CA2094614A1 - Composite sheet moldable material - Google Patents
Composite sheet moldable materialInfo
- Publication number
- CA2094614A1 CA2094614A1 CA 2094614 CA2094614A CA2094614A1 CA 2094614 A1 CA2094614 A1 CA 2094614A1 CA 2094614 CA2094614 CA 2094614 CA 2094614 A CA2094614 A CA 2094614A CA 2094614 A1 CA2094614 A1 CA 2094614A1
- Authority
- CA
- Canada
- Prior art keywords
- fibers
- weight
- composite
- pet
- matrix
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000002131 composite material Substances 0.000 title claims description 36
- 239000000463 material Substances 0.000 title description 2
- 239000000835 fiber Substances 0.000 claims abstract description 54
- 229920000139 polyethylene terephthalate Polymers 0.000 claims description 40
- 239000005020 polyethylene terephthalate Substances 0.000 claims description 40
- 239000011159 matrix material Substances 0.000 claims description 19
- 239000000203 mixture Substances 0.000 claims description 17
- 239000012783 reinforcing fiber Substances 0.000 claims description 16
- 238000000465 moulding Methods 0.000 claims description 13
- 229920001577 copolymer Polymers 0.000 claims description 12
- -1 polyethylene terephthalate Polymers 0.000 claims description 11
- 238000005452 bending Methods 0.000 claims description 9
- 238000002844 melting Methods 0.000 claims description 6
- 230000008018 melting Effects 0.000 claims description 6
- 239000011347 resin Substances 0.000 claims description 4
- 229920005989 resin Polymers 0.000 claims description 4
- 239000004698 Polyethylene Substances 0.000 claims description 2
- 229920000573 polyethylene Polymers 0.000 claims description 2
- LZDKZFUFMNSQCJ-UHFFFAOYSA-N 1,2-diethoxyethane Chemical compound CCOCCOCC LZDKZFUFMNSQCJ-UHFFFAOYSA-N 0.000 claims 2
- 229920000728 polyester Polymers 0.000 abstract description 7
- 230000000704 physical effect Effects 0.000 abstract 1
- 229920001169 thermoplastic Polymers 0.000 abstract 1
- 239000004416 thermosoftening plastic Substances 0.000 abstract 1
- 239000011230 binding agent Substances 0.000 description 17
- 238000000034 method Methods 0.000 description 16
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 description 12
- 229920001519 homopolymer Polymers 0.000 description 6
- 239000004743 Polypropylene Substances 0.000 description 4
- 230000015556 catabolic process Effects 0.000 description 4
- 238000006731 degradation reaction Methods 0.000 description 4
- 239000011521 glass Substances 0.000 description 4
- 239000003365 glass fiber Substances 0.000 description 4
- 229920003223 poly(pyromellitimide-1,4-diphenyl ether) Polymers 0.000 description 4
- 229920001155 polypropylene Polymers 0.000 description 4
- 230000002787 reinforcement Effects 0.000 description 4
- 238000002156 mixing Methods 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000009960 carding Methods 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000001746 injection moulding Methods 0.000 description 2
- 238000013001 point bending Methods 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 230000003014 reinforcing effect Effects 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 241000288673 Chiroptera Species 0.000 description 1
- DTQVDTLACAAQTR-UHFFFAOYSA-N Trifluoroacetic acid Chemical compound OC(=O)C(F)(F)F DTQVDTLACAAQTR-UHFFFAOYSA-N 0.000 description 1
- 230000003213 activating effect Effects 0.000 description 1
- 239000003963 antioxidant agent Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000012668 chain scission Methods 0.000 description 1
- 238000007596 consolidation process Methods 0.000 description 1
- 229920006240 drawn fiber Polymers 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000011152 fibreglass Substances 0.000 description 1
- 239000002223 garnet Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 150000002334 glycols Chemical class 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000003301 hydrolyzing effect Effects 0.000 description 1
- QQVIHTHCMHWDBS-UHFFFAOYSA-N isophthalic acid Chemical class OC(=O)C1=CC=CC(C(O)=O)=C1 QQVIHTHCMHWDBS-UHFFFAOYSA-N 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 125000000325 methylidene group Chemical group [H]C([H])=* 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 229920002959 polymer blend Polymers 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 230000003746 surface roughness Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 239000004753 textile Substances 0.000 description 1
- 238000007666 vacuum forming Methods 0.000 description 1
- 230000004580 weight loss Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/04—Reinforcing macromolecular compounds with loose or coherent fibrous material
- C08J5/046—Reinforcing macromolecular compounds with loose or coherent fibrous material with synthetic macromolecular fibrous material
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/04—Reinforcing macromolecular compounds with loose or coherent fibrous material
-
- D—TEXTILES; PAPER
- D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
- D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
- D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
- D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
- D04H1/54—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
- C08J2367/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
- Y10T442/60—Nonwoven fabric [i.e., nonwoven strand or fiber material]
- Y10T442/659—Including an additional nonwoven fabric
- Y10T442/671—Multiple nonwoven fabric layers composed of the same polymeric strand or fiber material
Abstract
Thermoplastic polyester fiber reinforced polyester panels which have extremely smooth and paintable surface and which can be deformed when hot to conform to a molded useful article without substantial loss in molecular weight or physical properties such as strength.
