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Engineering Plastics Solutions, Ltd.
34540 Richland Court
Livonia, MI 48150

Contents
• Personal photo
• Explanation of services(includes correlation of
design/process/morphology/composition/root cause)
• Curriculum vitae
• Examples of types of data provided and format
– FTIR
– TEM
– LM
– Report outline
– Processing analysis
– Materials selection and assisting applications development
• Cost structure
• Work examples from resume

Analysis of materials and processes

The following slides provide a step-by-step analysis of specific
issues resolved for a client that required understanding of the
material, the molding process, and the secondary process of
plating on plastic.
Situation:
– Timing was critical; results needed in next 5-7 days
– Very little money in budget for outside testing
– No money available to have me travel to see process

Procedure:
– Photograph all samples and label them
– Use light microscopy to inspect and document areas of interest
– Perform FTIR analysis on surfaces, reference areas, and raw pellets

Plated parts analysis
(4.0mm)
~4000 microns Example of a bubble in a plated PC/ABS wheelcover part.
The part was first examined using Light Microscopy(LM),
at about 25x magnification. The sides of this elongated
bubble are partially collapsed or sucked in, creating a
small ridge along the length.
~800

0mm
( 0.8
micr
ons

)

The top portion of the bubble was removed with the plate
layer. The surface under the bubble shows a glossy
interior compared to the roughened surface surrounding
it. The elongated bubble and glossy interior indicates that
there were volatiles in the melt during injection and they
created a void just below the surface. The surface defect
was thick enough to survive etching and became plated.
The collapse of the sides of the plated bubble indicates
that the original bubble skin was very thin and may have
collapsed during or after plating.
s
on
icr
m
0 )
00 mm
2 0
2.

Molding defects found

Looking at the plastic under the plating in different areas of
the part showed a major processing issue. The circled area is
a sliver of material that easily separated from the material
under it when the spoke was cut on a bandsaw. Following the
gating and material flow, it was determined that the material
flow separated and did not knit back together. This is an
indication of improper mold or melt temperature, or both.
The accompanying photo is a magnification of the backside of
this sliver.
Surface of sliver that
0m
~ 10

m

pulled away from the
spoke. Note that the
N o nded
bo a
surface is smooth with
n-
are

no indication of fusion
Cross section through part
to the rest of the part
compared to the
upper right region. A
further analysis of this
surface by FTIR (see
next slide) leads to an
interesting finding.

FTIR analysis

Comparing the smooth
surface, material .
008”-.020” directly
beneath the smooth
surface, the non-smooth
surface area, and the
material below the non-
smooth surface gives a
good sample
comparison.
There is definitely some
type of “oily” substance
on the glossy surface,
and it probably
prevented the melding
together at the flow
fronts.

Final conclusions
• There was a definite oily substance on the sliver that was under the plating.

• This oily substance is similar to compounds used in mold release agents, but are also
found in the PC/ABS formulations as mold release or flow enhancers.

• There was no indication of degraded rubber in the FTIR analysis comparisons which
indicates the material was not thermally degraded.

• The bubbles in the plating were voids caused by trapped gases or air in the melt at the
surface. Low melt temperatures or mold temperatures could indicate trapped air at the
surface.

Recommendations
• Investigate the use of mold release at the molding machine. No mold release should be
sprayed on the tool for best plating results.

• Analyze different lots of material or between material suppliers to be sure of consistent
levels of additive package.

• Investigate the temperature settings for the melt and the mold. Use a pyrometer to
measure melt and mold temperatures. If below mid-range of supplier recommended
settings, use step-wise increases to the maximum if required.

These examples of overlaid spectra of a TPO pellet surface and cross-section
show the very minor differences in compositional peak heights being analyzed.

Overlaid spectra of chloroform, heptane, and acetone extracts from a TPO (TPO-1) to show
how different additives and rubbers are revealed that cannot be seen in the spectra of the
whole material. These may only be 0.1 to 10% of the material formulation.

Overlaid spectra of the heptane extracts show differences in one of the TPO’s
(TPO-1,circled area) showing it has a styrene-based rubber additive not in the other TPO’s.

Expanded scale of overlaid spectra of the heptane extracts show differences in one of the
TPO’s (TPO-1,circled area) showing it has a styrene-based rubber additive not in the other
TPO’s.

There are a number of issues that confront the molding community today, but one
of these that can be very aggravating and costly is molding defects. These are
quality issues that may come and go. They can be isolated to certain tooling, certain
lots or grades of material or, even isolated to certain molding equipment.
If you are a high volume user of material, sometimes you have access to the
vendor’s lab services. If you are a lower volume user or spot buyer, you may not
have these available, or only at premium prices and at a lower priority.

surface splay “tiger stripes” discoloration short shots

gate blush dull spots bubbles/ voids “juicing”

streaking glossy spots burn marks delamination

I tried to create examples of the defects just using the
.ppt tools because I think it will take a bit of time to get
actual photo examples. The middle row are pretty
representative except the “dull spots”; it’s hard to show
a glossy surface with a few lower gloss spots. The tiger
stripes can be seen in some of the attached photos.

