradation behavior of P(3HB,4HB)/PLA blends in real soil environments. Their blends have different degradation rates in different depths of soil [12]. Yun-Xuan Weng, et al. studied a biodegradation behavior of poly(butylene adipate-co-terephthalate)(PBAT), poly(lactic acid) (PLA), and their blends under soil conditions. The carbon atom content in the molecular structure of the PBAT, PLA, and PBAT/PLA samples decreased, while the oxygen atom content increased, indicating that the samples indeed degraded [13]. Sommai Pivsa-Art, et al. reported the effect of additive on crystallization and mechanical properties of poly(lactic acid) (PLA) and poly(butylene succinate-co-adipate) (PBSA) blends. PLA and PBSA were blended in a twin screw extruder, which incorporated poly(butylene adipate-co-terephthalate) (PBAT) as an additive in PLA/PBSA blend. The ratio of PLA/PBSA was 80/20. The contents of PBAT were varied from 0 to 50 wt%. The addition of 20 wt% PBAT showed the maximum impact performance of the PLA/PBSA blends [14].

It is known that PLA degradation in compost takes place in two main and consecutive stages, i.e. the hydrolytic and enzymatic degradation [15]. PLA disintegration starts by surface hydrolysis [16] leading to polymer random decomposition [17]. The degradation process is related to the molecular weight, degree of crystallinity, purity, stabilizers, whether there is blocking or not, and so on [18]. The biodegradation of PLA under soil conditions is a complex process, and the degradation rate is relatively slow [19-21]. However, under composting conditions, PLA undergoes biological decomposition into carbon dioxide and water [22-24]. Toshinori et al. studied the biodegradation behavior of PLA under composting conditions. The results demonstrated that the PLA film samples degraded in three weeks, while PLA rope samples degraded in six weeks [25].

PLA and PBSA are both biodegradable polymers, and jute is the natural product. The composite yarn of biodegradable polymer reinforced with natural fiber is expected to show excellent biodegradability. This research reports the study of biodegradation of micro-braiding yarn prepared from polymer blend of PLA/PBSA fiber reinforced with jute fiber under soil landfilled conditions.

2. Experimental

2.1 Materials

Poly(lactic acid), PLA (2002D, Natureworks LLC, USA) was used in this study. Poly(butylene succinate-co-adipate), PBSA (Bionelle®) was supplied by Showa High Polymer Co., Ltd., Japan.). Jute was supplied by Kyoto Institute of Technology which was purchased from Bangladesh.

2.2 Fiber preparation process

The pellets were first dried in an oven at 80°C for 8 hour prior to processing. The blending weight ratios of each pellets (PLA/PBSA) were 100/0, 85/15 and 0/100. The polymer pellets were then mixed together with dry blend. After that the blends were melt spun through 5 hole which diameter has 0.32 mm per hole, using single screw extruder (ThermoHaak Polydrive) equipped. Spinning conditions: temperature at barrel were adjust 160, 170, 180 (Zone Extruder) 180 (Connecter) and 190 °C (Die), screw speed 8 rpm and the final multifilament were collected (Fig. 2.1).

Fig. 2.1 Fiber preparation process.

2.2 Micro-Braiding Yarn process

Fiber was spun into the bobbins to put on the stand of micro-braining machine. The number of bobbin is 16 bobbins. The fibers were jointed by binding together for braiding. In the jute fiber reinforced polymer yarn the binding was carried out by binding the central jute together. When braiding starts the jute fiber will move to the centre as shown in Fig. 2.2.

Fig. 2.2 Micro-braiding yarn process.

2.3 Biodegradation under soil test

Biodegradation under real soil conditions was carried out at the experimental soil pond located in RMUTT, Thailand; Fig. 2.3 shows a schematic diagram and digital photos. The actual size of the soil pond is 3 m x 2.5 m x 1.2 m (length x width x height). The pond wall not coat the cement due to excess water can ooze out, and air can get in and out. Field soil was put into the pond until the surface was 20 cm lower than the top of the pond wall. Ten specimens were tested for each blend. The soil temperature and humidity at 20 cm depth was recorded every day. The soil pH at 20 cm depth was recorded every three day. The specimen of each sample was taken out every week for testing.

Fig. 2.3 Soil pond at RMUTT, Thailand.

2.4 FTIR

Before and after degradation, the string samples underwent an infrared test using the attenuated total reflection (ATR) method in order to obtain the changes of the IR spectra of the samples before and after degradation.

3. Results and Discussion

3.1 Micro-braided yarn fiber

Yarn was prepared from micro-braiding of polymer blend fibers and the braided yarn having jute reinforced or combined rope.

(c) PLA:PBSA (85:15) (d) PL A: PBS A (85:15)/Jute

Fig. 3.1 Micro-braided yarn of (a) PLA, (b) PBSA, (c) PLA:PBSA (85:15) and (d) PLA:PBSA (85:15)/Jute.

