JP2010275156A - Cement molded body reinforcing fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cement molded body reinforcing fiber which can be defibrated and uniformly dispersed in a short time without performing mechanical stirring for a long time upon kneading a cement molded body material such as cement paste, mortar and concrete, not even in the case including kneading water, but also, in the case of dry blending including no kneading water, and can impart an excellent reinforcing effect without damaging the fluidity in being fresh of a cement molded body. <P>SOLUTION: The cement molded body reinforcing fiber is a short fiber to which a treatment agent composed of a polycarboxylic acid ether based anionic compound and polyalkylene glycol is imparted. The total coating weight of the treatment agent is 0.5 to 20 wt.% by a solid content ratio, further, the single yarn fineness of the short fiber is 0.5 to 100 dtex, and also, the aspect ratio of the short fiber is 50 to 1,000. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fiber for reinforcing a cement molded body having excellent dispersibility and excellent reinforcing effect without impairing the fluidity of the cement molded body when fresh.

  Conventionally, cement paste, mortar, concrete, and the like, which are cement molded bodies, are excellent in compressive strength, durability, incombustibility, and the like, and are inexpensive, and thus are used in large quantities for construction civil engineering. However, since it is a brittle material that causes drying shrinkage when it is cured and has a low tensile and bending strength, various kinds of materials are used for the purpose of suppressing cracking and improving mechanical properties such as bending strength and toughness. Blending a fibrous material is a known technique and many have been proposed.

  However, it is extremely difficult to uniformly disperse fibers in cement molded body materials including cement, fine aggregates, coarse aggregates, etc., and single yarns are entangled or curved during material kneading. There is a problem that a ball is generated and it is difficult to obtain a target reinforcing effect. Further, even if the fibers are uniformly dispersed in the cement molded body, there is a problem that the fluidity of the cement molded body when fresh is significantly reduced due to the binding force of the fibers.

  In order to solve such a situation, it has been proposed to use as a reinforcing material a bundling yarn in which a plurality of fibers are bonded and integrated with a bundling agent, and a bundling yarn obtained by bonding a plurality of fibers with a thermosetting resin. (For example, refer to Patent Document 1).

  When such a bundling yarn is used, it is first dispersed in the cement molding material in the form of a bundling yarn, and then the resin is detached due to friction or shearing force with a stirring blade or material in the stirrer, resulting in a bundling state. Gradually dislodges into multiple single yarns and disperses. Therefore, it has a feature that it is excellent in uniform dispersibility as compared with the case of mixing unfocused fibers.

  However, since this bundling yarn is firmly bonded with a thermosetting resin, it is difficult to sufficiently defibrate without stirring for a long time with a high shear force by a kneader as described above. It was. The fiber is defibrated by stirring, but when it is stirred for a long time, the fiber that has already been defibrated forms a fiber ball while continuing to stir in order to defibrate the undefibrated fiber. When the balls are formed, there is a problem that the reinforcing effect is impaired.

  For this reason, the sizing agent has been improved, and a technology has been disclosed in which a specific water-soluble polymer resin is used as a sizing agent to achieve a defibration degree of PH 12 of 50% or more (see Patent Document 2). According to this bundled yarn, the degree of defibration was excellent, the dispersibility was excellent, and the fiber ball was hardly formed.

  However, since the sizing agent is a water-soluble polymer resin, it dissolves after the resin is released while being stirred in the cement molding material, resulting in a thickening effect and reducing the fluidity of the cement molding when fresh. There was a problem to do.

  Moreover, in order to suppress the fluidity | liquidity fall at the time of the freshness of the cement molded object by fiber addition, what bundled the fiber with the concrete admixture called a water reducing agent is disclosed (refer patent document 3). Certainly, the effect of the water reducing agent can suppress a decrease in fluidity of the cement molded body when fresh due to the addition of the fiber, but there is a problem that the fiber surface of the water reducing agent makes it difficult to open the fiber.

  In addition, as a kneading procedure of the cement molded body material, in recent years, premix material in which powder components such as cement, fine aggregate, coarse aggregate and reinforcing fibers are mixed, and then mixing with mixing water, It has come to be favorably performed in terms of eliminating measurement labor and measurement errors at the construction site.

