|
|
Silveys' Plastic Consulting
Notes and Ideas on Plastic Topics |
|
| August, 2008
Vol. 2 No. 8 |
|
|
Greetings!
Hallo!
Summer is in full swing up here in the Northwest with 3 days plus of 100 F/ 39 C weather. Actually it is nice yet when the wind stops in the evening it can warm back up.
So hopefully all are enjoying the times and Olympics if you enjoy all the sports and can catch it on the net or the TV if the broadcast is at a decent hour. Myself I must confess to being hooked on the Olympics and enjoy the action as limited as it is in our viewing area.
Education seems to have been the theme this past month for my work load, and it was great. By great I mean that people actually wanted to learn, and asked questions. The comprehension level was up there in that some actually now understand that even though the machine can document the settings it does not document the results. Further having the results tends to make setting it up for the same results easy.
The topic this month is on color and is a part 1 as there is so much. When I started in plastics oh so long ago dry pigments were used in the shop (still available today) and some with heavy metals, and I can still remember the rainbow going down the drain as a shower was taken. Today we have concentrates, micro pellets, and liquid and if you can afford it pre-colored materials to use.
Enjoy the article and the summer; take stock of your own education level and how to continue to learn as the change we have all seen is a constant and demands of our customers and clients means that we need educate them as well as ourselves.
Enjoy, if you want to discuss training give a call, email or note, as hopefully all are getting prepared for the influx of work as things change.
TA
Steven
Silveys Plastics Consulting
360-882-3183
http://archive.constantcontact.com/fs034/1101663388820/archive/1102138661635.html
|
| Colorants |
|
A starting point.
by SL Silvey
|
Definition: Color: 1. the quality of an object or substance with respect to light reflected by it, usually determined visually by measurement of hue, saturation, and brightness of the reflected light.
In a general terminology the color we see is really not the color of the product but a reflectance back to our eye. Further a color in a plastic part (or any object) can be achieved in various ways and with various pigments and or dyes in which the colored product can look the same in one light but completely different under another light source. This phenomenon is called metamerism and was more prevalent years ago prior to the usage of all the colorimeters and computers available today. It is still an issue, and something to be aware of.
Color is added to plastics as any additive is either at the press or by a compounder or supplied directly from the manufacture which compounded it in during the resin manufacture.
The basics: Dyes or pigments? Dyes are soluble within the plastics we are using and become part of them while pigments are insoluble and are dispersed through the polymer matrix. Understanding this can help in that a dye dissolves within the polymer, thus no particles to be seen, while pigments are suspended within the matrix of our material.
Also dyes can equal bright, clear transparent colors while pigments are basic for deep, saturated opaque or translucent colors. Dyes are not for all materials as heat stability and a tendency to migrate limit their use.
In recent years, with the elimination of heavy metals the light fastness and brightness has been an issue. Other issues are the stability to heat during processing and the moisture within the pigments as organics tend or have issues with clumping together if not dried properly, thus when processing they may contain a big chunk of pigment which does not disperse properly.
Masterbatches: (color concentrates) these are pelletized colorants comprised of pigments and or dyes in a carrier that is compatible with the resin to be colored. Hopefully the dispersion within the concentrate is good.
Pre-colored: the material is already colored to the specific color and can be certified as meeting some standard such as flammability, or color stability.
Dry color / powder: this is using a specific pigment or pigment blend to achieve the color necessary. This is the cheapest way to color from a cost standpoint but higher in safety due to dust control, additive means and dispersion within the material. In small shot sizes, or small runs of material it can work, but working with powders requires a complete understanding of powders and what can be done. For example drying in a desiccant dryer with air flow is an issue as you could blow off the pigment and contaminate the dryer beds. There are currently new powders on the market referred to as dustless which disperses the pigment in a wax carrier.
Liquid color: Basically the dye or pigment is disperses within a liquid and is pumped into the material. For heat sensitive colors this is a good method as there is only one heat history. It is also with proper equipment and understanding a great way to run multiple colors.
When processing the following issues can concern the processor:
1- Compatibility, this is not only for the carrier in a concentrate but also what was used within the concentrate to help disperse the color within. For example was a steric acid used and the material to be processed is an Acetal which will react with steric acid.
2- Heat stability of the colorant. Has there been communication as to the temperature the material is actually processed at? The higher the heat stability of the colorant the more costly the pigment. Are there streaks that look as if they are degraded polymer?
3- What pellet size are you using? When talking about a let down ratio and the fact that 1 pound of concentrate is disperse through 100 pounds of resin the issue remains as to dispersion through the raw materials and than the mixing of said dispersion. Though amounts do not change (weight of additive) if the particle to be dispersed is smaller in size than initially the dispersion is greater thus the mixing or incorporation into the resin is better.
4- The screw, shot size and cycle. The screw can be tested for mixing compatibility and using at least 25% of barrel is good. What is the cycle of our process, short, quick screw recovery to maintain a cycle time may not allow time for mixing of colorant.
5- Let down and or mix ratio comprehension. In many ways a set pigment or colorant level must be added to the resin. If the let down changes it means we need add more or less concentrate to our resin. What this really means is that the pigment or dye level within the actual pellet or concentrate pellet is changing. Thus how the mixing occurs may need to change when the let down ratios change.
If color is important to the end product than considering what the color is from the onset of the design and tooling design should be done. In some colors gate location and weld lines have eliminated the use of that colorant for an end product or in other cases a new and modified tool needed to be design to take care of the issue.
S.L. Silvey
08-2008
Silveys Plastic Consulting |
| Services Provided |
|
What we can do, don't see it give a call and we can discuss! |
- Services can be over the phone, internet, Skype, Microsoft Messenger, fax, plant visits.
1- Troubleshooting: assisting in the processing
a. At your plant,
b. Over the phone, internet, Skype, MS Messenger
2- Plant Audits,
3- Training / education programs.
4- Mold optimizations / new mold trials
5- Other services
a. program management
b. material development ( oversee with external assistance)
c. testing of materials (oversee with external sources)
d. BTI MeltFlipperŽ ( distributor for)
e. Expert witness
MeltFlipperŽ, is the registered trade mark of the Beaumont Technologies, Inc
http://archive.constantcontact.com/fs034/1101663388820/archive/1102138661635.html
|
| Distribution contact for |
|
When size, stress and repeatability definitely have to be identical from 1 cavity to 96 cavities in the parts, give me call, or give BTI a call direct and tell them Steve sent ya.
Beaumont Technologies, Inc.
2103 East 10th Street
Erie, PA 16511
Telephone 814-899-6390
Fax 814-899-7117
www.beaumontinc.com
|
|
|
|
Steven Silvey
Silveys' Plastic Consulting
PO BOX 5216, Vancouver, Wa 98668
360-882-3183, cell 360-606-1156, fax 360-882-3184
|
 |
|
|
|
|
|
