BI-COMPONENT MICROFIBERS WITH HYDROPHILIC POLYMERS ON THE SURFACE WITH ENHANCED DISPERSION IN ALKALINE ENVIRONMENT FOR FIBER CEMENT ROOFING APPLICATION

Abstract

The present invention provides bi-component core-shell polymeric microfibers for reinforcing concrete comprising as a first component (shell) ethylene-vinyl alcohol (EVOH) polymer and at least one plasticizer, preferably, polyethylene glycol, and as a second component (core) a polymer chosen from a polyamide, a polyester, such as polyethylene terephthalate, and a polymer blend of a polyolefin and an anhydride grafted polyolefin and having an aspect ratio of length to diameter (L/D) or equivalent diameter of from 300 to 1000. The bi-component polymeric microfibers comprise from 5 to 45 wt. % of the first component, are easily processed, and provide fiber cements having improved mechanical properties at relatively low microfiber loadings.

Claims

1. A composition comprising bi-component polymeric microfibers for reinforcing concrete having as an outer or first component or shell ethylene-vinyl alcohol (EVOH) polymer having from 30 mol % to 50 mol % of ethylene, and at least one plasticizer, and as a second component or core a polymer chosen from a polyamide, a polyester, and a polymer blend of, on one hand, a polyolefin, and, on the other hand, an anhydride grafted polyolefin, the bi-component polymeric microfibers having an aspect ratio of length to diameter (L/D) or equivalent diameter of from 300 to 1000.

2. The composition of bi-component polymeric microfibers as claimed in claim 1, wherein the at least one plasticizer is a polyalkylene glycol, a methoxypolyalkylene glycol, or their admixture, and, wherein the microfibers have an equivalent diameter of <0.3 mm or less than 30 microns per ASTM D7580/D7580M (2015).

3. The composition of bi-component polymeric microfibers as claimed in claim 1, wherein in the first component the total amount of the plasticizer ranges from 1 to 10 wt. %, based on the total weight of the first component of the bi-component polymeric microfibers.

4. The composition of bi-component polymeric microfibers as claimed in claim 1, wherein the second component comprises a polymer blend of a polyolefin and an ethylenically unsaturated anhydride grafted olefin polymer.

5. The composition of bi-component polymeric microfibers as claimed in claim 1, wherein the second component comprises a polymer blend of a polypropylene and a maleic anhydride grafted polypropylene.

6. The composition of bi-component polymeric microfibers as claimed in claim 1, wherein the second component is a polymer blend of a polypropylene and polypropylene grafted with maleic anhydride, and the maleic anhydride proportion ranges from 0.01 to 0.3 wt. %, based on the total weight of the polymer blend solids of the second component.

7. The composition of bi-component polymeric microfibers as claimed in claim 1, wherein the EVOH polymer has a melt flow rate (MFR) of from 6.4 to 38 g/10 min at 210° C., 2.16 Kg (ASTM D1238-13 (2013) and, further wherein the second component comprises the polymer blend wherein the polyolefin is a polypropylene having a melt flow rate of from 12 to 24 g/10 min at 230° C. and 2.16 Kg (ASTM D1238-13 (2013)).

8. The composition of bi-component polymeric microfibers as claimed in claim 1, wherein the bi-component polymeric microfibers comprise a second component (core) to first component (shell) ratio of from 55 to 95 wt. % to 5 to 45 wt. % (or from 95:5 to 55:45), all weights based on the total weight of microfiber solids.

9. The composition of bi-component polymeric microfibers as claimed in claim 1, wherein the bi-component polymeric microfibers comprise a second component (core) to first component (shell) ratio of from 60 to 90 wt. % to from 10 to 40 wt. % (or from 60:40 to 90:10), all weights based on the total weight of microfiber solids.

10. The composition of bi-component polymeric microfibers as claimed in claim 1, wherein the composition comprises a wet fiber cement composition of the bi-component polymeric microfibers, and, further, comprises water, hydraulic cement, limestone aggregate and cellulosic fibers.

Description

EXAMPLES

[0086] The following examples are used to illustrate the present invention without limiting it to those examples. Unless otherwise indicated, all temperatures are ambient temperatures (21-23° C.) and all pressures are 1 atmosphere.