  Therefore, in both the premix method and the normal mix method, there is a demand for a fiber for reinforcing a cement molded body that can be defibrated and dispersed uniformly in a short time with a weak stirring force. It was not something that could be met.

Japanese Examined Patent Publication No. 62-21743 JP-A-10-183473 JP-A-8-259289

  The present invention solves the above-mentioned problems, and when kneading cement molded body materials such as cement paste, mortar, and concrete, particularly in the case of a dry premix, without mechanical stirring for a long time, An object of the present invention is to provide a fiber for reinforcing a cement molded body that can be defibrated and uniformly dispersed in a short time and can give an excellent reinforcing effect without impairing the fluidity of the cement molded body when fresh. To do.

  As a result of intensive studies, the present inventors have determined that the surface of the cement particle is cationic, so that the affinity for the cement / fiber interface is increased by making the surface of the reinforcing fiber for cement molding anionic. It was found that the fluidity of the cement molded body when fresh was not impaired. Further, it has been found that by reducing the static friction force between the fibers, when shearing by kneading is applied to the reinforcing fibers, the fibers are not lumped and are easily defibrated and easily dispersed uniformly in the cement molded body. Therefore, if the cement molded body reinforcing fiber is provided with a polycarboxylic acid ether-based anionic compound having an electrostatic adsorptive action with cement particles and a polyalkylene glycol effective in improving the smoothness between the short fibers, the above problem Has been found to solve the problem, and the present invention has been completed.

That is, according to the present invention,
A short fiber to which a treatment agent comprising a polycarboxylic acid ether-based anionic compound and a polyalkylene glycol is added in an amount of 0.5 to 20% by weight based on the total fiber weight, and the fiber yarn / thread static friction coefficient (F / Fμs) is 0.4 or less, the single fiber fineness of the short fibers is 0.5 to 100 dtex, and the aspect ratio of the short fibers is 50 to 1000,
Is provided.
The short fiber is preferably a copolyparaphenylene • 3,4′-oxydiphenylene • terephthalamide fiber.

  The fiber for reinforcing a cement molded body of the present invention has good fiber dispersibility regardless of the kneading procedure of the raw material, does not impair the fluidity of the cement molded body when fresh, and maintains it within a range that does not hinder construction, And a high reinforcement effect can be provided.

It is the schematic of the measuring apparatus of a thread | yarn / thread static friction coefficient.

Hereinafter, the present invention will be described in detail.
The present invention is illustrated by the following preferred examples, but is not limited thereto.

  The cement of the cement molded body used in the present invention can be selected in consideration of on-site construction conditions and the like, and is not particularly limited. For example, early strong, very early strong, low heat, moderate heat, etc. These various Portland cements, various mixed cements such as blast furnace cement obtained by mixing fly ash, blast furnace slag, and the like with these various Portland cements, fast-hardening cements and the like can be used alone or in combination of two or more.

  Also, the cement includes known blast furnace slag powder, fly ash, silica fume, limestone powder, quartz powder, dihydrate gypsum, hemihydrate gypsum, anhydrous gypsum, quick lime-based expansion material, calcium sulfoaluminate-based expansion material, and the like. Of admixture can be added. The blending ratio is not particularly limited and can be appropriately designed.

  As the aggregate of the cement molded body used in the present invention, only fine aggregates such as river sand, sea sand, mountain sand, crushed sand, No. 3-8 silica sand, limestone, and slag fine aggregate, and according to the required characteristics of the application In addition, coarse aggregates such as river gravel, crushed stone, and artificial aggregate can be mixed and used. In order to express high physical properties, it is preferable to use only fine aggregates such as silica sand and limestone whose particle size is adjusted without containing fine powder or coarse aggregates. Furthermore, in order to obtain a hardened cement body having desired characteristics, the particle size constitution and blending ratio also have a suitable range, and the aggregate particle size is preferably 4 mm or less, and less than 1.2 mm is 40 to 40 mm. More preferred is a mixture of 75% and 1.2 to 4 mm 60 to 25%, less than 1.2 mm 55 to 70% and 1.2 to 4 mm 45 to 30%. A mixture is most preferred. When the maximum particle size exceeds 4 mm, the fluidity and filling properties are insufficient, and those with 1.2 to 4 mm may be inferior in durability when less than 25%, and when they exceed 60%, the required early strength cannot be obtained. There is.

