Why thermoplastics are so unique

Thermoplastics are the most important class of plastics in industry. They combine reversible moldability, cost-efficient processing, and recyclability with a wide range of properties. Depending on their structure—linear or slightly branched, amorphous or semi-crystalline—key thermoplastic properties such as melting point, strength, toughness, and transparency vary. Their applications range from standard products to highly specialized high-performance components.

What makes them special is that thermoplastics can be molded as often as desired when heated and solidify again when cooled—without undergoing any chemical changes. This clearly distinguishes them from thermosets, which harden irreversibly, and elastomers, which are elastic but cannot be melted.

Thermoplastic elastomers (TPE, TPU) occupy a special position: they combine the meltability of thermoplastics with the elasticity of classic elastomers and open up additional possibilities for flexible applications.

The use of mineral fillers from HPF The Mineral Engineers allows the properties of thermoplastics to be specifically enhanced—for example, in terms of stiffness, dimensional stability, thermal conductivity, or flame retardancy. This results in tailor-made materials for demanding industrial applications.

The structure of thermoplastics is based on long polymer chains that are either linear or slightly branched. Unlike thermosets, they do not have permanent cross-links, which makes them reversibly deformable. Depending on the arrangement of the chains, a distinction is made between amorphous thermoplastics, in which the molecular chains are disordered and often transparent, and semi-crystalline thermoplastics, which contain ordered areas (e.g., PE, PA). This crystallinity provides higher strength, stiffness, and chemical resistance, but reduces transparency.

Features at a glance:

• reversible formability, meltable, multiple formability
• thermal resistance: standard types up to approx. 100°C, high-performance thermoplastics up to over 250°C
• mechanical: from flexible (PE, PP) to high-strength (PA, PEEK)
• chemical: resistant to many acids, alkalis, and solvents
• transparency and strength vary depending on the structure of the thermoplastics
• additives and HPF fillers improve the mechanical properties

HPF focuses primarily on polyamide, polypropylene, and polyethylene, as our fillers are particularly effective at optimizing these polymers.

Thermoplastics are produced by polymerization, polycondensation, or polyaddition. Depending on the process, linear or branched polymer chains are formed, which can be amorphous or semi-crystalline. This structure of thermoplastics determines key thermoplastic properties such as melting point, transparency, or strength.

During processing, both the condition of the material and precisely adjusted machine parameters are important. Granules (compounds) or powder must be clean, homogeneous, and, in the case of hygroscopic types such as PA or PET, carefully dried to ensure consistent melting and flow properties. The structure requires precise temperature and pressure control: too low temperatures prevent complete melting, too high temperatures lead to material degradation. The cooling rate also influences the degree of crystallization and thus properties such as strength, toughness, and transparency. The dwell time in the cylinder should also be kept short to avoid thermal damage.

Important processing methods

• injection molding – complex molded parts in large quantities
• extrusion – films, pipes, profiles
• thermoforming/compression molding – packaging, blister packs
• blow molding – hollow bodies such as bottles, tanks
• 3D printing (FDM) – prototyping, small series

In addition to the right formula and mixture, the decisive factors are primarily melting temperature, viscosity, cooling rate, and material moisture.

The use of mineral fillers can positively influence the mechanical properties of thermoplastics due to their different specific characteristics such as morphology, hardness, or surface texture, thus offering an interesting range of new possibilities. Thermoplastics can be specifically modified to achieve higher stiffness and thermal conductivity, improved chemical and/or UV resistance, and increased flame retardancy.

If you would like to know more about the use of our fillers in your manufacturing process, please write to us! We will be happy to help.

Thermoplastics are particularly sustainable due to their recyclability—they can be melted down and reshaped multiple times. Single-type materials enable efficient mechanical recycling. Thermoplastics play a crucial role in the circular economy and meet today's political and regulatory requirements.

Contaminated post-consumer or post-industrial plastic waste poses a major challenge for the circular economy, as the quality level required by industry often cannot be achieved. The odor profile of the recycled materials in particular is often a source of dissatisfaction. The unpleasant odors that can arise from the contaminants or during the recycling process are problematic when considering their use in automotive interiors, for example.

HPF The Mineral Engineers offers special additives for odor optimization. The mineral-based odor absorbers from the RESCOFIL^® product range were mixed into a post-consumer polypropylene recyclate at a concentration of 5% by weight in a twin-screw extruder. The resulting product was subjected to an olfactometric test in accordance with the VDA 270 standard. The results show that the addition of the newly developed RESCOFIL^® fillers significantly reduces the odor intensity of the recycled material to below the threshold value of 3, meaning that it is no longer perceived as unpleasant.

Thermoplastics are found in almost all industrial sectors:

Polypropylene
Polypropylene is used in a wide variety of applications. It is processed by injection molding into parts for electrical engineering, automotive engineering, and household appliances, as well as by extrusion into fibers and films. In the automotive industry, large parts such as side and door sills or interior trim are made from these compounds.

Polyamide
Polyamide 6 and polyamide 66 are the most widely used engineering plastics worldwide. They are used because of their high heat resistance, high hardness, and rigidity. In addition, polyamide 6 is characterized by good damping properties.

Polyethylene
Whether as packaging for food, in vehicle construction, in medical technology, in construction for thermal insulation, or in agriculture: polyethylene films are used in a variety of applications and must meet corresponding requirements. In addition to mechanical properties, optical requirements such as transparency, gloss, or opacity are often added.

