ADDITIVES | COMPATIBLISERS
parts, Monte says. “For example, although HDPE and PP are polyolefins and classified as addition polymers, more than 5% PP blended into HDPE will cause delamination issues when injection mould- ing the blend. PET, PBT, PC, and PA are condensa- tion polymers and are incompatible with addition polymers.”
While maleated polymers are often used to
compatibilise two dissimilar polymers, problems arise when there are more than two polymers, which frequently occurs in non-segregated PCR streams. “For example, if the stream contains PET, PBT, PC, PA and other condensation polymers, maleic anhydride will depolymerise them, reducing mechanical properties,” Monte says.
Above: Two samples of recycled waste streams containing PET contami- nated with other plastics. The one on the left has no compatibiliser. The one on the right, produced under the same process conditions, contains Struktol TR 219
tion product that aids in the incorporation of fillers (mineral or glass) by improving mixing and flow properties as well as mould release. These products result in better processing, improved surface quality, and in some cases, better physical properties. One recently introduced example is Struktol TR
229, designed for use in both polycarbonate (PC) and PC/acrylonitrile-butadiene-styrene (ABS) blends as well as polyamide 6 and 66 compounds. It can be used in FDA-approved applications and is also ideal for use in recycled applications. Struktol also offers Struktol TR 219 for use in PA6 and 66 compounds. It has been found to be effective in polyester (PET and PBT)-based compounds too, Fulmer says. Struktol TR 052, which Fulmer says is the company’s most robust compatibiliser, is said to be highly beneficial, even at low addition rates, for incorporation of regrind/recycled product in a wide range of polymers. “Processors can realise im- proved physical properties and overall improved processability of compounds requiring some level of recycled content,” he says.
Catalyst approach Kenrich Petrochemicals takes a completely different approach to compatibilisation of post- consumer recyclate, although again the aim is to be able to handle unseparated streams. Company President Salvatore Monte says the end product is suitable for consumer and automotive products. Common packaging polymers, such as HDPE,
PP, and PET, are intrinsically incompatible with each other and even small amounts of contamination can cause processing and quality issues in finished
76 COMPOUNDING WORLD | May 2018
Simpler segregation A small amount of Kenrich’s Ken-React CAPS KPR 12/L, however, acts as a Z-N/metallocene catalyst in the melt to compatibilise the non-segregated resins, as well as the fillers in the resins. “The product can catalyse both addition and condensa- tion polymers and at the same time couple and disperse fillers such as calcium carbonate and carbon black. Doing so significantly reduces segregation requirements to a practical level as filler levels can be in the 20 to 40% loading range without detracting from stress/strain properties,” Monte claims. The new CAPS KPR 12/L product is based partly on a neoalkoxy titanate coupling agent, which is a known repolymerisation catalyst for unfilled polymers. It allows the extruder to act as a poly- merisation reactor. However, solving the technical challenge still
leaves two major PCR market obstacles, says Monte. “The first is economics: the additives add costs in a market suppressed by low shale-oil resin prices and China’s recent restrictions on baled recyclables. The other is processing savvy: the PCR stream must be granulated and melt processed so that the polymer catalysis and filler coupling chemistry of the additive can go to work in the extruder melt.”
CLICK ON THE LINKS FOR MORE INFORMATION: �
www.lbf.fraunhofer.de/en �
www.fineblend.com.cn �
www.polyscope.eu �
www.yparex.com �
www.clariant.com �
www.polygroupinc.com �
www.nexamchemical.com �
www.struktol.com �
www.4kenrich.com
www.compoundingworld.com
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