Fiber reinforced polypropylene composite

Abstract

The present invention relates to a new composite comprising glass or carbon fibers and polymer-based fibers as well as to a process for the preparation of the composite and molded articles made from said composite.

Claims

1. Composite comprising: a) 50 to 91.0 wt %, based on the total weight of the composite, of a polypropylene base material having a melt flow rate MFR.sub.2 (230° C., 2.16 kg) measured according to ISO 1133 in the range of from 3.0 to 140.0 g/10 min, wherein the polypropylene base material is i) a heterophasic propylene copolymer (HECO) comprising a semicrystalline polypropylene (PP) as a matrix in which an elastomeric propylene copolymer (EC) is dispersed or ii) a propylene homopolymer (hPP); and b) 8.6 to 45.0 wt %, based on the total weight of the composite, of a glass fiber (GF) or carbon fiber (CF); and c) 2.5 to 20 wt %, based on the total weight of the composite, of a polymer-based fiber (PF) having a melting temperature of ≥210° C., wherein the polymer-based fiber (PF) also has a fiber average diameter in the range of 5 to 30 μm, a tenacity of from 3.0 cN/dtex, or both; and d) 0.1 to 7.0 wt %, based on the total weight of the composite, of an adhesion promoter (AP), where the adhesion promoter is a maleic anhydride functionalized polypropylene, wherein the weight ratio of the glass fiber (GF) or carbon fiber (CF) to the polymer-based fiber (PF) [(GF) or (CF)/(PF)] is at least 2:1.

2. Composite according to claim 1, wherein the heterophasic propylene copolymer (HECO) has a) a melt flow rate MFR.sub.2 (230° C., 2.16 kg) in the range of from 5.0 to 120.0 g/10 min, and/or b) a xylene cold soluble (XCS) fraction (25° C.) of from 15.0 to 50.0 wt %, based on the total weight of the heterophasic propylene copolymer (HECO), and/or c) a comonomer content of ≤30.0 mol %, based on the heterophasic propylene copolymer (HECO).

3. Composite according to claim 1, wherein an amorphous fraction (AM) of the heterophasic propylene copolymer (HECO) has a) a comonomer content in the range of 30.0 to 60.0 mol %, based on the amorphous fraction (AM) of the heterophasic propylene copolymer (HECO), and/or b) an intrinsic viscosity (IV) in the range of 1.8 to 4.0 dl/g.

4. Composite according to claim 1, wherein the propylene homopolymer (hPP) has: a) a melt flow rate MFR.sub.2 (230° C., 2.16 kg) in the range of from 5.0 to 120.0 g/10 min, and/or b) a melting temperature measured according to ISO 11357-3 of at least 150° C., and/or c) a xylene cold soluble (XCS) content based on the total weight of the propylene homopolymer (hPP).

5. Composite according to claim 1, wherein the glass fiber (GF) or carbon fiber (CF) has a fiber average diameter in the range of 5 to 30 μm and/or an average fiber length from 0.1 to 20 mm.

6. Composite according to claim 1, wherein the glass fiber (GF) or carbon fiber (CF) comprises a sizing agent.

7. Composite according to claim 1, wherein the polymer-based fiber (PF) is selected from the group consisting of a poly vinyl alcohol (PVA) fiber, a polyethylene terephthalate (PET) fiber, a polyamide (PA) fiber and mixtures thereof.

8. Composite according to claim 1, wherein the polymer-based fiber (PF) also has an average fiber length of 0.1 to 20 mm.

9. Composite according to claim 1, wherein the melting temperature Tm according to ISO 11357-3 of the polymer-based fiber (PF) is ≥40° C. above the melting temperature Tm according to ISO 11357-3 of the polypropylene base material.

10. Molded article comprising the composite according to claim 1.

11. Molded article according to claim 10, wherein the molded article is an automotive article.

Description

EXAMPLES

1. Definitions/Measuring Methods

(1) The following definitions of terms and determination methods apply for the above general description of the invention as well as to the below examples unless otherwise defined.

