Patent Application
20190381727
This application claims priority to European application No. 17156541.9 filed on Feb. 16, 2017, the whole content of this application being incorporated herein by reference for all purposes.
Additive manufacturing technologies, otherwise often referred as 3D printing techniques, including in particular filament fabrication techniques, have rapidly evolved during the past few years, in particular in the field of prototyping, and have gained enormous success because of their well-known advantages in terms of flexibility, accessibility of designs that simply could not be produced physically in any other way, mass customization, tool-less approaches, and sustainability profile.
Additive manufacturing systems are generally used to print or otherwise build 3D parts from digital representations of the 3D parts using one or more additive manufacturing techniques. Examples of commercially available additive manufacturing techniques include extrusion-based techniques, jetting, selective laser sintering, powder/binder jetting, electron-beam melting, and stereolithography processes. For each of these techniques, a digital representation of the 3D part is initially sliced into multiple horizontal layers. For each sliced layer, a tool path is then generated, which provides instructions for the particular additive manufacturing system to print the given layer.
For example, in an extrusion-based additive manufacturing system, a 3D part may be printed from a digital representation of the 3D part in a layer-by-layer manner by extruding a flowable part material. The part material is extruded through an extrusion tip carried by a print head of the system, and is deposited as a sequence of roads on a platen in an x-y plane. The extruded part material fuses to previously deposited part material, and solidifies upon a drop in temperature. The position of the print head relative to the substrate is then incremented along a z-axis (perpendicular to the x-y plane), and the process is then repeated to form a 3D part resembling the digital representation.
A variety of materials, thermoplasts or thermosets, have been proposed, and are already presently supplied under different forms, for use in 3D printing devices, including notably under the form of filaments for use in fused filament additive manufacturing devices.
Within this area, fluoromaterials are attracting increasing attention because of their performances' profile which may cope with requirements for being used in 3D printing processes.
Indeed, fluorinated and fully fluorinated plastomeric materials display high thermal and chemical resistance if compared with non-fluorinated plastics typically used in 3D printing.
Now, fluoropolymers have to be printed at high temperatures, varying between 200° C. and 450° C. Under these conditions, HF and other acid and by-products can be generated by thermal degradation of the fluorinated polymers with any of the possible following drawbacks:
There is hence a need for fluorinated polymers which display the chemical and thermal resistance of fluorinated plastics but with possess improved processing performances, so that they can be melt processed at lower temperature and used in a 3D printer.
On the other side, segmented fluorinated block copolymers are generally known in the art. For instance, notably U.S. Pat. No. 5,605,971 (AUSIMONT SPA) 25 Feb. 1997, U.S. Pat. No. 5,612,419 (AUSIMONT SPA) 18 Mar. 1997, U.S. Pat. No. 6,207,758 (AUSIMONT SPA) 27 Mar. 2001 disclose fluorinated thermoplastic elastomers including plastomeric segment and elastomeric segment, whereas elastomeric segments may be of different types, including e.g. segments including vinylidene fluoride (VDF) recurring units and/or segments including tetrafluoroethylene (TFE) recurring units and whereas plastomeric segment may equally be of different types, such as segments comprising TFE units, segments comprising VDF units, segments comprising ethylene, propylene or isobutylene units, in combination with other units.
The Applicant has now surprisingly found that certain fluorinated thermoplastic elastomers, as below detailed, are such to address and cope the challenging requirements expressed above for being processed through additive manufacturing techniques, thanks to their surprising ability to possess better processability at high shear rate than corresponding fluorinated thermoplasts, which possess similar product profile and hence performances, offering hence advantages in throughput and part design accurate control, containment of degradation, reduction of fumes, and yet delivering parts with outstanding chemical and thermal resistance.
