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

~80

0 mic

ron

s ( 0.

80 mm

)

~4000 m

icrons (4.0m

m)

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.

2000 micr

ons

2.0mm)

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.

Plated parts analysis

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.

~10

0m m

Cross section through part

Non-

bonded

area

Surface of sliver that pulled away from the spoke. Note that the surface is smooth with no indication of fusion 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.

Molding defects found

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.

Examples of FTIR

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.

surface splay “tiger stripes” discoloration short shots

gate blush dull spots bubbles/ voids “juicing”

streaking glossy spots burn marks delamination

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.

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.

~80

0 mic

ron

s ( 0.

80 mm

)

~4000 m

icrons (4.0m

m)

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.

2000 micr

ons

2.0mm)

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.

Plated parts analysis

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.

Smooth area showing no melt front cohesion; caused by chemical contamination at the flow front.

Ductile fracture area under the crackshowing good material cohesion. Sharp line of demarcation between the areas indicates possible chemical contamination.

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

“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.

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

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 = 779mmWidth = 6.0mmThickness = 2.0mmGate = 1.0mm diameter

gateEnd of fill (EOF) =779mm 24

Cavity sensor not zeroed

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

Intellimold vs. Conventional MoldingMolded 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.