DK148875B - BLOOD FILTER ELEMENT, ISSUE FOR USE OF BLOOD TRANSFUSIONS - Google Patents

Description

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The invention relates to a blood filter element, especially for use in blood transfusions.

There are two general types of blood filters available in the market for use in human blood transfusions.

The most common type is made of metal wire fabric or a nylon or polyester filament weave having a pore size of from approx. 125 to approx. 14Q micron, cf.

"Surgical Advances", Vol. II, No. 6 of September 1971.

These filters are called blood screens. They have a very coarse pore size because they are very likely to be blocked quickly if the pore size is smaller.

The second type of blood filter useful for transfusions consists of a relatively thick nonwoven fibrous mat, usually of polyester fibers, and this filter is called a Dacron wool filter. This filter is subject to United States Patent No. 3,448,041. The commercially available filters have a pore size of up to several hundred microns and are made of very fine fibers.

2Q The principle on which this latter filter type is based is disclosed in the aforementioned United States patent from column 3, line 51 to column 4, line 36. This filter requires a finely divided material having such properties and size that the material selectively collects the constituent altered components of the blood used in blood transfusions. The filter is designed to act as a substrate to which the sticky altered platelets and white blood cells adhere to storage. It is believed that the other blood components can freely pass through the filter, which has a large absorbent surface area to obtain a large capacity at a minimal device size. This type of filter also requires a material which can be used for long periods of operation without collapsing or clogging and which, without being adversely affected, can repeatedly be subjected to heating and chemical sterilization.

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The problem with the blood screens is that they do not remove enough of the finely divided material due to their large pore size. On the other hand, in the form of a mat made of nonwoven fibrous material, the filters go to the opposite extreme. Despite their large pore size of over 100 microns, these filters remove too much material and are also very prone to blockage. A large number of platelets and white blood cells, as well as particles of similar size in the blood, are prone to being filtered, leading to a rapid blockage and compression of the mat under the effect of the increased fluid pressure differential over it. Both of these effects are undesirable. These results are discussed by Egeblad, Osborn, Burns, Hill and Gerbode in "The Journal of 15 Thoracic and Cardiovascular Surgery", Vol. 63, No. 3 of March 1972, pages 384-390, and by McNamara, Burran, and Suehiro in a paper entitled "Effective Filtration of Banked Blood."

In the first of these writings, it is stated that 20 good results were obtained using the Dacron wool filter under perfusion in cardiac surgery, where the filter was placed in the line between the cardiotomic reservoir and the main vein line, in which a large portion of the circulating blood runs around the filter. Such an arrangement 25 requires a much greater flow rate of blood than a blood transfusion arrangement, so that the results obtained represent results similar to those obtained by blood transfusion but provided in a shorter time. By placing the filter in an arterial line so that all 3 blood of the oxygenator was filtered, a pressure gradient was built over the filter which necessitated a conversion to another filter which was placed parallel to the first, and in addition air was trapped in the filter during the first filling, and rico-35 was found to allow this air to be subsequently expelled directly into the arterial line. Blood reached a very low level of platelets within the first 10 minutes of use of the filter, 148875 • 3

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and this condition persisted throughout the cycle. There was also a decrease in the number of white blood cells, and the decrease in the number of both these types of particles was more pronounced than is usually the case with cardiac 5 pulmonary diversion, which showed that the filter captured large amounts of platelets and in smaller extensively white blood cells. The pressure gradient built up over the filter was partly due to this mass of particles and partly to intravascular coagulation to form fibrin trapped in the filter. In addition, the platelets captured on the filter tended to later decompose, so that the decomposition products were introduced into the filtered blood.

According to the invention which is the subject of Danish patent application no. 5491/71, cf.

133 133,366, a disposable filter element is provided

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for example, a square woven plastic grid of polyester monofilaments having a pore size within the range of from approx. 25 to approx. 50 microns, the filaments being locked in place at their intersection points, and the filaments having a diameter 2Q within the range of approx. 25 to approx. 50 microns. Such filter elements are capable of removing human blood microplugs in human blood circulation systems requiring high blood flow circulation without removing normal and desirable blood components. The filter not only removes microblocks, but also lipids and waste-25 substances and air plugs, and it also has a low resistance at high flow rates and a large flow capacity and is not prone to block for long periods of use.

