Posted on

Basalt – Twisted

Reasons to twist Yarns: 

  • protection of the fiber
  • increase tensile strength
  • creating hybrid fibers with various properties
  • allow to process in various stringent conditions

.... more about twisting

Basalt fiber can be twisted. Regardless the tex count, be it 34 (150 h.y.p.p), 68 (75 h.y.p.p), 136 (34 h.y.p.p) , etc. can be twisted. When it comes to the higher dense materials, it can be come somewhat tricky but is still possible for the most part. You can also twist texturized fibers.

... more about texturizing

Typically the twist is to ease production in the following value added step.

Application Ideas: 

  • weaving
  • Braiding
  • Knit-Braiding
  • Knitting
  • Sewing Threads
Posted on

Textile Process: Weaving, Slashing, Warping

The process in brief:

In weaving cloth, the warp is the set of lengthwise yarns that are held in tension on a frame or loom. The yarn that is inserted over-and-under the warp threads is called the weft, woof, or filler. Each individual warp thread in a fabric is called a warp end or end. Warp means “that which is thrown across” (OldEnglish wearp, from weorpan, to throw, cf.German werfenDutch werpen).

Very simple looms use a spiral warp, in which a single, very long yarn is wound around a pair of sticks or beams in a spiral pattern to make up the warp.

Because the warp is held under high tension during the entire process of weaving and warp yarn must be strong, yarn for warp ends is usually spun and plied fiber. Traditional fibers for warping are woollinenalpaca, and silk. With the improvements in spinning technology during the Industrial Revolution, it became possible to make cotton yarn of sufficient strength to be used as the warp in mechanized weaving. Later, artificial or man-made fibers such as nylon rayon or glass fibers were employed.


In Glass Fiber weaving, the most common weave patterns are

  • Basket Weave
  • Plain Weave
  • Satin Weave
  • Twill & Broken Twill Weave

 Basket Weave:

In Basket weave or Panama weave, groups of warp and weft threads are interlaced so that they form a simple criss-cross pattern. Each group of weft threads crosses an equal number of warp threads by going over one group, then under the next, and so on. The next group of weft threads goes under the warp threads that its neighbor went over, and vice versa.

Basketweave can be identified by its checkerboard-like appearance made of two or more threads in each group.


Plain Weave:

Schematic of a plain weave, which would be woven by a shuttle loom (left).

The right schematic represents the modern Plain weave, as the fiber is not anymore continuous throughout multiple sheddings, but it is cut after each shedding takes place.


Allthough shuttle looms are still in use mostly for narrow fabrics, they have been widely replaced by other, more efficient weaving technology:

Airjet Weaving * Projectile Weaving * Rapier Loom Weaving * Waterjet weaving.

 Satin Weave:

The satin weave is characterized by four or more fill or weft yarns floating over a warp yarn or vice versa, four warp yarns floating over a single weft yarn. Floats are missed interfacings, where the warp yarn lies on top of the weft in a warp-faced satin and where the weft yarn lies on top of the warp yarns in weft-faced satins. These floats explain the even sheen, as unlike in other weaves, the light reflecting is not scattered as much by the fibres, which have fewer tucks.

In glass fiber weaving, satin fabrics are popular when high drape ability is required. If the fabric has to be layed around corner or edges.

This Schematic also shows a traditional shuttle loom woven Satin Pattern.


 Twill Weave:

Twill fabrics technically have a front and a back side, unlike plain weave, whose two sides are the same. The front side of the twill is the technical face; the back is called the technical back. The technical face side of a twill weave fabric is the side with the most pronounced wale; it is usually more durable, more attractive, most often used as the fashion side of the fabric, and the side visible during weaving. If there are warp floats on the technical face (i.e., if the warp crosses over two or more wefts), there will be filling floats (the weft will cross over two or more warps) on the technical back. If the twill wale goes up to the right on one side, it will go up to the left on the other side. Twill fabrics have no up and down as they are woven.

The fewer interlacings in twills allow the yarns to move more freely, and thus they are softer, more pliable, and drape better than plain-weave textiles. Twills also recover from wrinkles better than plain-weave fabrics do. When there are fewer interlacings, yarns can be packed closer together to produce high-count fabrics. In twills and higher counts, the fabric is more durable.

Schematic of Twill Woven Fabric:


Weaving Glass Fibers:

Due to the low elongation coefficient (% of stretch before it breaks) of approx. 2.0 – 3.5 %, weaving Glass Fibers require very precise machine adjustments. It becomes a little simpler when the yarns have been texturized, as the extra bulk in essence increases the elongation coefficient by the grade of texture.

