Study On The Toughing And Reinforcing Effects Of Nanomontmorillonite-filled Nylon11 Composites

Preparation of polymer composites is one of the important methods to realize high performance of polymer materials. In this paper, POE-g-MAH/POE and nanomontmorillonite were used as the impact modifier for the nylon 11. The relationship between the structure and properties of nylon 11 toughened and reinforced by montmorillonite, POE-g-MAH/POE respectively or together was studied systematically. Deep investigation and analysis on high performance and theory of nylon 11 was carried out. The method of essential work of fracture was used for the first time to characterize the toughening mechanism of nylon11/montmorillo-nite duplicate nanocomposites and nylon 11/POE-g-MAH/montmorillonite ternary nanocom-posites, providing more information on the characterization of the fracture behavior for the polymer material. Meanwhile, it has pointed out an approach to enhance the toughness through improving the specific essential work of fracture and specific essential work of fracture respectively. And it studied the toughening mechanism of nylon 11/POE-g-MAH/montmorillonite ternary nanocomposites and obtained the critical particle space for the brittle-tough transformation and the lower limit for the diameter of elastomer to toughen the material. These information enriches badly the toughen theory for the nylon 11/POE-g-MAH/montmorillonite ternary composites which can be used for development and application the nylon composites with high properties. The main results are listed as following:1. Effect of montmorillonite content on the configuration and structure, mechanical property, rheological property, crystallization property and the thermal decomposition temperature was investigated. The results are listed as following:The exfoliated nanocomposites were obtained when the montmorillonite content was 2% while the intercalated nanocomposites were obtained when the montmorillonite content was more than 2%.The impact strength, specific essential work of fracture and specific plastic work all showed the trend of increasing at first then decreasing with the increase of the montmorillonite content. When the montmorillonite content was 2%, the impact property, specific essential work of fracture and specific plastic work were all up to the max. The impact strength was 16.56KJ/m2 which was 2.5 times as much as the pure nylon11's. The tensile strength, flexural strength and flexural modulus increased gradually while breaking elongation ration decreased with the increase of the montmorillonite content.It was obtained from analyzing the rheological curve of the nylon 11 and its nanocomposites that:nylon 11 and nylon 11/montmorillonite nanocomposites were both pseudo-plastic fluid. At the temperature of 230℃-245℃.the non-newtonian index was in the rang of 0.49-0.85. The apparent viscosity of nylon 11 decreased with the adding of montmorillonite. At high shear rate, the effect of montmorillonite on viscosity decreased. The temperature influence on the rheological property of the plastic melts decreased because the viscous activation energy for nylon 11 decreased with adding montmorillonite.When the montmorillonite content was 2%, the crystal form of nylon 11 had not changed. However, crystal form of nylon 11 transferred fromγtoαwith the increase of montmorillonite content. The organic montmorillonite played the role of nucleating agent on the nylon 11 matrix to destroy the spherulitic structure of nylon 11 causing the change of the crystal morphology for nylon 11. The Avrami equation can describe the isothermal crystallization behavior well of nylon 11 and its nanocomposites.Thermogravimetric analysis showed that when the montmorillonite content was 2%, the thermal decomposition temperature for nanocomposites increased by 27℃comparing with the pure nylon 11's.2. The effect law of POE-g-MAH content, montmorillonite content and blending order on the mechanical property, rheological property, crystallization property of nylon 11/POE-g-MAH/montmorillonite nanocomposites were studied systematically. The research result showed that:The impact strength specific essential work of fracture and specific plastic work of the nanocomposites increased with the increase of the POE-g-MAH content. When the POE-g-MAH content was 20%, the impact strength for the nanocomposites was 36.32KJ/m2 which was 5.5 times as much as the impact strength of 6.62 KJ/m2 for pure nylon 11. The tensile strength, flexural strength and flexural modulus decreased gradually with the increase of POE-g-MAH content. However, the breaking elongation ration increased at first then decreased with the increase of the POE-g-MAH content and was up to the max when the POE-g-MAH content was 20%.With the increase of the montmorillonite content, the impact strength decreased while the specific essential work of fracture of the nanocomposites increased at first then decreased and was up to max when the montmorillonite content was 5%. The specific plastic work decreased gradually with the increase of the montmorillonite content.The ability of resisting cracks extension was improved at the cost of the decrease of plastic property for nano-particles. With the increase of the montmorillonite content, the flexural strength and flexural modulus increased gradually while the tensile strength and breaking elongation ration increased at first then decreased and up to the max when the montmorillonite content was 5%.It was obtained from the analysis of rheological curve for nylon 11/POE-g-MAH/ montmorillonite nanocomposites with different montmorillonite content and POE-g-MAH content:the