  Further, the cement molded body used in the present invention is kneaded by adding an appropriate amount of kneaded water, but if the kneaded water does not contain a component that adversely affects the hardening of cement or the like, tap water or ground water, Water such as river water can be used, and for example, one suitable for “JIS A 5308 Appendix 9 Water used for mixing ready mixed concrete” is preferable.

  The polycarboxylic acid ether-based anionic compound used in the present invention may be one that is currently sold in the general market as a dispersant for cement particles, and one having an average molecular weight of 1,000 to 200,000 is usually used.

  The polyalkylene glycol used in the present invention is obtained by polymerizing or copolymerizing alkylene oxides such as ethylene oxide and propylene oxide, and usually has a number average molecular weight of 2000 or less, preferably 400 to 1000. When the molecular weight exceeds 2000, the viscosity of the solid content of the polyalkylene glycol is high, the static friction force between the fibers is increased, and the reinforcing fibers are not easily defibrated. Specific examples include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

  The total adhesion amount of the polycarboxylic acid ether-based anionic compound and the polyalkylene glycol needs to be 0.5 to 20% by weight with respect to the total weight of the cement molded body reinforcing fiber. When the amount is less than 0.5% by weight, excellent dispersibility of the reinforcing fibers cannot be obtained when the cement molded body material is kneaded, and the fluidity during freshness is low. On the other hand, when it exceeds 20% by weight, the fiber and other cement molded material may be separated or moisture may be excessively bleed out due to the influence of the treatment agent. Preferably, it is good to adhere in the range of 1.0-10.0 weight%.

  The mixing ratio of the polycarboxylic acid ether anionic compound and the polyalkylene glycol is appropriately selected depending on the fiber dispersibility at the time of kneading the material and the fluidity at the time of fresh cement molding, but the polycarboxylic acid ether anionic compound The weight ratio of / polyalkylene glycol is preferably 20/80 to 80/20. When the amount of the polycarboxylic acid ether-based anionic compound exceeds the above range, the static friction force between the fibers becomes large, and the reinforcing fibers are difficult to be defibrated. Conversely, when the amount of polyalkylene glycol exceeds the above range, the affinity with cement particles is low, and the fluidity of the cement molded body when fresh is lost.

  Next, the reinforcing fiber for cement molded body of the present invention needs to have a yarn / thread static friction coefficient (F / F μs) of 0.4 or less in order to facilitate dispersion of the fiber when a shearing force is applied. Yes, preferably 0.35 or less. When the yarn / thread static friction coefficient (F / F μs) exceeds 0.4, the fiber is difficult to disperse when the shearing force applied to the fiber is small, which is not preferable. The lower limit of the thread / thread static friction coefficient (F / F μs) is not particularly limited.

Further, the yarn / thread static friction coefficient (F / F μs) in the present invention is a measuring device as shown in FIG. 1, and one end of the fiber (3) is fixed to the U gauge (2), and the pulley (1) And then twisting twice and pulling with an initial load (T1) of 1000 g. The crossing angle (θ) between the yarns / yarns is 15 °, the temperature of the twist portion is kept at 20 ° C., and the U gauge (2) is pulled at a speed of 0.1 m / min. At that time, the tension (T2 g) sensed by the U gauge (2) is measured, and the static friction coefficient is calculated by the following formula as the ratio of the stress T2 to the initial load T1.
F / F μs == 1.40 Log 10 (T2 / T1)

  As a method for adhering the polycarboxylic acid ether-based anionic compound and the polyalkylene glycol to the fiber, there are a multifilament long fiber in which single fibers are gathered, a shape in which a plurality of the filaments are aligned, and a tow-like long fiber. Is continuously fed from a bobbin or a beam creel, and the treatment agent is sprayed by a method of impregnating in a bag containing the treatment agent, a method of attaching by a roller touch method, or a spray method. Although the method of making it adhere | attach etc. is mentioned, in order to make it adhere uniformly to a fiber, the method of immersing in the bath containing this processing agent is preferable, and what is necessary is just to adjust to a fixed adhesion amount with a squeeze roll.

