Plastic Resin

Listed below are the primary resins used in the manufacture plastic components. Following are some of the characteristics and features of resins used in molding plastic parts. Also listed is the Society of the Plastic Industry (SPI) resin identification code number.

High Density Polyethylene (HDPE)              2

Flexible but more rigid than LDPE. Natural color is milky white, semi- translucent depending on density. Good impact strength and stress crack resistance. Good chemical resistance. Good vapor barrier but poor gas barrier. Sterilizable via EtO or gamma radiation.

Low Density Polyethylene (LDPE)                  4

Very flexible, natural milky color, translucent with high impact strength. Excellent for mild and strong buffers, good chemical resistance. Good water vapor and alcohol barrier properties. Poor gas barrier, sterilizable with EtO or gamma radiation. Good stress crack and impact resistance.

 

Linear Low Density Polyethylene (LLDPE)  4

Very flexible, natural milky color, translucent with high impact strength. Excellent for mild and strong buffers, good chemical resistance. Good water vapor and alcohol barrier properties. Poor gas barrier, sterilizable with EtO or gamma radiation. Good stress crack and impact resistance.

Polybutylene Terephthalate (PBT)              7

Good chemical resistance, clear color, resistant to water, weak acids and bases at room temperature. Can be sterilized by EtO and autoclaving, at temperatures up to 180°C.

Polycarbonate (PC)                                            7

Rigid and strong, excellent clarity. High impact strength. Poor barrier properties.

 

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Polyethylene Terephthalate (PET)                 1
Semi-rigid to rigid depending on wall thickness. Natural color — clear and transparent. Good alcohol and solvent barrier; good gas and fair moisture barrier. Good to fair chemical barrier; not good for strong acids or bases. Good moldability. Sterilizable through EtO and gamma radiation. Good stress crack and impact resistance at room temperature and above.

Polypropylene (PP)                                            5

Rigid, solid, durable in container or closure forms. Opaque, natural grayish yellow in natural form. Excellent stress crack and impact resistance. Excellent moisture barrier, good oil and alcohol barrier, poor gas barrier properties. Good chemical resistance. Sterilizable with EtO or autoclaving.

Polystyrene (PS)                                                6

PS is a transparent, rigid and glass-like polymer. Good resistance to inorganic chemicals. Light and heat stable, biologically inert and non-toxic. Poor impact and stress crack resistance, poor barrier properties. EtO or Gamma sterilizable.

Polyvinyl Chloride (PVC)                                 3

Flexible to rigid. Good for coatings; fair water and good oxygen barrier. Transparent to yellowish color in natural state. Good chemical resistance. Sterilizable by EtO. Good impact and some stress crack resistance. Poor recycling due to chloride residues.

PTFE, FEP, PFA                                                    7

Polytetraflouroethylene, fluorinated ethylene propylene, perfluoralkoxy. All fluoropolymers feature opaque characteristics, excellent chemical resistance, good heat stability and thermal shock resistance. All are autoclavable, heat, and gas sterilizable.