Lec 11: Plastics Industry

Plastics

synthetic or semi-synthetic materials primarily composed of polymers, which are long-chain molecules formed by linking smaller molecules called monomers.

most conventional plastics originate from petroleum and natural gas-derived chemicals

From a CPI perspective, plastics represent a major downstream petrcohemcial industry because…

Raw materials → Feedstock preparation → Petrochemical processing → Monomer production → Polymerization reaction → Polymer resin production → Compounding and Additive Mixing → Plastics processing operations → Finished plastics products → Applications and Markets

Overall transformation pathway of the plastics industry

• Polymer matrix

• Additives

• Fillers

• Reinforcements

• Stabilizers

• Plasticizers

• Colorants

A plastic material consists mainly of?

• Petrochemical Feedstock Industry

• Polymer Manufacturing

• Plastic Processing Industry

• Plastic Additives Industry

• Recycling Industry

What are the several major sectors of the plastics industry?

Packaging

largest plastic market sector

Construction

industrial sector that provides durable materials

Automotive

industrial sector concerning with vehicle weight reduction

Electronics

industrial sector which is concerned with providing insulation and protection

Healthcare

industrial sector concerned with enabling sterile disposable products

Agriculture

industrial sector which is concerned with improving productivity

Bio-based plastics

industrial trend aiming to reduce fossil dependence

Processability

characteristics of plastics pertaining to it being easily molded into shapes

Molecular weight

controls strength and toughness

Chain branching

influences density and flexibility

Crosslinking

produces rigid structures

Crystallinity

affects strength and melting behavior

Additives

modify mechanical and processing properties

Thermoplastics

these plastics soften when heated and harden when cooled, they can be repeatedly processed

Polyethylene

flexible and chemical resistant | packaging films and containers

Polypropylene

high strength and chemical resistance | automotive parts and packaging

Polyvinyl Chloride

durable and versatile | pipes and cables

Polystyrene

lightweight and rigid | packaging and insulation

Polyethylene terephthalate

Strong and transparent | beverage bottles

Thermosetting plastics

Thermosets form permanent crosslinked structures and cannot be remelted (ex: epoxy, phenolic resin, melamine formaldehyde)

Epoxy

high strength and adhesion | coatings and composites

Phenolic

heat resistant | electrical components

Melamine

hard surface | laminates

Elastomers

plastics that exhibit rubber-like elasticity (ex: natural and synthetic rubber, silicones), applied in tires, seals and flexible tubings

Engineering plastics

these plastics possess enhanced mechanical and thermal properties, examples are polycarbonates, ABS, nylon, and PEEK, applied in aerospace components, automotive systems and electronics

Crude oil

_____ → refining, cracking, separation → ethylene, propylene, aromatics

Natural gas

______ → gas processing, steam cracking → ethylene, propylene

Ethane

_____ → steam cracking → ethylene → polyethylene

Benzene

_____ → aromatic processing → styrene, engineering plastics

Salt

______ → electrolysis → chlorine → PVC

Biomass

_______ → fermentation/chemical conversion → bioplastics

Steam cracking

one of the most important chemical processes in plastics manufacturing which converts hydrocarbons into basic petrochemical building blocks

Ethane/Naphtha feed → high temp furnace → thermal cracking → quenching → compression → separation → monomer products

Process flow of steam cracking

ethylene glycol + terephthalic acid

What is the monomer used to produce PET?

acrylonitrile

What is the monomer used to produce Acrylonitrile Butadiene Styrene (ABS)?

Condensation polymerization

What is the manufacturing route used to produce PET and nylon?

Polymer synthesis

What is the manufacturing route to produce polycarbonates?

optical products and electronics

What are polycarbonates used for?

fibers and engineering parts

What are nylon used for?

