High modulus fiberglass composition

Abstract

A high modulus glass composition is disclosed that is substantially free of lithium and rare earth oxides (Re2O3), while also achieving a Young's modulus of greater than or equal to 94 GPa.

Description

HIGH MODULUS FIBERGLASS COMPOSITIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 694,928, filed: 16 September 2024, and titled: High Modulus Fiberglass Composition, which is incorporated herein by reference in its entirety for all purposes.BACKGROUND OF THE INVENTION

[0002] Glass fibers are manufactured from various raw materials combined in specific proportions to yield a desired composition, commonly termed a “glass batch.” This glass batch may be melted in a melting apparatus and the molten glass is drawn into filaments through a bushing or orifice plate (the resultant filaments are also referred to as continuous glass fibers). A sizing composition containing lubricants, coupling agents and film-forming binder resins may then be applied to the filaments. After the sizing is applied, the fibers may be gathered into one or more strands and wound into a package or, alternatively, the fibers may be chopped while wet and collected. The collected chopped strands may then be dried and cured to form dry chopped fibers, or they can be packaged in their wet condition as wet chopped fibers.

[0003] The composition of the glass batch, along with the fiberglass manufactured therefrom, is often expressed in terms of the oxides contained therein. Numerous types of glasses may be produced by varying the presence or absence of particular oxides or varying particular oxide relationships and ratios within a glass batch. Examples of such glasses that may be produced include R-glass, E-glass, S-glass, A-glass, C-glass, ECR-glass, and more recently, high performance glass (i.e., high modulus and / or high strength glass). The glass composition controls the forming and product properties of the glass. Other characteristics of glass compositions include the raw material cost and availability and environmental impact.

[0004] For instance, high performance glass fibers possess higher strength and stiffness, compared to traditional E-glass fibers. In particular, for some products, stiffness is crucial for modeling and performance. For example, composites, such as wind blades, prepared from glass fibers with good stiffness properties would allow for longer wind blades on electrical generating wind stations while keeping flexure of the blade within acceptable limits.Conventionally, lithium is added to glass fiber compositions to obtain both desirable mechanical and forming properties. For example, lithium is very effective in reducing the viscosity of the glass formulation.

[0005] Although lithium-containing glass compositions may possess desirable qualities with respect to mechanical and forming properties, there are various considerations that make it desirable to reduce and / or eliminate lithium in a glass composition, such as cost, ability to source lithium-containing raw materials, etc.

[0006] Accordingly, glass compositions that reduce or eliminate lithium and limit expensive raw materials such as rare earth oxides are desired that are nonetheless capable of producing high mechanical performance (z.e., high Young’s modulus) glass fibers, while maintaining desirable forming properties (e.g., fiberizing temperature).SUMMARY OF THE INVENTION

[0007] Various exemplary aspects of the present inventive concepts are directed to a high modulus glass composition. The glass composition includes the following:SiO2 in an amount of from 50 wt.% to 62 wt.%;AI2O3 in an amount of from 18 wt.% to 35 wt.%, such as from 20 wt.% to 35 wt.%;CaO in an amount of from 0 to 12 wt.%;MgO in an amount of greater than or equal to 18 wt.%, such as at least 20 wt.%;Na2O+K2O in a total amount of from 0 to 0.5 wt.%; andZrCh in an amount of from 0 to 2 wt.%; wherein a total concentration of AI2O3 and MgO is greater than 38 wt.% and a ratio of SiO2 to MgO is from 2.6 to 3.1, such as, for example, 2.9 to 3.05. The glass composition includes less than 0.05 wt.% of lithium and rare earth oxides (Re2O3). A glass fiber formed from the glass composition has a Young’s modulus of greater than or equal to 94 GPa, and in some aspects, greater than or equal to 95 GPa.

[0008] According to certain aspects, the glass composition includes at least 20 wt.% MgO, and at least 20 wt.% AI2O3.

[0009] The glass composition is preferably free, or substantially free of lithium (e.g., Li2O) and / or rare earth oxides (Re2O3).

[0010] According to any aspect, the glass composition may comprise:S1O2 in an amount of from 54 wt.% to 59 wt.%;AI2O3 in an amount of from 20 wt.% to 25 wt.%;CaO in an amount of from 4 to 7 wt.%;MgO in an amount of from 18 wt.% to 20 wt.%;Na2O+K2O in a total amount of from 0.01 to 0.25 wt.%; andZrCh in an amount of from 0.5 to 1 wt.%; wherein a total concentration of AI2O3 and MgO is at least 40 wt.% and a ratio of SiO2 to MgO is from 2.9 to 3.05.

[0011] The glass composition has a fiberizing temperature that is less than it’s liquidus temperature and preferably less than 1,300 °C. According to certain aspects, the glass composition has a forming gap (difference between a fiberizing temperature and a liquidus temperature) that is less than -10 °C.

