Microbial Challenges for Long-lived Adhesive and Sealant...

Microbial Challenges for Long-lived

Adhesive and Sealant Formulations

Don Satchell, Ph.D.

Technical Director

Situ Biosciences LLC

Wheeling, IL

1Microbial Challenges for Long-Lived Adhesive & Sealant Formulations – ASC 2016

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Topics

• Adhesive and Sealant

Application Challenges

• Microbes &

Environmental conditions

• Antimicrobials,

Formulations, Testing

and Performance

Microbial Challenges for Long-Lived Adhesive & Sealant Formulations – ASC 2016

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Challenges for Adhesives & Sealants

By their nature, adhesive and sealants are commonly used in conditions

favoring microbial growth.

• High humidity and exposure to moisture

o Bathrooms, Windows, Flooring, Siding Stagnant high humidity

Environments,

• Environmental exposure

• Sunlight (UV in particular)

• Water/rain

• Freeze and thaw and dew point cycles


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Microbes Perspectives & Environmental Conditions

Nutrients:

• Environmental contaminants (organics in dust, etc.)

• Organics in the PRODUCT (olefins, urethanes, latex,

plasticizers, mineral slurries, surfactants…etc.


Water alone is not sufficient for microbial growth

Environmental conditions and nutrients must be present allow

for microbial proliferation

Generally - Standard environmental conditions that allow for

microbial growth are the same conditions we cohabitate

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Antimicrobials and Product Formulations

Antimicrobials used in adhesive and sealant formulations can perform

differently depending on:

How the additive is incorporated into the product formulation

The intended use instructions for the product.

Product Testing can vary for a variety of reasons:

• Layers of material

• Curing time

• Test substrate

• Volume

• Nutrient Load

• Mixing

• Durability Testing prior to resistance testing


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Microbial Testing Methods (Fungal):An example: ASTM G21: a Standard Method for Determining

Resistance of Synthetic Materials to Fungi

Strengths

• Standard inocula that can accommodate a range of fungal types

• (A. niger, P. funiculosum, C. globosum, T. virens and A.

pullulans)

• Standard replicates allow a comprehensive level of analysis

• Historical perspective on product quality/performance

Challenges

• Representation to a ‘standard’ condition


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Fungal Resistance Testing

On the rating scale of 0-4 (4 being the worst)

this sample received a score of 2 with

approximately 20% coverage by fungal

mycelia and spore; all growth was along the

perimeter edge.


This sample also received a score of

2 with <30% coverage by mycelia

and spore

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Assessment of Antimicrobials in Adhesives


Score of 1; <10% coverage by

mycelia and sporeScore of 4; >90% coverage by mycelia

and spore

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Bacterial Resistance Testing

ASTM E1428: Standard Method for Evaluating Performance of

Antimicrobials Against Staining by Streptomyce Species


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Properly Formulated Materials will resist fungal growth


• Low aqueous solubility will provide the best

environmental durability

• pH stability

• Broad spectrum efficacy

• Chemical compatibility with the substrate

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Common Antimicrobial Additives for Adhesives

Dichloropheynoxy-phenol -

Triclosan

Diiodomethyl- p - tolysulfone -

Amical

Quaternary ammonium trimethoxysilane -

Quatsilane

Zinc pyrithione - Zinc Omadine

Isothiazolinones


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ConclusionsMicrobial control strategies for product

environments

• Manage the environment to minimize

microbial challenges

• Manage the formulation to minimize

microbial impact

• Combination strategies work best,

but are potentially costly and

complicated

• Managing microbes requires

application and formulation insight


Microbial Challenges for Long-lived Adhesive and Sealant...

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