What is Overmolding ? Overmolding used for

What is overmolding?

overmolding  Introduction

• Overmolding is one of the methods of plastic molding

• Plastic profiles as raw materials, through the role of heat and force, to become the desired shape of products.

• To meet the special needs of many plastic products,

• Many plastic products are not made of plastic raw material, additional plastic products, the appearance and process requirements,

• Need to use two or more two kinds of plastic raw materials in multiple injection molding methods.

Overmolding Features

1) The main part of the hard plastic mold design calculations shrink Overmolding technology is known for creating "soft surfaces"

2) overmolding usually has two separate sets of mold

3) After the soft mold part of the mold with the main body of a hard to avoid a small number of empty spaces, 

and plastic parts use the main hard plastic glue can not have the virtual TPE over-molding process recipe and features With the rapid development of TPE elastomer industry in recent years, the application of TPE

4) overmolding is also more and more mature Many hard plastic parts,

 Through the introduction of elastomer TPE soft material, enhance the product's touch, grip, aesthetics, and other features.

TPE overmolding process recipe and features

• TPE overmolding, the key point is to make TPE and coated material PP, ABS, PC, PA, etc. can be a good coating adhesion.

• TPE and the coated material to make a good bond, according to the principle of chemical similarity and compatibility, 

The TPE and the coated material should have close characteristics, making the TPE and the material can be coated with molecular chain level fusion. 

Therefore, the type of coating material is decided TPE formula, overmolding directly affects the adhesion of TPE and whether the coated material is good or bad.

Overmolding Advantage

Overmolding not only makes the device surface full of softness but also can increase product functionality and added value.

 TPE formula

Different coated materials, such as PP, PC, ABS, PA, etc., require different TPE formulations and models.

 PP Material

• PP overmolding is a very weak plastic, very close to the TPE polarity of SEBS. Therefore, overmolding PP, direct use of the most conventional TPE formula can be,

• No need to add an additional polarity modifier. Although overmolding PP TPE is the most common category, the temperature is also very important,

• Must use sufficient injection temperature to ensure the flow of TPE and quickly rated on the PP surface, the injection temperature should be able to ensure the rapid formation of a layer of fusion in the PP plastic surface layer,

Which will help TPE and PP adhesion, Do not let the PP plastic parts in the injection molding heat distortion.

• Recommended overmolding temperature of 170 220 °C. Note: PP overmolding, SBS is not recommended as a TPE-modified binder.

ABS, PC Material

ABS, PC overmolding, ABS, PC for the weak to medium polarity plastic, and JPE there is a certain polarity difference. 

By adding a modifier (TPU) to the formulation, the polarity of the TPE can be improved, improving the adhesion of TPC to ABS and PC. In addition to the second injection temperature, 

The proposed 180 230 C Specific adjustments uncording to the actual processing conditions.

PBT, PET Material

PBT, PET semi-crystalline plastic, polar and ABS, PC similar. PBI melting point of 220 C. 

PET melting point is to have a higher melt as high as 260 CTPE need temperature.

 Therefore, TPE overmolding PBT and PET the required overmolding temperature higher than the ABS, and PC.

Bonding difficult PA6, PA66 Material PA6

PA66 is a semi-crystalline strong polar plastic, that needs high temperature and energy to form the weld layer on the hard plastic surface. 

PA6 melting point 240 C. PASS melting point 260 C To form a firm bond requires TPE with a higher melt temperature. General TPC overmolding PAG.

 Temperature 230-250 C. TPE overmolding PA66, needs 240 270 C. In addition PAG. PA66 is easy to absorb water,

 These are unfavorable factors for the coating and bonding of POM Material.

 POM Overmolding

POM although the melting point is not high, is only 180 C.

 However, due to its high crystallinity, the weld layer needs to be formed on the clad surface, which requires high energy. 

At the same time, the self-lubricating property of the POM is not conducive to the rapid coating of the TPE material on the surface of the POM hard plastic part.

 Therefore, POM coating has some difficulties.