JPS5814306B2 - Composite reinforced hose - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composite reinforced hose for conveying fluids under pressure, and more particularly to a composite reinforced hose for use in certain applications without substantially sacrificing other desirable physical properties. The present invention relates to composite reinforced hoses of this type of construction which have certain beneficial physical properties.

Composite hoses are used in many applications to convey fluids under pressure.

A typical flexible hydraulic hose includes a core tube extruded from one type of synthetic resin and a fibrous reinforcement around the core tube to hold the core tube against radial expansion and elongation. It has a protective exterior made of synthetic resin that covers the fibrous reinforcing material.

Composite hoses of this type are known, for example, in U.S. Pat. No. 3,062
, 241 specification, 3,332,447 specification, 3,334,165 specification, 3,251,381 specification, 3,116,760 specification, 3,722
, No. 550, etc.

These composite hoses must be flexible, substantially kink resistant, and have burst strength capable of handling fluids under relatively high pressures.

Additionally, the hose must be substantially resistant to chemical attack by the fluid.

As disclosed in the above patent specifications, various synthetic resins have been proposed for making hoses of different compositions.

For example, the choice of synthetic resin used to make the core tube will vary depending on the hose depending on the importance of its physical properties.

For example, resinous nylon 11 is a desirable choice for core tubes that require resistance to chemical attack by fluids carried by hoses.

Unfortunately, hoses with nylon 11 core tubes are not as flexible as hoses with core tubes made of other resins such as polyurethane.

However, polyurethane is not as resistant to fluid corrosion as nylon.

As with deciding between nylon or polyurethane for the core tube, one property must be sacrificed for another.

For some hoses, it is desirable to join the core tube to a fibrous reinforcement.

Polyurethane is useful as a core tube in spliced hoses because treating the polyurethane core tube with a solvent softens its surface and forms a sticky body that joins the fibrous strands to the core tube.

However, polyurethane core tubes can only be used in hoses where the polyurethane exhibits sufficient chemical resistance for the hose to carry fluid.

Therefore, in conventional hoses, the core tube with the most desired properties has been selected and other less important properties have been allowed to be sacrificed.

Of course, this does not result in hoses with optimal properties for many industries.

The present invention has been made in view of the above points, and is an improved composite reinforced hose for conveying fluids under pressure that has the most necessary properties to function properly without significantly sacrificing other properties. The purpose is to obtain.

A further object of the invention is to provide a composite reinforcement suitable for conveying fluids under pressure, having a structure which allows greater freedom in the selection of hose components in order to adapt to the various conditions to which the hose is subjected. It's about getting the hose.

Yet another object of the present invention is to obtain a composite hose that combines optimal flexibility, kink resistance, resistance to chemical attack, and other desirable properties.

Yet another object of the present invention is to provide a composite reinforced hose with a core tube that has the good properties of a plurality of thermoplastic synthetic resins without substantially compromising other properties of the core tube.

Yet another object of the present invention is to provide a hydraulic hose which is superior to conventional hydraulic hoses, as disclosed in the applicant's Canadian Patent Application No. 217,401.
The object of the present invention is to obtain a composite reinforced hose that is further improved from that described in the specification of Japanese Patent Application No. 11051 of 1975.

The composite reinforced hose according to the present invention includes a core tube having a two-layer structure in which at least two types of thermoplastic synthetic resins having different properties are simultaneously extruded and melted and laminated together;
It consists of a fibrous reinforcing material provided around the core tube and a protective synthetic resin exterior provided outside the fibrous reinforcing material.

Thermoplastic synthetic resins suitable for forming the inner layer of the core tube include, for example, segmented copolyesters, mixtures of segmented copolyesters and thermoplastic aromatic polyesters, mixtures of polyurethane and segmented copolyesters, and thermoplastic aromatic polyesters. Mention may be made of mixtures of polyester and polyurethane, and mixtures of polyacetal and polyurethane.

Thermoplastic synthetic resins suitable for forming the outer layer of the core tube include, for example, polyvinyl chloride, segmented copolyesters, polyurethanes, and mixtures of segmented copolyesters and polyurethanes.

Next, the composite reinforced hose according to the present invention will be described in detail with reference to the accompanying drawings showing one embodiment thereof.

