TPE包胶注塑(二次注塑)全流程?料和工艺,是一张卷子

应用领域 发布时间: 2026-09-14 1831 阅读

The overmolded parts come apart as soon as you peel them, and the second molding is all wasted. The material and process are two sides of the same coin, and both need to be addressed.

It peels off in layers as soon as you tear it; the substrate and material were not properly matched.

TPE overmolding injection (secondary injection molding), the material and process are on one sheet: substrate, material, parameters. Here’s the conclusion first: for overmolding delamination, check the substrate first — the substrate is the foundation for overmolding.

The biggest pitfalls in TPE overmolding: material and process, it's like a test paper. Even if the material is right, if the process is wrong, delamination still occurs — material and process are the two test papers of overmolding.

TPE coating is a craft: delamination and cracking are problems. Only with the right process can the yield be stable—it's a craft, don't skip steps.

The substrate determines whether it sticks or not, so why look at the framework first

TPE coating depends on the polarity of the substrate: PP uses SEBS base, PA uses TPEE. If the substrate doesn't match, delamination is inevitable—the substrate is the foundation of the coating.

The substrate surface must be treated: cleaned, dust removed, and degreased. If the substrate is not clean, bonding is pointless — substrate cleaning is the first step in coating.

The coating temperature should match: material temperature 180-210℃. Mold temperature 40-60℃ — temperature is the bonding line of the coating.

Material preparation, injection molding, cooling—what is the process flow?

Material preparation: Pre-form the substrate and perform surface treatment. If the substrate is not clean, it will delaminate—material preparation is the starting point for encapsulation.

Injection molding: first injection molding the substrate, then second injection molding to overmold. The temperatures for the two stages are adjusted separately — injection molding is the core of overmolding.

Cooling: Maintain pressure and cool in place. Insufficient cooling can cause sticking to the mold—cooling is the finishing step of encapsulation.

SEBS vs TPEE, which one to choose for overmolding

SubstrateEncapsulation materialTemperature
PPSEBS-based180-200℃
ABSSEBS-based190-210℃
PATPEE210-230℃
PCTPU200-220℃

Table reading: The substrate matches the system, and the temperature follows—PP uses an SEBS base, PA uses TPEE.

Match the base material, and the coating will not peel off.

If it can't be peeled off or delaminated, first check these four items

ProjectRequirementJudgment
SubstrateCleanMeet the standard
Material temperatureAccording to the systemMeet the standard
Mold temperatureAccording to the systemMeet the standard
Peel strengthActual measurementMeet the standard

Table reading method: Match the substrate, temperature, and peel strength item by item; even if the materials match, if the process is wrong, delamination still occurs—whether the encapsulation is good or not, both ends need to answer the question.

Material and craftsmanship are the two aspects of encapsulation.

Delamination is blamed on the material; no one checked the surface of the substrate.

Pitfall 1: Only changing the material. As soon as delamination occurs, they return the soft glue, but the temperature and substrate aren't matched—when delamination happens during secondary injection molding, first lay out the process and the materials on the table.

Pitfall 2: The substrate is not clean. Delamination — substrate cleaning is a must.

Pitfall Three: Random temperature adjustments. Delamination — adjust the temperature according to the system.

Substrate, peeling, process—ask clearly before coating

Three questions: what substrate, what system, how much peel strength. One check: actual measurement of mold peel—three questions and one check, supplier details clear.

Substrate verification must come first: first check the substrate polarity and surface treatment, then the material temperature and cooling. First check the substrate, then discuss yield — the substrate is the foundation of encapsulation.

Make sample keeping a habit: keep a sample for each batch, and retest the bonding by batch. When changing materials between batches, compare first before scaling up—the batch is stable, and customer complaints are few.

Delamination, Flash, Missing Glue: A Comparison Table of Faults

PhenomenonReasonCountermeasure
DelaminationUnclean substrateClean the substrate
DelaminationLow temperatureTemperature rise
CrackingMaterial mismatchMaterial change
shrinkLow hold pressureIncrease pressure
Silver streakMoistAdd roasting material

Do not mass-produce if the coating peeling strength is below 0.5 kN/m, it will start peeling after two weeks. For PP substrate SEBS system, the typical value is 1.0-2.0 kN/m; coating thickness should be 0.8-1.5 mm, too thin it won't stick well, too thick is wasteful.

Don't blame the glue first for delamination of the coated rubber—if the substrate polarity doesn't match, no amount of glue will help. Moisture is an accomplice in delamination, so the coating material should be properly baked; the material and the process are part of the same sheet, and both ends should be checked together.

Three steps for jacketed material acceptance: first measure peel strength, then bend 5,000 times, and finally pass wet and dry thermal cycles. The jacketed material temperature is adjusted according to the system, and the substrate batch is locked; when changing materials, first run a small batch trial production to pass the three checks.

Overmolding is 'soft skin over hard bone' — the substrate is the bone, the soft rubber is the skin, and the peel strength is the adhesion between skin and bone. When the soft rubber peels off around the whole shell, it is mostly due to insufficient peel strength; if the mold temperature is insufficient, the bonding is inferior.

Peeling force increased from 0.3 to 1.8 kN/m, no delamination after 5000 bends. When changing the batch of the substrate, compare first before scaling up; encapsulation parameters are recorded and archived for traceable reference.

Overmolding is soft material covering a hard core. First, check if it can stick; choose the TPE system according to the polarity of the substrate. For PP substrates with SEBS base, the typical peel strength is 1.0-2.0 kN/m; for ABS with SBS base. The substrate surface must be clean, and mold temperature affects peeling. Do not mass-produce if the peel strength is below 0.5 kN/m.

For secondary injection molding, first produce three samples for testing: peel strength report, bending cycles, and temperature resistance. Without any one of them, mass production will not be considered.

The overmolded parts can withstand bending five thousand times without delaminating before being considered stable; when changing materials, first run a small batch of 500 pieces to pass the three tests of appearance, feel, and durability, and only discuss mass production after the substrate is properly preheated.

Overmolding finishing acceptance: Peel strength, bending, and temperature resistance are checked with each batch; no production will be discussed if any sample is missing.

The peel strength of samples from each batch is 1.0-2.0 kN/m, and there is no delamination after 5,000 bending cycles; for batch material changes, first pass 500 pieces of a small batch through three inspections before discussing large-scale production.

When it comes to choosing the coating, it ultimately comes down to asking about the substrate polarity, peel strength, and bending lifespan all at once.

Base material system, peeling force 1.0-2.0 kN/m, does not delaminate after five thousand bends; first make three samples, all three must be complete, if one is missing, mass production will not be discussed.

Whether the coating sticks firmly or not can be known after bending it five thousand times once. If it peels off, it’s not up to standard, and the peel strength data follows each batch; only when the substrate is properly preheated can we talk about mass production.

Cologne Customer Case: Bulk delamination of overmolding, replicated according to production benchmarks

A plastic injection factory in Foshan experienced batch delamination of TPE overmolded parts, resulting in a persistently high rework rate. Cologne assisted on-site with production debugging until the yield stabilized, delamination was eliminated, and the touch and rebound matched the reference samples. Through production debugging, delamination was locked out before mass production—overmolding issues should first examine the substrate, then the parameters.

Summary

For the TPE overmolding injection process, first check the substrate, then adjust the temperature. Material and process form a single system, and the substrate is the foundation.

What we deliver is more than just a bag of material.

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