(2) Quantification of Microstructure by NMR Spectroscopy

(3) Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content of the polymers. Quantitative .sup.13C {.sup.1H} NMR spectra were recorded in the solution-state using a Bruker Advance III 400 NMR spectrometer operating at 400.15 and 100.62 MHz for .sup.1H and .sup.13C respectively. All spectra were recorded using a .sup.13C optimised 10 mm extended temperature probehead at 125° C. using nitrogen gas for all pneumatics. Approximately 200 mg of material was dissolved in 3 ml of 1,2-tetrachloroethane-d.sub.2 (TCE-d.sub.2) along with chromium-(III)-acetylacetonate (Cr(acac).sub.3) resulting in a 65 mM solution of relaxation agent in solvent (Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009), 475). To ensure a homogenous solution, after initial sample preparation in a heat block, the NMR tube was further heated in a rotatary oven for at least 1 hour. Upon insertion into the magnet the tube was spun at 10 Hz. This setup was chosen primarily for the high resolution and quantitatively needed for accurate ethylene content quantification. Standard single-pulse excitation was employed without NOE, using an optimised tip angle, 1 s recycle delay and a bi-level WALTZ16 decoupling scheme (Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225; Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1128). A total of 6144 (6 k) transients were acquired per spectra.

(4) Quantitative .sup.13C {.sup.1H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals using proprietary computer programs. All chemical shifts were indirectly referenced to the central methylene group of the ethylene block (EEE) at 30.00 ppm using the chemical shift of the solvent. This approach allowed comparable referencing even when this structural unit was not present. Characteristic signals corresponding to the incorporation of ethylene were observed Cheng, H. N., Macromolecules 17 (1984), 1950).

(5) With characteristic signals corresponding to 2,1 erythro regio defects observed (as described in L. Resconi, L. Cavallo, A. Fait, F. Piemontesi, Chem. Rev. 2000, 100 (4), 1253, in Cheng, H. N., Macromolecules 1984, 17, 1950, and in W-J. Wang and S. Zhu, Macromolecules 2000, 33 1157) the correction for the influence of the regio defects on determined properties was required. Characteristic signals corresponding to other types of regio defects were not observed.

(6) The comonomer fraction was quantified using the method of Wang et. al. (Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157) through integration of multiple signals across the whole spectral region in the .sup.13C {.sup.1H} spectra. This method was chosen for its robust nature and ability to account for the presence of regio-defects when needed. Integral regions were slightly adjusted to increase applicability across the whole range of encountered comonomer contents.

(7) For systems where only isolated ethylene in PPEPP sequences was observed the method of Wang et. al. was modified to reduce the influence of non-zero integrals of sites that are known to not be present. This approach reduced the overestimation of ethylene content for such systems and was achieved by reduction of the number of sites used to determine the absolute ethylene content to:
E=0.5(Sββ+Sβγ+Sβδ+0.5(Sαβ+Sαγ))

(8) Through the use of this set of sites the corresponding integral equation becomes:
E=0.5(I.sub.H+I.sub.G+0.5(I.sub.C+I.sub.D))
using the same notation used in the article of Wang et. al. (Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157). Equations used for absolute propylene content were not modified.

(9) The mole percent comonomer incorporation was calculated from the mole fraction:
E[mol %]=100*fE

(10) The weight percent comonomer incorporation was calculated from the mole fraction:
E[wt %]=100*(fE*28.06)/((fE*28.06)+((1−fE)*42.08))

(11) The comonomer sequence distribution at the triad level was determined using the analysis method of Kakugo et al. (Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150). This method was chosen for its robust nature and integration regions slightly adjusted to increase applicability to a wider range of comonomer contents.

(12) DSC analysis, melting temperature (T.sub.m) and heat of fusion (H.sub.f), crystallization temperature (T.sub.e) and heat of crystallization (H.sub.e): measured with a TA Instrument Q2000 differential scanning calorimetry (DSC) on 5 to 7 mg samples. DSC is run according to ISO 11357/part 3/method C2 in a heat/cool/heat cycle with a scan rate of 10° C./min in the temperature range of −30 to +225° C. Crystallization temperature and heat of crystallization (H.sub.c) are determined from the cooling step, while melting temperature and heat of fusion (H.sub.f) are determined from the second heating step.

(13) Density is measured according to ISO 1183-1—method A (2004). Sample preparation is done by compression molding in accordance with ISO 1872-2:2007.

(14) MFR.sub.2 (230° C.) is measured according to ISO 1133 (230° C., 2.16 kg load).