[0087] The inventive microfibers indicated in the Examples 1A, 2 and 3, below, the comparative polymer blend microfiber of Example 4, below, and the comparative bi-component polymer blend microfiber of Example 5, below, were extruded, formed and drawn via a melt spinning process. In the process, all indicated components were melted in an extruder, or, in the case of coextrusion, one component in each of two different extruders, and then pumped to a die that has plate designed to flow the one component, or in the case of two components, an inner and outer material in a bi-component core/shell configuration. Downstream of the die, the resulting fibers were drawn to a desired aspect ratio. The apparatus comprised Hills, Inc. (West Melbourne, Fla.) extruder equipment having a temperature profile of from 185-200° C., a flow through speed of 800 mpm, and a denier 5.9 den, wherein the extruder dies in the case of coextrusion were configured so that the second component flowed through a round die of 0.25 mm in diameter. In single component extrusion, the component flowed through a round die of 0.25 mm in diameter. A spinneret was located downstream of the co-extrusion equipment.

[0088] In coextrusion, the first component was co-extruded co-axially around the second component through an annular shaped die having an inner diameter matching the outer diameter of the round die. The spun fibers were then drawn to form bi-component polymeric microfibers having an average diameter of about 15 microns wherein the sheath of the first component formed an annulus of from 1 to 2 microns in thickness.

[0089] In extrusion, the one component was extruded through the round die and the spun fibers were then drawn to polymeric microfibers having an average diameter of about 15 microns.

[0090] Component proportions are indicated in the examples, below. Inventive proportions of the first component and second component of the bi-component polymeric microfibers were selected to target core/shell bi-component microfibers having an 80/20 ratio (w/w/) of second component or core to first component or shell. The first component EVOH was very difficult to extrude, shape and draw into a microfiber. Accordingly, the polyethylene glycol indicated in the examples below, was included in a melt of the first component; and the bi-component polymeric microfibers were produced via the melt spinning process. During extrusion the amounts of the first component and second component were varied in process to lower the proportion of the first component as much as possible. If possible, the proportion of the first component was lowered to 20 wt. % based on the total weight of bi-component polymeric microfiber solids. Where it was not possible to lower the first component proportion to 20 wt. %, the indicated proportion of the first component in the bi-component polymeric microfibers was the lowest proportion of first component obtained before the resulting microfibers would break upon drawing to form microfibers.

[0091] All fibers in the following Examples and Comparative Examples have an L/D of 600, a diameter of 15 micron, and a length of 9 mm.

[0092] The materials used in examples are, as follows:

[0093] Ethylene vinyl alcohol copolymer or EVOH: SOARNOL™ A4412 ethylene vinyl alcohol copolymer having a 44 mol % ethylene content, a melt flow rate (MFR) of 12 g/10 min (210° C., 2.16 Kg via melt index tester), a density (Micromeritics Gas Pycnometer, Micromeritics Instrument Corp., Norcross, Ga.) of 1.14 g/cm.sup.3 at 23° C. and a melting point of 164° C. (DSC heating and cooling speeds of 10° C./min) (Soarus LLC, Arlington Heights, Ill.).

[0094] Polyethylene glycol or PEG: MW of 7000 to 9000, density 1.07 (g/cm.sup.3; 70° C.); heat of fusion 41 (Cal/g); average number of repeating oxyethylene units 181.

[0095] Maleic anhydride grafted polypropylene or PP-g-MAH: POLYBOND™ 3150 maleic anhydride grafted polypropylene having a maleic anhydride content of from 0.7 wt. %, a melt flow rate (MFR) of 52 g/10 min (230° C., 2.16 Kg via melt index tester) and a density 0.91 g/cm.sup.3 at 23° C. (Addivant corporation, Danbury, Conn.). Various PP-g-MAH materials and their polymer blends are given in Tables 2A and 2B, below.

[0096] Polypropylene or PP: Polypropylene D180M PP having a MFR of 18 g/10 min at 230° C., 2.16 Kg (Braskem USA, Philadelphia, Pa.). Having a melting point MP (DSC) of 160° C., a density of 0.905 g/cc and an MFR of 18 g/10 min at 230° C., 2.16 Kg. Various PP materials and their polymer blends are given in Table 2, below.

