Polymer foam | additives
Polymer foams can be created using chemical or physical blowing
technologies. Mark Holmes looks at
some of the latest technological advances and the market drivers behind them
Weight concerns help lift foams
Polymer foaming is certainly not new but it is a technol- ogy that is being increasingly widely used today and for a number of different reasons, ranging from cost reduc- tion to performance and process improvement. Speaking at AMI’s Polymer Foam conference late
last year, Reedy Chemical Foam and Specialty Additives President and CEO Peter Schroeck highlight- ed the opportunity to cut cost through reduced material consumption, as well as the need to minimise product weight, as key criteria. However, he also cited elimina- tion of sink marks during processing, improved thermal and sound insulation, more stable and repeatable processing, and the opportunity to lower processing temperatures, leading to faster cycle times and reduced energy consumption, as important factors. From a chemical foaming perspective, Reedy Senior
Product Manager Larry Keefe says the company has identifi ed three main trends driving new developments in blowing agents and foaming technologies. Prime among these is the pressure to replace foamed polystyrene (PS) single-use food service items with foamed polypropylene. “The driver of this conversion is local and national governments’ legislative efforts to ban foamed polystyrene food service items,” he says. “Low density foamed polypropylene requires the use of high melt strength polypropylene polymer (HMS-PP). In the typical manufacture of single use food service items, the trim scrap from thermoforming fi nished articles from foamed sheet is fed back to the sheet extruder for reuse. The industry has found the percent- age of reuse for HMS-PP trim scrap is about half of that for PS, due to the loss of melt strength of the HMS-PP
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after extrusion and thermoforming. In addition, the fi nal density of foamed HMS-PP is higher than foamed PS,” says Keefe. A second area of development results from demand
from automotive manufacturers to accelerate mass reduction in automobiles and light trucks. “New models are being created where injection moulded plastic components are designed with ‘foam’ to reduce the weight of the entire automobile,” explains Keefe. “Mass reduction of injection moulded automobile applications requires the use of a resin or compound that can readily accept incorporation of a physical or chemical foaming agent to create weight savings without sacrifi cing physical properties or appearance. After resin/ compound selection, the foaming agent plays a crucial role in creating the cell structure resulting in weight savings without loss of properties.” Thirdly, the industry needs alternates to azodicarbo-
Figure 1: Image left shows a sample of foamed PP containing 0.75%ADC, the right image shows the same polymer foamed with 0.75% of SAFOAM HT from Reedy
January 2016 | COMPOUNDING WORLD 39
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