Bio-based and flame retardant?

Transcription

1 EMG Clariant Feature Article on FR for Biobased Plastics/Composites Page 1 of 5 Bio-based and flame retardant? Fire protection for bio-based polymers and plastics composites can ensure that renewable alternatives meet high-end industry requirements. But do proven solutions exist to maintain the improved environmental features with effective, more environmentally-friendly flame retardants? By dr. muriel rakotomalala, elke schlosser, dr. sebastian Hörold Bio-based polymers are here to stay. With a total capacity forecast of 12 million tons by 2020 a tripling of 2011 levels [1] there is definite interest in integrating these polymers into industrial applications. As early as 2010, approximately 20 different bio-based polymer families were commercial, while another 6 were at pilot scale. Around half of these were bio-based versions of well known traditional polymers, while the other half were new to the market, for example, polylactic acid (PLA) specialties for electronics and automotive [2] applications. Within the E&E and Building & Construction segments in particular, flammability of the plastics used is a priority issue. To gain acceptance in these industries, bio-based polymer matrices and plastic composites must pass the same standards as their petrochemical counterparts, such as UL94 Vertical Test and the Limit Oxygen Index (LOI) fire test. Consequently there is a need for advanced halogen-free flame retardants that align with the environmental and health profile of the compound they are treating. Initiatives such as the Design for Environment projects of the U.S. Environmental Protection Agency and the ENFIRO project sponsored by the European Union, are identifying nonhalogenated flame retardants for different materials and conclude that next to a favorable environmental and health profile these flame retardants also represent real alternatives from a technical and commercial view. This is a step forward in easing the decision-making and selection of safer, more environmentally-conscious solutions in many application areas. Research institutions, but also flame retardant producers and compounders are attending to the development and/or evaluation of halogen-free flame retardant alternatives for bio-based plastics and composites. Halogen-free in the E&E and Building sectors Demand for biomass derived plastics is certainly rising in the E&E and Building & Construction industries. Of potential relevance to these industries, academic research groups are focusing on halogen-free flame retardants, often in combination with renewable fillers such as wood, lignin, starch and oyster shell, for the bio-based plastics and composites of interest. Here, it is being shown that non-halogenated flame retardants have proven efficiency in bio-based polymer matrices, providing mechanical properties fit to use for certain applications. Flame retardant products from specialty chemicals producer Clariant, marketed under the name Exolit, have been used in both independent third-party research and internally-led research to assess the effectiveness of non-halogenated solutions. As a founding member of pinfa (the Phosphorus, Inorganic and Nitrogen Flame Retardants Association) and a Sector Group within Cefic (the European Chemical Industry Council), Clariant has shown its commitment to continuously improving the environmental and health profile of its flame retardant products. Halogen-free Exolit products can ensure effective flame retardancy in key bio-based polymers and composites used in Building & Construction and E&E applications. This is demonstrated in the following examples.

2 EMG Clariant Feature Article on FR for Biobased Plastics/Composites Page 2 of 5 Wood-plastic Composites European produced Wood-Plastic Composites (WPCs) are primarily used for extrusion purposes in the decking market (67% of market production). This is followed by their use as natural fiber composites in automotive interior parts (23%). [3] Ammonium polyphosphate flame retardant Exolit AP 422 can be used to confer flame resistance to polyolefin compounds. It is an efficient flame retardant that maintains the physical properties of WPC compounds and is easy to process. Exolit AP 422 leads to increased char formation, functioning as a protective layer, assisted by intumescence or swelling/foaming of the thermoplastic material on exposure to flame. This effect can lead certain applications to be self-extinguishing. Exolit AP 422 has a favorable environmental and health profile, and is both halogen-free and biodegradable. [4] For building and construction applications, the performance of wood-filled polypropylene (70% wood / 30% PP) against German Fire Test DIN 4102 B2 shows positive indication for effective fire protection using Exolit AP 422 treated compounds. Five specimens measuring 190mm x 90mm were assessed with and without flame retardant. As shown in Figure 1, DIN 4102 B2 was passed but the specimens burnt completely. The specimens in Figure 2 of 55% wood, 30% PP and 15% Exolit AP 422 were self-extinguishing. For the E&E sector, the performance of 60% wood-based WPC in the UL94 Test for electrical and electronic applications shows possibilities to achieve V-0 classification using a minimum of 10% Exolit AP 422 in the compound, as highlighted in Table 1. pla Possibilities to develop bio-based flame retardant PLA have also been revealed. In certain electrical and electronic applications, the selection of a flame retardant package can improve the fire resistance of PLA. One laptop computer manufacturer, for example, has developed a model with a cover made from a flame-retardant blend of PLA and polycarbonate. [5] Similar blends are under development for other office equipment. A fully independent study carried out at Unité Matériaux et Transformations (UMET, Lille University, France) investigated the efficiency of Exolit AP in PLA reinforced with different biobased fillers that could act as a char former in the intumescent system. Both lignin and starch from a different source allowed the material to reach the UL94 V-0 classification, while the non-reinforced material only achieved a V-2 rating (see Table 2). Moreover both lignin and starch increase the LOI and showed a reduction of both peak of heat release (phrr) in the cone calorimeter test. AP has therefore been shown to be an effective flame retardant additive for a bio-based plastic reinforced with bio-based fiber.

