Polymer Composite

Abstract

The present disclosure relates to a polymer composite. According to the present disclosure, there is provided a polymer composite capable of exhibiting improved light resistance while being environmentally friendly by containing microcellulose fibers fibrillated by the growth of inorganic particles as a reinforcing material.

Claims

1. A polymer composite containing a polymer matrix; microcellulose fibers; and a compatibilizer, and satisfying Equation 1:
2≤ΔE*.sup.ab≤15   [Equation 1] in the Equation 1, ΔE*.sub.ab is a color difference of the polymer composite, and the color difference is obtained according to the following formula of [(L*.sub.t−L*.sub.0).sup.2+(a*.sub.t−a*.sub.0).sup.2+(b*.sub.t−b*.sub.0).sub.2].sup.1/2 in L*a*b* color space measured using a colorimeter, wherein L*o, a*o and b*o are initial chromaticity values of the polymer composite, and L*.sub.t, a*.sub.t and b*.sub.t are chromaticity values of the polymer composite after exposing the polymer composite to a light source (fluorescent UV lamp) for 480 hours under the conditions of 0.75 W/(m.sup.2˜nm) @ 340 nm and 45±1 ° C.

2. The polymer composite of claim 1, wherein the microcellulose fibers comprise nanofibrils and inorganic particles.

3. The polymer composite of claim 2, wherein the nanofibrils are bonded to a surface of the microcellulose fibers, and the inorganic particles are bonded to the nanofibrils or bonded to a surface or inside of the microcellulose fibers.

4. The polymer composite of claim 2, wherein the microcellulose fibers have a minor axis diameter of 1 μm to 30 μm, and the nanofibrils have a minor axis diameter of 10 nm to 400 nm.

5. The polymer composite of claim 2, wherein the inorganic particles comprise spherical particles having a diameter of 0.01 μm to 10 μm; columnar particles having a diameter of 0.01 μm to 10 μm on one axis and a diameter of 0.02 μm to 30 μm on another axis; or a mixture thereof.

6. The polymer composite of claim 2, wherein the inorganic particles comprise at least one element selected from the group consisting of copper, zinc, calcium, aluminum, iron, silver, platinum, palladium, ruthenium, iridium, rhodium, osmium, chromium, cobalt, nickel, manganese, vanadium, molybdenum, magnesium, strontium, titanium, zirconium, hafnium, and gallium.

7. The polymer composite of claim 2, wherein the inorganic particles are contained in an amount of 1 to 40 parts by weight based on 100 parts by weight of the microcellulose fibers.

8. The polymer composite of claim 1, wherein the polymer composite contains 30 to 90 wt % of the polymer matrix; 5 to 60 wt % of the microcellulose fibers; and 1 to 20 wt % of the compatibilizer.

9. The polymer composite of claim 1, wherein the polymer matrix is at least one polymer selected from the group consisting of polyolefin, polyamide, styrenic polymer, and polycarbonate.

10. The polymer composite of claim 1, wherein the compatibilizer comprises a modified polyolefin.

11. The polymer composite of claim 1, wherein a tensile strength measured according to ASTM D638-5 for an ASTM D638-5 standard specimen prepared from the polymer composite is 35 MPa to 65 MPa.

12. The polymer composite of claim 1, wherein a flexural strength measured according to ISO 178 for a specimen having a size of 80 mm×10 mm×4 mm prepared from the polymer composite is 50 MPa to 85 MPa.

13. The polymer composite of claim 1, wherein a flexural modulus measured according to ISO 178 for a specimen having a size of 80 mm×10 mm×4 mm prepared from the polymer composite is 1.0 GPa to 3.5 GPa.

14. The polymer composite of claim 1, wherein the microcellulose fibers and the compatibilizer are dispersed in the polymer matrix.

15. The polymer composite of claim 10, Wherein the modified polyolefin is a resin obtained by modifying a polyolefin with an unsaturated carboxylic acid or a derivative thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0091] FIG. 1A shows an enlarged schematic view of non-fibrillated microcellulose fibers and FIG. 1B shows an enlarged schematic view of microcellulose fibers including nanofibrils and inorganic particles.