The present invention hence is directed to a method for manufacturing a three-dimensional object [object (3D)] using an additive manufacturing system, comprising:
The fluorinated thermoplastic elastomer [polymer (F-TPE)]
For the purpose of the present invention, the term “elastomeric”, when used in connection with the “block (A)” is hereby intended to denote a polymer chain segment which, when taken alone, is substantially amorphous, that is to say, has a heat of fusion of less than 2.0 J/g, preferably of less than 1.5 J/g, more preferably of less than 1.0 J/g, as measured according to ASTM D3418.
For the purpose of the present invention, the term “thermoplastic”, when used in connection with the “block (B)”, is hereby intended to denote a polymer chain segment which, when taken alone, is semi-crystalline, and possesses a detectable melting point, with an associated heat of fusion of exceeding 10.0 J/g, as measured according to ASTM D3418.
The fluorinated thermoplastic elastomer of the composition (C) of the invention is advantageously a block copolymer, said block copolymer typically having a structure comprising at least one block (A) alternated to at least one block (B), that is to say that said fluorinated thermoplastic elastomer typically comprises, preferably consists of, one or more repeating structures of type (B)-(A)-(B). Generally, the polymer (F-TPE) has a structure of type (B)-(A)-(B), i.e. comprising a central block (A) having two ends, connected at both ends to a side block (B).
The block (A) is often alternatively referred to as soft block (A); the block
(B) is often alternatively referred to as hard block (B).
The term “fluorinated monomer” is hereby intended to denote an ethylenically unsaturated monomer comprising at least one fluorine atom.
The fluorinated monomer may further comprise one or more other halogen atoms (Cl, Br, I).
Any of block(s) (A) and (B) may further comprise recurring units derived from at least one hydrogenated monomer, wherein the term “hydrogenated monomer” is intended to denote an ethylenically unsaturated monomer comprising at least one hydrogen atom and free from fluorine atoms.
The polymer (F-TPE) typically comprises, preferably consists of:
Any of block(s) (AVDF) and (ATFE) may further comprise recurring units derived from at least one hydrogenated monomer, which may be selected from the group consisting of C2-C8 non-fluorinated olefins such as ethylene, propylene or isobutylene.
Should the elastomeric block (A) be a block (AVDF), as above detailed, said block (AVDF) typically consists of a sequence of recurring units comprising, preferably consisting of:
The elastomeric block (A) may further comprise recurring units derived from at least one bis-olefin [bis-olefin (OF)] of formula:
RARB═CRC-T-CRD═RERF
wherein RA, RB, RC, RD, RE and RF, equal to or different from each other, are selected from the group consisting of H, F, Cl, C1-C5 alkyl groups and C1-C5 (per)fluoroalkyl groups, and T is a linear or branched C1-C18 alkylene or cycloalkylene group, optionally comprising one or more than one ethereal oxygen atom, preferably at least partially fluorinated, or a (per)fluoropolyoxyalkylene group.
The bis-olefin (OF) is preferably selected from the group consisting of those of any of formulae (OF-1), (OF-2) and (OF-3):
wherein j is an integer comprised between 2 and 10, preferably between 4 and 8, and R1, R2, R3 and R4, equal to or different from each other, are selected from the group consisting of H, F, C1-C5 alkyl groups and C1-C5 (per)fluoroalkyl groups;
wherein each of A, equal to or different from each other and at each occurrence, is independently selected from the group consisting of H, F and Cl; each of B, equal to or different from each other and at each occurrence, is independently selected from the group consisting of H, F, Cl and ORB, wherein RB is a branched or straight chain alkyl group which may be partially, substantially or completely fluorinated or chlorinated, E is a divalent group having 2 to 10 carbon atoms, optionally fluorinated, which may be inserted with ether linkages; preferably E is a —(CF2)m— group, wherein m is an integer comprised between 3 and 5; a preferred bis-olefin of (OF-2) type is F2C═CF—O—(CF2)5—O—CF═CF2;
wherein E, A and B have the same meaning as defined above, R5, R6 and R7, equal to or different from each other, are selected from the group consisting of H, F, C1-C5 alkyl groups and C1-C5 (per)fluoroalkyl groups.
