How safety footwear enhances protection in the workplace

How safety footwear enhances protection in the workplace

Safety shoes have an important place in the workplace. They protect the feet against injuries and help to reduce the number and severity of accidents. They can protect against punctures, cuts, burns and impact whilst also offering the individual a better grip when walking on a specific surface.

They have to follow basic requirements and offer additional protection for their area of application. For example, when working on a boat, the surface can be very slippery, so it is important to have a shoe which allows the individual to move around without the fear of slipping. For someone working with electricity, the shoe can prevent electrical hazard. Workers in the forest can also encounter a slippery surface from moss but there is also the possibility of getting cut when working with chainsaws. A safety shoe made from cut resistant materials can help prevent getting cut.


What are safety shoes?

Process of making a safety shoe

Fundamental requirements of safety footwear

Process of making a safety shoe

· Safety category S1

· Safety category S2

· Safety category S3

· Safety category S4

· Safety category S5

· Safety category S6 + S7


What are safety shoes?

Professional footwear can be distinguished into two categories. The first category is work footwear, meaning that the shoe is within the anti-slip and water repellent criteria, but the toecap and insole are not impact resistant.

The second category is called safety footwear, which is a shoe that must meet the EN ISO 20345 norms. This requires the shoe to have a minimum impact resistance of 200 Joules at the front-end part of the shoe and to be slip resistant on smooth and greasy floors in industrial environments. Different specific protections are then added onto the shoe to fulfill the protection criteria the shoe is meant for.

Process of making a safety shoe

A safety shoe begins with a conceptual design, which is then tested until it satisfies the requirements. The material for the upper part of the shoe is chosen depending on the functionality the shoe is supposed to have. The sole and the toe cap are also based on the function of the shoe.

Once all the materials have been chosen, the parts for the upper are cut out, assembled and then placed on the shoe last. Once on the shoe last, the toe cap is added underneath the main fabric and the shoe gets pressed together by a machine to help the shoe take form and make the toe cap fit well around the front part. Thermoplastic is then injected into the molds for the sole to then produce the outsole. Once the sole is connected to the upper part of the shoe, a safety shoe has been made. (You are interested in learning more about the specific requirements, when making a shoe last? Then click here.)

Fundamental requirements of safety footwear

The basic requirements of a safety shoe can be found in the standard basic (SB) degree of protection. This includes a sole which is anti-slip, anti-abrasion oil resistant and anti-static. The non-slip properties must be true on ceramic tiles with cleaning agents (SRA), on steel floor with glycerin (SRB) and on the two types of floors combined (SRC).

Furthermore, the materials used to build the shoe have to be water resistant, breathable, hard wearing, and strong. The shoe needs to be comfortable, and the toe cap needs to be impact and crushing resistant. The toe cap can be made from steel, plastic or aluminum and needs to have an impact resistance of 200 Joules. This means the toe cap should withstand a weight of 20kg from a fall height of 1 meter. A SB safety shoe provides the minimal amount of protection but provides more protection than a normal work shoe.

Process of making a safety shoe

All safety shoes must meet these basic requirements but there are additional requirements depending on the shoe’s area of application. The additional safety features on the safety shoes are depicted on the label via a symbol and can be divided into 3 categories: complete footwear, instep and the sole.

Complete footwear includes the following:

1. Puncture resistant (P) insoles, which are resistant to a puncture force of 1,100N.

2. Conductive footwear (C) which, by evaporating electrostatic charges, is electrical resistant from 0 to 100 kilohms.

3. Antistatic footwear (A) dissipates electrostatic charges between 100 and 1000 kilohms.

4. Heat resistant soles (HI) allows an insulation against heat up to 150 degrees.

5. Cold resistance soles (CI) allow an insulation against cold up to -17 degrees.

6. The heel area must absorb a minimum of 20 Joules energy (E). 

7. Metatarsal protection (M) provides additional safety for any of the bones in the foot.

8. Ankle protection (AN) adds additional ankle protection.

9. Cut resistant (CR) features are zones of the shoe which are resistant to getting cut.

10. Waterproofing (WR) means that the entire shoe must be waterproof.

Instep requirements are specifically directed towards the middle part of the foot. There is only one additional requirement, which is that the upper part of the shoe is resistant to water entering and the absorption of water (WRU).

The sole has two requirements. It can be resistant to contact with heat (HRO)  for temperatures up to 300 degrees and can also additionally be resistant to hydrocarbons (FO) which are highly combustible chemicals.

The different degree of protection provided by these safety shoes are indicated by the S, meaning standard, and a number. The higher the number, the more extensive the protection which goes from S1 up to S7. Safety shoes can be divided into two categories depending on the material the footwear is made from. The first category has a leather or other synthetic material upper (S1-S3, S6, S7) whilst the second category has an upper made from rubber, PVC or PU (S4 and S5).

