Requirement final.pdf

STATEMENT OF REQUIREMENTS

TITLE: Cryogenic Ball Mill for Grinding Polymer Materials

I. BACKGROUND INFORMATION

The Materials Measurement Science Division (MMSD) has the need for a benchtop ball mill with cryogenic capability [liquid nitrogen (LN2) cooling]. The major use for this mill will be to grind plastic materials (polymers and plastics). Cryogenic capability is required to freeze plastic materials to temperatures below their glass transition temperature (Tg ). At temperatures below Tg, plastic materials lose their plasticity and become brittle. After they become brittle, they can be fractured (ground or milled) into fine particles. MMSD is particularly interested in producing and recovering submicron (≤ 1 µm) sized particles.

This is a very difficult task and most milling procedures are incapable of producing significant quantities of submicron sized polymer and plastic particles. Cryogenic laboratory scale ball milling is one technique that has demonstrated at least some limited success producing submicron particles of polymers and plastics within our laboratory and that is why we specifically require a cryogenic ball mill for this purchase. Ball milling (as opposed to other milling methods) is more successful because it can produce the high impact forces that are necessary to break the frozen plastic materials down into submicron sized particles. Since ball milling is an extremely energetic process, the temperature of the sample being ground will rise rapidly during milling. Therefore, samples must be cooled to temperatures well below their Tg. before and during the milling process. Since Tg for some polymers can be as low as -125 ºC, cooling the samples with liquid nitrogen to a temperature of -196ºC before and during the milling process is critical.

Instrument automation and autofill capabilities of LN2 are required. Our grinding process consists of short grinding cycles (1-2 minutes) followed by cooling cycles (1-2 minutes) and these cycles must be repeated during the entire length of the grinding procedure (as much as 180 times requiring a time period of ≥10 hours). Without automation and autofill LN2 capability, this procedure would be too labor and time intensive.

Since real-world plastics often contain other materials, sometimes including metals and ceramics, we need the capability to mill these materials as well. Some of these materials mill more effectively at ambient temperatures under wet or dry conditions and require grinding jars and grinding balls of different compositions including hardened steel, stainless steel, zirconium oxide, tungsten carbide, and agate. The mill purchased must have these capabilities.

II. Salient Requirements

The Contractor shall provide one (1) cryogenic ball mill that meets the salient characteristic requirements listed below.

Salient Characteristics:

1) A closed (no potential exposure of the operator to liquid nitrogen) cryogenic cooling system is needed to keep operators safe while working at or near liquid nitrogen temperature (-196⁰C) for the entire milling procedure.

2) Milling occurs at a temperature ranging between -180⁰C and -196⁰C

3) Three different milling capabilities: cryogenic milling, wet milling at ambient temperature, and dry milling at ambient temperature.

4) The ability to connect the mill (for the purpose of liquid nitrogen delivery) to large, commercially available, LN2 Dewars (≥ 180 Liters) that will allow for extended uninterrupted grinding times of ≥ 3 hours bu use of supplied LN2 Connection Tube.

5) An automated grinding system with capability to create and store five or more standard operating programs.

6) A grinding frequency that ranges from 5 to ≥ 30 Hz.

7) A grinding jar and ball compositions of stainless steel.

8) Acceptance of a range of grinding jar sizes with volumes ranging from 5mL to ≥ 50 mL.

9) An operations manual shall be included, either electronic or hardcopy.

III. DELIVERABLES

Description Quantity Due Date

CryoMill One (1) Within 120 days after award

LN2 Connection Tube One (1) Within 120 days after award

Stainless Steel Grinding Jars (50 mL) Four (4) Within 120 days after award

Stainless Steel balls (25 mm) Four (4) Within 120 days after award

Operations manual One (1) Within 120 days after award

Delivery

National Institute of Standards and Technology

100 Bureau Drive

Building 227, Room B143

Gaithersburg, MD 20899

Delivery shall take place during normal business hours, between 7:30 am and 3:00 pm Eastern Time, Monday through Friday except Federal Holidays, and shall be coordinated with the NIST Subject Matter Expert.

IV. Warranty:

The Contractor shall provide, at a minimum, a one-year warranty for the equipment. The warranty shall cover all parts, labor, and travel. The warranty shall commence upon Government acceptance.

V. Acceptance Criteria:

The system will be inspected to assure everything within this requirements document has been met for Government acceptance.