Plastic and rubber materials are tested for quality and assessment to ensure materials and end products meet specifications and will perform as designed over their lifecycle. Mechanical testing of plastics and rubber materials are governed by industry standards such as ASTM and ISO standards. Common standards include:
- ASTM D412 – Standard Test Methods for Vulcanized Rubber and Thermoplastic Elastomers – Tension
- ASTM D624 – Standard Test Method for Tear Strength of Conventional Vulcanized Rubber and Thermoplastic Elastomers
- ASTM D638 – Standard Test Method for Tensile Properties of Plastics
- ASTM D695 – Standard Test Method for Compressive Properties of Rigid Plastics
- ASTM D751 – Standard Test Methods for Coated Fabrics
- ASTM D790 – Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials
- ASTM D882 – Standard Test Method for Tensile Properties of Thin Plastic Sheeting
- ASTM D1414 – Standard Test Method for Rubber O-Rings
- ASTM D1894 – Standard Test Method for Static and Kinetic Coefficients of Friction of Plastic Film and Sheeting
- ASTM D2290 – Standard Test Method for Apparent Hoop Tensile Strength of Plastic or Reinforced Plastic Pipe
In addition to following standardized test methods, companies may design their own verification and test plans to gather applicable data. Tension testing is a commonly applied test method where the test specimen is pulled and stretched in the tensile direction. Compression testing, on the other hand, compresses the specimen, usually in between an upper and a lower compression platen. Bend testing is also run in the compressive direction; the specimen is mounted on a bend fixture and the load is applied via third-point or four-point loading so that the specimen is bent as it fails. Other static tests include puncture testing, friction testing, peel testing, and more.
Rubber, or elastomer, specimens often show a high elongation, thus it is important to ensure failure occurs within the measuring range of the testing system.
Fatigue testing is another type of test where the specimen is subjected to loads over a specific course of time. Properties such as peak load, elongation percentage, modulus of elongation, yield to break are calculated to analyze how the material will perform over time and repeated use.
Plastics are the most commonly used material for additive manufacturing and 3D-printed plastics are an important topic of research as they can be used in various applications. Researchers in Rutgers University-New Brunswick School of Engineering have embedded high performance electrical circuits inside 3D-printed plastics that can be used in smaller devices with reduced energy use and increase in performance. Further research includes making fully 3D internal circuits, enhancing conductivity, and creating flexible internal circuits inside the 3D structures.
Another important research topic in plastics is the challenge to recycle plastic waste. According to researchers at the U.S. Department of Energy’s (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) (https://www.sciencedaily.com/releases/2019/05/190507110452.htm), the challenge with recycling plastic material arises from the fact that as plastics with different chemical compositions are mixed together to form the end-product, it is hard to tell which properties will be inherited from the original plastics. Thus, the recovery of the original monomers becomes an unknown equation. Researchers have developed a new plastic material called poly(diketoenamine), or PDK, with reversible bonds that can be recycled by dunking the material in a highly acidic solution. The acid breaks the bonds between the monomers of the PDK to separate the chemical additives that would otherwise prevent the plastic to be upcycled. PDK can be used in adhesives, phone cases, watch bands, shoes, cabling, and more. Further research is planned to use PDK plastics in applications such as textiles, additive manufacturing, and foams.
Material science research involving plastics and rubber materials also focus on the development of medical products. Researchers from Chalmers University of Technology, Sweden, have created a new, rubber-like material that is soft, elastic, easy to process. Potential applications of the new material include using is as a replacement for human tissue or as a drug delivery system. Researchers are also looking to develop antibacterial urinary catheters with the material as well as to 3D print it into specific structures.
A newly developed rubber material has also been proven to be useful for the automotive industry; graphene can be used as a scratch-proof paint for cars. Mechanical properties, specifically the Young’s modulus, of the hexagonal boron nitride (h-BN) are similar to those of diamond, yet h-BN is much cheaper, more flexible, and lighter. An international group of researchers have found that bilayer graphene develops a super-lubricity state where heat is not released during friction and additional mechanical strength is developed in the layers of the material. In real-world applications, graphene could be used to created flexible smart devices with resistance against corrosion as well as scratch-proof cars.