Description
WO9~/07898 2 0 ~ 1 6 ~ ~ PCT/~'S91/07782 TITLE
Composite Sheet Moldable Material Backqround of the Invention This invention relates to fiber reinforced resin matxices and more particularly it relates to polyester fiber as the reinforcing fiber for a polyethylene terephthalate resin matrix. Plastic shells reinforced with fiber glass are used for certain applications such as automotive body parts or housings for tools or electronic equipment. The reinforcing fibers such as glass are cast or encapsulated in a matrix such as polyethylene terephthalate (PET) or polypropylene (PP).
There are several methods which are usually employed to form these structures. One such method uses injection molding of PET blended with a very short cut length of glass fibers. A
second method uses a polyester in a solvent base which is sprayed into a mold, then laid up with glass, and then sprayed with another layer of polyester and a cross-lin~ing agent to make this structure permanently solid. Yet in another method ; preform sheet is produced by consolidating (technically pre-consolidating) a mixture of glass fiber and PET or PP or by extrucling PET or PP to a glass fiber mat. The sheet thus obtained is then vacuum formed or thermo-formed in a mold in a male female mold.
In all these techniques the PET has to be heated above its melting point to obtain conformance with the mold shape. Most homopolymer PET degrades very rapidly due to oxidation and hydrolytic degradation and looses it molecular weight and strength at this high temperature.
.
. . :,~ !, :. , . ' i:
W092/07898 2 0 ~ ~ 6 ~L~ PCT/US91/07782 Hence, in all the above techniques, the moisture or oxygen has to be excluded from coming in contact with the hot polymer blend. This requires elaborate injection molding or blanketing or drying equipment or the use of antioxidants in the polymer.
Summary of Invention This invention takes advantage of two fundamental properties of polyesters, namely, the degradation is most rapid at the melting point of PET (240 to 250C) in the absence of an inert media gas as is the case i~ most molding operations. It is also known that this degradation or strength loss is due to reduction in molecular weight caused by Chain Scission which declines rapidly with the reduction in temperature. The second property is the depression of the melting point of PET when copolymerized with isophthalates or glycols such as diethylene glycol (DEG). Surprisingly, this combination gives a copolymer PET matrix which can be reinforced with homopolymers PET fibers and neither the matrix nor the reinforcing fibers degrade significantly because the matrix can be melted and reconsolidated at lower temperatures.
Thi`s invention involves a combination of matrix (binder) and reinforcing fibers such that the molding or the pre-consolidation temperature is low enough (220C) to accomplish molding without appreciable degradation of the matrix or the reinforcement. Specifically, when a composite of homopolymer PET matrix reinforced with glass fibers was molded, it had to be consolidated-at 270C.
The glass remained intact but the polyester degraded from an intrinsic viscosity (I.V.) of 0.65 (20 LRV) to I.V. of 0.53 (13.5 LRV) and with this :. . : :: : , . . ;, :
,: : . ; :;. . : ~ : ::: .. :.: .. , .: : :.: : ,:
. :.:. :: , . :, ,, , .. : : :: . ,~ ., :, . . ... .. . ..
W092/07898 2 0 9 ~ PCT/~'S91/07782 ;
there was an unacceptable loss of molecular weight and strength. However, when PET was used as the reinforcing fiber and a copolymer of PET and 12.5 mole % DEG was used as the matrix and consolidated at 220C, the matrix I.V. went from 0.667 to 0.627 retaining its strength and the PET reinforcing fiber I.V. went from 0.635 to 0.62 retaining its strength and giving a composite of very good 10 strength (7.9 x 103 psi) and modulus (.713 x 106 psi). Thus, the present invention specifies using copolymer PET fibers (with relatively low melt temperatures) as the matrix forming component so that molding could be carried out at temperatures 15 below the temperature at which PET suffers ~-significant molecular weight loss and accompanying loss of strength and stiffness.
Since both the binder matrix and the reinforcing polymers are both spinnable as fibers, they can be spun and blended, and air laid, carded, or wet laid as any other fibers and pre-consolidated into sheets which can then be heated and formed (molded) into useful shapes in a typical male/female press or a vacuum forming operation. The fiber blend as a mat can also be used, without preconsolidation, in a closed mold to form a useful article by subjecting the mold and its content to a complete heating and cooling cycle.
A further surprising advantage of this combination is that the surface finish of these composites is extremely smooth and it copies or surpasses the surface roughness of the mold. This is a result of the fact that unlike glass reinforcements PET conforms and retains the new configuration at low molding temperatures (about 220C).
:, ., . . , . ,,, . , . , . . : ~ ,:, :: : ,,, . . : : . , . :, : , ,:
,: :
,:,: , .
~ .: , . .
W O 92/07898 2 ~ 9 ~ P ~ /US91/07782 Brief DescriPtion of the Drawinq Fig. 1 is a photograph of the ~ension Index for standard calibration surface.
Detailed Description of the Preferred Embodlment The composite fiber mat is formed on a conventional card and then needle punched for structural integrity. The ratio of reinforcing fibers and matrix forming fibers in the mat to ~ 3 binder fibers in the mat could be adjusted by changing the feed rate of corresponding fibers.
Though there is a preferred orientation in a carded mat, the extent of such orientation is not very significant and, for all practical purposes, the mat is considered as quasi-isotropic.
