Published 3/25/2009

Resin systems update: The greening of thermosets

Thermoset resin formulators seek environmental benefits as customers demand reduced cost and increased performance.

Vicki P. McConnell

This comparison of toughness properties of neat epoxy resin vs. those of a fiber-reinforced laminate indicates the improvement that is possible by using a nanomodified resin system in a molded composite structure. Source: Nanoresins AG

Low-profile/low-emissions and low-density polyester formulations developed by Polytec Composites (Kraichtal-Gochsheim, Germany) bring performance versatility to SMC decklid components in Daimler’s 2008 S-Class Coupe. Source: Polytec Composites

Heavy truck, lightweight hood: The nanofilled low-density polyester resin used in the multipart hood assembly on this Navistar’s Class 8 truck is formulated for a Class A finish and achieves a 21 percent weight savings. Source: Ashland Inc.

This CIPP felt liner, shown as it is readied at the liner plant prior to transportation and installation, is impregnated with a highly thixotropic resin formulated by AOC LLC (Collierville, Tenn.). The resin’s viscosity has minimal impact on pumping and processing, yet will resist draining down or flowing up service connections during installation and cure. Sources: AOC LLC, National Liner, National EnviroTech Group

Nano-enhanced bio-resins for SMC

To gain the secondary green benefit of potential fuel savings and the ability to haul more bulk product at no additional freight cost, fabricator Core Molding Technologies (Columbus, Ohio) recently reduced the weight of a Navistar regional-haul truck hood assembly from 100 lb to 79 lb (45 kg to 36 kg) using its custom-compounded sheet molding compound (SMC), commercialized as Nano-Lite. For the hood, the recipe included low-mass, nanofilled polyester and proprietary low-profile additives, Wallenhorst explains. In the formulation, Ashland’s AROTRAN 720 polyester is used in the hood’s Class A outer skin, but toughened AROTRAN 740 better suits the non-Class A reinforcement panels underneath. The filler ratio encompasses mineral, nanoclay, and one-inch long chopped glass roving at 20, 3 and 39 percent, respectively.

The nanofiller, an alternative to glass microspheres, not only achieved lower molded density (1.55 g/cm³ vs. 1.9 g/cm³ for traditional SMC) but also exhibited no in-resin suspension or Class A surface anomalies. It also enhanced mechanical properties in the reinforcement panels: tensile strength of 105 MPa, flexural strength of 245 MPa, flexural/tensile modulus of 15/12 GPa, notched Izod impact at 73°F/23°C of 950 J/m, with mold shrinkage of only 0.008 percent. All of the composite parts for an initial 40 production hood assemblies passed inspection after a 30-minute topcoat/clear coat paint oven bake at 230°F/110°C.

Ashland evaluated the hood’s Class A surface for surface waviness, orange peel and distinctness-of-image properties with its Advanced Laser Surface Analyzer (ALSA), verifying that it meets Navistar’s standards. To date, the initial 40 hood assemblies have withstood 800,000 equivalent miles (1.3 million km) in accelerated road testing, with no material issues encountered.

Additional structural SMC formulations have been developed by Ashland, with densities of 1.2 g/cm³, and those AROTRAN resins now are used by compounders in the automotive market. The supplier’s AROTRAN 805 polyester in weatherable SMC resin can be pigmented to white or black, offering the environmental plus of eliminating painting, which Wallenhorst connects to reducing volatile organic compounds (VOCs) and waste products.

Although sales of vehicles that historically have used the most SMC — pickup trucks, SUVs, and muscle-class sports cars — have suffered a severe decline, “the automotive market is still very important to us, and we will continue to support the needs of current and future automotive customers,” affirms Mike Dettre, business manager for closed mold resins at AOC LLC (Collierville, Tenn.). “With OEMs reevaluating their product offerings and retooling in line with consumer demand, maybe the paradigm can be broken that says cars must be manufactured primarily from steel.” But Dettre also points out that “SMC spans many markets, including transportation, general construction, electrical, consumer products and marine, and AOC remains firmly dedicated to advancing SMC technology wherever and whenever possible.” Collaborative effort between the OEM, molder and material suppliers “is paramount to get the most from an SMC component,” Dettre emphasizes.

