Foams heat resistant

There is also growing interest in multi-phase systems in which hard phase materials are dispersed in softer polyether diols. Such hard phase materials include polyureas, rigid polyurethanes and urea melamine formaldehyde condensates. Some of these materials yield high-resilience foams with load deflection characteristics claimed to be more satisfactory for cushioning as well as in some cases improving heat resistance and flame retardancy. 

PMI more heat-resistant and suitable for foam manufacture. 

The PP is produced by melt-kneading PP, an isoprene monomer and a radical polymerisation initiator, which has a high melt viscosity and a high melt tensile strength and is difficult to cause drawdown. Foamed articles made therefrom have a low density, high closed cell content, good appearance and excellent heat resistance. 

This patent is a reissue (RE 34607). The composition described, capable of forming foams with excellent mechanical properties and heat resistance, is made of (a) 14-80 wt.% of a propylene-ethylene random copolymer having an ethylene content of 1.5-6 wt.%, (b) 10-60 wt.% of a propylene-ethylene random copolymer having an ethylene content of 0.2-1.0 wt.%, (c) 10-60 wt.% of a linear low-density polyethylene, and (d) 1-30 pbw, per 100 pbw of the above resin composition, of a foaming agent. JAPAN... 

Sekisui Plastics is reported to have developed two types of heat resistant plastics foam one is PETP foam, capable of resisting temps, of up to 220C and the other is closedcell PP foam, resistant to temps, of up to 145C. Brief details are noted. 

Blowing agents swell a thick carbon foam which envelopes the object in a heat-resistant layer... 

EVA reins can be conveniently crosslinked by both peroxide or irradiation to enhance the mechanical properties and the heat resistance. It is the crosslinking, coupled with the inherent rubbery nature of the polymer, which makes EVA suitable for production of tough and abrasion resistant foams, especially suitable for footwear applications. Crosslinked EVA foams can be manufactured by two methods (8) ... 

In order to overcome this drawback, the concept of selective blending was exploited. Selective blending of PPE with low-viscous PS allowed one to control the microstructure, to refine the phase size, and to adjust the foaming characteristics of the individual phases of PPE/SAN blends. Appropriate blend compositions allowed simultaneous nucleation and cooperative expansion of both phases, generally leading to bimodal cell size distributions in the micron range. Due to cell nucleation and growth in both blend phases, the density could be further reduced when compared to PPE/SAN blends. Moreover, the presence of coalesced foam structure and particularly macroscopic defects could be avoided, and the matrix of the foamed structure was formed by the heat resistant PPE/PS phase. 

Molded foam copolymers with 10-30% glycidyl acrylate may be crosslinked by heating in the presence of polyamines. Heat resistance may be increased to as high as 150°C. by this treatment (25). Use of certain allyl or diallyl esters to control the crosslinking of polystyrene to the desired very light extent has been disclosed as a means of obtaining foams of improved and regular cell structure (135). Block copolymers of polystyrene, polydiene (particularly polyisoprene), and polystyrene... 

Similar to other materials, foams have limitations. No foam is fireproof but many of them can be made flame-resistant. Phenolics and silicones have excellent heat resistance but could crumble when subjected to vibrational stress if not modified. There are foams that can be affected by solvents, but fluorinated types resist them. However these plastics with modifiers provide acceptable performances. 

Acetal translucent crystalline polymer is one of the stiffest TPs available. It provides excellent hardness and heat resistance, even in the presence of solvents and alkalies. Its low moisture sensitivity and good electrical properties permit direct competition with die-cast metal in a variety of applications. In addition, acetal has extremely high creep resistance and low permeability. Acetal is also available as a copolymer (Hoechst Celanese Corp. s Celcon) for improved processability. The homopolymer (DuPont s Delrin) has a very low coefficient of friction and its resistance to abrasion is second only to nylon 6/6. Acetals are frequently blended with fibers such as glass or fluorocarbon to enhance stiffness and friction properties. Acetal is not particularly weather-resistant, but grades are available with UV stabilizers for improved outdoor performance. Acetal, whether homopolymer or copolymer, is not used to any significant degree in forming structural foams. 

Unitika Textiles in Japan has also developed a technology to manufacture foam-moulded products with good heat resistance using PLA. 

Heat-resistant [218] soft foams were prepared from the blends of hdPE with E-P random copolymers. The azodicarbanamide acts as a thermal antioxidant and the crosslinking of the blend was increased by electron beam radiations and foamed at 225 °C with 2320% expansion. A blend of 35 wt.% PE-PP (8 92), 15 wt.% E-P block copolymers, and 50 wt.% EPDM showed accelerated weathering resitance [219] 1000 h probably due to crosslinking between constituents of the block copolymer, polyblend and EPDM. The effect of filler and thermodynamic compatibility on kaolin-filled PE-PP blend was studied by Lipatov and coworkers [220]. The thermodynamic interaction parameter (%) decreased and thermodynamic stability increased by filler addition, the degree of crystallinity decreased with increasing thermodynamic compatibility of the components due to sharp decrease in the phase separation rate during cooling. 

Phenolic foams were first used in Germany in the early 1940 s to replace Balsa wood for use in aircraft (2). Notwithstanding the fact that both phenolic resin and phenolic foam itself have long histories, newer applications have imdergone slow development. Quite recently, however, the heat resistance as well as fire resistance qualities of this foam have focused attention to its wide uses. 

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