Should the block (A) consist of a recurring units sequence further comprising recurring units derived from at least one bis-olefin (OF), said sequence typically comprises recurring units derived from the said at least one bis-olefin (OF) in an amount comprised between 0.01% and 1.0% by moles, preferably between 0.03% and 0.5% by moles, more preferably between 0.05% and 0.2% by moles, based on the total moles of recurring units of block (A).
Block (B) may consist of a sequence of recurring units, said sequence comprising:
More specifically, block (B) may be selected from the group consisting of:
According to certain embodiments, the polymer (F-TPE) is a perfluorinated thermoplastic elastomer [polymer (pF-TPE)] comprising:
As said, both block (A) and block (B) of polymer (pF-TPE) consist of sequences of recurring units derived from TFE and recurring units derived from at least one perfluorinated monomer other than TFE. Recurring units derived from one or more than one perfluorinated monomer other than TFE may be present in each of block (A) and block (B). The said perfluorinated monomer(s) other than TFE may be the same in block (A) and block (B) recurring units, or may differ. It is nevertheless generally preferred for block (A) and block (B) to consist of sequences of recurring units derived from TFE and recurring units derived from same perfluorinated monomer(s) other than TFE.
The expression “perfluorinated”, as used herein for characterizing the monomer other than TFE used in block (A) and block (B) is hereby used according to its usual meaning, so as to mean that in said monomer is free from hydrogen atoms and comprises fluorine atoms to saturate valencies.
The said perfluorinated monomer other than TFE is advantageously selected from the group consisting of:
Good results have been obtained for embodiments wherein block (A) consisted of a sequence of recurring units derived from TFE and recurring units derived from one or more than one PAVE, as above detailed, and possibly of a minor amount of recurring units derived from at least one bis-olefin (OF),
and/or wherein block (B) consisted of a sequence of recurring units derived from TFE and recurring units derived from one or more than one PAVE.
The expression “minor amount” when used hereunder for indicating the amount of recurring units derived from a bis-olefin in a block (A) of polymer (pF-TPE) is intended to denote an amount which is one order of magnitude less (e.g. at least 50 times less) than the amount of recurring units derived from the other monomers, i.e. TFE and the perfluorinated monomer other than TFE, so as not to significantly affect the typical thermal stability and chemical resistance performances due to these latter units.
Should the elastomeric block (A) of polymer (pF-TPE) further comprise recurring units derived from at least one bis-olefin (OF), said block (A) typically further comprises recurring units derived from at least one bis-olefin (OF) in an amount comprised between 0.01% and 1.0% by moles, preferably between 0.03% and 0.5% by moles, more preferably between 0.05% and 0.2% by moles, based on the total moles of recurring units constituting said elastomeric block (A).
The weight ratio between blocks (A) and blocks (B) in the fluorinated thermoplastic elastomer is typically comprised between 95:5 and 10:90.
According to certain preferred embodiments, the polymers (F-TPE) comprise a major amount of blocks (A); according to these embodiment's, the polymer (F-TPE) used in the method of the present invention is characterized by a weight ratio between blocks (A) and blocks (B) of 95:5 to 65:35, preferably 90:10 to 70:30.
The polymers (F-TPE) used in the method of the present invention may be manufactured by a manufacturing process comprising the following sequential steps:
The manufacturing process above detailed is preferably carried out in aqueous emulsion polymerization according to methods well known in the art, in the presence of a suitable radical initiator.
The radical initiator is typically selected from the group consisting of:
It is also possible to use organic or inorganic redox systems, such as persulphate ammonium/sodium sulphite, hydrogen peroxide/aminoiminomethansulphinic acid.
