Foam profile

Journal of Applied Polymer Science 68, No.8, 23rd May 1998, p.1237-44 EFFECT OF ADDITION OF EVA ON THE TECHNICAL PROPERTIES OF EXTRUDED FOAM PROFILES OF LOW-DENSITY POLYETHYLENE/EVA BLENDS Rodriguez-Perez M A Duijsens A de Saja J A Valladolid,Universidad Sekisui Alveo BV... 

Foam densities were determined by use of gamma ray absorption to determine the amount of crude carried over in the foam. Under severe conditions, foam densities between 15.6 and 33.7 Ibm/cu ft (250 and 540 kg/m3 were measured, compared with a crude density of 50 6 Ibm cu 4 ft (810 kg. m11 Thus the crude content of the loam was between 28 and 66% by volume. Furthermore, up to 900 tonnes/hr (900 Mg/h], or 50%, of the crude fed to a separator could be carried over in foam Profiles of foam density and carry-over were similar for both the HP and LP separators. 

The aim of coextrusion is outlined and the tooling available for different types of profiles, including window profiles, sidings, fences and foam profiles, is described. Machinery for coextrusion is also described and details are provided on a specially designed coextrader (BEX 2-54CC/1) equipped with negative conical screws. 6 refs. 

SLAB FOAM. PROFILED SLAB FOAM MOLDED FOAM... 

Ryurtm. [Tosoh] Ediylene-vinyl chloride, PVC or blends, or EVAAPVC polymers for rigid a foamed profiles, flexible tu film, sheet, shoes and boots, crash pads, inj. molding, wire and cable insidation, pipe, dip and sptvf coatings, castings. 

Foamed profile. [Data from Foamed profiles. Baerlocher. ... 

Amphoteric surfactants have especially good foaming profiles in soft water. Betaines, in particular the amidopropyl types, are tolerant of hard water, followed closely by the tolerance of sulfobetaines and... 

A comparison of the foaming profile found in a standard flexible slabstock foam production with the one seen during liquid carbon dioxide foaming clearly shows a large difference in the rise profiles, especially at the lay down (Figure 2.3). 

Figure 2.3 Foaming profiles of standard flexible foam production and liquid carbon dioxide foaming.

Blends of a PO (PE, PP, PB, P4MP, their blends, and copolymers, e.g., with 1-aIkenes, vinyl esters, vinyl chloride, methacrylic esters, and methacrylic acid) with 0.2-50 wt% of a graft copolymer showed high tensile modulus and high sag resistance without increased melt viscosity. The blends could be shaped into foamed profiles at T = 200-230 °C. 

Choosing the right surfactant or surfactant combination that can deliver a desired foam profile is often done on a trial-and-error basis. As mentioned previously, often the surfactant structure that improves foam volume is not the same as that which contributes to foam stability. Some general guidelines about surfactant structure and optimum foam performance are listed as follows ... 

In-bowl cleaners are used with mechanical cleaning by the consumer. These products are usually liquids, usually thickened in the range of 200-700 cP. The idea is that the product is dispensed up under the rim of the toilet and then runs down the bowl wall until it encounters the water. The package for the product often has a specially shaped bottle that enables placonent of the product under the rim (Figure 5.2). The product should be thick enough to cling to the vertical wall and yet not be so thick that the product does not spread well. It should also have a foam profile that collapses quickly so that the product rinses away well. As in the case of many bathroom cleaners, these also come in two types, the acid and the hypochlorite. 

Ferch and Leonhardt [2] have made a comparison of the antifoam effects of blends of sodium tallow (C,6-C,g) and behenic (C20-C22) soaps on a wash cycle at a water hardness of 2.85 mM. A detergent powder formulated with a mixture of sodium alkylbenzene sulfonate and non-ionic surfactants was used together with a mixture of zeolite and sodium tripolyphosphate as builder. The resulting foam profiles are shown in Figure 8.4. An initial foam peak at the low temperature start of the wash... 

As in the example of the detergent formulation used to obtain the foam profiles shown in Figure 8.4, early attempts to develop praetieal washing powder formulations suitable for foam-intolerant, front-loading drum-type laundry washing machines utilized the antifoam effect of calcium soaps in mixed anionic and ethoxylated alcohol surfactant systems. The approach appears to have been entirely empirical. The foam behavior of ternary mixtures of anionie surfaetants, sueh as sodium alkylbenzene sulfonates, various ethoxylated alcohols, and soaps, was optimized for low foamabil-ity in relevant machines by systematie trial. Obviously, polyvalent metal ion (especially calcium) activity as determined by temperature, water hardness, and builder type and concentration represented an additional variable. Wash temperature and pH... 

As we have seen, the presence of ethoxylated non-ionic surface-active compounds can enhance the susceptibility of the foam of solutions of anionic surfactants to antifoam. This appears to be a general phenomenon that is also manifest with PDMS-hydrophobed silica antifoams in wash cycles with drum-type, front-loading, textile washing machines. This well-known effect is exemplified in Figure 8.13 where the addition of ethoxylated alcohols is seen to diminish the foam profile of solntions of sodinm alkylbenzene snlfonate (LAS) in the presence of PDMS-hydrophobed silica antifoam. Sawicki [7] has shown that the effect of these ethoxylated componnds does not concern either the precipitation of cloud phase drops (see Section 4.6.3.2) or marked changes in dynamic or equilibrium air-water solution snrface tensions. One possible explanation could concern a putative inhibiting effect of ethoxylated compounds upon the rate of PDMS-hydrophobed silica antifoam deactivation. However, this would afford no explanation for the effect of those componnds on the antifoam action of hydrophobic precipitates where no oil is present (see Section 8.2.2). 

FIGURE 8.14 Schematic illustration of potential effect of delayed release on washing machine foam profile of deactivating PDMS-hydrophobed silica antifoam. 

A major property of EO/PO nonionics is their low-foaming profile. Moreover, if the copolymer incorporates sufficient PO chains to be close enough to the solubility limit at the considered washing temperature, the surfactant can effectively act as a foam depressor when involved in systems with other surfactants such as LAS. 

Surfactants of this class are good emulsifiers, especially for polar molecules such as natural oils and fats. Alkylpolygiucosides provide good wetting and foam profile their foaming properties are superior to classical ethoxylated alcohols. They are, however, somewhat temperature sensitive. 

A desirable foam profile depends on the intended use of the product laundry or dish washing, skin and hair cleansing, and so forth. So it is crucial to learn about methodologies for measuring foam characteristics relevant to the product to be developed, as well as to understand how to control foam when overfoaming has to be compensated for or when foam has to be stabilized. 

IV. DESIRABLE FOAM PROFILE ACCORDING TO PRODUCT APPLICATION... 

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