AOC’s Atryl polyester resin sees continued use in Freightliner heavy truck SMC body parts, but ultralow-density (down to 1.3 g/cm³ with microsphere filler) and conductive grades have recently found commercial application, with the supplier’s continued R&D work on carbon-fiber reinforced, nanoclay-filled and UV-stable SMC. Dettre adds that AOC has R&D ongoing with bio-based polyester and natural fiber filler, but he believes “with the recent drop in oil prices, it is not as economically attractive at the moment.”

For Class A body panels on agricultural equipment and automobiles, John Ilkka, closed mold business development manager for Reichhold Inc. (Research Triangle Park, N.C.) says his company’s POLYLITE 31325-00, a new low-viscosity unsaturated polyester, offers a green resin chemistry — 25 percent soy oil-based — that cost-effectively replaces glycol in SMC/BMC (bulk molding compound) composites. Though no automotive applications have been publicized yet, Ilkka says the material is already in commercial use.

Cost-neutral bio-based SMC

At Meridian Automotive Systems (Allen Park, Mich.), SMC parts are compression molded and SMC is formulated in house for specific projects. Jeff Robbins, Meridian’s R&D director, reports that the company has been working on integrating renewable and recycled resins and fillers into SMC for the past several years, along with natural fibers, such as flax. “We have been able to prove cost and performance neutrality with bio-based SMC in several projects. However, customers remain reticent in embracing these resins as truly ‘drop-in’ materials, compared to the petroleum-based resins with which they’re familiar. Currently, there’s probably more intangible desire for a green factor in SMC formulations than there is actual customer acceptance of bio-based resins for commercial products.”

This past November, at the Green Car Conference and Exhibition in Novi, Mich., Meridian displayed a green SMC automotive underbody component that was prototyped, with help from Reichhold, with 30 percent renewable/recycled content. “Most of the effort with this part focused on replacing the polyester and glass filler in traditional SMC,” Robbins explains. The formulation included postconsumer recycled polyethylene terephthalate (PET), postindustrial polystyrene, renewable soy flour and soy resin. Specific gravity was 1.6, a 15 percent reduction from that of traditional SMC parts.

Elsewhere, SMC 0400, a new low-profile, low-VOC SMC formulation from the Automotive Composites Div. of Polytec Group (Horsching, Austria), is designed specifically to meet the requirements of the California Air Resources Board. Based on its low shrinkage rate, surface quality and sufficient temperature resistance to allow inline painting, this glass-reinforced polyester formulation has qualified for use in automotive body panels and trunk lids.

Rudi Kuehfusz, head of engineering at Polytec Composites (Kraichtal-Gochsheim, Germany), reports that Daimler’s 2008 S-Class Coupe features SMC 0400 in the inner shell of the trunk lid, and SMC 0500, a low-density (<1.5 g/cm³), low-emission SMC, is used in the outer shell. In recent developments at Polytec, an additive is now being evaluated that provides significantly lower viscosity in SMC resin/filler paste that could allow bumper beams and other structural automotive parts to be compression molded with glass loading as high as 60 percent.

Bio-resins for building green

In 2002, Ashland pioneered its first “renewable resource-based” resin, ENVIREZ 1807, an unsaturated polyester for SMC that contains up to 25 percent content from renewable resources such as soy oil and corn ethanol. Since then, Ashland has introduced ENVIREZ formulations for infusion (ENVIREZ 86400), resin transfer molding and general laminating (L86300). “These resins contain 12 percent bio-content from recyclate,” says Wallenhorst.

