WO2020049211A1

WO2020049211A1 - Composite filament

Info

Publication number: WO2020049211A1
Application number: PCT/FI2018/050632
Authority: WO
Inventors: Mikko Huttunen; Timo Lehtonen; Arto MESKANEN; Marjo KETONEN
Original assignee: Arctic Biomaterials Oy
Priority date: 2018-09-06
Filing date: 2018-09-06
Publication date: 2020-03-12

Abstract

A composite filament is disclosed, containing polylactic acid and/or other poly-al-pha-hydroxyacid based polymer, co-polymer, terpolymer, polymer blend or copolymer blend, as a polymer matrix, and nanoscale reinforcement. The composite filament optionally contains an additive selected from one or more of nucleating agent, impact modifier, and filler. Also a method of manufacturing the composite filament is disclosed, comprising melt mixing components of the filament together in one or more processing steps to obtain a composition, and subjecting the composition thereby obtained to a further processing step to form the filament.

Description

COMPOSITE FILAMENT

F1ELD OF THE INVENTION

The present invention relates to a composite filament, and more partic ularly to a method for manufacturing the composite filament. BACKGROUND

The following background description art may include insights, discov eries, understandings or disclosures, or associations together with disclosures not known to the relevant art prior to the present invention but provided by the pre sent disclosure. Some such contributions disclosed herein may be specifically pointed out below, whereas other such contributions encompassed by the present disclosure the invention will be apparent from their context.

Clay is a widely investigated and commercially high demand filler in the polymer industry. Polymer/clay nanocomposites are capable of having superior properties compared to conventional filled polymers even at a very low fraction of filler addition. The easy availability, processability, low cost, and nontoxicity of clay and the advancements in the processing of clay nanocomposites have raised com mercial interest in these materials. The value-added properties enhanced without sacrificing of pure polymer properties make the clays important in the modern pol ymer industry. Possible applications of polymer/clay nanocomposites range from household items to aerospace and medicine.

SUMMARY

The following presents a simplified summary of features disclosed herein to provide a basic understanding of some exemplary aspects of the inven tion. This summary is not an extensive overview of the invention lt is not intended to identify key/critical elements of the invention or to delineate the scope of the invention lts sole purpose is to present some concepts disclosed herein in a sim plified form as a prelude to a more detailed description.

According to an aspect, there is provided the subject matter of the inde pendent claims. Embodiments are defined in the dependent claims.

According to an aspect, there is provided a composite filament contain ing

polylactic acid and/or other poly-alpha-hydro xyacid based polymer, co-polymer, terpolymer, polymer blend or copolymer blend, as a polymer matrix; and nanoscale reinforcement;

and optionally an additive selected from one or more of:

nucleating agent;

impact modifier; and

- filler.

According to another aspect, a method of manufacturing the composite filament comprises melt mixing components of the filament together in one or more processing steps to obtain a composition; and subjecting the composition thereby obtained to a further processing step to form the filament.

According to yet another aspect, the composite filament is used for ad ditive manufacturing of a part.

According to yet another aspect, there is provided a 3D printed part pre pared by fused filament fabrication, by using the composite filament as raw mate rial.

One or more examples of implementations are set forth in more detail in the description below. Other features will be apparent from the description, and from the claims.

DETA1LED DESCRIPTION OF EMBOD1MENTS

The following embodiments are exemplary. Although the specification may refer to "an", "one", or "some" embodiment(s) in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Furthermore, words "comprising", "containing" and "including" should be understood as not lim- iting the described embodiments to consist of only those features that have been mentioned and such embodiments may contain also features/structures that have not been specifically mentioned.

Stiffness represents a material sample’s resistance to deformation, i.e. how it behaves under the application of external loading. Young's modulus, also known as the elastic modulus, is used as a measure of the stiffness of solid material. The mechanical properties of plastic materials depend on the strain (rate) and tem perature. At low strain, the deformation is elastic, and after removal of the deform ing load the plastic returns to its original size and shape ln this regime, the stress (s) is proportional to the strain (e), i.e. s = E e, where E is the tensile (or Young's) modulus of the plastic, which is a measure of the stiffness of the material lt means that when a plastic sample is pulled at a (constant) strain rate the applied stress (or load) is directly proportional to the observed strain (or elongation) lf the plas tic material is loaded beyond its elastic limit, it does not return to its original shape and size, i.e. a permanent deformation occurs. Generally the stiffness means the rigidity of an object; the extent to which it resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flex ible an object is, the less stiff it is.

Toughness is a measure of the energy a material sample is able to ab sorb before it breaks. Toughness differs from strength in that strength tells how much force is needed to break the sample, and toughness tells how much energy is needed to break the sample. A strong material is not necessarily tough as well. Toughness may be determined by plotting stress (=y-axis) against strain (=x-axis). lf the area underneath the plotted stress-strain curve (i.e. the area between the stress-strain curve and the x-axis) is measured, the value obtained is toughness. Tough material has higher a elongation at break than the brittle material with com parable maximum strength. Toughness of a material may in generally mean that the material is not brittle and the material does not easily break e.g. when bended. Tough materials typically have improved impact resistance when compared to more brittle materials.

