PUSHTRUSION TM DIRECT IN-LINE (D-LFT) COMPOUNDING TECHNOLOGY VERSUS LFT PELLETS AND GMT SHEET

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Todd Elliott
6 years ago
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1 PUSHTRUSION TM DIRECT IN-LINE (D-LFT) COMPOUNDING TECHNOLOGY VERSUS LFT PELLETS AND GMT SHEET Eric Wollan PlastiComp, LLC Abstract PlastiComp s Direct In-Line (D-LFT) compounding process provides processors of fiberreinforced thermoplastics a simple and affordable alternative to pre-compounded pellets and GMT sheet, while yielding equivalent or slightly higher mechanical properties. Its clever and uncomplicated design allows PlastiComp s D-LFT unit to be easily mounted on top of injection-molding machines of various sizes to compound both long and short fiber reinforced thermoplastics. The unit can also be used as a stand alone device to compound hot charges of material that can be compression pressed into parts and replace GMT sheet. The simplicity of the system allows converters the opportunity to compound fiber-reinforced thermoplastics themselves and capture a greater portion of the value chain. The flexibility of the technology does not favor a particular thermoplastic or formulation and therefore may be tailored to solve a particular opportunity using commercially available raw materials. Direct In-Line Compounding In the D-LFT process (Figure 1), thermoplastic resin pellets are fed into the hopper of the polymer injection unit. The injector unit is a typical injection barrel, capable of melting resin and homogeneously mixing and introducing the melt into the process at high rates and pressures. Continuous glass fibers are pulled from the supply creel and into the process die by the highpressure flow of molten resin. The viscous entrainment die is designed to meter glass fiber and molten resin, keeping the glass fiber percentage within close tolerances. The glass fiber strand and molten resin mixture is pushed from the viscous entrainment die at up to several hundred feet per minute. This process starts and stops instantaneously or runs continuously, as dictated by the material output. An in-line chopper cuts the glass fiber imbedded in the molten thermoplastic resin as it exits the viscous entrainment die. The chopper s cutting chamber is heated to maintain the cut mixture in the molten state. This mixture is directed through a transition tube positioned directly above the injection press screw. Fiber chop lengths of ¼ inch through several inches are possible. The D-LFT process is capable of controlling glass fiber percentages within a narrow range. A total variation of less than ±2% by weight is typical. The significant advantage of this D-LFT process over other D-LFT technologies is the ability to control fiber length. The patented chopper design allows fibers to be chopped to a specified length. The other D-LFT technologies on the market today use twin screws to chop the fiber, which leaves the fiber length up to a random distribution. Page 1

Figure 1: D-LFT unit can be integrated with existing Compression or Injection Presses Property Comparison

of mechanical properties was performed using a formulation of 40% long glass filled polypropylene pellets with 1.

Figures 2 through 4 compare the data that was generated from pellets and D-LFT.

2 Figure 1: D-LFT unit can be integrated with existing Compression or Injection Presses Property Comparison Injection Molding (Pellets versus D-LFT) To compare properties between pellets and D-LFT technology, a comparison of mechanical properties was performed using a formulation of 40% long glass filled polypropylene pellets with 1.04% of a proprietary coupling agent. Figures 2 through 4 compare the data that was generated from pellets and D-LFT. The test bars were molded using the same mold, same injection machine, same formulation, and same initial fiber length (12mm). D-LFT LF Pellets Figure 2: Flexural Modulus D-LFT LF Pellets Figure 3: Tensile Break Page 2

3 D-LFT LF Pellets Figure 4: Flexural Strength The data suggests that the D-LFT compounds yielded higher properties. It is important to understand the possible reasons for this when the compounds and processing conditions were identical. The D-LFT compound has only one heat history, compared to two with LFT Pellets. The D-LFT compounds are never cooled and are introduced to the injection screw in an already molten state. No compression is needed to melt the material in D-LFT processing. This results in less fiber breakage than what is seen with solid pellets. Pellets are typically chopped at a length no longer than 12mm. This is to prevent bridging problems in the hopper of an injection machine. The D-LFT system delivers the chopped compound to the injection machine in a molten state right to the injection screw, so the fiber length could be up to 2 inches long and not cause any feeding issues. This becomes much more critical when molding larger parts on higher tonnage injection presses. Fiber length retention will be much greater on larger machines that have larger screw flights and larger mold gating. The result will be an even greater property increase over LFT pellets. Property Comparison GMT Sheet versus D-LFT The D-LFT process was used to create 35% glass (by weight) polypropylene charges which were pressed in a 200 ton Wabash compression press to make 7 x 7 x 1/8 thick plaques. Mechanical test bar specimens were water jet cut from the plaques and the bars were tested for mechanical properties. The properties of this material were compared to the mechanical properties of 32% (by weight) polypropylene GMT sheet as shown in Table 1 below. The properties of the material produced by the D-LFT unit meet or exceed the properties of the GMT sheet used in the comparison. It is important to note that the properties of the material produced using the D-LFT process can be influenced depending on the placement of the charge in the mold. Table 1 shows the influence on properties that material placement in the mold can have. By placing the charge of material at the edge of the 7 x 7 mold, the properties of the part were increased by approximately 30% or more when compared to properties of a part that had the material placed in the center of the mold. This increase is due mainly to increase fiber orientation. This is a level of control that is not offered when purchasing GMT sheet. Page 3

