WiSys Technologies

OVERVIEW

Thermoset materials, such as cured rubber and phenolics, offer enhanced properties over traditional thermoplastics (such as Poly(lactic acid) or PLA, polystyrene, PET, etc.). This is due to their ability to crosslink making them better suited for high-temperature applications. However, they are generally more brittle, are insoluble and non-reformable and therefore are among the most difficult polymeric materials to recycle and reuse. As a result there is a clear and unmet need for the development of polymer materials with improved properties over thermoplastics such as PLA, while also being capable of readily degrading and being reused.

INVENTION

Research from the University of Wisconsin-Stevens Point has resulted in the development of a series of crosslinkable, degradable thermoset polymers with reversible crosslinking from mercaptosuccinic acid and diols. This novel series of polymers have utility for a broad range of applications including health care, durable goods and packaging.

Monomeric base materials are polymerized in a facile synthesis and crosslinked (cured) with methods compatible with current industry methods, allowing for the creation of resins with a wide variety of properties. The crosslinking reactions offer the unique feature of being readily reversible allowing for depolymerization to monomers, thereby providing for recyclability for use in sustainable commodity applications, aka “sustainable thermosets”.

The polymers are degradable under commercial compost conditions comparable to current bio-derived compostable polymers such as PLA and polycaprolactone. Properties such as duration of degradation in a compost setting, material pliability, toughness and optical clarity are controllable via the degree of polymer crosslinking. In addition, copolymers with PLA, such as poly(lactic acid-copentylenemercaptocuccinate) have been developed in an effort to improve the physical characteristics of PLA. 

APPLICATION(S)

• Platform technology with utility across a broad range of applications including consumer, healthcare or technical products that are potentially bio-derived, recyclable or compostable following use. These include:
  • Biodegradable polymers for industrial applications such as injection molded products/films, durable goods, disposable food containers and utensils;
  • Biodegradable polymers for packaging applications such as packaging with barrier protection, with enhanced protection against oxygen (e.g. bottles, food packaging, films etc…);
  • Bioresorbable polymers for medical applications with controlled degradation times, including sutures, screws, suture anchors, support membranes, plates/mesh, and/or pins/rods;
  • Biodegradable polymers for applications in the paper industry, improving the wet strength of paper products while retaining desired properties of paper such as compostability;
  • The polymer materials have the potential to be used as adhesives in wood products. They could for instance potentially replace formaldehyde resins in plywood and fiberboard. Formaldehyde has been associated with health risks and may cause concerns for consumers.

KEY BENEFITS

• Processing times and conditions are similar to available thermoset resins;
• Low odor; Curing (cross-linking) of the polymer series has produced polymers with high thermal stability at elevated temperatures greatly exceeding that of PLA;
• A direct comparison of compostability has been made between these materials and PLA;
  • Polymers have been shown to degrade to a similar extent and timeframe as PLA and degradation time of cured samples can be controlled by adjusting the crosslink density of the polymers;
• Cured crosslinked films are insoluble in organic solvents and infusible, but degrade readily under aqueous conditions when heated following parameters similar to those employed to reclaim PLA;
• Post-curing enhances the mechanical strength and glass transition temperature (Tg) with some-fully cured members of the series possessing a Tg at or above that of PLA. Uncured materials have shelf lives at room temparature greater than one year. Cured materials are stable under ambient use conditions for long periods;
• Cured films have readily undergone hydrolysis at elevated temperatures to produce clear aqueous solutions;
• Some members of the series exhibit excellent optical transparency after curing with a refractive index near that of ordinary glass (~1.5);
• The adhesive properties of the materials can be controlled with many possessing strong adhesive properties on a variety of surfaces and materials;
• Select materials show elastomeric properties similar to rubber, including foams, while others are rigid. Both types can be  readily degraded at the end-of-life for reuse.