WO2015093884A1 - Multilayered composite material using nanofibrilated cellulose and thermoplastic matrix polymer - Google Patents

Abstract

The present invention relates to a multilayered composite material prepared by thermocompressing a multilayered sheet, comprising: a first sheet layer formed from a solution containing a nanofibrilated cellulose and a first thermoplastic matrix polymer; and a second sheet layer formed from a solution containing a second thermoplastic matrix polymer, wherein the mulilayered composite material of the present invention has a high strength and high elastic modulus.

Description

Multi-layered Composite Using Nanofibrillated Cellulose and Thermoplastic Matrix Polymer

The present invention relates to a multilayer composite material using nanofibrillated cellulose and a thermoplastic matrix polymer, and a method of manufacturing the same.

Technology using nano materials has been applied to various industrial fields, and it is known that the application of these nano technologies to general purpose polymers can improve physical, chemical and thermal properties.

In particular, nanocomposites reinforced with nano-sized raw materials exhibit excellent physical properties compared to conventional composites (RA Vaia, Polymer Nanocomposites Open a New Dimension for Plastics and Composites, The AMPTIAC Newsletter, 2002, 6, 17-24), Increasing strength or simultaneously increasing strength and modulus have been reported (MMO Seydibeyoglu et al., Composites Science and Technology, 2008, 68, 908-914). This increase in strength is known to be caused by a defect between the increased specific surface area and the reduced interface compared to composites reinforced with micro-sized raw materials (M. Sternitzke et al., Journal of the American Ceramic Society, 1998). , 81, 41-48).

On the other hand, cellulose is the most abundant natural polymer among the organic compounds present in nature, and can be obtained from renewable materials. Unlike petroleum-based polymers, which are used in the past, they are decomposed in soil during disposal. Biodegradable properties. Recently, as the environmental problems are seriously raised, the necessity of eco-friendly polymer materials has increased. Accordingly, active development of raw materials and products of cellulose to replace petroleum-based functional polymers has been actively conducted (G. Siqueira et al., Polymer, 2010, 2, 728-765).

In particular, the nanostructured fibrillated cellulose has a high modulus of 150-200 GPa and a high strength of 5 GPa as a reinforcing material of the composite material. It is superior to the physical properties of Kevlar fiber, one of the superfibers, and is nano-sized (10 to 100 nm thick) compared to ordinary carbon fiber and glass fiber, and has a small coefficient of thermal expansion (0.1 ppm K ^-1 ). Possible, light weight, low energy consumption, good processability. Therefore, if the fiber's diameter (nano size) and fiber's aspect ratio (L / D) are controlled through excellent properties such as high crystallinity, toughness, and elastic modulus of cellulose nanofibers and appropriate manufacturing processes, glass fiber is a key material of the composite material industry. It can be a very likely material to replace.

Composites made of 100% cellulose nanofibers having this advantage have been reported to have better physical properties than ordinary steel or magnesium alloys. However, since the composite material is composed of only 100% cellulose, it is known that a long time drying and compression process is required due to the characteristics of the manufacturing process, and that the composite material can be manufactured only in the form of sheet. In addition, this material has a drawback that it cannot be molded to have various forms due to the absence of thermoplastics (Marielle Henriksson et al., 2008; Istva´n Siro et al., 2010).

Therefore, the thermoplastic and thermosetting plastic composites reinforced with cellulose nanofibers have been identified as a new generation of high-performance, environmentally friendly materials that exceed the limits of existing glass fiber reinforced composites. As the development of modern industry demands to reduce the weight and strength of the product, cellulose nanofiber composites having high performance and high performance are used in the fields of industrial materials such as electrical and electronics, transportation equipment (automotive, aerospace, ships, etc.), civil engineering, architecture, and environment. It is possible to expand the application of core materials to special fields such as defense and medical prosthetics.

In addition, in the 21st century, research and development on green nanocomposites in which nanotechnology is fused to the composite material field is continuously being pursued as a way to solve environmental problems, energy and resource problems. Cellulose nanofiber composites will go beyond the limitations of existing materials, and as a next-generation sustainable new material, it will be very likely to become a high-performance composite material with eco-friendliness and economy. The green composite with various and excellent properties ultimately provides a source technology for obtaining advanced materials having high strength, high modulus mechanical performance and multi-functionality such as electrical, thermal conductivity, and low coefficient of thermal expansion, which are not obtained with conventional materials. to provide.