In January, Ashland premiered ENVIREZ 50380 for pultruded products, containing 47 percent recycled bio-content. This formulation has high reactivity that supports fast line speeds and could earn LEED credits in the construction market. “Our customers who pultrude window lineals and other building components have an opportunity to supply builders with products that earn credit toward points under the U.S. Building Code Leadership in Energy and Environmental Design [LEED],” he explains, referencing a rating program developed by the U.S. Green Building Council to encourage green building criteria in both new and renovated construction. The resin’s recycled materials content contributes to LEED points under the program’s Materials and Resource Credits 4.1 and 4.2.

Wallenhorst reports that ENVIREZ resins are experiencing strong customer interest in spite of the current weak economic market, in part because they can be adopted into ongoing projects with little process adjustment. “All our bio-based resins are engineered to be ‘dropped in’ to existing manufacturing processes, and they must prove equal to or better than existing resin formulations in performance. This is crucial to fostering customer acceptance,” Wallenhorst concludes.

Reichhold’s POLYLITE 31325-00, mentioned earlier in reference to automotive SMCs, also is a candidate for composite products that can earn LEED credits. The resin can be used not only in pultruded window lineals but also in exterior residential door skins and electrical boxes, as well as in heating and air-conditioning components.

Green resins go underground

In cured-in-place pipe (CIPP), which is used to reline rather than excavate and replace underground pipe (see “Editor's Picks,” at right), one of the perceived downsides is the presence of styrene. To address the potential risks associated with styrenated CIPP resins — odor, the potential for emissions and, when cure is facilitated with hot water, safe disposal of styrenated water after cure — several suppliers are offering nonsytrenated alternatives.

Introduced this past November, DSM Composite Resins’ (Schaffhausen, Switzerland) new styrene-free Atlac Premium vinyl ester resin was first used in the Greenliner, produced by international CIPP installer Insituform Technologies Inc. (Chesterfield, Mo.), to rehabilitate 3,280 ft/1.4 km of 12-inch to 18-inch (300-mm to 450-mm) diameter sewer pipe in Heerlen, The Netherlands. According to Edwin Uppelschoten, sales manager at Insituform’s European headquarters in Schaffenhausen, numerous Greenliner installations have occurred since then, with installation time and methodology similar to liners using standard polyester and vinyl ester resins.

A significant portion of business for NoVOC Performance Resins LLC (Sheboygan, Wis.) comes from the sale of its no-styrene resins to the infrastructure rehabilitation market, which encompasses CIPP. Available formulations include the 4900 Series vinyl esters. “We have had an environmental materials focus since developing our first green resin in 1998 as an alternative to solvent-based resins,” says Rich Anders, NoVOC’s corporate technical director. “At that time, green products had much less of a push in this market. Now our resins are selected for environmentally sensitive CIPP situations, where an installation is near a hospital, school, restaurant or other public area, and where fresh waterways are involved.”

NoVOC has its own lining division and has designed premium CIPP liners for small-diameter potable water pipes as well as styrene-free liners for larger-diameter sewer pipes. Anders claims the green resins in both liners enable more efficient installation, with less hot water needed for cure and less energy required, overall, to conduct the installation. “Though our price is 30 to 50 percent higher than styrenated CIPP resins, we have demonstrated a savings in processing time, on the order of 10 to 20 percent.”

Although he believes the price of green CIPP resin “will never be comparable to a standard polyester because of the premium feedstocks we use,” Anders points out that “you can always do better on the formulation. It’s a never-ending effort to go to the next level.”

Balancing green and good outcome

Although he acknowledges growing concern among pipe system owners and engineers regarding styrene in CIPP resins, Kaleel Rahaim, business manager for remediation polymers at Interplastic Corp. (Minneapolis, Minn.) notes that most projects don’t yet specify a green product. He suggests, “The need for green CIPP resins begs the question, What is green? Is green defined as using renewable and/or recycled raw materials? If so, then resins are being developed to answer both scenarios.” In his view, however, CIPP resin producers will be challenged most to formulate resins with better adhesion, corrosion-resistance and high-temperature tolerance.
Emilio Oramas, AOC’s CIPP business manager, agrees, observing that “mistakes made during the installation of CIPP are typically expensive to repair. It is, therefore, critical that CIPP resins are made to the highest standards of quality and consistency.” However, he adds that cost is a critical component and contends that the focus must be “continuous process and quality improvement to maintain those performance levels and also help reduce costs.”