Do you want to learn more about different plastics used in injection molding. Then check out our blog post here.

1. Safety Category S1

The degree of protection S1 meets all the basic requirements (SB) and additionally has closed, shock and energy absorbing heel (E). In addition the sole must be hydro-carbon resistant (FO) and anti-static.

S1 is good for interior activities in dry places where the importance of the shoe is to have basic protection. Contact with water tends to be non-existent. This applies to jobs such as electricians, mechanics, and craftsmen.

2. Safety Category S2

S2 meets the basic requirements and those of category S1, whilst also providing resistance to water and liquid absorption in the upper part of the shoe.

Safety shoes which follow the S2 requirements are useful in work areas with a high level of humidity where basic protection is still sufficient. This can be useful for someone who works in the food industry in the storage and the transportation. An airport worker would need an S2 safety shoe but with a plastic toe cap which is lighter than metal and allow to have a metal-free shoe which is beneficial in airports.

3. Safety Category S3

S3 meets the standards of category S2 and provides a lugged sole and a resistance to sole puncture. A lugged sole is a thicker outer sole with deep indentations.

Activities which happen in hostile work situations would benefit from S3 safety shoes. The shoe allows the person to have basic protection on their feet with the upper part of the shoe being water resistant and to have a sole which is thick and sturdy. Jobs in mining, agriculture, factories, or construction often use shoes with the S3 standard. A forestry worker needs protection against sharp working tools and slippery surfaces. This calls for a safety shoe with S3 requirements and cut resistant features. Production or factory workers also wear S3 safety shoes as they need to protect their feet from materials falling and be able to move around comfortably.

4. Safety Category S4

Boots with a S4 certification have a reinforced toe cap and are made of waterproof materials. The boots are not only water resistant, but they are meant to not let any water penetrate into the boot.

5. Safety Category S5

S5meets the same standard as S4 and additionally has an 2anti-perforation safety sole made of steel or a strong and durable synthetic material.
People working on boats or near any body of water would benefit from a S4 or S5 safety shoe as they are waterproof and allow for a good sole grip.

6. Safety Category S6 + S7


S6 has the same specification as S2 but the whole shoe is water resistant.

S7 refers to the S3 category and the whole shoe is water resistant. A fireman encounters multiple elements such as fire and water. Therefore, the entire shoe must be heat and water resistant. It must ensure that the high heat will not enter the shoe. The sole must be thick enough to stabilize the foot of the fireman when walking on challenging terrain. Shoes with a S7 certificate would come into consideration as they offer the most safety and the whole shoe is water resistant.

Yet, shoes made for the fire department usually follow their own safety standard EN 15090. S6 and S7 safety shoes were introduced as additional protection classes in June 2022 after the EN ISO 20345 norm was reviewed. Because they are freshly introduced, their presence in the safety footwear market is still limited.


In summary, a safety shoe is used in multiple applications to help protect the feet from any injuries and to facilitate movement in the workplace. There are basic requirements which all safety shoes must follow but they differ in their degree of protection. S3 shoes have the most extensive protection in the market at the moment.

If you liked this article, make sure to follow our Social Media channels. You can contact us anytime via LinkedIn, Instagram & Facebook. We are happy to receive any feedback and tell us what other topics are of interest to you. We will try to address them in the near future.

Thanks for checking out our blog!

Shoelast · Basics

Shoelast · Basics


Almost every shoe development starts with it. It gives a shoe the final form and is still formed out of wood in Germany. Can you guess what this article will be about? We want to tell you more about the shoelast!  


What is a shoelast and why do we need one?

Wood vs. plastic

Measuring a last

Different last categories

Making of a last


What is a shoelast and why do we need one?

A last is the base of almost every shoe and a form giving tool for shoe production. The form of each last is built upon the design (lifestyle products) and category (performance products) of the shoe it is made for. As well it generates the fit of the shoe e.g., a climbing shoe must sit tighter than a sneaker. The last can also create a function for a shoe by giving it a pre-forming.

Wood vs. Plastic

The base model of each shoelast in Germany is produced out of wood. White beech is generally regarded as the preferred wood to work with. Cutting, carving, creating sharp lines and transition from filler to wood is smoother.

Although because of the humid climate, wood is not suitable for the development process in Asia where HDPE (High Density Polyethylene) is the material of choice.

Still in Germany as well as in Asia production lasts are made out of HDPE.

Measuring a Last

There are different points to measure a last and to make sure that it was manufactured according to standards of the different sizes. The most important ones are marked in bold right next to the pictures below.

Main Measurement Points

Stick length
The stick length defines the widest point in the length of the last.

