The Apocalypse

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Plastics production ​

Plastic materials such as HDPE, PET, and others are essential for rebuilding industrial society. This section covers the fundamentals of plastics production, types of plastics, raw materials sourcing, polymerization processes, and practical methods for producing and shaping plastics in a post-collapse environment.

Introduction to Plastics and Their Importance ​

Plastics are synthetic or semi-synthetic organic polymers that have become indispensable in modern life due to their versatility, durability, and low cost. They are used in packaging, construction, transportation, electronics, medical devices, and countless other applications. In a post-apocalyptic or collapsed industrial scenario, re-establishing plastics production is critical for restoring infrastructure, manufacturing, and daily life.

The most common plastics include:

  • HDPE (High-Density Polyethylene): Used for containers, pipes, and plastic bags.
  • PET (Polyethylene Terephthalate): Commonly used for beverage bottles and food packaging.
  • PVC (Polyvinyl Chloride): Used in pipes, window frames, and flooring.
  • PP (Polypropylene): Used in automotive parts, textiles, and packaging.
  • PS (Polystyrene): Used in insulation, disposable cutlery, and packaging foam.

This section focuses primarily on HDPE and PET due to their widespread use and relative ease of production once raw materials are available.

A photo of various plastic products including HDPE containers, PET bottles, and PVC pipes arranged on a workshop table, illustrating the diversity of plastic applications.

Raw Materials for Plastics Production ​

Petrochemical Feedstocks ​

Most plastics are derived from petrochemical feedstocks, primarily hydrocarbons obtained from crude oil and natural gas. The key building blocks are:

  • Ethylene (C2H4): The monomer for polyethylene (PE).
  • Propylene (C3H6): Used for polypropylene (PP).
  • Vinyl chloride (C2H3Cl): For PVC.
  • Styrene (C8H8): For polystyrene (PS).
  • Terephthalic acid and ethylene glycol: For PET.

In a collapsed industrial setting, crude oil refining and petrochemical cracking facilities may be unavailable or limited. However, some crude oil refining and cracking can be restarted on a small scale using charcoal or coke-fired furnaces and simple distillation and cracking setups. See Basic oil processing for foundational knowledge on crude oil distillation and cracking.

Alternative Feedstocks ​

If petroleum is scarce, alternative feedstocks can be considered:

  • Biomass-derived feedstocks: Cellulose, starch, and lignin can be chemically converted into bio-based monomers such as bio-ethylene or lactic acid (for PLA plastics).
  • Recycled plastics: Collecting and reprocessing existing plastic waste is a vital source of raw material. Mechanical recycling involves shredding and remelting plastics, while chemical recycling breaks plastics down into monomers or other chemicals for repolymerization.

A simplified petrochemical refinery flowchart showing crude oil distillation, cracking units producing ethylene and propylene, and polymerization reactors.

Polymerization Processes ​

Polymerization is the chemical process that links monomers into long polymer chains, forming plastics. The two main types are:

Addition (Chain-Growth) Polymerization ​

Used for polyethylene, polypropylene, and polystyrene. Monomers with double bonds (like ethylene) open up and link together rapidly.

  • HDPE production: Ethylene gas is polymerized under high pressure (1000-3000 atm) and temperature (200-300°C) with catalysts such as Ziegler-Natta or chromium-based catalysts.
  • Process details: The reaction occurs in a reactor vessel where ethylene is pressurized and heated in the presence of catalysts. The polymer forms as a solid or slurry, then is cooled and pelletized.

Condensation (Step-Growth) Polymerization ​

Used for PET and nylon. Two different monomers react, releasing small molecules like water.

  • PET production: Terephthalic acid reacts with ethylene glycol in a two-step process: esterification followed by polycondensation.
  • Process details: The reaction requires precise temperature control (250-280°C) and vacuum conditions to remove byproducts and drive polymer formation.

Practical Considerations for Small-Scale Polymerization ​

  • Catalysts: Ziegler-Natta catalysts are complex to produce but essential for HDPE and PP. Chromium oxide catalysts can be prepared from chromium salts.
  • Reactor design: Simple batch reactors can be constructed from steel or glass-lined vessels with heating jackets.
  • Safety: Polymerization reactions are exothermic and can run away if not controlled. Temperature and pressure monitoring are critical.

A photo of a small-scale polymerization reactor setup in a workshop, showing pressure gauges, heating elements, and piping.