However, for blood transfusion, this filter is not entirely satisfactory. Blood for use in transfusions tends to contain clots of solidified blood, which is not a condition that usually occurs in human blood circulation systems when the patient's blood is used in the circulation system. Clots of solidified blood are 35 sticky masses of material, and if a large number of clots of solidified blood occur, the square-woven plastic, lattice can quickly become blocked.

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The object of the present invention is to provide a blood filter element which can be used in non-blocking blood transfusions and which can remove not only large particles, such as clumps of clotted blood, but also 5 smaller particles down to a size of approx. 20 μ, while allowing red blood cells and at least a substantial portion of the white blood cells to pass. This is achieved by, as further specified in the characterizing part of claim 1, arranging the blood filter element with two filter sheets arranged in order of increasing fineness, ie. from the coarsest to the finest pore size, in the flow direction.

The first filter sheet is a coarse, open network of plastic filament material with a pore size within the range of approx. 800 to approx. 4,000 microns. This pore size is sufficiently small to remove clots of clotted blood within the diameter range of 500 to 1,000 microns and is sufficiently coarse for this to occur without blocking due to the filtration of clots of clotted blood.

The second filter sheet is an open woven or square woven network of plastic monofilaments having a pore size within the range of from ca. 20 to approx. 50 microns. This filter sheet removes micro blood clots, lipids and waste substances as well as air plugs, ie. virtually all of the particles passing through the first filter element, except for blood platelets, white blood cells, red blood cells and other similar small particles.

This combination of filter sheets can be referred to as a series because each subsequent filter sheet in the flow path removes some of the particles passing through the previous filter sheet. The inter-aspect ratio of the particles removed by the individual filter sheets in this filter series is clearly divided between the two filter sheets so that neither filter sheets are prone to being blocked during a given blood transfusion for a single patient. For sanitary reasons, blood transfusion filters are not used again, even to the same patient, if a second transfusion is to be performed at a later date, and then

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The element according to the invention is fully disposable, the use thereof solves the blocking problem common to blood filters sufficiently fine to remove small particles such as the adhesive non-viable platelets.

The first filter sheet has an open mesh structure.

It is produced by extrusion, molding or molding of plastic to form an open network having a coherent filament structure.

10 The plastic material used is compatible with blood.

Examples of materials which can be used include polypropylene, polyethylene, polyester, polyamide and poly carbonate.

One embodiment is similar to an open, square woven 15 filament network, although it is not made by filament weaving. An extruded, open-mesh plastic filament polypropylene sheet is commercially available under the registered trademark "Vexar".

There are other types of networks available that do not correspond to an open, square woven network. In these filament fabrics, plastic material may be disposed in such a way as to form round, elliptical or polygonal apertures such as e.g. may be triangular, square, rectangular, pentagonal, hexagonal, hexagonal, and octagonal, either individually or in pattern combinations. One embodiment of such fabric has triangular apertures separated by plastic filament material and arranged in groups of six to form a hexagonal pattern, while another embodiment has triangular apertures disposed in groups of two to form and rhombus. The shape of the open pores in the network is by no means critical, but it is important that the pore size is within the range of approx.

80Q to approx. 4,000 microns, the pore size range being measured as the largest and smallest dimension if the pores 35 have shapes other than the circular or a symmetrical shape, such as a square shape.

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The second filter sheet is an open-mesh square woven fabric which may be made of any blood-compatible plastic monofilaments such as polypropylene, polyethylene, polyester, polyamide and polycarbonate, having a pore size within the range of from about. 20 to approx. 50 microns. The monofilaments have a diameter within the range of approx. 20 to approx. 50 microns.