  And after giving polycarboxylic-acid-ether type | system | group anionic compound and polyalkylene glycol, it is preferable to give a drying process, It does not specifically limit as an apparatus, Although a contact-type hot roller etc. can be used. When a non-contact type heat drying furnace is used, the processing agent is not attached to the apparatus or contaminated, and the operation is easy. Moreover, it is preferable to dry at about 105-200 degreeC as a process temperature at this time, especially about 120-180 degreeC. Next, the obtained tow-like fiber material may be cut by a known cutting machine so as to have a predetermined fiber length. It should be noted that the amount of the treatment agent deposited hardly changes even if the treatment is performed as described above and then dried.

  The single fiber fineness of the reinforcing fiber for cement molded body of the present invention is 0.5 to 100 dtex, and the aspect ratio of the short fiber is 50 to 2000. The reinforcing effect due to fiber mixing, that is, cracking suppression, high bending strength and high This is preferable from the viewpoint of imparting bending toughness. When the single yarn fineness is less than 0.5 dtex, since the cement is alkaline, the fiber is deteriorated to the vicinity of the fiber core, the decrease in the tensile strength of the fiber is increased, and the desired reinforcing effect may not be obtained. On the other hand, when it exceeds 100 dtex, the spread to the details of the fibers becomes insufficient, and when the short fibers are added with the same volume content, the number of single fibers decreases and a sufficient reinforcing effect cannot be obtained. Preferably it is 1-60 dtex, More preferably, it is 1-50 dtex.

  Further, if the aspect ratio of the short fiber for reinforcing a cement molded body of the present invention is less than 50, the reinforcing effect by adding the fiber may not be obtained in strength and toughness. In addition, when it exceeds 2000, short fibers are entangled or finely broken during kneading, and the fluidity at the time of fresh cement molding is deteriorated, impairing the workability, or the expected reinforcement effect due to the addition of fibers cannot be obtained. Occurs. Preferably, the single fiber fineness of the short fibers is 0.75 to 75 dtex, and the aspect ratio is 100 to 1000.

  Moreover, the fiber mixing rate of the said cement molded object reinforcement fiber can be selected according to the objective, and it is preferable to use in the range of 0.01-10.0 volume%. If the fiber mixing rate is less than 0.01% by volume, crack cracking, strength, and toughness may not be sufficient. On the other hand, if it exceeds 10.0% by volume, fiber single yarns are entangled with each other, resulting in fiber balls, Dispersion of fibers is incomplete, the fluidity of the cement molded body when fresh is impaired, not only hindering workability during construction, but also because a reinforcing effect and toughness improving effect commensurate with the fiber mixing rate cannot be obtained, which is preferable Absent. In particular, the fiber mixing rate is preferably 0.05 to 5.0% by volume.

Here, the fiber mixing ratio (Vf: fiber volume fraction) in the present invention is a ratio (volume%) represented by the following equation.
Vf = (V1 / V2) × 100
[In the formula, V1 represents the volume (liter) of reinforcing fibers mixed in the unit volume (1,000 liters = 1 m ³ ) of the cement-molded body containing fibers, and V2 represents the unit volume of the cement-molded body (1,000 liters = 1 m ³ ). 1,000 liters = 1 m ³ )

Examples of the reinforcing fiber for cement molding of the present invention include carbon fibers, glass fibers, steel fibers, ceramic fibers, asbestos fibers, and the like, aramid fibers, vinylon fibers, polypropylene fibers, polyethylene fibers, polyarylate fibers, polybenzoxazoles. Organic fibers such as (PBO) fiber, nylon fiber, polyester fiber, acrylic fiber, vinyl chloride fiber, polyketone fiber, cellulose fiber, and pulp fiber can be used, and these are used alone or in combination of two or more. be able to. Of these, fibers made of para-aramid such as polyparaphenylene terephthalamide and copolyparaphenylene 3,4'oxydiphenylene terephthalamide are preferable because they have a greater reinforcing effect than other fibers, particularly copolyparaphenylene-3. , 4 'oxydiphenylene terephthalamide short fiber is less deteriorated in mechanical properties even when kept in a strong alkaline atmosphere under high temperature and high pressure for a long time. Steam curing under high temperature and high pressure, for example, 180 ° C, pressure It is preferable because it has a high strength retention even under a condition of saturated steam of about 10 kg / cm ² .

