Linde PLASTINUM®: The plastic pioneers

As the plastics industry tries not to bend to market pressures, Linde PLASTINUM® CO₂ solutions are pushing productivity to the max.

According to analyst IHS Chemical, by 2020, the average car will incorporate nearly 350 kg of plastics; 75% more than in 2014.  It’s all part of ‘lightweighting’ – a fast emerging trend in the automotive industry – where original equipment manufacturers (OEMs) are turning to new lightweight materials and high-tech composites to reduce the overall weight of vehicles.

The main reason for this is that regulatory authorities are pushing for greater fuel efficiency and lower emissions. Making vehicles lighter goes some way to meeting this challenge. As a result, plastics are being extensively employed throughout the vehicle for everything from door handles to internal fascia. But fuel efficiency isn’t the only pressure bearing down on the automotive industry.  Increased demand and competitive pressures also call for faster cycle times and reduced scrap rates, all while meeting the rising customer expectations around material strength and quality.  

All this goes to say that the plastics market is facing challenges. And since industrial gases play an indispensable role in plastics manufacturing, Linde has developed a portfolio of gas-based solutions – in particular based on CO2 – that meet these challenges. It’s called PLASTINUM® – and here are some highlights.

Car silver open door, picture taken from the side.
The use of plastics in cars is on the up; to make sure that the weight goes down.
PLASTINUM Foam key visual - car dashboard montage
Applications of foam injection moulding in the automotive industry: less weight, less material.

CO2: Let’s get physical

Foaming is an effective means of reducing the weight of any injection moulded plastic part and it’s here that Linde’s latest PLASTINUM offering is set to shine. Foamed plastics, also known as “expanded plastics” or “cellular polymers”, are produced when a blowing agent forms gas bubbles within the liquid plastic, which then solidifies into a foamed or porous structure. Since the gas is lighter than the solid, foams save on both weight and materials. “Foaming is being used more and more in the automotive industry, for exactly these reasons,” explains Paolo Kirchpfening, Global Marketing Manager, Commercialisation Management Chemicals & Environment, Linde Gases division, “but also in other industries such as medical and electrical/electronic as it allows manufacturers to achieve specific part properties.”

Linde will launch its PLASTINUM® Foam Injection Moulding technology at this year’s FAKUMA International Trade Fair for Plastics Processing.  It works by impregnating plastic pellets with pressurized carbon dioxide (CO2) in Linde’s revolutionary new equipment prior to the injection moulding process. This system allows for physical foaming in conventional injection moulding machines without retrofitting or adding more expensive equipment, thus reducing production costs and offering a more flexible system. 

This all-new physical foaming process was jointly developed with the Kunststoff-Institut Lüdenscheid. Germany-based ProTec Polymer Processing GmbH is also a partner and has developed a system for industrial application.

CO2: Cooler than nitrogen any day

When weight reduction isn’t the primary goal but the focus is on quality and cycle time reduction, Gas Injection Moulding (GIM) is increasingly used today. “For thick walled plastic parts like fridge handles, car door panels and bike racks, surface quality is important,” explains Andreas Praller, Senior Application Expert at the Linde Gases Division, “but without internal pressure in the mould, the plastic just shrinks, creating an unacceptable finish.” 

In regular GIM, high-pressure nitrogen (50 to 340 bar) is used to ensure dimensional stability, but Linde’s PLASTINUM® Gas injection moulding solution takes efficiency to the next level by replacing gaseous nitrogen with liquid CO2.  “CO2 can reduce cycle times by up to 30%,” explains Praller, “it has a much greater cooling potential than nitrogen due to its much higher density at typical GIM pressures.”

In fact, it performs at a comparable level to the more niche water injection moulding (WIM) in terms of heat removal capacity and cycle times. The difference is, it doesn’t leave any moisture on the products or tools, thus eliminating an additional drying step in the fluid injection cycle. “It’s the perfect solution for the best of both worlds” explains Praller.

CO2 is particularly beneficial where an automotive manufacturer wants to produce as many parts as possible with the same machine: “Switching from N2 to CO2 is very straightforward and can immediately increase your capacity due to reduced cycle times,” says Kirchpfening. 

PLASTINUM Mould Spot Cooling – Mould with conventional water cooling and CO₂ cooling of the core

CO2: Going places water can’t

Besides productivity pressures, injection-moulded plastic part manufacturers face a more practical challenge: cooling the mould tool itself. “Uniform temperature distribution is more important than you might think,” says Praller, “because the area taking longest to cool will determine the total cycle time and thus, productivity.” 

Such cooling is usually done using water which flows into small channels ideally evenly distributed throughout the tool. These channels need to be at least five millimetres thick – so when the mould includes long, narrow cores or other tiny areas, water simply can’t get there. The result: so-called “hotspots”.  “It’s a particular problem for our foaming customers,” adds Praller, “because the gas pockets make it harder for the heat to escape.”

To serve these customers, Linde offers a complimentary cooling solution: PLASTINUM®Mould Spot cooling: using CO2. “We can ensure cooling of cores with a diameter of even two millimetres by introducing liquid CO2 via thin and flexible capillary tubes,” says Kirchpfening. “This alone can reduce cycle times by up to 50%.” But, as always, shorter cycle times are only half the story: the other half is quality. “Spot cooling ensures a higher quality of part by reducing warpage and eliminating sink marks,” Praller adds. It seems PLASTINUM delivers on all fronts.