Biobased prepreg

Abstract

The invention relates to a biobased furan resin comprising a flame-retardant.

Description

[0001]DESCRIPTION BIOBASED PREPREG Technical Field The invention relates to a biobased furan resin comprising a flame-retardant. State of the Art For years, the concept of light weight has been a key element in promoting the use of polymer composites in the transport sector. Composites are complex materials because reinforcement, resin and additives can be combined in numerous ways to provide the optimum combination of properties required for a particular application. Many different machining methods are also available for turning materials into parts. This means that in order to develop composites, it is necessary to approach their development from different perspectives, considering the initial raw materials, the transformation process, and the possibilities of recycling at the end of their life cycle. Today, various factors such as increasing environmental awareness, legal pressures, depletion of fossil fuels and price increases lead to the search for new sustainable composites for the development of conventionally made products. The overall benefits of these sustainable composites can be listed as the use of naturally sourced and renewable materials with the traditional advantages associated with composites, as well as lightness, flexibility in part design and reduction in production costs. One of the biggest current limitations of composites is the applications that make it necessary to investigate flame-retardant strategies that enable their use in different applications and sectors. Of all the fire retardants currently on the market, it has been shown that the best fire-fighting properties are achieved with halogenated additives. Halogenated additives constituted most flame-retardant solutions until new environmental directives were introduced. But now their use is restricted. Therefore, new trends in flame-retardant additives are based on the use of non-halogenated substances. Among non-halogenated flame-retardants, aluminum trihydrate is the most widely used, accounting for almost half of the market by weight, along with other metal hydroxides such as magnesium and phosphorus-based additives. However, the disadvantage of these currently most popular materials is the necessity to use a high concentration of filler to achieve flame retardancy, which reduces the ease of processing the composite during the production of the composites. Furan resins are thermosetting resin systems obtained from the acid hydrolysis of natural resources such as agricultural by-products (pulp, oatmeal, corncob, cotton seed, sugarcane). 1   These resins are the product of acid-catalyzed linear condensation of furfuryl alcohol (FA) or other condensates containing furan rings, and their polymerization is supported by heat. Furan resins exhibit high thermal stability and chemical resistance compared to other thermosetting resins. Other advantages of furan resins include the absence of organic solvents, good storage stability, and eco-sustainability as they are obtained from biomass. In addition, the fire behavior of furan resins is noteworthy, as they have little tendency to emit fumes due to their dense charring. When furan matrix composites are exposed to fire due to their high aromatic content, 40% of the resin surface turns into a carbonaceous barrier that acts as a thermal barrier, unlike polyester resins with 5-10% conversion in the carbonaceous layer. However, such resins show worse mechanical properties compared to conventional polyester and epoxy resins. Especially low strengths and impact strengths are noteworthy. In addition, they have properties comparable to traditional phenolic resins and can substitute them with the advantage of being from renewable sources. In addition, furan resins can be converted by microwave radiation, as they have OH groups in their chemical structure. This fact constitutes a significant advance in composite processing technologies as it will reduce cycle times and control resin hardening. The term "prepreg" refers to a reinforcing fiber impregnated with a thermosetting resin long before it is used. In this type of material, the matrix is only partially cured for ease of use, and this is known as the "B state" of polymerization and requires cold storage to prevent complete curing. In this case, the resin can be formulated with different additives and fillers (internal release agents, anti-pulling additives, flame-retardant, etc.) to achieve the desired performance. When it comes to prepreg production, these are usually created by the effect of pressure and temperature defined according to the geometry and size of the final prototype [1- 5]. The invention provides a flame-retardant resin and prepreg in which the above-mentioned mechanical disadvantages of furan resin are eliminated. Detailed Description of the Invention The resin developed by the invention comprises biobased poly furfuryl alcohol. Formulation Since the epoxies did not show the desired FST properties, studies were started with Poly furfuryl Alcohol (PFA) resin and the formulation study was completed. Full staging application at 50°C for 2 days was used for this formulation study. 