The reinforcing fibers used in the present invention consists of homopolymer staple fibers of 1.5 to 7 dpf (preferably 5.5 dpf) and cut length of l" to 2.5" (preferably 1.5" long). These fibers usually have moderate crimp. Fibers of different geometry and differing number of holes (solid fibers to 4-hole fibers) were uséd in the present invention. These fibers are surface treated by a finish for better handling during carding or wet laying.
The binder (or matrix forming) ~ibers are lower melting copolymer fibers usually, but not exclusively crimped, of cut length 1" to 2.5" and 1.5 to 3.5 dpf. Binder fiber content in the mat is kept between 50% to 75% by weight. Better properties are observed when the binder fraction is 70%.
Several needle-punched pre-form mats are stacked to produce necessary thickness to make composite parts. It is found that better surface . .: : .. - . : : ::, ,: ,: : . . : :. . i W092/07898 2 ~ 9 ~ f3 ~ ~ PCTt~'S91/0778~
properties are obtained when a thin layer of binder fiber is placed on the outside of the fiber mat stack to be molded.
Blendinq Procedure For large quantities of fiber blend, the ;
cutter blender technique is used in which blending is done along with cutting on a Lumnus cutter. The reinforcing fibers and binder fibers are passed through two cutter reels, each adjusted to produce staple fibers of required lengths, running at different speeds adjusted to obtain the required weight conkribution of reinforcing and binder fibers in the blend. The cut fibers are collected in the same container. The blend thus obtained is reasonably uniform; however, by using a blender better uniformity is obtained.
Garnetina and Needle Punchinq Fiber blend obtained by the above-mentioned techniques are passed through a Garnet/Card and then through a needle puncher to form 22" wide 1/8" thick bats.
Moldinq Procedure About 80 grams of flber mat (usually 5-7 layers) was stacked in a 7x7" picture frame mold coated with silicone. No attempt was made to dry the fiber blend prior to transferring fiber blend into the mold. The mold unit was then placed in a hydraulic press (Pasadena Hydraulic Press model B-230, 50 T capacity) whose plates were kept at a temperature 15 to 25C above the melting point of the binder fibers. The mold was kept between the plates under a 10 ton load for 15 minutes. The heat was then cut off and cold water was passed W O 92/07898 2 0 ~ PC~r/~'S91/07782 through the assembly and the mold was allowed to cool to a temperature below 100C. The mold was then taken out of the press and the composite plaque was pushed out of the mold using a 3 ton Arbor press. Specimens were cut out from the plaques for tensile and blending measurements.
These composites are extremely tough with high resilience and good surface characteristics.
Average blending modulus and strength are calculated from several specimens. ; -Test Method for Surface Smoothness A Tension meter, manufactured by PPG ~ -Industries, is used to characterize the surface smoothness (or roughness) of composites. The Tension instrument is first calibrated on a smooth and even standard surface supplied by PPG. The instrument is placed over the surface and a Poloroid picture is taken by activating the flash.
The picture thus obtained has 12 regions or rectangles. The rectangle designated by number 9 has widely spaced lines but the one corresponds to number 20 contain lines which are closely packed.
For the standard smooth surface, the lines in the rectangle 20 do not touch each other and are distinctly visible. These lines in the picture are images of a grid reflected on the surface of the composite, thus the finer the visible lines in the picture the better the surface. The Tension index corresponds to the number assigned to the rectangle containing the closest packed lines which do not touch each other. Thus, the Tension index for the calibration surface is 20.
- After calibration, the instrument is placed over the composite sample and a picture is taken, and the Tension Index is identified by W092/0789~ 2 ~ ~ 4 fi 1~ PCT/~S9l/0778 reading the number assigned to the rectangle ;
containing the finest and closest pac~ed lines which do not touch each other.
Test for Determininq Bindinq Modulus and Yield Strength ASTM D790-71 is the standard used to determine binding modulus and yield strength wherein a four point bending test is applied to evaluate bending modulus and yield strength of PET/PET composites. Samples used are of 1 inch width and usually about 1/~ inch thickness. The bending modulus is evaluated from the slope of the tangent of the initial part of the force-deflection curve. The yield strength is evaluated by finding the force required for a significant ~ield of the specimen under the four point bending condition and evaluating the maximum stress using the linear theory of bending.
Test for Determinina Intrinsic Viscosity (I~) The intrinsic viscosity of PET or its copolymer derivatives were determined by measuring the solution efflux time in a calibrated Ostwald-Cannon-Fens~e modified viscometer using a 0.32% solution of PET dissolved in a mixture of 25 parts of tri-fluroacetic acid and 75 parts of methylene chlQride.
Example l We obtained a unlform blend by carding crimped 5.5 dpf PET homopolymer fibers (T-374, 4~hole round) and crimped 3.75 dpf PET copolymer fibers tT-171, PET, DEG with 12.5% DEG) both 1.5"
long, and needle-punching the nonwoven mat. The blend ratio (reinforcing fiber/binder fiber) was . .
WO 92/07898 PCI/US9~/0778' 2 ~
30/70 by weight. The fibers had a standard textile lubricant antistat for processing on dry or wet laid equipment. The intake of reinforcing fibers 5 and binder fibers is controlled to obtain the mat of required blend ratib. The dry mat weight was approximately 0.08 lbs./sq. ft. This mat was needle punched to a thickness of 1/8".