Polylactic acid, or polylactide, is a biodegradable thermoplastic ali phatic polyester derived from renewable resources, such as corn starch, cassava roots, chips or starch, or sugarcane. Alternatively polylactide may be totally syn thetic. Plain polylactide (PLA) is a brittle and stiff polymer ln an embodiment, PLA is modified so that the toughness and/or impact resistance of PLA is remarkably increased while the stiffness remains on a range comparable to that of plain un modified PLA.

An embodiment discloses a composite filament, a method for manufac turing the composite filament, and use of the composite filament for 3D printing ln an embodiment, a composite PLA filament is manufactured from PLA-based poly- mer matrix which is toughened by using nanosized reinforcement filler, such as nanoclay, and other additives as described below. The stiffness of such material is comparable to plain PLA while its toughness is superior to PLA.

An exemplary composition of the composite filament contains PLA- based polymer as a matrix in which nanoscale filler, such as nanoclay, is melt mixed with the matrix polymer. The nanoclay in the composite filament acts as a na- noscale reinforcement thereby increasing the strength and stiffness of the compo site structure of the filament. The filament may also include other additive(s), such as impact modifier(s), colorant(s), plasticizer(s), fire retardant(s), etc. The nanoclay and the additive (s) may be added to the composite material in separate processing steps. The stiffness of such material is comparable to plain PLA while its toughness is superior to PLA. Additionally other properties of such material may be superior to plain PLA, depending on chosen additives.

An exemplary composition further includes additive(s) which increases the crystallinity of the material(s). Such additive(s) serve as a nucleating agent in- creasing the degree of crystallinity, which increases the strength and temperature resistance of the material. For example, aromatic sulfonate derivative(s), such as LAK 301, may be used as an additive that increases the crystallinity of the mate rials), thereby increasing the strength and temperature resistance of the material. The stiffness of such material is comparable to plain PLA while its toughness and heat deflection temperature, i.e. heat resistance, is superior to PLA. Additionally other properties of such material may be superior to plain PLA, depending on cho sen additives.

Stiffness of the composite filament may be also improved (i.e. in creased) by using talc (i.e. magnesium silicate) as mineral filler. The mineral filler, such as talc, which may be of nanoscale or of submicron scale, has a physical rein forcement capability and simultaneously a positive effect to the crystallization rate, thereby enhancing the reinforcing of the material and the crystallization rate of the material. Particle size (gm) and load-% of the mineral filler may be adjusted ac cording to need. For example, the particle size may be from 0.5 gm (500 nm) to 30 gm (30 000 nm) and the load may be from 1% to 10%. By adjusting the amounts of aromatic sulfonate derivative and talc mineral in the composition, the stiffness and toughness of the composite may be adjusted. Specifically, by adjusting the ar omatic sulfonate derivative/talc mineral ratio in the composition, the stiffness and toughness of the composite may be adjusted. Measurements show that increasing filler load from 5% to 13% lead to 48% increase in flexural modulus.

An exemplary composition may also include at least one impact modi fier as an additive. The impact modifier is a compound that improves the impact strength of the polymer. The impact modifier forms entanglements in the matrix polymer, thereby resulting in improved impact strength properties. The impact strength is improved so that the composition containing at least one impact modi fier has a better (i.e. increased) shock absorption capability. The entanglements may be formed when the components of the composite filament are melt mixed, or during the crystallization process of matrix polymer. For example, MBS (methacry late butadiene styrene) may be used in the composition as an additive that acts as an impact modifier to improve the impact strength composite filament.

An exemplary composition of the composite filament contains or con sists of:

PLA and/or any other poly-alpha-hydroxyacid based polymer, co polymer, terpolymer, polymer blend or copolymer blend or any mix ture thereof as a polymer matrix; and

nanosized reinforcement, such as Cloisite 20a nanoclay, in an amount of 0.1 wt-% - 20 wt-%, preferably 0.5 wt-% - wt-1.5%; and optionally one or more of:

nucleating agent, such as LAK 301, in an amount of 0.1 wt-% - 20 wt-%, preferably 0.5 wt-% - 1.5 wt-%;

impact modifier, such as MBS, in an amount of 0.1 wt-% - 30 wt-%, preferably 5 wt-% - 15 wt-%; and

talc (Mg silicate) having an average particle size of 0.5 gm (500 nm) to 30 gm (30 000 nm), in an amount of 1 wt-% - 20 wt-%, preferably 3 wt-% - 10 wt-%.

As describe above, poly-alpha-hydroxyacid based polymer such as PLA is used as the polymer matrix in the filament. Nanoclay such as Cloisite 20a is used as the nanosized reinforcement that increases the impact strength of the filament. Nucleating agent such as LAK 301 may be used to increase the degree of crystallin ity of the polymer matrix, enabling increased strength and temperature resistance of the filament lmpact modifier such as MBS may be used to improve the impact resistance of the filament. Talc may be used to improve stiffness and degree of crys tallinity of the filament.