Ball width
Defines the widest point in the ball area and is measured with the help of a caliper.

Instep girth
The measurement of this point guarantees that the foot fits into the later shoe.

Ball girth
Is defined as the volume around the last in the ball area. This point can only be compared from last to last and not from foot to foot, because each foot is individual.

Heel Spring/Toe Spring 
Tells more about how the last is positioned in the later shoe and helps in the different categories.

Main Measurement Points

There are different measuring tools for controlling different points of the last.

A caliper is used to measure the stick length, the back cone height etc.

Measuring tape is used to define the ball girth and the last bottom length etc. and a ruler is needed to measure the toe spring.

In addition, heel blocks (metal plates) measure the heel spring. The PFI gauge is used to mark the ball girth position.

All measurements are noted down in the so called “Specification”, which is forwarded to the customer after the last development. With the help of the specification the customer can orientate his production settings.

Different Last Categories

Depending on the category of the shoe, the last is built for, there are different specifications the last must fulfill. 


A football shoe needs to sit tight on the foot. Therefore, a last for this category must have a narrow heel clip, a slim forefoot area and arch.

These functions provide extra stability for the whole foot and give a better connection to the football. As well the side walls of the last are rounded which makes it easier to handle the football. A football shoe must be comfortable as well because the players run a lot.


Running lasts need a balanced heel to toe spring ratio for a better roll up. Most running lasts have an asymmetric toe shape, which is adapted to the anatomy of the foot. This gives the foot sufficient space at the right place.

Also, it has a wide forefoot area. This  is because the foot can be swollen during or after running and should not be put under pressure. Quite often they also have a rounded heel, so the shoe adapts to the anatomy of the foot. In addition, running lasts have a narrow heel clip to avoid the foot slipping out of the shoe.

Spiked Running

A spiked running shoe has similar properties to a normal running shoe. Those shoes are used for short distance running. In addition, they also have stiff outsoles. Therefore, the toe spring in the last is raised which makes the power transmission on the forefoot easier.

To compensate the burden on the forepart special attention to the medial and lateral balance must be paid. The slim back part gives an extra stability, so the foot is not sliding out of the shoe.

Safety Boots

For safety boots the volume in the toe area is shrinked so the later toe cap fits. The side walls are high to adapt to the later boot shape. In general, the properties are like those of a hiking boot. The instep area is kept wide with attention to the later shoe construction e.g., zip, lace, slip on.

These lasts have a lot of volume to compensate for thick materials, foot beds and water resistant membranes. In addition, people often wear thick socks in their safety boots.


For fashion lasts it is hard to define any fixed standards because, as the category suggests, they are built according to current fashion trends. It is not uncommon that a shoe, originally from another category gains prominence in the fashion industry.

Normally the back part is standardized but aspects such as toe depth, shape and the overall length of the last can vary.


Climbing shoes have an extreme tight fit, a curved arch and forefoot. The toe area is asymmetric with point over the big toe. This is done because the big toe is the most powerful toe. The big toe can hold the entire body weight for several seconds, which is often required when climbing.


The properties of children lasts can vary for certain age range groups and categories. It is crucial throughout all categories, that enough room is given to the growing feet with all areas carefully considered.

Also great attention needs to be paid to the toe spring, which should not be too low. The bones in children’s feet are too weak to properly roll their foot and would fall. The fitting is extremely important because otherwise it is possible that the foot can be deformed.


Sandal lasts are produced closer to the real foot length and still the bottom is rather wide because of the spread of the foot during walking. They have slim, low sidewalls and often a sculpted bottom for the molded footbed. The toe depth does not play a role in this category because it is open.

Making of a Last


In the development process, there are three commonly used methods to start the process.

Base last
The footwear developer aims to produce a new shoe which uses another model as the base – the so-called base last. This is the most used method. With the help of the base last not every new development needs to start from scratch. Rather a completely new shoe can be created with changes on an existing last.

There are different use cases in which this development method is needed e.g., the footwear developer would like to produce the same shoe, which is already on the market, using a new material. Or the production is changed from Strobel to AGO (If you would like to know more about these production methods, be sure to check out our blog post about heel counters.)

Brand Designer send a rough idea of a new shoe. A meeting is then scheduled to discuss materials, exact form, and function. Afterwards the last is created.

Reference Shoe
The last method is working with reference shoes. The shoe developer gives the last manufacturer different shoe models which account as reference shoes. The new model should be a mix in design of the reference shoes. The fit is defined by the shoe developer. 

The data is then transferred and a wooden base last is milled. On these last further changes can be done.


Model confirmation & alterations
Traditionally lasts were confirmed by eye, but with the aid of CAD, comparisons can be made from version A to B. This leads to a better control and visibility of alterations.

