Polymer and plastic composites are plastics which are strengthened with fibers, fillers, particulates, powders and other matrix reinforcements to provide improved strength and/or stiffness. Examples include fiber reinforced plastics (FRPs), sheet molding compounds (SMCs), bulk molding compounds (BMCs), pre-preg materials, and fabricated composite parts.
The GlobalSpec SpecSearch Database contains listings of a variety of different polymer matrices. Some of the most common are epoxy, polyacetal, PEEK, fluoropolymers, and phenolics.
Epoxy resins exhibit high strength and low shrinkage during curing. They are known for their toughness and resistance to chemical and environmental damage. Most are two-part resins cured at room temperature. Depending on the formulation, epoxy resins are used as casting resins, potting agents, resin binders, or laminating resins in fiberglass or composite construction. They are also used as encapsulates, electrical conductors in microelectronic packaging, and adhesives in structural bonding applications.
Polyacetal or polyoxymethylene (POM) is a thermoplastic used in precision parts that require high stiffness, low friction, and excellent dimensional stability. It provides a higher strength material compared to polyethylene-type polymers; however, polyacetal materials are susceptible to oxidation at elevated temperatures. DuPont’s Delrin® is a common polyacetal engineering resin that is also used to mold plastic parts.
PEEK or polyether ether ketone is a colorless organic polymer thermoplastic. It has excellent mechanical and chemical resistance properties that are retained at high temperatures. It is highly resistant to thermal degradation as well. It is used extensively in the aerospace, automotive, electronic, and chemical process industries.
Fluoropolymers including polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) are used in applications requiring superior chemical resistance. PTFE is used in applications requiring superior chemical resistance or low friction.
Phenolics are thermosetting molding compounds and adhesives that offer strong bonds and provide good resistance to high temperatures. Phenolic resin adhesives made from chemicals of the phenol group and formaldehyde are generally the most durable. Phenolic resins are available in liquid, powder, and film form. Special phenolic resins are available that harden at moderate temperatures when mixed with suitable accelerators. Urea formaldehyde resins can harden rapidly at moderate temperatures, but generally do not have the properties of phenolic resins. Melamine resins have excellent dielectric properties.
Products may be strengthened with fibers, fillers, particulates, powders and other matrix reinforcements to provide improved strength and/or stiffness. Fibers are usually chopped, wound or woven and made of materials such as fabric, metal, glass, or fiberglass. Particulates vary in terms of shape and size. Powders are usually made of carbon, graphite, silicates, ceramics, and other organic or inorganic materials. Some matrix reinforcements provide improved electrical conductivity. Others offer improved thermal conductivity.
Thermoplastic composites include glass mat thermoplastics (GMT), weave-reinforced GMTs, low-density composites, and composite sandwich panels. GMTs are compression-molded thermoplastics that are used in place of metals such as aluminum or steel, plywood, or even engineered materials. Weave-reinforced GMTs are synthetic fabrics that are used as automotive materials to provide enhanced protection of a car’s underbody on poorly surfaced roads.
Polymer and plastic composites vary in terms of features. Products that are designed for electrical and electronics applications often provide protection against electrostatic discharge (ESD), electromagnetic interference (EMI), and radio frequency interference (RFI). Materials that are electrically conductive or resistive are also available. Polymer and plastic composites that use a phase change provide enhanced thermal characteristics.
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Conformal coatings encapsulate circuit boards and their electronic components in order to prevent the ingress of moisture, fungus, dust and other environmental contaminants.
Epoxy adhesives are chemical compounds for joining components. They require clean surfaces and are valued for their toughness and resistance to chemical and environmental damage.
Gel elastomers are highly viscoelastic polymer gel materials that have excellent shock absorption and damping characteristics. They are available in a variety of material types and grades.
Pressure Sensitive Adhesives (PSA) and Contact Adhesives
Pressure sensitive adhesives (PSA) and contact adhesives adhere to most surfaces with very slight pressure. They are available in solvent and latex or water-based forms.
Silicone Adhesives and Sealants
Silicone adhesives and sealants have a high degree of flexibility and a very high temperature resistance (up to 600° F), but lack the strength of other epoxy or acrylic resins.
Thermoplastics and Thermoplastic Resins
Thermoplastics and thermoplastic materials soften when heated and harden when cooled. They can withstand many heating and cooling cycles and are often suitable for recycling.
Thermosets and Thermoset Resins
Thermosets and thermoset materials are crosslinked polymeric resins that are cured or set using heat or heat and pressure. They generally have a higher resistance to heat than thermoplastics.