Plastic additives and fillers are compounds used to be mixed into plastic materials during the manufacturing process, for the purpose of changing some of their properties. While additives are created purely to transform plastics, adding to them properties that were not originally available to meet a broader range of uses, mixing agent (also known as fillers) is used with the goal of reducing the cost of raw materials.
What is plastic filler?
Fillers are basically materials that can be blended into another material and form a composite. If the performance factor and the processability of the final mixture are ignored, any material can be used as a filler, as long as they and the main material can be mixed well. With the important goal of reducing raw material costs, fillers are a large market, with current annual output estimated at 53 million tons, produced by more than 700 companies worldwide. Although fillers can be used in a wide variety of materials, but their two largest segments are elastomers and plastics. With the long-term tendency of plastic prices to inevitably increase when the abundance of oil and gas decreases, plus the times when the price of plastic spikes due to market fluctuations, mineral fillers abundant supply and much lower prices are becoming more and more commercially attractive.
But one thing that many plastic product manufacturers are interested in, is the use of fillers, will it reduce the performance of plastic?
In the past, the use of fillers to blend into plastic materials was seen as a trick of the manufacturers. By blending a cheaper raw material into the main ingredient, they can earn more profits, giving themselves a competitive advantage in price. The use of fillers in the past will almost certainly result in significant reductions in product performance and quality. Finding the ideal filler blends without sacrificing quality can be seen as a huge success. Such recipes are always kept secret. Accepting lower profits when using 100% virgin plastic resin, in order to create products of outstanding quality, has been the pride of many businesses, including our company. Most people think that plastic with fillers is a cheap commodity and should only be used in the secondary market. Their characteristic is that the product surface lacks perfection, the color is opaque and is easily punctured, torn, ...
But with the development of materials science, that is most likely no longer true. Today's modern fillers no longer degrade the performance of the plastic too much, and can even improve the product, adding to the plastic unique properties that the plastic material itself does not have. With the leading common filler being CaCO3 aka Taical, numerous tests have shown that, at 5% blend in LDPE resin, strength and tensile yield in both horizontal and machine direction (TD) and MD) are both improved. At 11% to 20% CaCO3, tensile strength decreased but not lower than unadulterated level, but in return puncture resistance and tear strength increased. At this mixing ratio, the mixture of resin and CaCO3 also exerts less pressure on the machine components, allowing the screw speed to be increased with a constant amperage. That means output can go higher than usual. The anti-blocking ability is also much improved, allowing you to further reduce the cost of this additive.
The characteristic roughness of the surface of plastic films using CaCO3 fillers is sometimes not entirely a defect. Such surfaces can improve the adhesion of printing ink, making them very suitable for printing. We can even eliminate the corona treatment step in the production process with a suitable filler content.
Undeniably, the competitive pressure on price is the leading reason why manufacturers are interested in fillers. But it is a fact that mixing plastic with fillers is becoming more and more interesting. If we understand their properties, we can create many outstanding ingredient recipes Perhaps that's why manufacturers are more and more reckless about the level of fillers in their products. Many Vietnamese manufacturers have successfully produced high quality plastic bags with filler content up to 25%, a ratio unprecedented for blown film applications. Even a few savvy customers have begun specifying the filler content in the products that they order to reduce costs.
Indeed, fillers in the plastic industry are gradually removing bad stereotypes and are no longer considered a "bad word" in the industry. In the near future, companies with a tradition of using 100% of raw materials are virgin plastic resins like us, may also have to change attitudes.
Calcium carbonate CaCO3 also known as rock powder
Criteria for choosing the right filler for plastic
In theory, any material that can be transformed into small granules could be used as a filler for plastics. For example, we can use sand as a filler, and the end result is that in the plastic there will be sand particles. The possibilities for combining resins with other materials are endless, but for successful mixing, the filler needs to melt and disperse well in the resin mix. At higher technical requirements, they must be chemically inert, free of metal impurities to avoid plastic degradation, low hardness to avoid wear of equipment, and most importantly, the cost must be cheap and readily available to be suitable for commercial use.