To meet the range of mechanical properties required by municipalities that seek CIPP rehab in their sewer systems, Interplastic offers a dozen different filled and unfilled CoREZYN polyester and vinyl ester resins. Rahaim identifies the most recent formulation as COR78-AT-329LC ValueRez CIPP polyester. This resin provides a lower-cost alternative to more commonly used, filled CIPP resins but reportedly has better mechanical properties. Flexural modulus values for these resins in CIPP applications have reached 600,000 psi/4.1 GPa. Gel time is 6 to 12 minutes at 140°F/60°C with hot-water cure, and the styrene content is 28 to 36 percent.

AOC’s Vipel line includes isophthalic polyesters for this market, such as L704-AAP with high modulus values (600,000 psi/4.1 GPa tensile modulus; 630,000 psi/4.3 GPa flexural modulus); L704-FAH with high molecular weight; and the new L713-LTA, which offers a competitive price without sacrificing performance properties by using the same first-quality materials as all of AOC’s CIPP resins. “CIPP resins are typically highly thixotropic and designed so that viscosity has minimal impact on pumping and processing, yet will resist drain down or flowing up service connections during a CIPP installation and resin cure,” says Oramas. “These resins also require the chemistry for complete cure under difficult cure conditions, such as extremely wet or cold environments.”

“Fillers can increase the flexural modulus of a finished composite liner,” he adds, “and flexural modulus can be a controlling factor when determining the thickness of the liner needed to carry required loads. Higher flexural modulus allows a contractor to install a thinner liner. We have designed our CIPP resins to work with glass- or carbon-fiber reinforcement to provide this higher modulus.”

Vipel L010-PPA is AOC’s bisphenol A epoxy-based vinyl ester for CIPP, formulated for increased corrosion-resistance in higher-temperature and -pressure applications. AOC also offers UV-cure resins and no-styrene CIPP resins, the latter formulated with comparable properties but more environmentally friendly chemistry.

Steve Hardebeck, Reichhold’s technical director, North America, observes, “Resin chemistries are demanding for CIPP in terms of the temperature range they see, from about 65°F/18°C during in-plant application of resin on a liner to in-place cure on site at 180°F/82°C.” For that reason, he says, Reichhold emphasizes the catalyzed stability of its CIPP resins, particularly in two DION-brand formulations, CIPP 2000 and CIPP 3000 (pats. pend.). These resins feature a unique self-thickening reaction — to 1.5 cps over 24 hours — and demonstrate high final viscosity combined with elasticity for ease of tube inversion. Reichhold also offers UV-curable resins for CIPP, and Hardebeck says the company is further evaluating and testing bio-based polyesters for CIPP, but he believes the benefits of green resins will be region- or end-market-specific.

RESIN SYSTEMS UPDATE: ADDENDA

Resins toughen up with nanofillers

Epoxy resins are stiff and strong, but on their own, they sometimes lack the desired impact- and fatigue-resistance. Historically, they’ve been toughened with thermoplastics, but resin suppliers are beginning to turn to a special class of nanomaterials for toughness.

In Geesthacht, Germany, Nanoresins AG produces chemistries for sizing fiber and modifying resin, and has recently formulated Nanopox bisphenol-A epoxy resins with silica nanoparticles. These resins reportedly improve mechanical properties, especially fracture toughness. The spherical silica particles (typically 20 nm), when combined with the right monomers or prepolymers, give Nanopox a significantly lower viscosity yield even with particle loading up to 50 percent. In composites, the silica filler increases toughness and stiffness perpendicular to the fiber direction. Stephan Sprenger, manager of the adhesives and composite materials business unit, says, “Our detailed analysis of nanoparticle volume fraction convinces us that Nanopox can improve fatigue performance tenfold in composites.” Additionally, Nanopox-modified epoxies reportedly do not demonstrate the brittleness that can cause microcracking in finished parts, as can be the case with other rigid, inorganic nanoparticles dispersed through high shear energy.