[0092] FIG. 2, and FIGS. 4A and 4B are scanning electron microscope (SEM) images of cellulose fibers fibrillated by the growth of inorganic particles according to Preparation Example 1 below.

[0093] FIG. 3 is a SEM image of cellulose fibers fibrillated by the growth of inorganic particles according to Preparation Example 4 below.

[0094] FIG. 5A shows a SEM image of miniaturized cellulose fibers complexed with inorganic particles according to Preparation Example 5 below, and FIG. 5B shows a SEM image of a SEM image of FIG. 5A taken at a higher magnification.

[0095] FIG. 6 shows specifications of a dog-bone-shaped specimen (or a dumbbell-shaped specimen) for measuring tensile strength according to Type V of ASTM D638 (unit: mm).

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0096] Hereinafter, the function and effect of the present invention will be described in more detail through specific examples. However, these examples are for illustrative purposes only, and the invention is not intended to be limited by these examples.

Preparation Example 1

[0097] (Preparation of Fibrillated Cellulose Fibers)

[0098] Hardwood kraft fibers (average fiber length: 0.692 mm, average minor axis diameter: 15.8 μm) were prepared as cellulose raw materials. An aqueous solution in which 20 g of zinc acetate was dissolved in 1000 g of distilled water was prepared. 20 g of the fibers were added to the aqueous solution and stirred at 200 rpm for 1 hour to obtain a mixture.

[0099] 7.2 g of sodium hydroxide (NaOH) was added to the mixture as a reducing agent at 50 ° C., and heated to 95 ° C., followed by stirring at 200 rpm for 4 hours to grow inorganic particles on the fibers. The content of the inorganic particles was confirmed to be 8 parts by weight based on 100 parts by weight of the fibers.

[0100] As shown in FIG. 2, it was confirmed using a scanning electron microscope (SEM) that fibrillation occurred in the fiber portion on which inorganic particles (ZnO) were grown. As a result of analyzing the SEM image, it was confirmed that the inorganic particles had a uniform particle diameter of about 100 nm (see FIG. 2). In addition, it was confirmed that metal elements (zinc) and oxygen were evenly distributed on the fibrillated cellulose fibers by the growth of the inorganic particles (see FIGS. 4A and 4B).

Preparation Example 2

[0101] (Preparation of Fibrillated Cellulose Fibers)

[0102] Fibrillated cellulose fibers were prepared in the same manner as in Preparation Example 1, except that the content of zinc acetate was controlled such 2 that the content of the inorganic particles was 12.5 parts by weight based on 100 parts by weight of the fibers.

[0103] As a result of analyzing the SEM image, it was confirmed that the inorganic particles had a uniform particle diameter of about 100 nm.

Preparation Example 3

[0104] (Preparation of Fibrillated Cellulose Fibers)

[0105] Fibrillated cellulose fibers were prepared in the same manner as in Preparation Example 1, except that the content of zinc acetate was controlled such ii that the content of the inorganic particles was 25 parts by weight based on 100 parts by weight of the fibers.

[0106] As a result of analyzing the SEM image, it was confirmed that the inorganic particles had a uniform particle diameter of about 100 nm.

Preparation Example 4

(Preparation of Fibrillated Cellulose Fibers)

[0107] Fibrillated cellulose fibers were prepared in the same manner as in Preparation Example 1, except that calcium carbonate (CaCO.sub.3) was used instead of zinc acetate and the content of calcium carbonate was controlled such that the content of the inorganic particles was 45 parts by weight based on 100 parts by weight of the fibers.

[0108] As a result of analyzing the SEM image, it was confirmed that the inorganic particles having a particle diameter of 100 nm were aggregated to form non-uniform aggregates (˜1 μm) (see FIG. 3).

Preparation Example 5

(Preparation of Miniaturized Cellulose Fibers)

[0109] Hardwood kraft fibers were prepared as cellulose raw materials as in Preparation Example 1. A surface of the fibers was oxidized using 2,2,6,6-tetramethylpiperidinyl-1-oxyradical (TEMPO) as a catalyst to obtain oxidized pulp. 1 g of the oxidized pulp was dispersed in 99 g of distilled water and miniaturized (defibrated) with a mixer for 30 minutes to obtain an aqueous dispersion of miniaturized cellulose at a concentration of 1%.