In step (a) of the manufacturing process as above detailed, one or more iodinated chain transfer agents are added to the reaction medium, typically of formula RxIn, wherein Rx is a C1-C16, preferably a C1-C8 (per)fluoroalkyl or a (per)fluorochloroalkyl group, and n is 1 or 2. It is also possible to use as chain transfer agents alkali or alkaline-earth metal iodides, as described in U.S. Pat. No. 5,173,553 (AUSIMONT S.P.A.) Dec. 22, 1992. The amount of the chain transfer agent to be added is established depending on the molecular weight which is intended to be obtained and on the effectiveness of the chain transfer agent itself.
In any of steps (a) and (b) of the manufacturing process as above detailed, one or more surfactants may be used, preferably fluorinated surfactants of formula:
Ry—X−M+
Among the most commonly used surfactants, mention can be made of (per)fluoropolyoxyalkylenes terminated with one or more carboxyl groups.
In the manufacturing process, when step (a) is terminated, the reaction is generally discontinued, for instance by cooling, and the residual monomers are removed, for instance by heating the emulsion under stirring. The second polymerization step (b) is then advantageously carried out, feeding the new monomer(s) mixture and adding fresh radical initiator. If necessary, under step (b) of the process for the manufacture of the polymer (F-TPE), one or more further chain transfer agents may be added, which can be selected from the same iodinated chain transfer agents as defined above or from chain transfer agents known in the art for use in the manufacture of fluoropolymers such as, for instance, ketones, esters or aliphatic alcohols having from 3 to 10 carbon atoms, such as acetone, ethylacetate, diethylmalonate, diethylether and isopropyl alcohol; hydrocarbons, such as methane, ethane and butane; chloro(fluoro)carbons, optionally containing hydrogen atoms, such as chloroform and trichlorofluoromethane; bis(alkyl)carbonates wherein the alkyl group has from 1 to 5 carbon atoms, such as bis(ethyl) carbonate and bis(isobutyl) carbonate. When step (b) is completed, the polymer (F-TPE) is generally isolated from the emulsion according to conventional methods, such as by coagulation by addition of electrolytes or by cooling.
Alternatively, the polymerization reaction can be carried out in mass or in suspension, in an organic liquid where a suitable radical initiator is present, according to known techniques. The polymerization temperature and pressure can vary within wide ranges depending on the type of monomers used and based on the other reaction conditions. Step (a) and/or step (b) of process for the manufacture of the polymer (F-TPE) is typically carried out at a temperature of from −20° C. to 150° C.; and/or typically under pressures up to 10 MPa.
The manufacturing process as above detailed is preferably carried out in aqueous emulsion polymerization in the presence of a microemulsion of perfluoropolyoxyalkylenes, as described in U.S. Pat. No. 4,864,006 (AUSIMONT S.P.A.) Sep. 5, 1989, or in the presence of a microemulsion of fluoropolyoxyalkylenes having hydrogenated end groups and/or hydrogenated recurring units, as described in EP 625526 A (AUSIMONT S.P.A.) Nov. 23, 1994.
The Part Material [Composition (C)]
Within the frame of the present invention, the expression “part material” (otherwise referred to as “composition (C)”), as used in connection with the method of the present invention is understood to designate the composition of matter intended to be the constituent material of the three-dimensional object obtained from the said method.
As said the part material (otherwise referred to as “composition (C)”) comprises at least one polymer (F-TPE) as above detailed. One or more than one polymer (F-TPE) may be used in the part material.
The part material may comprise the polymer (F-TPE) as above detailed in combination with other materials/ingredients, or may essentially consist of the said polymer (F-TPE), being understood that minor amounts (e.g. <1% wt on total part material) of components other than the polymer (F-TPE) may be present, without these components substantially affecting the performances and the properties of the polymer (F-TPE).
Composition (C) may hence comprise one or more than one additional polymer materials having thermoplastic behaviour, such as notably one or more than one fluoropolymer.
Further, the composition (C) may comprise one or more than one ingredients, such as those selected from the group consisting of thermal stabilizers, fillers, colouring compounds, plasticizers, curing systems, acid acceptors.
