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In the previous article, we introduced the processing technologies and diverse applications of TPE. In this final installment of the series, we will take a closer look at how thermoplastic elastomers are applied in real-world products. Through the development story of the Link Upon eraser, we’ll share how we began innovating materials for TPR erasers and TPE pencil grips, driven by our original intention to meet environmental trends and user needs.

Practical Topics in Thermoplastic Elastomers 
1. From Natural Rubber to Thermoplastic Elastomers
2. Properties, Processing, and Applications of Thermoplastic Elastomers 
3. Some Practical Applications of Thermoplastic Elastomers  

Author: Dr. Hong-Bing Tsai
Ph.D., Chemical Engineering, National Tsing Hua University
Professor, Department of Chemical and Materials Engineering, National Ilan University
Technology Director, AR Display Co., Ltd.

*Translated by Ching-Yuan Wu

Practical Topics in Thermoplastic Elastomers 3. 
Some Practical Applications of Thermoplastic Elastomers

[A Story About Link Upon Erasers]

There were two lines of words written on the whiteboard in the office of Mr. Lin* in Link Upon Company:

"Most countries were destroyed not by foreign enemies, but from within.
People often face existential problems without a proper sense of crisis."
These were the real cases often appeared in the history. 

Looking at the two lines of words, 
Mr. Lin asked, "Dr. Tsai, how do you think about the difference between research and development?"
Research is to find products or to create products, while development is trying to commercialize the products.”

Mr. Lin smiled and said, "Your idea is not going to hit the spot. Research only makes you happy, but development can make many people happy."
He reminded me that research and development cannot be isolated from the preference of consumers. 

When the memory of the eraser developing event of Link Upon Company appeared, I couldn’t help but feel warm in my mind.
The event began as an issue of survival. It was a story that happened more than thirty years ago. 

Mr. Lin asked, "Dr. Tsai, do you know which thing is the most profitable to sell?"

I smiled and said, "Manufacturing of chips should be the most profitable!"

"No, selling water is the most profitable. Do you know that? My friend sells juice products. He imports fruit powder from the United States, which costs 10,000 to 20,000 US dollars per ton. He adds water to make 100,000 cans, and each can sells 2 to 30 NTD. See how profitable it is!"

"I agree. But you don't manufacture beverages!"

"I found another thing that may be very profitable, that is stone powder. Calcium carbonate powder is only 50 cents per kilogram."

*Note: Mr. Ah-Hing Lin was the founder of Link Upon Advanced Material Corp.

Therefore, Link Upon Company started up an eraser project using stone powder. As mentioned earlier, the material used to erase pencil marks in the early days was natural rubber. Natural rubber is thermosetting and exhibits poor processing and shaping properties. Some people used PVC (polyvinyl chloride) plus plasticizer and calcium carbonate powder to make eraser blocks with excellent erasability. How to replace such a good and cheap product? Perhaps there was a chance from environmental issues. Another competitive option was the processability. So the clear goal was a non-PVC eraser that can be injection molded. Calcium carbonate powder plus rubber can make pencil marks erasable, but soft PVC is not allowed to be used, so the only option was thermoplastic elastomer (TPE). 

TPU possesses a wide range of properties, but it was too expensive to be competitive. Ionomers, TPO, TPV, TPEE and TPAE were not very suitable either, so the only option left was styrenic block copolymers.

At that time, an interesting toy appeared on the market: the magic octopus. This was a toy made by mixing high molecular weight SEBS powder and white wax oil, followed by heating to form a solution, and then pouring the solution into a mold. This material exhibited excellent stickiness and slow recovery after deformation. It behaved like unvulcanized natural rubber. Therefore, Link Upon developed non-PVC erasers that can be injection molded based on this system. The erasable properties of pencil mark could be adjusted by the ratio of SEBS, white wax oil and calcium carbonate. This would be a multivariable function. With so many variables, I intuitively feel that it might be more efficient to adopt an experimental planning approach. 

Before I completed the design of the experimental plan method, Mr. Lin excitedly showed me the samples he developed:

 "I have tried out a good formula. But I almost burned down my kitchen on Sunday."

