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ISO-HT® Polyiso Datasheet


ISO-HT Data Sheet

ISO-HT Polyisocyanurate Insulation for higher temperature applications
Version : 0615 

ISO-HT®   Polyisocyanurate Insulation
2.5 lb/ft³ (40 kg/m³) density for Higher Temperature Applications

ISO-HT is Dyplast Products’ 2.5 lb/ft³ polyisocyanurate rigid, closed cell, foam insulation for higher temperature applications up to 350°F (177°C), with intermittent exposure up to 375°F (190°C). ISO-HT is suitable for constant temperature or heat cycling environments. ISO-HT is certified by independent laboratory to meet demanding Class 1 flame spread and smoke development requirements per ASTM E84. ISO-HT fully complies with the demanding requirements of ASTM C591-15. Dyplast offers ISO-HT as bunstock or as sheets and blocks, with tolerances up to 1/32 inch on surfaces. Our extensive network of fabricators can provide special shapes for pipe, fittings, vessels, or other mechanical applications.

Polyisocyanurate exhibits the highest R-factor (insulating value) to thickness ratio of commercially available insulation, and ISO-HT provides higher R-factors and reduced thermal aging at lower temperatures. Ideal for applications over a wide range of temperature, from cryogenic liquids to low-temperature steam, ISO-HT offers superior performance when compared to polystyrene, polyurethane, phenolic,fiberglass, and cellular glass alternatives. When temperatures are limited to less than 300°F, our ISO-C1 product line is also available in 2, 2.5, 3, 4, and 6 lb/ft³ densities, which each provide successively improved strength and other attributes for physically demanding applications.

Dyplast’s ISO product line is produced as a continuous foam bunstock. For specific standard stock bun sizes contact the sales department.


ISO-HT is designed for use where temperatures range from -297°F to +350°F, making it ideal for low-temperature steam applications and refinery liquids, as well as commercial refrigeration, HVAC, chilled water, and hot water systems, panel insulation for transportation containers, and core material for architectural and panel construction.


Water absorption by insulation can degrade thermal insulating performance. ISO-HT’s extraordinary resistance to water absorption (0.6%) helps ensure long-term thermal performance remains superior to polystyrenes, phenolic foams, fiberglass, and even cellular glass - - which for example has water absorption of 0.2% (per manufacturer data), as well as considerably lower insulating value. Proper installation of vapor barriers can further improve performance of the complete ISO-HT insulating system.


Visit www.dyplast.com for easily accessible information on specifications in CSI format as well as MSDS, and other safety information. Relevant documents are retrievable within two clicks from our home page.

Dyplast Products is the preeminent manufacturer of polyisocyanurate and expanded polystyrene rigid foam products. With world-class production facilities in Miami, Florida, Dyplast Products offers its customers unsurpassed technology, responsiveness, wide-ranging product configurations, and state-of-the-art quality control. Our customer-focused staff, combined with our sound financial footing, ensure we deliver incomparable value to our customers far into the future. For information on Dyplast Products or additional technical data on this product, visit our website at www.dyplast.com.


The International Mechanical Code defines Class 1 insulation as meeting the 25/450 flame spread/smoke development rating. ISO-HT performs well within this range with a 25/400 (at 4”) rating. When comparing surface burning characteristics of alternative products, care must be taken to consider the installed insulation system as a whole, including sprinkler systems. For example, a well-designed ISO-HT insulation system can improve overall flame/smoke performance of the polyiso insulation. On the other hand, an alternative insulation’s flame/smoke ratings may be compromised by the sealants or jacketing often recommended by suppliers. There is also the matter of insulation system integrity during a fire. ISO-HT may be charred by flame, but maintains its integrity and continues to protect the insulated system.


High thermal insulation effciency is achieved by infusing cells with gases having low thermal conductivity. All such rigid foam insulation (including polyurethane, extruded polystyrene, and polyisocyanurate) thus lose a small amount of their insulating value over time as air displaces insulating gases. ISO-HT’s smaller, stronger cell structure and our proprietary cell-gas formulation work together to impede gas transfer across cell boundaries, thus reducing loss of thermal effciency. At a testpoint of 75°F, the average R-factor of ISO-HT over a 15 year period is comparable to the six-month “aged” R-factor. Thicker insulation, vapor barriers, and metal constraints also limit gas diffusion. Current LTTR calculation standards are primarily applicable to “faced” polyiso board, and are not appropriate for ISO-HT bunstock.


 ISO-HT is designed for constant temperature exposure up to 350°F. ISO-HT should be installed on pipe at room temperature and installation onto high temperature or live steam lines is discouraged, since this will cause dimensional stability problems. ISO-HT should be used with an appropriate ASJ or Vapor Barrier held in place with SSL tape. The use of ¾ inch filament tape with a 25% overlap is recommended, as is a PVC or Metal Jacket secured with metal banding.

