The Expert's Experts

Polymer Solution Incorporated’s Expert Team is hired by leading companies. This is a direct example of how our scientists are used as an extension of top organizations.

		PSI works for the top Fortune 100 companies. Providing specialized expert services and independent testing serves to advance important programs. "They are not a routine lab, you get real answers."
		PSI provides GMP-compliant analysis to the top medical device manufacturers and pharmaceutical companies. "They are an extension of our R&D. They are on our team; they don’t just work for us."
		In cases of patent infringement, industrial espionage, product or manufacturing defects, and personal injury, PSI scientists perform critical analysis and present expert communication on behalf of the largest law firms. "Jim is great as an expert witness, he is great at communicating very technical information in a way that the jury can understand."
		And here is the really cool part; we also work on behalf of rising stars, start-ups, and a vast array of smaller companies. These companies may not have the notoriety of the "Top 10" but they nevertheless serve a critical function for their employees and local community. We are excited to partner with companies of all sizes, to serve their materials analysis needs. What we are doing: "analyzing, understanding, explaining, and solving material science problems for clients."

Molecular Weight Analysis

Because the molecular weight of plastic and rubber materials controls the processing and performance properties, this is one of the most sought analyses. Scientists and engineers in any field that uses polymer materials want to know the molecular weight and molecular weight distribution of the polymers. The testing can be for quality assurance, comparing various batches, lots, or sources, or to contribute data to a failure analysis. There are many methods that can be used to determine the molecular weight of polymer materials.


Dilute Solution Viscosity

By measuring the flow time of a polymer solution through a precision capillary, we can calculate the viscosity which relates to molecular weight. If your plastic or polymer sample can be dissolved, we can measure the viscosity. High temperature, fluorinated solvents, and aromatic solvents are routinely employed by us. Also, we have many ways of removing fillers from samples so that more accurate results are obtained by excluding the non-polymer component.

Dilute solution viscosity is a frequently requested method of analysis, especially for quality control purposes. For example, medical plastics are analyzed as raw material, after molding, post-sterilization, as part of shelf-life stability tests, and contribute to R&D and product development programs. DSV allows scientists and engineers to track the molecular weight as a function of the phases of the product life. Read more about dilute solution viscosity. . .


Gel Permeation Chromatography

Gel permeation chromatography (GPC) and size exclusion chromatography (SEC) are two names for the same analytical method. GPC and SEC are used to separate molecules based on size in solution. These are powerful methods for fully characterizing the molecular weight distribution of samples. Instead of giving a single value, as dilute solution viscosity does, the full distribution curve is obtained.

Typically, we are verifying molecular weight as a function of process steps. Process steps can include raw material, post processed components, and sterilized, stored, artificially aged samples, or field-returns. A powerful feature of GPC and SEC is that subtle shifts in molecular weight can be precisely documented. And, these techniques can be used to determine if a polymer material is actually a blend of several molecular weight distributions. A blend of two distributions, for example, is called bimodal. To influence processing, properties, or as a result of utilizing regrind and recycled resins, multi-modal molecular weight distributions can be present in samples. GPC and SEC tell the story well. Read more about gel permeation chromatography or size exclusion chromatography (GPC and SEC). . .


Melt Flow Index Testing

The Melt Flow Index (MFI) is a measure of the ease of flow of molten thermoplastic polymer. It is defined as the mass of polymer in grams flowing in 10 minutes through an orifice having a specific diameter and length. The extrusion force is applied via prescribed weights at polymer-specific temperatures given in ASTM Method D1238 and ISO 1133. During an MFI determination the actual “extrusion time” is not exactly 10 minutes. However, the exact mass of extruded polymer and the exact time required to obtain that mass of extrudate are recorded. Then, a simple calculation normalizes the MFI value to the customary units of "grams-per-ten minutes."

For example, if 6.3525 grams of polymer is extruded in 7 minutes and 13 seconds then 6.3525 grams were extruded in 7.217 minutes.

So, the calculated MFI value is: 6.3525/7.217 x 10 = 8.8.

The MFI for the thermoplastic polymer sample is reported as 8.8 g/10-min.

The melt flow rate is an indirect measure of molecular weight, high melt flow rate corresponding to low molecular weight. Synonyms of Melt Flow Index are Melt Flow Rate (MFR) and Melt Index (MI). Read more about Melt Flow Rate. . .


Shear Rheometry

Shear Rheometry measures the melt viscosity, creep, and stress relaxation responses of polymers as functions of time, temperature, and force, using parallel plate or cone-and-plate configurations. Polymer samples can be evaluated from sub-ambient temperatures to high temperature. As a result, the rheometer is able to document the properties of plastic and rubber materials in the solid state, through the glass transition temperature, and into the melt region. It is the melt region that is used to calculate the molecular weight of the sample.

An additional powerful feature of shear rheometery is the ability to measure properties as a function of frequency. Frequency is an important experimental parameter because many polymers are not used in a static environment but rather are subjected to mechanical frequencies during use. The rheometer allows the scientist or engineer to determine material properties as a function of time, temperature, and frequency. This ability provides a detailed multi-dimensional analysis of plastic and rubber materials; useful for fundamental analysis, modeling, material comparisons, and failure analysis. Read more about Shear Rheometry. . .

The Expert’s Experts
We realize that we are partnered with the top companies in virtually every business category. Top companies achieve extraordinary success by being experts in their field. And, they partner with leading experts.

Polymer Solutions Incorporated is organized around specialized areas of expertise and employs highly skilled Experts eager to partner with you.

This issue focuses on some examples of how PSI is the expert’s Expert.

Molecular Weight Analysis
And, molecular weight analysis continues to be a topic of great interest to clients. So, in this issue we offer useful information about molecular weight and how it is measured.

• Dilute Solution Viscosity
• Gel Permeation Chromatography
• Melt Flow Index Testing
• Shear Rheometry

You can get even more information about these important analytical methods and others by visiting our web-site or by talking to one of our Experts.

Cool Pics
Also in this newsletter is the very popular section, Jay’s Cool Microscopy Pics of the Month!



Bonus Content This Month:

1. Who’s Jay?
2. A Few Words From The Founder

He is our microscopy and physical testing expert. Virtually every day, he is capturing images of interesting subject matter, usually for clients, sometimes just because he can.

Because of our diverse client base and his interest and expertise, Jay captures a wide range of images; digital photographs, optical microscopy images, and very high magnification electron microscopy images.

There’s more to the man than his images. Think you know Jay? Take our 10 question quiz and find out. Five of the statements are true, five are not. Which ones are true?
First 10 respondents with the correct answers receive a $10 Starbucks® Gift Card.

While leading the PSI Microscopy Lab, Jay works with some extremely interesting materials. Many are even more intriguing at high magnification. In this month’s edition of the PSI newsletter, Jay shares some of his favorites that include:

(Click on each image to view it in higher resolution.)


1. EDS (Energy Dispersive Spectroscopy) Map of wood coated with sealer and shellac.


2. SEM image of the wing of a stink bug at around 3,000x magnification. No stinkbugs were harmed in the making of this image.


3. TEM image of a PLA-PP copolymer at 16,000x magnification.  The PLA phase was stained and appears as the darker color in the image.