Polyethylene masterbatches with

A new generation of process aid masterbatch is claimed by Cabot. Plasadd comes in two grades, for linear low-density polyethylene film with, respectively. 

These are highly effective external lubricants for PVC, with positive effect on gelation and surface quality of finished products. Polar polyethylene waxes have a pronounced anti-sticking effect and high molecular types are suitable for transparent items. Other waxes improve pigment dispersion and permit production of highly concentrated masterbatches with better colour yield. 

Additive masterbatches with fragrance have been developed by Clariant Masterbatches. Five flavours are available, initially for use with polyethylene, with let-down ratios of 2-10%. Formulations for other plastics are under development. 

Experiments were then carried out to compare specific output rate and masterbatch distribution. The material was natural low-density polyethylene blended with 5% of a 40% carbon black masterbatch. 

Ampacet claims that it has been able to lower the range of trigger temperatures over which azodicarbonamide masterbatches work, from the usual 190-205 °C down to 170-200 °C. Bayer sells a modified azodicarboxylic acid diamide-based blowing agent called Porofor ADC/Z-C2 for foaming crosslinked polyethylene. It is claimed to allow the manufacture of lower density foams at conventional oven temperatures, with shorter production cycles than standard ADC diamides. 

The functionalization of EPDM with MA is carried out in a Berstorff 25 mm corotating twin screw extruder. EPDM (Keltan 740 DSM), Perkadox 14 (bis(tert. butyl peroxy isopropyl) benzene AKZO half life times 5 min at 175 °C 10 sec at 210 °C [4]) and Nourymix(50/50 wt% masterbatch of MA on polyethylene AKZO) were mixed and starved fed to the first section of the extruder. A nitrogen atmosphere was maintained over the reaction mixture throughout the extruder. In the last sections free maleic anhydride and other volatile components were removed by applying vacuum on the last vent. Standard extrusion conditions were throughput rate 1 kg/h residence time 5 minutes rotor speed 150 rpm Mass temperatures in the die 220-260 OC. The MA-content in the rubber was determined with potentiometric titration and infrared analysis. 

About 56% of the total polymer consumption in masterbatch is polyolefins, estimates Ampacet, with polyethylenes making up 41.14 million tonnes and polypropylenes 24 million tonnes. 

Concentrates or masterbatches are consistent, simple, and safe. They usually come in a granular form, in which the concentrated pigment is dispersed in a polymer carrier (such as polyethylene) that is compatible with the matrix resin. The let-down ratio is usually 0.5-2%, depending on colour, host material, and part thickness. 

Because polyethylene and polypropylene are in beads or granular forms, these additives are normally added in master-batches. These masterbatches are added in proportion to add in lower concentration. Usually antiblocking agents are used in combination with calcium silicate or kaolin. Antiblocking agents do not dissipate static charge. 

In the 1970s, a number of polymer suppliers introduced a marketing policy which discontinued the supply of polyolefin compounds in favour of supplying natural materials. The discontinued compounds included black polyethylene for water pipe extrusion in which the pipe producers substituted the black compound fed to their extruders with pellet blends of natural polyethylene and carbon black masterbatch. 

During the 1970s, most UK extrusion companies producing black polyethylene pipes and cables used pre-compounded material. If fed with a blend of natural polymer and masterbatch, which would have reduced material costs, they would have failed to meet the carbon black mixing requirements of the relevant British Standards. 

Figure 7.6 Maddock type barrier shearing element for 38 mm extruder. Reproduced with Permission from G.M. Gale, Masterbatch Flow Patterns in Polyethylene Extrusion, Rapra Members Report No.16, Rapra Technology, Shawbury, Shrewsbury, UK, 1978, Figure 7. 1978, Rapra Technology)...

The extruder was run with the pellet feed maintained by hand at a level just covering the screw. Individual black masterbatch pellets were added at timed regular intervals. After a suitable overall extrusion time the extruder was stopped, rapidly cooled and the screw ejected with a hydraulic ram. A pipe grade low-density polyethylene (LDPE) was used with masterbatch pellets containing 40% carbon black. 

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