Sprenger claims that the company’s latest offerings, Nanopox F400 bisphenol-A epoxy and F520 bisphenol-F epoxy, both filled with 40 percent nanosilica particulate, can be used in prepregs, manually mixed resins for hand layup and injection molding with no sacrifice in processability. Nanopox technology is designed to boost not only the performance of epoxy resins but also vinyl ester, acrylic and other chemistries as well. “Since we manufacture nanoparticulate masterbatches of acrylic monomers and epoxy resins by the hundreds of tons per year, at prices ranging from $25 to $50/lb U.S., we have established a robust, industrial-level materials manufacturing process.”

Applications to date for Nanopox F400 nanoresins include machine parts, filament-wound components and automotive and marine products. The F520 Nanopox is being used in vacuum-assisted resin transfer molding (VARTM) processes for special parts, such as those for automotive engines and paper processing machinery.

Nanoresins AG also works with Emerald Performance Materials’ (Cuyahoga Falls, Ohio) CVC Thermoset Specialties Div., which provides Hypro reactive liquid polymers (RLPs) to enhance toughness, low-temperature mechanical properties, adhesion and impact resistance in the nanofilled resin formulations. Emerald’s 2000 series RLPs are direct butadiene homopolymer additives, and its 1300-series carboxyl-terminated butadiene acrylonitrile (CTBN) copolymers are used to modify backbone resin chemistry. “Our materials help functionalize or modify specific, reactive chemical bonds within a resin’s overall formulation,” explains Dave Egan, Emerald’s technical service manager. “In the 1300 series RLPs, carboxyl end groups enable the CTBN to undergo addition-esterification reactions with epoxy resins, becoming elastomeric modifiers to the thermoset resin system.”

The Hypro products form “rubbery domains with bimodal distribution” that can significantly increase interlaminar fracture toughness in composites. This enables the resulting parts, in applications such as jet skis, to withstand rugged end-use. Egan points out that Hypro’s morphology improvement also is effective in polyester and vinyl esters for SMC/BMC compounds as well.

Chemical elements of a resin system

A commercial resin system includes not only the basic backbone chemistry, based on glycol, acid and/or reactive monomers, such as styrene, amines and anhydrides that make it an epoxy, polyester or vinyl ester, but it also incorporates many additives and reagents that can modify or manipulate this chemistry to ensure proper performance in particular applications. In neat thermoset polymer resin systems, any or all of the following may be found.

Cure control additives that affect viscosity and thickening rate, the time between the chemical phases of gelation and exothermic crosslinking and resin hardening. These include catalysts or initiators such as methyl ethyl ketone peroxide (MEKP), accelerators such as naphthenate or dimethyl aniline (DMA) and inhibitors such as tertiary butyl catechol (TCB).
Additives or promoters to achieve optimum resin-to-fiber interface and specific performance properties such as UV stability, conductivity, abrasion resistance, toughness, specific surface characteristics, reduced density and profile, low hydroscopy and flame/fire retardance.
Mold release agents.
Coloration agents and pigments.
Fillers, including calcium carbonate, natural or biobased filler like flax fiber or soy flour, recyclate filler such as rubber particulate and nanosized filler, from nanoclays to carbon nanotubes.

NCC program screening bioresins

A two-year ongoing research effort at the National Composite Center (NCC, Kettering, Ohio) into both nano- and bioresins could help encourage fabricators and end users toward greener SMC formulations that yield lighter weight parts without sacrificing strength and cost savings. A scientific team at the NCC’s Bio-Lite Technical Center of Excellence in Kettering and a new bio-composite laboratory on the Dayton Campus for Advanced Materials Technologies continues screening mechanical properties from a large pool of biomaterials that are submitted from sources worldwide.