Polyethylene

the largest volume plastic produced globally

Low-density Polyethylene

flexible, low density and is used for films and packaging

High-density Polyethylene

strong and rigid used for containers and pipes

Linear LDPE

flexible and tough, used for stretch films

Polypropylene

high chemical resistance, low density and high fatigue resistance, used for automotive components, food containers, medical products, and fibers

Polyvinyl Chloride

unique because it contains chlorine derived from salt, used for pipes, electrical insulation, flooring, and construction materials

Polyethylene terephthalate

produced through condensation polymerization and are used in beverage bottles, food packaging and polyester fibers

1. Polymer manufacturing

2. Plastic Product Fabrication

What are the two main stages of plastic production?

Feedstock preparation

this step’s purpose is to comvert petroleum and natural gas resources into useful chemical intermediates

Monomer production

to manufacture reactive molecules required for polymer formation

• addition polymerization

• condensation polymerization

• copolymerization

three major industrial polymerization methods

Addition polymerization

unsaturated monomers combine without eliminating small molecules

Condensation polymerization

monomers combine while eliminating small molecules such as water and methanol

Copolymerization

two or more monomers are polymerized together (ex: ABS, SBR rubber), gives improved strength, better chemical resistance, and modified processing behavior

Slurry/gas-phase polymerization in a fluidized-bed reactor

PE is polymerized in what process and reactor type?

Catalytic polymerization in a loop reactor

PP is polymerized through what process and reactor type?

Suspension polymerization in a batch reactor

PVC is polymerized through what process and reactor type?

Bulk polymerization in a continuous reactor

PS is polymerized through what process and reactor type?

Condensation polymerization in a melt reactor

PET is polymerized through what process and reactor type?

Polymer compounding

After polymerization or polymer production, this step is next.

Plasticizers

increase flexibility

Stabilizers

prevent degradation

Fillers

improve strength and reduce cost

Pigments

provide color

Flame retardants

improve safety

Plastic Processing Operations

After additives, this next step is where polymer resins are converted into usseful products through manufacturing processes.

Extrusion

continuous shaping of molten polymer through a die

Injection Molding

molten polymer is injected into a mold cavity

Blow Molding

used mainly for hollow products such as bottles and containers, it is when air pressure expands heated plastic inside a mold

Thermoforming

heat plastic sheet, form over mold, and cools and removes product; applied in food trays and packaging

• Steam cracking

• Polymerization

• Extrusion

• Injection molding

• Drying

What operations are energy-consuming in the plastics industry?

• furnace efficiency

• heat exchanger performance

• cooling systems

• process integration

What do chemical engineers optimize to reduce energy consumption?

Residence time

Which parameter in the polymerization reaction determines conversion and molecular weight?

Temperature

Which parameter in the polymerization reaction controls reaction rate and molecular structure

Pressure

Which parameter in the polymerization reaction influences polymerization conditions

Catalyst activity

Which parameter in the polymerization reaction controls productivity and polymer properties

batch reactor

reactor type used in PVC production

CSTR

reactor type used in specialty polymers

fluidized bed reactor

reactor type used in PE production

loop reactor

reactor type used in PP production

Polymerization reactions can release significant heat

What is the heat transfer challenge in the plastics industry?

Electrical energy → heater bands → polymer melting → shaping through die → cooling

Polymer processing during extrusion flow

• non-Newtonian fluids

• melt viscosity, pressure drop, flow resistance, pump selection

• extruder design, polymer pipelines, injection molding system

Polymer materials often behave as ______ thus engineering considerations include and ______ are applied.

Viscosity

this parameter determines processing difficulty

Shear Rate

parameter that controls flow behavior

Melt Strength

parameter that influences product formation

Elasticity

parameter that affecys final product quality

• effective mixing

• heat removal

• controlled residence time

• catalyst management

A polymer reactor must provide:

Hopper

part of the extrusion which feeds polymer pellets

Screw

part of the extruder which melts and transports polymer

Barrel

part of the extruder which provides heating

Die

part of the extruder which shapes the product

Cooling system

part of the extruder which solidifies the product

Injection Molding Equipment

this equipment is used for producing complex-shaped plastic components; its main components are injection unit, mold system, hydraulic/electric drive, cooling systems

Molecular weight

Quality parameter that determines mechanical properties and is tested through gel permeation chromatography

Melt flow index (MFI)

Quality parameter that measures processability and is tested through the melt flow test