However, research and development on thermoplastic composites using cellulose nanofibers is still in its infancy.

Accordingly, the present inventors have completed the invention related to the multilayered composite material using nanofibrillated cellulose and thermoplastic matrix polymers having physical properties of glass fibers or more.

The present invention is to provide a multi-layer composite material using a nanofibrillated cellulose (NC) and a thermoplastic matrix polymer, which can replace the glass fiber reinforced composite material.

A first aspect of the present invention provides a semiconductor device comprising: a first sheet layer formed from a solution containing nanofibrillated cellulose and a first thermoplastic matrix polymer; And

By thermally compressing a multilayer sheet including a second sheet layer formed from a second thermoplastic matrix polymer-containing solution, the first thermoplastic matrix polymer and the second thermoplastic matrix polymer are thermally melted with each other, and nanofibers are formed between the thermally melted polymers. It provides a composite material in which the berylated cellulose is inserted.

A second aspect of the present invention is directed to a method for manufacturing a semiconductor device comprising: at least one first sheet layer prepared by drying and pressing a nanofibrillated cellulose and a first thermoplastic matrix polymer-containing solution; And a first step of preparing a multilayer composite material in which at least one of the second sheet layers containing the second thermoplastic matrix polymer is laminated. And

Applying a pressure to thermally melt the first thermoplastic matrix polymer and the second thermoplastic matrix polymer below the brittleness temperature of the nanofibrillated cellulose,

The at least one first sheet layer and the second sheet layer are laminated alternately, to provide a method of manufacturing a multilayer composite material.

A third aspect of the present invention provides a reinforced molding to which the multilayered composite material of the first aspect is applied.

Hereinafter, the present invention will be described in more detail.

The term "multilayer composite material" as used herein means a material in which a plurality of layers having different components are laminated. Specifically, in the present invention, one or more first and second sheet layers may be alternately stacked.

The thermoplastic matrix polymer of the present invention may be used as long as it is a material having excellent compatibility such as nanofibrillated cellulose and interfacial affinity as a thermoplastic polymer, and is preferably a polyamide (PA) resin. The polyamide resin is a synthetic polymer in which the structural units constituting the main chain are connected by an amide group, and specific examples thereof include Polyamide 6 and Polyamide 6,6. The first thermoplastic matrix polymer and the second thermoplastic matrix polymer of the present invention may be the same or different.

The fiber length of the polyamide resin is preferably 0.1 mm to 3.0 mm. When the fiber length is longer than 3.0 mm, the long fiber length causes difficulty in dispersion when mixed with water, and when the fiber length is shorter than 0.1 mm, the shape stability of the manufactured sheet is insufficient. Fineness is preferably 0.1 to 5.0 denier.

The nanofibrillated cellulose of the present invention may have a diameter of 10 to 100 nm.

The second sheet layer formed from the second thermoplastic matrix polymer of the present invention may be a hot melt web, a meltblown nonwoven or a film, and morphological analysis suggests a meltblown nonwoven.

In the step of producing a multilayer sheet by thermal pressing the second sheet layer on the first sheet layer of the present invention, the conditions of the thermal pressing is 100 ~ 200 ℃ when the second sheet layer is a hot melt web, when the melt-blown nonwoven fabric or film It may be 170 ~ 270 ℃.

In addition, the thermocompression may be performed in a pressure range of 4 to 100MPa.

Through the thermal compression, the first thermoplastic matrix polymer of the first sheet layer and the second thermoplastic matrix polymer of the second sheet layer are thermally melted with each other, and nanofibrillated cellulose is inserted between the thermally melted polymers. As a result, the bonding force between the sheet layers is increased and the tensile strength is increased. If the temperature range is exceeded, the nanofibrillated cellulose fibers are also embrittled and the fiber structure is destroyed. Thus, the thermocompression temperature range is a temperature at which the thermoplastic matrix polymer can be selectively melted and at the same time nanofibrillated. Preference is given to a range below the brittleness temperature at which cellulose does not embrittle.