No plastic is perfect, and no filler is ideal either. The essence of using fillers is a compromise between properties that will be improved and those that will be lost. To get the best trade-off, manufacturers need to understand the properties of fillers, and how they will interact with the plastic.
There is something quite special, is that knowing the chemical composition of fillers will not help much to use them. Because in most cases, chemicals have no effect on plastic. The real things of concern for fillers are the physical parameters, including particle size and shape, and their surface area.
particle size
The particle size distribution is an important physical parameter of powdered materials, described in research reports with 3 indexes as D10, D50 and D90. A value of index D10 or DV (0.1) indicates that 10% of the particles in the dough will be less than this size. D90 or DV (0.9) means 90% of the total particles are less than this size. And D50 DV (0.5) means 50% of the total particles are less than this size. Particle size values are usually given in micrometers (μm). As an example: if the D50 index of a powder is 4 μm, 50% of the particles in the powder will be less than 4 μm in size, which means 50% will be larger than this size. D50 is considered the average value, and when talking about grain size, it is usually only this value in mind. The D50 index also often appears on product data sheets published by manufacturers. However, rarely seen indices such as D10 and D90, representing the size of the largest and smallest particles present in the material are the really important indicators.
The use of fillers has a rule, that the larger the size of the filler particles, the worse the problems will occur. Particles larger than 10 microns will begin to seriously affect the impact resistance and strength and ductility of the plastic. Larger and coarser particles also result in poor plastic surface quality and low gloss. In most cases this will be a failed blending product, but there are exceptions when plastic film manufacturers intentionally mix fillers with large particle sizes, in order to create a matte film surface. and purposefully roughened.
The smaller the particle size, the higher the dispersion in the mixture, the product surface will be smooth and glossy. Particles smaller than 100 nanometers (by 0.1 micrometers) are called nanoparticles, which have the effect of coating and repairing defects on the surface of the material. In practice, however, these ultrafine particles tend to stick together into larger particles, and the attraction between these fine particles can also increase the viscosity of the mixture.
It can be seen that the average particle size value D50 does not completely determine the yield of the filler material, but also needs to consider the remaining two particle size values. One thing to keep in mind is that the particle size value is not a constant for each material, but is determined by the manufacturing process and technology.
particle shape
Fillers can have many shapes, but for simplicity we can group them into three groups:
Round or cubic particles of which Calcium carbonate or glass are typical examples. This grain shape increases stiffness but reduces strength somewhat, with little effect on impact strength and elongation at break.
The fibrous form is characterized by wollastonite and glass fiber, which have a reinforcing effect on plastics if the aspect ratio is high enough and well bonded to the surrounding polymer. The most important property of fibrous fillers is the aspect ratio, which is calculated as the largest dimension (length) divided by the smallest dimension (diameter). For example, a fibrous material is 10 microns long and 1 micron in diameter, their aspect ratio is 10:1.
The flat disc shape, or platy, which is characterized by Talc and Mica, can also reinforce the material in principle the higher the aspect ratio, the more effective it is. This shape helps the filler reinforce the main material in both the lateral and longitudinal directions, while the thread form reinforces it along the length. This platy sheet shape also imparts gas and liquid barrier properties to the plastic.
Filler shape and aspect ratio are important parameters, but it is rarely shown in the literature and tachnical data sheet of the filler. This is because measurements are extremely difficult to make, and the shape or aspect ratio of the grain is also often significantly affected in the direction of reduction or breakdown during material handling. This causes the specifications in the filler data sheet to not match the aspect ratio of the particles inside the final product.
surface area
The surface of the particles determines their interactions with other particles, and with the surrounding polymer molecules. The larger the area, the higher the adhesion, which improves the tensile and flexural strength. This principle is the same as before gluing objects together, or before painting something, people often sand them. Sanding will create protrusions and increase the contact surface area, thereby improving adhesion.
However, good adhesion will also create agglomeration and more viscosity, making the process of the resin mixture running through the screw encounter certain difficulties.
