Polypropylene—carbon fiber composite

Abstract

The present invention refers to a fiber reinforced polymer composition comprising a polypropylene, carbon fibers and a polar modified polypropylene as coupling agent as well as to an article comprising the fiber reinforced polymer composition.

Claims

1. A fiber reinforced polymer composition comprising: (a) from 39 to 94 wt. %, based on the total weight of the fiber reinforced polymer composition, of a polypropylene (PP); (b) from 5 to 60 wt. %, based on the total weight of the fiber reinforced polymer composition, of carbon fibers (CF); and (c) from 1 to 10 wt. %, based on the total weight of the fiber reinforced polymer composition, of a polar modified polypropylene (PMP) as coupling agent, wherein the polar modified polypropylene (PMP) comprises groups derived from polar groups in an amount of from 1.5 to 4.0 wt. %, based on the total weight of the polar modified polypropylene (PMP), wherein the carbon fibers (CF) are in the form of a non-woven fabric.

2. The fiber reinforced polymer composition according to claim 1, wherein the polypropylene (PP) has: (a) a melt flow rate MFR.sub.2 (230 C., 2.16 kg) measured according to ISO 1133 of not more than 100 g/10 min; and/or (b) a melting temperature T.sub.m in the range of 160 to 170 C.; and/or (c) a ratio of weight average molecular weight (M.sub.w) to number average molecular weight (M.sub.n) [M.sub.w/M.sub.n] of from 1 to 10.

3. The fiber reinforced polymer composition according to claim 1, wherein the polypropylene (PP) is a propylene homopolymer (H-PP1) and/or a propylene copolymer (C-PP1).

4. The fiber reinforced polymer composition according to claim 1, wherein the non-woven fabric comprises at least 50 wt. % carbon fibers (CF), based on the total weight of the non-woven fabric.

5. The fiber reinforced polymer composition according to claim 1, wherein the carbon fibers (CF) comprise a sizing agent.

6. The fiber reinforced polymer composition according to claim 1, wherein the fiber reinforced polymer composition is free of fibers (F) being selected from the group comprising glass fibers, metal fibers, mineral fibers, ceramic fibers and mixtures thereof.

7. The fiber reinforced polymer composition according to claim 1, wherein the polar modified polypropylene (PMP) comprises groups derived from polar groups selected from the group consisting of acid anhydrides, carboxylic acids, carboxylic acid derivatives, primary and secondary amines, hydroxyl compounds, oxazoline and epoxides, and also ionic compounds.

8. The fiber reinforced polymer composition according to claim 1, wherein the polar modified polypropylene (PMP) is a propylene polymer grafted with maleic anhydride.

9. The fiber reinforced polymer composition according to claim 8, wherein the polar modified polypropylene (PMP) is a propylene copolymer grafted with maleic anhydride comprising ethylene as comonomer units.

10. The fiber reinforced polymer composition according to claim 1, wherein the fiber reinforced polymer composition further comprises at least one additive in an amount of up to 20 wt. %, based on the total weight of the fiber reinforced polymer composition.

11. The fiber reinforced polymer composition according to claim 1, wherein the fiber reinforced polymer composition further comprises 2.0 to 15.0 wt. %, based on the total weight of the fiber reinforced polymer composition, of an elastomeric copolymer (ECP) comprising units derived from ethylene and C.sub.4 to C.sub.8 -olefins.

12. The fiber reinforced polymer composition according to claim 1, wherein the fiber reinforced polymer composition has: (a) a melt flow rate MFR.sub.2 (230 C., 2.16 kg) measured according to ISO 1133 of from 5 to 75 g/10 min; and/or (b) density of equal or less than 1.200 g/cm .sup.3; and/or (c) a Charpy notched impact strength at +23 C. of 5.5 kJ/m.sup.2; and/or (d) a tensile strength according to ISO 527-2 of at least 100 MPa.

13. An article comprising a fiber reinforced polymer composition according to claim 1.

14. The article according to claim 13, wherein the article is a molded article.

15. The article according to claim 13, wherein the article is a part of washing machines or dishwashers or automotive articles.

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 is used to quantify the isotacticity and regio-regularity of the polypropylene homopolymers.

(4) 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.

(5) For polypropylene homopolymers approximately 200 mg of material was dissolved in 1,2-tetrachloroethane-d.sub.2 (TCE-d.sub.2). 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 needed for tacticity distribution quantification (Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443; Busico, V.; Cipullo, R., Monaco, G., Vacatello, M., Segre, A. L., Macromolecules 30 (1997) 6251). Standard single-pulse excitation was employed utilising the NOE and 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, 11289). A total of 8192 (8 k) transients were acquired per spectra.

