What is TPE Overmolding?

TPE  overmolding generally refers to the injection molding process where TPE materials are molded onto a second materials, typically a rigid plastic such as PP, PS, ABS, PC and PA. It can increase comfort touch, anti slip and impact resistance performance of finished products.

Two injection molding processes commonly used for the production of overmolded products are insert molding and multi-shot injection molding. Insert molding is the most widely used process where a pre-molded insert is placed into a mold and TPE is shot directly over it. Its advantage is that it uses conventional single shot injection molding machines for TPE overmolding, saving the costs of purchasing new machinery.

Multi-shot injection molding, also known as multiple material or two-shot molding, requires a more advanced injection molding machine that is equipped with two or more barrels, allowing two or more materials to be shot into the same mold during the same molding cycle. Manufacturers will select multi-shot injection molding to reduce cycle times, achieve parts with superior quality and reduce labor costs.

Notices for TPE overmolding:

  1. Take the compatibility of TPE and rigid plastic parts into consideration;
  2. Avoid sharp corners in the product design to improve the adhesion of TPE to rigid plastic parts;
  3. Use appropriateair venting to prevent air from in the mold cavities;
  4. Keep the proportionof TPE’s flow length and product thickness below 150:1;
  5. Achieve balance between TPE’s thickness and expected touch;
  6. Control the temperature of molten TPE to ensureadhesive effect;
  7. Perform special processing for smooth surfaceto increase the contact surface between TPE and rigid plastic parts, thereby strengthening adhesive effect;
  8. Use TPEwith excellent flowability, because the thickness and dimension proportion of TPE overmolding is very small and TPE is usually required to flow through long paths and thin-walled areas to fill molds;
  9. Use good adhesives.

 

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What is the White Substance on the Surface of TPE/TPR Products?

The white substance on the surface of TPE/TPR products is small molecules caused by migration and precipitation.

Sometimes, certain low molecular weight additives, such as brighteners, releasing agents, may be added into the modification process of TPE/TPR products. Owing to the poor compatibility with substrates, these additives are generally added by 2~3‰. If excessive additives are added, the migration of small molecules will occur as time goes by.

The temperature is high while blending and modifying TPE/TPR. Hence, the additives show relatively even dispersed state (unstable) in the blending system. As time goes by, the oversaturated additives will migrate to the surface of TPE/TPR products owing to the low solubility of low molecular weight additives in the blending system. In daily life, we may find white substance exists on the surface of TPE/TPR finished products after a period of time, which can be rubbed off by hand. This is the migration of excessive low molecular weight additives.

Acidification, frosting, whitening and other phenomena commonly found in the production of TPE/TPR products are all caused by the migration of constituents that have poor compatibility in the blending system.

As a result, the amount of added additives with low solubility should be strictly controlled in the modification process, to prevent TPE/TPR products from consequent migration. In the actual production process, the migration of additives also occur in other modified engineering plastics and rubber products in addition to TPE/TPR products.

 

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How to Deal with the Sticky Texture of TPE/TPR Products?

Problem Description

Some products made from TPE/TPR granules have sticky texture.

Problem Analysis

TPE/TPR granules are thermoplastic elastomers produced by compounding SEBS and SBS (worked as substrate), compounding oil, reinforced resins, compatiblizing agents, functional additives, and fillers.

  1. Amount of added compounding oil

Compounding oil is one of the indispensable constituents of TPE/TPR granules. The addition of compounding oil can improve TPE/TPR’s plasticity, but it also may result in the sticky texture of TPE/TPR products. The hardness of TPE/TPR granules is in the range of Shore A0~100. Generally speaking, the more compounding oil added, the softer TPE/TPR products, and the stickier texture TPE/TPR products will have.

  1. Influence of substrate

In the TPE industry, the compounds using SEBS and SBS as substrate are usually called TPE and TPR respectively. SEBS is the hydrogenated SBS and superior to SBS in oil absorbency, namely for the same mass numbers of SEBS and SBS, SEBS can absorb more compounding oil, or the surface of SEBS-based TPE products are not easy to be sticky compared with that of SBS-based TPR products. SBS-based TPR granules have hardness below Shore A50~60. They are prone to cake in summer due to the high temperature, and the products made from TPR granules have relatively stickier texture. SEBS-based TPE products rarely have sticky texture except those made from super soft materials with hardness below Shore A15.

Recommended Solution

Based on the above analysis, the products made from SBS-based TPR granules are easy to have sticky texture, especially at high temperature. Hence, it is recommended that manufacturers use SEBS-based TPE granules for product production to deal with the sticky texture of TPR products.

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How to Improve TPE/TPR Materials’ Toughness, Resilience, Abrasion Resistance and Tensile Properties?

As thermoplastic elastomers, TPE/TPR materials are not as good as vulcanized rubber in toughness, abrasion resistance, and resilience. TPE/TPR materials are therefore usually applied in non-mechanical and engineering sectors like consumer goods industry.

However, consumer goods industry sometimes has different requirements for toughness, abrasion resistance and resilience of TPE/TPR materials. This depends on the demands for product quality from end users, or end user market determines the level of product quality and the quality of selected raw materials.

