Globally it is estimated that some 318 million tonnes of plastic are produced annually, of which 218 million tonnes is solid or rigid plastic waste. Global average plastics recycling is at 21% compared with 15% in 2016. According to the ISWA Report (International Solid Waste Association) published 7th May 2021, some 50m tonnes per year of plastic waste is incinerated with 10m tonnes finding its way into oceans and waterways.This has become widely known in the public domain leading to more pressure in finding ways to tackle this issue, but it has been unfairly levelled at the plastics industry itself.

For example, specialised screen changers with large surface areas while co-rotating twin-screw extruders offer greater flexibility especially where sectional barrels are used as vented sections can be moved around or added. This is particularly the case for PET moisture must be controlled. Natural fibre fillers mentioned earlier can contain significant levels of moisture: starch-based biopolymers can contain up to 12 percent with cellulose and wood fibre up to 8 percent.

Stephen has been with PlasticsToday and its preceding publications Modern Plastics and Injection Molding since 1992, throughout this time based in the Asia Pacific region, including stints in Japan, Australia, and his current location Singapore. His current beat focuses on automotive. Stephen is an avid folding bicycle rider, often taking his bike on overseas business trips, and is a proud dachshund owner.

Machines delivered in the 1980s and 1990s are being upgraded to outperform their original specifications, while new machine deals also are accelerating.

Hallstrom added, “Essentially we are updating machines that have been in production for over 30 years and bringing them up to the same specifications as our new machines. This has been especially popular since we started to promote this capability to our customers, as they see a significant enough savings since we are re-using the most expensive parts of these large machines, being the bases, platens, and cylinders. The customer gets back a machine that outperforms the machine’s original specifications and is as reliable as a new machine with the same warranty.”

For the operator, working with and controlling recycled material adds further challenges such as using differing temperatures, screw speed and adjustment required to pressure. Increased wear on machine parts creates additional running costs.

Milacron has aggressively expanded its rebuild and remanufacture capabilities for LPIM machines for customers. There are a large number of old LPIM machines in the field that were purchased in the late 1980s and 1990s that need rebuilds and upgrades to control systems and new motor and drive selections, moving away from DC to AC drives which provide better energy efficiency. Milacron’s full remanufacturing consists of fully rebuilding the machine to current model specifications, including full teardown and inspection, platen refurbishment, full re-painting of the machine, new controls, electrical system, and hydraulics. The major tonnage and injection cylinders and hydraulic accumulators are sent out for refurbishment and resealing. New screws, barrels, and injection melt accumulators are also included as part of this program.

The push for the increased use of recycled plastics and use of bioplastics will continue to grow but technology also continues to develop: ‘de-manufacturing’ is an increasingly important element in product design and manufacture where components can be more effectively dismantled and sorted at end-of-life stage.

For the processor, major challenges remain: although polymer prices have been dropping, they are still twice the cost per tonne compared to Sept 2020. Issues such as varying material quality, inconsistent stock availability and the plastics tax (if less than 30% recycled plastic is used) have created greater focus on recycling. This has resulted in greater wear on screws and barrels. Recycled plastics can vary significantly in melt flow due to contaminants remaining and moisture. Different plastics are often combined, making the content difficult or impossible to separate into polymer type, colour and structure. For example, PET and PVCmust be totally separated. Moisture control remains a big problem especially with PET.

There is movement toward greater use of bio-degradable polymers such as PVOH in packaging and Bio-PP in tubing for agricultural and forestry applications. Natural fibre fillers such as starch, cellulose, soya and gelatin are being increasingly used due their renewable attributes and lower environmental impact. For example, some studies have found that wood fibre filler combined with recycled PVC stabilises the recycled material for up to 5-7 cycles and improvement in material strength up to 10-15 cycles.

Despite best practice and quality control, recycled material can potentially cause problems such as the resin not fully melting or hard fragments causing wear or damage to screw flights and barrel bore. Regular monitoring is recommended so that problems can be addressed earlier if possible, before it becomes costly.

The markets driving the increased level of activity are material handling (pallets and boxes), underground enclosures for telecommunications and utilities, drainage and irrigation products, all-terrain vehicle (ATV) components, commercial/institutional, and industrial and safety products. Milacron is also seeing other new products being developed that are conversions from concrete, metal, and wood in the building and infrastructure market as well.

But particle fillers such as glass-fibre, talc and calcium carbonate remain popular as these produce cheap composites with greater strength, stiffness, heat deflection and creep-resistance. In the plastics industry, glass-fibre additive can range from 15% to 50%, making processing much more challenging: not only creating greater wear on screws, barrels and machine components in contact with the material, the material itselftends to degrade quickly due to its higher viscosity and abrasive content.