Due to the “brittle” nature of glass fibers, the finer yarns require preparation to withstand the harsh friction caused by the reed. This preparation is called Slashing.


While Roving or texturized yarns typically do not need any special additional treatment of seizing, the finer yarns typically do.

Slashing is a process in which the strand will be applied an additional seizing, aiding the weaving process. Without this additional seizing, the yarn in the warp will be starting to create “fuzz” from broken filaments. This is due to the reed rupturing the warp strands. The fuzz in return will influence the shedding behavior of the neighboring fibers. This may cause those fibers not to clearly separate from each other, when the shedding takes place. This will result in either a simple miss pick or in a complete yarn breakage in the warp.

The slashing typically handles two production steps in one;

a) application of the required additional seizing

b) warping the strands to a loom beam. (Note:Slashing can also be offered on a “bobbin-to-bobbin”-process, as well.)

In case of slashed bobbins, a second process will have to take place, which is called warping.


Warping is the process in which single strands of fibers (yarns) will be wound to a beam which is called a loombeam. This loombeam can then be either attached or connected to the weaving loom or put on a separate A-Phrame construction.

Depending on the desired weave construction, at times, two loombeams can be implemented. In that case, a top beam stand is mounted to the machine, holding the second beam.

There are three basic Warping Techniques:

a) Sample Warping

Sample Warping is typically for around 30 yards or under 100 yards, as needed, just for weaving samples. Other lengths apply, but in essence it is meant for short runs.

b) Sectional Warping

A Sectional Warper draws e.g. 200 single ends at a time and winds it to a loombeam. This is then called a section. After the desired quantity has been wound, e.g. 5,000 yards, the second section will be applied with the same yard count. In order to do so, the warper will be moved a small distance on a rail system, to be centered again in front of the next section. This process will be repeated, until the desired total end count has been reached.

C) Direct Warping

A Direct Warper draws all the required strands at one time and applies the desired quantity of yards in this one process. Therefore, while Sectional Warping and Direct Warping both result in the same end count with the desired max quantity per strand, the sectional warping process calls for multiple production steps, while the Direct Warper produces it in one production step.

The choice of the correct warping system depends on the mill’s setup.

Caution with warping, as glass fiber has a very low elongation coefficient, precise machine adjustments and tension systems are required.

Creel Weaving: 

More dense or heavier yarns, around 270 tex and up, are preferably woven on creels.

Two basic creel designs:

a) Pin Creel

Here, the bobbin is stuck on a pin.

B) Shelf Creel

Here the bobbin stands on a shelf.

While there are many different designs of pin creels or shelf creels, it appears that the shelf creel provides more flexibility, as some glass fiber manufacturers provide rovings for inside and some for outside unwinding. Rovings with inside unwinding cannot be used for pin creels.

Posted on

Textile Process: Twisting

Twisting is the process which applies turns to one or multiple strands of yarns.

Turns can be in S-Direction and they can be in Z-direction.

Depending on the intended following production process, the amount of turns/ inch or turns / m can vary.

For better visibility, following is an example of a twisted cotton strand:


You can now count how many turns/ inch or per cm have been applied.

In general, the larger the amount of turns / inch, the higher the cost, as it takes the machine longer to manufacture the required count.

While Rovings have almost no or even zero twist, fine yarns usually will only be available with a low twist count. A converter will then apply higher twist counts.

Reasons to twist Yarns: 

  • protection of the fiber
  • increase tensile strength
  • creating hybrid fibers with various properties
  • other

 There are two main twisting processes:

a) Ring twisting

b) Direct Cabling or “false twisting”

Glass Fibers have a “recall” effect, they tend to twist or turn back into the original form. Therefore, when twisting two strands together, this needs to be taken into account.

Ring Twisting: 

Ring twisting consist of two production processes:

Process 1:

Individual strands will be first twisted in one direction, in most cases Z-Direction.

Process 2:

In the second conversion process, two or more single strands will be put together while twisting them now in the opposite direction, in this case in the S-Direction.

This way, 2 up to 12 or even more strands can be twisted together and they are not effected by the “recall”-effect when twisted right.

The cones the materials are twisted on are called “milk bottle” bobbins, due to the shape.

Direct Cabling: 

Direct cabling process is only one production step. While one strand of yarn stays in the original direction, the second strand of yarn will be wrapped around the other.

Due to only one required production process, this method is considered to be more cost effective.

The cones the materials are twisted on are cylindrical.

Currently, direct cabling can only be done with two strands, while ring twisting is more flexible and can be many fold.