CAD can as well be used as a tool to make minor adjustments, but it‘s not capable of creating what the experienced model maker can with the last.

Fully graded last
Measurement is taken from stick length and ball girth. This value is graded up and down freely using the appropriate grading system. The most commonly used systems are the British, American and French one but they can also be customer specific.

Coordination grading
Specific areas of the last stay stable, allowing the rest of the last to grade naturally e.g., stick length.


Production Last Material

The basic material of these lasts is High Density Polyethylen (HDPE). It belongs to the group of polyolefins. Polyethylene is a semi-crystalline thermoplastic produced by polymerization of ethene. The melting point lies at 120°C.

At framas all normal production lasts are produced using HDPE. This plastic withstands humidity changes and is strong enough to endure the varying types of processes and pressures during the production process.

Basic Production Process

The last block is first rough milled to shape, attached to the machine at the toe and heel part.

At this time a system for easier delasting process e.g., last with vertical hinge is included.

Firstly, holes are drilled at specific locations for the hinge pins.

Following cuts are sawn with an exact radius for optimal hinge movement and length reduction.

In the next step cuts are also made inside the last to accommodate the hinge location.

In the last step of the vetical hinge inclusion the hinge and the last are assembled together.

At this point the basic production process continues and is the same for every last.

The comb holder is milled in the last, which is needed to hold it in place in the coming machines.

Afterwards, the back and front of the last, which were previously needed to hold it in place, are cut off.

The last is then fine milled to achieve a smooth and precise finish.

In the next step the stick length is measured with the help of a caliper. In addition, a measuring tape is used to define the ball girth.

After that the fine milled last is cut to the correct production back cone height.

The surface of the last is then burned to give it a shiny, polished look and to improve the detail of the laser marking.

The last is afterwards marked with a laser, which typically includes the company logo. Depending on the customer’s preference, different stamps such as production date or last number may be added.

A hole is drilled into the last to accommodate the socket, which is needed for later positioning of the last in the production machine.

The socket is inserted into the hole, which allows for secure and precise positioning of the last in the production machine.

Further Processes

At framas Germany the produced lasts are only used as reference model, archive pages and small series for European production. The main production of lasts happens in Asia with our partner YinHwa.

After production the lasts are then sent to the customer for further testing, processing or directly to the shoe factories, where they are used for production.

If you liked this article, make sure to follow our Social Media channels. You can contact us anytime via LinkedIn, Instagram & facebook. We are happy to receive any feedback and tell us what other topics are of interest to you. We will try to address them in the near future.

Thanks for checking out our blog!

Material Basics · Injection Molding

Material Basics · Injection Molding

Injection Molding in the footwear industry

The range of plastics is huge. To not lose track, in this blog we focus on plastics used in injection molding within the footwear industry. But first of all, what is injection molding?

Injection Molding is a commonly used manufacturing technology in the footwear industry. In this technology a thermoplastic material is melted into a liquid, either rubber or plastic, injected into a mold and then cooled down. The mold is determining the final 3D-shape of the component e.g., outsole.


What is plastic?

Synthetic polymers · Four different groups

Thermoplastics in injection molding

Thermoplastic Polyurethan (TPU) – The star of the thermoplastics

Polyamides (PA) – The stiff ones

Polyether Block Amide (PEBA) – The luxury one

Styrene-Butadiene-Styrene (TPS-SBS) – The biggest group


What is plastic? 

And now continuing with some chemistry: The correct chemical term for plastic is polymer. The word polymer comes from the Greek prefix polý-, which means „many“, and the suffix -méros, which means „parts“. Polymers = „Many parts“.

Polymers are giant molecules made up of chains or rings of linked repeating subunits called monomers.

Natural Polymers
  • Cellulose
  • Cotton
  • Wool
  • Amber
  • DNA
  • Natural rubber
  • Starch

Synthetic Polymers

  • Polyethylene (PE)
  • Polypropylene (PP)
  • Polyvinyl chloride (PVC)
  • Polystyrene (PS)
  • Polyamide (PA)
  • Polyetherblockamides (PEBA)
  • Thermoplastic styrene elastomers (TPS)
  • Thermoplastic Polyurethan (TPU)
  • Polyurethane (PU)
  • Epoxy resin

Synthetic polymers · Four different groups

First the bad news: Not very surprisingly, the footwear industry’s focus is still on synthetic polymers which are mostly not biodegradable. Good news, due to their melting properties, with the right idea, concept, design, and process some synthetic polymers can be the core material for real material loops.

Please do not worry, natural polymers will be payed attention to in subsequent blogs. So first, let’s have a deeper look into synthetic polymers. The “synthetics” can be grouped into 4 types – relevant for injection molding.

