Bio-based prepreg

Abstract

This invention relates to a bio-based furan resin containing a flame retardant.

Description

Technical Field

[0001] The present invention relates to a bio-based furan resin containing a flame retardant.

Background Art

[0002] (Status of the Prior Art) Over the years, the concept of weight reduction has been an important factor in promoting the use of polymer composites in the transportation field. Composites are complex materials because they can optimally combine the properties required for specific applications by variously combining reinforcing materials, resins, and additives. Various machining methods can also be used to process the materials into parts. That is, in order to develop composites, it is necessary to work on the development from various viewpoints, considering the initial raw materials, conversion processes, the possibility of recycling at the end of the life cycle, and so on. Today, due to various factors such as the growing environmental awareness, legal pressure, depletion of fossil fuels, and price increases, new sustainable composites are required for the development of conventional products. The overall advantages of these sustainable composites can be cited as the use of natural-derived renewable materials with lightweight, flexibility in part design, and reduction of manufacturing costs, in addition to the traditional advantages associated with composites. One of the current biggest limitations of composites is the applications that require investigating strategies for flame retardants that enable use in various applications and fields.

[0003] It has become clear that halogen-based additives exhibit the best fire-fighting properties among currently available flame retardants. Until the introduction of new environmental directives, halogen-based additives accounted for most flame retardant solutions. However, their use is now restricted. Therefore, the new trend in flame retardants is based on the use of non-halogen-based substances. Among non-halogen-based flame retardants, aluminum trihydrate is the most widely used, accounting for nearly half of the market by weight, along with other metal hydroxides such as magnesium and phosphorus-based additives. However, a drawback of these currently most popular materials is that they require high concentrations of fillers to achieve flame retardancy, which reduces the processability of composites during manufacturing. [Overview of the project] [Problems that the invention aims to solve]

[0004] Furan resins are thermosetting resin systems obtained by acid hydrolysis of natural resources such as agricultural by-products (pulp, oatmeal, corn cob, cottonseed, sugarcane). These resins are products of acid-catalyzed linear condensation of furfuryl alcohol (FA) or other condensates containing furan rings, and their polymerization is thermally supported. Furan resins exhibit higher thermal stability and chemical resistance compared to other thermosetting resins. Other advantages of furan resins include the absence of organic solvents due to their biomass origin, excellent storage stability, and environmental friendliness. Furthermore, the fire behavior of furan resins is noteworthy; their dense carbonization results in less fume generation. Because furan matrix composites have a high aromatic content, when exposed to fire, unlike polyester resins with a carbonaceous layer conversion rate of 5-10%, 40% of the resin surface becomes a carbonaceous barrier, functioning as a thermal barrier. However, these resins have inferior mechanical properties compared to conventional polyester and epoxy resins. Their low strength and impact strength are particularly noteworthy. Furthermore, furan resins possess properties comparable to conventional phenolic resins, and have the advantage of being made from renewable resources, making them a viable substitute for phenolic resins. Additionally, because furan resins have OH groups in their chemical structure, they can be converted using microwave radiation. This fact represents a significant advancement in composite material processing technology, as it shortens cycle times and allows for control over resin curing.

[0005] The term “prepreg” has long been used to refer to reinforced fibers impregnated with thermosetting resin. In this type of material, the matrix is ​​only partially cured for ease of use, a state known as the “B state” of polymerization, and requires low-temperature storage to prevent complete curing. In this case, various additives and fillers (such as internal release agents, anti-pulling additives, and flame retardants) can be added to the resin to achieve the desired performance. As for the manufacture of prepregs, they are usually produced by the effects of pressure and temperature, which are specified according to the geometry and size of the final prototype [1-5].

[0006] The present invention provides a flame-retardant resin and prepreg that overcome the above-mentioned mechanical drawbacks of furan resin. [Means for solving the problem]

[0007] The resin developed by this invention contains bio-based polyfurfuryl alcohol. [Modes for carrying out the invention]

[0008] combination Since the epoxy resin did not exhibit the desired FST properties, research using polyfurfuryl alcohol (PFA) resin was initiated, and formulation studies have been completed. In these formulation studies, a full staging application was performed at 50°C for two days.

[0009] Poly(furfuryl alcohol) is mixed with a curing agent (crosslinking agent) and subjected to polymerization treatment in an oven at 50°C for 2 days (preferably 50-55 hours). When the dynamic viscosity reaches 1000-5000 Pascals-seconds, a flame retardant and a reinforcing agent (tuffer) are added. Preferably, ammonium polyphosphate is used as the flame retardant and polyethersulfone as the reinforcing agent. The flame retardant is crucial not only for giving the hot melt formulation the ideal viscosity but also for obtaining desirable test results in fire-smoke-toxicity tests. The reinforcing agent (tuffer) is added to give the final composite component mechanical strength. Preferably, the weight ratio is as follows:

[0010] Poly(furfuryl alcohol): 40-60% Ammonium polyphosphate: 20-40% Polyethersulfone: 1-20% Hardener: 1-5%

[0011] In aeronautical (FAR 25.853) and rail (EN 45545) tests, exceptional results were obtained with the bio-based thermosetting resin system of the present invention.