  In cement molded products, in addition to the above materials, AE water reducing agent, high performance AE water reducing agent, shrinkage reducing agent, setting retarder, curing accelerator, thickener, antifoaming agent, foaming agent, rust preventive agent, antifreeze Additives such as an agent, a clay mineral-based thixotropic agent, a colorant, and a water retention agent can be used within a range that does not substantially impair the object of the present invention.

  The method for adding the cement-molded body reinforcing fiber of the present invention to the cement-molded body material is not particularly limited. For example, when used for reinforcing mortar or concrete, cement and fine aggregate, A method of kneading after adding a coarse aggregate and the fiber for reinforcing a cement molded body of the present invention to a dry premix and then kneading and adding water, or mixing cement and fine aggregate, coarse aggregate, etc. After sufficiently stirring, a method of adding and kneading the cement molded body reinforcing fiber of the present invention may be mentioned.

  The kneading machine used for stirring the material containing the reinforcing fiber for cement molded body of the present invention is not particularly limited, and examples thereof include a bread mixer, a tilting mixer, an omni mixer, a Hobart mixer, and a truck mixer. It is done.

  The use of cement molded bodies such as cement paste, mortar, concrete, etc., in which the fibers for reinforcing cement molded bodies of the present invention are blended is not particularly limited, and can be applied to general civil engineering and architectural uses. For example, a wide range of applications such as slope reinforcement and foundations of building structures can be given by spray molding, press molding, vibration molding, centrifugal molding, and the like. Production of secondary product molded products (blocks, plates, sheets, tetrapots, etc.) can also be performed by various molding methods.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
Various evaluations in the examples were measured as follows.

(1) Fiber length and fineness Measured according to JIS-L-1015.

(2) Fiber yarn / Thread static friction coefficient (F / Fμs)
Measurement and calculation were performed by the method described above.

(3) Fiber dispersibility evaluation method by dry premix of powder components for cement and fine aggregates and fibers for reinforcing cement moldings 700 g of ordinary Portland cement (Sumitomo Osaka Cement Co., Ltd.), 1400 g of quartz sand 5 and cement molding Fiber dispersibility in dry premix powder obtained by kneading 15 g of body reinforcing fibers with a mortar mixer (manufactured by Marui, MIC-362, volume: 5 L) at a stirring speed of 140 rpm for about 1 minute In the case of no fiber entanglement and no fiber ball was produced, it was determined to be good, and a fiber entanglement or a fiber ball produced was regarded as defective.

(4) Measuring method of flow value indicating fiber dispersibility and flowability of mortar in reinforcing fiber-added mortar 400 g of water is added to the above-obtained fiber-added dry premix powder for reinforcing a cement molded body, and mortar About the fiber dispersibility in the mortar obtained by kneading for about 3 minutes at a stirring speed of 140 rpm using a mixer (manufactured by Marui Co., Ltd., MIC-362 type, volume: 5 L), the fibers are uniformly dispersed without entanglement of fibers. And when the work at the time of construction was not obstructed, it was judged as good, and when there was entanglement of fibers or when the work at the time of construction was obstructed, it was judged as defective. Next, a mortar flow test is performed based on JIS-R-5201. When the circular distorted mortar diameter is distorted, an arithmetic average of the shortest diameter and the longest diameter is calculated as a flow value. The larger the flow value, the higher the fluidity of the mortar. However, if the flow value of the reinforcing fiber-added mortar is 80% or more of the flow value of the fiber-free mortar, the fluidity is high and less than 80%. Judge that the liquidity is low. However, the longest diameter is in the range of 1 to 2 times the shortest diameter, and if it exceeds 2 times, it is determined that measurement is impossible and fluidity is low.

(5) Method of measuring bending strength of reinforcing fiber-added mortar The above-obtained cement-molded body reinforcing fiber-added mortar was cast into a mold having a width of 40 mm, a height of 40 mm, and a length of 160 mm. A specimen for flexural strength measurement was manufactured by curing with% RH for 28 days. The specimen was measured according to a three-point bending measurement method. That is, using a tensile compression tester for 10 tons (made by TOYO BALDWIN, UNIVERSAL TESTING INSTRUMENT MODEL UTM 10t), compress the center at a distance of 10 cm between fulcrums at a speed of 2 mm / min, and obtain the bending strength from the highest point of stress. It was. Also, the fracture energy required for breaking the specimen is calculated from the relationship between the bending stress and strain, the bending strength is 12 N / mm ² or more and the breaking energy is 5 kN / mm or more, and the bending strength is 12 N / mm ² or the breaking energy. 5 kN / mm or less was regarded as defective.