Generally, to the aim of fabricating a coloured three-dimensional object, the composition (C) will comprise one or more than one colouring compound, whose choice is not particularly limited. As used herein, the term “colouring compound” is intended to denote a compound that changes the colour of reflected or transmitted light as the result of wavelength-selective absorption of the electromagnetic radiation.
The colouring compound may be typically selected from the group consisting of organic colouring compounds and inorganic colouring compounds. Mixtures of one or more organic colouring compounds and one or more inorganic colouring compounds may be used in the composition (C) as above detailed. Otherwise, organic colouring compounds or inorganic colouring compounds may be separately used.
The colouring compound may be a luminescent colouring compound [compound (L)] or a non-luminescent colouring compound [compound (N-L)].
For the purpose of the present invention, the term “luminescent colouring compound [compound (L)]” is intended to denote either a fluorescent colouring compound [compound (L-F)] or a phosphorescent colouring compound [compound (L-P)].
The terms “luminescent”, “fluorescent” and “phosphorescent” are used in the present invention according to their usual meanings.
The compound (L) is usually able to re-emit the absorbed electromagnetic radiation from an excited state to a ground state. In particular, the compound (L-F) usually absorbs electromagnetic radiation in the ultraviolet (UV) region and re-emit it in the visible region of the electromagnetic spectrum.
For the purpose of the present invention, the term “non-luminescent colouring compound [compound (N-L)]” is intended to denote a non-luminescent colouring compound which selectively absorbs electromagnetic radiation in the visible region of the electromagnetic spectrum.
According to an embodiment of the present invention, mixtures of one or more compounds (L) and one or more compounds (N-L) may be used in the composition (C) of the invention.
Non-limiting examples of suitable inorganic compounds (N-L) include inorganic pigments such as metal salts and metal oxides, preferably selected from the group consisting of cadmium sulfide, zinc sulfide, cadmium selenite, lead chromate, zinc chromate, aluminosilicate sulfur complex, ferric oxide, ferric oxide molybdenate, chromium oxide, copper oxide, cobalt oxide, alumina, lead oxide, carbon black and mixtures thereof.
Non-limiting examples of suitable organic compounds (N-L) include, for instance, azo pigments and polycyclic aromatic pigments, said polycyclic aromatic pigments being preferably selected from those based on cyanine, phthalocyanine such as copper phthalocyanine, anthraquinone, quinacridone, perylene, perinone, thioindigo, dioxazine, isoindolinone, isoindoline, diketopyrrolopyrrole, triarylcarbonium and quinophthalone.
Non-limiting examples of suitable organic compounds (L-F) typically include polycyclic aromatic dyes such as those based on xanthene, thioxanthene, benzoxanthene, naphthalimide, coumarin, naphtholactam, hydrazam, azlactone, methine, oxazine and thiazine.
Non-limiting examples of suitable inorganic compounds (L-F) typically include inorganic compounds comprising at least one element selected from the group consisting of rare earth metals, Zn and Mn.
The composition (C) may comprise one or more than one filler; the filler may be at least one selected from the group consisting of calcium carbonate, mica, kaolin, talc, carbon black, carbon fibers, carbon nanotubes, magnesium carbonate, sulfates of barium, calcium sulfate, titanium, nano clay, carbon black, hydroxides of aluminium or ammonium or magnesium, zirconia, nanoscale titania, and combinations thereof. While silica and glass fibers are generally not preferred fillers, they may be used in the composition (C), when the components of the said composition (C) are not generating amounts of HF which may react with the said SiO2-based fillers.
The Method for Manufacturing a Three-Dimensional Object
As said, the method includes a step of printing layers of the part material, as above detailed.
Techniques for printing the said layers are not particularly limited, and may be selected notably from extrusion-based techniques, jetting, selective laser sintering, powder/binder jetting, electron-beam melting and stereolithography.
