For this proposal, we wanted to take an agricultural waste product and combine in a reactive extrusion process using a twin-screw extruder (TSE), the details of which are still proprietary. This is something that is our bread-and-butter here at Aspen Research. We were pioneers in the wood-polymer composite (WPC) area and most of the patents assigned to Andersen Windows involving WPC's had Aspen Research personnel as inventors. In other words, we do know what we are doing in this subject matter.
Here's some of the feedback:
"Rheological control of bio-based materials is challenging for molders. The polymers contain moisture, so special equipment will be needed for polyethylene and/or polypropylene molding shops"Polyethylene? Polypropylene? Where did those materials come from? We didn't mention them other than as materials we might displace. PE and PP cannot be prepared in a reactive extrusion process. If we had suggested reactive extrusion of PE or PP, that alone would be worthy of multiple SBIR grants as that would revolutionize the entire industry, completely overlooking the incorporation of ag waste into it. Also, ag waste materials can contain moisture (not "polymers"), but since this process is performed entirely in a twin screw extruder, the moisture can be removed through the vents, something we do all the time. But let's just go along with the reviewer and agree that we cannot remove the moisture. Since when is moisture such a heartache requiring "special equipment"? Show me an injection molder without a resin dryer and I'll show you an injection molder shop that is owned by their bank and being auctioned off. Resin dryers are not special equipment.
"However, the use of reactive extrusion in this proposal will not be enough to homogenize the feed material due to the fact that such a process is only good for processing times of 100-1000 seconds. With [ag-waste particles] at a size scale of 1 mm and highest mass diffusivity of 0.00000001 sq cm/s for [these] materials, we are looking at processing times in the order of 1000000 seconds...If experiments were done, the above difficulties will be made evident, and that the 4 hr processing time facilitated by the use of small molecule reactive components will still be needed."This reviewer is too clever by half. I haven't bothered to see if the diffusivity numbers are correct (I'll assume they are), BUT THEY ARE ONLY VALID FOR NON-CONVECTIVE FLOW CONDITIONS, something completely remote from the inside of a twin screw extruder. Nobody ever models the flow inside a TSE because there is just too much going one - melting, mixing, conveying, venting (which requires increasing and then decreasing the pressure), all in very small, thin films moving in three different directions. Furthermore, the ag-waste particles don't need to diffuse anywhere - the reactive monomers diffuse to them (actually, the monomers are convected to the ag waste), and quite easily at that. And lastly, if the reviewers arguments are correct, then WPCs would not be possible, since WPCs are made by combining wood particles with high molecular weight polymer which really is impossible in quiescient diffusivity. Not only do experiments show that 4 hours processing times are not needed (even 4 minutes is too long), but the commercial success of Fibrex, Trex, Timber Tech and dozen of other products show the economic viability of this process.
Feedback like this provides no insight as to how to improve the proposal. I really question whether these reviewers have much or any industrial experience. Certainly whatever experience they do have is not enough, as the comments shown here are not helpful at all, and in fact are just plain wrong. Why can't these reviewers just say something like "neat idea, but we liked some other ideas better"?