Generally, TPE/TPR suppliers with experience in the R&D and production of TPE/TPR materials can offer customers specific TPE/TPR grades on the basis of their product requirements, such as excellent toughness, resilience, and abrasion resistance, to satisfy customers’ cost-effectiveness demands. To do this, the formulas of TPE/TPR materials can be adjusted, although it is very difficult to develop the suitable TPE/TPR materials that satisfy customers’ strict requirements.

The improvement of TPE/TPR materials’ poor toughness, tensile properties, abrasion resistance, and resilience can be considered from the following aspects:

  1. Too many fillers are added in the production of TPR/TPRmaterials. This will reduce tensile strength, elongation and other tensile properties of TPR/TPR materials, and also have a negative effect on its resilience and abrasion resistance.
  2. The substrates have low molecular weight or are non-hydrogenated. Low molecular weight substrate-basedTPE/TPR materials have relatively poor resilience, tensile properties, as well as abrasion resistance. Non-hydrogenated substrate-based TPE/TPR materials have relatively poor tensile properties.
  3. There is a problem with TPE/TPRmaterials’ plasticization in extrusion or injection molding. The poor plasticization will lead to adverse effect on the above-mentioned physical properties.
  4. The compatibility ofall ingredients in TPE/TPR formula also needs to be considered. The poor compatibility can’t result in good physical properties.
  5. The addition of functional additivescan improve TPE/TPR materials’ abrasion resistance.

 

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Thermoplastic elastomers rubber (TPE) styrene isoprene styrene block copolymer SIS rubber polymer 1505

DESCRIPTION

Thermoplastic elastomer SIS(styrene isoprene styrene) polymer 1505 has good anti-aging properties, good initial viscosity, excellent melt processing performance, good elastic recovery, and small permanent deformation .

SIS rubber polymer 1501

APPLICATION

Adhesive /Asphalt modification /Plastic modification

SIS 1505+_meitu_10

CHEMICAL PROPERTIES

Structure: L

Styrene content  (%) : 15

Diblock content  (%):  <1

Solution Viscosity(25℃,25%)  (≤mPa.s):  ≤2500

MFI  (g/10min):  8-16

Shore A  (/) : 30-40

Tensile strength  (Mpa) : ≥7

Elongation  (≥%) : ≥1000

 

FORMULA

PSA (Parts by mass)

SIS(1505): 30

Naphthenic Oil: 20

Tackifying Resinl: 25

Other Additives:  Right amount

 

ALTERNATIVE GRADES

Taipol 2311

Vector 4111

Kraton 1114P

 

MANUFACTURE

Sunion

 

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Thermoplastic elastomers rubber (TPE) styrene isoprene styrene block copolymer SIS rubber polymer 1501

BEC materials  SIS 1501 , SIS rubber 1501, SIS polymer 1501 , styrene isoprene styrene 1501

DESCRIPTION 
Thermoplastic elastomer SIS(styrene isoprene styrene) polymer 1501 possesses good thermal stability and melt processing performance, good elastic recovery,and small permanent deformation .

SIS 1501

APPLICATION 

Adhesive /Asphalt modification /Plastic modification

SIS 1501+

CHEMICAL PROPERTIES
Structure: L
Styrene content (%) : 15
Diblock content (%) : <1
Solution Viscosity(25℃,25%) (≤mPa.s) : ≤2500
Shore A (/) : 30-40
Tensile strength (Mpa) : ≥7
MFI (g/10min) : 8-16
Elongation (≥%) : ≥1000

FORMULA
PSA (Parts by mass)
SIS(1501): 30
Naphthenic Oil: 20
Tackifying Resinl: 25
Other Additives: Right amount

ALTERNATIVE GRADES
Taipol 2311
Taipol 4211
Kraton 1114P
Vector 4111
Kraton 1164P

MANUFACTURE
Sunion

 

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SAM Products of SINOPEC Baling: New Solution for Asphalt Modification

New Solution for Asphalt Modification

SAM products manufactured by SINOPEC Baling Company, including YH1601, YH1602, and YH1603, provide new solution for asphalt modification, especially in self-adhering waterproofing membrane and asphalt pavement, with excellent performances.

SAM is a new product type of styrenic block copolymer (SBC) family. It has the combined properties of SBS and SIS, and its price is between that of SBS and SIS. This makes it very cost-effective. With special polymer structure, SAM is able to reduce fish eye and other defects of modified asphalt, and improve the flexibility of modified asphalt at low temperature and the ability of being stored at high temperature for a long period of time. Furthermore, in the manufacture of self-adhering waterproofing membrane, SAM can be directly applied in the self-adhering layer instead of the conventional method that requires to mix SBS, SIS and rubber powder together to make the waterproofing self-adhering layer. This can greatly enhance production efficiency and save costs.

In addition, SAM’s special structure makes it superior to SBS and SIS in certain applications. As a new type of thermoplastic elastomer, SAM is expected to lead the asphalt modification sector.

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