Ideal for injection molding large, lightweight, durable structural plastic parts, the Milacron LPIM Structural Foam Technology creates a cellular foamed core surrounded by integral skins, forming a total integral and rigid structure. In this process, a foaming agent (nitrogen) is mixed with the polymer melt and short-shot through a modular multiple nozzle system into a mold (or multiple molds) in a volume less than is required to fill a solid part. The injection pressure and expanding gas/polymer cellular mixture act to fill the mold. The mold cavity pressures are 10–20 times lower than conventional injection molding which permits the use of lower cost aluminum molds with no additional hot runner system since the hot runner manifold and nozzle system is integral to the machine. Many molds and large parts of different sizes can be molded at the same time. The multi-nozzle machine design allows for multiple molds to be run simultaneously allowing for higher productivity.

Ernsberger added, “Milacron worked closely with our entire team at 20/20 to identify the upgrades to the existing machines to be rebuilt that will put these machines above today’s current machine specifications and give us the widest capabilities for these size machines in the industry.” Ernsberger continued, “We also had Milacron integrate some proprietary technologies into their machines that allow us to have the most versatile LPIM Structural Foam machine fleet in the custom molding market. It’s a great partnership between the companies, as all equipment at 20/20 CMP is 100% Milacron.”

Milacron CEO Tom Goeke stated, “Stories like 20/20’s machine retrofits reinforce the fact that Milacron has an unrivaled aftermarket offering. Our aftermarket offerings aren’t only spare parts, we can literally take an older machine and transform it to like new condition. Milacron has set the standards, driven innovation and led the industry in Multi-Nozzle Low-Pressure Injection Molding Technologies for more than four decades. These machines can be used for Structural Foam, Structural Web, Gas Assist, Solid Molding, or combinations of these technologies depending on the application.” Goeke added, “The LPIM market is strong for our customers that require either new or rebuilt machines in both North America and Europe, and we have a number of solid inquiries both domestically and internationally including many from Latin America and India.”

Machine builder Milacron Holdings Corp. has seen demand increase for its Low Pressure Injection Molding (LPIM) Structural Foam machines following a successful NPE 2018 in Orlando, FL, including machine rebuilds. Milacron had a dedicated space in the NPE booth focusing on LPIM technologies and large part molding. An eye-catching display showed a replica platen of the massive Cincinnati 6,750 ton machine sold to 20/20 Custom Molded Plastics of Holiday City, OH.

Bioplastics are more temperature sensitive, hence Magog Industries have re-designed extrusion screws to minimise shear. These projects are increasing as processors are increasingly using biopolymers (with natural or organism derived cells) and bio-based polymers (partially or fully chemically synthesised). Changes in material processing behaviour (rheology) can mean re-design of the screw, e.g. change of compression ratio and mixer design required.

According to PMM (Plastics Machinery & Manufacturing), extruder OEMs such as Battenfeld-Cincinnati and Coperion have seen increasing demand for machines that process bioplastics and recycled material, hence re-design of the processing line to meet the challenges of contamination, degassing (venting), moisture and corrosion.

Bi-metallic hardened options along with specific alloy material for screws and barrels is recommended when processing with aggressive material. Magog Industries also can advise on coatings such as TDC (thin dense chrome), ceramic, tungsten carbide spray, (eg HVOF) being just some of the solutions available from Magog to assist all processors (compounding, extrusion, injection moulding and blow moulding) when processing with challenging material.

At NPE, 20/20 entered into an agreement with Milacron to refurbish and upgrade two of their existing 400-ton LPIM machines to 500-ton LPIM machines, and one of their 500-ton LPIM machines to 750-ton LPIM machines. 20/20 is also having Milacron rebuild and upgrade five of their 750-ton LPIM machines. The machines will undergo a complete remanufacture and rebuild process at Milacron’s Batavia, OH manufacturing plant and be returned like new machines.

Eric Hallstrom, Business Manager, Milacron LPIM added, “Milacron has been promoting our proprietary Structural Web technology that allows for multi-point gas assist molding that can be added to as an option to our standard LPIM machine. The process allows for a cosmetic part appearance for large projected area parts and can reduce part weights by up to 20%. The gas assist process also creates an inherently strong and durable part, molded with low internal stresses and a dual wall thickness which can replace many rotational molded or industrial blow molded parts with better aesthetics and better cycle times for higher volume parts.”

In total, Milacron is currently rebuilding eight LPIM machines as well as four HPIM machines. “Milacron’s commitment to the LPIM side of the industry, their quality, performance, and service is second to none and is the reason that we made this decision to have them rebuild and upgrade this equipment,” said Ron Ernsberger, President, 20/20 Custom Molded Plastics.

Parts molded with LPIM can replace many rotational molded or industrial blow molded parts with better aesthetics and better cycle times.