Depending upon the printing technique which is used, the part material may be provided under different morphology for being used for printing layers in the additive manufacturing system. For instance, the part material may be provided under the form of loose particles; it may be provided under the form of fluid-state thermally solidifiable material or meltable precursor thereof, or may be provided under the form of a thermosettable liquid solution.
The method may include printing layers of a support structure from a support material, and printing layers of the three-dimensional object from the said part material in coordination with the printing of the layers of the support structure, where at least a portion the printed layers of the support structure support the printed layers of the three-dimensional object, and then removing at least a portion of the support structure for obtaining the object (3D).
According to certain preferred embodiments, the printing technique is an extrusion-based technique. According to these embodiment's, the method of the invention comprises:
Although this not being required, the object (3D) generated in the method as above detailed, may be submitted to a further step causing the polymer (F-TPE) to chemically crosslink.
This can be achieved through different techniques, including notably irradiation, e.g. with beta-radiation or gamma-radiation, thermal treatment, or any combination of the same.
To this aim, composition (C) may advantageously comprise suitable curing systems facilitating cross-linking of the polymer (F-TPE).
Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.
The invention will be now described in more detail with reference to the following examples whose purpose is merely illustrative and not limitative of the scope of the invention.
In a 22 litres reactor equipped with a mechanical stirrer operating at 400 rpm, 13.9 l of demineralized water and 139 ml of a microemulsion, previously obtained by mixing 29.2 ml of a perfluoropolyoxyalkylene having acidic end groups of formula: CF2ClO(CF2—CF(CF3)O)n(CF2O)mCF2COOH, wherein n/m=10, having average molecular weight of 600, 9.5 ml of a 30% v/v NH4OH aqueous solution, 81.8 ml of demineralised water and 18.5 ml of GALDEN® D02 perfluoropolyether of formula: C—F_3—O(CF2CF(CF3)O)n(CF2O)mCF3 with n/m=20, having average molecular weight of 450, were introduced.
Then 6.1 g of 1,4-diiodoperfluorobutane (C4F8I2) as chain transfer agent were introduced, and the reactor was heated and maintained at a set-point temperature of 80° C.; a mixture of tetrafluoroethylene (TFE) (38% moles) and perfluoromethylvinylether (MVE) (62% moles) was then added to reach a final pressure of 21 bar (2.1 MPa). 1.39 g of ammonium persulfate (APS) as initiator were then introduced. Pressure was maintained at set-point of 21 bar by continuous feeding of a gaseous mixture of TFE (60% moles) and MVE (40% moles) up to a total of 3000 g. Once 3000 g of monomer mixture were fed in the reactor, the reaction was discontinued by reducing the stirring to 50 rpm and cooling the reactor at room temperature. The stirrer was then stopped and the residual pressure was discharged, and the temperature brought to 75° C. A mixture of tetrafluoroethylene (TFE) (81% moles) and perfluoromethylvinylether (MVE) (19% moles) was then added to reach a final pressure of 21 bar (2.1 MPa). As soon as the mechanical stirrer was set operating at 400 rpm, the reaction started with no need for additional initiator and the pressure was maintained at set-point of 21 bar by continuous feeding of a gaseous mixture of TFE (95% moles) and MVE (5% moles) up to a total of 750 g. Then the reactor was cooled, vented and the latex recovered. The latex was treated with nitric acid, the polymer was separated from the aqueous phase, washed with demineralized water, dried in a convection oven at 130° C. for 16 hours and finally granulated in a twin-extruder. Material characterization data of so-obtained pellets are summarized in Table 1.
In a 7.5 liters reactor equipped with a mechanical stirrer operating at 72 rpm, 4.5 l of demineralized water and 22 ml of a microemulsion, previously obtained by mixing 4.8 ml of a perfluoropolyoxyalkylene having acidic end groups of formula CF2ClO(CF2—CF(CF3)O)n(CF2O)mCF2COOH, wherein n/m=10, having an average molecular weight of 600, 3.1 ml of a 30% v/v NH4OH aqueous solution, 11.0 ml of demineralized water and 3.0 ml of GALDEN® D02 perfluoropolyether of formula CF3O(CF2CF(CF3)O)n(CF2O)mCF3, wherein n/m=20, having an average molecular weight of 450, were introduced.