According to Harry Couch, senior technical advisor, the ultimate program goal is determining the optimum SMC recipes to achieve 1.2 specific gravity. “We think this is possible, in part through cure stabilization chemistry.” Renewable and recycled resin components are being considered, along with plant and other natural fibers. “We’re also paying attention to surface chemistry, as well as the moisture behavior of natural fibers,” says Couch.

He considers NCC’s joint development programs with material suppliers to be crucial. Resin supplier Ashland Inc. (Dublin, Ohio) and glass fiber reinforcements supplier Owens Corning (Toledo, Ohio) have supported and participated in the NCC’s materials screening efforts. Couch also believes the involvement of SMC fabricators could reduce the development time of biobased composites. “It’s important to clarify that massive recapitalization isn’t necessary in order to process these materials and that commercial biomaterials will compete with traditional materials on a cost per value basis.” In Couch’s opinion, “the current demand for green materials in the marketplace may be inflated,” and he emphasizes that the NCC is striving to “help people gain a realistic perspective on biobased materials.”

Biopolyol boosts reaction time

Is it possible to make the polyol component in polyurethane resin using a greenhouse gas neutral process? According to Dow Polyurethanes (Midland, Mich.), a global business group within The Dow Chemical Co, the answer is yes, with RENUVA Renewable Resource Technology.

Developed over the last decade, this soybean oil-based polyol (or biopolyol) was commercialized in 2007 and uses up to 60 percent fewer fossil fuel resources to produce than conventional polyol technology. Further RENUVA biopolyol utilizes natural oil harvested from soybeans grown in the U.S., which helps reduce reliance on imported raw materials. Though used most recently in flexible foam for furniture and bedding applications, RENUVA bio-based polyol also has been tested with 15 percent wollastonite (or mineral) filler in automotive bumper fascia. In this application, more than 50 percent of the total polyether polyol in the polyurethane resin was replaced by RENUVA biopolyol.

The four-step process in formulating RENUVA bopolyol includes:

Methanolysis, where fatty acid methyesters are produced from the soybean oil.
Hydroformylation, where aldehydes are produced from functionalized double chemical bonds in the soybean oil.
Hydrogenation, where alcohol groups are produced from the aldehydes.
Polymerization, where the monomer is combined with an initiator and catalyst to produce the biopolyol.
The two primary elements in this chemistry are methanol and glycerine, both of which can be sourced from renewable feedstocks.

“Until recently, a key challenge in using natural oil-based polyols in composites has been the reaction time," explains Umberto Torresan, global marketing manger for RENUVA. "Unlike competitive bio-based polyols, which have secondary oxygen/hydrogen or hydroxyl chemical groups in their molecular chains, the RENUVA biopolyols have a primary hydroxyl group that reacts with isocyanates three times faster in the formulation of polyurethane resin. Also, the RENUVA component in the resin offers the benefit of enabling high levels of renewabe content without the unpleasant odor that can be created other bio-based polyols. ”

In the RIM fascia trial, Dow worked with molder, Polycon Industries (Ontario, Canada), designing a polyurethane formulation designated Polycon Lite, which uses RENUVA biopolyol, other additives, and the mineral filler at a 10 to 15 percent load level. Use of this formulation in the five-part painted exterior fascia achieved the surface finish and aesthetics desired by automotive OEMs. Over the course of prototyping these components (upper and lower shelves, side wings, and grille opening reinforcement panel), Polycon varied the degree of RENUVA biopolyol content in the filled resin from 25 to 80 percent. Both companies made the determination that a 50 percent substitution for polyether polyol by RENUVA biopolyol met OEM requirements for Class A surface finished bumper fascia in terms of flexural modulus, tensile strength, density, heat sag, and filler level in four different paint colors.

Torresan confirms that, since initial testing of RENUVA in filled polyurethane fascia components, Dow has pursued several commercial opportunities for this material in automotive fascia, and with further research, could evolve to bio-based exterior body panels. RENUVA polyol also is suitable for use in adhesives and sealants, particularly because the low viscosity formula of biobased polyols reduces the need for solvents, which reduces VOC emissions. Low-temperature flexibility, hydrolytic resistance, and UV stability properties are also exhibited in adhesive applications, including structural formulations.