[0012] Test results for epoxy flame retardant formulations under FAR 25.853 and EN 45545-2 show that the bio-based furan resin of the present invention is up to twice as effective;

[0013] The U.S. Federal Aviation Administration (FAA) has developed the FAR 25.853 standard to certify that aircraft materials meet certain performance standards when exposed to heat and flames.

[0014] The following table shows the results of the FAR.25.853 fire smoke toxicity test for composite boards of different thicknesses cured in an autoclave. The test standards, limit criteria, and test results required to pass the test are shown in Table 1 below. These are the test results for 1-layer, 2-layer, and 8-layer prepreg samples using the resin of the present invention. In this example, the total percentage of resin in the prepreg sample is 38%. Table 2 shows the results for oven-cured boards.

[0015] The criteria shown in the table are explained below. DS Max: Maximum specific optical density obtainable within 20 minutes of testing. CITG: Conventional Toxicity Index Marhe: Maximum average heat release rate Minimum critical flux in CFE quenching DS 4 Specific optical density after 4 minutes VOF4 VOF4 = DS1min + DS2min + DS3min + (DS4min / 2) **

[0016] [Table 1]

[0017] [Table 2]

[0018] As shown in Tables 1 and 2, the resin of the present invention obtained results far below the reference requirements.

[0019] In Table 3, the results of the bio-based furan resin of the present invention are compared with epoxy resins and phenolic resins included in the prior art. As can be seen from these results, the bio-based furan resin of the present invention showed unexpected results compared with epoxy resins and phenolic resins.

[0020]

Table 3

[0021] The EN 45545 standard is a standard for meeting and harmonizing the fire safety of railways. Railway vehicles are classified according to the level of fire risk associated with their design and operation. The risk levels are three levels: HL1, HL2, and HL3. HL1 has the lowest requirements, HL3 has the highest requirements, and HL3 is expected from the flammability performance; according to the European Railway System Directive (EN 45545), train parts represent different parts with symbols such as R1, R7, and R17.

[0022] Name Test Method Inner vertical surface of R1 ISO 5658-2 CFE Internal horizontal ISO 5660-1 Downward surface ISO 5659-2 Ds VOF4 ISO 5659-2 CIT Inner surface of the passage of R7 - Type B Air duct of the locomotive Outer body shell wall Outer surface of the enclosure including the following Technical facilities Under the frame of the outer body shell External passage Features of the exterior design Container attached to the lower part of the frame Outer surface of the passage Truck structure and parts Arc Splash Barrier Material R17 Cabinet Housing - Exterior ISO 5658-2 ISO 5660-1 ISO 5659-2 ISO 5659-2

[0023] Tables 4 and 5 show the EN 45545-2 test results for the bio-based furan resin and epoxy resin of the present invention. The values ​​in Table 4 show that the resin of the present invention gives HL3 class results in all evenings compared to the epoxy resin.

[0024] [Table 4]

[0025] [Table 5]

[0026] Table 6 shows the results for an 8-layer resin sample cured in an autoclave, and Table 7 shows the results for an 8-layer resin sample cured in an oven.

[0027] [Table 6]

[0028] [Table 7]

[0029] References 1. Patricia Ares Elejoste, Alexandra Allue, Jesus Ballestero, Santiago Neira, Jose Luis Gomez-Alonso, and Koldo Gondra: Development and characterization of sustainable prepregs with improved fire behavior based on furan resin and basalt fiber reinforcement. 2. Das, O.; Babu, K.; Shanmugam, V.; Sykam, K.; Tebyetekerwa, M.; Neisiany, RE; Forsth, M.; Sas, G.; Gonzalez-Libreros, J.; Capezza, AJ. Natural and industrial waste for sustainable and renewable polymer composite materials. 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. 4. Andrew, JJ; Dhakal, H., Sustainable Bio-Based Composites for Advanced Applications: Recent Trends and Future Opportunities—A critical review. Compos. Part C Open Access 2021, 7, 100220. [CrossRef] 5. Mohanty, AK; Vivekanandhan, S.; Pin, J.-M.; Misra, M., Composite materials from renewable and sustainable resources: challenges and innovations. Science 2018, 362, 536-542. [CrossRef] [PubMed]

Claims

1. a. 40-60% by weight of poly(furfuryl alcohol); b. 20-40% by weight of flame retardant; c. 1-20% by weight of a reinforcing agent; d. 1-5% by weight of a hardening agent A furan resin containing furan resin.

2. The resin according to claim 1, wherein the flame retardant is ammonium polyphosphate.

3. The resin according to claim 1, wherein the reinforcing agent is polyethersulfone.

4. a. A step of mixing the curing agent with poly(furfuryl alcohol) and polymerizing it at 50°C; b. Preferably, a step to obtain a dynamic viscosity of 1000 to 5000 Pascal seconds at the end of polymerization; c. Step of adding flame retardants and reinforcing agents. A method for producing furan resin according to claim 1, including the method described in claim 1.

5. The method according to claim 4, wherein polymerization at 50°C is carried out for 50 to 55 hours.

6. A prepreg comprising the resin described in claim 1.

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