Flame Retardancy of Bio-base Plastics

Available online at www.sciencedirect.com

ScienceDirect Energy Procedia 89 (2016) 38 – 44

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

Flame retardancy of bio-base plastics Masayuki Okoshi*, Supaphorn Thumsorn, Hiroyuki Hamada Kyoto Institute of Technology, Kyoto, 606-8585, Japan

Abstract This paper describes the evaluation of the flame resistance on bio-based polymer (BBP) and developing inedible woody biomass plastic. Nano aluminum hydroxide nano-Al(OH)3) was used as flame retardant for polyolifin. The effect of nano-Al(OH)3) on flame retardancy of polyolefin was reported. We also developed flame test metho by informing flammability of the combustion process from multi-cone calorimeter. In this research, we studied flame retardancy of poly(lactic acid) and reported flammability of polymer materials by rating of UL-94 using the relationship of heat released rate and time of ignition in multi-cone calorimeter. © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license © 2016 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the 12th EMSES 2015. Peer-review under responsibility of the organizing committee of the 12th EMSES 2015

-Keywords: char; flame retardant; combustion; PLA; cellulose

1. Introduction Flame retardant property is important especially for polymer products, which various flame retardant materials can be applied for suitable products [1-6]. Petroleum-based plastics are linked to certain environmental problems. One such problem is the depletion of natural resources; another is global warming. Bio-based plastics (BBP) are thus in the spotlight as they are made from renewable resources. However, BBP exhibit very poor properties compared to petroleum-based plastics, thus making it difficult to apply BBP to products. We have studied new BBP using BBP, and applied it to products, but one of BBP causes a food problem, as it is made from corn. It is therefore important to develop new BBP made from inedible resources. We have studied the behavior of neat BBP and flame-resistant BBP under the combustion. We have studied flameretardancy since 2001. It is shown as follows.

-* Corresponding author. Tel.: +81 75-724-7844; fax: +81 75-724-7844. E-mail address: [email protected]

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.2016.05.006

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1.1. 1st Nano-Al(OH)3 particle in olefine polymer in 2003 Novel flame retardant mechanism was found from the results. Flame rewardable of EVA composite contained with the novel Nano-particles of the aluminum hydroxide [8]. The result is shown in Fig. 1 and Fig. 2 and summarizes in Table 1.

Fig. 1. TEM photograph of nano-Al(OH)3 particle.

Fig. 2.Heat release rate of EVA, AL-1 (EVA with nano-Al(OH)3) and AL-2 (EVA with micro-Al(OH)3). Table 1. Composition and mechanical properties of EVA with Al(OH)3 nanocomposites. Materials

Contents (phr)

Al(OH)3 particle size

Tensile strength (MPa)

EVA

EVA(100)

-

4.7

AL-1

EVA(100)+Novel Al(OH)3 (10)

10 nm

5.2

AL-2

EVA(100)+Normal Al(OH)3 (10)

1 Pm

4.8

Elongation (%) 963 1002 974

1.2. 2nd Nano-Sumectilte in olefin polymer in 2005 We found the flame retardacy and mechanical properties of the partial dispersion were better than the complete one’s in sumectite nanocomposite. Fig. 3 and Fig. 4 presents the model of nano-composite flame retardant and the test results, respectively.

Fig. 3. Modle of sumectite nanocomposites.

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Fig. 4. Heat release curves of sumectitie nanocomposites.

1.3. 3rd Development of flame test methods in 2008 We could obtain the relation between the heat release rate or the integrated heat release value and the combustion time by the multi-cone calorimeter (MCC) as shown in Fig. 5. Fig.6 depicts the behavior with V-0 (PC/ABS;Teijin MUTIRON T7300) and V-2 (ABS;UMGABS ZFJ310) materials by Heat Release Rate (HRR) and Combustion time on MCC. In this Figure the HRR of V-2 resin is higher than the V-0 resin. In addition, the HRR curve is shown the different between 1st and 2nd ignition. We are clear to conclude the data from Black box in UL-94 combustion test.

Fig. 5. A novel combustion machine, Multi-cone calorimeter.

Fig. 6. Heat release rate of V-0 and V-2 materilas under the UL-94 vertical testing.

