Polymers standards

Polymer Standard tenacity, GPa Breaking elongation, % Modulus, GPa Density, kg/m Moisture. c regain... 

AMERICAN POLYMER STANDARDS COLUMNS FOR SIZE EXCLUSION CHROMATOGRAGHY... 

American Polymer Standards Corporation, Mentor, Ohio 44060... 

With large companies such as Waters Corp., TOSOH Corp., Polymer Laboratories Ltd., Shodex Corp., and Phenomenex Inc. and smaller companies such as American Polymer Standards Corp., Polymer Standards Service, and Jordi Associates, all manufacturing ST-DVB GPC/SEC gel, the market has become saturated with analogous columns. All the manufacturers just men-... 

Many researchers choose to buy expensive GPC/SEC columns from one of the major producers because that producer s columns had been used in the past or because of a successful marketing campaign by one particular producer. It should be noted that repacked columns can be obtained for a fraction of the cost of new columns. American Polymer Standards repacked columns are guaranteed to perform just as well as new columns from any company. When a column is repacked the only parts reused are the stainless-steel tube and end caps. This hardware is then repacked using new frits and new ST-DVB gel. Each column is individually tested in a quality control laboratory and shipped in the customer s choice of solvent. American Polymer Standards offers a column repacking service because it is a practical, inexpensive way for customers to acquire state of the art GPC/SEC columns. 

The point to consider with repacked GPC/SEC columns is the warranty. Because the columns are fragile, warranties are very important. American Polymer Standards offers a 90-day unconditional warranty on every repacked column. This type of warranty is especially useful for beginners, who would typically make mistakes within the first 3 months of GPC/SEC work. 

FIGURE 5.1 Analysis of American Polymer Standards dextran standards, two columns AMGEL Linear 300 X 7.8 mm, eluant DMSO, flow rate I ml/min, temperature S0°C, detector (DRI). 

This section deals with the procedure used by American Polymer Standards Corp. in the manufacture of GPC/SEC gels. The reaction is performed in a three-neck flask equipped with a reflux condenser, a mechanical stirrer, and a thermometer. First, prepare the water phase and then the organic phase. After mixing the organic phase into the water phase, stir at 300 to 400 rpm for 2 hr at 40°C. Heat to 70°C and continue mixing at 150 rpm for 10 hr. Cool to room temperature, (RT), dilute with water, and filter. Wash the gel with water, acetone, toluene, and again with acetone. Dry at 70°C for 12 hr, classify the gel, and package. 

DESIGN, PROPERTIES, AND TESTING OF POLYMER STANDARDS SERVICE SIZE EXCLUSION CHROMATOGRAPHY (SEC) COLUMNS AND OPTIMIZATION OF SEC SEPARATIONS... 

PSS Polymer Standards Service, D-5S023 Mainz, Germany... 

Size exclusion chromatography (SEC, also known as GPC and GFC) has become a very well accepted separation method since its introduction in the late-1950s by works of Porath and Flodin (1) and Moore (2). Polymers Standards Service (PSS) packings for SEC/SEC columns share this long-standing tradition as universal and stable sorbents for all types of polymer applications. In general, PSS SEC columns are filled with spherical, macroporous cross-linked, pressure-stable, and pH-resistant polymeric gels. 

TABLE 9.9 Experimental Parameters for Running Polymer Standards in SEC... 

Table 9.9 (6) gives some guidelines for proper SEC separation conditions when analyzing polymer standards with narrow molar mass distribution on a single 30-cm column. The conditions have to be adjusted when running industrial polymers (which are normally much wider in molar mass distribution). Depending on the width of the MMD, concentrations can be increased by a factor of 3 to 10 for such samples. As a general rule, it is advisable to keep the concentration of the injected solution lower than c [ j] < 0.2. 

FIGURE 9.9 Definition of column test parameters using a SEC chromatogram of a polymer standard mixture (PSS Polystyrene ReadyCal) and a low molar mass compound (BHT). 

Unfortunately, this value is sample and system dependent just by using polymer standards with different molar masses, different values of peak resolution can be generated. 

This equation is based on experience with liquid chromatography of low molecular weight samples displaying single peaks. Its application for the GPC of polymers, however, contains a disadvantage, as it mixes two inseparable properties the retention difference for the separation and the peak width for the contrary effect of band broadening. Such a procedure is acceptable if both effects are accessible for an experimental examination. For the GPC experiment, we do not possess polymer standards, consisting of molecules that are truly monodisperse. Therefore, we cannot determine the real peak width necessary for a reliable and reproducible peak resolution R,. This equation then is not qualified for a sufficient characterization of a GPC column. 

Commercial grades of PVP, K-15, K-30, K-90, and K-120 and the quaternized copolymer of vinylpyrrolidone and dimthylaminoethylmethacrylate (poly-VP/ DMAEMA) made by International Specialty Products (ISP) were used in this study. PEO standard calibration kits were purchased from Polymer Laboratories Ltd. (PL), American Polymer Standards Corporation (APSC), Polymer Standards Service (PSS), and Tosoh Corporation (TSK). In addition, two narrow NIST standards, 1923 and 1924, were used to evaluate commercial PEO standards. Deionized, filtered water, and high-performance liquid chromatography grade methanol purchased from Aldrich or Fischer Scientific were used in this study. Lithium nitrate (LiN03) from Aldrich was the salt added to the mobile phases to control for polyelectrolyte effects. 

Commercial narrow standards [such as poly(ethylene glycol) (pEG), polystyrene sulfonate, pAA, poly w-vinyl pyrrolidinone, dextrans] are available from American Polymer Standards Corporation, Polymer Laboratories, Polymer Standards Service USA, Toyo Soda, and others. While these standards are often not as narrow as pSty or pMMA that has been anionically polymerized, they are acceptable for narrow standard calibrations. 

In addition to polymer standards, a number of broad distribution, water-soluble polymers can be characterized on TSK-PW columns using universal calibration. These include both fully and partially hydrolyzed PVA, PAAM, PEE, and dextran. PVA, the world s largest-volume, synthetic, water-soluble polymer, was first successfully separated on TSK-PW columns by Hashimota et al. (10). In the 1980s, the use of low-angle, laser light-scattering detection... 

Gel permeation chromatography (GPC) or size exclusion chromatography (SEC) has been routinely used to estimate die molecular weight of die polymers. The molecular weight measured by GPC is relative to a polymer standard, typically polystyrene GPC is dius a relative method rather than an absolute one. For those polymers whose structure is very different from polystyrene, GPC molecular weight values could significantly differ from the real ones. In those cases, GPC values should only be regarded as a reference. 

Several assumptions were made in using the broad MWD standard approach for calibration. With some justification a two parameter equation was used for calibration however the method did not correct or necessarily account for peak speading and viscosity effects. Also, a uniform chain structure was assumed whereas in reality the polymer may be a mixture of branched and linear chains. To accurately evaluate the MWD the polymer chain structure should be defined and hydrolysis effects must be totally eliminated. Work is currently underway in our laboratory to fractionate a low conversion polydlchlorophosphazene to obtain linear polymer standards. The standards will be used in polymer solution and structure studies and for SEC calibration. Finally, the universal calibration theory will be tested and then applied to estimate the extent of branching in other polydlchlorophosphazenes. 

SEC or gel permeation chromatography (GPC) is one of the widely used chromatographic techniques [56,57]. In contrast to the already discussed colligative and scattering methods it is not an absolute method and requires proper calibration with some known polymer standards. One obtains not only the average molar masses (M , Mw, Mz) but the complete molar mass distributions. 

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