Properties of Pyrograf-III Carbon Nanofibers

Table of Contents

Types of Carbon Nano Fiber
About Pyrograf


Pyrograf-III is a highly graphitic, inexpensive, very fine, patented and tubular carbon nanofiber. Two fiber types are available that includes diameters in the 70 - 200 nm range and a as-produced fiber length in the range 50-200 µm. Hence nanofibers have a smaller size when compared to traditional milled or continuous carbon fibers but definitely larger than carbon nanotubes (1-10 nm). Pyrograf-III nanofiber is presently offered in two types and in the three grades shown below. The nanofiber is also available in several product forms; powder-like (i.e. debulked), paper, pre-dispersed, and compounded product forms.

Types of Carbon Nano Fiber

The table shows the summary of the properties of carbon-III nanofiber:

Table 1. Summary Table of typical inherent properties of Pyrograf-III carbon nanofiber

Nano- fiber Type Nano- fiber Grade N2Surface Area, (m2/gm) Dispersive Surface Energy, (mJ/m2) Moisture Content (%) Iron Content (ppm) PAH Content (mg PAH/g fiber)
PR-19 XT-PS 20-30 120-140 < 5 < 14,000 <1
PR-19 XT-LHT 15-20 120-140 < 5 < 14,000 <1
PR-19 XT-HHT 15-25 265-285 < 5 < 100 <1
PR-24 XT-PS 40–50 75-95 < 5 < 14,000 <1
PR-24 XT-LHT 35–45 145-165 < 5 < 14,000 <1
PR-24 XT-HHT 35-45 125-145 < 5 < 100 <1

The different types of carbon nanofiber are:

PS - Pyrolytically stripped carbon nanofiber enables removal of polyaromatic hydrocarbons from the fiber surface.

LHT – This includes carbon nanofiber heat-treated to 1500°C temperatures, which carbonizes chemically vapor deposited carbon present on the Pyrograf surface. Nanofibers are produced by this heat treatment, which normally provides the highest electrical conductivity in nanocomposites.

HHT – This includes carbon nanofiber heat-treated to temperatures up to 3000°C, which graphitizes chemically vapor deposited carbon present on the surface of Pyrograf. This high level of heat treatment results in highly graphitic carbon nanofiber and minimizes the iron catalyst content to very low levels.

PR-19 – This has an average diameter of about 150 nm and has a chemically vapor deposited (CVD) layer of carbon on the fiber surface over a graphitic tubular core fiber (catalytic layer) as observed in Figure 1.

Figure 1. Transmission electron micrograph showing catalytic

PR-24 – This has an average diameter of about 100 nm and has a minimal CVD carbon overcoat. Since the fibers are produced in a vapor phase, they get entangled during growth, resulting in a mesh-like configuration. De-bulking of this raw form is then done resulting in a product that is uniform in bulk density enabling precise compounding into final products.

Pyrograf-III is presently available in a debulked form termed as XT. This form has a bulk density of 1-3 lb/ft3.

Figure 2 and 3 show micrographs representing magnified views of the Pyrograf-III carbon nanofiber in its final debulked product form.

Figure 2. Prior Debulking Process (difficult to disperse)

Figure 3. XT Debulking Process (easier to disperse material)

Closely-knit bundles of nanofiber are seen in the top image, which are typical of the debulked product that has been produced for a number of years.

It is tough to disperse this type without causing any damage to the nanofiber. The product form processed with an improved debulking method (designated as XT in the product code) that creates loose structures of the carbon nanofiber bundle is shown in the lower image. The loose “XT” carbon nanofiber bundle needs a lesser amount of energy to achieve dispersion, hence enabling higher retention of fiber length during processing. The new product generates the same electrical conductivity in polymer composites at approximately half the loading of the non-XT nanofiber.

It is possible for Pyrograf-III to simultaneously provide improved electrical conductivity over a broad range along with mechanical reinforcement of certain matrix materials. Other benefits provided by the nanofiber include improved heat distortion temperatures and increased electromagnetic shielding.

About Pyrograf

Pyrograf Products, Inc. (PPI) is one of the leading producers of carbon nanofibers worldwide.

Pyrograf Products focuses on manufacturing high- quality, low-cost carbon nanofibers utilizing the proprietary and patented vapor grown carbon fiber (VGCF) process. Pyrograf-III, developed Applied Sciences, Inc. (ASI), is a versatile vapor grown carbon nanofiber with a wide range of applications.

This information has been sourced, reviewed and adapted from materials provided by Pyrograf.

For more information on this source, please visit Pyrograf.

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