"What’s the matter?"

"I cooked too many pots. I was a little tired that day, so I took a nap and it started to burn."

When I was in the university, it was always jokingly said that someone has cooked a pot every time who did a chemistry experiment. 
Taking the compounding of SEBS and white oil as an example, the equipments such as rollers, mixers, beakers, flasks and blenders used in polymer laboratories are indeed not as convenient as burning a stainless steel pan on a gas stove, but there is a risk of ignition. Many small business owners at that time were in a very difficult situation, and Mr. Lin was a typical example.

I couldn't help but ask, "How many pots did you cook?"

"I didn't know? Anyway, I just tried to find a formula with excellent erasability and molding properties. If it was not good, I just cooked the ingredients again." 

So, the first generation prototype came out. The cooked compound was first cut into eraser blocks by hand, and then introduced to customers with the environmental protection issues. The result was that no one was willing to pay! Now that the formula came out, the point was just to find a way to sell it. Mr. Lin was the typical businessman. The problem was that it was more expensive. 

After searching for a while, we found that the eraser tips of the pencil seemed to be a target. 

First, it was difficult and not cost-effective to manufacture eraser tips using soft PVC.  Second, the erasability of the traditional rubber tips made of vulcanized natural rubber was poor.

Using injection molding seemed to be able to reduce the cost of the eraser tips. So Link Upon started making molds and then mass-produced non-PVC eraser tips.  Sure enough, low-price is king. Coupled with excellent erasable properties, Link Upon expanded the non-PVC eraser tip business to all over the world. Initially, the eraser tip sizes of pencils from different manufacturers varied to some extent. 

The devil is in the details! 
You can't embrace all manufacturers, but you can get most manufacturers to embrace your products. Link Upon also developed aluminum ferrules for assembling pencils, the size of which was suitable for the eraser tips produced by Link Upon. 

When manufacturers used Link Upon's eraser tips and aluminum ferrules, there were little problems during assembly. Therefore, the market was easier to expand. In the 1990s, Link Upon's market share in the eraser tip market reached approximately 80%. 

Eraser tips

In the eraser market, the most widely used product was the block-type eraser. Of course, it is also possible to make eraser blocks using the original eraser tip formula. The problem was that one of the main raw materials was SEBS, which was too expensive. In the 1990s, some rubber companies in Taiwan began to produce SBS. Its price was quite competitive. Link Upon began to use SBS to replace part of SEBS in the development of eraser blocks. Soon, the erasability and processability were solved. However, the new formula brought new problems: deterioration and discoloration. Undoubtedly, the unsaturated double bonds of SBS are the main cause of deterioration and discoloration. How to solve it? Adding antioxidants and stabilizers might provide a solution. Antioxidants were relatively cheap, so more quantity used was acceptable. Therefore, the main evaluation point was the effect of the stabilizer content on the stability of the eraser block.

Mr. Lin said, "Dr. Tsai, how do you evaluate stability?"

“Accelerated aging is commonly used in laboratories. Thermal stability can be assessed by placing the sample in a high temperature oven for a period of time and then measuring its properties. By irradiating the sample with an ultraviolet lamp for a period of time and observing the color change or measuring its spectrum, the light stability can be roughly evaluated.”

“Is the result of this simulation accurate?”

“It's hard to say. But it's not as accurate as the actual evaluation.”

“Is sunbathing effective?”

“In fact, sunbathing is closer to the actual evaluation.”

So, Mr. Lin quickly prepared eraser blocks containing different formulas and placed them outside the office window to bask in the sun.

“How long do you think an eraser block will last?”

“The distributors said that the stocking period should not be over two years, and common consumers will not complain after three years of buying the eraser blocks.” 

“The eraser blocks are majorly placed in an indoor environment. So, if they are exposed to the sunlight outside the window, similar to be accelerating aging, and those can persist one or two years are considered to be acceptable.”

After one or two years of observation, the results were satisfactory. Link Upon also successfully introduced its own eraser block products.