[0012] Further exemplary aspects of the present inventive concepts are directed to a lithium-free, high modulus glass composition that includes the following:SiO2 in an amount of from 54 wt.% to 59 wt.%;AI2O3 in an amount of from 18 wt.% to 35 wt.%;CaO in an amount of from 0 to 12 wt.%;MgO in an amount of greater than or equal to 18 wt.%;Na2O+K2O in a total amount of from 0 to 0.2 wt.%; andZrO2 in an amount of from 0 to 2 wt.%.The glass composition includes a total concentration of AI2O3 and MgO that is greater than 38 wt.% and is free or substantially free of lithium and rare earth oxides (Re2O3). The glass composition has a Young’s modulus of greater than or equal to 94 GPa, and a forming gap (difference between a fiberizing temperature and a liquidus temperature) of less than -10 °C.

[0013] According to certain aspects, the glass composition comprises a SiO2 / MgO weight ratio of 2.8 to 3.1.

[0014] In any aspect of the subject invention, the glass composition may include:SiO2 in an amount of from 54 wt.% to 59 wt.%;AI2O3 in an amount of from 20 wt.% to 25 wt.%;CaO in an amount of from 4 to 7 wt.%;MgO in an amount of from 18 wt.% to 20 wt.%;Na2O+K2O in a total amount of from 0.01 to 0.25 wt.%; andZrO2 in an amount of from 0.5 to 1 wt.%. The glass composition may include a total concentration of AI2O3 and MgO is at least 40 wt.% and a weight ratio of SiCh to MgO is from 2.8 to 3.1.

[0015] Further exemplary aspects of the present invention are directed to method of forming a continuous high modulus glass fiber that includes providing a molten glass composition according to the present inventive concepts; and drawing said molten composition through an orifice to form a continuous glass fiber.

[0016] The glass fiber formed in accordance with the inventive concepts herein may be used to manufacture a reinforced composite product that includes a plurality of glass fibers dispersed within a polymer matrix. The reinforced composite product may form, for example, a wind blade.

[0017] The foregoing and other objects, features, and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description that follows.DETAILED DESCRIPTION

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which these exemplary embodiments belong. The terminology used in the description herein is for describing exemplary embodiments only and is not intended to be limiting of the exemplary embodiments. Accordingly, the general inventive concepts are not intended to be limited to the specific embodiments illustrated herein. Although other methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described herein.

[0019] As used in the specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0020] Unless otherwise indicated, all numbers expressing quantities of ingredients, chemical and molecular properties, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attachedclaims are approximations that may vary depending upon the desired properties sought to be obtained by the present exemplary embodiments. At the very least each numerical parameter should be construed in light of the number of significant digits and ordinary rounding approaches.

[0021] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the exemplary embodiments are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Every numerical range given throughout this specification and claims will include every narrower numerical range that falls within such broader numerical range, as if such narrower numerical ranges were all expressly written herein. Moreover, any numerical value reported in the Examples may be used to define either an upper or lower end-point of a broader compositional range disclosed herein.

[0022] Percentages by weight (“wt.%”) are reported herein on the basis of total oxides in the glass composition, unless otherwise specified.

[0023] Although the glass composition of the subject inventive concepts may be described and / or claimed in various ways, it should be appreciated the different compositions are alternative solutions to the particular problem addressed herein and are all part of the general inventive concepts disclosed.

[0024] The present disclosure relates to a natural resource focused glass composition with surprisingly high Young’s modulus, while being essentially free of lithium and rare earth oxides. By “essentially free of lithium and rare earth oxides,” it is meant that the glass composition includes no greater than 1.0 % by weight of lithium and rare earth oxides (individually or collectively), including no greater than 0.8 % by weight, 0.5 % by weight, 0.1 % by weight, 0.05 % by weight, and 0.01 % by weight. In some exemplary embodiments, the glass composition includes between 0 and less than 1.0 % by weight lithium and rare earth oxide (individually or collectively), including between 0 and 0.5 % by weight, and between 0 and 0.05 % by weight. In any of the exemplary embodiments, the glass composition may be entirely free of lithium and rare earth oxides. The rare earth oxides may include, for example, Y2O3, La2C>3, Ce2O3, and SC2O3, Ga2C>3, S1112O3, and / or Gd2C>3, and may also be referred to generally as “Re2O3”.

[0025] The current commercially available high modulus glass fibers include either lithium or rare earth oxides, in order to achieve Young’s modulus levels above 92 GPa. However, such oxides are expensive, limited, and require a significant amount of energy to product the grades needed for glass fiber reinforcement production. Removing lithium and rare earth oxides from a glass composition provides a more environmentally friendly glass composition and also produces a lighter density, high modulus glass fibers, which is a key metric for fiberglass composites used to manufacture wind blades that require longer blades in order to generate more energy. The longer blades require materials with higher modulus in order to withstand forces applied to them without breaking and without adding too much additional weight.

[0026] The glass composition may be in molten form, obtainable by melting the components of the glass composition in a melter. The glass composition exhibits a low fiberizing temperature, which is defined as the temperature that corresponds to a melt viscosity of about 1000 Poise, as determined by ASTM C965-96(2007). Another fiberizing property of a glass composition is the liquidus temperature. The liquidus temperature is defined as the highest temperature at which equilibrium exists between liquid glass and its primary crystalline phase. The liquidus temperature, in some instances, may be measured by exposing the glass composition to a temperature gradient in a platinum-alloy boat for 16 hours (ASTM C829- 81(2005)). At all temperatures above the liquidus temperature, the glass is completely molten, i.e., it is free from crystals. At temperatures below the liquidus temperature, crystals may form. The difference between the fiberizing temperature and liquidus temperature is often referred to as the forming gap or “AT”. Conventional fiberglass forming processes require a fiberizing temperature that is sufficiently above the glass compositions’ liquidus temperature for greater flexibility during fiberizing and to avoid devitrification both in the glass distribution system and in the fiberizing apparatus.