Read more about this product in “Renuva Soy-Based Polyol RIM for Automotive Exterior Applications,” by M. Goldhawk (Dow Automotive) and A. Zafera, M. Wesolowski, and J. Moore (Polycon Industries), presented in September 2008 at the Society of Plastics Engineers’ (SPE) Automotive Composites Conference & Exhibition (ACCE),http://www.speautomotive.com/SPEA_CD/SPEA2008/c.htm.

Functionalizing green nanobased resins

One of the most extreme environments for nanofilled resins (see “Resins Toughen Up with Nanofillers” in main article) may be in sports products, where damage tolerance such as impact resistance is a critical performance variable. Patented NANO IN technology from Nanoledge (Boucherville, Quebec,Canada) enables the dispersion and integration of nanoparticles in epoxy resins. Unique properties of these nanoparticles, such as multiwalled carbon nanotubes, boost overall mechanical properties in what Nanoledge refers to as “high-performance nanostructured materials.” Successful nanobased resin formulations from the company have been used in surfboard, snow ski, bike frame, fishing rod, golf shaft, badminton racquet and baseball bat applications, as well as in wind energy components.

The key to an optimized nanofilled epoxy comes from a strategic understanding of the molecular chemistry in both the resin and nanoparticles, as well as the possible modifications in the physical properties resulting from these combined elements. This is referred to as nanoformulation. NANO IN technology has its origins in nanoparticles synthesis and functionalization R&D developed at the CNRS (France’s national scientific research center). In 2003, Nanoledge began commercially manufacturing carbon nanotubes, carbon nanotube-filled epoxy resin and eventually nanoparticle-formulated epoxy systems, all billed as “eco-friendly” nanocomposites. The company claims these materials exhibit improved strength, toughness, flexibility, conductivity, chemical resistance, and compression and fatigue resistance properties. In sports products, lighter weight and longer product life have also been demonstrated. Further, there’s an environmental benefit in the materials.

Patrice Lucas, Nanoledge’s customer care director, explains that the use of carbon nanoparticles reduces overall filler content significantly (starting from as low as 0.3 wt-%) in a composite material. This, in turn, reduces the level of chemicals required to manufacture the material. In bio-based epoxies, nanoparticulate reduces chemical levels and utilizes a sustainable component while retaining similar overall properties to conventional filled resins.

Nanoledge also promotes the processibility of its nanobased resins on existing molding equipment because of its optimized functionalization and formulation. Typically, nanofillers may increase viscosity (higher viscosity means the material flows more slowly), which can affect overall processing time. “We believe the formulator’s mission is to design nanobase formulas that fit the manufacturer’s process and desired end product performance, rather than the manufacturer having to design a process in order to produce high-quality parts with our nanomaterials,” Lucas says.

To formulate its nanobased materials, Nanoledge works with various nanoparticles suppliers, such as Bayer MaterialScience (Leverkusen, Germany and Pittsburgh, Pa.), whose trademarked Baytubes product is considered by Nanoledge to be of high quality and highly reliable. Currently, Nanoledge offers four nanofilled epoxy masterbatches for sports products, another four for wind energy structures, and five for aerospace components, all of them designed for formulators. These can be tailored for particular customers or purchased in ready-to-use formulations for prepreggers and composites parts manufacturers. Intermediates (e.g., semi-solid resin films) are available for other processes, such as resin film Infusion (RFI).

Lucas reports that the company has an annual production capacity of 100 tons for nanobased resins and more for ready-to-use formulations. He notes that the company will soon launch a new eco-friendly nanofilled formulation designed for surfboard applications, developed in close partnership with Ecomoana (Chamrousse, France).

To read more about nano-enhanced composites, click on “Nanoparticles, Nanotubes and Nanocomposites,” under “Editor’s Picks,” in “Learn More” at the top of this page.