SAMPE Journal - May/June 2023 - 37

INTRODUCTION
Techneglas LLC recently developed a polysiloxane
resin family designed for high service temperatures,
up to 1200°C. Ultra-High Temperature Resins
(UHTR) are available as solid flake (Table 1), as a
solution in isopropyl alcohol (Table 2), and as high
viscosity liquids (Tables 3 and 4).
UHTR resins are a patented, inorganic
polysiloxane, pre-ceramic matrix formulated for
low weight loss, high char yield, low heat release
rate, and low heat release capacity for composite
applications. UHTR composites can be made
using glass fiber, silica/quartz fiber, carbon fiber,
and basalt fiber. UHTR resin is used in automotive
coatings for engine and exhaust components
and is currently being evaluated for composite
applications for automotive, aviation, aerospace,
and military applications. UHTR resin can be
used for wet layup, tow winding, BMC / SMC, and
prepregs. UHTR resins are thermosets that can be
thermally cured at 225°C for 2-3 hrs. followed by
post-cure as needed.
UHTR resins can be catalyzed for lower
temperature cure, or faster cure at elevated
temperature. Catalyst examples include:
* Titanium (IV) Butoxide
2-3 wt%
* N-(2-Aminoethyl)-3aminopropyltrimethoxysilane
1-2 wt%
* 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole
0.5-2 wt%
UHTR is
resins
formulated for easy processing,
comparable to epoxy resins, while exhibiting
sustained operating temperatures near, or above,
legacy
designed
applications, Figure 1.
BACKGROUND
Thermal protection system (TPS) is an important
component of a reentry spacecraft. On many
occasions, high-temperature ablative material,
placed as the most outside layer of the TPS1
, is
required to protect the components or structures
of the functional parts, such as the space vehicle
during the reentry stage or solid rocket motor
nozzle. Most ablative materials are reinforced
organic resin composites2
due to their low densities
and good ablation properties. For example, the
Apollo command modules (CM) were used a
low-density material, Avcoat 5026-39/HC-G, as
their heat shield started in late 1960s. Avcoat
5026-39/HC-G is an epoxy-novolac resin filled
fiberglass honeycomb material3
of 0.51 g/cm3
, a char density of about half of its
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SAMPE JOURNAL |
37
V.O.C.
Specific Gravity
Appearance
Viscosity
Percent of Solids
Odor (liquid)
for
high-temperature
Table 1. UHTR-F specifications.
UHTR-F
Appearance
Melting Point
Resin Content
Odor
Tg
Density
White solid
100°C
>99%
Slight
>500°C
1.2 g/mL (10.0 lb/gal)
Liquid Ignition Temperature >300°C
Table 2. UHTR-IPA specifications.
UHTR-IPA
Appearance
Viscosity
Percent of Solids
Odor (liquid)
V.O.C.
Specific Gravity
Slightly cloudy liquid
95 cPs
65%
Slight Solvent
368 g/L (3.07 lb/gal)
1.05
Pot Life at 25°C when catalyzed 1-3 hours
Table 3. UHTR 6398-S specifications
UHTR 6398-S
Appearance
Viscosity
Percent of Solids
Odor (liquid)
V.O.C.
Specific Gravity
Colorless/white semi-solid
35,000 cPs (75°C)
>99%
Slight
Zero
1.2 g/mL (10.0 lb/gal)
Pot Life at 25°C when catalyzed >300°C
Table 4. UHTR 9863-S specifications
Techneglas UHTR 9863-S
Colorless/white semi-solid
5,000 cPs (50°C)
>99%
Slight
Zero
1.2 g/mL (10.0 lb/gal)
Pot Life at 25°C when catalyzed >300°C
, with a density
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SAMPE Journal - May/June 2023

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