[0027] However, the subject glass composition has a negative AT, with a fiberizing temperature that is less than the liquidus temperature of the glass. A negative forming gap (or delta T) has heretofore been challenging because the glass will tend to crystallize at the forming temperature. Accordingly, glass compositions with a negative forming gap have to be fiberized at a higher than typical temperature.

[0028] The glass composition may have a AT of less than about -10°C, including, for example, less than about -15°C, less than about -20°C, less than about -25°C, less than about -30°C, less than about -35°C, less about -40°C, less than about -45°C, and less than about -50°C. In such aspects, the glass composition may have a AT from less than 0°C to about -75°C, such as, for example, less than about -5°C to less than about -70 °C, less than about -10°C to less than about -60°C, less than about -15°C to less than about -55°C, less than about -20°C to less than about -45 °C, including all endpoints and subranges therebetween.

[0029] In any of the aspects disclosed herein, the glass composition may have a fiberizing temperature of less than about l,350°C, including fiberizing temperatures of no greater than about 1,325°C, no greater than about 1,315°C, no greater than about l,300°C, no greater than about l,290°C, no greater than about 1,275°C, no greater than about 1,265°C, and no greater than about 1,250 °C. In some exemplary embodiments, the glass composition has a fiberizing temperature no greater than about 1,285°C, such as no greater than about l,280°C, and no greater than about 1,275°C.

[0030] In some exemplary embodiments, the glass composition has a liquidus temperature of at least about 1,275°C, including liquidus temperature of at least about l,290°C, at least about l,300°C, at least about l,310°C, at least about 1320°C, at least about l,330°C, at least about 1,345°C, at least about l,350°C, and at least about 1,365°C. In some exemplary embodiments, the glass composition has a liquidus temperature between about l,300°C and about l,390°C, including between about 1,315°C, and about 1,375°C, and between about l,320°C and about l,360°C, including all subranges and endpoints therebetween.

[0031] The high modulus glass composition includes SiCT in an amount of 50 wt.% to 62 wt.%, AI2O3 in an amount between 18 wt.% to 35 wt.%, MgO in an amount of at least 18 wt.%, and, optionally, up to 12 wt.% CaO, such that the total SiO2+ MgO concentration is at least 70 wt.%, and the total concentration of AhOs+MgO is at least 38 wt.%. The composition includes less than 0.05 wt.% of Li2O and / or rare earth oxides. The components of the glass composition are provided in particular relationships and ratios that surprisingly provide fiberglass with a Young’s modulus of at least 94 GPa without the inclusion of either lithium or rare earth oxides. Such relationships include a total concentration of AI2O3 and MgO (AhOs+MgO) of greater than 38 wt.% and a weight ratio of SiO2 to MgO (SiO2 / MgO) from 2.6 to 3.1. Such a glass composition has a liquidus temperature that is greater than its fiberizing temperature. Thus, the high modulus glass composition defined herein demonstrates a negative forming gap (also referred to as AT).

[0032] The glass composition includes at least 50 wt.%, but no greater than 62 wt.% SiCh. In some instances, the glass composition may include at least 52 wt.% SiCh, including at least 53.5 wt.%, at least 54 wt.%, at least 55 wt.%, and at least 55.5 wt.%. In some instances, the glass composition includes no greater than wt.% SiCT. including no greater than 60 wt.%, no greater than 59 wt.%, no greater than 58.5 wt.%, no greater than 58 wt.%, no greater than 57.8 wt.%, no greater than 57.4 wt.%, and no greater than 57 wt.%.

[0033] Thus, certain aspects of the glass composition may include SiCh in an amount between 50 wt.% and 62 wt.%, including, for example, between 52 wt.% and 60 wt.%, between 53.5 wt.% and 59.5 wt.%, 54 wt.% and 58.5 wt.%, and 54.5 wt.% and 58 wt.%, including all subranges and endpoints therein.

[0034] To achieve a glass fiber having a high Young’s modulus in the absence of lithium and rare earth oxides, the glass composition includes a high concentration of MgO, with a minimum concentration of 18 wt.%. Magnesium is the highest field strength (charge to size ratio) alkaline earth ion (other than beryllium). In simple terms, it creates stronger bonding in tighter spaces. The glass composition includes an amount of greater than or equal to 18 wt.% MgO, including at least 18.5 wt.%, at least 19 wt.%, at least 19.2 wt.%, at least 19.4 wt.%, and at least 19.8 wt.% MgO. Additionally, the glass composition includes less than or equal to 22 wt.% MgO, including no greater than 21.8 wt.%, no greater than 21.5 wt.%, no greater than 21 wt.%, no greater than 20.8 wt.%, and no greater than 20.5 wt.% MgO. According to certain aspects, the glass composition includes 18 wt.% to 22 wt.% MgO, including, for example, 18.2 wt.% to 21.8 wt.% MgO, 18.5 wt.% to 21.5 wt.% MgO, 18.8 wt.% to 21.2 wt.% MgO, 19 wt.% to 21 wt.% MgO, and 19.3 wt.% to 20.5 wt.% MgO, including all endpoints and subranges therebetween.

