Recently, I had the opportunity to visit the KPA trade fair in Ulm, Germany where I stopped by the booth of Technoform—a specialist in the extrusion of highly filled plastics. I was joined by Dirk from Technoform, and together we explored the fascinating world of glass fibers and their integration into plastics.
Dirk (left) from Technoform Tailored Solutions discussing with Herwig the importance of glass fibers integration into plastics.
Why Glass Fibers?
Our discussion centered on the advantages of incorporating glass fibers into plastic materials. Dirk explained that glass fibers are not only cost-effective but also significantly enhance the mechanical properties of plastics. When used as a compound, glass fibers reinforce the plastic, making it stronger and more durable.
Types of Glass Fibers and Their Applications
There are several ways to integrate glass fibers into plastics:
-Short Glass Fibers: Ideal for optimizing component properties at a relatively low cost. These are commonly used when a balance between performance and cost is needed.
-Long Glass Fibers: Preferred when higher impact resistance or damping effects are required.
-Continuous Glass Fibers: Used specifically for components that demand increased stiffness.
Dirk highlighted that the choice of fiber type depends on the specific requirements of the component being produced.
A Practical Example: The Child Seat Frame
One of the most interesting examples we discussed was a child seat frame made of polypropylene. In this application, both short and continuous glass fibers are combined. The short glass fibers provide the general mechanical strength, while continuous fibers are strategically placed at weak points to reinforce rib structures. This targeted approach results in local stiffening, which further stabilizes the entire component mechanically. They used their pultrusion technology to create thin polypropylene profile with unidirectional glas fiber reinforcement. The cut profiles where placed in the injection molding tool and overmolded with polypropylene.
Takeaways
This conversation with Dirk offered valuable insights into how the right combination of glass fibers can optimize the performance of plastic components. By understanding the unique benefits of each fiber type, we can better tailor our materials to meet specific application needs.
Thank you to Dirk and the Technoform team for sharing their expertise and practical examples. I look forward to bringing more of these industry insights to our polymer engineering community in the future!
If you’ve ever wondered how to choose the right injection molding machine for your project, understanding clamping force is key.
Today, we’ll break down how to calculate the clamping force required for parts with wall thicknesses both below and above 1.5 mm. Mastering this calculation not only ensures high-quality parts but also helps you make smarter, more efficient equipment choices.
Let’s dive in!
Case 1: part wall thickness below 1.5 mm
Clamping force F [kN] = projected area A [m2] * filling pressure pf [bar] / 100
Hello and welcome to this new blog post in which we discuss the functional groups of polymers.
Introduction — why functional groups matter
Figure 1: Overview of the 11 functional groups of polymers.
Functional groups are the recurring atom clusters in organic molecules whose chemistry largely determines material properties (polarity, hydrogen-bonding, thermal stability, chemical resistance, chain rigidity, degradability, etc.).
In polymers, the functional group(s) present in the backbone or pendant positions control bulk properties and processing behaviour, so identifying the dominant functional group is a quick route to predicting performance during material selection.
What are the 11 functional groups we will discuss in this post:
Imide group
Sulfone Group
Amide Group
Ester Group
Ketone Group
Sulfide Group
Ether Group
Arene Group
Alcohol Group
Alkane Group
Haloalkane Group
Let us get starting!
1) Imide group — structure: –CO–N–CO– (cyclic or linear imide)
Figure 1: Functional groups of polymers: Imide group.
What it gives: outstanding high-temperature stability, good chemical resistance, high glass transition (rigid backbone), low creep.
Typical polymers / examples: Polyimides (e.g., Kapton®, Vespel®) used for high-T films, electrical insulation, aerospace parts. Polyimides are classic high-performance plastics made from dianhydride + diamine routes.
Notes: Alkyl groups (R-) are saturated, non-aromatic hydrocarbon chains derived from alkanes (e.g., methyl, ethyl).
Aryl groups (Ar-) are aromatic rings derived from compounds like benzene.
2) Sulfone group — structure: –SO2– (often between aryl groups)
Figure 2: Functional groups of polymers: Sulfone group.
What it gives: high thermal stability, hydrolytic stability, rigidity and flame resistance; good dimensional stability and toughness in amorphous engineering resins.
Typical polymers / examples: Polysulfones / Polyethersulfones / Polyphenylsulfone (PSU, PES/PESU, PPSU — trade names include Ultrason®, Radel®). Widely used in medical devices, plumbing/valves, electrical components and under-the-bonnet automotive parts.
3) Amide group — structure: –CONH–
Figure 3: Functional groups of polymers: Amide group.
What it gives: strong intermolecular hydrogen bonding resulting in high strength and toughness, relatively high melting point, moisture uptake (hydrophilicity increases with amide density), good abrasion resistance.
Typical polymers / examples: Polyamides (Nylons) — PA6, PA66, PA11, PA12; Semi-aromatic polyamides such as PPA, and fully-aromatic polyamides (aramids) such as Kevlar® for ballistic & high-strength uses. Use in fibers, gears, bearings, structural components.
4) Ester group — structure: –COO– (ester linkage in backbone)
Figure 4: Functional groups of polymers: Ester group.
What it gives: backbone polarity (good mechanical strength), susceptibility to hydrolysis (hence biodegradability for some), good melt processability (thermoplastic polyesters).
Typical polymers / examples: Polyesters — PET (polyethylene terephthalate), PBT, PLA (polylactide). Used for fibers, bottles, films, engineering thermoplastics and (for some aliphatic esters) biodegradable medical devices.
Example: Carbonate functional group
If the organic rest "R1" is replaced by a oxygen, R-O-C(=O)-O-R2, we obtain a carbonate ester, which are utilized in the creation of polycarbonate (PC).
