Adhesion Force: A chemical or physical force that hold two pieces of material together at the bond interface
Bulk Density: Mass per unit volume of a material, including any voids present
Cellular Rubber: Rubber products containing cells or hollow receptacles
Chalking Rubber: Formation of a powder residue on the surface or rubber material due to surface degradation
Creep: Time-dependent part of strain resulting from stress
Crosslinking: The formation of a three dimensional polymer material by interchain reactions that lead to changes in physical properties
Degradable Plastic: A plastic designed to undergo a significant change in its chemical structure under specific environmental conditions resulting in a change in properties
Dumbbell Specimen: Specimen that is flat and has a narrow uniform central portion with enlarged ends
Elastic Limit: Greatest stress that a material is capable of sustaining, without any permanent strain remaining, upon complete release of the stress
Elastic Shear Modulus (G): Ratio of the shear-stress component in phase with the shear strain, to the shear strain
Elastic Young’s Modulus (E): Ratio of the normal stress component in phase with the normal strain, to the normal strain
Elasticity: Rapid recovery of a material to its initial shape and dimensions after deformation
Elastomer: An elastic polymer that turns rapidly to its initial dimensions and shape after substantial deformation
Elongation: Extension produced when tensile force is applied to a test specimen
Percent Elongation: Final length minus the original length divided by the original length expressed as a percentage
Ultimate Elongation: Elongation at failure or rupture of the specimen
Ethylene Plastic: A plastic structured with polymers of ethylene or copolymers of ethylene with other monomers
Expandable Plastic: A plastic in a form capable of being made cellular by thermal, chemical, or mechanical means.
Expanded Rubber: Cellular rubber having closed cells made from solid rubber compound
Extensometer: Displacement measuring device used to determine the elongation of a test specimen as it is strained
Furan Resin: A resin in which the furan ring is an integral part of the polymer chain and represents the greatest amount by mass
Gauge Length: The original length of the portion of the specimen over which strain, elongation, or the change of length are determined.
Gel Rubber: A portion of the raw rubber insoluble in a specific solvent, in which, without crosslinking, the raw rubber would be soluble
Glass Transition: The reversible change in an amorphous polymer or in amorphous regions of a partially crystalline polymer from a viscous or rubbery condition to a hard and relatively brittle one
Glass Transition Temperature: The approximate mid-point of the temperature
Grain: Anisotropy into rubber during processing
Granulated Rubber: Rubber composed of non-spherical particles with maximum particle dimension from below 425 µm (40 mesh) to 12 mm (0.47 in.)
Ground Rubber: Particulate rubber composed of non-spherical particles with maximum particle dimension from well below 425 µm (40 mesh) to 2 mm (0.08 in.)
Ground Vulcanized Rubber: Vulcanized rubber in particulate form, generally used as an extender or filler
Hardness: Resistance to indentation
Inhibitor: Material that suppresses a chemical reaction
Latex: Colloidal aqueous dispersion of rubber
Mineral Rubber: Compounding material other than rubber that is prepared from petroleum asphalt and used as a softener, tackifier, or extender
Mold: Device with cavities that is used to shape a material
Compression Molding: Applying compressive force to a material that is placed in the mold cavity to form it to the final desired shape
Injection Molding: Applying heat through a sprue into the mold cavity by means of a pressure gradient from an external heated chamber to form a material to the final desired shape
Molecular Weight: Ratio of the mass of a molecule to one-twelfth (1⁄12) of the mass (1.6605 × 10-27 kg) of a Carbon-12 atom
Necking: Localized reduction in the cross-section of a test specimen due to applied tensile force
Particulate Rubber: Rubber material that is vulcanized or unvulcanized, with or without coating, that has been transformed into a collection of particles
Payne Effect: The decrease in the numerical value of modulus calculations in low-amplitude fatigue testing of filled rubber specimens
Plasticity: Characteristic of unvulcanized rubber indicated by the degree of retention of deformation after removal of force
Plasticity Retention Index (PRI): Ratio of plasticity measured after air-oven ageing to a plasticity number prior to ageing
Plasticizer: Compounding material that enhances polymer deformability
Puncture Strength: Maximum mechanical force required to puncture a specimen
Resilience: Ratio of energy transferred to energy received when a specimen is deformed
Resin: A material of indefinite and relatively high molecular mass that may be used as a softener, processing aid, vulcanizing agent, or reinforcing agent
Rubber: A material that is capable of recovering from large deformations quickly and forcibly, and can be, or already is, modified to a state in which it is essentially insoluble (but can swell) in boiling solvent, such as benzene, methyl ethyl ketone, or ethanol-toluene azeotrope
Tear Strength: Maximum mechanical force required to tear a specimen
Tensile Strength: The maximum tensile stress applied in stretching a specimen to failure
Tensile Stress: A stress applied to stretch a test specimen in tensile load
Thermoplastic Elastomers: A family of rubber-like materials that consist of materials with both thermoplastic and elastomeric properties and that can be reprocessed, remolded, and recycled
Thermoplastic Vulcanizate: Thermoplastic elastomer with a chemically crosslinked rubber phase that is procuded by dynamic vulcanization
Thermoset: A polymer material that changes into a non-flowable, infusible, insoluble form upon vulcanization
Viscoelasticity: Property of a material that exhibits some combination of both elastic or spring-like and viscous or flow-like behavior
Vulcanization: Irreversible process during which a rubber compound, through a change in its chemical structure (for example, crosslinking), becomes less plastic and more resistant to swelling by organic liquids, while elastic properties are conferred, improved, or extended over a greater range of temperature.
Yield Point: The point at where the rate of stress with respect to strain goes through a zero value and may become negative
Definitions are based on terminology from ASTM D883 Standard Terminology Relating to Plastics and ASTM D1566 Standard Terminology Relating to Rubber.
3D-Printing
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.
Recyclable Plastics
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.
Medical Applications
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.
Scratch-proof Cars
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.