3.2 Humidity of soil

IOO »

■»J

M J» ID 0

i ; i * 5 s t g 9 io u i: u h u le r a w » ;; s h is » r a Tlmr

Fig. 3.2 Humidity of soil in compost pond.

The humidity of soil was calculated from percentage of water in soil compared with weight of soil after drying in an oven at 105 oC for 4 h. The sampling for humidity measurement was carried out with soil at 10 cm under the surface for 10 points. The humidity measurement was done every day. The results are shown in Fig. 3.2. It was found that the humidity of soil was almost same content of averagely 23%.

3.3 Temperature oof soil

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Time (days)

Fig. 3.3 Temperature of soil in compost pond

Temperature of soil was measure for 28 days at 10 cm under sol surface. The average of 10 points measurement was calculated. The results are shown in Fig. 3.3. It was found that temperature of soil in the test varied from 1-3 degree Celsius. The average temperature is 27 oC.

3.4 pH oof soil

The pH of soil was measured every 3 days from soil sample 10 cm depth from the surface. The soil sample was dissolved in distilled water and measured the pH. The results are shown in Fig. 3.4. It was found that the average pH of soil is 6.65.

l J 7 10 IJ li 19 12 25 28

Tlmr (day«)

Fig. 3.4 Humidity of soil in compost pond. 3.5 Biodegradability of polymer, polymer blends and composite yarn

Ill 1 fl ! 1 III (llllll

111 i ll-llllli 1 1 1 ■ 1 \\ iilb-iy P 1 i iji, 1;

(a) 0 week (b) 1 week (c) 2 weeks (d) 3 weeks (e) 4 weeks Fig. 3.5 Photographs of neat PLA string before and after buried under soil.

From Fig. 3.5 the neat PLA string before biodegradation test showed brittle and low flexibility property. After 1, 2 and 3 weeks the string was clearly broken because of brittleness property of PLA. However, the samples of 4 weeks showed little degradation due to the buried position has low humidity.

(a) 0 week (b) i week (c) 2 weeks (d) 3 weeks (e) 4 weeks

Fig. 3.6 Photographs of neat PBSA string before and after buried under soil.

Biodegradation test under soil of neat PBSA is shown in Fig. 3.6. PBSA is a soft and flexible polymer. After 3 and 4 weeks landfilled test PBSA string shows clearly broken but likely less than PLA degradation. From Fig. 3.7 it was found that the PLA:PBSA (85:15) string did not show degradation after 4 weeks. Fig. 3.8 shows biodegradation test of PLA:PB SA (85:15)/jute yarn. The yarn and jute did not show degradation after 4 weeks.

Fig. 3.8 Photographs of PLA:PBSA (85:15)/Jute string before and after buried under soil.

(a) 0 week (b) I week (c) 2 weeks (d) 3 weeks (e) 4 weeks

Fig. 3.9 Photographs of jute string before and after exposed under soil.

Fig. 3.9 shows biodegradation test of jute string to compare with polymers and composite. Jute string showed increasing of degradation after 2 and 3 weeks. At 4 weeks jute was degraded to small pieces and no samples could be collected.

(a) 0 week (b) 1 week (c) 2 weeks (d) 3 weeks (e) 4 weeks

Fig. 3.10 Photographs of cellulose samples before and after buried under soil.

From Fig. 3.10 after the first week swelling and wrinkled of cellulose sample was detected. The broken parts of samples could be seen after 2 weeks buried. The degradation of cellulose is similar to the case of jute string due to same chemical structures.

3.6 Chemical structure measurement using FT-IR method

The string samples before and after biodégradation test were subjected to Chemical structure measurement using FT-IR technique. The results are shown in Fig. 3.11 (a-f).

Fig. 3.11 FT-IR spectra of (a) neat PLA string (b) neat PBSA string (c) jute string (d) PLA/PBSA (85/15) string (e) PLA/PBSA (85/15) /Jute string (f) cellulose paper

From Fig. 3.11 (a-d) and Fig. 3.11 (f) the FT-IR analysis of PLA, PBS, Jute, polymer blend of PLA/PBSA and cellulose before and after biodegradation test show same spectrum. The results confirm that after degradation smaller polymer molecules are obtained. However, the degradation of PLA/PBSA/Jute string (Fig. 3.11 (e)) shows disappearance of hydroxyl peak at 3,400 cm-1 indicated degradation of jute parts. Higher concentration of carbonyl

group at 1,750 cm-1 could be observed. 4. Conclusion

Micro-braided yarn of polymer blend of poly(lactic acid) and poly(butylene succinate-co-adipate) ratio 85:15 reinforced with jute fiber was prepared. Biodegradability of micro-braided yarn was studied compare with cellulose by buried in soil for 28 days. The samples were taken every week for weight loss measurement and structure analysis. Humidity and soil temperature are important factors of biodegradation. It was found that polymer blend of PLA:PBSA and PLA:PBSA/Jute showed similar biodegradation behavior.

Acknowledgements

The authors would like to acknowledge the National Research Council of Thailand for research financial support. References

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