Table of contents
Table of contents
As the global plastic waste crisis escalates, the necessity for innovative and sustainable solutions grows. One transformative approach is incorporating both recycled plastics and bio-based materials in the formulation of powder coatings. allnex is championing this shift with its ECOWISE™ CHOICE products, including CRYLCOAT® OCEAN powder coating resins.
The plastic waste dilemma
The escalating plastic waste crisis is a pressing global concern. Despite ongoing recycling efforts, a substantial amount of the hundreds of millions of tons of plastic ends up in in the oceans.
Figure 1: Per capita contribution to oceanic plastic pollution worldwide
The statistics from Our World in Data underscore the severity of the issue, revealing a concerning trend in plastic waste production and disposal. The unequal distribution of responsibility for plastic pollution across different countries is particularly striking. Given these trends, the need for innovative solutions to manage plastic waste effectively and sustainably is clear.
The benefits of powder coating
Traditional strategies for managing plastic waste, such as recycling and incineration, have so far proven insufficient to address the scale of the issue. By integrating recycled plastics into powder coating resins, we not only reduce plastic waste but also create a product with enhanced properties.
Transforming plastic waste into an opportunity
The solution to the plastic waste problem begins with raising consumer and industry awareness about the potential of recycled plastics and bio-based materials in powder coating resins.
Market awareness and circular economy initiatives
Figure 2: The linear and circular economy
Initiatives promoting a circular economy play a vital role in this transformation. The idea is to transition from a linear model of ‘take-make-dispose’, to a circular economy where waste becomes a resource.
Regulatory impacts and materials
Government regulations and the environmental impact of raw materials play a role in driving the shift towards sustainable solutions. The inclusion of recycled plastics and bio-based materials in powder coating resins aligns with these regulations and reduces reliance on non-renewable raw materials.
Sustainable powder coating resins
allnex has identified five pillars in its strategy towards sustainable coatings. These pillars are based on the UN’s 17 sustainable development goals (SDGs). Here we will focus on ‘Cicural economy‘ and ‘Renewable sourcing‘.
A circular approach
A circular approach in the value chain is fundamental to transforming plastic waste into a resource. The aim is to recycle materials for the same or similar applications rather than downcycling them. The Extended Producer Responsibility (EPR) plays a key role in this by shifting the responsibility from consumers to producers.
Recycling waste PET
allnex are introducing new powder coating technology with up to 25% recycled PET (rPET) in these powders. The reason why only 25% rPET can be used in polyester resins for powder coating resins lies in the differences in chemical structures of the polyesters.
Schematic 1. Structure of PET. The relatively simple repeating structure does not lend itself to a lot of flexibility which results in a high melting point.
Depending on how PET is treated and its thermal history, PET can be amorphous or semi-crystalline. Its melting point is upward of 250 ºC which makes it difficult to melt or dissolve/mix with polyesters of lower melting points. Polyesters designed for powder coating resins have much lower melting points due to the internal design of their molecular structure.
Schematic 2. Low melting point ultra durable polyester structure as used in modern powder coatings. Molecular swivel points are designed into the polymer structure (white arrows).
Chemically, rPET is most conveniently incorporated into polyesters used in powder coatings by means of depolymerizing the PET through transesterification. The process of incorporating or depolymerizing rPET is referred to as glycolysis because it is done in the presence of glycols (similar to those used in making polyester resins for powder coatings).
Complete glycolysis (the complete depolymerization of rPET into terephthalic acid and ethylene glycol) is difficult to achieve. The likelihood of rPET oligomer incorporation to the final polyester structure can be high.
Schematic 3. Glycolysis of rPET in the presence of ethylene glycol without a catalyst. In this case m < n. The final product is bis(2-hydroxyethyl) terephthalate (BHET).
A careful balance of incorporating terephthalic acid, oligomers and bis(2-hydroxyethyl) terephthalate into the polyester structure is required. Too much of these compounds in the polyester structure will adversely affect the performance of the polyester and therefore the final powder coating. If the amounts are not optimal, properties such as melting point, hardness and outdoor (UV) stability may be compromised.
The glycolysis reaction of rPET is a slow reaction therefore catalysts such as zinc acetate, sodium hydroxide or strong acids such as sulphuric acid may be contemplated.
Sourcing rPET
The steps involved in sourcing and re-introducing rPET into the synthesis of polyesters that can be used for powder coating resins can be seen below.
Figure 3. Steps in the use of rPET as a sustainable raw material for the production of polyesters.
Figure 4. Examples of rPET that can be obtained from numerous sources. allnex uses rPET directly from manufacturing plants that use PET in applications such as packaging.
Superior powder coating performance
These enhanced properties are not just theoretical. The research conducted by allnex demonstrates the superior performance of powder coatings formulated with renewable polyester compared to conventional hybrids. The figure below showcases the promising results, offering tangible proof of the potential of these sustainable powder coating solutions.
Below are the results with renewable polyester No. 1 compared to a conventional 70/30 hybrid polyester.
Mechanical properties
| 6 months aging of cured film |
10 min at 180° DI/RI |
10 min at 180° T-Bend |
|---|---|---|
| Conventional 70/30 PE white formulation |
120/120 | 1-T |
| Polyester No.1 white formulation |
160/160 | 0-T |
Polyester No.1 1-100 double rubs MEK
CRYLCOAT® OCEAN
allnex is using recycled polymer waste streams as building blocks for powder coating polyesters to help reduce pollution from single-use plastics. Designing our coating resins we are able to repurpose post-consumer PET, enabling us to respond to the requirements of green technology and we contribute to the circular economy by long term management of polymer waste.
The CRYLCOAT® OCEAN product range is designed to have no differences in workability compared to traditional powder coating resins.
CRYLCOAT® OCEAN 2489-5 is the first born powder coating polyester resin containing 25% recycled PET in allnex portfolio. This resin can be formulated with the major powder coating crosslinkers, such as triglycidyl- isocyanurate (TGIC) and β-hydroxy-alkylamide (HAA) systems and can be used for both indoor and outdoor applications such as industrial metal including household appliances, metal furniture and fittings.
While CRYLCOAT® OCEAN 2489-5 represents a progressive step towards sustainability, it is not yet part of the ECOWISE™ CHOICE range. Every technology faces its own set of unique challenges which allnex are committed to addressing in order to meet the high standards of ECOWISE™ CHOICE. We are in constant collaboration with our partners to improve the sustainability of our product portfolio. If you are interested in improving the sustainability of your products, please contact our experts.
The future of powder coatings
With CRYLCOAT® OCEAN powder coating resins, we envision a future where plastic waste becomes a resource. allnex is leading this change, providing solutions that maintain the functional requirements of powder coatings while integrating recycled plastics and bio-based materials. As we continue to navigate the complexities of the plastic waste crisis, collaboration, innovation and informed decision-making will be key to achieving our sustainability goals. If you’re interested in learning more about how allnex can help, don’t hesitate to contact an allnex expert today.
FAQ
Let’s answer some of the most frequently asked questions about CRYLCOAT® OCEAN product range and rPET resins:
