Poly ethylene Foams

Chemically embossed metallocene polyethylene foams are used, for example in a floor covering. A blowing agent azodicarbonamide has been proposed. The blowing agent activator is selected from citric acid, oxalic acid, p-toluene sulfonic acid, phosphoric acid, potassium carbonate, borax, triethanol amine, zinc chloride, zinc acetate, zinc oxide, zinc stearate, barium stearate, calcium stearate, urea and poly(ethylene glycol) (6). 

Pressman, Modified flame retardant polyphenylene ether resins having improved foamability and molded articles made therefrom, US Patent 4 791145, assigned to General Electric Company (Selkirk, NY), December 13,1988. 

Expandable composition and process for extruded thermoplastic foams, US Patent 5 462 974, assigned to Sealed Air Corporation (Saddle Brook, NJ), October 31,1995. 

Joyce and D.J. Kelley, Polyphenylene ether-alkenyl aromatic polymer blends having organobromine additives, US Patent 4927858, assigned to Huntsman Chemical Corporation (Salt Lake City, UT), May 22,1990. 

Burkett and M. Carnahan, Method for forming a foam product with enhanced fire resistance and product produced thereby, US Patent 6383608, May 7,2002. 

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Commonly used isocyanates are toluene dhsocyanate, methylene diphenyl isocyanate, and polymeric isocyanates. Polyols used are macroglycols based on either polyester or polyether. The former [poly(ethylene phthalate) or poly(ethylene 1,6-hexanedioate)] have hydroxyl groups that are free to react with the isocyanate. Most flexible foam is made from 80/20 toluene dhsocyanate (which refers to the ratio of 2,4-toluene dhsocyanate to 2,6-toluene dhsocyanate). High-resilience foam contains about 80% 80/20 toluene dhsocyanate and 20% poly(methylene diphenyl isocyanate), while semi-flexible foam is almost always 100% poly(methylene diphenyl isocyanate). Much of the latter reacts by trimerization to form isocyanurate rings. 

Polyurethane foams are formed by reaction with glycerol with poly(propylene oxide), sometimes capped with poly(ethylene oxide) groups with a reaction product of trimethylolpropane and propylene oxide or with other appropriate polyols. A typical reaction sequence is shown below, in which HO—R—OH represents the diol. If a triol is used, a cross-linked product is obtained. 

Polyester Polyols. Initially polyester polyols were the preferred raw materials for polyurethanes, but in the 1990s the less expensive polyether polyols dominate the polyurethane market. Inexpensive aromatic polyester polyols have been introduced for rigid foam appHcations. These are obtained from residues of terephthaHc acid production or by transesterification of dimethyl terephthalate (DMT) or poly(ethylene terephthalate) (PET) scrap with glycols. 

In most cases, these active defoaming components are insoluble in the defoamer formulation as weU as in the foaming media, but there are cases which function by the inverted cloud-point mechanism (3). These products are soluble at low temperature and precipitate when the temperature is raised. When precipitated, these defoamer—surfactants function as defoamers when dissolved, they may act as foam stabilizers. Examples of this type are the block polymers of poly(ethylene oxide) and poly(propylene oxide) and other low HLB (hydrophilic—lipophilic balance) nonionic surfactants. 

Chapman et al. [131] reported the synthesis of poly(ethylene oxide) (PEO) supported dendritic f-BOC-poly(a, c-L-lysines). These dendritic polymers termed as hydramphiphiles formed foams possessing good temporal stability in aqueous solution. Scrimin et al. [132] synthesized a three-directional polypeptide having uses in membrane permeability modulation. Decapeptide fragments were linked to TREN [tris(2-aminoethyl)amine] core. 

Poly(ethylene), high density 1953 1955 Thermoplastics, foams ... 

Blends of poly (ethylene terephthalate) (PETP) and polypropylene (PP) with different rheological properties were dry blended or compounded, and extrusion foamed using both physical blowing and chemical agents, and the foam properties compared with those of foam produced from the individual components in the absence of compatibilisers and rheology modifiers. The foams were characterised by measurement of density, cell size and thermal properties. Low density foam with a fine cell size was obtained by addition of a compatibiliser and a co-agent, and foamed using carbon dioxide. The presence of PP or a polyolefin-based compatibiliser did not effect... 

By foaming an immiscible blend system of a poly(ethylene glycol)PEG/ polystyrene (PEG/PS), Taki et al. detected a similar foaming behavior as well as a bimodal cell size distribution [78], While smaller cells formed in the more... 

Taki K, Nitta K, Kihara S, Ohshima M (2005) C02 foaming of poly(ethylene glycol)/ polystyrene blends relationship of the blend morphology, C02 mass transfer, and cellular stmcture. J Appl Polym Sci 97 1899-1906... 

Scheme 4.14. Lysine-based, dendritic terminated poly(ethylene oxide) was described as hydroamphiphiles due to the formation of stable foams in water.

Step-growth polymerization, 22, 24-25, 23, 84-86, 86,90-92,114-115, 261 compared with chain-growth polymerization, 88-89, 88-89 interfacial polymerization, 91-92 laboratory activities on synthesis of nylon, 228-230 synthesis of polyesters in the melt, 231-233 synthesis of polyurethane foam, 234-237 molar mass and, 86, 86 polycondensation of poly ethylene terephthalate), 90-91 polymers produced by, 86 types of monomers for, 90 Stereochemistry, 28, 37-39,41-42, 70 tacticity, 103-105 Stereoisomers, 41 Stereoregularity, 70 Stiffness, 142, 261 Strain, 142-143, 261 Strength... 

The high hydrophobicity of silicones can complicate their use in some applications. For example, proteins can undergo denaturation in contact with silicones [1]. In such cases, the siloxane can be modified to include a hydrophilic domain. This is typically accomplished by functionalizing the silicone with a hydrophilic polymer such as poly(ethylene oxide)(PEO). Silicone surfactants of this type have found widespread use as stabilizers for polyurethane foams, and have been investigated as a structurant to prepare siloxane elastomers for biomaterials... 

U.R.Vaidya and V.M.Nadkarai (1987). Unsaturated Polyester Resin Foam Poly(ethylene terephthalate) Waste-Part 1 Synthesis and Characterization. Ind. Eng. Chem. Res., Vol. 26, pp. 194—198. 

By chemical recovery of polyester [poly(ethylene terephthalate) (PET)] (Chapter 16) and PU wastes, by alcoholysis or by aminolysis (Chapter 20), new polyols are obtained that can be used in rigid PU foam fabrication. The vegetable oil polyols, obtained by chemical transformation of the double bonds in vegetable oils in various hydroxyl groups are a very attractive route to obtain polyols from renewable resources (Chapter 17). 

BR and/or poly(ethylene-co- vinyl or acrylic monomer), e.g., EVAc EPDM polynorbornene having carboxylic, and carboxylic ester groups PVC blends with crosslinked NBR for foamed floating devices DOIP plasticized PVC blended with TPU and EVAc... 

PE with EVAc, CPE, BR, etc., have been chemically foamed at T = 150-210°C 5 to 95 wt% of LDPE or LLDPE with EAA PE with either poly(ethylene-co-vinylcarboxylate) or an acrylate PP with an ionomer and EBA-GMA PP with an ionomer, EBA-GMA and EPDM PO with a core-shell graft copolymer MBS-type PP with acidified-PP, or a carboxylic acid-modified EPR, SMM-MA, and either EMMA-GMA or EVAc-GMA LLDPE, PMMA and SEBS, EPR, or ethylene-styrene block copolymer (ES)... 

Poly(ethylene terephtlialate) (PET) has become a major synthetic polymer during the past forty years. Significant cotnmercial markets [1] have been developed for its application in textile and industrial fibers, films, and foamed articles, containers for carbonated beverages, water and otlier liquids, and thermoformed applications (e.g. dual ovetiable containers). 

Japon, S., Leterrier, Y. and Manson, J.-A. E., Recycling of poly(ethylene terephdialate) into closed-cell foams, Polym. Eng. ScL, 40, 1942 (2000). Letenier, Y., Laboratoiie de Technologie des Composites et Polymeres (LTC), Ecole Polytechnique Eederale de Lausanne (EPEL), CH-1015 Lausanne, Switzerland, personal communication, 2001. 

Starch utilization in plastic and rubber compositions began in the 60s and 70s, with oxidised starch in rubber and other polymers, such as urethane foams, poly(vinyl alcohol) and copolymers of poly(ethylene-co-acrylic acid) formulations, and as a filler in plasticized polyvinyl chloride (PVC) [37,39]. In another technique, gelatinized starch was mixed with PVC latex and the water was removed to give a PVC-starch composition, which was mixed with a PVC plasticizer such as dioctyl phthalate (DOP). 

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