Thermoset Polymers

The first group is
Thermoset Polymers.

Its polymers become irreversibly hardened due to extensive cross-linking between the polymer chains upon being cured. (e.g.
Epoxy Resin, Polyurethanes (PU))


The second group is Elastomers.

Elastomers are lightly cross-linked and very elastic.They can be reversibly extending but the curing is irreversible (e.g. vulcanization)

Thermoplastic Polymers

The third group is Thermoplastic Polymers.

Its polymers become moldable above a specific temperature and solidify upon cooling. e.g., PE, PP, PS, PET, PA, PC

Thermoplastic Elastomers

A fourth hybrid form is Thermoplastic Elastomers.

They are a physical mix of polymers with both thermoplastic and elasto-meric properties but they are fully re-meltable e.g., TPS, TPU, EVA and PEBA

Thermoplastics in injection molding

Now you know everything about the different polymer groups, but which of those are now used in injection molding? The answer comes here. Due to their flexible characteristics the two groups of Thermoplastics are perfectly right.

When thermoplastics are heated, they melt to a liquid which makes them suitable for the injection molding process. These materials can be cooled and heated several times without any change in their chemical structure. Moreover, depending on the desired injection parameter only minor changes in the mechanical properties, e.g., colder molding temperature, are needed.

In essence, Thermoplastic is suitable for mass production of components because of its short circle time and its melting abilities. 

Further, we will give you an overview about one Thermoplastic Polymer

  • Polyamides (PA)

 and three Thermoplastics Elastomers

  • Thermoplastic Polyurethan – (TPE-U or short: TPU)
  • Polyetherblockamides – (TPE-A or short: PEBA)
  • Thermoplastic Rubber Compound (TPR) – (TPE-S = TPS = SBS+PS)

All four are commonly used for injection molding in the footwear industry. And in case it was not mentioned yet. All four are recyclable.

    Thermoplastic Polyurethan (TPU) – The star of the thermoplastics

    One of the (still raising) stars in the footwear industry, is the material Thermoplastic Polyurethan (TPU). TPU was first discovered in 1937 by Otto Bayer and his coworkers at the labs of I.G. Farben in Leverkusen, Germany. A TPU is a so-called „block copolymer“ consisting of alternating sequences of hard and soft segments. It is formed by a poly-addition reaction between methylen-diphenyl-diisocyanates (MDI), one or more short-chain Diols („chain extenders“) as well as long-chain Diols.

    The variation of the ratio, structure and/or molecular weight of the reactants allows chemists to create an enormous variety of TPUs (with some restrictive limitations). Depending on the desired material properties, TPU grades can be produced fine-tuned and customized along a wide range of requirements. Besides its flexibility and durability, TPU has several mechanical benefits over other elastomers: It has an extraordinary tensible strength, a solid load bearing capacity, and an enormous elongation at break.

    TPU can be classified in three types: Polyester, Polyether, and Caprolactone, whereas only the first and the second type have relevance for footwear industry and will be discussed further.



    Chemically expressed Polyester is the category of polymers which contains the ester functional group in every repeat unit of their main chain.

    As a specific material it mostly occurs as the type of polyethylene terephthalate, which is abbreviated with well know term PET. Polyester exists in both natural and synthetic forms. When it comes to sustainability matters all natural occurring polyesters are of course biodegradable, whereas only a few of the synthetic ones are.

    Polyester has three functional benefits which explains its extensive usage in the clothing and footwear industry. First, Polyester has excellent oil and chemical resistance. Secondly, the abrasion resistance is good, and lastly its physical properties are well-balanced.


    Polyether is the polymer category which contains ether linkages in their main chain.

    The fact that Polyether TPU has excellent hydrolysis resistance, and that it is durable against microbial attack makes Polyether suitable for applications requiring contact to water. Even better, Ether has superior low temperature flexibility and good abrasion resistance, which qualifies the material for e.g., outdoor winter activities. When it comes to combining Polyether to other plastics in the same application, it is quite helpful that it has good bonding abilities to Polyamide 12 (check section Polyamide below). One disadvantage compared to Polyester is that Polyether is more expensive.

    A second way to classify TPUs is the distinction between “aromatic” or “aliphatic”.

    Aliphatic TPU

    Aliphatic TPUs are based on isocyanates as H12MDI, HDI or IPDI, are light stable and offer excellent optical clarity. Unfortunately, Aliphatic TPUs are expensive compared to aromatic Polyester and aromatic Polyether which disqualifies them for a vast of footwear applications.

    Aromatic TPU

    Aromatic TPUs are based on isocyanates as MDI and count as so-called „Workhorse products“, since they can be used in almost all applications which require flexibility, strength, and toughness.