An exemplary method for manufacturing the composite filament com prises mixing components of the filament together in one or more processing steps, and subjecting the composition thereby obtained to heat and pressure to form the filament. The method may comprise mixing components of the filament together by using melt mixing, such as twin screw melt extrusion and/or compounding, to obtain the composite filament.

ln an exemplary embodiment, the composite filament may be used for additive manufacturing (i.e. 3D printing) of a part. The additive manufacturing may comprise fused filament fabrication (FFF). ln an exemplary embodiment, there is provided a 3D printed part pre pared by fused filament fabrication, by using the composite filament as raw mate rial. Example 1

The feasibility of a composite filament on 3D printing was studied by using PLA (HP2500) in which 1% of nanoclay was melt mixed to form a mixture. Other additives in the mixture included 1 wt-% of LAK and 10 wt-% of MBS. The amount of PLA in the mixture was thus 88 wt-%. The obtained mixture was melt processed into a form of a continuous filament having a diameter of 1.75 mm. The obtained continuous filament was used as a raw material in 3D printing by means of fused filament fabrication (FFF). The stiffness of 3D printed part (standard dog bone test bar) thus obtained was similar as plain PLA (manual measurement ac cording to how the material feels on hand while bending), but the toughness was superior to plain PLA. Toughness of the 3D printed part was observed manually by bending the formed part and by comparing the results to a part 3D printed from plain non-reinforced PLA material. Both parts were bent to 90 degrees angle from the middle. The part manufactured from plain PLA broke in two parts, while the part manufactured from the material according to an embodiment of the present invention showed no visual signs of a fracture.

Example 2

The effect of different additives on various material properties was studied. The results are shown in Table 1 and Table 2 illustrating the effect of dif- ferent additives on these material properties. When compared to samples com posed of plain PLA (A) or highly crystalline PLA (B), the materials according to em bodiments of the present invention (C - F) were proven to have improved material properties. When compared to plain PLA (A) and/or crystallized PLA (B), the ma terials according to embodiments of the present invention demonstrated improved toughness as measured in strain at break and impact strength and improved tem perature resistance measured in heat deflection temperature. The stiffness of the materials according to embodiments of the present invention were comparable to that of plain PLA (A) and/or crystallized PLA (B) Table 1

Table 2

Even though the invention has been described above with reference to examples, it is clear that the invention is not restricted thereto but can be modified in several ways within the scope of the appended claims. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment.

lt will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The inven tion and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

CLA1MS

1. A composite filament, containing

polylactic acid and/or other poly-alpha-hydro xyacid based polymer, co-polymer, terpolymer, polymer blend or copolymer blend, as a polymer matrix; and

nanoscale reinforcement;

and optionally an additive selected from one or more of:

nucleating agent;

impact modifier; and

- filler.

2. A filament according to claim 1, wherein the nanoscale reinforcement is nanoclay, such as Cloisite 20a.

3. A filament according to claim 1, wherein the reinforcement is na noscale/micron scale talc.

4. A filament according to claim 1, 2 or 3, wherein the filament contains the nanoscale reinforcement in an amount of 0.1 wt-% - 20 wt-%, preferably 0.5 wt-% - wt-1.5%.

5. A filament as claimed in any one of the preceding claims, wherein the nucleating agent is an aromatic sulfonate derivative, such as LAK 301.

6. A filament as claimed in any one of the preceding claims, wherein the filament contains the nucleating agent in an amount of 0.1 wt-% - 20 wt-%, pref erably 0.5 wt-% - 1.5 wt-%.

7. A filament as claimed in any one of the preceding claims, wherein the impact modifier is methacrylate butadiene styrene.

8. A filament as claimed in any one of the preceding claims, wherein the filament contains the impact modifier in an amount of 0.1 wt-% - 30 wt-%, prefer ably 5 wt-% - 15 wt-%.

9. A filament as claimed in any one of the preceding claims, wherein the filler is talc.

10. A filament according to claim 8, wherein the talc has an average par ticle size of 0.5 gm (500 nm) to 30 gm (30 000 nm).

11. A filament as claimed in any one of the preceding claims, wherein the filament contains the filler in an amount of 1 wt-% - 20 wt-%, preferably 3 wt- % - 10 wt-%.

12. A method of manufacturing a composite filament as claimed in any one of the preceding claims, wherein the method comprises melt mixing components of the filament together in one or more pro cessing steps to obtain a composition; and

subjecting the composition thereby obtained to a further processing step to form the filament.

13. A method according to claim 12, wherein the method comprises mixing components of the filament together by using melt mixing.

14. A method according to claim 12 or 13, wherein the method com prises subjecting the composition to twin screw extrusion and/or compounding to form the filament.

15. Use of a composite filament as claimed in any one of the preceding claims 1 to 11 for additive manufacturing of a part.

16. Use according to claim 15, wherein the additive manufacturing com prises fused filament fabrication.

17. A 3D printed part prepared by fused filament fabrication, by using a composite filament as claimed in any one of the preceding claims 1 to 11 as raw material.