Blister in surface of PC/ABS plated wheelcover

Pits in surface of chrome plated PC/ABS – 20x magnification

Photomicrograph(40x) of surface under chrome plated
PC/ABS. Darker areas are where etch was not as effective
and adhesion was much lower. Possibly due to cold material
getting pushed to surface and creating different density.
[color is actually a gray, yellow is due to angle of lighting]

Photomicrograph (20x) of a pit
in the part surface caused by
peeling off chrome plate from
plated PC/ABS. Note that only
top left area has ductile failure
and the fairly sharp and
irregular edge below it. This
indicates that there was poor
cohesion in the material at this
area. It may be that cold
material came to the surface
and didn’t bond with the hotter
material, or that there could be
some chemical that is at the
interface of the melt that
prevented adhesion when the
melt fronts came together.
[again, the color is gray;
lighting caused the yellowness
and helped increase the
contrast]

This is an example of
wrinkled plating on a PC/
ABS caused by a couple
of issues. Between
areas 4 and 5 are dark
streaks where there was
no plate adhesion. There
appears to be a crack by
area 4 as well.

Another crack seen in plated PC/ABS part after cutting a
cross-section through one leg of the part. Circled area
shows where the material pulled apart with no effort along a
knitline. Again, the evidence of cold material and uneven
flow, or a chemical at the surface of the flow front
preventing good melding of the flows.

Photomicrograph
(20x) from
underneath
cracked surface
area along the
length of the
crack.

Smooth area showing no melt front cohesion; Ductile fracture area under the crack
caused by chemical contamination at the flow front. showing good material cohesion.
Sharp line of demarcation between
the areas indicates possible
chemical contamination.

Note: photo is
not black and
white; just
background is
white and gray
and part is a
flat black color

“Tiger striping” in a TPO molded fascia. Can be caused by material “stick-slip”
against the tool surface because of material formulation, or by minor variations in
the melt pressure causing different material velocities and different material
densities. It can also be a combination of these issues.

II C. - Spiral flow with Intellimold® pressure control

What is Intellimold pressure control?
•Intellimold is a technology for injection molding that controls the speed of the ram based
on how much pressure is needed to keep the material flowing in the tool during the fill-
pack-hold cycle.

•Then nozzle and cavity are fitted with pressure sensors, and these signals are used to
compute an internal melt pressure (IMP) which is translated into a voltage to control the
injection ram via the control valve(or torque drive on electric models)

•The IMP control signal ( the set pressure) is compared to the nozzle and cavity pressure
every millisecond to maintain a constant melt pressure during the continuous fill-pack-
hold cycle; there is never a switching of control signals, as in some other processes such
as RJG.

•The second set point is the process factor (PF), which tells how the injection pressure
needs to drop off (or increase) as the cavity pressure increases, to create a desired
packing pressure. AT THE END OF FILL, nozzle pressure + cavity pressure = IMP, so
the nozzle pressure curve will start to decrease as soon as the cavity pressure starts to
rise. The final pack pressure is determined by the PF. In these spiral flow samples, the
PF= -1, so the nozzle pressure decreased 10psi for every 10psi increase in the cavity
pressure.
23

II C. – Spiral flow analysis

Spiral flow utilizes a channel cut into a mold of a given
length, width, thickness, and gate size. The tool is
temperature controlled and placed in an injection molding
machine (IMM) which uses hydraulic pressure to force the
material through the sprue, runner and gate into the channel.
The dimensions on the channel are:
Length = 779mm
Width = 6.0mm
Thickness = 2.0mm
Gate = 1.0mm diameter

gate
End of fill (EOF)
=779mm 24

Overlaid spiral flow pressure curve comparisons at different melt pressures [do
not use the name of the sample on any graphs, charts, spectra, etc. unless
specifically told it is okay. You may substitute “Material A”,etc.]
Can use “R_TPO”
as name

Cavity sensor not
zeroed

Intellimold vs. Conventional Molding
Molded PP copolymer of 12MFI in
two-cavity chip tool. Parts are
60mmx90mmx1mm on the upper
chip, and 60mmx90mmx2mm in the
bottom chip. Tool was shot
conventionally controlling the fill
based on shot volume (short shot)
and using full hydraulic pressure.
Notice the inclusions of air bubbles
as “fingers” or voids.
The lower series show the filling of
the chips using the same shot
volumes but controlling the injection
pressure with the Intellimold
process control. No voids are
present, and the thicker chip is
filled, even though the same shot
volume was used.

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