[0097] Polyvinyl alcohol (PVOH) microfibers: High tenacity and high modulus PVA fiber W1 6 mm from Anhui Wanwei Updated Hightech Material Industry Co. Ltd., Chao hu, Anhui, China. PVOH fiber properties are presented in Table 1, below.

[0098] PP microfibers: PP monofilament 1.10 dtex×9 mm (Saint Gobain do Brasil Produtos Ind. e para const. Ltda-Brasilit Cia.). The PP fiber properties are presented in Table 2A, below.

[0099] MB2: The composition shown in Table 2B, below, was prepared by extrusion in a 26 mm twin screw extruder (44 L/D and 30 HP) having eleven (11) barrels and equipped with a 3 mm, 2 hole strand type die. Pellets of each of PP and PP-g-MAH were fed into the extruder using Ktron™ single screw feeders (Coperion GmbH, Stuttgart, Del.). The materials were fed into the main feed throat (barrel #1) with nitrogen gas in the feed throat. The strands were run through a 3.048 meter water bath and were pelletized using a Conair strand cutter (Conair, Stamford, Conn.). The total feed rate was 18.14 Kg/hr, and at a screw speed of 300 RPM. The temperature set points were 60° C. in zone 1 of barrel #2 and 180° C. in the remaining zones.

TABLE-US-00001 TABLE 1 PVOH fiber properties Properties value Linear density (dtex) 2 Tenacity (cN/dtex) 12.2 Elongation (%) 6.8 Hot water solubility (90° C., 1 h) 0.7 Dispersion grade (class) 1 Length (mm) 6

TABLE-US-00002 TABLE 2A PP fiber properties Properties value specification Title 1.12 dtex ≤1.20 dtex Tenacity 10.18 cN/dtex ≥9.50 cN/dtex Elongation 19.42% ≤25% Moisture content    2% 1.5-2.5% Finishing content  0.68% 0.6-0.7% Dispersion grade 3 level 2 to 3

TABLE-US-00003 TABLE 2B Second Component Second Component MB2 Composition Composition 80 wt. % PP 75 wt. % PP 20 wt. % PP-g-MAH 25 wt. % MB2

TABLE-US-00004 TABLE 2C Second Component Acid Content Material Acid content (wt. %) MB2 0.14 Second Component 0.035 If second component diluted down 3× 0.012 with neat PP

[0100] Test Methods:

[0101] The following test methods were used in evaluating the Examples. The indicated aqueous dispersions of each of the indicated bi-component polymeric microfibers were tested for dispersibility in water. Separately, the bi-component polymeric microfibers indicated in the examples C1, C2, 1A, 2, 3, 4, and 5, below, were made into cement fiberboards by the methods given above and were tested for mechanical properties.

[0102] Dispersibility was assessed by stirring the 0.02 g of the indicated bi-component polymeric microfibers for 3 min in 1 liter of alkaline water (pH=10-11, ammonium OH) then filtering it through a black polyester cloth (for contrast) by pulling with vacuum (200 to 300 mmHg). Then the solution was poured over a Buchner funnel having upstream of the porous plate filter paper (Whatman, 80 g/cm.sup.2, 10 cm diameter, Merck Millipore, Burlington, Mass.), and dark fabric (to enable visual evaluation). After removing the water, the patterns made by the fibers were assessed to evaluate their dispersibility. Fiber dispersibility was visually ranked with the following rating scale, as follows:

[0103] Grade 1: (completely dispersed) Microfibers are distributed homogeneously throughout the area of the filter paper, no clumped fibers;

[0104] Grade 2: 5-10 wt. % of the microfibers are clumped after filtering test;

[0105] Grade 3: 20-30 wt. % of the microfibers are clumped after filtering test;

[0106] Grade 4: (poor dispersibility) A majority of microfibers are clumped; poor bad distribution over the area of the filter paper.

[0107] Dispersibility results are reported on Table 3, below.