 Table 1 ISO-HT® Foam Comparison vs. ASTM C591-15

General Physical Properties1,2,3 ISO-HT® /2.5 ASTM C591-15 Max or Min
Service Temperature, °F (°C)                                            (Maximum4) 300 (149) 300 (149)
(Minimum) -297 (-183) -297 (-183)
12.17 Nominal Density, D1622, lb/ft3 (kg/m3) 2.5 (40) ≥2.5 (40)
12.2 Compressive Resistance (Strength), D1621 psi (kPa)    
Parallel 39 (266) ≥35 (241)
Perpendicular (Length) 33 (230)  
Perpendicular (Width) 30 (207)  
12.3 Apparent Thermal Conductivity, C1778
(aged 6 months @ 73 ± 4°F) Btu.in/hr.ft2°F (W/m.°K)
Mean temp of measure -265°F (-165°C) 0.06 (0.009) Not specified
Mean temp of measure -200°F (-129°C) 0.11 (0.016) ≤0.13 (0.019)
Mean temp of measure -150°F (-101°C) 0.13 (0.019) ≤0.15 (0.022)
Mean temp of measure -100°F (-73°C) 0.15 (0.022) ≤0.17 (0.025)
Mean temp of measure -50°F (-45°C) 0.18 (0.026) ≤0.19 (0.027)
Mean temp of measure -0°F (-17°C) 0.18 (0.026) ≤0.19 (0.027)
Mean temp of measure +50°F (+10°C) 0.16 (0.023) ≤0.19 (0.027)
Mean temp of measure +75°F (+24°C) 0.16 (0.023) ≤0.20 (0.029)
Mean temp of measure +150°F (+66°C) 0.19 (0.027) ≤0.24 (0.035)
Mean temp of measure +200°F (+93°C) 0.20 (0.029) ≤0.27 (0.039)
12.4 Hot-Surface Performance, C411 at
300°F (149°C) Deflection inches (mm)
Pass @ 0.03 (.7) ≤0.25 (6)
12.5 Water Absorption, C272, % by volume 0.6 ≤1.0
12.6 Water Vapor Permability (Transmission), E96, Perm-in (ng/Pa.s.m) 1.9 (2.8)  ≤3.5 (5.1)
12.7 Dimensional Stability5, D2126, % linear change    
-40°F, 14 days -0.2 ≤1
158°F, 97% RH, 14 days 1.2 ≤4
212°F, 14 days 0.6 ≤2
12.8 Closed Cell Content, D6226, % 95 ≥90


Table 2

The following properties are NOT Specified for ASTM C591-15 yet are often reported. 
Surface Burning Characteristics6 (if required), E84  
Flame Spread (@4 inch thickness) ≤25
Smoke Density (@4 inch thickness) 350
Leachable Chloride, C871, ppm 58
Shear Strength, C273,  Average of 3 directions in psi (kPa) 24 (165)
Shear Modulus, C273, psi (kPa) 289 (1993)
Tensile Strength, D1623, psi (kPa)  
Parallel 49 (338)
Perpendicular 35 (241)
Tensile Modulus, D1623, psi (kPa)  
Parallel 1741 (12004)
Perpendicular 1167 (8046)
Flexural Strength, C203, psi (kPa)  
Parallel 58 (400)
Perpendicular 60 (414)
Flexural Modulus, C203, psi (kPa)  
Parallel 870 (5998)
Perpendicular 1018 (7019)
Coefficient of Linear Expansion, E228, Average Value in/in.°F (m/m.°C) 34 x 10-6 (61 x 10-6)
Color Tan


MAIN TABLE Footnotes:
1. All properties were measured at temperatures at or near 75° unless otherwise indicated, and all test values were obtained from
independent certified testing laboratories.
2. These are nominal values obtained from representative product samples, and are subject to normal manufacturing variances.
3. Average value through the foam cross section of tested sample.
4. Above 300°F, discoloration and charring will occur, resulting in an increased k-factor in the discolored area.
5. Frequent and severe thermal cycling can produce dimensional changes significantly greater than those listed here. Special design
considerations must be made in systems subject to severe cycling.
6. This numerical flame spread data is not intended to reflect hazards presented by this or any other material under actual fire
7. Table 1 includes the paragraph numbering system utilized within Section 12 of ASTM C591-15.
8. Thermal Conductivities (k-factors) at Low Temperatures: ASTM C591 is the Standard Specification for Unfaced Preformed Rigid Cellular Polyisocyanurate Thermal, and is arguably the key Standard used by insulation system end-users and engineer/specifiers to guide decision-making. Compliance with ASTM C591 is often a prerequisite within an insulation Request for Proposal. The latest version of the Standard, ASTM C591-15, imposes some additional requirements such as revised limits on thermal conductivities (k-factors) measured across a temperature range from +200°F to -200°F. Dyplast has traditionally offered this information to its clients; our k-factor results are comlpliant and excellent.



NOTICE: No freedom from any patent owned by Dyplast Products or others is to be inferred. Because use conditions and applicable laws may differ from one location to another and may change with time, Customer is responsible for determining whether products and the information in this document are appropriate for Customer's use and for ensuring that Customer's workplace and disposal practices are in compliance with applicable laws and other government enactments. Dyplast Products assumes no obligation or liability for the information in this document. NO WARRANTIES ARE GIVEN; ALL IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE ARE EXPRESSLY EXCLUDED.

Characteristics, properties, performance of materials, and application specifications herein described are based on data obtained under controlled conditions. Information is supplied upon the condition that the persons receiving same will make their own determination as to its suitability for their purposes prior to use. Dyplast Products makes no implied warranties of any type, including without limitation, any warrant of merchantability or fitness of purpose. In no event will Dyplast Products be responsible for damages of any nature whatsoever resulting from the use of or reliance upon this information or the product to which information refers. No agent, sales representative, or employee is empowered to change, alter, or amend this provision, unless approved in writing by a duly authorized officer of Dyplast Products.


About Dyplast

Dyplast Products offers mechanical insulation solutions for an array of low temperature applications such as LNG insulation, cryogenic insulation, chilled water pipe insulation, refrigeration insulation, and low temperature steam insulation - - and in industries ranging from building construction,, roofing, refrigeration, transportation, petrochemical, pharmaceutical, marine and more.