5) Ketone group — structure: –CO– (ketone carbonyl in backbone or adjacent to aromatic units)
Figure 5: Functional groups of polymers: Ketone group.
What it gives: increased backbone polarity and stiffness; when combined with ether linkages in high-performance families it confers elevated Tg and chemical resistance.
Typical polymers / examples: Poly(aryl ether ketone) family (PAEK) — includes PEEK, PEK, PEKK — used for high-temperature structural parts, bearings, medical implants, and additive manufacturing in demanding applications. PAEKs combine aryl, ether and ketone functionalities giving excellent thermo-oxidative stability.
Figure 6: Functional groups of polymers: Sulfide group.
What it gives: enhanced temperature resistance, chemical and solvent resistance; excellent flow for injection molding; inherent flame retardant properties; excellent dimensional stability;
7) Ether group — structure: –O– (alkyl or aryl ether linkages)
Figure 7: Functional groups of polymers: Ether group.
What it gives: flexibility (aliphatic ethers), good low-temperature toughness, and for aromatic ether linkages (polyarylethers) increased thermal stability and oxidative resistance. Ethers reduce crystallinity when in backbone and improve chain mobility.
8) Arene (aromatic ring) group — structure: –Ar– (phenyl, substituted phenyl rings in backbone or pendant)
Figure 8: Functional groups of polymers: Arene group.
What it gives: backbone rigidity (high modulus), thermal stability, UV interaction (often poor UV resistance unless stabilized), pi-stacking that influences mechanical and barrier properties. Aromatic content generally increases glass transition and heat resistance.
Typical polymers / examples: Polystyrene (PS) — aromatic pendant phenyls on a saturated backbone; poly(phenylene), polyaryls and many high-performance polymers with aromatic repeat units (e.g., polyimides, PAEK family). Polystyrene is a major commodity aromatic polymer used for foams, rigid packaging and consumer products.
9) Alcohol (hydroxyl) group — structure: –OH (pendant or chain-end hydroxyls)
Figure 9: Functional groups of polymers: Alcohol group.
What it gives: hydrogen bonding, polarity, water solubility (if dense), reactivity for crosslinking (e.g., with isocyanates to form polyurethanes) or functional modification. Hydroxyls raise surface energy and adhesion.
Typical polymers / examples: Polyvinyl alcohol (PVA, PVOH) — water-soluble, used in films, adhesives and hydrogels; alcohol endgroups in polyols (polyether or polyester polyols) are core building blocks for polyurethanes.
10) Alkane group (saturated hydrocarbon backbone) — structure: –CH2–CH2– etc. (non-functional hydrocarbon chain)
Figure 10: Functional groups of polymers: Alkane group.
What it gives: low polarity results in low surface energy, excellent chemical resistance to polar solvents, high flexibility (especially in low Tg aliphatic polyolefins), good electrical insulating properties and very high production volumes (commodity plastics).
Typical polymers / examples: Polyethylene (PE), Polypropylene (PP). These are the polyolefin family used for films, containers, piping, and fibers. Expect low density, good toughness, and simple processing.
11) Haloalkane group (alkyl halide pendant or backbone) — structure: –C–X (X = Cl, Br, F)
Figure 11: Functional groups of polymers: Haloalkane group.
What it gives: increased flame retardance (e.g., chlorinated polymers), increased polarity and density, and ready sites for nucleophilic substitution or further modification; halogens can also raise refractive index and change dielectric properties.
Typical polymers / examples: Polyvinyl chloride (PVC) — chlorine on backbone carbons; fluoropolymers (e.g., PTFE — where fluorine dominates) are extreme cases with outstanding chemical resistance and low friction. PVC is used in construction, pipes, cable insulation and flooring; fluoropolymers are used where chemical inertness and high T performance are needed.
Mixed-functionality polymers & location of the group
Backbone vs pendant vs endgroup: a functional group in the backbone (repeat unit) typically dominates bulk mechanical/thermal behaviour. Pendant groups (e.g., the phenyl in polystyrene or the chloro in PVC) tune Tg, polarity and solubility. Endgroups mainly affect surface chemistry and reactivity.
Combinations are common: many engineering polymers combine functional groups (for example, PAEKs include arene, ether and ketone motifs; polysulfones include aryl, ether and sulfone units), which gives the unique combined property sets.
Overview of all the 11 functional groups of polymers
Figure 12: Overview of the functional groups of polymers.
Hello an welcome to a new blog post. In plastic part design, proper material selection and processability are essential considerations. Additionally, part marking plays a crucial role, as it enables more efficient sorting and recycling of plastic components. The two primary standards governing part marking are ISO 1043 and ISO 11469.
Example >PARA-(CF+MEF(x))<
Based on ISO 1043 (specifically ISO 1043-1 regarding plastics symbols), the notation >PARA-(CF+MEF(x))< is a part marking code used to identify the material composition of a molded plastic component made out of PolyarylAmide (PARA; PA-MXD6).
Figure 1: Plastic part marking example with focus on special additives.
MEF: This indicates a specific, likely proprietary, modification or additive blend. In the context of this material, it refers to special filler package, potentially containing Metal fillers, Elastomers, or special Fillers (MEF) which are used to enable EMI-shielding.
(x): Often followed by a number (e.g., in a technical data sheet, it might appear as >PARA-MEF(1)7<, this indicates the specific grade or a percentage/variant within the supplier's internal classification system.
> <: The angled brackets indicate that the part is marked in accordance with ISO 11469 for identification and recycling, as required for parts over a certain weight. ISO 11469 does not define a universal minimum weight for marking; however, industry standards (e.g., in automotive) generally require marking for parts weighing more than 100 grams. Smaller components, often those under 25 grams or with a surface area smaller than, are usually exempt from this marking requirement.