[0108] Mechanical Properties: Cement fiberboards were made using the wet compositions of bi-component polymeric microfibers in the manner indicated in each Example, below. Upon completing the curing period, fiber cement boards were cut (160 mm×40 mm×5 mm) and mechanical properties were assessed according to RILEM 49 TFR: testing method for fiber reinforced cement based composites, France, (1984). Specifically, a stress strain curve was generated by tensile testing the indicated fiber cement board using an INSTRON™ 5565 load testing machine (Instron, Norwood, Mass.), equipped with a 5 kgf load cell and a 5 mm/min load ratio on four steel cylindrical bending points, upper distance between point is 45 mm and lower distance between points is 135 mm, wherein two are placed centered on a stage underneath the cement fiberboard and flush to each edge of the underside of the 40 mm width of the fiberboard; and the two other bending points are placed underneath the stage a distance L mm apart so that the load cell is centered between each pair of bending points. The tensile tests generated a stress-strain curve from which the various mechanical properties were derived. Mechanical results can be found below in Table 4, below.

[0109] Stress-strain curve: Microfiber containing cement fiberboards that were made according to the indicated examples were subjected to mechanical testing by varying the stress, load or force generated on them and measuring the strain caused by each level of stress. The tests were used to generate a stress strain curve. obtained from the stress-strain curve during the tensile strength test.

[0110] Obtained from the stress-strain curve generated during the tensile test, the MOR or modulus of rupture is reported as the maximum stress supported by the composite matrix during the stress-strain test and is calculated with the ultimate load achieved during the test divided by the area of the fiberboard specimen. MOR is given by Equation 1, below, and is the average result reported from five (5) cement fiberboards selected at random. An acceptable modulus of rupture is at least 2.0 MPa, or preferably, at least 3.0 MPa.

[00001]$\begin{array}{cc}\mathrm{MOR}=\frac{F_2*L}{b*d^2}& \left(\mathrm{Equation}1\right)\end{array}$

[0111] Where:

[0112] F.sub.2, is the maximum load applied in N;

[0113] L, is the largest distance in mm between two lower load bearing points where the indicated cement fiberboard is placed onto two load bearing points across its width, which points are centered on top of a wider load bearing member that is supported by the two lower load bearing points;

[0114] b, is the cement fiberboard width in mm;

[0115] d, is the cement fiberboard thickness in mm.

[0116] Obtained from the stress-strain curve generated during the tensile test, the limit of proportionality (LOP) is the area corresponding to the elastic deformation in the stress-strain plot and is proportional to the applied load. LOP is calculated with the load at which the load-strain curve deviates from linearity, the beginning of the plastic deformation regime, Equation 2, below. An acceptable limit of proportionality is at least 2.0 MPa, or preferably, at least 2.5 MPa.

[00002]$\begin{array}{cc}\mathrm{LOP}=\frac{F_1*L}{b*d^2}& \left(\mathrm{Equation}2\right)\end{array}$

[0117] Where:

[0118] F.sub.1, is the load applied in LOP in N;

[0119] L, is the largest distance in mm between two lower load bearing points where the indicated cement fiberboard is placed onto two load bearing points across its width, which points are centered on top of a wider load bearing member that is supported by the two lower load bearing points;

[0120] b, is the sample width in mm;

[0121] d, is the sample thickness in mm.

[0122] Obtained from the stress-strain curve generated during the flexural deformation test, the Modulus of Elasticity (MOE) or Young's Modulus is calculated as the slope of the stress-strain curve in the elastic deformation regime (see Callister, D. W., Rethwish G. D., Materials Science and Engineering: An Introduction, 8th ed., John Wiley & Sons Inc., chapter 6, p. 157, 2012).

[0123] The higher the MOE, the greater the cement fiberboard stiffness and the lower its elastic deformation, where the stress is proportional to the deformation. An acceptable modulus of elasticity is at least 2.5 GPa.

[0124] Obtained from the stress-strain curve generated during the flexural deformation test, the Specific energy (SE) is defined as the energy absorbed during the stress-strain test and is calculated by integral of the area under the curve load vs strain, see Equation 3, below. The higher the SE value, the better the fiber reinforcement ability. An acceptable specific energy is at least 2.5 kJ/m.sup.2, or preferably, at least 3.5 kJ/m.sup.2.

[00003]$\begin{array}{cc}\mathrm{SE}=\frac{\mathrm{Energy}\mathrm{absorbed}}{b*d}& \left(\mathrm{Equation}3\right)\end{array}$

[0125] Where:

[0126] Energy absorbed is calculated as above.