Polyester monofilaments are preferred. Most of the polyester monofilaments available are polyesters of ethylene glycol and terephthalic acid and these are available under the registered trademark "Dacron". Polyester monofilaments may also be prepared from other polymers of alkylene glycols and dicarboxylic acids, usually aromatic acids, but also cycloaliphatic and aliphatic acids, of which, for example, polypropylene glycol-1,2, butylene glycol-2, 3 and -1,2 and pentylene glycol-1,2 and -2,3 and -1,3 esterified with terephthalic or alkyl-substituted terephthalic acids or adipic or subaric acids or cyclohexane-1,4-2Q-dicarboxylic acid.

The ethylene glycol terephthalic acid polyester monofilaments are preferred because they are inexpensive.

However, polyesters of other glycols and acids can also be used.

Examples of polyester monofilament screen materials, 2L 3 which can be used as filter sheets of the present invention, are such materials made of polyester monofilament having a diameter of 20, 25 and 40 microns, with (a) a mesh opening of 53 microns with 33 % open area, 3Q (b) a 44 micron mesh aperture with 27% open area, (c) a 37 micron mesh aperture with 33% open area, and (d) a 21 micron mesh aperture with 14.5% open area. Corresponding screeners are available made of polyamide filaments, polyvinylidene chloride filaments and polypropylene-35 filaments.

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It is also preferred that the monofilaments of the square woven network be locked in place at their intersection points. The locking not only causes an increase in strength and stiffness, but also prevents a change in the pore dimensions during use, which is extremely important.

The double-filter sheet series of the invention can be mounted in disposable filter elements or can be formed in any other shape. In order to achieve a maximum open area and a large flow rate within a confined space, the two filter sheets are preferably assembled close to one another, although they may also be separated by a spacer, and both filter sheets are preferably corrugated or rolled. for providing a large surface area for flow along with any spacers used. The spacer has a pore size that is at least as large as the pore size of the first filter sheet, and which is preferably larger, being within the range of approx. 800 20 to approx. 10,000 microns.

Some preferred embodiments of the invention will now be described in more detail with reference to the accompanying drawings, in which: FIG. 1 is a side elevational and sectional view of a filter element according to the invention including a double filter; FIG. 2 is a partial sectional view of FIG. 1 illustrates the filter element illustrating the side caps of the filter housing; FIG. 3 is a detailed and sectional view of the portion of FIG. 1 shows a filter element according to the invention, fig. Fig. 4 is a perspective view of an embodiment of a filter element according to the invention made in bag form and including a double filter; 5 is a longitudinal section through the embodiment of FIG. 4 shows the filter element along line 5-5 and seen in the direction shown by arrows, and

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8 U3875 FIG. 6 is a cross-section through the embodiment of FIG. 4, the filter element shown on the line 6-6 w is seen in the reference indicated in the food arrow.

The FIG. 1-3 a filter element is composed of 5 a housing 1 having a first and a second housing parts 2 and 3 between which a fluid chamber 4 is formed. There is a fluid opening 5 at the base of the housing channel part 2 and a fluid opening exists. 6 at the base of the housing part 3.

It can be seen that these openings are arranged coaxially. The orifice 5 serves as fluid inlet, while the orifice 6 serves as the fluid outlet and the flow occurs, as seen, only in the direction from the orifice 5 to the orifice 6 due to the placement of the two filter sheets in the series.

The inlet port 5 is disposed in a tapered tube 7 arranged to puncture a blood bag plug for use in blood transfusion. The housing portion 2 has an inner projection or rib 8 extending from one side 9 to the other side 10, and the housing portion 3 has a corresponding inner projection 11 extending from one side 2Q to the other side 13. These serve as supports as they extend over the corrugations of the three-component assembly containing the filter sheet series and the spacer, which aggregate serves as a filter.

Each housing portion 2 and 3 is generally channel-shaped with opposite sides 9 and 1Q extending outwardly from the base portion of the housing portion 2, and opposite sides 12 and 13 extending outwardly from the base portion of the housing portion 3. The base portions of housing portions 2 and 3 are each provided with fluid flow channels 14. Housing portion 2 has on each side a pair of locating fingers 15, and housing portion 3 has on each side two pairs of locating fingers 16 with an intermediate slot 17 into which fingers 15 fit.

These parts locate the housing parts 2 and 3 upon assembly thereof.