[0035] The glass composition includes MgO in a concentration (wt.%) such that the weight ratio of SiO2 to MgO (SiO2 / MgO) is between 2.6 and 3.1. SiO2 is the primary glass former (O- Si-0 linkages, with 4 oxygens to each silicon and 2 silicones to each oxygen) and MgO contributes Mg2+cations to the structure, which create two non-bridging oxygens (NBOs) in the glass former linkages. A weight ratio of SiO2 / MgO above 3.1 would indicate that there are too many bridging oxygens in the structure, which may lead to high viscosity and difficulty in forming due to the high temperatures required to reach the forming viscosity. A weight ratio of SiO2 / MgO below 2.6 may result in too many NBOs and a very broken or flexible structure, which leads to a low viscosity, along with a low strength and modulus. A balance in theSiCh / MgO weight ratio value has been discovered to achieve the desired properties for both forming and application in the market. In certain aspects, the glass composition includes MgO and SiO2 in concentrations such that the ratio of SiCh to MgO is between 2.8 and 3.05, or between 2.9 and 3.0, including all endpoints and subranges therebetween. In any of the aspects herein, the glass composition may include a weight ratio of SiO2 to MgO (SiO2 / MgO) that is less than 3.

[0036] Another important aspect of the glass composition is an AI2O3 concentration of at least 18 wt.% and no greater than 35 wt.%. AI2O3 helps to improve glass modulus, but also tends to increase the glass liquidus, so it is often limited such as to have as little impact to the liquidus temperature as possible. However, as the subject glass is capable of processing with a negative forming gap, the amount of AI2O3 can be increased to as high as 35 wt.%. According to any of the aspects herein, the concentration of AI2O3 is be between 18 wt.% and 35 wt.%, including between 18.3 wt.% and 32 wt.%, between 18.5 wt.% and 30 wt.%, between 19 wt.% and 28 wt.%, between 19.3 wt.% and 27 wt.%, between 19.5 wt.% and 25 wt.%, between 19.8 wt.% and 24.5 wt.%, between 20 wt.% and 24 wt.%, and between 20.0 wt.% and 23 wt.%, including all endpoints and subranges therebetween.

[0037] The glass composition includes AI2O3 and MgO in such concentrations to provide a total concentration of AI2O3 and MgO that is at least 38 wt.%. A high total concentration of AI2O3 and MgO is important in order to provide a glass composition capable of forming a glass fiber with a Young’s modulus of at least 94 GPa, while excluding rare earth oxides and / or lithium. In an of the exemplary aspects, the glass composition includes a total concentration of AI2O3 and MgO greater than 38 wt.%, such as, for example, at least 39 wt.%, at least 40 wt.%, at least 41 wt.%, and at least 42 wt.%.

[0038] The SiO2, AI2O3, and MgO concentrations are further carefully selected such that the weight ratio of MgO +AI2O3 to SiO2 ((MgO+A12O3) / Si2O)) in the glass composition is at least 0.68, and preferably at least 0.69, or 0.70.

[0039] The glass composition advantageously includes less than 12 wt.% CaO. CaO tends to negatively impact Young’s modulus, and therefore the subject glass composition optionally includes CaO, in an amount that does not exceed 12 wt.%. According to some aspects, the glass composition includes less than 12 wt.% CaO, such as, for example, less than or equal to 10 wt.%, less than or equal to 8 wt.%, less than or equal to 5.5 wt.%, less than or equal to 5 wt.%,less than or equal to 4 wt.%, less than or equal to 2.5 wt.%, or less than or equal to 2 wt.% CaO. In some exemplary embodiments, the glass composition is free of CaO, or includes CaO in only trace amounts, such as less than below 0.5 wt.%. Thus, according to some aspects, the glass composition may include 0 to less than 12 wt.% CaO, including, for example, 0 to 10 wt.% CaO, 0 to 5 wt.% CaO, or 0 to 2 wt.% CaO, although such aspects may alternatively include minimal amounts of CaO, such as at least 0.5 wt.%, at least 0.75 wt.%, at least 1.0 wt.%, and at least 1.25 wt.%.

[0040] As mentioned above, the glass compositions disclosed herein exhibit a high Young’s modulus, while being free or essentially free of Li2O and rare earth oxides, such as, for example Y2O3, LajOj, CesOa, and SC2O3. Accordingly, the glass composition includes an amount of rare earth oxides that is no greater than 1 wt.%, no greater than 0.75 wt.%, no greater than 0.5 wt.%, no greater than 0.25 wt.%, no greater than 0.15 wt.%, and no greater than 0.05 wt.%. The glass composition additionally includes less than 1 wt.% of Li2O, including no greater than 0.75 wt.%, no greater than 0.5 wt.%, no greater than 0.25 wt.%, no greater than 0.15 wt.%, no greater than 0.1 wt.%, no greater than 0.05 wt.%, and no greater than 0.01 wt.% Li2O. In some exemplary embodiments, the glass composition includes between 0 wt.% and less than 1 wt.% Li2O, including between 0 wt.% and 0.5 wt.%, between 0 wt.% and 0.5 wt.%, and between 0 wt.% and 0.05 wt.%. In some exemplary embodiments, the glass composition is entirely free of Li2O and rare earth oxides.