Courtsey of

Posted on

About Glass Fibers

Fiberglass is the original fiber reinforcement of modern composites. Though the ancient Phoenicians, Egyptians and Greeks knew how to melt glass and stretch it into thin fibers, it wasn’t until the 1930s that the process evolved into commercial-scale manufacturing of continuous fibers, which would later be used as structural reinforcements. Patent applications filed between 1933 and 1937 by Games Slayter, John Thomas and Dale Kleist, employees of Owens-Illinois Glass Co. (Toledo, Ohio), record the key developments that step-changed the industry from producing discontinuous-fiber glass wool to making continuous glass filaments with diameters as small as 4 microns (4 millionths of a meter) and thousands of feet long. Ensuing breakthroughs made the process commercially viable and cost-competitive.


The last two patents in the series, entitled “Textile Material” and “Glass Fabric,” foreshadowed the future of glass fiber as a textile reinforcement. The patents were awarded in 1938, the same year that Owens-Illinois and Corning Glass Works (Corning, N.Y.) joined to form Owens-Corning Fiberglas Corp. (OCF).


The new company marketed its glass fiber under the trade name Fiberglas, which was the genesis of the common generic reference to fiberglass. It was not long before a number of other manufacturers entered the market and, through numerous process and product innovations, contributed to a worldwide structural composite reinforcements market of roughly 4 to 5 million tons per year.


Source: Composite World:

Following are some Glass Fibers available in the market: 

AR-Glass * C-Glass * E-Glass * ECR-Glass * L-Glass * Quartz Glass * R-Glass * S1-Glass * S2-Glass * S3-Glass * Silica Glass * Other

Manufacturing Of Glass Fibers

The glass fiber process

Textile-grade glass fibers are made from silica (SiO2) sand, which melts at 1720°C/3128°F. SiO2 is also the basic element in quartz, a naturally occurring rock. Quartz, however, is crystalline (rigid, highly ordered atomic structure) and is 99 percent or more SiO2. If SiO2 is heated above 1200°C/2192°F then cooled ambiently, it crystallizes and becomes quartz.

Glass is produced by altering the temperature and cooldown rates. If pure SiO2 is heated to 1720°C/3128°F then cooled quickly, crystallization can be prevented and the process yields the amorphous or randomly ordered atomic structure we know as glass.

Although continuously refined and improved, today’s glass fiber manufacturers combine this high heat/quick cool strategy with other steps in a process that is basically the same as that developed in the 1930s, albeit on a much larger scale. This process can be broken down into five basic steps: batching, melting, fiberization, coating and drying/packaging.

Step 1: Batching

Although a viable commercial glass fiber can be made from silica alone, other ingredients are added to reduce the working temperature and impart other properties that are useful in specific applications.

For example, E-glass, originally aimed at electrical applications, with a composition including SiO2, AI2O3(aluminum oxide or alumina), CaO (calcium oxide or lime) and MgO (magnesium oxide or magnesia), was developed as a more alkali-resistant alternative to the original soda lime glass. Later, boron was added via B2O3 (boron oxide) to increase the difference between the temperatures at which the E-glass batch melted and at which it formed a crystalline structure to prevent clogging of the nozzles used in fiberization (Step 3, below).

S-glass fibers, developed for higher strength, are based on a SiO2-AI2O3-MgO formulation but contain higher percentages of SiO2 for applications in which tensile strength is the most important property.

In the initial stage of glass manufacture, therefore, these materials must be carefully weighed in exact quantities and thoroughly mixed (batched). Batching has become automated, using computerized weighing units and enclosed material transport systems. For example, in Owens Corning’s plant in Taloja, India, each ingredient is transported via pneumatic conveyors to its designated multistory storage bin (silo), which is capable of holding 70 to 260 ft³ (1.98 to 7.36m³) of material. Directly beneath each bin is an automated weighing and feeding system, which transfers the precise amount of each ingredient to a pneumatic blender in the batch house basement.

Step 2: Melting

From the batch house, another pneumatic conveyor sends the mixture to a high temperature (≈1400ºC/2552ºF) natural gas-fired furnace for melting.

Glass Melting

The furnace is typically divided into three sections, with channels that aid glass flow.

The first section receives the batch, where melting occurs and uniformity is increased, including removal of bubbles. The molten glass then flows into the refiner, where its temperature is reduced to 1370ºC/2500ºF. The final section is the forehearth, beneath which is located a series of four to seven bushings that, in the next step, are used to extrude the molten glass into fibers. Large furnaces have several channels, each with its own forehearth.
According to Scott Northrup, global business development director for AGY (Aiken, S.C.), furnace operation is being improved on several fronts.