Masayuki Okoshi et al. / Energy Procedia 89 (2016) 38 – 44

In order to increase the variety of eco-conscious bioplastic materials, KIT is researching and developing a new type of cellulose-based bioplastic in addition to polylactic acid (PLA; KIT also developed biomass plastic with the PLA content of 30 weight percent, which has been introduced in its products since 2007).Cellulose is an organic compound found in wood. Compared to other materials, which are found only in certain countries, wood materials are available worldwide and require less transport, thereby reducing CO 2 emissions. In addition, using an inedible substance like cellulose avoids the indirect use of farmland (i.e. indirect use of farmland refers to the planting of biomass materials in fields used to produce food) and consequently does not compete with food supplies. However, cellulose is generally less durable and flame resistant, and thus is more problematic to handle than PLA. 2. Experimental 2.1. Materials and sample preparation PLA resin (PLA4043D, NatureWorks LLC, USA) was carried out by an injection molding machine (J55AD, manufactured by The Japan Steel Works, LTD., Japan) under the conditions of a nozzle temperature of 200°C, and a mold temperature of 90°C. CAP (cellulose acetate propionate; Eastman CAP482, Japan) resin, ABS resin (191, manufactured by Asahi Kasei Corporation, Japan), and Resorcin bis(diphenyl phosphate;CR741, manufactured by Daihachi Chemcal Inc., Japan) were mixed. The molded element in the form of a sheet was ground using a smallsized two-axis grinding machine (CSS, manufactured by FUJITEC Co., Japan) to be shaped into pellets, which were then extruded by an extruder (TEM-SS, manufactured by TOSHIBA MACHINE CO., LTD., Japan) under the conditions of a feed temperature of 180°C, a head temperature of 220°C, and a screw rotating speed of 60 rpm, after which injection molding was carried out by an injection molding machine (J55AD, manufactured by The Japan Steel Works, LTD., Japan) under the conditions of a nozzle temperature of 220°C, and a mold temperature of 40°C. 2.2. Flammability testing (UL-94) A vertical burning test was carried out in accordance with JIS Z 2391 (Test flames -- 50 W horizontal and vertical flame test methods). The thickness of the sample was 2 mm. For the molded item samples that were favorably evaluated by the flammability test, the level providing the highest flame retarding effect was defined as V0, and subsequent levels were defined as V1, V2, and HB, respectively, in descending order of flame retarding effect. Further, any molded item which was not evaluated as at least level HB was rejected. 2.3. Mechanical strength testing An autograph (V1-C, manufactured by Toyo Seiki Seisaku-Sho, Ltd.) was used and, in conformity with JIS K 7161 (Plastics -- Determination of tensile properties Part 1: General principles), the yield stress was measured at room temperature with the rate of pulling being set at 50 mm/min. 3. Results and Discussion 3.1. Behavior of flammability BBP We observed the behavior of flammability for various BBP. Firstly, Fig. 7 shows a result of HRR curves of PLA under the UL-94 vertical testing. PLA burnt with a small flame for a long time. Fig. 8 presents the relationship between maximum heat release rate (MHRR) and total heat release rate (THRR). The combutional behavior of PLA was different from other polymer. As comparison, PLA is middle point of MHRR in various polymers combustional energy as presented in Fig. 8. From Fig. 8, the combustion energy of polyester and polyamide exhibited lower in HRR [9].

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㻝㻜 㻜 㻥 㻤

㻠㻜㻜 㻟㻜㻜

T HRR→ 㻞㻜㻜

←HRR 㻝㻜㻜 㻜 㻜

㻡㻜

㻝㻜㻜

㻙㻝㻜㻜 㻙

㻣 㻢 㻡 㻠 㻟 㻞 㻝㻡㻜㻝 㻜

⥲Ⓨ⇕㔞㻔㼗㻶㻕

Heat release (W) Ⓨ⇕㏿ᗘ㻔㼃㻕

㻡㻜㻜

Total heat release rate (kW)

42

᫬㛫㻔㼟㼑㼏㻕 Time (s)

Fig. 7.Combustion behavior of PLA.

Fig. 8. MHRR and THRR of materilas under the UL-94 vertical testing.

Fig.9 illustrates the relationship between MHRR and dripping time of polymer from UL-94 testing. We can separate two groups of polymers combustion as Group A and Group B. Group A was polymers that revealed slow dripping time but consumed large MHRR. Polymers that classified in Group A were PE, ABS and PS. On the other hand, Group B was fast dripping polymers that showed the dripping time around 7 s in PLA or 10 s in A-PET. However, this Group ignited with low MHRR during testing.

Fig. 9.MHRR and dripping time under the UL-94 vertical testing.

Masayuki Okoshi et al. / Energy Procedia 89 (2016) 38 – 44

3.2. Developmet of inedible wood biomass plastic Kyoto Institute of Technology (KIT) has developed an original alloy compatibilization technology to give cellulose a strength equivalent to that of conventional petroleum-based resins. First, the strong hydrogen bond of the cellulose is loosened with chemical reactions to facilitate the blending of petroleum-based plastic with cellulose molecules. Then, the type of petroleum-based plastic is selected and the amount of its molecules is adjusted, so as to reduce the difference in melt viscosity when blended with cellulose. As a result in Fig. 10, the dispersion of cellulose and petroleum-based plastic is optimized, and compatibility is improved without the use of additives known as compatibilizing agents. As you can see in Fig. 10 (CAP/PC), cellulose and petroleum-based plastic are normally difficult to mix. Looking at the texture of the new biomass plastic under a microscope, however, we can see that the cellulose and petroleum-based plastic are well mixed (Fig. 10 CAP/ABS. This high compatibility results in a plastic with the strength to resist impact and flames. The inedible woody biomass plastic developed by KIT offers a weld strength and flexibility that surpass those of petroleum-based plastics, even though it is cellulose-based and consists of approximately 40 percent plant-based materials by weight. It is also as equally flame resistant as petroleum-based plastics. This biomass plastic has obtained the "BiomassPla" logo from the Japan BioPlastics Association.

model

Fig. 10. Model and SEM photographs of CAP/ABS and CAP/PC.

Fig. 10 demonstrates a model of spindle-like structure (sticking out like the tip of a rope) and is surrounded by cellulose. Both substances are very unevenly dispersed, with separations between the adhered surfaces. This material has low mechanical strength, readily absorbs water, and undergoes significant dimensional change. The grainy features are composed of the petroleum-based plastic. The other areas are composed of cellulose. The image indicates satisfactory dispersion that results in high mechanical strength, low water absorption, and reduced dimensional change. 4. Conclusions Flame retardancy of polyolefin improved by using nano-aluminum hydroxide with the particle size of both micro- and nano-meter. In this reserch, we applied multi-cone calorimeter to inform the flammability of polymer materials. The relationship between heat release rate and the inition time would inform the UL-94 rating of polymer combustion. In aaddition, we can develo cellulose-polymer resin by preparing cellulose based ABS and cellulose based PC.

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