(6) Quantitative .sup.13C{.sup.1H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals using proprietary computer programs.

(7) For polypropylene homopolymers all chemical shifts are internally referenced to the methyl isotactic pentad (mmmm) at 21.85 ppm.

(8) Characteristic signals corresponding to regio defects (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253; Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157; Cheng, H. N., Macromolecules 17 (1984), 1950) or comonomer were observed.

(9) The tacticity distribution was quantified through integration of the methyl region between 23.6-19.7 ppm correcting for any sites not related to the stereo sequences of interest (Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443; Busico, V., Cipullo, R., Monaco, G., Vacatello, M., Segre, A. L., Macromolecules 30 (1997) 6251).

(10) Specifically the influence of regio-defects and comonomer on the quantification of the tacticity distribution was corrected for by subtraction of representative regio-defect and comonomer integrals from the specific integral regions of the stereo sequences.

(11) The isotacticity was determined at the pentad level and reported as the percentage of isotactic pentad (mmmm) sequences with respect to all pentad sequences:
[mmmm]%=100*(mmmm/sum of all pentads)

(12) The presence of 2,1 erythro regio-defects was indicated by the presence of the two methyl sites at 17.7 and 17.2 ppm and confirmed by other characteristic sites. Characteristic signals corresponding to other types of regio-defects were not observed (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253).

(13) The amount of 2,1 erythro regio-defects was quantified using the average integral of the two characteristic methyl sites at 17.7 and 17.2 ppm:
P.sub.21e=(I.sub.e6+I.sub.e8)/2

(14) The amount of 1,2 primary inserted propene was quantified based on the methyl region with correction undertaken for sites included in this region not related to primary insertion and for primary insertion sites excluded from this region:
P.sub.12=I.sub.CH3+P.sub.12e

(15) The total amount of propene was quantified as the sum of primary inserted propene and all other present regio-defects:
P.sub.total=P.sub.12+P.sub.21e

(16) The mole percent of 2,1-erythro regio-defects was quantified with respect to all propene:
[21e]mol.-%=100*(P.sub.21e/P.sub.total)

(17) Characteristic signals corresponding to the incorporation of ethylene were observed (as described in Cheng, H. N., Macromolecules 1984, 17, 1950) and the comonomer fraction calculated as the fraction of ethylene in the polymer with respect to all monomer in the polymer.

(18) The comonomer fraction was quantified using the method of W-J. Wang and S. Zhu, Macromolecules 2000, 33 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.

(19) The mole percent comonomer incorporation was calculated from the mole fraction.

(20) The weight percent comonomer incorporation was calculated from the mole fraction.

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

(22) MFR.sub.2 (190 C.) is measured according to ISO 1133 (190 C., 2.16 kg load).

(23) MFR (170 C.) is measured in line with the general definitions of ISO 1133 (170 C., 1.2 kg load).

(24) DSC analysis, melting temperature (Tm) and melting enthalpy (Hm), crystallization temperature (Tc) and crystallization enthalpy (Hc): measured with a TA Instrument Q200 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 crystallization enthalpy (Hc) are determined from the cooling step, while melting temperature and melting enthalpy (Hm) are determined from the second heating step.

(25) The glass transition temperature Tg is determined by dynamic mechanical analysis according to ISO 6721-7. The measurements are done in torsion mode on compression moulded samples (40101 mm.sup.3) between 100 C. and +150 C. with a heating rate of 2 C./min and a frequency of 1 Hz.

(26) Density of the polymer composition is measured according to ISO 1183-187. Sample preparation is done by compression molding in accordance with ISO 1872-2:2007.

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

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

(29) Tensile Modulus; Tensile strength are 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).

(30) Charpy notched impact strength is determined according to ISO 179 1eA at 23 C. by using an 80104 mm.sup.3 test bars injection molded in line with EN ISO 1873-2.

(31) Average fiber diameter is determined according to ISO 1888:2006(E), Method B, microscope magnification of 1000.

2. Examples

(32) The following inventive example IE1 and comparative examples CE1 and CE2 were prepared by compounding on a co-rotating twin-screw extruder (ZSK 40 from Coperion).

(33) The following process parameters were used: throughput of 100 kg/h screw speed of 100-150 rpm barrel temperatures of 250 C. flat die plate with 5 mm holes, whereby 3 holes were opened.

