SP Nano Ltd. (Yavne, Israel) reports that it has developed SP1, a thermally stable protein originally isolated and cloned from poplar trees, and now produced by means of fermentation. Its genetically engineered variants tightly bind to carbon nanotubes (CNTs) to form what is described as a stable SP1/CNT complex, which prevents CNT aggregation/agglomeration and allows its homogenous mixing in a resin matrix. SP Nano has demonstrated that SP1/CNT, when combined with an epoxy-based adhesive at <1%-wt improved peel strength, impact resistance and fraction toughness by more than 50%. Even bigger improvement in fraction toughness was observed when SP1/CNT was combined with epoxy-based resin.
Further, SP Nano has demonstrated that SP1/CNT can be applied as a sizing-like coating to dry carbon fiber at loadings of 0.3-0.4%-wt. SP Nano tested this material, wet-laid and autoclave-cured, using a phenolic resin, and compared the results to the same test of a carbon fiber/phenolic without SP1/CNT coating. Results show an interlaminar shear strength of the SP1/CNT composite 47% greater than that of the non-SP1/CNT composite; through-thickness tensile strength tests demonstrated a 176% increase in the SP1/CNT composite. SP Nano says the property improvements can be attributed to the presence of the CNTs on the surface of the carbon fiber, which creates a high surface area network that bridges the fiber and the resin matrix.
Eyal Shpilberg, CEO of SP Nano, says the company is evaluating applications for SP1 and early analysis shows the SP1/CNT-phenolic combination might have the most potential. In addition, the company is working on an epoxy-compatible SP1/CNT formulation as well. Another application, he notes, is with glass fiber coating, where a 2%-wt concentration creates high conductivity. This, Shpilberg says, could be valuable to provide EMI shielding in electronics applications. SP1/CNT also has application in adhesives at loadings of about 1.2%-wt. SP Nano also reports that it is working with some OEMs to further evaluate interlaminar properties of SP1/CNT composite structures.
Shpilberg says SP Nano is currently selling concentrated bottles of the SP1 protein with CNTs. The customer then would bear responsibility to integrate the material into their materials. Shpilberg notes that the coating technology used to apply SP1/CNT to a dry fiber is “standard and widely available globally.”