Specific-Gravity Thermoplastics Open New Doors

Thermoplastics and high density materials continue another year of growth as recent developments and innovative design changes allow these materials to offer even more benefits in all kinds of environments and applications. Thermoplastics found a place in mainstream business due to their ability to decrease the part count or weight of parts in a particular tool or appliance. Turns out that a new class of heavy plastics and high density compounds are entering the picture, ones that have a specific gravity varying between 1.8 to 10.

A Bit of History

To better understand how this could revolutionize the manufacturing process, let’s take a look at how engineered thermoplastics are made. After a base resin has been chosen, its electrical, mechanical and physical properties are altered and manipulated to achieve desired state. Fillers and replacements such as rubber tougheners (for flexibility), carbon-black fillers (for electrical conductivity) and glass fiber (for strength) are carefully chosen and added to finally create a material that can work wonders in making the manufacturing process faster, smoother and cheaper.

How are High-Specific-Gravity Compounds Created?

High-specific-gravity compounds are created by combining adding mineral or metallic fillers in thermoplastics. Base resins commonly used in this care are crystalline thermoplastics because of their flow properties. Common examples include polyesters, polypropylene, polyurethane and polyamides. Surface chemistry of fillers and particle size distribution is also important to ensure optimal processability. 

The Journey from Light to Heavy

High-specific-gravity compounds can be classified into three different weight classes. Lightweight high-specific-gravity compounds have a specific gravity which varies between 1.8 to 4. These heavy plastics are commonly used in medical devices and to replace aluminium, clay or glass. Some of these compounds are used to add strength while others may be used to improve toughness. These compounds can be pigmented from brighter to darker tones.

Middleweight high-specific-gravity compounds have a specific gravity that varies between 4 to 7. These materials are usually designed to become magnetic and they fall in the same class as die-cast zinc. Many safety-restraint components used in automobiles are made using these high density materials and these parts can be colored in darker hues.

Finally, heavyweight high-specific-gravity compounds have a specific gravity that varies between 7 and 10. They offer solutions similar to lead, stainless steel and bronze and are a fantastic lead replacement for shielding x-rays in medical applications. Training rounds are also made using these compounds to minimize the use of lead while allowing the material to withstand muzzle pressure and still manage to disintegrate upon impact. Another application of heavyweight high-specific-gravity compounds can be seen in automobile steering columns.

Why is this Important?

What makes these high gravity compounds so special is that they not only manage to consolidate parts and custom-create properties in order to decrease costs, but also present the ability to dialin specific part weights across the density range, which even manages to touch lead and its alloys. To make matters even more interesting, these engineered thermoplastics also come with special abilities such as magnetic properties, noise reduction, frangibility, x-ray opacity and x-ray shielding. High-specific-gravity compounds are injection moldable in metal replacement solutions, which also eliminates the need for assembly operations and secondary machining, further reducing costs across the manufacturing channel.

Steven J. Stanek usually writes articles and blogs related to industrial Mechanism and Products, In this article he writes about High density plastic and thermoplastic composite materials. He has been vehemently writing articles for ecomass.com