[Example 1]
Aramid fiber (“Technola” manufactured by Teijin Techno Products Co., Ltd., single yarn fineness 1.7 dtex, number of fibers 1000), polycarboxylic acid ether anionic compound (“Mighty 21LV” manufactured by Kao) / polypropylene glycol (manufactured by Matsumoto Yushi) , Number average molecular weight = 700) After dipping in an aqueous solution (formulation weight ratio 50/50, aqueous solution concentration 15%), it is dried at 120 ° C. to prepare an agent-treated yarn having a treatment agent adhesion amount of 3%. The yarn / yarn static friction coefficient (F / Fμs) was measured and calculated. The agent-treated yarn obtained above was cut into 6 mm to obtain reinforcing fibers.

  700 g of ordinary Portland cement (manufactured by Sumitomo Osaka Cement Co., Ltd.), 1400 g of silica sand No. 5 and 15 g of the above reinforcing fiber were mixed at a stirring speed of 140 rpm using a mortar mixer (manufactured by Marui, MIC-362 type, capacity: 5 L). Kneaded for about 1 minute to prepare a cement molded body to which short fibers have been added, fiber dispersibility during dry premixing, fiber dispersibility and flowability during fresh fiber addition mortar, bending strength and fracture Energy was evaluated. The results are shown in Table 2.

[Examples 2 to 5, Comparative Examples 1 to 8]
In Example 1, the treatment agent, the blending ratio of the treatment agents, and the amount of the treatment agent attached to the fibers were changed as shown in Table 1, and the evaluation of the fiber yarn / thread static friction coefficient (F / F μs) was performed. The fibers were adjusted, the fiber dispersibility during the dry premix, the fiber dispersibility of the reinforcing fiber-added mortar and the fluidity during freshness, the bending strength and the breaking energy were evaluated, and the results are shown in Table 2.

[Example 6]
In Example 1, cement, silica sand and kneading water were added and stirred sufficiently, and finally the cement molded body reinforcing fiber of the present invention was added and kneaded. The results are shown in Table 2.

[Example 7]
In Example 1, it carried out by the same method except having used polyethyleneglycol (made by Matsumoto Yushi, number average molecular weight 1000) instead of polypropylene glycol. The results are shown in Table 2.

  The fiber for reinforcing a cement molded body according to the present invention has high smoothness between short fibers, good dispersibility is obtained in a dry premix with powder components such as cement and fine aggregate, and further mixing water is added. As a mortar, the dispersibility remains unchanged and the fluidity is maintained without impeding construction. Moreover, since the fibers were uniformly dispersed, it was confirmed that the reinforcing effect was high. Even when dry premixing was not performed, the fibers were uniformly dispersed, good mortar fluidity was obtained, and the reinforcing effect was high.

  When kneading cement molding materials such as cement paste, mortar, concrete, etc., not only when mixing water is included, but also when using dry blends that do not include mixing water, mechanical stirring is not performed for a long time. Since it can be defibrated and dispersed uniformly over time, it is useful as a lightweight, high-strength cement molded product.

1: Pulley 2: U gauge 3: Fiber

Claims (4)

  It is a short fiber to which a treatment agent comprising a polycarboxylic acid ether-based anionic compound and a polyalkylene glycol has been applied, and the total amount of the treatment agent to be applied is 0.5 to 20% by weight in solid content ratio. A featured fiber for cement molding reinforcement.   The fiber for reinforcing a cement-molded article according to claim 1, wherein the fiber has a yarn / thread static friction coefficient (F / F µs) of 0.4 or less.   The fiber for reinforcing a cement molded body according to claim 1 or 2, wherein the single fiber fineness of the short fiber is 0.5 to 100 dtex, and the aspect ratio of the short fiber is 50 to 1000.   4. The cement-molded body reinforcing fiber according to claim 1, 2 or 3, wherein the short fiber is a copolyparaphenylene 3,4'-oxydiphenylene terephthalamide fiber.

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