All Categories > Industrial Products > Engineering Composite Materials > Fiberglass Reinforced Polyester (FRP) > Glastherm-HT and Glastherm-S (Up to 550ºF Fiberglass Reinforced Polyester Composite Boards) > Item # Grade S  
    Printable Page     Email Email This Page     Save To Favorites Save To Favorites

Item # Grade S, Glastherm-HT and Glastherm-S (Up to 550ºF Fiberglass Reinforced Polyester Composite Boards)

GLASTHERM® brand thermal insulating sheet is an excellent choice for mold insulation applications. Glastherm sheet offers significant advantages when compared with other materials such as mica, asbestos concrete or calcium silicate. Glastherm sheet is an efficient thermal barrier. It is strong in order to resist the effects of molding pressure and rough handling. It is resistant to oil and water absorption, and is completely asbestos-free.
A major profit constraint in the molding and casting of rubber, plastics and metals continues to be the cost of energy. Managers who are concerned with the current and forecasted price of electricity, natural gas, and oil are focusing on methods which will reduce energy consumption. Installing or upgrading thermal insulation in curing presses and molds is one relatively easy and inexpensive way to achieve important energy savings.
In order to cure or "freeze" a resin or compound, molding equipment is almost always dependent upon heated or cooled zones Glastherm sheet reduces energy consumption by minimizing a wasteful flow of energy between these zones.
In the past, little or no insulation has been used in or around molds. Where it was used, the insulation was often a thin sheet of asbestos-reinforced concrete (e.g. Transited®). Although inexpensive, asbestos-reinforced concrete is a poor thermal barrier and is so brittle that it is easily damaged. It readily absorbs oil and water, further reducing its value as an insulating material. Asbestos concrete also tends to compress after a period of time in use. This can be a problem where parallelism between mold halves is important. Alternatives to asbestos concrete, such as calcium silicate (e.g. Marinite®) and mica, also have drawbacks. Calcium silicate is highly absorbent and has very poor compressive strength. Mica has poor long-term compressive strength and is expensive. Insulating material for today's needs must have:
  • Low thermal conductivity
  • High compressive strength at process temperatures
  • Excellent control of thickness dimension
  • No asbestos or other toxic materials
  • Ability to withstand rough handling during mold changes
Glastherm sheet provides all of these features. It is a fiberglass reinforced, mineral filled sheet bonded together with heat resistant thermosetting resins. This highly durable composite is then precision finished to close dimensional tolerances. It has less than half the thermal conductivity of asbestos concrete and is rugged enough to provide years of service.
When installed on the base of a mold. Glastherm sheet will reduce heat transfer between mold and press platen. This also results in more even temperatures within the mold. Another benefit, in the case of heated molds, is that less plant ventilation will be needed.

Specifications  · Note  · Grades of Glastherm Sheet


Maximum Service Temperature

425 ºF

Thermal Conductivity

1.8 BTU-in/hr-ft²-ºF

Coefficient of Thermal Conductivity Across Thickness

7.02 x 10-5 in/in/ºF

Coefficient of Thermal Conductivity Across Surface

1.10 x 10-5 in/in/ºF

Specific Heat

0.24 btu/lb

Compressive Strength Force Applied to Surface at 75ºF

45000 psi

Compressive Strength Force Applied to Surface at 302ºF

16000 psi

Compressive Strength Force Applied to Surface at 392ºF

11500 psi

Compressive Strength Force Applied to Surface at 425ºF

10000 psi

Compressive Modulus

1.8 x 106 psi

Flexural Strength

18000 psi

IZOD Impact Strength

8.0 ft lb/in

Rockwell M Hardness


Water Absorption

0.4 % by Wt.


115 lb/ft³

Thickness Tolerance

±0.002 in



Electric Strength Perpendicular at 0.5 in

50 vpm

Resistance to Lubricant and Hydraulic Fluids

No Effect

Glastherm Sheet Thickness

1 in

Glastherm Sheet Size

3 x 6 ft
4 x 8

Glastherm sheet is manufactured in thicknesses from 1/4 inch to 1 inch, and in sheet sizes of 3 ft x 6 ft and 4 ft x 8 ft. Contact your nearest Distributor for exact size availability by grade.

Grades of Glastherm Sheet
Two grades of Glastherm insulating sheet are currently available. Both otter a combination of high physical strength and low thermal conductivity.
Glastherm Grace S Sheet
A general purpose insulating sheet with an economical combination of thermal and physical properties Recommended for processes where the continuous operating temperature does not exceed 425ºF Grade S is particularly suited to the rubber molding industry.

twitterfacebookFlickrLinked InSite created by ThomasNet Web Solutions and powered by Navigator Platform
Foundry Service & Supplies, Inc. | Heat And Corrosion Resistant Industrial Insulation & Construction Materials