26 LGF35-PP Edge Placement 16003 938 1.9 26088 753 9.37 21.9 Not Tested Azdel Plus C321-B01 32% 11000 670 2.4 15100 663.4 10.5 Not listed 13.

4 TABLE I: MECHANICAL PROPERTIES (D-LFT versus GMT) Material Tensile Strength (psi) Tensile Modulus (ksi) Elong. (%) Flex Strength (psi) Flex Modulus (ksi) Notched Izod (ft*lbs/in) Unnotched Izod (ft*lbs/in) Dyantup Total Energy (ft-lb) LGF35-PP Center Placement LGF35-PP Edge Placement Not Tested Azdel Plus C321-B01 32% Not listed 13.3 The Cost Advantage In order to stay competitive in today s global market, cost reduction is a key. Raw materials are typically the largest cost component of plastic part manufacturing. This is where D-LFT has a large advantage over LFT pellets. A material processor can typically save up to 30% in raw material costs when using D-LFT technology instead of LFT pellets. The savings can be even greater when employing this technology with higher cost materials such as Nylon and TPU. Where this D-LFT separates itself from other D-LFT technologies is with its size (its compact construction allows for the unit to be mounted on top of an existing injection machine, minimizing the need for additional floor space) and its price. This D-LFT system can also be bypassed or removed when not in use so that a molder can process pre-compounded pellets if necessary. This increased flexibility reduces the risk of having an underutilized, dedicated asset on the production floor. The D-LFT unit can be retrofitted to an existing injection machine, or an entirely new system can be purchased. With the large material costs savings that these systems return, the ROI on this equipment is quite rapid. Figures 5 and 6 show several different payback scenarios based on a retrofit unit or a complete D-LFT unit. Fig. 5. Assume 5lb part or less at $2.50/lb cost of LFT PA6 material. The EAV in this example is 250K lbs and a $1.75 raw material cost with D-LFT. This results in a ROI of approximately 1.5 yrs. Figure 5: ROI of Retrofit D-LFT Unit Page 4

Figure 6: ROI of New D-LFT Unit Fig.6. Assume 3 lb part or less at $2.50/lb cost of LFT PA6 material. EAV of 250K lbs. $1.75/lb raw material cost with D-LFT. This results in a ROI of approximately 2.

It is important to understand that under the complete unit scenario, the D-LFT unit is paying back the entire injection machine and compounding unit.

5 Figure 6: ROI of New D-LFT Unit Fig.6. Assume 3 lb part or less at $2.50/lb cost of LFT PA6 material. EAV of 250K lbs. $1.75/lb raw material cost with D-LFT. This results in a ROI of approximately 2.75 yrs. At first glance, it would appear that the retrofit option is the best Return-On-Investment. It is important to understand that under the complete unit scenario, the D-LFT unit is paying back the entire injection machine and compounding unit. Both units can still be used as traditional molding machines when desired, which makes both cost scenarios very conservative. Many of the competitive D-LFT technologies on the market are three to four times the cost of this D-LFT system. In order to get a suitable ROI on a competitive unit, the molder must have a very large volume OEM that they are molding for. This limits the amount of users of D-LFT technology in the marketplace. These units are only capable of D-LFT processing, thus increasing the risk if an account is lost. This D-LFT system reduces the expense and risk to the molder, by offering a lower cost, flexible alternative. Conclusion This D-LFT technology has the opportunity to disrupt the compounding industry by offering an affordable alternative to current D-LFT suppliers. The ability to be able to remove or bypass the D-LFT unit and use the injection machine to mold pellets greatly reduces the risk to the molder. The cost savings that are passed on to the molder through raw materials can be greater than 30% of LFT pellet prices. D-LFT technology is able to supply formulations that yield mechanical properties equal to or greater than those of LFT pellets and GMT sheet. Page 5

Pushtrusion TM. New Direct Compounding Technology. New. Integrating new technology with state-of. of-the-art production systems

Pushtrusion TM. New Direct Compounding Technology. New. Integrating new technology with state-of. of-the-art production systems Pushtrusion TM New Direct Compounding Technology New Integrating new technology with state-of of-the-art production systems Eric V. Lee, product manager Presentation Content Review market dynamics contributing