additives | Polymer foam
Table 1: Nucleation efficacy of kinetic against mineral nucleation in foamed PP profiles Sample
Cell size range Nominal cell (microns)
CFA alone
CFA + CaCO3 CFA + talc
50-130 30-100 30-135
CFA + kinetic nucleator 30-100
size (microns) 100 80
100 85
Source: Reedy Chemical Foam and Specialty Additives
Table 2: Comparison of foaming characteristics of ADC against SAFOAM HT in PP profiles Sample
Cell size range Nominal cell (microns)
ADC at 0.5% 45-320
SAFOAM HT at 0.5% 35-130 ADC at 0.75%
100-450 SAFOAM HT at 0.75% 35-180
size (microns) 180 75
290 90
Source: Reedy Chemical Foam and Specialty Additives
namide (ADC) to meet European Union regulatory requirements. “ADC is now listed as a REACH Substance of Very High Concern (SVCH)” says Keefe. “The industry is searching for ADC alternatives that are not SVCH classified that still perform as ADC does with respect to foaming characteristics - activation temperature and gas yield.”
Reedy has been developing a number of new
products designed to address these requirements. “For HMS-PP, we have introduced SAFTEC RB-25, which is an easy-to-use pellet concentrate to improve the melt strength of reuse HMS-PP,” Keefe says. “It allows the use of a greater percentage of HMS-PP trim scrap by creating a fibrous network in the melt, leading to improved melt strength. In addition, we have developed SAFOAM Kinetic Nucleator products that distribute the foaming agent gas more efficiently resulting in more cells from the same quantity of gas and a lower density. SAFOAM Kinetic Nucleators generate cells due to particle morphology and the spinning motion of the
Right: TecoCell technology, marketed for injection moulding applications by Trexel, is claimed to deliver a highly consistent foam in a range of polymers including HDPE (left) and PP
40 COMPOUNDING WORLD | January 2016
www.compoundingworld.com
Density (g/cm3
)
0.685 0.685 0.644 0.529
Density (g/cc)
0.837 0.754 0.694 0.675
Density
reduction 8.1%
17.2% 23.8% 25.9%
particle - the spinning motion releases numerous cells constantly. Traditional mineral nucleators typically generate a fixed number of cells per mineral particle.” The company has introduced SAFOAM LE, a chemi-
cal foaming agent product line with a kinetic nucleator designed for polyolefins and polyolefin compounds. “SAFOAM LE products allow the moulder or extruder to achieve greater weight savings, through density reduction, by more efficient gas nucleation,” he explains.
Reedy has also developed SAFOAM HT, a high Density
reduction 24.5% 24.2% 28.8% 41.5%
temperature endothermic chemical foaming agent product line available in pellet or powder form offering an activation temperature of 207˚C, which Keefe claims is in line with the activation temperature of ADC. The company recently completed a study comparing
the efficacy of kinetic nucleation against traditional mineral nucleators in extruded foamed PP profiles. Equal weight ratios of endothermic chemical foaming agent and nucleating agent were used, with the results showing that the SAFOAM Kinetic Nucleator bettered density reduction by 2.1% over talc, an 8.8% relative improvement (Table 1). A second Reedy study compared the foaming
characteristics of ADC to SAFOAM HT in PP profiles across two doses of the chemical foaming agents under identical extrusion conditions. The company says the results (Table 2 and shown in the photographs in Figure 1) show that SAFOAM HT is a viable alternative to ADC but cannot be considered a drop-in replacement.
Engineering solutions Another key area of development is carrier technolo- gies, which is a response to the growing demand for foamed engineering plastics, according to Dr Ronak Bahrami, Group Leader Polymer Foams at the Univer- sity of Bayreuth in Germany. “Generally, engineering plastics have better mechanical properties and thermal stabilities and are suitable for high performance applications in the automotive industry, sports equip- ment and the aviation sector. In addition, there is the need for lightweight materials in everyday applications,
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