Plastic Shaping and Forming Techniques ​

Once polymer pellets or granules are produced, they must be shaped into usable products. Common methods include:

Extrusion ​

Molten plastic is forced through a shaped die to produce continuous profiles such as pipes, sheets, or films.

  • Equipment: An extruder consists of a heated barrel with a rotating screw that pushes plastic through the die.
  • Applications: HDPE pipes, plastic sheeting, and films.

Injection Molding ​

Plastic is melted and injected into molds to form complex shapes like containers, caps, and housings.

  • Equipment: Injection molding machines require precise temperature and pressure control.
  • Applications: Bottles, caps, automotive parts.

Blow Molding ​

Used primarily for hollow objects like bottles. Plastic is extruded into a tube (parison), then inflated inside a mold.

Thermoforming ​

Plastic sheets are heated and formed over molds by vacuum or pressure.

Recycling and Reprocessing ​

  • Mechanical recycling: Plastics are shredded, cleaned, and remelted for extrusion or molding.
  • Chemical recycling: Depolymerization back to monomers for repolymerization.

An extrusion process showing plastic pellets feeding into a heated barrel, being pushed through a die to form a pipe.

HDPE Production and Applications ​

HDPE Characteristics ​

  • High strength-to-density ratio.
  • Chemical resistance.
  • Good impact resistance.
  • Used in containers, pipes, geomembranes, and plastic lumber.

Production Steps ​

  1. Ethylene sourcing: From cracking of hydrocarbons.
  2. Polymerization: High-pressure or low-pressure processes with catalysts.
  3. Pelletizing: Cooling and cutting polymer into pellets.
  4. Shaping: Extrusion into pipes, blow molding into containers.

Practical Tips ​

  • HDPE can be recycled multiple times with minimal degradation.
  • It is resistant to many solvents and chemicals, making it suitable for storage containers.
  • Pipes made from HDPE are flexible and durable for water and gas transport.

A photo of HDPE pipes stacked outdoors, showing their smooth surface and flexibility.

PET Production and Applications ​

PET Characteristics ​

  • Transparent and strong.
  • Excellent gas and moisture barrier.
  • Used for beverage bottles, food packaging, and synthetic fibers.

Production Steps ​

  1. Raw materials: Terephthalic acid and ethylene glycol.
  2. Esterification: Reacting monomers to form oligomers.
  3. Polycondensation: High temperature and vacuum to form long polymer chains.
  4. Pelletizing: Cooling and cutting into pellets.
  5. Shaping: Injection molding or blow molding into bottles.

Practical Tips ​

  • PET is recyclable but requires careful sorting due to contamination.
  • It can be chemically recycled to recover monomers.
  • PET fibers are used in textiles and non-woven fabrics.

The PET polymerization process showing the chemical reaction between terephthalic acid and ethylene glycol.

Recycling and Waste Management of Plastics ​

Recycling is essential to reduce raw material demand and environmental impact.

Mechanical Recycling ​

  • Collection and sorting of plastic waste.
  • Cleaning to remove contaminants.
  • Shredding into flakes.
  • Melting and remolding.

Chemical Recycling ​

  • Depolymerization to monomers.
  • Purification and repolymerization.

Challenges ​

  • Mixed plastics complicate recycling.
  • Degradation of polymer properties after multiple cycles.
  • Contamination with food or chemicals.

Waste Management ​

  • Avoid burning plastics due to toxic fumes.
  • Landfill management to prevent leaching.
  • Promote reuse and repair of plastic products.

A photo of a plastic recycling facility with sorted plastic bales and shredding machines in operation.

Environmental and Health Considerations ​

  • Plastics production involves toxic chemicals and emissions.
  • Proper ventilation and protective equipment are necessary.
  • Microplastics pose long-term environmental risks.
  • Biodegradable and bio-based plastics offer alternatives but require specific conditions to degrade.

Summary and Next Steps ​

Re-establishing plastics production requires:

  • Access to raw materials (petrochemical or bio-based).
  • Knowledge of polymerization chemistry.
  • Construction of reactors and shaping equipment.
  • Implementation of recycling systems.

Refer to Basic oil processing for foundational knowledge on obtaining petrochemical feedstocks. For shaping and forming equipment, see related manufacturing sections in this chapter.

Plastics production is a complex but achievable goal that will significantly enhance the capacity to rebuild industrial society and improve quality of life in a post-collapse world.

A simplified plastics production cycle from raw materials to polymerization, shaping, use, and recycling.