[0127] b, is the sample width in mm;

[0128] d, is the sample thickness in mm.

Comparative Example 1 (C1): Polyvinyl Alcohol (PVOH) Microfibers

[0129] As a reference standard, cement fiberboards were prepared with PVOH microfibers and then assessed. A cement fiberboard was prepared by dispersing ordinary Portland cement (64 wt. %), limestone (31.1 wt. %), cellulose fiber (3 wt. %) and PVOH fiber (1.9 wt. %) in water. After that, water was removed by a dewatering process using a molding chamber and applying vacuum (200-300 mmHg). Fiber cement boards were cast in 4 layers. Each layer was pressed for 2 min at 3.2 MPa. At the end, one layer is placed on top of the other. The resulting board was finally pressed for 5 min at 3.2 MPa. This process roughly mimics the Hatschek process. Fiber cement boards were then “plastic sealed” (wrapped) in polyvinylidene fluoride wrap and left in oven for 24 h at 50° C.; after this period, the cement fiberboard was removed from the oven and let sit at room temperature (6 d/23±2° C.) for curing. Upon completing the curing period, fiber cement boards were cut (160 mm×40 mm×5 mm) and mechanical properties were assessed.

Comparative Example 2 (C2): Polypropylene (PP) Microfibers

[0130] Another reference standard, cement fiberboards were prepared with PP microfibers. The cement fiberboard was prepared by dispersing cement (64 wt. %), limestone (31.1 wt. %), cellulose fiber (3 wt. %) and PP fiber (1.4 wt. %) in water. After that, water was removed by dewatering process using a molding chamber and applying vacuum (200-300 mmHg). Fiber cement boards were cast in 4 layers. Each layer was pressed for 2 min at 3.2 MPa. At the end, one layer is placed on top of the other. The resulting board was finally pressed for 5 min at 3.2 MPa. Fiber cement boards were then wrapped in polyvinylidene fluoride wrap and left in an oven for 24 h at 50° C.; after this period the product was removed from the oven and let at room temperature (6 d/23±2° C.) for curing. Upon completing the curing period, fiber cement boards were cut (160 mm×40 mm×5 mm) and mechanical properties were assessed.

Example 1: PP+PP-g-MAH Core/EVOH Shell Microfiber

[0131] A bi-component polymeric microfiber (second component PP+PP-g-MAH and first component EVOH) ratio 60/40 was prepared by co-extruding both polymer components in the melt extrusion process disclosed above. After collecting, fibers were post drawn 2.5× to achieve high polymer orientation and final tenacity, then continuous filament was cut in 9 mm lengths, diameter 25 microns and a L/D of 360 for dispersion tests.

Example 1A: PP+PP-g-MAH Core/EVOH Shell Microfiber with 5 wt. % Shell PEG Plasticizer Content and Cement Fiberboard with 1.9 wt. % of the Microfiber

[0132] A bi-component polymeric microfiber (second component as core PP+PP-g-MAH and, as the first component, EVOH with PEG 5 wt. % of first component) was prepared by co-extruding both polymer components in the melt extrusion process disclosed above. After collecting, fibers were post drawn 4.5-5.0× to achieve high polymer orientation and final tenacity, then continuous filament was cut in 9 mm lengths and a L/D of 600 for fiber cement application tests. Cement fiberboard was prepared with PP+PP-g-MAH/EVOHP fibers (1.9%) fibers by dispersing ordinary Portland cement (64%), limestone (31.1%), cellulose fiber (3%) and PP+PP-g-MAH/EVOH fibers (1.9%) in water. After that, water was removed by dewatering process using a molding chamber and applying vacuum (200-300 mmHg). Fiber cement boards were cast in 4 layers. Each layer was pressed for 2 min at 3.2 MPa. At the end, one layer is placed on top of the other. The resulting board was finally pressed for 5 min at 3.2 MPa. Fiber cement boards were then wrapped in polyvinylidene fluoride wrap and left in an oven for 24 h at 50° C.; after this period, the cement fiberboard was removed from the oven and left at room temperature (6 d/23±2° C.) for curing. Upon completing the curing period, fiber cement boards were cut (160 mm×40 mm×5 mm) and their mechanical properties assessed.

Example 2: PP+PP-g-MAH Core/EVOH Shell Microfiber with 5 wt. % Shell PEG Plasticizer Content and Cement Fiberboard with 1.4 wt. % of the Microfiber

[0133] A bi-component microfiber in accordance with the present invention (second component as core PP+PP-g-MAH and as first component EVOH with PEG 5 wt. % of first component) was prepared by co-extruding both polymers components in the melt extrusion process disclosed above. After collecting, fibers were post drawn 4.5-5.0× to achieve high polymer orientation and final tenacity, then continuous filament was cut in 9 mm lengths and an L/D of 600 for fiber cement application tests. Cement fiberboard was prepared by dispersing ordinary Portland cement (64 wt. %), limestone (31.1 wt. %), cellulose fiber (3 wt. %) and PP+PP-g-MAH/EVOHP fibers (1.4 wt. %) in water. After that, the water was removed by dewatering process using a molding chamber and applying vacuum (200-300 mmHg). Fiber cement boards were cast in 4 layers. Each layer was pressed for 2 min at 3.2 MPa. At the end, one layer is placed on top of the other. The resulting board was finally pressed for 5 min at 3.2 MPa. Fiber cement boards were then wrapped in polyvinylidene fluoride wrap and left in an oven for 24 h at 50° C.; after this, the product was removed from the oven and let sit at room temperature (6 d/23±2° C.) for curing. Upon completing the curing period, fiber cement boards were cut (160 mm×40 mm×5 mm) and their mechanical properties assessed.

Example 3: PP+PP-g-MAH Core/EVOH Microfiber with 2.5 wt. % Shell Plasticizer Content 0.5 wt. % and Cement Fiberboard with 1.9 wt. % of the Microfiber

[0134] A bi-component microfiber in accordance with the present invention (second component as core PP+PP-g-MAH and as first component, EVOH+PEG 2.5 wt. % of first component) prepared by co-extruding both polymers components in the melt extrusion process, disclosed above. After collecting, fibers were post drawing 4.5-5.0× to achieve high polymer orientation and final tenacity, then continuous filament was cut in 9 mm length and L/D of 600 for fiber cement application tests. Fiber cement composites were prepared with PP+PP-g-MAH/EVOHP microfibers (1.9 wt. %) by dispersing cement (64 wt. %), limestone (31.1 wt. %), cellulose fiber (3 wt. %) and PP+PP-g-MAH/EVOHP fibers (1.9 wt. %) in water. After that, water was removed by dewatering process using a molding chamber and applying vacuum (200-300 mmHg). Fiber cement boards were cast in 4 layers. Each layer was pressed for 2 min at 3.2 MPa. At the end, one layer is placed on top of the other. The resulting board was finally pressed for 5 min at 3.2 MPa. Fiber cement boards were then wrapped in polyvinylidene fluoride wrap and left in an oven for 24 h at 50° C.; after this period the product was removed from the oven and let sit at room temperature (6 d/23±2° C.) for curing. Upon completing the curing period, fiber cement boards were cut (160 mm×40 mm×5 mm) and their mechanical properties assessed.

Comparative Example 4: PP/PP-g-MAH Polymer Blend Microfibers

[0135] A bi-component microfiber in accordance with the present invention core PP and shell (PP-g-MAH) was prepared by co-extruding both polymer components in the melt extrusion process, disclosed above. After collecting, fibers were post drawing 4.5-5.0× to achieve high polymer orientation and final tenacity, then continuous filament was cut in 9 mm length and an L/D of 600 for fiber cement application tests. Cement fiberboards were prepared by dispersing cement (64 wt. %), limestone (31.1 wt. %), cellulose fiber (3 wt. %) and PP/PP-g-MAH fibers (1.4 wt. %) in water. After that, water was removed by dewatering process using a molding chamber and applying vacuum (200-300 mmHg). Fiber cement boards were cast in 4 layers. Each layer was pressed for 2 min at 3.2 MPa. At the end, one layer is placed on top of the other. The resulting board was finally pressed for 5 min at 3.2 MPa. Fiber cement boards were then wrapped in polyvinylidene fluoride wrap and left in an oven for 24 h at 50° C.; after this period, the product was removed from the oven and let sit at room temperature (6 d/23±2° C.) for curing. Upon completing the curing period, fiber cement boards were cut (160 mm×40 mm×5 mm) and their mechanical properties assessed.