The reactor was heated and maintained at a set-point temperature of 85° C.; a mixture of vinylidene fluoride (VDF) (78.5% moles) and hexafluoropropylene (HFP) (21.5% moles) was then added to reach a final pressure of 20 bar. Then, 8 g of 1,4-diiodoperfluorobutane (C4F8I2) as chain transfer agent were introduced, and 1.25 g of ammonium persulfate (APS) as initiator were introduced. Pressure was maintained at a set-point of 20 bar by continuous feeding of a gaseous mixture of vinylidene fluoride (VDF) (78.5% by moles) and hexafluoropropylene (HFP) (21.5% by moles) up to a total of 2000 g. Moreover, 0.86 g of CH2═CH—(CF2)6—CH═CH2, fed in 20 equivalent portions each 5% increase in conversion, were introduced.
Once 2000 g of monomer mixture were fed to the reactor, the reaction was discontinued by cooling the reactor to room temperature. The residual pressure was then discharged and the temperature brought to 80° C. VDF was then fed into the autoclave up to a pressure of 20 bar, and 0.14 g of ammonium persulfate (APS) as initiator were introduced. Pressure was maintained at a set-point of 20 bar by continuous feeding of VDF up to a total of 500 g. Then, the reactor was cooled, vented and the latex recovered. The latex was treated with aluminum sulphate, separated from the aqueous phase, washed with demineralized water and dried in a convection oven at 90° C. for 16 hours, and finally granulated in a twin-extruder. Material characterization data of so obtained pellets are summarized in Table 1 below.
Characterization of Materials Produced in the Examples
Determination of Thermal Properties
Thermal properties have been determined by differential scanning calorimetry pursuant to ASTM D3418 standard.
Weight loss at a given temperature Tx was measured by heating the sample in a thermogravimetric analyser (Perkin Elmer TGA7) at a heating rate of 10° C./min under a 30 mL/min flux of air.
Determination of Rheological Properties
Rheological tests have been performed according to ASTM D4440 standard, using an Anton Paar MCR502 rheogoniometer with parallel plates geometry (25 mm diameter; gap between 1 and 2 mm). Maximum strain amplitude has been set within linear viscoelastoc range of the specimen submitted to test via a preliminary automated strain sweep. Isothermal frequency sweep in the range 0.05 to 100 rad/sec at temperatures T*slightly exceeding melting point of the specimen submitted to test (Tm+10° C.<T*<Tm+15° C.) were performed, and complex viscosities values recorded.
Rheological properties of polymer of Ex. 1 and Ex. 2C are summarized in the following table.
Rheological data have been obtained at a temperature slightly exceeding melting temperature of the polymer of Ex. 1 and Ex. 2C, respectively.
The data comprised in Table above clearly show that compared to corresponding thermoplast of similar monomer composition, the present perfluorinated thermoplastic elastomer possesses lower complex viscosity at shear rates of about 100 rad/sec (which are those encountered, e.g., in the die of a fused filament forming device) at significantly lower processing temperature, so demonstrating advantageous processing behaviour.
Thermal stability of samples of Ex. 1 and Ex. 2C was determined through measuring weight loss by TGA at a temperature of 300° C.: for both materials, the weight loss was found to be below 0.1% wt, hence confirming that the two materials possess substantially the same thermal stability in the range of temperatures which is of interest for the hereby concerned field of use.
Same conclusion can be drawn considering data comprised in Table 3, herein below, comparing VDF-based thermoplastic elastomer and thermoplast.
| Number | Date | Country | Kind |
|---|---|---|---|
| 17156541.9 | Feb 2017 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/053339 | 2/9/2018 | WO | 00 |