[0041] The glass composition may optionally include the alkali metal oxides NajO and K2O, in individual or collective amounts of 0 to less than about 2 wt.%. For instance, in any of the exemplary embodiments, the glass composition may include from about 0.01 wt.% to less than about 2 wt.% Na2O and K2O, including from about 0.05 wt.% to about 1.8 wt.%, from about 0.1 wt.% to about 1.6 wt.%, from about 0.2 wt.% to about 1.4 wt.%, from about 0.4 wt.% to about 1.2 wt.%, from about 0.5 wt.% to about 1 wt.%, from about 0.8 wt.% to about 0.8 wt.%, including all endpoints and subranges therebetween. In any of the embodiments disclosed herein, the glass composition may have a total content of Na2.0 and K2O of less than 1.5 wt.%;, less than 1 wt.%, or less than 0.5 wt.%. In any of the exemplary embodiments, the glass composition may be free of Na2O and / or K2O.

[0042] The glass composition may further optionally include Z1O2 and / or ZnO. For instance, in any of the exemplary embodiments, the glass composition may include from 0 wt.% to about 3 wt.% Z1O2. including from about 0.1 wt.% to about 2 wt.%, from about 0. 5 wt.% to about1.5 wt.% and from about 1 wt.% to about 1.5 wt.% ZrCh. Additionally or alternatively, the glass composition may include from greater than 0 wt.% to about 3 wt.% ZnO, including from about 0.01 wt.% to about 2 wt.%, from about 0.05 wt.% to about 1 wt.% and from about 0.1 wt.% to about 0.5 wt.% ZnO. It should be understood that in exemplary embodiments, the glass composition may include ZrO2, ZnO, ZrO2 and ZnO, or neither ZrO2 nor ZnO.

[0043] The glass composition may further optionally include TiO2 and / or Fe2O3 in individual or collective amounts of at least 0.01 wt.%. For instance, in any of the exemplary embodiments, the glass composition may include from about 0 to about 2 wt.% TiO2, including from about 0.1 wt.% to about 2 wt.%, from about 0.2 wt.% to about 2 wt.%, from about 0.5 wt.% to about 2 wt.%, from about 0.01 wt.% to about 1.5 wt.%, from about 0.1 wt.% to about 1.5 wt.%, from about 0.2 wt.% to about 1.5 wt.%, from about 0.5 wt.% to about 1.5 wt.%, from about 0.01 wt.% to about 1 wt.%, from about 0.1 wt.% to about 1 wt.%, from about 0.2 wt.% to about 1 wt.%, from about 0.5 wt.% to about 1 wt.%, from about 0.01 wt.% to about 0.8 wt.%, from about 0.1 wt.% to about 0.8 wt.%, from about 0.2 wt.% to about 0.8 wt.%, from about 0.5 wt.% to about 0.8 wt.% TiCF. Additionally or alternatively, the glass composition may include from 0 wt.% to about 3 wt.% Fe2O3, including from about 0.01 wt.% to about 2 wt.%, from about 0.05 wt.% to about 1 wt.% and from about 0.1 wt.% to about 0.5 wt.% Fe2O3.

[0044] The glass composition may also be free or substantially free of B2O3 and fluorine, although either, or any, may be added in small amounts to adjust the fiberizing and finished glass properties and will not adversely impact the properties if maintained below several percent. As used herein, substantially free of B2O3 and fluorine means that the sum of the amounts of B2O3 and fluorine present is less than 1.0 wt.% of the composition. The sum of the amounts of B2O3 and fluorine present may be less than about 0.5 wt.% of the composition, including less than about 0.2 wt.%, less than about 0.1 wt.%, and less than about 0.05 wt.%.

[0045] The glass compositions may further include impurities and / or trace materials without adversely affecting the glasses or the fibers. These impurities may enter the glass as raw material impurities or may be products formed by the chemical reaction of the molten glass with furnace components. Non-limiting examples of trace materials include zinc, strontium, barium, and combinations thereof. The trace materials may be present in their oxide forms and may further include fluorine and / or chlorine. In some exemplary embodiments, the inventive glass compositions contain less than 1 wt.%, including less than 0.5 wt.%, less than 0.2 wt.%, and less than 0.1 wt.% of each of BaO, SrO, P2O5, and SO3. Particularly, the glass compositionmay include less than about 5.0 wt.% of BaO, SrO, P2O5, and / or SO3 combined, wherein each of BaO, SrO, P2O5, and SO3 if present at all, is present in an amount of less than 1 wt.%.