The nonwoven sheets are then stacked to 10 form 7x7" batt of weight approximately 0.6 lbs./sq.
ft. The mat is transferred to a 7x7 picture frame mold coated with standard mold release (silica) ~ -agent. The mold is closed and placed between the platens of a hydraulic press. The platens were 15 kept at a temperature of 230C. The mold and its contents are kept between the platens at a pressure of (15T/7x7") for approximately 15 minutes before water is allowed to circulate through the platens to cool the mold and its contents to a temperature to 80C. Cooling process is started ~hen the evidence of flash is sighted, if it happened earlier than 15 minutes. The composite plaque is `
then removed from the mold and is tested for its 25 strength, modulus, and surface smoothness. The T-374/171 composite has a bending modulus of :
720,000 psi and yield strength 5,400 psi in one direction and 75,000 psi in the other. The surface smoothness under (Tension index) was 16. By using 30 "KAPTON" sheets on both sides of the mat before molding and removing these sheets after molding, the surface smoothness was improved. The Tension index for composites formed using a Class-A mold or by using "KAPTON" sheets was 18.
Example 2 The procedure is identical to Example l using a composite preform layer composed of ., : . , ;' ', , 1 , " ., . , . ' ' ' ,, ; ~ , , :: :,. .. . . . . . ..
W092/07898 2 a ~ PCT/~591/07782 ~ g :~
homopolymer PET reinforcing fibers and isothlate copolymer binder fibers (T-374 and D-262 fibers with 5.5 and 3 dpf, respectively; D-262 contains 30% of polyethylene isothalate). Molding temperature (235C) and molding time (20 minutes) are slightly higher compared to DEG copolymer binder fiber composites for 30/70 reinforcement/binder blend ratio. Isothalate composites provided a modulus of 700,000 psi and yield strength of 7,500 psi. Surface properties are excellent. The Tension Index for composites, without the use of "KAPTON" sheets was 15.
Exam~le 3 The procedure is identical to Example 1 using a co~posite preform layer composed of drawn P~T as reinforcements (T-374) and undrawn PET
(T-611, 6 dpf) as binder fibers (40/60 by weight).
Molding is carried out at carefully controlled temperatures sufficient enough to melt the undrawn fibers while leaving the drawn fibers mostly intact. The Tension Index for the surface was 12, T-374/611 composites developed a bending modulus of 500,000 psi and having strength of 11,000 psi.
Exam~le 4 The procedure is identical to Example 1 using nonwoven sheets composed of PET reinforcing fibers (T-37A) and isothala~e (2GI) sheath-core copolymer binder fibers (D-269, PET/2GI/PET 50//50, `
` dpf 4.0) in 30/70 ratio by weight. The molding temperature was slightly higher, 245C. T-374/171 composites developed a modulus of 650,000 psi and strength 9,000 psi. The Tension Index for composites molded without using "KAPTON" sheets was 12.
- . , , - . ............ . : , . i " ,. . . ... ...
:, ~ . ., ;,, . . . :
. .
2 0 ~ ~ 6 1 ~ 1 Q fr~
Example 5 The procedure is identical to Example 1 using a composite preform layer composed of PET
fibers (T-372 solid round, dpf 1.5) and PET
copolymer fibers (T-171) in 40/60 blend ratio. The bending modulus of resulting composite was 550,000 psi, and the bending strength was 11,000 psi.
Tension Index of the surface was 13.
Example 6 The procedure is identical to Example 1 using a composite fiber batt composed of high IV
0-9, mid shrinkage, industrial PET yarn (uncrimped, 1.5" cut length) and a needle punched fiber blend of T-374 and 171 at 30/70 weight ratio. The preform fiber batt is obtained by stacking alternate layers of industrial yarn and T-374/171 fiber blend at 25/75 weight ratio so that both sides of the stack have T-171 fiber layer. The bending modulus of the resulting composite sheets was 900,000 psi and strength 9,500 psi.
, ..... ,. .. ., .,. .. , . .. ... ~
, ,:,: : . , .,:.,.
Composite Sheet Moldable Material Backqround of the Invention This invention relates to fiber reinforced resin matxices and more particularly it relates to polyester fiber as the reinforcing fiber for a polyethylene terephthalate resin matrix. Plastic shells reinforced with fiber glass are used for certain applications such as automotive body parts or housings for tools or electronic equipment. The reinforcing fibers such as glass are cast or encapsulated in a matrix such as polyethylene terephthalate (PET) or polypropylene (PP).
There are several methods which are usually employed to form these structures. One such method uses injection molding of PET blended with a very short cut length of glass fibers. A
second method uses a polyester in a solvent base which is sprayed into a mold, then laid up with glass, and then sprayed with another layer of polyester and a cross-lin~ing agent to make this structure permanently solid. Yet in another method ; preform sheet is produced by consolidating (technically pre-consolidating) a mixture of glass fiber and PET or PP or by extrucling PET or PP to a glass fiber mat. The sheet thus obtained is then vacuum formed or thermo-formed in a mold in a male female mold.
In all these techniques the PET has to be heated above its melting point to obtain conformance with the mold shape. Most homopolymer PET degrades very rapidly due to oxidation and hydrolytic degradation and looses it molecular weight and strength at this high temperature.
.
. . :,~ !, :. , . ' i:
W092/07898 2 0 ~ ~ 6 ~L~ PCT/US91/07782 Hence, in all the above techniques, the moisture or oxygen has to be excluded from coming in contact with the hot polymer blend. This requires elaborate injection molding or blanketing or drying equipment or the use of antioxidants in the polymer.