3 EMG Clariant Feature Article on FR for Biobased Plastics/Composites Page 3 of 5 polyamides (pa) Phosphinates can be used to provide reliable flame retardants in applications involving elevated temperatures. Flame retardants based on aluminum salts of diethylphosphinic acid (DEPAL) developed and marketed by Clariant under the Exolit OP name, are used most widely to incorporate non-halogenated flame retardancy into engineering plastics. In most cases, a relatively small loading is sufficient to meet stringent fire safety regulations. In an in-house study, Clariant investigated the effectiveness of Exolit OP products in partially biobased PA10T commercialized by Evonik [6]. This polyphthalamide, whose monomers are largely derived from naturally sourced raw materials, significantly reduces the CO₂ emissions compared to pure petroleum-based polyamides. For this study, PA10T was compounded with 30% glass fibers and different flame retardant systems based on Exolit OP grades in order to evaluate the both flame retardancy and mechanical properties. In comparison to the commercially available non-flame retardant glass reinforced PA10T [7] that reaches the classification HB in the UL94 test, the compound with the new Exolit product Exolit OP 1400 (TP) [8] showed the best balance between flame retardancy efficiency and mechanical properties. The comparison is shown in Table 3. Another bio-based PA is PA410 commercialized by DSM under the tradename EcoPaXX *. The evaluation of two Exolit OP systems in PA410 reinforced with 30% glass fiber showed that both systems could reduce the flammability of EcoPaXX while maintaining the impact strength required for E&E applications. However, the highest classification V-0 could not be achieved for all thicknesses, see Table 6. This demonstrates the challenge of developing a compound that simultaneously reaches the highest flammability classification while maintaining good mechanical properties. phbv Poly 3-hydroxybutyrate-co-3-hydroxyvalerate, more commonly known as PHBV, is a biodegradable, non-toxic plastic product alternative to synthetic non-biodegradable polymers made from petroleum. Its low thermal stability is often seen as a drawback. A study carried out at the BAM Federal Institute for Materials Research & Testing, focused on a two component flame retardant system to achieve a UL94 V-0 rating and with a relatively high oxygen index (LOI) value. In comparison to the non-flame retardant compound both peak of heat release (phrr) and total heat release (THR) were reduced (Figure 3). FT- IR analysis demonstrated that the combination of Exolit OP 1240 and Iron Trioxide (Fe) contribute to formation of an additional residual char that can act as a protection layer between the heat source and the combustible bio-based plastic. [10]

4 EMG Clariant Feature Article on FR for Biobased Plastics/Composites Page 4 of 5 Market availability The acceptance of halogen-free flame retardant solutions within the focus industries of E&E and Building & Construction is not yet widely known. The presence of commercially available compounds incorporating more environmentally-compatible flame retardants shows that there is a demand for such materials. However, availability is currently limited, with only a few compounders advancing into this area. The following examples provide a selection of halogen-free flame retardant bio-based plastics currently available. EuroStar Engineering Plastics has introduced flame retarded thermoplastic compounds based on a renewable oyster shell filler using Clariant s Exolit AP non-halogenated flame retardants. [11] DSM s EcoPaXX development is a polyamide 410 that not only derives from 70% renewable materials but is also proven to be 100% carbon neutral from cradle-to-gate. One halogen-free grade reaches UL94V-0 classification and is promoted for E&E applications. [12] In addition, under the general term GreenLine, EMS-GRIVORY * markets a wide range of bio-based polyamides which are partially or wholly manufactured from renewable raw materials. [13] GreenLine includes two halogen-free flame retarded grades of a bio-based PPA that achieve UL94 V-0 rating. The indications are clear that there is a growing interest in bio-based plastics and composites with halogen-free flame retardants. However, there is a need for more investment into the development of new solutions. The highlighted benefits and the feasibility of compounding bio-polymer materials with non-halogenated flame retardants will encourage further manufacturers to become more environmentally-conscious in their product offerings. * * * Trademark of Clariant registered in many countries * Registered 3rd party trademark

5 EMG Clariant Feature Article on FR for Biobased Plastics/Composites Page 5 of 5 The Authors dr. muriel rakotomalala is technical marketing manager, Flame retardants, and at Clariant in this position since muriel.rakotomalala@clariant.com elke schlosser is technical marketing manager, Flame retardants, and at Clariant in this position since elke.schlosser@clariant.com dr. sebastian HÖrold is Head of development & application technology Plastics, Flame retardants, and at Clariant in this position since 2001 sebastian.hoerold@clariant com Figure Captions Figure 1. Fire behavior of 70% wood-filled polypropylene without flame retardant DIN 4102 B2 test passed, specimen (shown after 60 s) burns off completely Figure 2. Fire performance of 55% wood-filled polypropylene with 15% Exolit AP 422: Self-extinguishing after 30 s Figure 3. Cone calorimetric data of PHBV with Exolit OP 1240 (designated as AlPi) and iron oxide as flame retardant additives Figure 4. The non-halogenated flame retardants of Clariant s Exolit brand are ideal for use in combination with bio-based plastics and renewable fillers, such as wood, lignin, starch and even ground oyster shell Note: All figures and table courtesy Clariant literature [1] market Based study on Bio-based Polymers in europe, nova-institut GmbH, version [2] the state-of-the-art on Bioplastics: Jan Th. J. Ravenstijn, 2010, Polymedia Publisher GmbH [3] market developments of and opportunities for biobased products and chemicals. Final report december authors: dammer, m. Carus, a. raschka, l. scholz, nova-institut GmbH [4] inorganic compound, causes no biological oxygen depletion, rapidly decomposes to ammonium and phosphate in ground and sludge. source: uba research report, december 2000, pp 112. [5] Biopolymers: Polylactic acid and flame retardancy, [6] evonik industries 2012 vestamid Ht plus m3000 datasheet [7] evonik industries 2012 vestamid Ht plus m3033 datasheet [8] Clariant s new development with clearly higher thermal stability and reduced plate-out [9] datasheet dsm ecopaxx [10] study by dr e Gallo with exolit op 1240 (aka aipi) published in eur. Pol.J.47(7) [11] [12] [13] [Ends]