When the second sheet layer formed from the solution containing the second thermoplastic matrix polymer is laminated on the first sheet layer formed from the solution containing the nanofibrillated cellulose and the first thermoplastic matrix polymer and thermally compressed, the second thermoplastic matrix polymer is heated. It is melted by compression to fill the pores inside the first sheet layer, and serves to connect the internal fibers with each other.

Compared to sheets formed only of microfibrillated cellulose, the reinforcement effect due to nanofibrillated cellulose embedded in the sheet containing the thermoplastic matrix polymer constitutes a mesh network connected by hydrogen bonding or entanglement. Interactions between nano-sized configurations are more effective and allow for better dispersion in the matrix.

The multilayer composite material of the present invention may have a tensile strength of 20 to 80 MPa. This is because the multilayer composite material prepared by thermocompressing the first sheet layer containing only the nanofibrillated cellulose without the thermoplastic matrix polymer and the second sheet layer formed from the solution containing the thermoplastic matrix polymer (see FIG. 1B) is weak. Compared to having 8 ~ 10 MPa tensile strength, it is very excellent in strength.

In the present invention, the first sheet layer is formed from a solution containing nanofibrillated cellulose and a first thermoplastic matrix polymer. First, pulp is dispersed in a solvent, subjected to mechanical beating, and a nanofibrillated cellulose suspension is prepared using a homogenizer. Next, the thermoplastic matrix polymer is mixed with the nanofibrillated cellulose suspension to form a sheet-shaped composite material through a wet web formation and a drying process.

The pulp, which is a raw material used to prepare the nanofibrillated cellulose of the present invention, may be soda pulp (AP), semichemical pulp, kraft pulp, and the like, and particularly, but is not limited to bleached sulfurous pulp. .

In addition, as a solvent for dispersing cellulose, water is preferable, but is not limited thereto. Since the cellulose nanofibers are hydrophilic, there is a problem that can not be evenly dispersed when using a hydrophobic solvent.

The nanofibrillated cellulose and the first thermoplastic matrix polymer are preferably 3: 7 to 5: 5 by solid weight ratio. When the weight ratio is smaller than 3: 7 (eg 2: 8), the particles may be separated and layered with the solvent (water) by the density difference between the nanofibrillated cellulose and the first thermoplastic matrix polymer after dispersion. When the weight ratio is greater than 5: 5 (eg 6: 4), drainage may not be good and curling of the sheet may occur severely during drying. This is because the solvent (water) molecules remaining between the nanofibrillated cellulose serve as an adhesive for connecting the fibers to form a hydrogen bonding network. In one embodiment, the nanofibrillated cellulose and the first thermoplastic matrix polymer are about 4: 6 by weight of solids.

The wet web forming and drying process is a process of selectively removing the solvent from the mixture of the nanofibrillated cellulose suspension and the thermoplastic matrix polymer to obtain a uniform sheet-like fibrous structure, and then manufacturing the sheet into a sheet by pressing rolls.

The wet web formation is a process of preventing curling and increasing density of the manufactured sheet by applying a pressure at a high temperature before drying the manufactured sheet. The pressurization may be performed using a hot press, but is not limited thereto. Through the pressing step, the volume of voids between the nanofibrillated cellulose and the thermoplastic matrix polymer fiber generated during the wet nonwoven process is reduced, and the interface wettability is improved. At this time, the higher the temperature and pressure of the pressing step is preferable.

In addition, the drying in the drying step is preferably such that the moisture content of the sheet is less than 1%. The drying is preferably performed at 0.5 to 30 hours at 30 to 100 ℃ under atmospheric pressure. In one embodiment the drying is carried out at 80 ° C. for 24 hours under atmospheric pressure. The drying temperature and time affect the moisture content of the final sheet, and at high temperatures of 100 ° C. or higher, the sheet may be warped due to rapid drying or have an undesirable effect on the physical properties.

In order to impart a bonding force to the sheet formed through the wet web forming and drying process, a temperature of 150 ° C. to 250 ° C. and a pressure of 2 MPa to 300 MPa may be further added. In one embodiment, a pressure of 4.8 MPa is further applied at 210 ° C. Due to the temperature and pressure, the thermoplastic matrix polymer fibers are melted and impregnated, and the impregnated thermoplastic matrix polymer fibers together with the nanofibrillated cellulose fibers form a nanofiber composite. Representative processes of high temperature and high pressure molding to apply the temperature and pressure include, but are not limited to, a calender process and a press process.