The use of larger furnaces has increased throughput to between 30,000 and 40,000 metric tonnes (66.2 million lb to 88.2 million lb) per year.

One of the most important advances has been digital control technology. “Digital controls … measure and manage the precise temperature of the glass as it moves through the furnace as well as the gas … and oxygen flow rates.” They also maintain a smoother, steadier flow to the fiberization equipment, avoiding air bubbles or other interruptions that could cause discontinuities in fiber formation.

Control of oxygen flow rates are crucial because furnaces that use the latest technology burn nearly pure oxygen instead of air because it helps the natural gas fuel to burn cleaner and hotter, melting glass more efficiently. It also lowers operating costs by using less energy and reduces nitrogen oxide (NOx) emissions by 75 percent and carbon dioxide (CO2) emissions by 40 percent.

Because the furnace is a consumable — the process of melting and moving the glass wears away the refractory bricks that line the furnace interior — efforts are being made to increase the brick’s service life.

Glass fiber production is a continuous process, says AGY sales and marketing VP Drew Walker, “Once production begins, you don’t shut it down.”

Manufacturers say that a typical furnace averages 12 to 15 years between rebuilds, with seven years as a worst-case scenario. Walker explains that at up to $150 million for construction of a new manufacturing site and $10 million to $15 million for a new furnace or rebuild, extending furnace life translates directly into dollars.

The industry takes three main approaches to glass melting:

(1) indirect melt (also called marble remelt);

(2) direct melt using larger-scale furnaces (8,000 to 100,000 metric tonnes per year); and

(3) direct melt using smaller-scale furnaces (150 to 200 metric tonnes per year), which are also called paramelters.

For indirect marble remelt, molten glass is sheared and rolled into marbles roughly 0.62 inch (15 to 16 mm) in diameter, which are cooled, packaged and then transported to a fiber manufacturing facility where they are remelted for fiberization (see “Step 3”). The marbles facilitate visual inspection of the glass for impurities, resulting in a more consistent product.

The direct melt process transfers molten glass in the furnace directly to fiber-forming equipment. Because direct melting eliminates the intermediate steps and the cost of forming marbles, it has become the most widely used method.

Step 3: Fiberization

Glass fiber formation, or fiberization, involves a combination of extrusion and attenuation.

In extrusion, the molten glass passes out of the forehearth through a bushing made of an erosion-resistant platinum/rhodium alloy with very fine orifices, from 200 to as many as 8,000. Bushing plates are heated electronically, and their temperature is precisely controlled to maintain a constant glass viscosity. Water jets cool the filaments as they exit the bushing at roughly 1204ºC/2200ºF.

Attenuation is the process of mechanically drawing the extruded streams of molten glass into fibrous elements called filaments, with a diameter ranging from 4 μm to 34 μm (one-tenth the diameter of a human hair).

A high-speed winder catches the molten streams and, because it revolves at a circumferential speed of ~2 miles/~3 km per minute (much faster than the molten glass exits the bushings), tension is applied, drawing them into thin filaments.
The bushings are expensive, and their nozzle design is critical to fiberization. Nozzle diameter determines filament diameter, and the nozzle quantity equals the number of ends.

A 4,000-nozzle bushing may be used to produce a single roving product or the process can be configured to make four rovings with 1,000 ends each. The bushing also controls the fiber yield or yards of fiber per pound of glass.

(The metric unit, tex, measures fiber linear density; 1 tex = 1 g/km, and yield is the inverse, yd/lb.) A fiber with a yield of 1,800 yd/lb (275 tex) would have a smaller diameter than a 56 yd/lb (8,890 tex) fiber, and an 800-nozzle bushing produces a smaller yield than a 4,000-nozzle bushing. This helps to explain why Wisdom Dzotsi, Americas glass business manager for OCV Reinforcements (Toledo, Ohio, a combination of the reinforcements and fabrics businesses of Owens Corning and Saint-Gobain Vetrotex), views a 4,000-nozzle bushing as the sweet spot that has evolved for optimizing production flexibility.

In contrast, AGY uses 800-orifice bushings because, as Walker explains, “We are a smaller company whose glass yarn and specialty fiber business is based on finer filaments and smaller-run niche products.”