Summary of Invention This invention takes advantage of two fundamental properties of polyesters, namely, the degradation is most rapid at the melting point of PET (240 to 250C) in the absence of an inert media gas as is the case i~ most molding operations. It is also known that this degradation or strength loss is due to reduction in molecular weight caused by Chain Scission which declines rapidly with the reduction in temperature. The second property is the depression of the melting point of PET when copolymerized with isophthalates or glycols such as diethylene glycol (DEG). Surprisingly, this combination gives a copolymer PET matrix which can be reinforced with homopolymers PET fibers and neither the matrix nor the reinforcing fibers degrade significantly because the matrix can be melted and reconsolidated at lower temperatures.
Thi`s invention involves a combination of matrix (binder) and reinforcing fibers such that the molding or the pre-consolidation temperature is low enough (220C) to accomplish molding without appreciable degradation of the matrix or the reinforcement. Specifically, when a composite of homopolymer PET matrix reinforced with glass fibers was molded, it had to be consolidated-at 270C.
The glass remained intact but the polyester degraded from an intrinsic viscosity (I.V.) of 0.65 (20 LRV) to I.V. of 0.53 (13.5 LRV) and with this :. . : :: : , . . ;, :
,: : . ; :;. . : ~ : ::: .. :.: .. , .: : :.: : ,:
. :.:. :: , . :, ,, , .. : : :: . ,~ ., :, . . ... .. . ..
W092/07898 2 0 9 ~ PCT/~'S91/07782 ;
there was an unacceptable loss of molecular weight and strength. However, when PET was used as the reinforcing fiber and a copolymer of PET and 12.5 mole % DEG was used as the matrix and consolidated at 220C, the matrix I.V. went from 0.667 to 0.627 retaining its strength and the PET reinforcing fiber I.V. went from 0.635 to 0.62 retaining its strength and giving a composite of very good 10 strength (7.9 x 103 psi) and modulus (.713 x 106 psi). Thus, the present invention specifies using copolymer PET fibers (with relatively low melt temperatures) as the matrix forming component so that molding could be carried out at temperatures 15 below the temperature at which PET suffers ~-significant molecular weight loss and accompanying loss of strength and stiffness.
Since both the binder matrix and the reinforcing polymers are both spinnable as fibers, they can be spun and blended, and air laid, carded, or wet laid as any other fibers and pre-consolidated into sheets which can then be heated and formed (molded) into useful shapes in a typical male/female press or a vacuum forming operation. The fiber blend as a mat can also be used, without preconsolidation, in a closed mold to form a useful article by subjecting the mold and its content to a complete heating and cooling cycle.
A further surprising advantage of this combination is that the surface finish of these composites is extremely smooth and it copies or surpasses the surface roughness of the mold. This is a result of the fact that unlike glass reinforcements PET conforms and retains the new configuration at low molding temperatures (about 220C).
:, ., . . , . ,,, . , . , . . : ~ ,:, :: : ,,, . . : : . , . :, : , ,:
,: :
,:,: , .
~ .: , . .
W O 92/07898 2 ~ 9 ~ P ~ /US91/07782 Brief DescriPtion of the Drawinq Fig. 1 is a photograph of the ~ension Index for standard calibration surface.
Detailed Description of the Preferred Embodlment The composite fiber mat is formed on a conventional card and then needle punched for structural integrity. The ratio of reinforcing fibers and matrix forming fibers in the mat to ~ 3 binder fibers in the mat could be adjusted by changing the feed rate of corresponding fibers.
Though there is a preferred orientation in a carded mat, the extent of such orientation is not very significant and, for all practical purposes, the mat is considered as quasi-isotropic.
The reinforcing fibers used in the present invention consists of homopolymer staple fibers of 1.5 to 7 dpf (preferably 5.5 dpf) and cut length of l" to 2.5" (preferably 1.5" long). These fibers usually have moderate crimp. Fibers of different geometry and differing number of holes (solid fibers to 4-hole fibers) were uséd in the present invention. These fibers are surface treated by a finish for better handling during carding or wet laying.
The binder (or matrix forming) ~ibers are lower melting copolymer fibers usually, but not exclusively crimped, of cut length 1" to 2.5" and 1.5 to 3.5 dpf. Binder fiber content in the mat is kept between 50% to 75% by weight. Better properties are observed when the binder fraction is 70%.
Several needle-punched pre-form mats are stacked to produce necessary thickness to make composite parts. It is found that better surface . .: : .. - . : : ::, ,: ,: : . . : :. . i W092/07898 2 ~ 9 ~ f3 ~ ~ PCTt~'S91/0778~
properties are obtained when a thin layer of binder fiber is placed on the outside of the fiber mat stack to be molded.
Blendinq Procedure For large quantities of fiber blend, the ;
cutter blender technique is used in which blending is done along with cutting on a Lumnus cutter. The reinforcing fibers and binder fibers are passed through two cutter reels, each adjusted to produce staple fibers of required lengths, running at different speeds adjusted to obtain the required weight conkribution of reinforcing and binder fibers in the blend. The cut fibers are collected in the same container. The blend thus obtained is reasonably uniform; however, by using a blender better uniformity is obtained.
Garnetina and Needle Punchinq Fiber blend obtained by the above-mentioned techniques are passed through a Garnet/Card and then through a needle puncher to form 22" wide 1/8" thick bats.