The multi-layered composite material formed of the nanofibrillated cellulose of the present invention can be used as an environmentally friendly, next-generation high-performance new material that can replace the existing glass fiber reinforced composite material and can be manufactured as a reinforced molded article. In other words, multi-layered composite materials with high performance and high performance are used in the fields of industrial materials such as electrical and electronic equipment, transportation equipment (automobiles, aerospace, ships, etc.), civil engineering, construction, and environment, and defense and medical industries that require lightweight and high strength products. It is possible to expand the application of core materials to special fields such as prosthetics.

The multi-layered composite material of the present invention is characterized in that a first sheet layer composed of nanofibrillated cellulose and a first thermoplastic matrix polymer is thermally compressed with a second sheet layer formed from a solution containing a second thermoplastic matrix polymer, thereby forming a first thermoplastic matrix polymer. The second thermoplastic matrix polymer may be thermally melted with each other, and nanofibrillated cellulose may be inserted between the thermally melted polymers. Therefore, the multilayer composite material of the present invention has a high density, shows excellent tensile modulus, flexural modulus, and fracture characteristics, and has an effect of superior strength than conventional glass fibers.

In addition, since the first thermoplastic matrix polymer of the first sheet layer and the second thermoplastic matrix polymer of the second sheet layer are thermally melted with each other, the interlayer bonding force is excellent and may serve as an adhesive layer.

1A and 1B illustrate a multilayer composite material formed by laminating or thermocompressing a sheet composed of nanofibrillated cellulose and a meltblown nonwoven fabric, which is an adhesive layer, by a conventional method, and FIG. 1C illustrates an embodiment of the present invention. The schematic diagram shows a multilayered composite material formed by thermocompression bonding of an NC / first thermoplastic matrix polymer and a second thermoplastic matrix polymer as an adhesive layer.

Figure 2 shows a process chart for manufacturing a multi-layer composite material in the form of a sheet through a wet web forming and drying process using a nanofibrillated cellulose and a thermoplastic matrix polymer.

FIG. 3 illustrates the structure of a multilayer composite composed of an NC / PA composite and an adhesive layer (hot melt web, meltblown nonwoven and film) in accordance with one embodiment of the present invention.

Figure 4 shows the observation surface and cross section of the NC / PA multilayer composite material of Example 2 by scanning electron microscopy.

5 is a graph showing the tensile modulus of elasticity of the NC / PA composite material according to the adhesive layer, thermal compression pressure and NC content.

Figure 6 is a graph showing the flexural modulus of the NC / PA multilayer composite material according to the adhesive layer, thermal compression pressure and NC content.

7 is a graph showing fracture characteristics of PA6,6 sheet, NC / PA6 and NC / PA6,6 composite materials.

8 is a graph showing the tensile strength and tensile modulus of the NC / PA / NY and NC / PA / AB composite materials.

9 is a graph showing the flexural strength and flexural modulus of the NC / PA / NY and NC / PA / AB composite materials.

10 is a graph showing the impact characteristics of the NC / PA / NY and NC / PA / AB composite materials.

Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples. However, the following Examples and Experimental Examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Example 1 Preparation of Composites (NC / PA) Containing Nanofibrillated Cellulose and Thermoplastic Matrix Polymers

First, a pulp dispersion having a fiber length of 1.0 mm was dispersed in water and dissociated through a mechanical beating process for 30 minutes in a pulper to prepare a pulp dispersion. A pulp dispersion of 0.2% by weight was prepared based on the weight of the pulp solids contained in the pulp dispersion prepared above, stirred for 30 minutes, and then fibrillated using a homogenizer.

Three nozzles of different diameters were passed through the high pressure homogenizer sequentially in the order of diameter size as follows. 1) 5 times: nozzle diameter 250 mu m, pressure 70 MPa, 2) 5 times: nozzle diameter 200 mu m, pressure 240 MPa, 3) 5 times: nozzle diameter 150 mu m, pressure 310 MPa. As described above, the cellulose dispersion was passed five times for each nozzle to prepare a nano-sized fibrillated cellulose (nanofibrillated cellulose, NC) suspension through a total of 15 homogenizing processes.