[0046] The glass composition may alternatively be characterized in terms of moles, whereby each component is present in a particular mole percentage or molar ratio. For instance, it has been discovered that glass composition capable of forming glass fibers with a Young’ s modulus of at least 94 GPa, while excluding rare earth oxides and / or lithium, include SiCF and MgO in molar amounts such that the mole ratio of SiCF / MgO is less than 2.1. Similar glass compositions that include SiCF / MgO mole ratios of 2.1 or greater demonstrate decreasing Young’s Modulus levels with increasing SiCF / MgO mole ratios. Accordingly, the glass composition may include an SiCF / MgO mole ratio of no greater than 2.1, including, for example, from 1.0 to 2.08, from 1.1 to 2.05, from 1.3 to 2.03, from 1.5 to 2.0, from 1.7 to 1.98, and from 1.8 to 1.95, including all endpoints and subranges therebetween.

[0047] Table 1, below, provides various exemplary compositional ranges formulated in accordance with the present inventive concepts.TABLE 1

[0048] As mentioned above, the glass composition comprises a lithium and rare earth oxidefree unique blend of oxides that is capable of forming a glass fiber with a high Young’s modulus. Particularly, the glass composition includes an increased concentration of MgO and a combined concentration of AI2O3 and MgO of at least 38 wt.%, thus forming a glass fiber with a Young’s modulus of greater than or equal to 94 GPa and a specific modulus of at least 35 MJ / kg. The glass composition further includes a unique SiO2 / MgO mole ratio that is no greater than 2.1.

[0049] The Young’s modulus (or “elastic modulus”) of a glass fiber may be determined by taking the average measurements on five single glass fibers measured in accordance with the sonic measurement procedure outlined in the report “Glass Fiber and Measuring Facilities at the U.S. Naval Ordnance Laboratory”, Report Number NOLTR 65-87, June 23, 1965 (known herein as the “fiber modulus”). In comparison, another method of measuring modulus is to measure the bulk modulus. Modulus measurements on bulk samples are not equivalent or comparable to the fiber modulus because of the different thermal histories involved in forming the types of samples. Furthermore, bulk samples must be annealed prior to the cutting, grinding, and polishing required to produce the specific samples needed for the bulk measurement. This annealing step takes the bulk sample atomic structure even further from that of the fiber. Thus, such bulk modulus measurements are not directly comparable to fiber modulus, described herein. Bulk modulus measurements are described in ASTM C1259 or E1876.

[0050] The glass fibers formed from the inventive glass composition have a Young’s modulus (fiber modulus) of at least about 94 GPa, such as a Young’s modulus of at least about94.1 GPa, at least about 94.3 GPa, at least about 94.5 GPa, at least about 95 GPa, at least about95.1 GPa, at least about 95.3 GPa, and at least about 95.6 GPa. According to any aspect, the glass fibers formed from the inventive glass composition have a Young’s modulus of between about 94 GPa and about 98 GPa, including between about 94.2 GPa and about 96 GPa, and between about 94.5 GPa and about 95.8 GPa, including any endpoints and subranges therebetween.

[0051] The glass composition disclosed herein forms glass fibers having a density between 2.4 g / cc to 3.0 g / cc. The density may be measured by any method known and commonly accepted in the art, such as the Archimedes method (ASTM C693-93(2008)) on unannealed bulk glass. In any of the exemplary embodiments, the glass fibers may have a density between2.5 g / cc to 2.9 g / cc, including from 2.6 g / cc to 2.8 g / cc, 2.55 to 2.75 g / cc, and 2.6 to 2.7 g / cc.

[0052] The density and Young’s modulus are then used to determine the specific modulus of the glass fiber. It is desirable to have a specific modulus as high as possible to achieve a lightweight composite material that adds stiffness to the final article. Specific modulus is important in applications where stiffness of the product is an important parameter, such as in wind energy and aerospace applications. As used herein, the specific modulus is calculated by the following equation:Specific Modulus (MJ / kg) = Modulus (GPa) / Density (kg / cubic meter)

[0053] The exemplary glass fibers formed from the inventive glass composition have an optimized specific modulus of about 35 MJ / kg to about 40.0 MJ / kg, including about 35.4 MJ / kg to about 39 MJ / kg, and about 35.6 MJ / kg to about 38 MJ / kg.

[0054] According to some exemplary embodiments, a method is provided for preparing glass fibers from the glass composition described above. The glass fibers are formed at an elevated temperature, compared to conventional fiberizing temperatures. In some aspects, the glass fibers are formed by obtaining raw ingredients and mixing the ingredients in the appropriate quantities to give the desired weight percentages of the final composition. The method may further include providing the inventive glass composition in molten form and drawing the molten composition through orifices in a bushing to form a glass fiber.

[0055] The mixed batch may then be melted in a furnace or melter and the resulting molten glass is passed along a forehearth and drawn through the orifices of a bushing located at the bottom of the forehearth to form individual glass filaments. In some exemplary embodiments, the furnace or melter is a traditional refractory melter. By utilizing a refractory tank formed of refractory blocks, manufacturing costs associated with the production of glass fibers produced by the inventive composition may be reduced. In some exemplary embodiments, the bushing is a platinum alloy-based bushing. Strands of glass fibers may then be formed by gathering the individual filaments together. The fiber strands may be wound and further processed in a conventional manner suitable for the intended application.