 

Eraser blocks

With the non-PVC eraser formula that can be injection molded, Link Upon also actively developed some shaped erasers. At that time, some processing plants were often proud of the number of molds they had made. Mr. Lin: "Although we don't have too many molds, our components have different colors, and the number of products we can assemble is also very large!" So, Link Upon gradually developed various series of shaped erasers. The ones that left a deep impression in my mind include the dinosaur series, the wild animal series, football series, baseball series, puzzle series, fruit and vegetable series, etc. In a trance, more than thirty years have already passed.

During that period, Mr. Lin also mentioned that extrusion uses more material than injection molding. In other words, the production capacity could be greater. Some eraser blocks had been made by cutting after extrusion. If multiple color extrusion was used, and then cut, special erasers could be made. Typical products are shown on the left in the picture below.Shaped erasers

 

[Grip Materials and Grips] 

One day, Mr. Lin had an idea: “Link Upon uses foreign materials including compounded materials and agent materials, but it seems that we don’t have our own (registered trademark) materials!”

“Developing new materials is a big project!”

“Dr. Tsai, don't misunderstand. We won’t develop new resins. New materials obtained from new processes such as Santoprene are what we can imitate.” 

“Link Upon owns many formulas. Maybe we can find a special application product, improve the formulation, then register a trademark, and promote it to become our own material.”

“This is feasible. Many stationery factories have reported that the existing pen grips show some shortcomings. The size of rubber products often runs away, and the touch feeling is not so good. Silicone products can be transparent and exhibit better elasticity, but it is quite expensive.”

“Let’s start from the transparent formulations. In fact, the touch feeling of some our eraser materials is similar to that of some pen grips. If calcium carbonate is not used, there is a chance to adjust the formulations to be transparent.”

Link Upon engaged in the research and development of its? own materials. One day, Mr. Lin said, “Dr. Tsai, I found an interesting phenomenon. After kneading, our material becomes more elastic! Do you know what's going on?”

“This is an interesting phenomenon. Kneading first appeared in the processing of natural rubber. At first, the Banbury mixer was recognized as more effective. During the kneading of natural rubber blocks, in addition to mixing various additives, the shear force also reduces the degree of polymerization of natural rubber molecules, and this favors the subsequent mixing and molding. However, there was a completely different case. Formerly, someone used PVC (polyvinyl chloride) to extrude corrugated boards. Corrugated boards required stiffness, that is, rigidity. He heard that DOP (dioctyl phthalate) is a plasticizer that would greatly reduce the hardness of PVC, so he greatly reduced the amount of DOP. As a result, the corrugated boards he extruded collapsed after a short period of use. The reason was that PVC still needs some DOP to effectively gelatinize the PVC powder. During processing, DOP could effectively penetrate into the PVC powder under the action of shear force, so that the extruded material showed reasonable physical properties.”

“So kneading could allow the white oil to effectively penetrate into SEBS?”

“It should be. In fact, this also involves another concept: gel. In some gels, the polymer chains are effectively entangled, making their viscosity to be infinite, and thus forming elasticity. SEBS can be dissolved in oil by heating, but it is already entangled. Just dissolving by heating, the SEBS molecular chains may not be fully expanded. If it is kneaded while heating, the white oil has a chance to effectively allow the molecular chains to fully expand to form a gel.”

“So, the ingredients must be precisely controlled to prevent the molecular chains from breaking, but to allow them to be effectively expanded.”

“That's right! This requires hard-working.”

“The greatest advantage of Link Upon is willing to work hard.”

As a result, a series of TPE formula materials with a wide range of properties were developed, and the registered trademark was LINK-PLUS®. The materials ranged from transparent to various colors, from super soft (Shore A 15) to normal hardness such as Shore A 80, and a variety of touch feelings were included. Of course, most customers paid attention to the products rather than the materials. Link Upon also once developed elastomer products and parts such as mats and washers. The most successful one was the grips.

Grips

This article is dedicated to my good friend Mr. Ah-Hing Lin
June 24, 2025