FIG. 1 is a fragmentary side view of a partially fractured cross section of a composite reinforced hose, and FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG. 1.

Canadian Patent Application No. 217,401 discloses that at least two layers of core tubes formed from thermoplastic synthetic resins with different physical properties are fused directly to each other at the interface in a wall that functions as a unitary structure. A composite reinforced hose is described, which is composed of a single layer or multiple layers of fibrous reinforcing material provided on the outside of the core tube, and a protective synthetic resin sheath provided on the outside of the fibrous reinforcing material. has been done.

The invention of Canadian Patent Application No. 217,401 discloses that two or more layers of different physical properties are fused together to form a single wall, such that they do not separate into layers under conditions of use as a hydraulic hose. The present invention provides a composite reinforced hose comprising the synthetic resin core tube of the above layers, a suitable fibrous reinforcing material provided on the outside of the core tube, and a protective sheath on the outer surface.

With the invention described in Canadian Patent Application No. 217,401 and the present invention, composite reinforced hoses having unique desirable properties can be produced without substantially sacrificing other desirable properties.

For example, a virtually chemically corrosion-resistant polymer, such as nylon, may be selected as the inner layer of the core tube wall, and a layer of a flexible polymer, such as elastomeric polyurethane, may be fused to the core tube inner layer as an outer surface. It is possible to obtain increased flexibility and torsion resistance.

The outer layer of the core tube can be formed of a resin that can form a sticky body when treated with a polar solvent, thereby adhesively bonding the core tube to the reinforcement and improving the strength of the hose.

In such hoses, the relative thicknesses of the nylon and polyurethane can be varied to further improve the properties of the hose.

In another aspect of the invention, the inner layer of the core tube wall is formed of a solvent-resistant thermoplastic polymer fused to the outer layer that forms the outer surface of the core tube and has particles of conductive material such as carbon black distributed thereon. , a hose for use in an airless high-pressure paint spraying device can be obtained.

A hose in which the core tube is comprised of a foam plastic or porous outer layer and a substantially non-porous inner layer fused thereto is also provided by the present invention.

The core tube is made by a method suitable for melt-bonding two different layers of thermoplastic synthetic resin together to such an extent that the two layers do not separate at the interface when the hose is stretched or otherwise subjected to conditions. .

The most practical method of core tube production is to feed two thermoplastics or two different types of the same thermoplastic from different extruders into a single extrusion head, and then When supplying the molten resin for the outer layer of the core tube wall, the resin inside the core tube is in a molten state and the two molten synthetic resins are extruded from the same extrusion die.

The two layers of the selected thermoplastic composite melt along their interfaces and adhere tightly to each other, and when the hose is used to convey fluid under high pressure, the physics of the two layers of the core tube It has been found that the core tube does not delaminate, even though the physical properties are significantly different.

For example, nylon 11 and thermoplastic polyurethane can be adhered to each other according to the method of the present invention.

The present invention therefore provides a hose consisting of a core tube having a layer of nylon 11 fused to a layer of substantially non-porous thermoplastic polyurethane.

A layer of nylon 11 is usually provided as the innermost layer due to its chemical corrosion resistance.

The polyethylene layer provides flexibility to the hose and can also be used to form an adhesive for joining the core tube to a fibrous reinforcing layer that is typically placed on the outside of the core tube.

The nylon 12 and thermoplastic polyurethane layers can be fused together.

Because of its chemical corrosion resistance, the nylon 12 layer can be used as the inner layer of the core tube with an outer thermoplastic polyurethane layer.

The present invention can also provide composite reinforced hoses having two or more layers of synthetic resin core tubes, generally having the same chemical composition but tailored to provide different physical properties. .

For example, relatively hard thermoplastic polyurethane with Shore hardness D50-60 and Shore hardness A80-95.
can be coextruded with a relatively soft thermoplastic polyurethane to form the core tube.

Hard thermoplastic polyurethanes have better chemical corrosion resistance than softer polyurethanes.

So typically a hard polyurethane is used for the inner layer of the core tube.

A soft polyurethane layer can improve the flexibility of the hose.

Another hose obtainable according to the invention includes an innermost layer of a segmented copolyester such as Hytrel having a Shore hardness of about D55 and an outer layer of a segmented copolyester such as Hytrel having a Shore hardness of about A90. It has a core tube consisting of.

