Tacky-Free Polyurethanes Pressure-Sensitive Adhesives by Molecular-Weight and HDI Trimer Design

Area of Science:

• Polymer Chemistry
• Materials Science
• Adhesive Technology

Background:

• Polyurethane pressure-sensitive adhesives (PU-PSAs) are crucial in various applications.
• Controlling adhesive properties like tack, cohesion, and removability is essential for performance.
• Existing PU-PSAs may require optimization for specific adhesion and cohesion requirements.

Purpose of the Study:

• To develop novel PU-PSAs with optimized tack, cohesion, and removability.
• To investigate the impact of methylene diisocyanate, poly(ethylene glycol) (PEG), and 1,4-butanediol chain extender ratios on PU-PSA properties.
• To determine the influence of molecular weight and crosslinking density on adhesive performance.

Main Methods:

• Synthesis of PU-PSAs using methylene diisocyanate, PEG, and 1,4-butanediol with varying HDI/HDI trimer ratios.
• Characterization of adhesive properties including tack, cohesion, and 180-peel strength.
• Analysis of molecular weight and crosslinking density effects on adhesion.

Main Results:

• Developed PU-PSAs exhibited satisfactory tack, cohesion, and removability.
• Adhesive properties were significantly influenced by the HDI/HDI trimer ratio and crosslinking agent composition.
• A molecular weight range of 1000 < Mn < 3000 showed a limiting effect on pressure-sensitive adhesion.
• Crosslinking density critically affected cohesion, adhesion, and tack.

Conclusions:

• A formulation with 50 wt.% 600PEG and 50 wt.% crosslinking agent, and an HDI/HDI trimer ratio of 1.0, achieved an optimal balance of adhesion and cohesion.
• This optimal formulation demonstrated sufficient tack, high 180-peel strength, and good cohesion.
• The study provides insights into tailoring PU-PSA properties through controlled synthesis and formulation.