The AEWC Center’s wood plastic composites pilot plant is a world-leading facility offering industrial clients a range of manufacturing and testing services. AEWC’s range of manufacturing equipment and capacities serve a global list of manufacturers interested in initiating, improving and/or diversifying their wood plastic composite extrusion capacities. AEWC’s ISO 17025 accredited testing capacities enable manufacturers to evaluate wood plastic composite products according to international standards recognized by building code and other product certification agencies.

 

Davis Standard Woodtruder

The centerpiece of the AEWC Center’s Wood Plastic Composites Pilot Plant is a Davis Standard WT-94 Woodtruder™ . The Woodtruder includes twin and single-screw extruders, a blending unit, a computerized blender-control system, a die tooling system, a spray cooling tank with driven rollers, a traveling cut-off saw, and a run-off table.

The Woodtruder™ can process fibers from sawdust, wood (both hard- and softwoods), sisal, rice hulls, kenaf, flax, peanut shells, recycled polymers, and many other materials.  These are combined with such plastics as polypropylene, high-density poly ethylene (HDPE), and poly vinyl chloride (PVC), which are variously found in many consumer goods such as milk jugs, house siding and plumbing materials. Work is also underway examining the processing of wood fiber with engineering thermoplastics (nylon).

As processing begins, fiber is placed into the unit’s Colortronic Graviblend Plus 1 station blending unit and weighed within. The wood is fed into the throat of the twin screw extruder and the fiber is dried from 5 to 8 percent moisture down to below 1% through a series of heating zones with atmospheric venting.

 Meanwhile, separate from the fiber, the plastics are melted. This separation insures that fibers will not be burned during processing when the melted plastics encapsulate the fibers completely. These materials are then mixed and any remaining moisture or volatiles are removed by vacuum venting.                                                                                          

 

 

 

 

      Next, the materials are shaped in a die           cooled in the conveyor spray cooling tank,

                                                     

cut to the desired length with the Model MST-6 traveling cut-off saw and collected on the Model DT20-6 run-off table

 

Compounding and Pelletization

To meet specific processing parameters of various commercial manufacturers of wood plastic composite materials, the Center has capacities for specialized compounding – the action of mixing together several types of materials with a polymer matrix. Compounded strands which can be manufactured in the Davis-Standard Woodtruder or in the smaller Cincinnati Milacron CM55 conical twin-screw extruder, are cooled and directly fed into a pelletizer, a machine that has a rotating set of blades that chops the strands into pellets of a user-controll  able length. These pellets are dried and bagged and may be used by polymer processors anywhere in the world.

 

 Agglomeration

The Center’s pilot plant has capacities for agglomeration, a process of particle size enlargement which gathers small, fine particles such as dusts or powders into larger masses, clusters, pellets or briquettes. These agglomerated materials can then be used as end products or in a secondary processing step. AEWC’s Pallmann Pulverizer makes the Center one of the premier developers of this process in North America.

 

 Injection Molding                                                                                                                                               

AEWC’s Engel CC90 injection molding system generates test coupons for testing materials in flexural bending, tension, and impact and allows in-house determination of the operating and mechanical properties of various WPC formulations developed from compounding, agglomeration, and pelletization. This system provides a tool to gauge and establish base-line performance data for various wood plastic composites.

 

 

Dryer

The steam tube dryer is available to dry wood flour and other fiber materials to moisture contents below 1% in order to faciliate extrusion compounding for the CM 55 extruder and the Woodtruder.

 

 

 

Material Property Testing Capabilities at UMaine-AEWC for Wood Plastic Composites

 The AEWC Center performs a variety of ASTM Standard tests, as well as custom tests. The staff consists of full-time, dedicated personnel supported by supervised graduate/undergraduate students. This flexible staffing arrangement enables the Center to provide quick turnarounds on routine testing. Frequently, one-week service is available for common tests. Examples of ASTM Standard tests performed at the AEWC Center are listed below.