The sides 12 and 13 abut at their ends against the sides 9 and 10 and are fused with them so that the housing parts are attached to each other to form a single piece. A pair of projecting portions 20 and 21 of housing portion 3 extend parallel to and within sides 12 and 13 all the way to the inner wall of housing portion 2.

The assembly 40, consisting of the two-component filter-sheet series and spacer, projects at each edge 22 and 23 into the spaces 24 and 25 formed by the sides 12 and 13 and the portions 20 and 21, and at the locations. where the three-sheet assembly bends around the tips 20 and 21, it is held tight at 26 and 27 against the inner wall 10 of the housing part 2, being attached thereto.

The fastening is provided by fusing the parts 2Q and 21 with the housing part 2 through the open pores of the two-filter sheet 41, 42 and the spacer 44 to form a liquid tight closure at 26 and 27 all the way along their 15 sides of the assembly. all three sheets are attached to each other in these points. Such a joint may e.g. is obtained by ultrasonic welding, by softening with a solvent or by melting using heat.

The assembly 40 of the filter sheet series and spacer 40 is, as is clearly seen in FIG. 3, composed of a first coarse filter sheet 41 of extruded polypropylene network, available under the trademark Vexar, with a pore size of approx. 1500 microns. The spacer 44 is also made of extruded polypropylene network, available 25 under the trademark Vexar, with the same pore size of approx. 1500 microns. The second filter sheet 42 is made of open-mesh, square-woven polyester monofilament fabric with a pore opening of 40 microns, a monofilament diameter of 40 microns and 27% open area. The islet monofilaments 30 and the chain monofilaments are supported on each other by hot curing at their intersection points to form solid pores with a size of 40 microns between them.

The two filter sheets 41 and 42 of the filter series are corrugated in order to increase the surface area within 35 within the confined space of the fluid chamber 4, and the tips of the corrugations abut and are held in place by the protruding parts 8 and 11 of the housing parts 2 and 3.

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The Sfåfllrfiflf ^^ 3 filter sheet series extends straight to the ends of pages 12 and 13.

The housing duct portions 2 and 3 are open at their sides, as can be seen most clearly in FIG. 2 to form aperture-5 are 28 and 29 leading into fluid chamber 4 in housing 1. The openings are closed by side caps 30 and 31 attached to housing parts 2 and 3 as well as to edges 32 and 33 of the assembly 40, which comprises the filter sheet series and the spacer means, extending across the apertures 2 to 0 from end to end between the mutually fitting parts 9, 10, 12 and 13 of the housing parts. Hereby, the two other side edges of the fluid flow filter sheet series are closed, so that the flow is limited to flow between the two portions 34 and 35 of the fluid chamber 4 of the housing via the pores of each of the filter sheets of the filter sheet series 40. Any flow between the fluid openings 5 and 6 of the housing 1 may thus pass each of the two filter sheets in the direction 41, 42 as shown in FIG. Third

The assembly of the device shown in FIG. 1-3, the box-filter element 20 is carried out as follows. Referring now to FIG. 1, that the side parts 9, 10, 12 and 13 of each housing part 2 and 3 have a special structure which ensures a liquid tight closure between the housing parts when attached to each other. The opposite sides 9 and 10 of the housing part 2 meet and abut corresponding sides 12 and 13 of the other housing part 3. The housing part 2 has one pair of side locating fingers 15 on each side and the housing part 3 has on each side two pairs of side locating fingers 16 between which the fingers 15 are accommodated to ensure that the parts fit tightly together in the correct position for 2Q retention of the filter sheet series 40.

The sides 9, 10, 12 and 13 are each slightly longer than their combined length after being attached to each other. When the housing parts 2 and 3 are assembled, the sides 9 and 10 can be easily melted to the sides 12 and 13 to 35 respectively, creating a one-piece continuous structure at the closed 36, see FIG. 1 and 2. Within the sides 11 148875 and 12 and 13 there are in the housing part 3 projecting parts 20 and 21, which extend all the way to the inner wall at 26 and 27 of the housing part 2.

