Functionalized Silica Fillers for Advance Applications

TAGS:  Polymer Reinforcement      Silicas    

Plastic resins are compounded with a wide variety of mineral fillers. Most mineral fillers have served an important cost reducing role by replacing the more expensive resin in a given compound. However, major suppliers in the silica-based talc filler segment have made great strides in offering functionalized recently. These fillers enhance key plastic properties, such as: Flexural, stiffness and impact strength.

Key functional filler suppliers are expanding capacity and improving their filler manufacturing process technology. The overall silica fillers market is growing on an average at 5% annually and is being led by these cost-effective functionalized fillers.

These functionalized fillers are being used in a broad range of applications that include anti-blocking transparent films, improved flow plastic compounds, LEDs, and 3D printing.

Let’s also take a look at the most recent innovations in surface modification and improved dispersion of mineral fillers.

Want to know more about silica-based talc? Find out here!

Significant Features of Silica-based Talc

Talc comes from earth mining with different type deposits yielding materials based on a given platelet size with their own unique property profiles. With further proprietary processing, talc fillers are tailored to meet specific compounded plastic properties.



Thermoplastics have historically used silica-based talc as reinforcement. It exhibits a strong machine direction reinforcing capability due to its plate-like structure, typical of anisotropic materials.

• Like wood that is strong along the grain, talc is robust along its plate structure but weaker in its cross direction.
• Also, talc shows reduced warping accompanied by good mechanical properties.
• Further, its non-wetting, hydrophobic nature allows for easy dispersion in a broad range of plastic resins.

No wetting or dispersing agents are required in silica-based talc. However, flowability is a challenge in talc compounding due to its plate-like structure.

Additionally, talc appears fluffy or fleecy in appearance. This compounding challenge is most apparent in engineered, small particle size talc grades that further exhibit narrower particle size ranges. Further talc compaction prior to feeding into the polymer melt will counter this obstacle. Specialized material handling and feeding device equipment is the key here.

Micronized Talc Advances

#1. IMI Fabi's Specialty Product Range

HTP1s Talc Grade

Italian supplier IMI Fabi has an extremely micronized commercial HTP1s talc grade. It increases HTP1s flowability through a bulk density increase by a factor of 2.5 versus standard loose powder and compacted talc.

• It accomplishes this flow improvement via compacting talc into sphere-shaped particles.
• This HTP1s talc grade shape makes it in essence frictionless while flowing and is maintained throughout the blending process with the plastic resin. With this uniform flowability HTP1s assists in allowing all additives to attain very uniform levels at the compound formulation stage.
• Also, HTP1s can be used in powder based dryblend compounds due to its excellent dispersibility.

HVTultraC

• The HVTultraC grade is focused on automotive applications, such as: Dashboards and bumpers, as well as other industrial scratch resistant applications.
• It has a tailored stiffness to impact capability in thermoplastic polyolefin (TPO) compounds, combining enhanced stiffness and dimensional balance with improved low-temperature brittle break performance.
• Beyond TPO use, HVTultraC works in a similar fashion with established automotive engineering plastics, such as: PolyButylene Terephthalate (PBT) and PolyAmide 66 (PA 66, or nylon).

NB240

Elsewhere, application development wise; the NB240 talc grade finds use in PolyEthylene (PE) film. It provides extrusion slip performance and lower barrel and screw wear, along with anti-blocking and transparency features.

#2. Imerys High Aspect Ratio (HAR) 3G Talc Products

Continuing, Imerys Performance Additives has commercialized unique High Aspect Ratio (HAR) talc products namely, HAR® 3G T84 and HAR® 3G T77. Two talc products, HAR® 3G T84 and HAR® 3G T77 are specialty milled via a patented process that improve automotive PolyPropylene (PP) and Thermoplastic PolyOlefin (TPO) compounds. Property enhancements include improved stiffness up to 30%, dimensional control, and temperature aging. Further, these HAR 3G grades will reduce automotive part weights and wall thicknesses that in turn translate into tighter vehicle fit and finish tolerances. Imerys' Other Developments In terms of more cost-effective talcs, Imerys offers two JetFil® grades namely, V625C  and V7000 with high platelet counts to maximize reinforcement strength. In addition, it has also developed a densified and compacted Nicron™ 674C talc grade. It will find use in PP and TPO compounds targeted at appliance and packaging end-uses, as well as automotive markets.