[0110] A zinc acetate aqueous solution was prepared by dissolving 20 g of zinc acetate in 1000 g of distilled water. 3.6 g of sodium hydroxide (NaOH) was dissolved in 10 ml of distilled water to prepare a sodium hydroxide solution.

[0111] While stirring 100 g of the aqueous dispersion of miniaturized cellulose at 15° C., 50 ml of the zinc acetate aqueous solution and 10 ml of the sodium hydroxide solution were added thereto, followed by stirring at 500 rpm for 2 hours to prepare a composite of zinc oxide (ZnO) particles and miniaturized cellulose.

[0112] As shown in FIGS. 5A and 5B, it was confirmed using a scanning electron microscope that the composite of zinc oxide particles and miniaturized cellulose according to Preparation Example 5 had strong bonding strength and aggregation between the miniaturized celluloses, so that nanofibers were aggregated and the dispersion degree of particles was low.

Example 1

[0113] 30 wt % of fibrillated cellulose fibers according to Preparation Example 1, 60 20 wt % of homopolypropylene (melt flow rate (MFR) according to ASTM D1238: 60 g/10 min) and 10 wt % of a compatibilizer were added to a batch mixer, and mixed at 160 ° C. for 20 minutes to prepare a master batch in the form of pellets. As the compatibilizer, maleic anhydride-grafted polypropylene (acid number according to ASTMD-1386 (2010): 20 mg KOH/g) was used.

[0114] The master batch was put into a twin-screw extruder to perform a compounding process, and then extruded. The mixture obtained through the extrusion was put back into an injection machine and then injected, thereby obtaining a polymer composite specimen.

Example 2

[0115] A polymer composite specimen was obtained in the same manner as in Example 1, except that the fibrillated cellulose fibers according to Preparation Example 2 was used instead of Preparation Example 1.

Example 3

[0116] A polymer composite specimen was obtained in the same manner as in Example 1, except that the fibrillated cellulose fibers according to Preparation Example 3 was used instead of Preparation Example 1.

Example 4

[0117] A polymer composite specimen was obtained in the same manner as in Example 1, except that the fibrillated cellulose fibers according to Preparation Example 3 was used instead of Preparation Example 1, and a master batch was prepared by additionally adding and mixing 3 wt % of a black colorant (NB9096) based on the weight of the compounds added to the batch mixer.

Example 5

[0118] A polymer composite specimen was obtained in the same manner as in Example 1, except that 55 wt % of the fibrillated cellulose fibers according to Preparation Example 3, 35 wt % of polypropylene, and 10 wt % of a compatibilizer were added to the batch mixer.

Example 6

[0119] A polymer composite specimen was obtained in the same manner as in Example 1, except that 5 wt % of the fibrillated cellulose fibers according to Preparation Example 3, 85 wt % of polypropylene, and 10 wt % of a compatibilizer were added to the batch mixer.

Comparative Example 1

[0120] A polymer composite specimen was obtained in the same manner as in Example 1, except that the fibrillated cellulose fibers according to Preparation Example 4 was used instead of Preparation Example 1.

Comparative Example 2

[0121] A polymer composite specimen was obtained in the same manner as in Example 1, except the hardwood kraft fibers used in Preparation Example 1 which were soaked in water and swollen were applied instead of the fibrillated cellulose fibers according to Preparation Example 1.

Comparative Example 3

[0122] A polymer composite specimen was obtained in the same manner as in Example 1, except that the miniaturized cellulose fibers according to Preparation Example 5 was used instead of Preparation Example 1.

TEST EXAMPLES

[0123] The physical properties of the specimens prepared in Examples and Comparative Examples were evaluated by the following method, and the results are shown in Table 1 and Table 2 below.

[0124] (1) Minor Axis Diameter of Fiber

[0125] The minor axis diameter of the cellulose fibers (the shortest diameter in the cross section of fiber) prepared in Preparation Examples was measured using a scanning electron microscope.