(15) MFR.sub.2 (190° C.) is measured according to ISO 1133 (190° C., 5 kg or 2.1 kg load).

(16) The xylene cold solubles (XCS, wt.-%): Content of xylene cold solubles (XCS) is determined at 25° C. according to ISO 16152; first edition; 2005Jul, 1

(17) The amorphous content (AM) is measured by separating the above xylene cold soluble fraction (XCS) and precipitating the amorphous part with acetone. The precipitate was filtered and dried in a vacuum oven at 90° C.

(18) $\mathrm{AM}\%=\frac{100*m1*v0}{m0*v1}$

(19) wherein

(20) “AM %” is the amorphous fraction,

(21) “m0” is initial polymer amount (g)

(22) “m1” is weight of precipitate (g)

(23) “v0” is initial volume (ml)

(24) “v1” is volume of analyzed sample (ml)

(25) Intrinsic viscosity is measured according to DIN ISO 1628/1, October 1999 (in Decalin at 135° C.).

(26) Charpy notched impact strength is determined according to ISO 179/1 eA at 23° C. and at −20° C. by using injection moulded test specimens of 80×10×4 mm.sup.3 prepared in accordance with EN ISO 19069-2.

(27) Charpy unnotched impact strength is determined according to ISO 179/1 eU at 23° C. by using injection moulded test specimens of 80×10×4 mm.sup.3 prepared in accordance with EN ISO 19069-2.

(28) Tensile Modulus is measured according to ISO 527-2 (cross head speed=1 mm/min; 23° C.) using injection molded specimens as described in EN ISO 1873-2 (dog bone shape, 4 mm thickness).

(29) Elongation at yield is measured according to ISO 527-2 (cross head speed=50 mm/min; 23° C.) using injection molded specimens as described in EN ISO 1873-2 (dog bone shape, 4 mm thickness).

(30) Tensile strength is measured according to ISO 527-2 (cross head speed=50 mm/min; 23° C.) using injection molded specimens as described in EN ISO 1873-2 (dog bone shape, 4 mm thickness).

(31) Elongation at break is measured according to ISO 527-2 (cross head speed=50 mm/min; 23° C.) using injection molded specimens as described in EN ISO 1873-2 (dog bone shape, 4 mm thickness).

(32) Average fiber diameter, average fiber length and aspect ratio: Pellets obtained from pultrusion were embedded in Struers CaldoFix resin under vacuum. For determining the average fiber diameter, the polished cross sections of these pellets were determined. Abrasion/polishing was performed on a Struers LaboPol-5 machine, employing grinding media with particle sizes down to 0.04 μm. The samples thus prepared were analyzed using an Olympus optical microscope in brightfield mode. The dimensions of the fiber cross-sections of the fibers in the matrix were measured to get the average fiber-diameter (typically around 30 individual fibers were measured and the shortest dimension of the fiber cross-section was used to get the fiber diameter).

(33) In contrast, the average fiber length was determined by X-ray computed tomography (XCT). For the generation of XCT data a sub-μm CT nanotom (GE phoenix x-ray nanotom 180NF, Wunstorf, Germany) was used. The tube was operated at 70 kV to obtain enough contrast. The voxel size was (2 μm).sup.3, the measured volume was (5×2×3 mm).sup.3 of a sample of injection moulded specimen as described in EN ISO 1873-2 (dog bone shape, 4 mm thickness). The XCT data were processed by various algorithmic steps to ascertain the three-dimensional structure of the sample. The fibre length distribution was derived from the XCT data and the weighted mean average of the fibre length distribution was taken as the average fibre length. The aspect ratio can be calculated from the average fiber diameter and length.

2. Examples

(34) Composites were prepared using the components in the amounts as indicated in table 1 below and as explained further below. Pellets of the Masterbatch1, Masterbatch2, Masterbatch3, and Masterbatch4 were prepared by impregnating the endless fibers in a pultrusion process. The impregnating was carried out at a temperature not exceeding 210° C.