The NC suspension and two kinds of polyamide (Polyamide, PA) fibers (PA6 or PA6,6) were mixed in a solid weight ratio of about 4: 6, and the wet web was formed and dried in the order shown in FIG. 2. NC / PA composites in sheet form were prepared. At this time, the fiber length of the used PA fiber was 1.0 mm, the fineness of the pressure of 3.4 MPa in hot plate press NC / PA6 sheet manufactured by a wet web forming process using a stainless steel screen mesh of 1,000 scales After drying for 2 hours at a temperature of 80 ℃ and dried in the oven at the same temperature for 24 hours. To impart bonding force to the dried NC / PA6 sheet, a roll calendar was used at a rate of 4.8 MPa at 210 ° C. and passed at a rate of 0.5 m / min.

Example 2 Preparation of Multilayer Composites Using Composite Materials (NC / PA) Containing Nanofibrillated Cellulose and Thermoplastic Matrix Polymers

In order to manufacture a multi-layered composite material, as shown in FIG. 3, a PA6 hot melt web, a meltblown nonwoven fabric or a film is laminated in a 1 to 5 layer structure between the NC / PA6 sheet layers prepared in Example 1, as shown in FIG. By thermal compression. The weights of the PA6 hot melt webs, meltblown nonwovens and films used at this time were 17, 100 and 175 g / m ² . Table 1 shows the materials, thermocompression conditions, NC content, and sample names of the NC / PA multilayer composite material prepared in 1 to 5 layers. Scanning Electron Microscope (SEM) (SU8000, Hitachi, Japan) was used to analyze the surface and cross section of the NC / PA multilayer composite material.

Table 1

Matrix or adhesive layer	Thermocompression conditions	Floor	NC content (wt.%)	Total thickness (㎛)	Sample name
-	-	One	40.0	40	N1
PA Hot Melt Web	150 ° C / 60 seconds	2	38.0	160	L2
		3	37.4	280	L3
		4	37.1	400	L4
		5	37.0	490	L5
PA Meltblown Nonwovens	210 ~ 230 ℃ / 60 seconds	2	34.7	260	M2
		3	33.3	420	M3
		4	32.6	620	M4
		5	32.2	830	M5
PA film	210 ~ 230 ℃ / 120 seconds	2	38.0	170	F2
		3	37.4	290	F3
		4	37.1	400	F4
		5	37.0	540	F5
-	240 ° C / 1,200s (87MPa) after 190 ° C / 600s warm up	3	40.0	100	S3

Experimental Example 1: Physical Properties of NC / PA Composites and Multilayer Composites Using the Same

(1) Tensile modulus

Tensile modulus of the composite material was evaluated using a universal strength tester (H100KS, Tinius Olsen, UK) in accordance with ASTM D638-03, a speed of 1.0mm / min and a load cell of 2.5kN was used.

Figure 5 shows the tensile modulus of the NC / PA composite material according to the adhesive layer and thermal compression pressure and NC content. That is, the NC / PA6 and NC / PA6,6 composite material prepared by the method of Example 1, which was prepared using PA6 or PA6,6 as polyamide fibers, and a second thermoplastic mattress polymer layer (adhesive layer or second sheet layer) Tensile modulus of the multilayer composite material of Example 2 prepared using PA hot melt web (L), PA melt blown nonwoven fabric (M) or PA film (F) was measured. In FIG. 5, the NC / PA6,6-S composite material is manufactured by thermally compressing three NC / PC6,6 sheets without using a mattress as in Example 2.

The tensile modulus of the NC / PA6 and NC / PA6,6 composites was in the range of 1 to 2 MPa and 3 to 12 MPa, depending on the NC content, whereas the tensile modulus of the PA6,6 sheet was 0.8 MPa. Tensile tensile modulus of NC / PA6,6 multilayer composites was higher than that of NC / PA6 composites. Tensile modulus of NC / PA composites increased with increasing NC content. In addition, it was confirmed that the multilayer composite material having a high tensile modulus was produced when the thermocompression was performed at a pressure of 87MPa compared to the NC / PA multilayer composite material thermally compressed at a pressure of 4.8MPa.

(2) Flexural modulus

The flexural modulus of the composite material was evaluated under the same conditions as the tensile modulus by the evaluation method of ASTM D790-03.