[0056] The operating temperatures of the glass in the melter, forehearth, and bushing may be selected to appropriately adjust the viscosity of the glass, and may be maintained using suitable methods, such as control devices. The temperature at the front end of the melter may beautomatically controlled to reduce or eliminate devitrification. The molten glass may then be pulled (drawn) through holes or orifices in the bottom or tip plate of the bushing to form glass fibers. In accordance with some exemplary embodiments, the streams of molten glass flowing through the bushing orifices are attenuated to filaments by winding a strand formed of a plurality of individual filaments on a forming tube mounted on a rotatable collet of a winding machine or chopped at an adaptive speed. The glass fibers of the invention are obtainable by any of the methods described herein, or any known method for forming glass fibers.

[0057] The fibers may be further processed in a conventional manner suitable for the intended application. For instance, in some exemplary embodiments, the glass fibers are sized with a sizing composition known to those of skill in the art. The sizing composition is in no way restricted, and may be any sizing composition suitable for application to glass fibers. The sized fibers may be used for reinforcing substrates such as a variety of plastics where the product’s end use requires high strength and stiffness and low weight. Such applications include, but are not limited to, nonwoven mats and woven fabrics for use in forming wind turbine blades; infrastructure, such as reinforcing concrete, bridges, etc.; and aerospace structures. Exemplary woven fabrics include, for example, unidirectional, uniaxial, multiaxial, stitched fabric, and the like.

[0058] In this regard, some exemplary embodiments of the present invention include a composite material incorporating the inventive glass fibers, as described above, in combination with a hardenable matrix material. This may also be referred to herein as a reinforced composite product. The matrix material may be any suitable thermoplastic or thermoset resin known to those of skill in the art, such as, but not limited to, thermoplastics such as polyesters, polypropylene, polyamide, polyethylene terephthalate, and polybutylene, and thermoset resins such as epoxy resins, unsaturated polyesters, phenolics, vinylesters, and elastomers. These resins may be used alone or in combination. The reinforced composite product may be used for wind turbine blade, rebar, pipe, filament winding, muffler filling, sound absorption, and the like.

[0059] In accordance with further exemplary embodiments, the invention provides a method of preparing a composite product as described above. The method may include combining at least one polymer matrix material with a plurality of glass fibers. Both the polymer matrix material and the glass fibers may be as described above.EXAMPLES

[0060] Exemplary glass compositions according to the present invention were prepared by mixing batch components in proportioned amounts to achieve a final glass composition with the oxide weight percentages set forth in Tables 2, 3, and 4 below.

[0061] The raw materials were melted in a platinum crucible in an electrically heated furnace at a temperature of l,600°C for 3 hours. The fiberizing temperature was measured using a rotating cylinder method as described in ASTM C965-96(2007), entitled “Standard Practice for Measuring Viscosity of Glass Above the Softening Point,” the contents of which are incorporated by reference herein. The liquidus temperature was measured by exposing glass to a temperature gradient in a platinum- alloy boat for 16 hours, as defined in ASTM C829- 81(2005), entitled “Standard Practices for Measurement of Liquidus Temperature of Glass,” the contents of which are incorporated by reference herein. Density was measured by the Archimedes method, as detailed in ASTM C693-93(2008), entitled “Standard Test Method for Density of Glass Buoyancy,” the contents of which are incorporated by reference herein.

[0062] The Young’s modulus was measured by the sonic fiber technique, in accordance with the measurement procedure outlined in the report “Glass Fiber Drawing and Measuring Facilities at the U.S. Naval Ordnance Laboratory,” Report Number NOLTR 65-87, June 23, 1965. The specific modulus was calculated by dividing the measured elastic modulus in units of GPa by the density in units of g / cc.TABLE 2TABLE 3TABLE 4(a)- COMPARATIVE EXAMPLESTable 4(b)- COMPARATIVE EXAMPLES

[0063] As demonstrated above, in Tables 2 and 3, glass fibers formed from glasscompositions in accordance with the present inventive concepts (such as an MgO concentration of at least 18 wt.% and one or more of the following: a total concentration of AhCh+MgO greater than 38 wt.%, an SiCh / MgO weight ratio between 2.6 and 3.1, an SiCh / MgO mole ratio no greater than 2.1, and an (MgO+AhChVSiCh ratio of at least 0.68 achieve a Young’s modulus of at least 94 GPa and a specific modulus of at least 35. In some aspects, if the glass composition falls outside one or more of these relationships, the glass fibers formed therefrom exhibit a drop in Young’s modulus to levels below 94 GPa.

[0064] Various aspects of the present disclosure have been described above both generically and with regard to specific embodiments. Although the invention has been set forth in what is believed to be the preferred embodiments, a wide variety of alternatives known to those of skill in the art can be selected within the generic disclosure. The invention is not otherwise limited, except for the recitation of the claims set forth below.