During assembly, the edges 22 and 23 of the aggregate 40, consisting of the corrugated filter sheet series and spacer, are folded around the projecting portions 20 and 21 of the housing portion 3 and into the spaces 24 and 25 between the sides 12 and 13 and the projecting portions. parts 20 and 21 where they are securely held. The housing part 2 is then mounted above the housing part 3 and pressed firmly against the filter sheet series and the combined spacer while clamping these three sheets at 26 and 27 against the tips of the projecting parts 20 and 21 and holding the three sheets firmly in place at the tight interaction between the inner wall of the housing part 2 and the ends of the parts 20 and 21.

The protruding portions 20 and 21 are then joined together through the pores of the spacer 44 and in the two filter elements 41 and 42 at 26 and 27 with the wall of the housing portion 2 to form a liquid-tight seal between these components and closure of both sides of the housing. the filter sheet series for the fluid flow. The sides 9 and 10 of the housing part 2 can also be attached to the sides 12 and 13 of the housing part 3 by melting, such as by ultrasonic welding, either simultaneously or later such that the two housing parts 2 and 3 are tightly connected to each other to prevent a fluid leak. the exterior of the filter assembly.

Next, the side caps 30 and 31 over the openings 28 and 29 are secured in the housing portions 2 and 3 to the edges 32 and 33 of the assembly consisting of the filter sheet series and the spacer, attaching the filter sheet sides and the spacer to the side caps and completing the fixing of the filter sheet series and the spacer 40 in place in the fluid chamber 4 along with the seals between the filter sheet series and the four side walls of the housing. This can be done at 35 e.g. to use an adhesive or melt of adhesive or resin or other sealant or by melting the end caps. The filters element is now complete and ready to use.

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The filter element is used in a conduit as follows. The pointed end is inserted into the stopper in a blood bag, whereby blood can flow from the bag through the inlet opening 5 and from there into the duct 14 and further into the chamber portion 34. The blood then flows through the filter sheet series 40 via the filter sheet 41, filter sheet 42 and the spacing means 44 from which the blood is introduced into the chamber portion 35 from which it flows out through the duct 14 from the housing through the opening 6.

Conduit connections can be provided at the openings 5 and 6 in any desired manner. Also, if desired, so-called luer locking means can be used.

The FIG. 4-6, the filter element 50 has a filter in the form of an assembly 60 consisting of a two-component filter sheet series, comprising sheets 41 and 42 and a spacer sheet 44 in corrugated, roofed form with corrugated folds 51 located in the plane of the filter element in an overlapping manner. .

The two filter sheets 41 and 42 and the separating spacer 44 are positioned exactly as shown in FIG. 3, the filter sheet 41 being outermost positioned, while the spacer means 44 being disposed innermost in the closed form shown in FIG. 4-6. The corrugated assembly 60 is heat sealed at 52 along its four sides or along three sides if folded on itself. The thus-enclosed filter-sheet series 60 has an outlet conduit connection via a tube 53 which extends into its open inner cavity 54 and terminates in a dome-shaped end bottom 55 formed as a sieve. The only approach to the inner cavity 54 extends through the filter sheet series 60. This type of filter element 30 is particularly useful in a flexible bag type filter unit, and the bag 56 is shown in this case in dotted lines in FIG. 4 and 5. The other end of bag 56, which may be constituted by the blood bag itself, may be provided with an inlet tube 57 for receiving blood. It is also possible to use a tapered inlet tube 57 which opens outside the assembly 60 in the bag 56, in which

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It can be attached to bag 56 by heat sealing in the same way as the filter element · This assembly is inserted as a plug into a blood bag, just as is the case with the filter element of FIG. 1 and 2, with the filter sheet 41 5 outermost and the spacer means 44 innermost.

The filter element shown in FIG. 4-6, is particularly useful for transfusion blood filtration, in which case it can be incorporated into a standard blood bag, but it can also be attached to any blood vessel.

