Garden chair

Moulded PP gives an outdoor chair its continuous seat, back and legs.

Garden chair, illustrative image

Material

PP matrix of the chair body: PP

Material selection rationale

Low density
Makes a chair easier to move.
Mouldable structure
Ribs, curves and legs help carry the load without a solid block of plastic.
Reinforcement and load paths
Glass fibres stiffen the PP compound while ribs and curved sections route loads from the seat to the legs.

How it becomes a product

  1. Prepare the formulation: PP is compounded with the chosen reinforcement, pigment and stabilisers.
  2. Injection-mould the chair: A mould shapes the body; the part cools before removal and finishing. Flow during moulding influences fibre orientation and shrinkage, so the moulded chair cannot be treated as an isotropic block of PP.

Preparation routes

Propene route

Catalytic addition polymerisation. Propene molecules join into chains. A suitable catalyst controls chain growth and the arrangement of the methyl side groups. Catalyst-controlled arrangement of methyl groups can favour regular packing. The monomer formula alone does not describe this tacticity.

A coordination catalyst system is used; it is not counted as a monomer. A thermoplastic moulding or foam uses already-made PP, not propene reacting inside the final product.

  1. Poly(propene): manufacture and usesChemical Industry Education Centre, University of York

Sources

  1. Bit chair: glass-fibre-reinforced polypropyleneNardi
  2. Polypropylene supply and injection moulding at ArsoNardi
  3. Poly(propene): manufacture and usesChemical Industry Education Centre, University of York