Vinyl pencil eraser
Softened PVC is formulated into an eraser that lifts pencil marks from paper.
Material
Soft PVC-based eraser block: PVC
Material selection rationale
- Soft formulation
- Conforms to the paper during rubbing.
- Controlled wear
- Small worn-away crumbs help carry loosened graphite away.
- Useful controlled wear
- The eraser is designed to shed some material during rubbing; excessive durability alone would not explain good erasing.
How it becomes a product
- Mix the formulation: PVC is combined with the chosen plasticiser, fillers and other eraser ingredients. Plasticiser and fillers tune softness and wear before forming; the sleeve is added later and is outside the polymer chemistry.
- Form and finish: The compound is formed into blocks or a continuous profile, then cut and sleeved.
Preparation routes
Vinyl chloride route
Free-radical addition polymerisation. Vinyl chloride molecules link into PVC chains. The resin is then formulated differently for rigid pipes and flexible coverings. The original double bond is consumed, while the C–Cl bonds remain in the repeat unit. Flexible and rigid PVC can therefore have the same polymer origin.
An initiator starts chain growth. Stabilising additives and, for flexible formulations, plasticisers are separate from the monomer. Plasticiser acts mainly by altering chain mobility; it is not a second polymerising feedstock.
- PVC: monomer production, polymerisation and usesChemical Industry Education Centre, University of York
From ethene to vinyl chloride
- Ethene + Chlorine → 1,2-Dichloroethane
Direct chlorination adds chlorine across ethene's double bond.
- 1,2-Dichloroethane → Chloroethene
Industrial cracking removes hydrogen chloride, leaving the double bond in vinyl chloride.
- PVC: monomer production, polymerisation and usesChemical Industry Education Centre, University of York
Sources
- Erasers: PVC formulations and PVC-free alternativesSTAEDTLER
- PVC: monomer production, polymerisation and usesChemical Industry Education Centre, University of York