Polyolefin foams LDPE foam

Becanse there are many factors involved in the dynamic mechanical compression of polyolefin foams, the Taguchi method was employed in a Perkin Elmer DM A7 dynamic mechanical analyser to establish a method to improve the measurement process. The signal-to-noise ratio was measured to determine how the variability could be improved. Control and noise factors were evaluated and levels chosen, with details being tabulated. Appendix A describes some of the factors. Tests were conducted on two closed cell foams. NA2006 foam is 48 kg/cu m LDPE and NEE3306 foam is 32 kg/cu m EVA. Different factors were shown to influence results for E and tan delta but an optimum combination is proposed for the simultaneous measurement of both properties. The results were less variable as frequency was increased. Small differences in the dynamic response of different materials should be measurable because of the low variability in the experimental results. 18 refs. 

A review is presented of the nitrogen autoclave process for the manufacture of crosslinked polyolefin foams. Process and product developments over the last few years are summarised and future possibilities are described. Process developments include use of higher temperatures and pressures to produce foams having densities as low as 10 kg/cub.m. Product developments include foams based on HDPE/LDPE blends, propylene copolymers and metallocene-catalysed ethylene copolymers. The structure and properties of these foams are compared with those of foams produced by alternative processes. 5 refs. 

The static and dynamic mechanical properties, creep recovery behaviour, thermal expansion and thermal conductivity of low-density foams made of blends of LDPE and EVA were studied as a function of the EVA content of the blends. These properties were compared with those of a foam made from a blend of EVA and ethylene-propylene rubber. A knowledge of the way in which the EVA content affects the behaviour of these blend foam materials is fundamental to obtaining a wide range of polyolefin foams, with similar density, suitable for different applications. 9 refs. 

Cross-linked LDPE foam (see Polyolefin Foams in Chapter 2) has been produced by using either chemical cross-linking or radiation cross-Knking. These materials have been used in the automotive industry for carpeting, boot mats, sound deadening, and pipe insulation, and as flotation media for oilcarrying and dredging hose. 

R. Sanchis, O. Fenollar, D. Garcia, L. Sanchez, R. Balart, Improved adhesion of LDPE films to polyolefin foams for automotive industry using low-pressure plasma. Int. J. Adhes. Adhes. 28, 445 51 (2008)... 

There are several processes for the production of moldable polyolefin beads. In the BASF process, LDPE foam strands are extruded out of a multi-hole die and granulated to beads by a die-face cutter. Inexpensive butane is used as the blowing agent and the foam beads are then cross-linked by electron-beam. As the beads have atmospheric cell pressure, a special technique is required to develop the... 

Zotefoams has added new F grades to its ED-15 polyethylene foam range to meet the needs of the automotive and aerospace markets. The range of foams is the lightest available for crosslinked foam with a density of 15 kg/m, some 30% lighter than any other polyolefin foam, and is made in LDPE and metallocene catalysed polyolefins. 

P.O.34 is rarely used in polyolefins. In such media, it only withstands exposure to 200°C, and its opaque colorations show insufficient lightfastness. P.O.34 tends to bloom, especially in extrusion products made of low molecular weight LDPE types. The pigment is, however, recommended for a variety of other media. These range from aromatic polyurethane foams to cast resins of unsaturated polyester, in which the pigment slightly delays the hardening process. 

There have been more efforts to use blends such as Nova Chemicals Arcel (an ethylene styrene interpolymer in bead form) to create a more durable foam than EPS. EPP can be moulded into complex shapes, with the steam bonding of the beads (291). These packaging foams compete with polyolefin film products such as Jiffy foam (bubblewrap) and macrobubbles made by heat sealing 150 mm lengths of tubular LDPE film. As it is difficult or costly to recycle such foam products, in some countries there is a move towards biodegradable starch foams and moulded paperboard. 

Using a laboratory technique previously developed to evaluate the performance of chemical foaming agents in XLPE foam, metallocene polyolefins are evaluated at various addition levels to branched LDPE to determine their effect on general foam quality (cell size, density, appearance). The laboratory method is discussed, and conclusions on acceptable levels of the metallocene resins are offered. 5 refs. 

Chem. Descrip. Decabromobiphenyl oxide CAS 1163-19-5 EINECS/ELINCS 214-604-9 Uses Flame relardant for thermoplastic, elastomeric, and Ihemioset polymer systems incl. HIPS, PBT, ABS, njrfons, PP, PC, PET, polybulylene, PVC, LDPE, EPDM, unsat. polyesters, epoxies, flexible PL) foam, wire insulation (polyolefin, TPE, PU elastomer, polyamide/polyimide), adhesives, coatings, textiles... 

The commercially available AddiMet system is designed to perform on-line measurement (NIR or UVA IS) of antioxidant concentrations in polyolefins. The NIR option allows determination of bulk composition and prediction of physical properties of the polymer matrix. Vastenhoudt [146] reported determination of Irganox 1010, Irgafos 168, Ca-stearate and silica in PP with correlation coeffi-cients/standard errors of 0.92/0.008%, 0.99/0.004%, 0.99/0.004 % and 0.95/0.015%, respectively. In-line NIRS was also used to monitor CO2 dissolved in molten polymers (EPR-block-PP, LDPE, PBS) at the extrusion foaming process [152]. 

In polyolefins, it is used mainly in LDPE wire and cable insulation. Other uses reported or claimed include EVA wire and cable and foam carpet-backing EMA wire and cable EPR and EPDM wire and cable, electrical insulation, roofing, and automotive parts— white-wall tires, hoses, seals, and weather stripping XLPE wire and cable chlorosulfonated polyethylene and HDPE and polybutene. There is considerable interest in its use in PP cabinets (less smoke than polystyrene). 

Uses Blowing agent for foamed plastics, polyolefins, impact polystyrene, PP, ABS, etc. chem. foaming agent for ABS, acetal, acrylic, EVA, HOPE, LDPE, PPO, PP, PS, HIPS, flexible and rigid PVC, TPE Regulatory Canada DSL... 

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