(34) The polymer and the components different from the carbon fibers were fed to the extruder and melt-kneaded in the 4.sup.th barrel of the extruder which consists of three kneading blocks (two times a KB 45/5/40, followed by a KB 45/5/20 LH) and a left-handed conveying element. The carbon fibers were added in the 6.sup.th barrel using a side feeder. A second kneading zone located in the 8.sup.th barrel and consisting of three kneading blocks (KB 45/5/20) was used to distribute the carbon fibers homogeneously. Moreover, two TME elements (one TME 22.5/20 and one TME 22.5/20 LH) located between the 8.sup.th and the 9.sup.th barrel were used to further distribute the carbon fibers.

(35) Table 1 summarizes the composition of the inventive and comparative examples and their properties

(36) TABLE-US-00001 TABLE 1 Overview of composition and mechanics for inventive and comparative examples IE 1* CE 1* CE 2* PP [wt.-%] 63.35 63.35 PP-1 [wt.-%] 64 Carbon fibers [wt.-%] 20 20 Glass fibers [wt.-%] 22 Carbon black [wt.-%] 0.5 ECP1 [wt.-%] 10 10 ECP2 [wt.-%] 10 PMP [wt.-%] 5 PMP2 [wt.-%] 5 PMP2a [wt.-%] 1.5 MFR2 (230 C./2.16 kg) [g/10 min] 10.64 4.76 2 Density [g/cm.sup.3] 1084 1084 1232 Tensile modulus [MPa] 10835 11455 5300 Tensile strength [MPa] 110.7 97.6 105 Charpy impact strength [kJ/m.sup.2] 37.33 21.51 57 unnotched +23 C. *remaining part up 100 wt.-% are typical additives like antioxidants, carrier etc.

(37) PP is the commercial propylene homopolymer HF955MO of Borealis AG having a melt flow rate MFR2 (230 C.) of 19.5 g/10 min and a melting temperature of 167 C.;

(38) PP-1 is the commercial propylene homopolymer HK060AE of Borealis AG having a melt flow rate MFR2 (230 C.) of 125 g/10 min and a melting temperature of 165 C.;

(39) Carbon fiber is a non-woven fabric comprising 80 wt.-% of carbon fibers and has been produced by needle-punching: The carbon fibers have an average diameter of 7 m.

(40) Glass fibers is a glass fiber having an average diameter of 17 m and is an endless roving before production, about 10 mm length after pelletizing;

(41) ECP1 is the commercial product Engage 8100 of Dow Elastomers (USA), which is an ethylene-1-octene copolymer having a density of 0.870 g/cm.sup.3, a melt flow rate MFR.sub.2 (190 C.) of 1.0 g/10 min and a 1-octene content of 25 wt.-%;

(42) ECP2 is the commercial product Queo 8230 of Borealis Plastomers, which is an ethylene-1-octene copolymer having a density of 0.882 g/cm.sup.3, a melt flow rate MFR.sub.2 (190 C.) of 30 g/10 min and a 1-octene content of 17 wt.-%;

(43) PMP is the ethylene polypropylene copolymer (functionalized with maleic anhydride)

(44) TSPP3598 GB of BYK Co. Ltd, Germany, having a MFI (170 C.) of 71 g/10 min and a maleic anhydride content of 2.2-2.4 wt.-% wherein further the ethylene polypropylene copolymer has an ethylene content of 5.6 wt.-%;

(45) PMP2 is the polypropylene (functionalized with maleic anhydride) TPPP8112 FA of BYK Co. Ltd, Germany, having a MFR.sub.2 (190 C.; 2.16 kg) of more than 80 g/10 min and a maleic anhydride content of 1.4 wt.-%;

(46) PMP2a is the polypropylene (functionalized with maleic anhydride) TPPP9012 GA of BYK Co. Ltd, Germany, having a MFR.sub.2 (190 C.; 2.16 kg) of 50-110 g/10 min and a maleic anhydride content of more than 0.9%.

(47) It can be gathered from table 1 that the inventive example IE1 comprising carbon fibers in combination with a specific polar modified polypropylene in a polypropylene matrix has well-balanced mechanical properties such as stiffness and impact, at reduced density. Moreover, compared to the comparative examples CE1 and CE2, using a polar modified polypropylene (PMP) that is typically used as coupling agents in polypropylenes, a significant improvement in the impact related properties is obtained, but keeping a comparable modulus value.