The corrugated form of the filter sheet series in this element provides a large surface area, and the layered arrangement of the corrugations makes it possible to provide a flat bag without the need for a core support, because the spaces between the folds act as wires, while 2 ^ 5 the overlapping structure. at the same time providing a structural support. The support sheet or spacer sheet 44 for the two filter series is made of material which can be softened by heating and which is softened at a lower temperature than any of the 2Q two filter sheets forming the series so that the filter sheets 41 and 42 are not affected. under the conditions under which the spacer is softened, whereby the latter can be fused to form a liquid-tight heat seal through the pores of the filter sheet, without adversely affecting the filter sheets. The heat seal is easily performed by high frequency heating, and all heat seals, including the heat seals in conjunction with the pipes, can be performed simultaneously.

As a spacer, any sheet 30 having a bump, e.g. lid, ribbed or folded surface and having large openings through it. Extruded, molded and shaped mesh as well as perforated sheets of polypropylene, polyethylene, polyester, polycarbonate and polyamide can be used. The surface of the spacer or support member is sufficiently uneven to provide a drainage and to block the middle and fine filter sheets by the support sheet. A preferred support material is a network consisting of extruded polypropylene network and available under the Vexar brand.

The spacers may also assist in keeping the filter sheet series in a desired shape, such as especially in corrugated form. If a spacer is used, this is usually placed close to or in contact with the second filter sheet in the series. It is not necessary to place any spacer sheet before or after the first 10 filter sheet, which consists of an open network, because of its large pore size.

In a suitable design of a filter element, the filter sheet is folded into a corrugated cylinder, the open ends of which are closed by end caps to limit the filtrate flow line such that it must extend through the filter series, the filtrate flow line being connected to at least one of the end caps. . The end caps preferably consist of plastic material and can e.g. be made of polyester, polypropylene or polycarbonate. The end caps may be attached to the corrugated filter sheet series using a ceramic material or adhesive of conventional type. However, to ensure liquid seal, it is preferred to melt the end caps of the filter sheet series, and for this purpose a polyolefin such as polyethylene or polypropylene is preferred to the end cap material. Other plastics materials that can be used as end caps include polyamides, oolycarbonates and polyesters, as well as "Teflon" (polytetrafluoroethylene) and "Kel-F" (polytrifluorochlorethylene), but these substances are more difficult to attach.

In another suitable form of a filter element, the filter sheet series and spacer sheets in corrugated form are enclosed in a plastic bag across the flow line between the inlet and outlet of the bag, e.g. may take the form of conduit connections, such as tubes, which open at opposite sides of the filter sheet series. This type is particular

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Applicable for attachment to blood transfusion bags and, if desired, for this purpose may be provided with a puncture tube connection.

The filter element according to the invention, if desired, can be used in conjunction with pumps in filter units arranged for simple blood transfusion where no high flow rates occur, such as by dripping or flow by gravity from blood bags. To this end, the filter element may be provided with 10 fittings or conduits suitable for adapting it for connection in blood transfusion systems of any kind.

Claims (7)

148875 O Patent Claims. Blood filter element, especially for use in blood transfusions, characterized in that it comprises, in combination, two filter sheets (41 and 42} arranged in order of increasing fineness, calculated in the flow direction, of which filter sheets first (41) consists of a coarse, open network of plastic filament material having a pore size in the range of about 800 to 4,000 µg microns, the second filter sheet (42) consisting of an open screen fabric of plastic monofilaments having a pore size in the range of about 20 to about 50 microns. Blood filter element according to claim 1, characterized in that the first filter sheet (41) consists of a network made by extrusion, molding or molding of plastic and having a connection. extending filament structure. Blood filter element according to claim 2, characterized in that the plastic material is selected from the 2q group comprising polypropylene, polyethylene, polyester, polyamide and polycarbonate. Blood filter element according to claim 1, characterized in that the second filter sheet (42) is a square woven network of plastic monofilaments having a pore size within the range of from approx. 20 to approx. 50 microns, whereby the filaments are locked in place at their intersection points. Blood filter element according to claim 4, characterized in that the monofilaments have a diameter 2Q within the range of from approx. 25 to approx. 50 microns. Blood filter element according to claim 4, characterized in that the monofilaments are made of polyester plastic. Blood filter element series according to claim 1, characterized in that the filaments are thermoset for locking them in place.