In addition to the above parameters, there are many factors that combine that will determine the success or failure of your filler application. Working with plastic is not easy, technical errors in the production of plastic packaging can appear with more frequency when more substances are added to the plastic. For a plastic composite, all the flow behavior, viscous properties, elasticity and flow characteristics when molten greatly affect the processing. However, there is no need to worry, just like when you use plastic colorants, filler suppliers will also fully advise you on the right mix type and ratio.
grain shape of some common plastic fillers
Some common fillers in the plastic and plastic packaging industry
There are 4 fillers most commonly used in the plastic industry in general and in plastic packaging in particular, namely Calcium carbonate, Talc, Sodium sulfate and Barium sulfate. Calcium carbonate has the strength of price, Talc has the strength of reinforcement, and Sodium sulfate and Barium sulfate have the ability to increase transparency. Some other fillers such as mica, Wollastonite, kaolin and glass granules are used less because of their low economic efficiency. They are mainly used in engineering plastics and some special cases.
Calcium carbonate filler
Calcium carbonate (CaCO3) is a relatively inexpensive and abundant natural mineral that makes up more than 4% of the earth's crust. The economic attractiveness makes CaCO3 the most popular filler, a viable option to combat cycles of plastic price volatility. They are non-toxic, odorless, white with a low refractive index, soft, dry and stable over a wide temperature range. Calcium carbonate powder is best compatible with PP and PE plastic, but can still be mixed with some other popular resins such as PS, ABS, PVC, EPS, ...
In North America, CaCO3 is mainly ground from marble, while in other parts of the world it is derived from chalk, limestone and even marble. All three rocks are chemically similar, but chalk and limestone are geologically younger and need to be pre-treated to remove moisture before they are formed into a concentrated form. Ground Calcium carbonate (GCC) has more impurities, larger particle size and coarser than precipitated Calcium carbonate (PCC) prepared from calcium oxide.
In addition to the cost advantage, CaCO3 has a very good property of creating a more opaque and whitening effect on the plastic, which saves the rather expensive TiO2 white particles when white packaging is needed. However, the whitening level of CaCO3 only stops at a support level, that is, it cannot completely replace the pigment. In typical opacity plastics such as HDPE, the opacity of the added CaCO3 will not make any significant visual difference.
The opaque nature of CaCO3 makes them unsuitable for products requiring transparency. And with some colors, the opacity of this filler can cause us to expend more pigment than usual. For example, red will turn pink under the influence of CaCO3, and we will need more red pigment, or a darker red to achieve the desired effect.
Calcium carbonate fillers can increase the coefficient of friction, helping to reduce the amount of anti-block additives needed. If you are a manufacturer of polyethylene film, you understand how serious the problem of agglomeration can be. The thin film layers stick together so that the bag cannot be opened, even damaging the membrane surface. Plastic bags with CaCO3 will not stick and are easier to open than usual.
An increase in the coefficient of friction means that the surface of the product will have less shine and a rougher feel. But such a rough surface will increase the surface contact area, making the CaCO3-containing plastic film easier to print. Plastic bags with high friction are also easily stacked neatly, more convenient for packaging.
In terms of physical properties, the most noticeable effect of Calcium carbonate on plastics is that they increase the hardness and impact strength but decrease the tensile strength and elongation at break. In other words, packaging containing CaCO3 filler has high stability, good impact resistance, but becomes less flexible. With too much CaCO3 content, plastic bags will become friable and easily torn.
The Calcium carbonate particles create gaps between the molecules, increasing the rate of water vapor transmission and gas permeation. In other words, they reduce the air tightness of plastic films, but this is a beneficial property for some packaging applications, such as fruit bags. This effect is even used to produce breathable sanitary films for diapers and similar applications, by increasing the Calcium carbonate addition rate to 60% to achieve an open cell structure.
It is worth noting that CaCO3 has a density of 2.71 gram/cm³, three times higher than that of PE plastic with a density of only 0.92 to 0.97 gram/cm³. As a result, the resulting plastic product will also weigh more per unit volume, meaning the number of bags per kilogram of plastic will be reduced. This sometimes makes cost-cutting purposes ineffective and will be a factor to consider when using fillers.