Figure 6 shows the flexural modulus of the NC / PA multilayer composite material according to the adhesive layer and thermal compression pressure and NC content. The flexural modulus of the composite material thermally compressed at 87MPa was higher than that of the adhesive layer, and the flexural modulus of the sample using PA meltblown nonwoven fabric as the adhesive layer was higher than that of the PA hot melt web and PA film. Similar to the sample used. When the same NC content and thermocompression pressure were applied, the samples using the PA film as the adhesive layer of the NC / PA multilayer composite showed higher flexural modulus than the samples using the PA hot melt web. The flexural modulus of NC / PA6,6 multilayer composites was higher than that of NC / PA6 multilayer composites regardless of the type of adhesive layer.

(3) breaking characteristics

The fracture characteristics of NC / PA composites were evaluated using an electrodynamic test system (Acumen 1, MTS system, USA) in accordance with ASTM D671-71. The load cell used was 3 kN and 10 ⁶ cycles at a frequency of 20 Hz. cycle).

7 shows the fracture characteristics of PA6,6 sheets, NC / PA6 and NC / PA6,6 composites. As a result of performing 10 ⁶ repetition experiments at 20Hz using a 3kN load cell, the break stress reduction of NC / PA6,6 composite material was less than that of NC / PA6 composite material and PA6,6 sheet. Confirmed. This results in an increase in the service life of the NC / PA composite material due to the NC reinforcing effect. In addition, the initial stress at break of NC / PA composites was higher than that of PA6,6 sheet due to NC reinforcement effect.

Therefore, it was confirmed that NC / PA composite material with increased tensile modulus, flexural modulus, and service life could be manufactured by using NC as a reinforcing material in PA.

Experimental Example 2: Physical Properties of Multi-layered Composites Using NC / PA Composites and Thermoplastic Panels

The method of manufacturing NC and the method of manufacturing NC / PA sheet using a high pressure homogenizer are the same as those shown in Example 1, and were prepared by the manufacturing method of FIG. The prepared NC / PA sheet was adhered to a polyamide (PA) panel (sample name: NY) and an acrylonitrile butadiene styrene (ABS) panel (sample name: AB), respectively, to NC / PA / NY and NC / PA / AB composites were prepared. PA6 hot-melt web (sample name: L, 17 g / m) as adhesive layer for thermocompression bonding between NC / PA sheet and NY or NC / PA sheet and AB to produce NC / PA / NY and NC / PA / AB composites ² ), a meltblown nonwoven fabric (sample name: M, 100 g / m ² ) and a film (sample name: F, 175 g / m ² ) were used.

The manufactured NC / PA / NY and NC / PA / AB composite materials, and the independent NY panel (sample name: NY-N) and AB panel (sample name: AB-N), which did not adhere the NC / PA sheet, and the adhesive layer, were Tensile, flexural, fracture, and impact characteristics of the samples (sample name: S) thermo-compressed without using the NC / PA sheet itself were compared.

In the production of the multilayered composite material, thermal compression between the composite material and the adhesive layer was performed at 210 ° C./40 sec for sample names NY-S, NY-F, and NY-M, and 130 ° C. for sample names NY-L and AB-L. It was performed at 60 second condition.

(1) Tensile strength and tensile modulus

Tensile properties of NC / PA / NY and NC / PA / AB composites were evaluated using a universal strength tester (H100KS, Tinius Olsen, UK) according to ASTM D638-03, with a speed of 1.0 mm / min and 50 kN. The load cell of was used.

Figure 8 shows the tensile strength and tensile modulus of the NC / PA / NY and NC / PA / AB composite materials. Tensile strength and tensile modulus were increased by bonding NC / PA sheets to NY or AB panels. Tensile strength and tensile modulus of NC / PA / NY composites increased up to 158% and 126%, respectively, compared to NY panels. In addition, tensile strength of NC / PA / AB composites increased by 130% and 126%, respectively, compared to AB panels. In particular, it was confirmed that the tensile modulus of the NY panel thermocompression-bonded using the PA hot melt web as the adhesive layer was significantly increased compared to the tensile modulus of the composite material bonded with the PA film or PA melt blown nonwoven fabric.