Such hoses have beneficial physical properties at high temperatures.

In another embodiment of the invention, a bracing hose that is not only flexible and kink resistant but also capable of transporting fluid without contamination by the core tube has an inner layer of unplasticized nylon 11 and a plasticized nylon 11 layer. Obtained using a core tube with the outer layer.

A hose suitable for directing paint under high pressure has a core tube consisting of an inner layer of nylon 11 or nylon 12 and a thermoplastic polyurethane layer containing carbon black particles fused to the nylon 11 or nylon 12 layer. It can be obtained using

The nylon layer provides solvent corrosion resistance for transporting the paint within the core tube, and the polyurethane containing carbon black particles provides a semiconductor for conducting static charge to the ground.

As a variation of this type of hose, the inner layer may be nylon 11 and the outer layer may be nylon 11 with carbon black dispersed therein.

The core tube can be adhesively bonded to the reinforcement surface by applying an adhesive or activating the core tube surface with a solvent or softener to form a stick from the resin on the outer surface of the core tube.

For example, the polyurethane surface of the core tube can be activated by wetting it with a suitable polar solvent such as N-methylpyrrolidone.

The fibrous reinforcement is then brought into tensioned contact with the outside of the moistened core tube, causing the strands of reinforcement to become embedded and partially enclosed by the softened core tube material.

In this way, the fibrous reinforcing layer is bonded to the core tube and the strength of the hose is improved.

Hytrail is a synthetic resin sold by DuPont.

Hytrail is a segmented copolyester and is described in US Pat. No. 3,766,146.

If selected thermoplastic synthetic resins with different physical properties are co-extruded, they can be joined together by melting, without the need for an intervening adhesive.

For example, if the nylon and thermoplastic polyurethane elastomer are melted, fed separately to an extrusion head, and extruded one on top of the other while still molten, the nylon will fuse to the thermoplastic polyurethane elastomer.

If one layer of the core tube is difficult to fuse to the other, a third intermediate layer of synthetic resin that is fused to both layers can be interposed between them.

The inventors surprisingly found that a core tube with two or more layers of thermoplastic synthetic resin of different physical properties has an elongation rate approximately equal to that of the softer resin (the average value of both It was found that the resin had an elongation at break close to resins with low elongation or low elongation.

In other words, the molten layers are fused together and break at the break point of the resin that has a greater elongation.

For example, extrude a layer of nylon 11 with a thickness of 0.020 inches (0.508 mm) and while the nylon 11 is still molten, add a layer of nylon 11 with a thickness of 0.025 inches (0.635 mm) on top of the layer of nylon 11. The core tube can be made by extruding a thermoplastic polyurethane layer having a

The two layers are fused together.

Using the same equipment, 0.020 inch (0.508 m
Extrude a single-layer core tube of nylon 11 with a wall thickness of 0.025 inch (0.635 mm) and use the same core tube to repair the double extruded tube with a wall thickness of 0.025 inches (0.635 mm) Can be extruded from polyurethane.

Test samples were cut from a total of three samples and the elongation at break was measured.

Surprisingly, the elongation at break of the laminate core tube was comparable to that of the polyurethane core tube.

The measurement results obtained are as follows.

n: Number of samples tested It can be seen that this occurs only once in 2.0 times.

The composite tube elongation confidence is substantially higher than the all nylon tube range and overlaps with the all urethane tube range.

The elongation at break of the composite tube is at least 9.9 greater than that of an all-nylon 11 tube extruded under the same conditions.
% (probably 20.5%) good.

Other combinations of synthetic resins that can form core tubes with two or more layers coaxially extruded and fused together are segmented copolyesters and polyvinyl chloride, such as Hytrail, segmented copolyesters and polyvinyl chloride, segmented copolyesters and A mechanical blend of a non-porous thermoplastic polyurethane and a segmented copolyester with an aromatic polyester such as poly(tetramethylene terephthalate) in one layer and a polyvinyl chloride polymer in the outer layer.

Laminated core tubes that combine layers of high-trail or mixtures of segmented copolyesters and aromatic polyesters with layers of polyvinyl chloride or polyurethane typically have an inner layer containing the segmented copolyester. .

Mechanical mixtures of segmented copolyesters and polyurethanes can also be used in one of the layers, usually the outer layer.