A higher weight density of the resin mix will also reduce blower system productivity per kilogram per hour, but film yield in square meters increases as CaCO3 increases heat transfer. This filler has 5 times higher thermal conductivity than PE plastic, so the plastic mixture will melt faster and more evenly, the cooling process on the roller is also faster. Faster cooling also means less fogging and more stable film bubbles, allowing manufacturers to increase the speed of the extruder without a hitch.
CaCO3's faster cooling properties leading to plastic bags can be heat sealed at lower temperatures than usual. On a heat sealer system, most operators are familiar with raising the temperature when the weld is not tight, but with a high CaCO3 mix, they may have to get used to the opposite, that is temperature reduction.
There is a big difference between the content, blend formula between manufacturers. There are many units that are said to have successfully produced plastic bags that mix up to 30% CaCO3 in the composition, but usually this ratio is only at a maximum of 15% to preserve the characteristics of the plastic. The particle size of CaCO3 when used in the production of plastic bags must be less than 2 microns and coated with a surface treatment so that they can be easily dispersed in the mixture. These treatments will be pre-mixed with the main filler by the filler manufacturers, then condensed into masterbatch pellets similar to the way plastic pigments are produced. For thick and large plastic films, CaCO3 fillers with a larger average size can be used. The large size of the particles will not require a surface treatment to aid dispersion, but such large particles can cause scratches to the very product they protect (as CaCO3 has a fairly high hardness). The hardness of CaCO3 on the Mohs scale is 3, harder than plastic but still smaller than the TiO2 pigment (hardness 5.5) that it is commonly used to replace, and much smaller than the anti-blokking additives commonly made from silica and diatomaceous earth (hardness on the Mohs scale of 7). CaCO3's hardness has also raised concerns that it will cause slight wear to film blower components. But most manufacturers consider this wear insignificant, and can even play a role in cleaning the inside of the machine, replacing periodic chemical treatment.
For woven PP yarn, the use of Calcium carbonate is even encouraged and the additional dosage can be greater than 30%. CaCO3 granules are said to be the perfect solution for manufacturers to partially or completely avoid the fiber problem. Fibrous yarn is an uncontrolled plastic structure separation phenomenon, which is common when stretching PP or PE yarns. With only a small amount of Calcium carbonate, not only this problem is solved, but also can improve the tensile strength and tear resistance of the finished product.
In terms of food safety, Calcium carbonate is an FDA-approved plastic additive for use in food packaging and medical packaging applications. Calcium carbonate is not to worry about, and is even an important ingredient of traditional Chinese medicine. When entering the human body through ingestion, they are also easily dissolved by the acid in the human stomach, then excreted through the digestive tract.
An indispensable weakness of CaCO3 is that they contribute to the process of breaking the plastic molecular chain under light, temperature and other environmental conditions. This fracture process causes the macroscopic performance of the mechanical properties to decrease, which is known as the plastic aging process. Therefore, Calcium carbonate fillers should not be used in outdoor packaging applications, such as greenhouse films or agricultural mulch films.
hardness of some minerals on the Mohs scale
Talc filler
Tacl is the second most popular filler in the plastics industry, second only to Calcium carbonate. It is one of the softest natural minerals known, with the lowest hardness on the Mohs scale (1/10). This property is important, as it makes Talc the least abrasive on plastic production equipment compared to other fillers.
Talc is a mineral with a layered, sheet-like structure consisting of a layer of magnesium hydroxide sandwiched between two layers of silica, with the chemical formula Mg3Si4O10(OH)3. The unusual shape of Talc is also known as the platy. This shape when coupled with a sufficiently high aspect ratio creates excellent reinforcement for the material. Talc and similar shaped fillers are also classified as reinforcing fillers so that they can be easily distinguished from other fillers.
The color of natural Talc can be white, colorless, green or brown. This difference is because depending on the extraction site, Talcum powder can contain different proportions of MgO, SiO2 and H2O. The higher the silicon content in the Talc powders, the purer they will be, the better the performance in the applications will be, and the higher the price.