    As indicated above, TPU materials can be used for almost all categories of footwear applications. The hardness can be adjusted from very soft (e.g., sneaker outsoles) to very hard (e.g., shank applications). Moreover, TPU is UV resistant and can therefore be used for articles which are exposed to sunlight.

    Let’s pick some requirements of footwear components which are perfectly fulfilled by TPU.

    Side panels need to be UV resistant, have an appropriate strength to resist the pulling of laces and need to be flexible (shore A) bend along the upper. External heel counters need to be both UV resistant and hard/stiff enough in accordance to protect and support the heel. Shanks need to be tough and stiff (Shore D) and UV resistant.

    There are actually great examples of existing shoes on the market, which are totally made of TPU materials and can therefore be fully recycled. 

      Polyamides (PA) – The stiff ones

      Another classical material of injection molding in the footwear industry are Polyamides (PA). Chemically speaking, Polyamides are long-chained molecules in which the repeating units in the molecular chain are linked together by amide groups. Amide groups (CO-NH) are commonly formed by a poly-condensation reaction between a carboxyl group (COOH) and an amine group (NH2).

      PAs occur both naturally (e.g., proteins, such as wool and silk) and synthetically. The footwear industry uses synthetical PA, such as well-known Nylon.

      PAs commercially exist in different Polyamide types, such as PA6, PA6.6, PA4.6, PA6.10, PA11, PA12. Depending on the number of carbon atoms in between the amide groups physical properties such as density or liquid absorption vary on a wide scale.

      Compared to TPUs Polyamides are considerable stiffer. Therefore, they are mainly used for applications where a certain reinforcement is required, e.g., a Shank system, Strobel insole board, eyelets.

      But PA has its limitations. In comparison to PA11 and PA12 especially PA4.6, PA6, PA6.6, PA6.10 absorb more water & humidity. Moreover, low temperature harms the flexibility of PA, which disqualifies PA for outdoor activities. Compared to TPU, the price of PA is relatively high. You can tell as a rule that the longer the PA chain, the more expensive the PA becomes. A PA12, for instance, has almost double the price of a PA6.

      Due to the stated limitations and except for a few PA6 grades, mainly PA11 and PA12 grades have been successfully established in the footwear industry, usually in high performance applications.

      A PA12 soccer outsole needs to be light weight, reinforced, UV resistant and flexible even under low temperatures. A PA12 soccer outsole in connection to TPU ether studs works perfectly, because of the bonding ability of PA with TPU (TPU has a better traction behaviour and is more comfortable to walk on). 

      Polyether Block Amide (PEBA) – The luxury one

      Polyether Block Amide (PEBA) count as the luxury, high performer under the materials for the footwear industry.

      What is PEBA, chemically speaking? PEBA materials are block copolymers made up of rigid polyamide blocks and soft polyether blocks. By manipulating these blocks and their relative ratio a large property spectrum from very hard and rigid to very soft and flexible can be achieved.

        PEBA grades combine the benefitting properties of Polyamides (e.g., toughness, low density) with the high flexibility/elasticity of Polyether’s:

        • Low temperature flexibility and impact resistance (at temperatures lower than -40 °C)
        • Relatively low density (1.01 g/cm3) compared to TPUs (1.19g/cm3)
        • Proper energy return
        • Fatigue resistance
        • Good chemical resistance
        • the lightest of all thermoplastics

        Similar to TPU,  the hardness of PEBA can be adjusted from very soft (e.g., external heel counters) to very hard (e.g., insole boards, sprint plates, or outsoles). The option of usage are almost endless. Especially in the sport footwear industry PEBA grades are well established, but due to their relatively high price (approximately as expensive as PA12) they are mainly used for high-performance applications. The above stated superior properties PEBAs are predestined for winter sports (e.g., ski and snowboard boots) and other competitive sports where low weight, weather resistance, energy return, and fatigue resistance are required (e.g, ultra trail running).

        And as if all these positive skills of PEBA are not enough: Designed and applied in an clever way, PEBA is also sustainable! There are actually great examples of existing footwear on the market, which are totally made of PEBA materials and can therefore be fully recycled.

          Styrene-Butadiene-Styrene (TPS-SBS) – The biggest group

          The most occurring thermoplastic elastomer (TPE) is the styrene based thermoplastic styrene elastomer (TPS).

          The easiest, best performing, and cheapest TPS is a mix of styrene and butadiene, Styrene-butadiene-styrene (SBS). As illustrated above, the butadiene is the elastomeric (soft) linking segment between the polystyrene blocks. Due to its synthetic nature, SBS is logically not biodegradable. In its not hydrated form, it is almost only used to modify other materials. Common applications are in the area of street construction and baby diapers. SBS can also be used in the footwear industry. However, due to its poor UV resistance it is more suitable for footwear components which are protected from the sun (e.g., heel counters).