The inner layer of the core tube can be comprised of a mixture comprising about 5 to about 95 weight percent polyurethane and about 95 to about 5 weight percent aromatic polyester in combination with the outer layer.

The inner layer of the core tube may be a mixture of polyacetal and polyurethane, which can be combined with the outer layer described above.

Examples of suitable thermoplastic aromatic polyesters include Valnx (trade name, aromatic polyester sold by General Electric Company), Tenite (trade name, aromatic polyester sold by Eastman Kodak Company), Celanex (trade name, aromatic polyester sold by Celanese Plastics Company) can be mentioned.

An aromatic polyester such as Valox and a segmented copolyester such as Hytrail may be blended in appropriate relative proportions and extruded to form the core tube layers.

For example, aromatic polyester such as Barox
~60% by weight can be used.

From about 99% to about 50% by weight of thermoplastic polyurethane to about 1% cosegmented polyester, although suitable mixtures of polyurethane and segmented copolyester may be used.
It is desirable to use up to about 50% by weight.

Referring to the drawings, a composite reinforced hose 10 is shown in FIGS. 1 and 2. FIG.

Composite reinforced hose 10 is approximately 0.020 inches (0.50
8 mm) and a layer of nylon 11 with a thickness of approx.
Pellethane (with a thickness of 5 inches (0.635 mm)
It has a core tube 17 formed by simultaneously extruding a thermoplastic polyurethane elastomer outer layer such as Pellethane (trade name) 90A.

The two synthetic resins are fused together at the interface to form a core tube that does not delaminate when the hose 10 is used to convey fluid under pressure.

The polyurethane outer surface of the core tube 17 is moistened with N-methylpyrrolidone to form a gel-like substance 13 on the surface.

A reinforcing layer 14 of polyethylene terephthalate ester filaments is looped under tension around the core tube, and the surface of the core tube 17 is activated with a solvent.

The filament is embedded and partially wrapped in the surface of the core tube 17 forming an elastomeric bond between the fibrous reinforcement and the core tube.

A second reinforcing layer 15 can also be provided on the reinforcing layer 14.

A protective polyurethane sheath 16 is provided on the outside of the fibrous reinforcing layer 15 by extruding a thermoplastic polyurethane elastomer.

Suitable other core tubes may be substituted for the core tube 17 of the embodiment, and the core tube 17 may or may not be bonded to the reinforcing layer depending on the particular requirements of the hose.

For example, in embodiments of the present invention, the innermost layer of core tube 17 may be comprised of a segmented copolyester such as Hytrail, and the outermost layer may be a polyvinyl chloride polymer.

Alternatively, a mechanical mixture of a thermoplastic aromatic polyester and a segmented copolyester, such as Valox 310, may be extruded as the innermost layer, and a polyvinyl chloride polymer may be extruded simultaneously to form the outermost layer of the core tube 17.

It is also possible to use a mixture of thermoplastic aromatic polyester and segmented copolyester as the innermost layer of the core tube 17 and polyurethane or segmented copolyester as the outer layer.

Alternatively, two mixtures of aromatic polyester and segmented copolyester having different proportions of components may be extruded together to form the inner and outer layers.

The polyurethane sheath 16 and the polyurethane 12 of the core tube 17 may be extruded from a suitable thermoplastic polyurethane, such as that sold under the trademark Pellethane by Absorption Company.

U.S. Patent Nos. 3,116,760 and 3,722
, No. 550, and by Messrs. Saunders and Fritsch, “Polyurethanes: Chemistry and
It is also possible to use the thermoplastic polyurethanes described in the book "Technology" published by Interscience Publications in 1964.

Poly(tetramethylene ether) glycol, 1,4-
a suitable chain extender such as butanediol and 4,4'
- reaction product with diphenylmethane diisocyanate,
and an intramolecular ester such as poly(ε-caprolactone) ester and a suitable chain extender such as 1,4-butanediol with an aromatic diisocyanate such as 4,4'-diphenylmethane diisocyanate. The resulting polyurethanes are also preferred.

Sheath 16 may also be extruded from nylon or other suitable synthetic resins such as segmented copolyester.

The fibrous reinforcement can be formed by braiding or spirally winding filaments of a suitable synthetic resin.