Bushing design is advancing. Kevin Richardson, market development director for PPG Industries (Pittsburgh, Pa.) notes, “There are emerging developments in bushing design that further enhance performance via tailored filament diameters and also contribute to total furnace throughputs, lowering cost.” AGY agrees, stating that the range of fiber diameter, or micronage, has become more varied as composite reinforcements have become more specialized. Although OCV sees 17 μm and 24 μm as the most popular diameters, its reinforcement products vary from 4 μm to 32 μm, while AGY’s products typically fall in the 4 μm to 9 μm range.

Walker notes that all fiberglass manufacturers want to produce as much glass fiber per hour as possible. Advances in winding have enabled producers to triple efficiency. Walker explains, “We process more packages at once now; 20 years ago we may have used two packages where now it is common to use six.” (See “Step 5.”)

Step 4: Coating

In the final stage, a chemical coating, or size, is applied. (Although the terms binder, size and sizing often are used interchangeably in the industry, size is the correct term for the coating applied, and sizing is the process used to apply it. See “Learn More,” at right.)
Size is typically added at 0.5 to 2.0 percent by weight and may include lubricants, binders and/or coupling agents. The lubricants help to protect the filaments from abrading and breaking as they are collected and wound into forming packages and, later, when they are processed by weavers or other converters into fabrics or other reinforcement forms.

Coupling agents cause the fiber to have an affinity for a particular resin chemistry, improving resin wetout and strengthening the adhesive bond at the fiber-matrix interface.

Some size chemistries are compatible only with polyester resin and some only with epoxy while others may be used with a variety of resins.

AGY, OCV and PPG agree that size chemistry is crucial to glass fiber performance, and each company considers its size chemistry to be proprietary.

PPG believes that in many composite applications, performance can be achieved via size chemistry as effectively as, if not more than, glass batch chemistry. For example, its 2026 size chemistry used with HYBON products for wind blades reportedly achieves an order of magnitude improvement in blade fatigue life by  improving fiber wet out and fiber adhesion to all resin types.

Step 5: Drying/packaging

Finally, the drawn, sized filaments are collected together into a bundle, forming a glass strand composed of 51 to 1,624 filaments. The strand is wound onto a drum into a forming package that resembles a spool of thread. The forming packages, still wet from water cooling and sizing, are then dried in an oven, and afterward they are ready to be palletized and shipped or further processed into chopped fiber, roving or yarn.

Roving is a collection of strands with little or no twist. An assembled roving, for example, made from 10 to 15 strands wound together into a multi-end roving package, requires additional handling and processing steps.

Yarn is made from one or more strands, which may be twisted to protect the integrity of the yarn during subsequent processing operations, such as weaving.

One process, many products

Although the basic glass fiber process has changed little since its commercialization 80 years ago, it has undergone many refinements. Two continuous threads run through fiberglass manufacturing’s history: the drive to increase production throughput and bring cost down and the desire to improve the performance properties of the finished product.

Manufacturers continue to push forward on both fronts in their pursuit of ever-newer applications for fiberglass-reinforced composite.

Source: Composite World:

Posted on

About Basalt Fibers

From Wikipedia, the free encyclopedia, further information about the basalt and its unique properties:

Basalt fiber is a material made from extremely fine fibers of basalt, which is composed of the minerals plagioclasepyroxene, and olivine. It is similar to carbon fiber and fiberglass, having better physical properties than fiberglass, but being significantly cheaper than carbon fiber. It is used as a fireproof textile in the aerospace and automotive industries and can also be used as a composite to produce products such as camera tripods.

Basalt fiber is made from a single material, crushed basalt, from a carefully chosen quarry source and unlike other materials such as glass fiber, essentially no materials are added. The basalt is simply washed and then melted.

The manufacture of basalt fiber requires the melting of the quarried basalt rock at about 1,400 °C (2,550 °F). The molten rock is then extruded through small nozzles to produce continuous filaments of basalt fiber.

There are three main manufacturing techniques, which are

  • centrifugal-blowing,
  • centrifugal-multi roll and
  • die-blowing

The fibers typically have a filament diameter of between 9 and 13 µm which is far enough above the respiratory limit of 5 µm to make basalt fiber a suitable replacement for asbestos. They also have a high elastic modulus, resulting in excellent specific tenacity—three times that of steel.

Property Value
Tensile strength 4.84 GPa
Elastic modulus 89 GPa
Elongation at break 3.15%
Density 2.7 g/cm³

Outstanding Properties of Basalt Fibers: 

• High tensile strength
• Alkali resistant
• High thermal conductivity
• No carcinogenic risk or other health hazards
• Completely inert with no environmental risks
• Resistant to acids and aggressive chemicals
• High E modulus resulting in excellent specific tenacity, three times that of steel fiber
• Good fatigue resistance
• Electro-magnetic resistant