​Creating Sustainable Plastic Products with Antimicrobials

Written by the Microban Technical Team

The History of Plastics & Polymers

Synthetic polymer was first invented in 1869 as a substitute to ivory used to make pieces for the game of billiards. Subsequently, synthetic polymers were found to be useful as replacements for a variety of natural substances like tortoiseshell, horn, and linen. Over the last 150 years, synthetic polymers, also known as plastics, have become an important category of materials for human activity.

The word ‘plastic’ originally meant pliable and easily shaped. As a class of compounds, synthetic polymers being strong, lightweight, and flexible became known as plastics. The revolutionary discovery of plastics facilitated the creation of new materials that have been influential in helping people and populations overcome social and economic constraints. Plastics rapidly replaced steel in cars, paper and glass in packaging, and wood in furniture due to their in-expense, safety, and pliability.

In the 1960s, the reputation of plastics became tarnished by environmental threats associated with single-use, disposable plastics that are pervasive in landfills and polluting oceans. However, the demand for plastic products has continued to increase. Plastics facilitate the creation of multi-use products that are generally considered to be more environmentally friendly. They are also less expensive, and more widely available than those made from natural polymers. Simultaneously, reusable plastics are environmentally friendly because their extended use-life reduces the financial and environmental cost of plastic waste.

The Effects of Microbes on Plastic Surfaces

As with all surfaces, plastics are exposed to the environment in which they are located. They are therefore the target of microbial contamination, attachment, survival and growth. Given the right environmental conditions, such as temperature, humidity, moisture, and food source, bacteria and fungi can exist on plastic surfaces. For example, chopping boards, food storage containers, baby highchairs, and coolers can harbor persistently high loads of bacteria. Bacterial populations can increase quickly on plastic surfaces because their cells are simple and can multiply easily. Some microbes can be destructive such as when they cause staining, odors, and/or product degradation.

There are polymers that are particularly susceptible to penetration and attack from microbes. These include polymers that present a food source for microbes. Flexible polyvinyl chloride (PVC) contains high levels of plasticizers, a carbon-rich food source for bacteria and fungus which can render these materials susceptible to microbial attack and degradation.

Plant-sourced plasticizers are more susceptible to attack than synthetic phthalates. As the industry has transitioned from phthalate-based plasticizers to "green" and plant derived sources such as epoxidized soybean oil (ESBO), there are even greater opportunities for microbial attack and hence degradation. When Phifer switched from synthetic phthalates to ESBO as a greener facing substrate, greater failures in fungal testing were observed and the need arose for a more fortified antifungal solution.

Some polymers have open structures wherein their surfaces are highly porous with apertures and cracks. Porous surfaces enhance microbial contamination and harborage, leading to stains and odors and potentially the spread of bacteria. For example, kitchen sponges absorb moisture and are therefore highly attractive to microbes.

Foamed ethylene-vinyl acetate (EVA) used in shoes can be an attractive host for microbes, resulting in persistently smelly shoes such as those used in water sports.

Sealants and paints and similar coatings develop cracks and pits over time, making them porous. The pores may shrink with time and create even more tiny crevices for microbial habitation. A sealant or caulk used in bathroom is a good example. Once fungus has effectively penetrated the cracks, bleaching and cleaning will not eliminate the mildew as it can only clean the surface. The fungus remains viable within the cracks and grows back out after a few weeks.

Being a polymer, polyester textile is a form of plastic. The seams of polyester garments can harbor a high degree of microbes that resist removal even by repeated laundering. Over time, the odorous metabolic by-products can be absorbed into the polyester fiber and lead to persistent odor i.e. "permastink".

Microban antimicrobial technologies are helping to address plastic pollution worldwide.

Enhancing Plastic Sustainability with Antimicrobial Technologies

Product design is now at the forefront of worldwide sustainability initiatives. Life cycle assessments are characterising changes in legislation, prompting manufacturers to reconsider raw materials and supply chain management. Antimicrobials are contributing to sustainable product development by extending the lifespan of plastic articles. Through the inhibition of damaging microbes on a plastic surface, antimicrobials help to prevent premature deterioration, visual discoloration and odours.

As with untreated surfaces, an antimicrobial-treated plastic surface can be contaminated with microbes from the environment. The difference is that the microbes are less likely to attach, survive, and grow on a treated plastic surface because antimicrobials create unsuitable conditions for the microbes. The result is a plastic product that stays cleaner, fresher and more durable for its expected lifetime.

For more information on Microban antimicrobial technologies for plastics, contact a member of the team today.