Moldinq Procedure About 80 grams of flber mat (usually 5-7 layers) was stacked in a 7x7" picture frame mold coated with silicone. No attempt was made to dry the fiber blend prior to transferring fiber blend into the mold. The mold unit was then placed in a hydraulic press (Pasadena Hydraulic Press model B-230, 50 T capacity) whose plates were kept at a temperature 15 to 25C above the melting point of the binder fibers. The mold was kept between the plates under a 10 ton load for 15 minutes. The heat was then cut off and cold water was passed W O 92/07898 2 0 ~ PC~r/~'S91/07782 through the assembly and the mold was allowed to cool to a temperature below 100C. The mold was then taken out of the press and the composite plaque was pushed out of the mold using a 3 ton Arbor press. Specimens were cut out from the plaques for tensile and blending measurements.
These composites are extremely tough with high resilience and good surface characteristics.
Average blending modulus and strength are calculated from several specimens. ; -Test Method for Surface Smoothness A Tension meter, manufactured by PPG ~ -Industries, is used to characterize the surface smoothness (or roughness) of composites. The Tension instrument is first calibrated on a smooth and even standard surface supplied by PPG. The instrument is placed over the surface and a Poloroid picture is taken by activating the flash.
The picture thus obtained has 12 regions or rectangles. The rectangle designated by number 9 has widely spaced lines but the one corresponds to number 20 contain lines which are closely packed.
For the standard smooth surface, the lines in the rectangle 20 do not touch each other and are distinctly visible. These lines in the picture are images of a grid reflected on the surface of the composite, thus the finer the visible lines in the picture the better the surface. The Tension index corresponds to the number assigned to the rectangle containing the closest packed lines which do not touch each other. Thus, the Tension index for the calibration surface is 20.
- After calibration, the instrument is placed over the composite sample and a picture is taken, and the Tension Index is identified by W092/0789~ 2 ~ ~ 4 fi 1~ PCT/~S9l/0778 reading the number assigned to the rectangle ;
containing the finest and closest pac~ed lines which do not touch each other.
Test for Determininq Bindinq Modulus and Yield Strength ASTM D790-71 is the standard used to determine binding modulus and yield strength wherein a four point bending test is applied to evaluate bending modulus and yield strength of PET/PET composites. Samples used are of 1 inch width and usually about 1/~ inch thickness. The bending modulus is evaluated from the slope of the tangent of the initial part of the force-deflection curve. The yield strength is evaluated by finding the force required for a significant ~ield of the specimen under the four point bending condition and evaluating the maximum stress using the linear theory of bending.
Test for Determinina Intrinsic Viscosity (I~) The intrinsic viscosity of PET or its copolymer derivatives were determined by measuring the solution efflux time in a calibrated Ostwald-Cannon-Fens~e modified viscometer using a 0.32% solution of PET dissolved in a mixture of 25 parts of tri-fluroacetic acid and 75 parts of methylene chlQride.
Example l We obtained a unlform blend by carding crimped 5.5 dpf PET homopolymer fibers (T-374, 4~hole round) and crimped 3.75 dpf PET copolymer fibers tT-171, PET, DEG with 12.5% DEG) both 1.5"
long, and needle-punching the nonwoven mat. The blend ratio (reinforcing fiber/binder fiber) was . .
WO 92/07898 PCI/US9~/0778' 2 ~
30/70 by weight. The fibers had a standard textile lubricant antistat for processing on dry or wet laid equipment. The intake of reinforcing fibers 5 and binder fibers is controlled to obtain the mat of required blend ratib. The dry mat weight was approximately 0.08 lbs./sq. ft. This mat was needle punched to a thickness of 1/8".
The nonwoven sheets are then stacked to 10 form 7x7" batt of weight approximately 0.6 lbs./sq.
ft. The mat is transferred to a 7x7 picture frame mold coated with standard mold release (silica) ~ -agent. The mold is closed and placed between the platens of a hydraulic press. The platens were 15 kept at a temperature of 230C. The mold and its contents are kept between the platens at a pressure of (15T/7x7") for approximately 15 minutes before water is allowed to circulate through the platens to cool the mold and its contents to a temperature to 80C. Cooling process is started ~hen the evidence of flash is sighted, if it happened earlier than 15 minutes. The composite plaque is `
then removed from the mold and is tested for its 25 strength, modulus, and surface smoothness. The T-374/171 composite has a bending modulus of :
720,000 psi and yield strength 5,400 psi in one direction and 75,000 psi in the other. The surface smoothness under (Tension index) was 16. By using 30 "KAPTON" sheets on both sides of the mat before molding and removing these sheets after molding, the surface smoothness was improved. The Tension index for composites formed using a Class-A mold or by using "KAPTON" sheets was 18.
Example 2 The procedure is identical to Example l using a composite preform layer composed of ., : . , ;' ', , 1 , " ., . , . ' ' ' ,, ; ~ , , :: :,. .. . . . . . ..
W092/07898 2 a ~ PCT/~591/07782 ~ g :~
homopolymer PET reinforcing fibers and isothlate copolymer binder fibers (T-374 and D-262 fibers with 5.5 and 3 dpf, respectively; D-262 contains 30% of polyethylene isothalate). Molding temperature (235C) and molding time (20 minutes) are slightly higher compared to DEG copolymer binder fiber composites for 30/70 reinforcement/binder blend ratio. Isothalate composites provided a modulus of 700,000 psi and yield strength of 7,500 psi. Surface properties are excellent. The Tension Index for composites, without the use of "KAPTON" sheets was 15.