Comparative Example 3: PP+PP-g-MAH/EVOH (w/o Plasticizer) Fiber Cement Board with 1.9% of the Microfiber

[0136] A bi-component microfiber in accordance with the present invention (core PP and shell (PP-g-MAH) was prepared by co-extruding both polymer components in the melt extrusion process, disclosed above. After collecting, fibers were post drawing 2.5× to achieve high polymer orientation and final tenacity, then continuous filament was cut in 9 mm length and final diameter was 24.1 micron, an L/D of 370 for fiber cement application tests. Cement fiberboards were prepared by dispersing cement (64 wt. %), limestone (31.1 wt. %), cellulose fiber (3 wt. %) and PP/PP-g-MAH fibers (1.9 wt. %) in water. After that, water was removed by dewatering process using a molding chamber and applying vacuum (200-300 mmHg). Fiber cement boards were cast in 4 layers. Each layer was pressed for 2 min at 3.2 MPa. At the end, one layer is placed on top of the other. The resulting board was finally pressed for 5 min at 3.2 MPa. Fiber cement boards were then wrapped in polyvinylidene fluoride wrap and left in an oven for 24 h at 50° C.; after this period, the product was removed from the oven and let sit at room temperature (6 d/23±2° C.) for curing. Upon completing the curing period, fiber cement boards were cut (160 mm×40 mm×5 mm) and their mechanical properties assessed.

TABLE-US-00005 TABLE 3 Dispersibility in water Result Example Bi-component polymeric microfibers (Grade) C1* PVOH 1 C2* PP 3 1 core (PP + PP-g-MAH) and shell EVOH 1 *Denotes Comparative Example.

[0137] As shown in Table 3 above, the inventive bi-component microfibers of Example 1 exhibit the same excellent dispersibility in water the PVOH microfibers of Comparative Example 1 and dramatically outperform the PP microfibers of Comparative Example 2.

TABLE-US-00006 TABLE 4 Mechanical Testing Performance Microfiber Core/ MOR LOP SE MOE Example Material loading Shell ratio (MPa) (MPa) (kJ/m.sup.2) (GPa) C1* PVOH 1.9 wt. % n/a 7.46 3.71 6.58 9.67 C2* PP 1.4 wt. % n/a 4.43 2.67 4.74 3.80 1A PP + PP-g- 1.9 wt. % 80/20 5.48 3.29 5.88 4.57 MAH/ EVOH (5 wt. % PEG) 2 PP + PP-g- 1.4 wt. % 80/20 4.49 3.04 4.72 4.76 MAH/ EVOHP (5 wt. % PEG) 3 PP + PP-g- 1.9 wt. % 80/20 4.21 2.67 4.57 2.54 MAH/ EVOHP (2.5 wt. % PEG) 4* PP/PP-g- 1.4 wt. % 80/20 4.19 2.29 4.37 3.48 MAH 5* PP + PP-g- 1.9 wt. % 50/50 3.57 2.93 2.45 4.36 MAH/ EVOH (w/o plasticizer) *Denotes Comparative Example.

[0138] As shown in Table 4, above, the inventive bi-component polymeric microfibers in Examples 1A, 2 and 3 demonstrated good mechanical properties, as did the polymeric microfibers of Comparative Examples C1, C2 and 4. The Mechanical properties of the inventive bi-component polymeric microfibers in Examples 1A, 2 and 3 demonstrated superior mechanical properties compared to the bi-component polymeric microfibers of Comparative Example 5 because they comprised a higher proportion of the core second component than the comparative bi-component polymeric microfibers. In addition, the inventive bi-component polymeric microfibers in Examples 1A, 2 and 3 demonstrated excellent processability and spinnability unlike those of Comparative Example 5 which could not be processed at an EVOH level below 50 wt. % of the bi-component polymeric microfiber solids which would lead to inadequate ductility. Further, the inventive bi-component polymeric microfibers in Example 2 demonstrated improved mechanical properties compared to the same polymeric microfibers of Comparative Example 4 without the first component. It was not expected that one could make microfibers having an EVOH sheath, much less bi-component polymeric microfibers having mechanical properties that were superior to the same microfibers without EVOH.