Advanced Plastics Made from Seeds

By David Schilpp

Plastics, the name many use for materials made from polymers, play a critical role in modern life and help meet many of the world’s largest challenges. Cell phones, computers, and many life-saving medical devices would not exist in the world today without polymers. Polymers also make possible the development of modern-day coatings.

Most surface coatings contain synthetic polymers to bind a pigment and/or a performance additive to a desired surface. The synthetic polymer used in coatings, or the “binder,” can vary in its chemistry (e.g., nylon, epoxy, polyester, acrylic, etc.). Many nylons, a term used for thermoplastic polyamides, are traditionally made from petroleum-based materials. However, Rilsan® polyamide 11, a polymer manufactured by Arkema, starts as a seed in the earth.

The Pragati Program
 As consumers become more eco-focused, Arkema wanted to offer more than just a bio-sourced material. Arkema wanted to help ensure the material source operated sustainably, and hence joined forces with other chemical companies and a nonprofit. In May 2016, Arkema, BASF, Jayant Agro-Organics along with implementation partner Solidaridad, started the Pragati Program for farmers in Gujurat, India, where the majority of the world’s castor supply originates.

As a Kharif crop (plants that are cultivated and harvested during the Indian subcontinent monsoon season), castor takes great advantage of the seasonal monsoon rains and the local semi-arid climate. Castor cultivation causes zero deforestation and does not compete with food crops. The Pragati Program aims to enable sustainable castor crop production by using good agricultural practices to increase yield and farmer income, efficiently use water resources and maintain soil fertility, drive adoption of good waste management practices, enable better health and safety, and respect human rights. The Pragati Program has helped train and certify more than 5,800 farmers, reduced water consumption by approximately 35%, and improved yield by 25%. Over 13,300 hectares (32,900 acres) are now being farmed in accordance with the SuCCESS™ sustainable castor code (see www.castorsuccess.org), a code with 76 auditable criteria based on 11 principles. The pictures in Figures 1 and 2 represent two improvement scenarios of farming practices before and after training. The first series shows more efficient planting to help drive higher yield. The second series portrays the difference in water consumption and yield when farmers practice skip-furrow irrigation (after) versus furrow irrigation (before).

Because of the success in the Pragati Program, Arkema and partners committed to a second phase in 2019, which aims to continue educating farmers on good agricultural practices, increase involvement of women in the supply chain, scale up farmer participation to at least 7,000 farmers by the end of 2022, and create greater awareness for downstream users.

Turning Seeds to Resin
Once harvested, farmers sell the seeds for downstream processing. The castor seeds are crushed to generate castor oil and castor cakes. Farmers primarily use castor cakes as a fertilizer (naturally fungicidal against plant parasitic roundworms) for sugarcane, grapes, cotton, rice, coffee, etc., or burned as fuel. Arkema purchases the castor oil to convert it to amino 11, then polyamide 11 resin (Figure 3).

 The resin has been a trusted source of performance for over 70 years for several different downstream markets and applications. Since 1947, Arkema has been the only industrial producer of this unique polymer derived from castor. The automaker Citroën first grasped the potential of extruding the material to make fuel lines. Applications then further evolved into cell phone components, running shoes, 3D printed eyewear frames, hydrogen fuel tanks, and many other unique applications including using the material to create powder coatings. As a biobased material, the eco- friendly powder coating offers a lightweight, extremely durable, and easy-to-apply solution for extending the life of metal parts exposed to high impact, corrosion, high voltage, and abrasive environments.

Coaters can apply the polymide 11-based powder coatings via electrostatic spray, fluid bed dip, hot floc/spray, flame spray, or minicoat processes. Easily applied with a low energy fusion, the coating offers chemical and corrosion resistance, high durability, and electrical insulation for a variety of everyday products to extend a part’s useful life.

It also has excellent chemical resistance to not only grease and hydrocarbons, but acids, bases, and salts, too. During exposure to chemicals, even at elevated temperatures, the powder coating maintains good dimensional stability and resists degradation of the polymer matrix.

In addition, it maintains very low permeation to hydrocarbons. The high abrasion and impact resistance, especially at low temperatures, can be attributed to the polymer’s fine crystalline grid and spherolitical structure, as well as its molecular weight and polydispersity (the polymer is non-uniform and contains polymer chains of unequal length, and so the molecular weight is not a single value). Performance rivals or exceeds epoxies, polyesters, and polyolefinic copolymers and generally other polyamides when it comes to impact and abrasion resistance. The powder coating created from the biobased resin offers high durability while also providing great protection from high voltage. The dielectric resistance of polyamide powder coatings can reach as high as 65kV/mm at 125μm.

Fields of Application
 End-use specialty markets for polyamide 11-based powder coatings include automotive, medical, furniture, oil and gas, chemical processing, battery components, and consumer electronics. The automotive industry widely uses these powder coatings for the material’s lubricity and excellent durability. The abrasion resistance and lubricity prevent a drive shaft, sliding car door or seat, car hood supports, or other small parts (hooks, clips, springs, etc.) from failing. As an added benefit, the material offers significant noise dampening.

Manufacturers of pipes, fittings, and connectors use it to extend in-service life due to corrosion and chemical resistance. Coated parts will withstand highly corrosive environments proven through accelerated aging at 200+ hours in 5% bleach solution and 2,000+ hours in salt water.

Growing markets like electrical vehicles (EV) and semiconductors have demanded the high performance the coating offers as well. EV manufacturers use it for busbars, connectors, battery racks, and intercell cooling elements due to the excellent dielectric resistance, flexibility, and durable performance at high and low temperatures. The coating can be applied on straight bus bars prior to bending the bar into the desired shape due to the flexibility of the material.

Sustainability starts with sourcing materials from renewable resources through sustainable practices. As a next step, companies must choose the best material to minimize the impact on the environment and maximize the life of the part. Not only does polyamide 11-based powder coating offer high performance, but the material offers coaters a biobased alternative that is sustainably sourced from castor farming.

David Schilpp is account manager for powder coatings at Arkema.