Imerys’ HAR (Dark Green) Talc Performance,  20% Loading in PP Copolymer

#3. HPF The Mineral Engineer's Functionalized Silica-based Materials

The Quarzwerke Group’s division, HPF The Mineral Engineers, has been doing early development work on functionalized silica-based materials, such as mica and wollastonite for 3D printing Acrylonitrile Butadiene Styrene (ABS) compounds. The goal here is to improve processing speed, stiffness, and surface quality in FDM (Fused Deposition Modeling) and its complementary FFF (Fused Filament Fabrication) 3D printing technologies.


HPF is experimenting with a range of silica-based particle sizes and shapes. Using silica-based fillers can significantly decrease warpage in finished 3D printed plastic parts.

• HPF’s work with their functionalized silica fillers involves milling processing to not only vary particle shapes and sizes, but also surface modifying to the point of offering silica coating products. Uniform silica grain sizes need to be in sync with FDM (or Arburg’s FFF) filament die diameters.
• Another key to this research is to see if HPF silica variants can be improved to strengthen 3D printing layer to layer adhesion to increase mechanical strength properties.

Historically, 3D printable resin systems drop off a third in properties due to their current layer to layer adhesion strengths. Beyond ABS resin work, HPF is working with Polyamide 6 (PA6. Or nylon 6) and renewable content PolyLactic Acid (PLA) resins.

Surface Modifying Mineral Fillers

The Quarzwerke Group subsidiary HPF The Mineral Engineers have recently developed advanced functional filler systems for PolyAmide (PA, or Nylon). These functionalized mineral fillers when compounded into higher temperature nylons are capable of replacing high performance PolyPhenylene Sulfide (PPS) plastics. Other high performance nylon grades being developed include PA610, PA6T/6 and PA9T.

HPF’s technology development centers around tailored mineral filler surface treatments. Mineral fillers as a rule are high polarity in nature and have high surface tensions. Conversely, plastics into which mineral fillers are compounded exhibit low polarity and low surface tension. When mineral fillers and plastics are compounded together a high surface interfacial energy is produced and the two phases (plastic, mineral filler) separate. To counter this separation tendency HPF has tested various mineral modifications with silanes and related organic molecules that lower interfacial tension, allowing the two phases to be compatible.

Extensive surface treatments on a whole range of minerals such as mica, kaolin, and wollastonite have been documented by HPF. These surface treatments have been developed with higher temperature resistance, and thus are suitable for the higher processing temperatures in engineering plastics like high end PAs. In terms of mechanical properties, excellent elongation at break results were evidenced when an HPF long needle wollastonite mineral or Tremin 939 was compounded into PA 610, and when a short needle wollastonite or Tremin 283 was formulated into PA6T/6.


HPF Data Showing the Effect of Various Filler Treatments on Elongation at Break in PA Compounds

These HPF mineral filler surface treatments are effective at processing temperatures up to 330°C, and are useful in the highest temperature PAs like PA9T. Elsewhere HPF is utilizing their surface treatments in lower processing plastics such as PA6 and PolyPropylene (PP), with an eye to enhancing processability and impact strength.

Improved Mineral Filler Dispersion

Uniform mineral filler dispersion in plastics compounding is important, otherwise agglomerates show up in the polymer matrix, which in turn leads to low toughness/high stiffness imbalance in the finished material. Here historically Evonik has led with additive development to improve filler dispersion in polymer matrices. The key additives here are Evonik’s Tegomer® and Tegopren®, based on Organo-Modified Siloxane (OMS) chemistry.

Evonik’s OMS chemistry in highly filled inorganic compounds provides enhanced melt flow together with significantly reducing processing equipment surface abrasion. Tegopren® 6875 was the initially commercialized OMS type additive. Recently a Tegopren® 6879 has come into use containing silyl functionalities. They are unique in that they generate no Volatile Organic Compounds (VOCs). These additives produce outstanding hydrophobic surfaces on the mineral fillers, and they are effective as well with colorants and nitrogen or phosphorous-based flame retardants. Also, they are United States Food and Drug Administration (US FDA) and European Union (EU) food contact regulation compliant.


Evonik’s Tegopren® 6875 ‘Hydrophobizing’ Filler Surfaces (L) such that TiO₂ Will Float on Water (R)

Talc Process Enhancements

Huber Engineered Materials (U.S.) $300 million, silica-based additives business was fully acquired in late 2017 by major plastics raw material supplier - Evonik (Germany). Its product line is currently Huber Silica.

Historically, since the 1950s silica-based products, like - talc are first mined and then have been further batch processed from agglomerates. And finally, they are mechanically milled into targeted particle sizes for application development purposes.

Huber Silica has researched, developed, and commercialized a new continuous silica process manufacturing technology. This continuous process technology is capable of providing a range of particle sizes and porosities without the need for mechanical milling. This technology has been patented and is trade named as Spherilex.

Silent Features of New Silica Process Manufacturing Technology - Spherilex

• Evonik’s new technology operates by varying reactor process conditions, like: Temperature, pressure and flow rates. This, in turn, translates into a variety of particle sizes, size distributions, and porosity levels for optimizing thermoplastic compounds. The capability to control these process features can, for example, allow for tailoring to a narrow particle size and distribution for transparent anti-blocking talcs used in plastic PolyEthylene (PE) and PolyPropylene (PP) films. These specialized talcs operate in narrow refractive index ranges, and their anti-blocking feature can keep film layers from adhering to one another during unwinding.


• The Spherilex talc additive slightly roughens the film surface to effectively anti-block or breaks the static attraction between the film layers, while not interfering with the basic film transparency level.


• Furthermore, this processing capability can be adjusted to different film thicknesses, either as single film layers and equally important and doable in multilayer films.


• Similarly, with Spherilex talc’s lower porosity, it can be made to order allowing for its use as a carrier to incorporate other processing aids into standard silica master batches. These processing aids include:
  • Slip agents
  • Heat stabilizers, and
  • Ultraviolet enhancements


• Finally, with Spherilex technology, talc particle shapes and sizes can be custom manufactured. This can minimize plastic equipment screw and barrel wear, for ease of product transitions as well as efficient downtime management.

Application of Spherilex Functionalized Talc

LED (Light Emitting Diode) light bulb covers are a high-tech application for Spherilex functionalized talc. Traditionally, LED lighting yields very bright white, single direction, sort of harsh lighting effects. And lampshades or lenses are designed to diffuse an LED light source whether in a household or an automotive application use.

At low, less than 2-5% loadings, tailored Evonik Spherilex talc can efficiently diffuse light when incorporated into an LED bulb or lens cover plastic compound. This approach minimizes secondary needs for diffusing light via lampshades or more importantly through more expensively designed lens molds.

Glass Microsphere Improvements

In conclusion, another aspect of functionalized silica fillers involves glass microspheres both in hollow and solid forms.

In essence, these microspheres perform a role that is midway between a functionalized talc filler and standard glass fiber reinforcement. Microspheres have a 1 aspect ratio that will provide low warpage in narrow tolerance molded parts where improvements are required in:

• Stiffness
• Abrasion resistance, and
• Harsh chemical exposure

Glass microspheres are surface etched and coated for improved plastic resin bonding.

PQ Corporation's Cost-Effective High Glass Microsphere

PQ Corporation, traditionally known as Potters Industries, is the major global supplier of glass microspheres. Precision engineered glass microspheres can be loaded into plastic compounds at higher levels compared to talc mineral fillers. Yet even with high glass microsphere loadings versus talc or other mineral fillers, they effectively lower a given plastic compound’s viscosity. This in turn improves the compound’s flow leading to increased molded part or extruded throughput production.

Also, and equally important, due to high glass microsphere loadings compound and part costs are significantly reduced. In addition, microspheres will improve overall injection molding flowability when used in combination with glass, carbon, or aramid fibers, or other miscellaneous flake or filler particle shapes.

Glass microspheres are available in solid and hollow form.

• Solid microspheres are 2 & 1/2 times heavier than hollow microspheres.
• Hollow microspheres offer maximum volume displacement and therefore part weight reduction, along with enhanced thermal insulation performance.

Glass microsphere compounding is straight forward. With their smooth spherical shape, glass microspheres take less process energy to compound into plastic resins, whether thermoplastic or thermoset based. Microspheres also have small surface areas that help maintain a low viscosity level at high load rates and in turn less plastic resin in the compound recipe. Their spherical shape minimizes plastic equipment screw and barrel wear.

PQ Corporation has maintained-long term microsphere development programs to continually improve strength, whiter appearance variants, small particle size grades, and lower density products.

Commercially Available Silica Fillers

Check out all silica filler grades available in market here!