Claims

CLAIMS1. A glass composition comprising:SiCh in an amount of from 50 wt.% to 62 wt.%;AI2O3 in an amount of from 18 wt.% to 35 wt.%;CaO in an amount of from 0 to 12 wt.%;MgO in an amount of greater than or equal to 18 wt.%;Na2O+K2O in a total amount of from 0 to 0.5 wt.%; andZrCh in an amount of from 0 to 2 wt.%; wherein a total concentration of AI2O3 and MgO is greater than 38 wt.% and a weight ratio of SiO2 to MgO is from 2.6 to 3.1; wherein the glass composition includes less than 0.05 wt.% of lithium and rare earth oxides (Re2O3), and wherein a glass fiber formed from the glass composition has a Young’s modulus of greater than or equal to 94 GPa.

2. The glass composition of claim 1, wherein the glass fiber has a Young’s modulus or greater than or equal to 95 GPa.

3. The glass composition of claim 1 or claim 2, wherein the glass composition further comprises ZrO2 in an amount of from 0.1 wt.% to 2 wt.%.

4. The glass composition of any preceding claim, wherein the glass composition comprises a SiO2 / MgO ratio of 2.9 to 3.05.

5. The glass composition of any preceding claim, wherein the glass composition includes an APO^+MgO concentration of at least 40 wt.%.

6. The glass composition of any preceding claim, wherein the glass composition includes at least 20 wt.% MgO.

7. The glass composition of any preceding claim, wherein the glass composition includes at least 20 wt.% AI2O3.

8. The glass composition of any preceding claim, wherein the glass composition is free of Li2O.

9. The glass composition of any preceding claim, wherein the glass composition is free of rare earth oxides (Re2O3).

10. The glass composition of any preceding claim, wherein the glass composition comprises:SiCh in an amount of from 54 wt.% to 59 wt.%;AI2O3 in an amount of from 20 wt.% to 25 wt.%;CaO in an amount of from 4 to 7 wt.%;MgO in an amount of from 18 wt.% to 20 wt.%;Na2O+K2O in a total amount of from 0.01 to 0.25 wt.%; andZrCh in an amount of from 0.5 to 1 wt.%; wherein a total concentration of AI2O3 and MgO is at least 40 wt.% and a weight ratio of SiO2 to MgO is from 2.9 to 3.05.

11. The glass composition of any preceding claim, wherein the glass composition has a fiberizing temperature that is less than l,300°C.

12. The glass composition of any preceding claim, wherein the glass composition has a fiberizing temperature that is less than a liquidus temperature.

13. The glass composition of any preceding claim, wherein the glass composition has a forming gap (difference between a fiberizing temperature and a liquidus temperature) that is less than -10°C.

14. A lithium-free glass composition comprising:SiCh in an amount of from 54 wt.% to 59 wt.%;AI2O3 in an amount of from 18 wt.% to 35 wt.%;CaO in an amount of from 0 to 12 wt.%;MgO in an amount of greater than or equal to 18 wt.%;Na2O+K2O in a total amount of from 0 to 0.2 wt.%; andZrO2 in an amount of from 0 to 2 wt.%; wherein a total concentration of AI2O3 and MgO is greater than 38 wt.%; wherein the glass composition is free of lithium and rare earth oxides (Re2O3), and wherein the glass composition has a Young’s modulus of greater than or equal to 94 GPa and a forming gap (difference between a fiberizing temperature and a liquidus temperature) of less than -10 °C.

15. The glass composition of claim 14, wherein the glass composition has a Young’s modulus or greater than or equal to 95 GPa.

16. The glass composition of claim 14 or claim 15, wherein the glass composition further comprises Z1O2 in an amount of from 0.1 wt.% to 2 wt.%.

17. The glass composition of any one of claims 14 to 16, wherein the glass composition comprises a SiCh / MgO weight ratio of 2.8 to 3.1.

18. The glass composition of any one of claims 14 to 17, wherein the glass composition includes an AOCh+MgO concentration of at least 40 wt.%.

19. The glass composition of any one of claims 14 to 18, wherein the glass composition includes at least 20 wt.% MgO.

20. The glass composition of any one of claims 14 to 19, wherein the glass composition includes at least 20 wt.% AI2O3.

21. The glass composition of any preceding claim, wherein the glass composition comprises:SiCh in an amount of from 54 wt.% to 59 wt.%;AI2O3 in an amount of from 20 wt.% to 25 wt.%;CaO in an amount of from 4 to 7 wt.%;MgO in an amount of from 18 wt.% to 20 wt.%;Na2O+K2O in a total amount of from 0.01 to 0.25 wt.%; andZrO2 in an amount of from 0.5 to 1 wt.%; wherein a total concentration of AI2O3 and MgO is at least 40 wt.% and a weight ratio of SiO2 to MgO is from 2.8 to 3.1.

22. The glass composition of any preceding claim, wherein the glass composition has a fiberizing temperature that is less than l,300°C.

23. The glass composition of any preceding claim, wherein the glass composition has a forming gap (difference between a fiberizing temperature and a liquidus temperature) that is less than -25 °C.

24. A high modulus glass fiber formed from the glass composition of any of claims 1525. A method of forming a continuous high modulus glass fiber comprising: providing a molten glass composition according to any preceding claim; and drawing said molten composition through an orifice to form a continuous glass fiber.

26. A reinforced composite product comprising; a polymer matrix; and a plurality of glass fibers formed in accordance with any preceding claim.

27. A reinforced composite product according to claim 26, wherein the reinforced composite product is in the form of a wind blade.