Exam~le 3 The procedure is identical to Example 1 using a co~posite preform layer composed of drawn P~T as reinforcements (T-374) and undrawn PET
(T-611, 6 dpf) as binder fibers (40/60 by weight).
Molding is carried out at carefully controlled temperatures sufficient enough to melt the undrawn fibers while leaving the drawn fibers mostly intact. The Tension Index for the surface was 12, T-374/611 composites developed a bending modulus of 500,000 psi and having strength of 11,000 psi.
Exam~le 4 The procedure is identical to Example 1 using nonwoven sheets composed of PET reinforcing fibers (T-37A) and isothala~e (2GI) sheath-core copolymer binder fibers (D-269, PET/2GI/PET 50//50, `
` dpf 4.0) in 30/70 ratio by weight. The molding temperature was slightly higher, 245C. T-374/171 composites developed a modulus of 650,000 psi and strength 9,000 psi. The Tension Index for composites molded without using "KAPTON" sheets was 12.
- . , , - . ............ . : , . i " ,. . . ... ...
:, ~ . ., ;,, . . . :
. .
2 0 ~ ~ 6 1 ~ 1 Q fr~
Example 5 The procedure is identical to Example 1 using a composite preform layer composed of PET
fibers (T-372 solid round, dpf 1.5) and PET
copolymer fibers (T-171) in 40/60 blend ratio. The bending modulus of resulting composite was 550,000 psi, and the bending strength was 11,000 psi.
Tension Index of the surface was 13.
Example 6 The procedure is identical to Example 1 using a composite fiber batt composed of high IV
0-9, mid shrinkage, industrial PET yarn (uncrimped, 1.5" cut length) and a needle punched fiber blend of T-374 and 171 at 30/70 weight ratio. The preform fiber batt is obtained by stacking alternate layers of industrial yarn and T-374/171 fiber blend at 25/75 weight ratio so that both sides of the stack have T-171 fiber layer. The bending modulus of the resulting composite sheets was 900,000 psi and strength 9,500 psi.
, ..... ,. .. ., .,. .. , . .. ... ~
, ,:,: : . , .,:.,.
Claims (8)
1. A composite structure formed from a fiber reinforced resin matrix comprising: 30% to 40% by weight of polyethylene terephthalate reinforcing fibers and 60% to 70% by weight of a matrix of a copolymer of polyethylene terephthalate and from about 20 to about 35 mole % diethyl glycol.
2. A composite structure is defined in Claim 1, said composite having a molding temperature between the melting temperatures of reinforcing fibers and the matrix forming fibers.
3. The composite structure of Claim 1 having a Tension Index of between about 12 and about 18.
4. A composite structure formed from a fiber reinforced resin matrix comprising: 30% to 40% by weight of polyethylene terephthalate reinforcing fibers and 60% to 70% by weight of a matrix of a copolymer of 70 weight % polyethylene terephthalate and 25 to 30 weight percent polyethylene isothalate.
5. The composite of Claim 4 having a Tension Index of less than about 18.
6. The composite of claim 1 or claim 4 having a Tension Index of from about 12 to about 18.
7. The composite structure of claim 1 or claim 4 having a bending modulus in the range of from about 500,000 to 900,000 psi and a yield strength of from about 5,400 to 11,000 psi.
8. A composite structure molded from a blend of 30% to 40% by weight of polyethylene terephthalate fibers and 60% to 70% by weight of a copolymer of polyethylene terephthalate and about 25 to about 35 mole % diethyl glycol fibers, said copolymers having an intrinsic viscocity loss of less than about 10% units after molding.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US60666490A | 1990-10-31 | 1990-10-31 | |
| US07/606,664 | 1990-10-31 |
Publications (1)
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|---|---|
| CA2094614A1 true CA2094614A1 (en) | 1992-05-01 |
Family
ID=24428941
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2094614 Abandoned CA2094614A1 (en) | 1990-10-31 | 1991-10-29 | Composite sheet moldable material |
Country Status (10)
| Country | Link |
|---|---|
| US (1) | US5286557A (en) |
| EP (1) | EP0555381B1 (en) |
| JP (1) | JPH06502670A (en) |
| KR (1) | KR930702427A (en) |
| AU (1) | AU650311B2 (en) |
| BR (1) | BR9106870A (en) |
| CA (1) | CA2094614A1 (en) |
| DE (1) | DE69109491T2 (en) |
| ES (1) | ES2073278T3 (en) |
| WO (1) | WO1992007898A1 (en) |
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|---|---|---|---|---|
| DE4205464C1 (en) * | 1992-02-22 | 1993-03-04 | Fa. Carl Freudenberg, 6940 Weinheim, De | |
| US5591289A (en) * | 1995-06-29 | 1997-01-07 | Davidson Textron Inc. | Method of making a fibrous headliner by compression molding |
| GB2333741B (en) | 1998-01-30 | 2002-09-04 | Jason Inc | Vehicle headliner and laminate therefor |