For example, poly(alkylene terephthalate) ester fibrous reinforcements are described in US Pat. No. 3,062,241.

The above fibers have a strength of about 7 to about 11 g/denier and about 9%
It has an elongation at break of ~17.

In a preferred embodiment of the invention, the hose comprises at least one
2g/denier and strength up to about 25g/denier and approx.
% to about 7% filament reinforcing layer is provided.

Aromatic polyamide fibers marketed by DuPont under the trade name Kevlar and known to those skilled in the art as fiber B and as alumid filaments may also be used.

A suitable reinforcing material comprising synthetic aromatic polyamide filaments is disclosed in our Canadian Patent Application No. 217,239.
(corresponding to Japanese Patent Application No. 11049 of 1975) and Canadian Patent Application No. 217,401 (corresponding to Japanese Patent Application No. 11051 of 1975).

Aromatic polyamide fiber fibrous reinforcements are preferred for composite hoses with high burst strength.

The core tube can be formed by extrusion using a suitable extrusion device having a separate extruder for feeding the thermoplastic synthetic resin into one extrusion head.

In one embodiment of the invention, 3/8 inch (9.5 2 5
The hose, having a core tube 17 with an inner diameter of 1.5 mm), has an inner layer extruded from a mixture comprising about 90 parts of Hytrail segment copolyester and about 10 parts of Valox 310 poly(tetramethylene terephthalate) ester.

Approximately 0.010 inch (0.254 mm) coaxially extruded with a mixture of High Trail and Barox
A thermoplastic polyurethane layer having a thickness of .

A single reinforcing layer 14 of knitted fibers of polyethylene terephthalate ester is provided around the core tube 17 and bonded thereto.

The fibrous reinforcing layer is adhered to the core tube 17 by dissolving the polyurethane surface with N-methylpyrrolidone and weaving the fibers into the wet core tube.

Approximately 0.025 inches (0.635 mm) of polyurethane sheath 16 is extruded onto the outside of reinforcing layer 14 and bonded thereto.

The resulting hose is 0.65 inch (16.51 mm)
with an outer diameter of approximately 10,000 psi and a burst strength of approximately 10,000 psi.
Can be bent to a radius of 75 inches (19.05 mm) without twisting.

Hoses with single layer nylon core tubes and hoses identical to those described above have approximately 1.75
It has a minimum bend radius of inches (44.45 mm).

It takes approximately 12 pounds (5.44 kg) to bend the hose of the present invention 180° around a 21/4 inch (57.15 mm) radius, having a core tube consisting of a high-trail and barox inner layer and a polyurethane outer layer. ) to bend a hose with a single-layer nylon core tube in the same way
load is required.

In another embodiment of the invention, the hydraulic hose is 1 inch (2
It has a core tube 17 with an inner diameter of 5.4 mm).

The core tube 17 consists of 0.04 parts of a mixture of 85 parts of Hytrail segment copolyester and 15 parts of Valox 310 polytetramethylene terephthalate ester.
5 inch (1.143 mm) thick inner layer and approx.
It can be formed by simultaneously coextruding a 0 inch (0.762 mm) thick outer layer of polyvinyl chloride polymer.

A single reinforcing layer 14 of poly(ethylene terephthalate) ester fibers is woven around core tube 17 and adhered to core tube 17 using a solution of about 18 parts polyurethane dissolved in 82 parts methylene chloride solvent. .

A polyurethane sheath 16 is extruded onto the outside of the fibrous reinforcing layer 14 and adhered thereto.

The outside diameter of the hose is approximately 1.45 inches (36.83 mm).

Bursting strength is about 6800 psi and minimum bend radius without twisting is about 4 inches (101.6 mm).

The hose has a 41/2 inch (114.3 mm) radius and a 22 pound (998 kg) load.
It has an 80° bend and is more flexible than a hose with a single layer nylon core tube as demonstrated by the fact that a 31 pound (14.06 kg) load is required to bend the same way for a hose with a nylon core tube.

As is clear from the above description, the composite reinforced hose obtained by the present invention is superior to conventional hoses and has unique physical properties without substantially sacrificing other properties of the hose. Some synthetic resin can be applied to the core tube where it is most needed.

For example, the synthetic resin for the inner layer of the core tube may be selected for chemical corrosion resistance, or may be selected to obtain a hose that has both chemical corrosion resistance and tensile strength;
Also, a softer synthetic resin can be selected for the outer layer of the core tube to maintain overall flexibility.