(2) flexural strength and flexural modulus

The flexural modulus of the prepared composite material was evaluated under the same conditions as the tensile modulus by the evaluation method of ASTM D790-03.

Figure 9 shows the flexural strength and flexural modulus of the NC / PA / NY and NC / PA / AB composite materials. Flexural strength and flexural modulus were increased by adhering NC / PA sheets to PA and AB panels. In particular, flexural strength and flexural modulus of NC / PA / AB composites were increased by 292% and 160%, respectively.

(3) breaking characteristics

The fracture characteristics of the NC / PA / NY and NC / PA / AB composites were evaluated using an electrodynamic test system (Acumen 1, MTS system, USA) according to ASTM D671-71, where the load cell was 3 kN. Tests were made for 10 ⁶ cycles at a frequency of 10 Hz.

Table 2 below shows the fracture characteristics of the NC / PA / NY and NC / PA / AB composite materials. The 10 ⁶ cycles were tested at 70, 50, and 30% of the maximum flexural load.The 70% force resulted in the greatest breaking cycle of the AB-L sample with NC / PA / AB bonded to PA hot melt film. At 50% force, the maximum breaking cycle was greatest in the NY-F sample with NC / PA / NY bonded with PA film. In addition, at 30% force all samples passed the 10 ⁶ cycle test. In the NY and AB panels to which the NC / PA sheet was bonded, the number of breaking cycles increased significantly regardless of the type of the adhesive layer.

TABLE 2

(4) impact characteristics

The impact properties of the manufactured composite materials were tested by dropping a ball with a diameter of 50 mm at a height of 1,520 mm by a steel ball drop test machine using the Gardner impact test method (falling weight) according to ASTM D 5420. .

Figure 10 shows the impact characteristics of the NC / PA / NY and NC / PA / AB composite materials. NY panels showed better shock absorption characteristics than AB panels, and the impact absorption characteristics were improved by adhesion of NC / PA sheets.

Therefore, it was confirmed that tensile, flexural, fracture, and impact characteristics were improved by adhering NC / PA sheets to NY and AB panels.

Claims (11)

1. A first sheet layer formed from a solution containing nanofibrillated cellulose and a first thermoplastic matrix polymer; And

   By thermally compressing a multilayer sheet including a second sheet layer formed from a second thermoplastic matrix polymer-containing solution, the first thermoplastic matrix polymer and the second thermoplastic matrix polymer are thermally melted with each other, and nanofibers are formed between the thermally melted polymers. Multilayer composite material characterized by the insertion of a beryl cellulose.
2. The method of claim 1,

   Wherein the first thermoplastic matrix polymer and the second thermoplastic matrix polymer are polyamide resins.
3. The method of claim 2,

   The polyamide resin is Polyamide 6 or Polyamide 6,6, multilayer composite material.
4. The method of claim 1,

   The first sheet layer is prepared by mixing a suspension of nanofibrillated cellulose and the first thermoplastic matrix polymer in a solid weight ratio of 3: 7 to 5: 5.
5. The method of claim 1,

   And the second sheet layer is a hot melt web, meltblown nonwoven or film.
6. The method of claim 5,

   The thermal pressing is performed at 100 to 200 ° C. when the second sheet layer is a hot melt web, and 170 to 270 ° C. when a meltblown nonwoven or film.
7. The method of claim 1,

   The thermal compression is to be carried out in a pressure range of 4 to 100MPa, multilayer composite material.
8. The method of claim 1,

   Wherein said multilayer composite material has a tensile strength of 20 to 80 MPa.
9. At least one first sheet layer prepared by drying and pressing nanofibrillated cellulose and a first thermoplastic matrix polymer-containing solution; And a first step of preparing a multilayer composite material in which at least one of the second sheet layers containing the second thermoplastic matrix polymer is laminated. And

   Applying a pressure to thermally melt the first thermoplastic matrix polymer and the second thermoplastic matrix polymer below the brittleness temperature of the nanofibrillated cellulose,

   Wherein said at least one first sheet layer and said second sheet layer are laminated alternately.
10. The method of claim 9,

    Wherein the first thermoplastic matrix polymer and the second thermoplastic matrix polymer are the same or different polyamide resins.
11. The reinforced molded article to which the multilayered composite material according to any one of claims 1 to 8 is applied.

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