(35) TABLE-US-00001 TABLE 1 Examples Masterbatch1 Masterbatch2 Masterbatch3 Masterbatch4 Example (PP-LPETF) (PP-LPETF) (PP-LGF) (PP-LCF) hPP [wt.-%] 75.1 62.3 71.2 66.3 LPETF [wt.-%] 24.9 37.7 — — LGF [wt.-%] — — 27.0 — LCF [wt.-%] — — — 27.0 AP [wt.-%] — — 1.8 6.8 Density [kg/m.sup.3] 990 1040 1080 1040 Tensile [MPa] 2254 2470 6367 12100 modulus Tensile [MPa] 51.5 47.4 109.2 79.6 strength Tensile [%] 24.4 22.5 2.6 0.8 Elongation at yield Tensile [%] 25.7 23.5 2.6 0.8 Elongation at break NIS [kJ/m.sup.2] 70.6 94.6 24.8 10.5 (23° C.) “hPP” is the commercial polypropylene homopolymer “HJ120UB” containing nucleating and antistatic additives, provided by Borealis. This polymer is a CR (controlled rheology) grade with narrow molecular weight distribution, density of 905 kg/m.sup.3 (ISO1183) and an MFR.sub.2 of 75 g/10 min (230° C.; 2.16 kg; ISO 1133); XCS of 2.2 wt.-% and melting temperature of 164° C. and a Charpy Notched Impact Strength at 23° C. of 1.0 kJ/m.sup.2. “LPETF” is the commercial endless PET multifilament yarn on bobbins PES 11000 f2000 Type 715, tenacity of 74.5 cN/dtex, elongation at break 13%, with a specific surface-treatment for PP, supplied by Durafiber Technologies, Germany. “LGF” is the commercial endless glass fiber Tufrov 4599, 1200 tex, of PPG Industries having an average diameter of 17 μm and a silane sizing agent for glass. “LCF” is the commercial endless carbon fiber Panex 35 continuous tow of Zoltek, having an average diameter of 7.2 μm, tensile strength of 4.137 MPa, tensile modulus of 242 GPa and a density of 1.81 g/cc. “AP” is an ethylene polypropylene copolymer functionalized with maleic anhydride having a MFR.sub.2 (190° C.) of more than 80 g/10 min and a maleic anhydride content of 1.4 wt.-% “NIS” is the notched impact strength.

(36) The Masterbatches1 to 4 were dry-blended for preparing inventive examples IE1, IE2, IE4 and IE5 as outlined in table 2a. IE3, CE2 and CE3 were directly prepared by impregnating the given fibers in a pultrusion process. The impregnating was carried out at a temperature of about 210° C. Comparative example CE1 is the commercial sample GB215HP of Borealis comprising 22 wt.-% glass fibers. Injection molding of the inventive and comparative examples was carried out on a Battenfeld HM 1300/350 injection molding machine. The composition of the comparative and inventive composites and their characteristics are indicated in table 2b below.

(37) TABLE-US-00002 TABLE 2a Examples Example IE1 IE2 IE4 IE5 Masterbatch1 [wt.-%] 25.0 25.0 Masterbatch2 [wt.-%] 25.0 25.0 Masterbatch3 [wt.-%] 75.0 75.0 Masterbatch4 [wt.-%] 75.0 75.0

(38) TABLE-US-00003 TABLE 2b Composition and characteristics Example CE1 CE2 CE3 IE1 IE2 IE3 IE4 IE5 hPP [wt.-%] 78.0 75.0 69.0 72.2 69.0 65.3 68.5 LPETF [wt.-%] 9.43 6.23 10.0 9.43 6.23 LGF [wt.-%] 20.0 20.3 20.3 20.0 LCF [wt.-%] 20.0 20.3 20.3 AP [wt.-%] 2.0 5.0 1.35 1.35 1.1 5.06 5.06 Density [kg/m.sup.3] 1030 1020 990 1070 1040 1080 1050 1040 Tensile [MPa] 4330 5001 9023 5017 4689 4733 5750 6080 modulus Tensile [MPa] 73.5 93.9 73.8 83.2 82 77 50.1 52.5 strength Tensile [%] 2.5 2.8 1.0 2.4 2.6 2.4 1.2 1.0 Elongation at yield Tensile [%] 2.5 2.9 1.0 2.4 2.6 2.5 1.3 1.0 Elongation at break NIS [kJ/m.sup.2] 15.1 17.0 6.9 37.7 30.1 39.1 26.6 20.3 (23° C.)

(39) From table 2b, it can be gathered that the inventive examples exhibit an improved mechanical property profile and especially and improved impact strength.