2   Poly (furfuryl alcohol) is mixed with a curing agent (crosslinker) and subjected to a 50°C oven polymerization process for two days (preferably 50-55 hours). When the dynamic viscosity of 1000-5000 Pascal.second is reached, flame-retardant agent and toughener agent (toughener) are added. Preferably, Ammonium polyphosphate is used as flame-retardant agent and Polyether Sulfone as toughener agent. In addition to providing an ideal viscosity for the hot-melt formulation, the flame-retardant agent is also of great importance in obtaining the desired test results for Fire-Smoke-Toxicity tests. The toughener agent (toughener) was added to give mechanical strength to the final composite part. Preferably the proportions by weight are given below. Poly (furfuryl alcohol): 40-60% Ammonium polyphosphate: 20-40% Polyether sulfone: 1-20% Curing Agent: 1-5% Extraordinary results were obtained in aviation (FAR 25.853) and railway (EN 45545) tests with the biobased thermoset resin system of the invention. When we compare the FAR 25.853 and EN 45545-2 test results of the Epoxy Flame-retardant formulations, it is seen that the biobased furan resin results of the invention are up to 2 times better; The American Federal Aviation Administration (FAA) has developed the FAR 25.853 standard to prove that aircraft materials meet certain performance criteria when exposed to heat or flame. The table below shows the FAR.25.853 Fire Smoke Toxicity test results of composite plates of different thicknesses cured in the autoclave. The test standards, limit criteria and test results required to pass the test are given in Table 1 below. These are the test results of 1 layer, 2 layer and 8-layer prepreg samples obtained with the resin subject to the invention. The total percentage of resin in the prepreg sample used in this example is 38%. Table 2 shows the results of the oven-cured plates. The explanations of the criteria given in the tables are as follows. DS Max: Maximum specific optical density obtained within 20 minutes of test time. CITG: Conventional toxicity index Marhe: Maximum average heat emission rate 3   CFE Minimum critical flux in quenching DS 4 Specific optical density recorded at 4 minutes VOF4 VOF4 = DS1min + DS2min + DS3min + (DS4min / 2)** Table 1: Results of FAR 25.843 composite plates. Standard Criteria Requirements 8 Layers 1 Layer 2 Layers FAR 25.853, F Part I Burn length (mm) ≤ 150 16 2 22 FAR 25.853, F Part IV HRRmax (kW / m²) ≤ 65 17.9 16.2 11.4 THR2minutes ≤ 65 11.3 8.3 11.1 (kW.min / m²) FAR 25.853, F Part V Dm (Ds max) ≤ 200 5 4 4 AITM 3-0005 (issue 2) [CO] (ppm) / 24 32 41 [SO2] (ppm) < 100* 2 1 1 [NOx] (ppm) < 100 4 4 5 [HF] (ppm) < 100 0 0 0 [HCl] (ppm) < 150 0 0 0 [HCN] (ppm) < 150 0 0 0 Table 2: FAR 25.843, Results of oven cured composite plates. Standard Criteria Requirements 1 Layer 2 Layers FAR 25.853, F Part I Burn length (mm) ≤ 150 4 3 FAR 25.853, F Part IV HRRmax (kW / m²) ≤ 65 12.5 12.4 THR2minutes ≤ 65 11.6 11.4 (kW.min / m²) FAR 25.853, F Part V Dm (Ds max) ≤ 200 2 4 AITM 3-0005 (issue 2) [CO] (ppm) / 26 35 [SO2] (ppm) < 100* 1 1 [NOx] (ppm) < 100 3 5 [HF] (ppm) < 100 0 0 [HCl] (ppm) < 150 0 0 [HCN] (ppm) < 150 2 6 As can be seen in Tables 1 and 2, the results far below the required values of the criteria were obtained with the resin subject to the invention. 