Many people often confuse Talc with Taical due to the quite similar characters. However, Taical is a popular name in Vietnam for synthetic fillers that are concentrated in the form of masterbatch with the main ingredient being CaCO3. “Taical” is a combination of the first letters of the phrases: Tensile strength (hardness, impact resistance), Agglomeration-free (dispersion), Improve whiteness, Cost- saving, Acording to any mixture ratio, Less shrinkage.
In the past, Talc was mainly used as a filler in polypropylene to increase stiffness. However, the use of Talc has been extended to polyethylene and polyamides in recent times. This filler has the advantage of being chemically inert, insoluble in water, dilute inorganic acids and dilute alkaline solutions. In addition, talc has an affinity for all organic substances, so they are easily dispersed in plastics.
Talc's significant enhancing effect on plastic products mainly comes from its unique microscopic flake structure. When mixed in a resin, it can be uniformly dispersed in a layered form, forming films that improve stiffness, flexural modulus and provide obvious heat retention and resistance. However, this property improvement is within a certain blend content range. After adding talc to polypropylene at a rate of less than 20%, the tensile strength of the finished product will increase slightly. But when the talc content exceeds 20%, the tensile strength of the material begins to gradually decrease due to the intermolecular attraction.
The behavior of talc in plastics is as interesting as their shape. When the resin mixture is pushed through the screw, the talc granules' sheet-like structures are oriented in the extrusion direction. Therefore, their reinforcing ability is very strong in the machine direction but weaker in the horizontal direction. This is a typical property of anisotropic materials, as wood is stronger along the grain.
Although Talc's plate structure contributes to increased stiffness and heat resistance, it significantly reduces impact strength. Whereas Calcium carbonate does not increase hardness and heat resistance as much as talc, but they have almost no adverse effect on impact strength. Talc's plate structure is also detrimental to the molten flow rate of the material.
Talc, Mica, Kaolin and most silicon-based minerals have almost infrared and ultraviolet blocking properties, and have high thermal stability. These properties give plastic products the ability to resist aging. Just like CaCO3, the printability of talc-containing plastic films can also be improved.
Talc has very high thermal stability, up to 900°C and almost no shrinkage. Therefore, in blow molding applications such as plastic bottles, plastic containers, Talc has the effect of increasing the dimensional stability of the product.
Like CaCO3, Talc resin is very popular with manufacturers because it is suitable for most traditional production processes such as blow extrusion, injection molding, and extrusion without having to upgrade equipment. Talc granules are also capable of replacing anti-caking additives such as CaCO3, and are also believed to be safe in food packaging applications. Talc's inertness makes it non-conflicting when mixed with other materials. They are even commonly used in the cosmetic industry because they are hypoallergenic. However, in their natural form, some Talcum powders contain asbestos, which can cause lung cancer when inhaled. In 1976, the Cosmetic, Toiletry, and Fragrance Association (CTFA) issued voluntary guidelines stating that all Talc used in cosmetic products in the United States must not contain trace amounts of asbestos in the United States. detectable level.
talc filler masterbatch
Barium sulfate and Sodium sulfate transparent fillers
While CaCO3 is the leading filler for cost-effective purposes, Talc excels in reinforcing ability, Sodium sulfate (Na2SO4) and Barium sulfate (BaSO4) are considered to characterize the transparent filler group. Talc also has clarity, but much less when compared to Sodium sulfate and Barium sulfate. If the mixing content is too high, Talc will also give the resin an opacity.
Sodium sulfate is an inorganic neutral salt compound also known as the sulfate of soda, appearing as a white, odorless, crystalline solid with a salty or bitter taste and the ability to absorb water. In nature, Sodium sulfate is found in many forms, from the anhydrous form (called the mineral thenardite), to the hydrated decahydrate (called the mineral mirabilite or Glauber's salt).
Nano-grade Na2SO4 filler resin has outstanding surface modification ability, increased gloss, transparency, and improved some mechanical properties such as flow rate, tensile strength, thermal stability and ability anti-blocking ability.
Sodium sulfate is recommended for use in different dosage ratios. In agricultural films or greenhouse films, the recommended mixing ratio is between 5 and 30%. For HDPE or LDPE blown film packaging applications, dosages can be up to 50%.