[0126] Specifically, in the case of microcellulose fibers, the minor axis diameters of 10 microfibers per each sample were measured and displayed in a range excluding the maximum and minimum values. In the case of nanofibrils, the minor axis diameters of 20 nanofibrils per each sample were measured, and displayed in a range excluding the maximum and minimum values.

[0127] In Preparation Example 5, the cellulose fibers were miniaturized (defibrated), and then complexed with particles unlike Preparation Examples 1 to 4. The minor axis diameter of nanofibrils of Preparation Example 5 in Table 1 below means the minor axis diameter of the miniaturized cellulose after complexing with particles.

[0128] (2) Light Resistance

[0129] Using a weather resistance tester (model name: QUV ACCELERATED WEATHERING TESTER, manufacturer: Q-LAB), a specimen was exposed to a light source (fluorescent UV lamp) under the conditions of 0.75 W/(m.sup.2.Math.nm) @340 nm and 45±1° C. for 480 hours.

[0130] Chromaticity values of the specimen before and after exposure to the light were measured using a colorimeter (model name: Ci7860, manufacturer: X-rite). Using the measured chromaticity values of L*a*b*, the color difference (ΔE*.sub.ab) was obtained by the following formula of [(L*.sub.t−L*.sub.0).sup.2+(a*.sub.t-a*.sub.0).sup.2+(b*.sub.t-b*.sub.0).sup.2].sup.1/2

[0131] In the above formula, L*.sub.0, a*.sub.0 and b*.sub.0 are initial chromaticity values of the specimen before exposure to light; and L*.sub.t, a*.sub.t and b*.sub.t are chromaticity values of the specimen after exposure to light.

[0132] (3) Tensile Strength

[0133] The following specimen (FIG. 6) was prepared according to the standard of specimen Type V of ASTM D638. The specimen was left for 24 hours in a constant temperature and humidity room adjusted to a temperature of 23 ° C. and a relative humidity of 50%, and then subjected to a tensile test.

[0134] The tensile strength (MPa) of the specimen was measured according to ASTM D638 using a universal testing machine (UTM) manufactured by Instron. In accordance with ASTM D638, a gap between the grips holding the specimen at both ends was set to 25.4 mm, and the test was performed at a constant tensile rate with a crosshead speed of 5 mm/min.

[0135] (4) Flexural Strength and Flexural Modulus

[0136] A specimen having a size of 80 mm×10 mm×4 mm was prepared according to ISO 178. The specimen was left for 24 hours in a constant temperature and humidity room adjusted to a temperature of 23 ° C. and a relative humidity of 50%, and then subjected to a flexural test.

[0137] The flexural strength (MPa) of the specimen was measured according to ISO 178 using a universal testing machine (UTM) manufactured by Instron. In accordance with ISO 178, a supports span was set to 46 mm using a three-point flexural test jig, and flexural strength was obtained by performing a flexural test under a crosshead speed of 5 mm/min.

TABLE-US-00001 TABLE 1 Minor axis diameter Microcellulose Size of inorganic fibers (μm) Nanofibrils (nm) particles (μm) Preparation 1~10 50~100 0.05~0.1 Example 1 Preparation 1~10 50~100 0.05~0.5 Example 2 Preparation 1~10 50~100 0.1~1 Example 3 Preparation 1~10 50~100 0.1~1 Example 4 Preparation none 10~100 0.1~1 Example 5

TABLE-US-00002 TABLE 2 Color Flexural Flexural Tensile difference strength modulus strength (ΔE*ab) (MPa) (GPa) (MPa) Examples 1 14.4 62 2.3 51 2 13.2 64 2.3 52 3 8.4 65 2.6 54 4 2.0 65 2.5 55 5 5.0 79 3.0 60 6 10.0 55 1.7 42 Comparative 1 15.7 63 2.6 56 Examples 2 17.0 62 2.6 55 3 15.2 45 1.7 31

[0138] Referring to Table 2, it was confirmed that the polymer composites according to Examples exhibited superior light resistance compared to the polymer composite according to Comparative Example 1.