          SBS is rarely used in an unmixed form because it has an amorphous structure and therefore melts very slowly when exposed to heat. To improve its properties, it is often mixed with thermoplastics. For recycling, and the injection molding process of heel counters, pure (Nonylphenol free) SBS is necessary.

          The only element to be added, which improves the properties of SBS without harming the ability of thermo-recycling, is Polystyrene. Polystyrene, as mentioned above, makes SBS stiffer and is already an element of SBS.

          Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. It occurs solid or foam and is not biodegradable, cannot be decomposed by bacterias. Conventional polystyrene is clear, hard, and brittle. It was first discovered in 1839 by the apothecary Eduard Simon in Berlin. PS is a very cost-efficient material. It is also one of the most widely used plastics. PS can be the material for protective packaging, containers, lids, bottles, trays, tumblers, or disposable cutlery.

          In the footwear industry High Impact Polystyrene (HIPS) is used, which is less brittle and impact resistant even at low temperatures. High availability and low prices on the secondary market make PS suitable for recycled components e.g. our heel counters, even though the properties limit the application.

            To sum up, an overview of the prices of all materials we introduced in this post and their hardness range.

            If you liked this article, make sure to follow our Social Media channels. You can contact us anytime via LinkedIn, Instagram & Facebook. We are happy to receive any feedback and tell us what other topics are of interest to you. We will try to address them in the near future.

            Thanks for checking out our blog!

            Material Basics · Injection Molding

            The Heel Counter

            What is a heel counter? 

            An internal heel counter is a non-visible shoe component placed in the back of the shoe to stabilize and tighten the back of the heel that shapes around the Achilles tendon of your foot. Accordingly, internal heel counters are used throughout most footwear categories fulfilling several functions. It should protect the heel from injuries, ensure a stable heel support, guarantee a comfortable wear feeling, and fit perfectly to the heel shape.

            Shoes with an external heel support or no heel support (e.g. sandals), are the only constructions where no internal heel reinforcement is applied.


            Strobel vs. AGO

            Heel Counter vs. Thermo-Sheets

            Heel counter material


            History framaprene

            Heel Counter
            Strobel Heel Counter

            Strobel vs. AGO

            Depending on the manufacturing process, there are two types of heel counters. Experts on the field, call heel counters either “AGO” or “Strobel”. At first glance, AGO and Strobel heel counters seem to be quite the same. However, a tiny construction element makes the difference. 

            The decisive criteria which differentiates an AGO from another type of heel counter is that the AGO has a flange. The flange is a small extending element on the bottom of the heel counter. In collaboration with the 3D shape of a heel counter, it provides extra stability, and most importantly it ensures the perfect fit on the heel during the manufacturing process.

            The name AGO comes from the manufacturing method AGO (Another Great Opportunity), invented by the Milanese tanner Francesco Rampichini in 1911, in which this type of heel counter is used. To construct the shoe in the AGO method, first the heel counter is glued into an opened upper element (without insole). Subsequently, the upper is mounted on a shoe last, which is already prepared with an insole. The sealing is then made by gluing or pinching the lasted upper to the bottom of the insole. During the whole mounting and sealing process, the AGO heel counter’s flange prevents it from moving away from its perfect heel position.

            Heel counters without a flange are called Strobel. They are suitable for e.g., a Strobel construction, which is the most common manufacturing method in the sport shoes industry. The Strobel method requires specialized machines. The name Strobel has its origin from the company with the same name, which invented this type of footwear manufacturing. Differing from the AGO method, the stabilization and fit of the heel counter only comes from the perfect adaptation of the 3D heel counter to the shoe last.

            In this method, the upper is already prepared with a glued (or sometimes even stitched) heel counter inside. Before even mounting it to the last, the upper is already connected and sealed to the so-called “Strobel board”. A Strobel board is much narrower and thinner compared to insoles usually used in the AGO method. The stitch sealing of upper, Strobel board, and heel counter can be imaged with the look of a sock.

            Because extending heel counter flanges would collide with the stitches of the Strobel connection, a Strobel heel counter does not have any flanges.

            In many footwear categories the Ago and Strobel methods are merging. Some shoes are often manufactured with the Strobel method on the heel part of the foot (remember: stitches) and with the AGO method on the front foot. Logically, the method used for the heel part holds sway over the choice of heel counter type.

            Strobel Heel Counter


            Ago Heel Counter


            Heel Counter vs. Thermo-Sheets

            Both heel counters and thermo-sheets are functional elements located on the heel of a shoe. As the names already tell, heel counters and thermo-sheets are not the same. What is the difference again? Don’t heel counters and thermo-sheets have the same purposes of protection, stability, and fit? Yes, both are aiming for all three criteria, but when viewed from the functional perspective, heel counters perform better:

            Thermo-Sheets are die-cut 2D counters which are leveled to the last shape via heat and pressure.