Barium sulfate (BaSO4) has similar properties to Na2SO4, also good for LDPE and HDPE films, also improves gloss, transparency, tensile strength and hardness of the product. In addition, BaSO4 is resistant to acids and alkaline solutions, has light fastness as well as stable plasticity for a long time. The recommended mixing ratio of BaSO4 is between 5% and 30%, but the ideal ratio for maintaining smooth luster and increasing mechanical properties is said to be at 20%.
The outstanding advantage of BaSO4 filler is that it works effectively not only in blown film products but also in some injection molding products such as small parts of household appliances, bottles. By adding BaSO4 to the formulation, these fillers result in high hardness, corrosion resistance and ideal printability. In extrusion molding application, the use of BaSO4 (about 25%) can make the surface of PP plastic look like ABS plastic without affecting existing properties.
Both Barium and Sodium Sulfate are mainly used for high-grade packaging materials because they are more expensive than talc and CaCO3 (still cheaper and more stable than plastic, of course). The biggest difference between these two types of transparent plastic fillers is that Na2SO4 has a lower lattice energy than the hydration energy, so it can be dissolved in water. Barium sulphate, on the other hand, has a higher lattice energy than the hydration energy, so it is insoluble in water. In simpler words, BaSo4 has stronger and more stable bonding properties than Na2SO4. So, water molecules cannot break the bonds of BaSO4 but can break Na2SO4 bonds. Because BaSO4 is insoluble, they are resistant to moisture, which will be more durable in case the product has water on the surface.
The clarity of Na2SO4 is higher than that of BaSO4, even the best in the group of transparent fillers. However, as a salt, they will have a salty taste, and if used in excess will cause precipitation problems after a long time. Barium sulfate is generally more comprehensive, but the specific gravity is quite high (up to 4.5 grams/cm³), so adding too much will affect the weight of the product.
Mica filler
Mica is a layered silicate, with an octahedral Al2O3 structure sandwiched between two SiO2 tetrahedra, giving it an unusual speculum shape resembling Talc, providing excellent reinforcement to the material. Mica's special properties are its extremely low coefficient of thermal expansion (CTE) and extraordinary insulating properties. Mica has a weight density of about 2.7 grams/cm³ and a hardness of 2.5 on the Mohs scale.
Mica fillers can significantly increase air permeability, but reduce the ductility and flexibility of the material. Tensile strength increases while impact strength and flow rate decrease with increasing mixing ratio.
Mica comes in two common forms, including the most common Muscovite Mica, which is a hydrated silica of potassium and aluminum, and Phlogopite Mica which is a hydrated silica of potassium and magnesium. Muscovit mica is white, while Phlogopite is dark in color but has much higher thermal stability. Both types of fillers behave relatively similarly when it comes to the same particle size and aspect ratio.
Wollastonite filler
Wollastonite (CaSiO3) is a needle-shaped granule, usually appearing as a white powder. CaSiO3 has a rather high hardness compared to other common fillers (4.5 on the Mohs scale), which enhances the hardness and prevents scratches and abrasions of the product. The most common application of CaSiO3 is in the control panels, details of PP plastic interiors on cars. Tests show that the Izod impact force of PP with mixed wollastonite is significantly increased compared to that of unadulterated primary resin.
Wollastonite competes with reinforcing fillers such as Mica and Talc, and can also be used to replace glass fibers in the production of thermoplastics and thermosets. However, the reinforcing effect of wollastonite is not equal to the above-mentioned fillers because their aspect ratio is usually lower. Wollastonite is also not as resistant to acids and bases as other silica-based fillers, but in return they can improve the product's fire resistance, thermal stability and dielectric strength.
The tensile strength and elongation at break of the resin tended to decrease with the addition of wollastonite, but the Young's modulus improved.
Wollastonite filler with needle structure
Kaolin filler
Kaolin is the name for kaolinite clay- Al2Si2O5(OH)4, which is a member of the kaolin aluminosilicate family. It is a white or yellowish-brown soft powder, with a speculum-like granule appearance like Talc and Mica. This shape offers great reinforcement when the aspect ratio is high enough, but in practice it is difficult to make kaolin with such a high aspect ratio. Kaolin in nature has not a large enough aspect ratio but they are inert and cheap, fire resistant, with the main composition of minerals kaolinite, illite, montmorillonite, quartz, ... They have moderate plasticity, friable and easy to crush, with mica and quartz debris in the composition. Whiteness is one of the important parameters that determine the quality and filling performance of kaolin, the higher the purity of the kaolin, the whiter its color.
