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HDT - Heat Deflection Temperature

Oran Hazan - PVC Field Technologist, Lab

Heat Deflection Temperature (HDT) is the temperature at which a polymer or plastic sample deforms under a specified load.

This property of a given plastic material is applied in many aspects of product design, engineering, and manufacture of products using

thermoplastic components.

The heat distortion temperature is determined by the following test procedure outlined in ASTM D648.

The test deflection is loaded in three-point bending in the edgewise direction.

This is similar to the test procedure defined in the ISO 75 standard (Source: Wikipedia).

For the purposes of manufacturing, marketing and selling polycarbonate and PVC Sheets, we must consider HDT as an important

factor when we provide potential customers with solutions and products. The following bullets represent the various factors and

considerations relating to HDT.



HDT by definition refers to the overall bulk of the sheet. As such, thicker sheets will have a higher Heat Deflection Temperature,

reflected in a greater service temperature range.



PVC & PC sheet bulk temperatures are the combined result of the ambient temperature and direct exposure to infra-red radiation

that may be associated with sunlight (Direct sunlight in itself, doesn’t necessarily indicates heat radiation, i.e. IR radiation).



Dark colors (similarly to black body) absorb more heat and at a faster rate.



Cold colors for PVC, which are embedded within the bulk material itself, are essentially IR diffusers / reflectors.



These cold colors allow PVC roofing, cladding and decks to maintain a relatively low surface temperature and extend their effective

service temperature range.



Palram’s white PVC roofing (white PALRUF) has improved HDT properties due to its white

color and special formulation.



Multi wall sheets and panels allow for even greater HDT and service ranges due to their

internal insulating function.



Palram’s solar colors are the cold colors for polycarbonate. They effectively reduce IR transmission

through them and provide a cooler yet fully lighted environment.



Surrounding temperature and direct sunlight influence on the sheet’s temperature (bulk and

surface) and therefore it is essential to characterize the material and the product specification.

Palram’s unique USP (Unique Selling Proposition) in regards to HDT and essentially all engineering

& technical related aspects of utilizing PVC & PC sheets is its in house Projects Support Team. They

provide each customer with custom solutions to fully integrate our products with the customer’s

requirements and we provide support for both the product and the installation process.

Introducing the PalramProjectsWebsite

| Tamir Horesh

Palram’s Projects Department is launching a new website to showcase some of

our best architectural projects, built using Palram’s

polycarbonate, PVC and acrylic solutions. The website presents a photo gallery, arranged by project category and application, which

will inspire designers to incorporate Palramproducts into their architectural creations. In addition, the website

includes a resources section, where the building professional can find

useful tools such as load calculators, CAD drawings and

specification documents for Palram’s products, making it

easier for him or her to add Palram in the structure.

Through the new website and its Project Support Center,

Palram is deepening its engagement with architects,

engineers, contractors and other professionals in the

construction industry. By raising the awareness to Palram’s

products for construction applications, we will bring more

business to Palram and to its customers.     

Please visit our website at

For any support with architectural projects, contact us at