Examples of applications:

• Packaging: Films, bottles, containers (PE, PP, PET)
• Automotive: Engine covers, trim strips, interior parts, tanks, bumpers (PP, PA, ABS)
• Medical technology: Disposable devices, tubes (TPU, PEEK)
• Construction & electronics: Window profiles, insulation, housings
• Consumer goods: Device housings, sporting goods, furniture

Thermoplastics offer a number of key advantages that make them the largest group of plastics in terms of volume. Their reversible deformability allows components to be molded multiple times, reused, and recycled efficiently—a clear advantage in the circular economy.

At the same time, they score points for their cost-efficient production, low weight, and energy-efficient processing in established processes such as injection molding or extrusion.

Another advantage lies in the wide range of properties that can be specifically enhanced by additives or mineral fillers, from higher impact strength and increased rigidity to improved thermal conductivity or flame retardancy.

As a result, their range of applications extends from simple standard solutions to highly specialized high-performance applications in technology and industry.

Polyethylene (PE): inexpensive, easy to process, and chemically resistant; typical applications include films, canisters, pipes, and packaging.

Polypropylene (PP): stiffer and more heat-resistant than PE, used for automotive parts, textile fibers, and numerous components in vehicle interiors.

Polyethylene terephthalate (PET): transparent, strong, and highly recyclable; best known for bottles, packaging, and fibers. PET plays a lesser role in HPF, as it is usually processed unfilled.

High-performance thermoplastics such as PEEK and PPS: extremely resistant to temperature and chemicals; indispensable for the most demanding applications in aviation, medical technology, and the semiconductor industry.

The raw materials from HPF The Mineral Engineers provide valuable services as fillers in many thermoplastic applications.
The reason: the demands placed on modern plastics, for example in the automotive industry, are constantly increasing. Polymers alone can no longer meet the required property profiles. They are therefore reinforced with high-quality, functional fillers based on granular cristobalite, needle-shaped wollastonite, and plate-shaped muscovite and phlogopite mica.

These high-performance fillers make a decisive contribution to improving the mechanical and thermal properties of the compounds.

As functional fillers, they increase scratch resistance, reduce mechanical and thermal distortion, and improve tensile strength and tensile modulus while maintaining impact strength in the polymer system and thus in the finished part.

Polypropylene is used in a wide variety of applications. Among other things, it is processed by injection molding into parts for electrical engineering, automotive engineering, and household appliances, and by extrusion into fibers and films. Over the last decade, polypropylene has also been increasingly discovered as a material by the automotive industry. Here, large parts such as side and door sills or interior trim are manufactured from these compounds.

In polypropylene systems, the excellent reinforcement properties of the needle-shaped TREMIN^® 939 have proven themselves over the years. The surface-modified TREMIN^® 939 types, in particular, can be optimally integrated into the polymer and handled with ease.

Polypropylene compounds produced with TREMIN^® 939 offer the following properties:

• excellent impact resistance combined with high stiffness
• very good scratch resistance
• high heat distortion resistance
• low shrinkage of the finished parts

The use of plate-shaped mica MICA muscovite and TREFIL^® phlogopite can significantly improve the thermal and mechanical properties in polypropylene/polyethylene compounds.

This results in a significant reduction in shrinkage in both dimensions as well as an improvement in heat distortion sensitivity. There is also an increase in tensile strength and tensile modulus, as well as an increase in stiffness while maintaining toughness.

Polyamide 6 and polyamide 66 are the most widely used engineering plastics worldwide. They are used because of their high heat resistance, high hardness, and rigidity. In addition, polyamide 6 is characterized by good damping properties.

Short-needle, amino-silane coated wollastonite powders TREMIN^® 283 have been successfully used for many years as functional fillers for polyamides when warpage-free properties are required.

With the long-fiber TREMIN^® 939 grades, higher stiffness can be achieved here.The proportion of these fillers in the compounds ranges between 20 and 40 wt.-%. The polyamides reinforced in this way offer a variety of possibilities for designing distortion-resistant, stiff molded parts. The compounds reinforced with TREMIN^® are characterized by excellent stiffness, high heat and temperature resistance, and excellent dimensional stability (TREMIN^® 283). They also achieve high impact strength and excellent paint adhesion.

The use of surface-modified, platelet-shaped TREMICA^® muscovite and TREFIL^® phlogopite influences the mechanical and thermal properties in the polyamide compound through a range of positive effects. In addition to increased tensile strength, enhanced stiffness, and reduced shrinkage, improved shrinkage isotropy and a significant reduction in sensitivity to heat distortion can also be observed.

For thermoplastic applications, types from the SILATHERM^® product range are particularly suitable. The fillers have been tested in polyamide and polypropylene. Despite high filler contents, the mechanical properties remain at a very good level.

High-performance fillers based on mineral raw materials can influence required properties in plastic films. Especially SIKRON^® cristobalite, TREFIL^® anhydrite and MICROSPAR^® feldspar are suitable in this application.

The functional fillers offer the following advantages:

• excellent anti-blocking properties combined with good appearance
• high UV transmission values with good IR absorption
• barrier effect

If you want to learn more about thermoplastics and our filler solutions, write to us!

We are happy to help.