Specialty Polymers and Resins

Specialty polymers and resins are proprietary polymers, resins, monomers and intermediates. This category includes plastics and elastomers that are based on proprietary curing technologies or chemistries, or that are designed for specialized applications. Specialty polymers and resins are available in a variety of forms. Resin raw materials include pellets, powders, granules, and liquids. Polymeric and elastomeric raw materials are available as stock shapes that can be used to fabricate parts. Specialty polymers and elastomers can also be used to create patterns, molds, and rapid prototypes. Electronic-grade products are used in thermal interface materials, potting and encapsulating compounds, conductive adhesives, and dielectric sealants. Optical-grade materials are used to develop transparent polycarbonate and acrylic lenses. Purging compounds are used to clean out molding machines between runs of different colors or compositions.

Mechanical and physical properties for specialty polymers and resins include flexural strength, tear strength, ultimate tensile strength, tensile yield strength, tensile modulus, elongation, and impact toughness. Flexural strength or yield is the maximum fiber stress that a specimen can withstand before cracking or breaking. Tear strength measures the tear resistance of thin, flexible materials. Ultimate tensile strength (UTS) is the maximum amount of stress required to fail or break a material under tension-loading test conditions. By contrast, tensile yield strength (YS) is the amount of stress required to begin to permanently deform the material. The tensile modulus (Young’s modulus, modulus of elasticity) is a material constant that indicates the variation in strain produced under an applied tensile load. Elongation is the percentage of deformation that occurs. The amount of energy absorbed measures the material’s impact toughness. Density, the mass per unit area, and water absorption are additional considerations.

Thermal properties for specialty polymers and resins include maximum use temperature, deflection temperature, glass transition temperature, thermal conductivity, and the coefficient of thermal expansion. Maximum use temperature is the temperature range to which a material can be exposed without the degradation of structural or other required end-use properties. Deflection temperature is the temperature range to which a material can be exposed without deflection under a given stress of 264 psi or 1.8 MPa. Glass transition temperature is the inflection point for glassy, non-crystalline materials that are heated. Thermal conductivity is the linear heat transfer per unit area for a given applied temperature gradient. The coefficient of thermal expansion (CTE) is the amount of linear expansion or shrinkage that occurs in a material with a change in temperature.   

Specialty polymers and resins vary in terms of electrical and optical properties. Electrical resistivity, the inverse of conductivity, is the longitudinal electrical resistance of a uniform rod of unit length and unit cross-sectional area. Dielectric strength is the maximum voltage field that a material can withstand before electrical breakdown occurs. The dielectric constant is the relative permittivity of a material compared to a vacuum or free space. Transmission is the amount of light that passes through a material. The index of refraction measures the speed of this light. 

Important processing and physical properties for specialty polymers and resins include viscosity, shrinkage, and melt flow index (MFI). Viscosity, a measurement of a fluid’s resistance to flow, controls how well a resin fills the cavities or voids in a mold. Shrinkage is the maximum percentage of linear shrinkage that occurs after drying, setting, and/or curing. Melt flow index (MFI) is the output flow rate in grams that occurs during a 10-minute period. Blow molding and extrusion processes tend to use lower MFI, while injection molding typically utilizes higher MFI polymers. Process temperature is another important specification for specialty polymers and resins.

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