TPP-K

1. Product Overview

Tetraphenylphosphonium Tetraphenylborate (TPP-K) is a latent curing accelerator that remains inert at room temperature and releases active phosphonium cations upon heating to catalyze epoxy ring-opening reactions.

Its molecular structure consists of two highly symmetrical tetraphenyl groups. A central phosphorus atom (P) is bonded to four phenyl rings, forming a positively charged tetraphenylphosphonium cation ([P(C₆H₅)₄]⁺). A central boron atom (B) is likewise bonded to four phenyl rings, forming a negatively charged tetraphenylborate anion ([B(C₆H₅)₄]⁻). These two ions combine through electrostatic attraction to form a salt with a bulky and rigid molecular structure.

2. Basic Information and Physical Properties

Item	Description
CAS No.	15525-15-2
Chinese Name	Tetraphenylphosphonium Tetraphenylborate
English Name	Tetraphenylphosphonium Tetraphenylborate
Composition	An ion-pair salt consisting of tetraphenylphosphonium cations ((C₆H₅)₄P⁺) and tetraphenylborate anions ((C₆H₅)₄B⁻)
Molecular Formula
Molecular Weight	658.62
Appearance	White to off-white powder or crystals
Melting Point	N/A
Solubility	Insoluble in water and ethanol; poorly soluble in common polar solvents; readily soluble in organic solvents such as dichloromethane, toluene, chlorobenzene, and DMF
Storage Conditions	Store at room temperature in a dry environment under an inert atmosphere. The product is light-sensitive and should be kept sealed and protected from light.

3. Product Features and Recommended Applications

Product Features

Bulky Hydrophobic Ionic Structure: Although TPP-K has an ionic structure, both its cation and anion are surrounded by multiple hydrophobic phenyl rings, making it a bulky hydrophobic organic salt.
Curing Mechanism: Upon heating, the ion pair dissociates, releasing free tetraphenylphosphonium cations that catalyze epoxy ring-opening reactions. The tetraphenylborate anion is highly stable and does not generate small-molecule volatile by-products.
Long-Term Thermal Latency: Functions as a high-temperature, long-lasting latent curing accelerator.

Recommended Applications

Epoxy Curing Accelerator / Catalyst

TPP-K is an important component of latent curing accelerator systems used in high-end semiconductor encapsulation molding compounds (EMC), high-frequency copper-clad laminates, and PCB solder mask inks.

4. Advantages, Disadvantages, and Precautions

Advantages

Excellent thermal stability and a very long storage life at room temperature.
No readily reactive carbonyl or quinone structures.
Good resistance to acids, alkalis, and water vapor.
Contributes to excellent moisture-heat resistance, hydrolysis resistance, and aging resistance in formulated systems.

Disadvantages

Relatively low curing reactivity.
Requires higher curing temperatures and/or longer holding times to achieve the desired curing performance.

Precautions

Chemical Compatibility: Tetraphenylborate anions may decompose under strongly acidic or oxidative conditions. Avoid combining TPP-K with strongly acidic formulation components.
Light Protection: Store away from light to prevent discoloration that may affect product color specifications.