Kaolin has the ability to increase the physical properties of materials, including tensile strength, resistance to warping and chemical degradation. It also enhances luminosity, making the material look whiter and brighter. Their weight density and stiffness are comparable to Mica, at 2.6 grams/cm³ and 2.5 on the Mohs scale, respectively.
Kaolin filler is widely used in paper, ceramics and refractory materials, then in coatings, rubber fillers, glazes and white cement. Kaolin is used in plastics only in very small quantities, mainly in some engineering plastics, probably because of its poor performance compared to other fillers, which is not commensurate with the cost.
In plastics production, kaolin is mainly used for its anti-blocking properties as well as infrared absorption in applications requiring laser marking. Greenhouse films using kaolin will increase transmission characteristics of short infrared wavelengths, while significantly blocking transmission of long infrared wavelengths, thereby creating a higher degree of "greenhouse effect". Kaolin and EVA (Ethylene-Vinyl Acetate Copolymer) are two materials that have been shown to be long-infrared radiation absorbers without appreciably affecting the mechanical properties or aging behavior of agriculture films.
Kaolin also significantly increases the opacity of the plastic and is often used as a contrast agent for polymer preparations, completely or partially replacing the expensive pigment titanium dioxide.
SiO2- glass filler
Silicon dioxide (SiO2), also known as silica or glass beads, is a chemical compound with a high hardness (7/10 on the Mohs scale), and a density of 2.65 grams/cm³. Filler glass will have different properties depending on whether their bead shape is glass bead, short glass fiber or long glass fiber.
Glass beads are used to increase stiffness, reduce warping, especially in fiberglass filled polymers, which promotes better flow and surface finish. They are especially common in engineering polymers such as nylon, polybutylene terephthalate (PBT), or thermosetting resins such as phenolic resins and epoxy. Using glass beads will greatly reduce the agglomeration in plastic production, while enhancing fire resistance. Even very thin layers of silica deposited on polymer surfaces can reduce heat release and slow down their ignition.
In plastic film packaging, fume silica (fume silica) is used to reinforce and absorb infrared light in greenhouse film products. In bioplastic packaging, SiO2 nanoparticles, when combined with starch-based bags, can help improve many mechanical properties, especially increasing water and gas repellency, absorption capacity, etc. oil absorption and chemical resistance. However, plastic film containing glass filler has poor heat-sealing performance.
Glass fibers are mainly used to increase mechanical properties such as the flexural modulus and tensile strength of thermoplastic or thermosetting plastics. Short high aspect ratio fiberglass or very high aspect ratio long fiberglass, even continuous fiber, can be used to create very effective reinforcement. Nylon, polypropylene and other polymers that are blended with glass fibers are collectively known as Glass Fiber Reinforced Polymer (GFRP), which has the property of being several times stronger and more durable than virgin polymers. Water. Short glass fiber (SGF) is less than 1/2 inch in length, which improves stiffness and impact strength, reducing shrinkage. Long glass fiber (LGF) is 1/2 inch longer, resulting in a stiffer and more impact resistant plastic (especially at cold temperatures), and has a higher tensile strength than mixtures containing SGF equivalent proportions.
A GFRP is typically 10% to 50% fiberglass. Usually, the more fibers, the greater the improvement, as long as the fibers are well blended and the polymer adheres well to the fibers. If the adhesion is poor, the composite may fail, but this adhesion can be improved by treating the fiber or adding bonding agents.
However, the use of glass fillers in plastics faces many obstacles, and the biggest problem is their high cost. Usually, there is no economic benefit to using glass as a filler. Plastics using glass fillers are also highly viscous when melted, making the production process difficult and reducing machine capacity. The high hardness of glass requires special treatment to protect the device from wear.
