Two Shot Mould Bonded Test Bar: IBA qualification window

A two-shot test bar that peels in the lab is a misleading pass. The bar bonds a rigid substrate to a TPE; the result depends on the grade and the thermal window. Xiangxi IBA series bridges the pair at the molecular level, dosed at the substrate-matched level (see TDS); peel strength rises several-fold and the bar gives a true bond read, with no primer.

Why the Two Shot Mould Bonded Test Bar gives a false read

• Wrong grade — a generic tie agent is not matched to your substrate/TPE, so the bar peels though the process is right.
• Thermal window miss — second shot too hot or cold; the bar fails at the interface, not the chemistry.
• No primer baseline — without a primer-free alloy the test cannot tell whether the bond is chemical or just mechanical.

Process window to qualify the Two Shot Mould Bonded Test Bar

Xiangxi interfacial bonding alloy (IBA) series

Which IBA grade for Two Shot Mould Bonded Test Bar

• Polyolefin grade (PP carrier) for PP-based bars; matched to the PP/TPE pair in the TDS.
• Engineering plastic grade (PA carrier) for PA/PC/ABS bars; switch the carrier accordingly.
• Elastomer grade (TPU carrier) for TPU/elastomer bars; matched to TPU/TPE.
• Run all three on one shared plaque for a fair grade comparison.

Processing notes for Two Shot Mould Bonded Test Bar

• Select the IBA grade to the bar's substrate pair from the TDS before the trial; do not guess.
• Let the pellet down into the TPE at the substrate-matched loading; no primer step in the cell.
• Lock the thermal window per substrate; the bar peels only outside it, not when the grade is right.
• Side gain: the test bar now reflects chemistry, not just tooling luck.

Results to verify in your own lab

• 90° peel across grades: several-fold higher; cohesive tear in TPE.
• Grade comparison: the matched variant outperforms the generic tie agent.
• Thermal window map: bond holds across the qualified melt range, fails only outside it.
• Reproducibility: repeat bars give consistent peel, confirming a chemical bond.

Frequently asked questions

Which IBA grade do I qualify on a two-shot test bar?

Match the grade to the bar's substrate: polyolefin for PP, engineering plastic for PA/PC/ABS, elastomer for TPU; the TDS lists each pair.

Why does my generic tie agent peel on the bar?

A generic agent is not matched to your substrate/TPE pair; the IBA grade is selected to that pair, so the bar reflects real bond.

How do I separate chemistry from tooling?

Run the matched IBA grade with no primer; if the bar peels only outside the window, the bond is chemical.

Can one bar compare all three grades?

Use one shared plaque with the three variants so the peel comparison is fair; request the TDS for each.

Does the test bar need a primer baseline?

No; the IBA grade is primer-free by design, so the bar shows the chemical bond directly.