In the present invention, the thickness of the layers of the core tube can also be varied to obtain a hose with specific properties.

The layers of the core tube can also be selected to provide novel combinations of properties such as chemical corrosion resistance and conductive columns or insulation.

The cost of the hose can also be reduced by using only a relatively thin layer of expensive but desirable synthetic resin only on the surfaces of the core tube where it is needed.

A substantially non-porous synthetic resin layer can also be obtained in combination with a foam layer, such as a polyurethane foam layer.

By appropriately selecting the combination of resin layers used in the core tube, torsion resistance can also be achieved in cooperation with the reinforcement bonded to the sheath.

Although the present invention has been described in detail for the purpose of disclosure, such details are solely for the purpose of disclosure and will not be understood by those skilled in the art to understand the spirit of the invention, other than as limited by the scope of the claims. It goes without saying that various modifications are possible within this range.

[Brief explanation of the drawing]

The drawings show an embodiment of the composite reinforced hose according to the present invention, and FIG. 1 is a fragmentary side view of a partially fractured cross section of the composite reinforced hose, and FIG. 2 is a diagram taken along the line ■-■ in FIG. 1 is a cross-sectional view of a composite reinforced hose along the 10... Composite reinforced hose, 11... Nylon, 12... Thermoplastic polyurethane elastomer, 13... Gel-like substance, 14...
・Reinforcement layer, 15...Second reinforcement layer, 16...
...Polyurethane exterior, 17...Core tube.

Claims (1)

[Claims] 1 Consisting of a core tube, a fibrous reinforcing material provided around the core tube, and a protective sheath provided outside the fibrous reinforcing material, the core tube having different It has a two-layer structure in which at least two types of thermoplastic synthetic resins having the properties are co-extruded and directly melted and layered together,
The core tube may consist of an inner layer of an A-segment copolyester and an outer layer of polyvinyl chloride, or an inner layer of a mixture of a B-segment copolyester and a thermoplastic aromatic polyester and polyvinyl chloride, a segment copolyester, a polyurethane or a segment. (c) an inner layer of a mixture of polyurethane and segmented copolyester and an outer layer of polyurethane; (d) an inner layer of a mixture of thermoplastic aromatic polyester and polyurethane; an outer layer of vinyl chloride, segmented copolyester, polyurethane or a mixture of segmented copolyester and polyurethane; or an inner layer of polyvinyl chloride, segmented copolyester, polyurethane or segmented copolyester; Composite reinforced hose for conveying fluids under pressure, characterized in that it consists of an outer layer of a mixture with polyurethane. 2. The composite reinforced hose according to claim 1, wherein the inner layer of the core tube is made of segmented copolyester, and the outer layer of the core tube is made of polyvinyl chloride. 3. Claims in which the inner layer of the core tube is a mixture of segmented copolyester and thermoplastic aromatic polyester, and the outer layer of the core tube is polyvinyl chloride, segmented copolyester, polyurethane, or a mixture of segmented copolyester and polyurethane. The composite reinforced hose according to item 1. 4. The composite reinforced hose of claim 1, wherein the core tube has an innermost layer of a mixture of segmented copolyester and polyurethane and an outer layer of polyurethane. 5. The composite reinforced hose according to claim 1, wherein particles of a conductive substance are distributed in the outermost layer of the core tube. 6. The core tube according to claim 1, wherein the core tube has an inner layer of a mixture of thermoplastic aromatic polyester and polyurethane and an outer layer of polyvinyl chloride, segmented copolyester, polyurethane, or a mixture of segmented copolyester and polyurethane. Composite reinforced hose. 7. The composite reinforced hose of claim 1, wherein the core tube has an inner layer of a mixture of polyacetal and polyurethane and an outer layer of polyvinyl chloride, segmented copolyester, polyurethane or a mixture of segmented copolyester and polyurethane. 8. A composite reinforced hose according to claim 1, wherein the reinforcing material is joined to the outer layer of the core tube. 9 Claim 1 in which the exterior is joined to the reinforcing material
Composite reinforced hose as described in section. 10. The composite reinforced hose according to claim 8, wherein the exterior is joined to a reinforcing material.