Mixed Proportions of Paraloid B-72 and B-48N as Structural Adhesives for Art Conservation: Evaluations of Tensile Strength and Glass Transition Restricted; Files Only

Abstract

This study aims to enhance the understanding of polymer-based adhesive performance in art conservation by focusing on the impact of blending Paraloid B-72 and B-48N polymers to improve resistance to temperature changes and increase strength. In working to restore irreplaceable artifacts, the art conservation field is limited to the use of adhesives that are imperceivable, of appropriate strength, and fully reversible. While conservators have heavily relied on the stable and fully-removable adhesive bonds formed by B-72, its relatively low glass transition temperature Tg leaves adhesive joins susceptible to deformation or failure at hotter temperatures. To address this issue, conservators have incorporated B-48N into blends with B-72 in efforts to raise an adhesive’s Tg and resistance to softening at higher temperatures. However, the extent to which the addition of B-48N affects the performance of an adhesive in terms of its strength and resistance to climate fluctuations remains ill-understood. We fill this gap using ellipsometry to measure the glass transitions of various B-72 and B-48N blends. Further, we evaluate each adhesive’s tensile fracture strength using the Conservation Adhesive Tensile-to-Shear (CATS) tester. The results provide comprehensive profiles of adhesive properties for conservators to refer to when determining a treatment most suitable for an artifact’s expected stresses and location of display. Furthermore, the findings contribute to a deeper understanding of the physics underlying the behavior of polymer blends in the context of art conservation. Most notably, this study finds that tensile fracture strength generally increases with increasing B-48N content with blends with less than 50% B-48N content likely exhibiting similar stability to B-72. While blends with over 50% B-48N concentration exhibit similar strength to neat B-48N, they feature distinct glass transition shapes, broadening the adhesive's glass transition and retaining mechanical properties across a wider temperature range.

Table of Contents

Chapter 1: Introduction

1.1 Motivation

1.1.1 Art Conservation

1.1.2 Polymer Physics' Insight into Art Conservation

1.1.3 Paraloid B-72 and B-48N as Conservation Adhesives

1.2 Goals of Thesis

Chapter 2: Introduction to Polymer Physics

2.1 The Glass Transition

2.1.1 The Glass Transition Temperature and Thermal Expansion

2.1.2 Tensile Fracture Strength

2.2 Polymers in this Study

Chapter 3: Experimental Methods--Ellipsometry

3.1 Ellipsometry Theory

3.1.1 Instrumentation and General Overview

3.1.2 Characterizing the Polarization State of Light

3.1.3 Interaction between Light and Matter

3.1.4 Fundamental Equation of Ellipsometry

3.2 Sample Preparation

3.3 Experimental Procedure

Chapter 4: Experimental Methods--Conservation Adhesive Tensile-to-Shear (CATS) Tester

4.1 Design of CATS Apparatus

4.2 Sample Preparation

4.2.1 Adhesive Preparation

4.2.2 Glass Rod Sample Preparation

4.3 Experimental Procedure

4.3.1 Measurement Procedure: Improvements over Previous Method

4.3.2 Preliminary Testing and Comparison with Previous Results

Chapter 5: Results and Discussion

5.1 Evaluations of Tensile Strength: Results of CATS Testing

5.1.1 Reproducibility of B-72 and B-48N Tensile Strength

5.1.2 Tensile Strength of B-72:B-48N Blends

5.2 Evaluations of Glass Transition: Results from Ellipsometry

5.2.1 A-11 Control: PMMA

5.2.2 Pure B-72 and B-48N

5.2.3 Blends of B-72 and B-48N

5.3 Relating Glass Transition to Adhesive Fracture Strength

Chapter 6: Conclusions

6.1 Summary of Results

6.2 Future Work

References

About this Honors Thesis

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School	Emory College
Department	Physics
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Physics, General
Keyword	Polymer Physics Art Conservation
Committee Chair / Thesis Advisor	Connie B. Roth, Emory University
Committee Members	Eric Weeks, Emory University Renee A. Stein, Emory University

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