nylon 11/POE-g-MAH/montmorillonite nanocomposites with different mont-morillonite content and POE-g-MAH content were all pseudo-plastic fluids. As to the nylon 11/POE-g-MAH nanocomposites with 20% POE-g-MAH, the apparent viscosity decreased and viscous activation energy increased with the adding of montmorillonite. As to the nylon 11/montmorillonite nanocomposites with 5% montmorillonite, with the adding of POE-g-MAH, the apparent viscosity for nanocomposites decreased at first when the POE-g-MAH content was 25%, apparent viscosity increased while the viscous activation energy decreased.The crystallinity degree of nanocomposites decreased with the adding of POE-g-MAH while the crystallinity degree of nanocomposites increased with the adding of montmorillonite which played the role of heterophase nucleating agent. The crystal form of nylon 11/montmor-illonite nanocomposites had not changed with the adding of POE-g-MAH. However, crystal form of nylon 11/POE-g-MAH transferred fromγtoαwith the adding of montmorillonite.The effect of blending order on impact strength, tensile strength and flexural strength was very small. However, the specific essential work of fracture for Nlwas less than N2's while specific plastic work for Nlwas larger than N2's and crystallization temperature for N1 was a little higher than N2's. The crystallization time for N1 was less which was benefit for crystallization.3. The effect law of POE-g-MAH content as well as the grafting ratio of POE-g-MAH on mechanical property, rheological property, crystallization property of nylon 11/POE-g-MAH/ montmorillonite nanocomposites were studied systematically. The study results showed:With the increase of POE-g-MAH content in the POE-g-MAH/POE nanocomposites, the impact strength of nanocomposites increased at first and up to the max of 64.5 KJ/m2 which was 9.7 times as much as the pure nylon's when the POE-g-MAH content was 20% as well as the grafting ratio of MAH was 0.16. With the increase of POE-g-MAH content, the change of specific essential work of fracture was very small. However, with the increase of montmorillo-nite content, the specific plastic work increased at first then decreased and up to the max when the POE-g-MAH content was 20%. With the increase of POE-g-MAH content, tensile strength and breaking elongation ration of nanocomposites increased at first then decreased and the tensile strength was up to the max when the POE-g-MAH content was 20% while breaking elongation ration was up to the max when the POE-g-MAH content was 30%. However, the effect of POE-g-MAH content on the flexural strength and flexural modulus of nanocompo-sites was very small.It was obtained from the analysis of rheological curve for nylon 11/POE-g-MAH/mont-morillonite nanocomposites with different POE-g-MAH content:the nylon 11/POE-g-MAH/ montmorillonite nanocomposites with different POE-g-MAH content were all pseudo-plastic fluids. The apparent viscosity nanocomposites was up to the max when every part of the elastomer was POE-g-MAH and the viscous activation energy of nanocomposites change to be minimum when the POE-g-MAH content was 10% in the elastomer.The crystallinity degree decreased and the crystallization temperature increased with the increase of the POE-g-MAH content in the POE-g-MAH/POE nanocomposites.4. The effect of POE-g-MAH content,montmorillonite content,POE-g-MAH content in the elastomer and blending order on the diameter of elastomer was studied. The toughening mechanism of nylon 11/POE-g-MAH/montmorillonite (5%) ternary nanocomposites was dis-cussed according to the SEM image for impact fracture surface of nanocomposites.With the increase of POE-g-MAH content, the diameter distribution of elastomer in the nylon 11/POE-g-MAH/montmorillonite nanocomposites changed to be narrow and the diameter changed to be large. The critical layer thickness of brittle-tough transition for nano-composites was 0.16μm.With the increase of POE-g-MAH content in POE-g-MAH/POE nanocomposites, the diameter of elastomer was smaller from 1.16μm with the ratio for POE-g-MAH/POE of 10/90 to 0.24μm with all the parts were POE-g-MAH. As to the nylon 11/POE-g-MAH/montmorillo-nite or nylon 11/POE-g-MAH/POE/montmorillonite nanocomposites, the lower limit for elastomer diameter was 0.22μm if the material with good toughness strength was wanted.The effect of adding montmorillonite on the diameter distribution and particle shape of elastomer was small. With the increase of montmorillonite content, the diameter of elastomer particle decreased at first and with a minimum when the montmorillonite content was 5%. With the further increase of montmorillonite content, the diameter of elastomer showed a little increase but the range was very narrow.The toughening mechanism for nylon 11/POE-g-MAH/montmorillonite (5%) ternary nanocomposites was:when the elastomer particle space was larger than 0.16μm, the montmor-illonite layer played the role of stress concentration and the cavitation happened at first. When the elastomer particle space was less than 0.16μm, the POE-g-MAH played the role of stress concentration and the exfoliation with the matrix happened at first and then cavitation generated. When the elastomer particle diameter was less than 0.61μm, the elastomer particle can only cause matrix yielding and deformation within the range of several hundreds ofμm. While the elastomer particle diameter was more than 0.61μm, the elastomer particle can cause matrix yielding and deformation within the range of several hundreds ofμm as well as within the range of several tens ofμm. Thus, the energy was absorbed much more and the impact strength was greatly improved.