4   In Table 3, the biobased furan resin results of the invention are compared with the epoxy and phenolic resins included in the known state of the art. As can be seen from these results, the biobased furan resin subject to the invention reveals unexpected results compared to epoxy and phenolic resins. Table 3: FAR 25.853 comparative test results Standard Criteria Requirements Epoxy Phenolic Biobased Furan Resin FAR 25.853, F Part I Burn length (mm) ≤ 150 ≤ 150 16 FAR 25.853, F Part IV HRRmax (kW / m²) ≤ 65 54.5 ≤ 40 17.9 THR2minutes ≤ 65 66.1 50 11.3 (kW.min / m²) FAR 25.853, F Part V Dm (Ds max) ≤ 200 84 ≤ 15 5 AITM 3-0005 (issue 2) [CO] (ppm) / 24 [SO2] (ppm) < 100* 2 [NOx] (ppm) < 100 4 [HF] (ppm) < 100 0 [HCl] (ppm) < 150 0 [HCN] (ppm) < 150 0 The EN 45545 standard is a standard used to meet and harmonize the fire safety of Rolling stock is classified according to the level of fire hazard associated with their design and operation. The three hazard levels are HL1, HL2 and HL3. HL1 is the lowest requirement and HL3 is the highest requirement, and the expectation from flammability performance is HL3  According to the European Rail Systems Directive (EN 45545), train components symbolize different parts as R1, R7 and R17. Name Test Method R1 Inner vertical surfaces ISO 5658-2 CFE internal horizontal ISO 5660-1 downward facing surfaces ISO 5659-2 Ds VOF4 ISO 5659-2 CIT R7 Internal surfaces of passages - Type B Air ducts in locomotives Outer body shell walls 5   external surfaces of enclosures containing Technical equipment Under the frame of the outer body shell Outer passages Exterior design features Container mounted to the bottom of the frame Outer surface of passages Bogie structure and parts Arc splash barrier material R17 Cabinet housing – Exterior surfaces ISO 5658-2 ISO 5660-1 ISO 5659-2 ISO 5659-2 In Tables 4 and 5, EN 45545-2 test results of the biobased furan resin and epoxy resin subject to the invention are given. The values in Table 4 show that the resin of the invention gives HL3 class results in all evenings compared to the epoxy resin. Table 4: EN 45545-2 test results for biobased furan resin Biobased Furan R1 R7 R17 Resin Ds max. 51.5 HL3 HL3 HL3 CITg 0.1 HL3 HL3 HL3 MARHE 7.7 HL3 HL3 HL3 CFE 50 HL3 HL3 HL3 Ds 4 32 HL3 HL3 HL3 VOF4 61 HL3 HL3 HL3 Table 5: EN 45545-2 test results for epoxy resin Requirements Epoxy Mean Values R1 R7 R17 Ds max. ≤300 300-600 HL2 HL3 HL3 CITg ≤0.75 0.3-0.6 HL3 HL3 HL3 MARHE ≤60 50-70 HL3 HL3 HL3 6   CFE 20≥ 40-50 HL3 HL3 HL3 Ds 4 ≤150 200-400 HL2 HL3 HL3 VOF4 ≤300 500-600 HL2 HL3 HL3 Table 6 shows the results of the 8-layer resin sample cured in the autoclave, while Table 7 shows the results of the 8-layer resin sample cured in the oven. Table 6: Railway standard (EN45545) results of composite plates cured in autoclave. Biobased Furan R1 R7 R17 Resin (8 layers) Ds max. 51.5 HL3 HL3 HL3 CITg 0.1 HL3 HL3 HL3 MARHE 7.7 HL3 HL3 HL3 CFE 50 HL3 HL3 HL3 Ds 4 32 HL3 HL3 HL3 VOF4 61 HL3 HL3 HL3 Table 7: Railway standard (EN45545) results of oven cured composite plates Biobased Furan R1 R7 R17 Resin (8 layers) Ds max. 38.1 HL3 HL3 HL3 CITg 0.03 HL3 HL3 HL3 MARHE 0 HL3 HL3 HL3 CFE 50 HL3 HL3 HL3 Ds 4 22.1 HL3 HL3 HL3 VOF4 52.7 HL3 HL3 HL3 References 1. Patricia Ares Elejoste, Alexandra Allue, Jesus Ballestero, Santiago Neira, José Luis Gómez- Alonso and Koldo Gondra; Development and Characterisation of Sustainable Prepregs with Improved Fire Behaviour Based on Furan Resin and Basalt Fibre Reinforcement 2. Das, O.; Babu, K.; Shanmugam, V.; Sykam, K.; Tebyetekerwa, M.; Neisiany, R.E.; Försth, M.; Sas, G.; Gonzalez-Libreros, J.; Capezza, A.J.; et al. Natural and industrial wastes for sustainable and renewable polymer composites. Renew. Sustain. Energy Rev. 2022, 158, 112054. 3. Islam, S.; Islam, S.; Hasan, M. Natural Fiber Reinforced Polymer Composites as Sustainable Green Composites. Ref. Modul. Mater. Sci. Mater. Eng.2022. 7   Andrew, J.J.; Dhakal, H. Sustainable biobased composites for advanced applications: Recent trends and future opportunities – A critical review. Compos. Part C Open Access 2021, 7, 100220. [CrossRef] Mohanty, A.K.; Vivekanandhan, S.; Pin, J.-M.; Misra, M. Composites from renewable and sustainable resources: Challenges and innovations. Science 2018, 362, 536–542. [CrossRef] [PubMed]

Claims

CLAIMS 1. A furan resin, characterized in comprising, a. 40-60% by weight Poly (furfuryl alcohol) b. 20-40% by weight flame-retardant agent c. 1-20% by weight of toughener agent d. 1-5% by weight curing Agent.

2. A resin according to Claim 1, characterized in that the flame-retardant agent is ammonium polyphosphate.

3. A resin according to Claim 1, characterized in that the toughener agent is polyether sulfone.

4. A furan resin production method according to Claim 1, characterized in comprises steps of, a. Mixing the curing agent with poly (furfuryl alcohol) and subjecting it to polymerization at 50°C b. Preferably obtaining 1000-5000 Pascal.second dynamic viscosity at the end of polymerization c. Adding flame-retardant agent and toughener agent.

5. A method according to Claim 4, characterized in that the polymerization at 50°C takes 50-55 hours.

6. A prepreg characterized in comprising resin according to Claim 1.

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