            Heel counters are injection molded and have a 3D shape. The fact that heel counters can be designed in perfect accordance with the shape of the shoe last (based on which a shoe is manufactured) ensures a superior fit over 2D thermo-sheets.

            Still, there are advantages of thermo-sheets, making them attractive: cost effectiveness and flexibility. The construction of a thermo-sheet tooling (cutting die) costs less than a heel counter mold, and is herewith more flexible when it comes to design changes. Therefore, thermo-sheets usually have a lower unit price.

            Even though price competitiveness, which is one of the most important criteria of the footwear industry, is unchanged, surprisingly an increasing quantity of thermo-sheets has recently been replaced by heel counters.

            Here is why:
            On the one hand, sustainability aspects are gaining importance, and the production of thermo-sheets has an unavoidable flaw: the process of die-cutting and skiving accrues waste. Opposed to that heel counters are injection molded and therefore produce less waste. Moreover, can consist of up to 100% recycled material, whereas most thermo-sheets only contain a relatively small share of recycled ingredients.

            On the other hand, new design and manufacturing concepts of heel counters enable a competitive price compared to thermo-sheets.

            Generally speaking, thermo-sheets are preferably used for casual footwear, where the component price is usually a more important criterion. In high performance footwear categories, where high resistant protection, strong heel support, good fit, and advanced wearing comfort is required heel counters are in use.

            Heel Counter Material

            framas Heel counters are made from 100% recycled raw materials. The hard component is recycled Polystyrene and the soft component recycled SBS (resp. TPR = Thermoplastic Rubber). By compounding the soft and the hard material components in different ratios, framas currently offers 3 fully sustainable heel counter compounds. 

            • framaprene ECO R100 87A


            • framaprene ECO R100 95A
              Standard · Used for around 70% of all applications


            • framaprene ECO R100 55D
              ard · Specialty grade used for casual applications

            Material Components

            Styrene-Butadiene-Styrene  Soft Component

            Reprocessed single-source post-industrial waste from the sanitary products industry (foil extrusion).

            This source ensures stable mechanical properties comparable to virgin SBS grades and enables our fully sustainable compounds to be used even for performance applications.

            High Impact PolyStyrene  Hard Component

            Reprocessed post-consumer and post-industrial  waste (consumer electronics and food packaging) from constant sources in Japan.

            Since the replacement of the virgin polystyrene in 2013, the weight of recycled HIPS has reached up more than 8,500 tons until today.


            Every year around hundreds of millions of shoes are produced. Since heel counters can be found in almost all of them, their impact on the environment is considerable high.

            framas group is currently producing more than 100 million heel counters per year which requires around 2,500 tons of raw material.

            Considering that framas heel counters are made of 100% recycled raw materials, the material-related carbon footprint was reduced by more than 90% (> 7,500 tons of carbon per year) compared to the usage of virgin materials.

            For next generation compounds framas is currently investigating bio-based and bio-degradable options and also target to reduce the carbon missions caused by the logistics (trucking, shipping) in the entire supply chain for heel counter materials.

            History framaprene

            Having expertise in last-making since 1948, framas produced the first complementary heel counters in the late 1970s. Since then, more than 90 heel counter series have been developed, some of them being produced for more than 40 years.

            In 2009, framas founded an R&D project in cooperation with the University of Applied Sciences in Kaiserslautern, Germany targeting to develop a well performing heel counter compound partly based on recycled ingredients.
            As a result, the framaprene ECO grades were introduced, containing more than 50% recycled Polystyrene. After intensive product testing and material evaluation, those grades were officially approved and launched in mass-production in 2013, reducing the usage of virgin materials in specific products by more than 1,000 tons per year.

            In 2017, the first R&D trials with the recycled SBS (soft component) were initiated with the target to finally provide a fully sustainable heel counter compound.​

            The first 100% recycled framaprene grade was introduced in 2019 but it took another 18 months to establish a solid vendor base to guarantee a safe R-SBS supply of sufficient quantity and reliable quality.

            From the middle of 2021, after almost 12 years of continuous progress, framas Group can cover an annual production quantity of more than 100 million pairs exclusively based on recycled ingredients, reducing material related carbon emissions by more than 90% compared to the usage of virgin raw materials. A GRS certification is currently under process and will be finalized until spring 2023.

            If you liked this article, make sure to follow our Social Media channels. You can contact us anytime via LinkedIn, Instagram & Facebook. We are happy to receive any feedback and tell us what other topics are of interest to you. We will try to address them in the near future.

            Thanks for checking out our blog!