JEC COMPOSITES MAGAZINE - Issue #63 - March 2011 - 90

prepreg

prepreg machinery from Century Design, Inc. (CDI, San Diego, USA) that can perform both filming and impregnation processes. The plant, whose lay-out is shown in Figure 5, can produce up to 320 mm wide tape at a maximum impregnation speed of 20 m/min. The plant is equipped with three couples of heated rolls that, along with two heated platens, keep the resin warm during the compaction process. The maximum operating temperature achievable is of 180°C. The last chill rolls and platen cool down the prepreg that is wound around the take-up roll. Tab.3: Hot melt process parameters
Process parameters The Ep60-Nov18 resin was characterized by a viscosity Heated platen temperature 55°C low enough to avoid the Heated roll temperature 50°C preliminary filming step, allowing a simpler process Compaction roll gap 0.42 mm where filming took place Compaction roll pressure 414 kPa simultaneously with the impregnation step. The Impregnation speed 3 m/min liquid resin was cast directly between two dry siliconed paper tapes, while the carbon fibres were pulled simultaneously between the same paper tapes. Process parameters are listed in Table 3. A 15 metre long and 20 cm wide prepreg tape was produced. It was characterized by a fibre content of 49 ± 1%w (216-225 g/m²) and a resin content of 50 ± 3%w (212-238 g/m²). It showed good impregnation of the reinforcement.

based samples. These results are the consequence of both the higher toughness of the cardanol-based matrix, as shown by impact tests, and the similar compatibility between carbon fibres and both epoxy systems.

Conclusions
In this work, Cimteclab’s know-how in the development of cardanol derivatives and Technologycom’s expertise in the field of prepregs were combined to develop an epoxy prepreg made using the Novocard XFN-1400 cardanol-based curing agent. Two different epoxy systems showing adequate tackiness and viscosity at room temperature for use as prepreg matrix were studied by a preliminary DSC analysis. The epoxy systems were cured with 18 phr of Novocard XFN-1400, employing an imidazole catalyst. The composition that showed the highest Tg (111°C) was chosen as matrix for a unidirectional carbon fibre prepreg. Before manufacturing the prepreg, an Izod impact test was carried out on the novolacbased epoxy resin in order to compare its performance with that of a similar amine-cured system. The results obtained showed a 163% higher toughness when the novolac is used as epoxy curing agent. The subsequent manufacture of the prepreg by the hot melt process, whose parameters were set in accordance with rheological measurements of the cardanolbased resin, also revealed the high processability of this kind of epoxy system. Flexural and short beam tests on specimens cut from a composite laminate made by pressclaving 16 prepreg sheets showed that no significant mechanical changes occur when 18 phr of Novocard XFN-1400 is used as epoxy curing agent instead of common amine hardeners. This study demonstrated that epoxy prepregs using a cardanol derivative as curing agent can be used in the manufacture of secondary structures for aeronautical, wind energy, transport and sporting applications. n
Web-site: www.cimteclab.it; www.technologycom.it Contacts: info@cimteclab.it; franco.innocente@technologycom.it References 1. P. Blazdell, Interdiscipl. Sci. Rev., 25 (2000), 220. 2. M. T. Harvey, S. Caplan, Ind. Eng. Chem., 32 (1949), 1306. 3. D. Wasserman, C. R. Dawson, Ind. Eng. Chem., 37 (1945), 396. 4. S. K. Shukla, A. Maithani, D. Agarwal, D. Srivastava, Pop. Plast. Packag., 47 (2002), 58. 5. Y. C. Chen, Y. W. Chiu, K. F. Lin, J. Polym. Sci. Part A: Polym. Chem., 37 (1999), 3233. 6. M. S. Heise, G. C. Martin, Macromolecules, 22 (1989); 99. 7. M. Ito, H. Hata, K. Kamagata, J. Appl. Polym. Sci., 33 (1987), 1843. 8. P. Campaner, D. D’Amico, L. Longo, C. Stifani, A. Tarzia, J. Appl. Polym. Sci.,114 (2009), 3585.

jec composites magazine / No63 March 2011

Results of the mechanical tests on the composite laminate The mechanical features of specimens cut from the composite laminate, made from 16 overlapped prepreg sheets, were investigated through both flexural and short beam tests. For comparison purposes, a similar carbon fibre reinforced laminate, using the Ep50+Am system as matrix, was also prepared and tested. Flexural and short beam test results, as reference to composites with a standardized fibre volume content of 50%, are reported in Table 4 and Tab.4: Flexural test results Table 5, respectively. Bending Bending Both flexural modulus and Composite strength modulus matrix flexural strength of the (MPa) (GPa) cardanol-based specimens 896 ± 66 EP60+NOV18 69 ± 4 were a bit lower than Ep50+Am 73 ± 6 907 ± 89 those of the amine-cured epoxy laminate. In fact, Tab.5: Short beam test results the presence of the cardanol-based novolac Composite Shear strength reduces the cross-linking matrix (MPa) density of the cured epoxy resin, resulting in a slight EP60+NOV18 57 ± 1 lowering of both modulus Ep50+Am 51 ± 4 and strength at break. On the other hand, slightly higher strength values were recorded in short beam tests for the Novocard XFN-1400

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JEC COMPOSITES MAGAZINE - Issue #63 - March 2011

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