| US6010785A (en) * | 1998-02-25 | 2000-01-04 | E. I. Du Pont De Nemours And Company | Cardable blends of dual glass fibers |
| US20040091651A1 (en) * | 2002-11-01 | 2004-05-13 | Mark Rule | Pet copolymer composition with enhanced mechanical properties and stretch ratio, articles made therewith, and methods |
| US20050260371A1 (en) * | 2002-11-01 | 2005-11-24 | Yu Shi | Preform for low natural stretch ratio polymer, container made therewith and methods |
| WO2004113414A1 (en) * | 2003-06-18 | 2004-12-29 | The Coca-Cola Company | Polyester composition for hot fill applications, containers made therewith, and methods |
| US20050221036A1 (en) * | 2004-04-01 | 2005-10-06 | The Coca-Cola Company | Polyester composition with enhanced gas barrier, articles made therewith, and methods |
| AU2004229064A1 (en) * | 2004-11-11 | 2006-05-25 | Woven Image Pty Limited | Single Layer Substrate |
| US7572493B2 (en) * | 2005-05-11 | 2009-08-11 | The Coca-Cola Company | Low IV pet based copolymer preform with enhanced mechanical properties and cycle time, container made therewith and methods |
| US7820257B2 (en) * | 2005-05-11 | 2010-10-26 | The Coca-Cola Company | Preforms for preparing lightweight stretch blow molded PET copolymer containers and methods for making and using same |
| FR3065957B1 (en) * | 2017-05-05 | 2019-07-12 | Roquette Freres | THERMOPLASTIC COMPOSITE |
Family Cites Families (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3369948A (en) * | 1964-11-12 | 1968-02-20 | Du Pont | Method of producing a pile fabric |
| US3499810A (en) * | 1967-05-31 | 1970-03-10 | Du Pont | Method of making a bonded nonwoven web of staple-length filaments |
| US3989788A (en) * | 1973-04-25 | 1976-11-02 | E. I. Du Pont De Nemours And Company | Method of making a bonded non-woven web |
| GB1558401A (en) * | 1976-04-08 | 1980-01-03 | Ici Ltd | Segmentally bonded non woven fabrices |
| US4304817A (en) * | 1979-02-28 | 1981-12-08 | E. I. Dupont De Nemours & Company | Polyester fiberfill blends |
| US4263364A (en) * | 1979-12-14 | 1981-04-21 | Eastman Kodak Company | Stampable reinforced thermoplastic polyester sheets |
| US4418116A (en) * | 1981-11-03 | 1983-11-29 | E. I. Du Pont De Nemours & Co. | Copolyester binder filaments and fibers |
| US4419503A (en) * | 1982-05-24 | 1983-12-06 | Exxon Research & Engineering Co. | Catalytic process for the production of petroleum resins |
| JPS59144611A (en) * | 1983-02-01 | 1984-08-18 | Teijin Ltd | Polyester yarn |
| CA1277188C (en) * | 1984-11-19 | 1990-12-04 | James E. O'connor | Fiber reinforced thermoplastic articles and process for the preparationthereof |
| DD229443A1 (en) * | 1984-12-08 | 1985-11-06 | Engels Chemiefaserwerk Veb | METHOD FOR PRODUCING BINDEFASES FOR LIQUID MATERIAL MANUFACTURING |
| JPS6233899A (en) * | 1985-08-08 | 1987-02-13 | 帝人株式会社 | Base material for honeycomb core and its production |
| EP0310200A3 (en) * | 1987-10-02 | 1990-02-14 | Stamicarbon B.V. | Combinations of filaments having substantially different melting or decomposition points, and use thereof |
| JPH01167370A (en) * | 1987-12-24 | 1989-07-03 | Mitsubishi Rayon Co Ltd | Thermoplastic resin composition |
-
1991
- 1991-10-29 EP EP19920900359 patent/EP0555381B1/en not_active Expired - Lifetime
- 1991-10-29 AU AU90353/91A patent/AU650311B2/en not_active Ceased
- 1991-10-29 JP JP4501253A patent/JPH06502670A/en active Pending
- 1991-10-29 CA CA 2094614 patent/CA2094614A1/en not_active Abandoned
- 1991-10-29 ES ES92900359T patent/ES2073278T3/en not_active Expired - Lifetime
- 1991-10-29 KR KR1019930701305A patent/KR930702427A/en not_active Application Discontinuation
- 1991-10-29 BR BR9106870A patent/BR9106870A/en not_active Application Discontinuation
- 1991-10-29 WO PCT/US1991/007782 patent/WO1992007898A1/en active IP Right Grant
- 1991-10-29 DE DE1991609491 patent/DE69109491T2/en not_active Expired - Fee Related
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1992
- 1992-11-05 US US07/971,152 patent/US5286557A/en not_active Expired - Fee Related
Also Published As
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|---|---|
| BR9106870A (en) | 1994-04-19 |
| JPH06502670A (en) | 1994-03-24 |
| US5286557A (en) | 1994-02-15 |
| EP0555381A1 (en) | 1993-08-18 |
| AU9035391A (en) | 1992-05-26 |
| DE69109491D1 (en) | 1995-06-08 |
| DE69109491T2 (en) | 1995-10-19 |
| KR930702427A (en) | 1993-09-09 |
| ES2073278T3 (en) | 1995-08-01 |
| AU650311B2 (en) | 1994-06-16 |
| EP0555381B1 (en) | 1995-05-03 |
| WO1992007898A1 (en) | 1992-05-14 |
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