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M&M Plastics (Environmental Impacts (Volatile Organic compounds (VOC),…
M&M Plastics
Environmental Impacts
Thermoplastics
efficient to recycle
parts should be designed in a single material if possible and with recycling & disassembly in mind.
some are harmful in production
for example
polyester & epoxy
contain styrene
are known as pollutants and are toxic
Volatile Organic compounds (VOC)
avoid inhaling
give gass off during lifetime
lowers air quality indoors
Manufacturing Techniques:
Blow Molding
3 Ways:
Extrusion Blow Molding (EBM)
Low:
Tooling costs
Running costs
used for:
medical
chemical
veterinarian
consumer industries
wide range of materials
complex & intricate shapes manufactured
Containers of:
3ml to 220L
Materials used:
PP
PE
PET
PVC
Costs:
Least expensive
Injection Blow Molding (IBM)
Higher demands such as:
Medical containers
Cosmetic packaging
More control over:
wall thickness
neck details
Containers of:
3ml to 1L
Materials used:
PP
HDPE
Costs:
2x as much as EBM
Injection Stretch Blow Molding (ISBM)
used for:
produce high quality glass clear PET containers
such as:
water bottles
agrochemical
Personal care
general chemicals
bathroom & toilet porducts
Gives superior mechanical properties
stretching the pre-form during blowing increases mechanical strength
Containers of:
50ml to 5L
Materials used:
PE
PET
Costs:
most expensive
Related Processes
Thermoforming
Rotation molding
Injection molding
Mainly for:
large hollow volumes with thin walled walls
Materials to be used:
All thermoplastics
Injection Molding
Related Processes
For:
Rapid prototyping
identical parts
with tight tolerances
high volume productions only
excellent surface finish
Variations of Injection Molding:
Gas-assisted
multishot
in-mold decorating
Typical applications:
automotive
industrial & house hold products
garden furniture
hosing of consumer electronics
Quality
due to:
high pressure
good surface finish
excellent repeatability
resolidified polymers tends to shrink and wrap
Sink marks:
occur on the surface opposite a rib detail
weld lines
material is forced to flow, or around obstacle
Design opportunities
A simple split mold
cheap
complex shapes
expensive
In-mold & insert film decorating
integrated to cycle to make it cheaper
metallic, pearlescent, thermochromic, photochromic effects
Multi shot injection molding
can combine:
up to 6 materials in 1 product
density, rigidity, colour, texture, different levels of transparency
Design Considerations
Involves:
designers
polymer specialists engineers
tolmakers
modelers
Mold
high temperatures
high pressure
problems
shrinkage
stress build up
in areas with sharp corners
draft angles should be at least 0.5º
Material insertion
start in the thickest wall section
finish in the thinnest wall section
Ribs
increase strength of part
reduce wall thickness
not exceed 5x the wall height thickness
recommended to use:
lots of shallow ribs
than fewer deeper ribs.
Compatible Materials:
all thermoplastics
certain:
thermosetting plastics
metal powder
polymer matrix
Costs
tooling costs are very high
small parts very rapidly
cycle time:
small parts:
30-60s
large parts:
longer times
Labour costs are low
Environmental impacts:
thermoplastics can be recycled
require 50% virgin material
Types of plastic:
Bioplastics
molded without petrochemicals
Can be:
Starch based
Cellulose based
natural rubber materials
Fully biodegradable
less energy to produce
Synthetic
Thermoplastics
Can be reprocessed with virgin material
Regrind
limited to less than 15%
some materials may contain higher %
Further categorized by:
Molecular structure
Weight
Thermoset
have a permanent cross-links
more durable molecular structure that is more resistant to:
Heat
Chemicals
produced by petrochemical industry
Grades are possible
modified to break down within a period of time
1-5 years
possible by addition of bioactive compounds
do not affect physical qualities
Additives Fillers & Reinforcement
Used to improve:
Mechanical Properties
Colour
made up of:
carrier resin coated pigment
added to raw material during process
Determined by:
International standards:
Pantone
RAL
Other effects:
Metallic
Pearlescent
Thermochromatic
Photochromatic
Photoluminescent
Electrical Conductivity
Mold Flow
Antimicrobial Properties
Material resistance to:
Fire
UV
Chemical Attack
Fillers
Thermoplastics
can be:
injection molded
extruded
compression molded
Types used to improve mechanical properties:
Fibers
Talc
Minerals
Textiles
Thermosets
can be:
compression molding
composite laminating
new techniques better suited (less labour costs)
Resin transfer
Resin Infusion
3D thermal laminating
types:
glass
aramid
carbon
hemp
jute
They have superior:
strength for their weight
different grade
different uses
Notes on Manufacturing
Thermoplastics
Granulated form
Sheet material
needs extra processing
more costs
Drawn fibers
Blown Film
Amorphous materials
do not have sharp melting point
therefore Thermoforming is suited
Crystalline materials
have a sharp melting point
more suited for:
thin wall sections
complex features
Thermosets
Cure at room temp.
Polyester
Vinyl ester
Epoxy (EP)
Polyurethane (PUR)
mixed with:
catalyst or hardener
Powdered, liquid or solid
are heated
trigger the formation of cross-links
Cured in a mold