Tuesday, April 7, 2009

A new emerging technology in injection molded foam industry is crosslinked injection molding technique called XL-IM Technical Brochure, Injection Molding of Cross-Linked Engage Foams foot wear Applications, DuPont Dow Elastomers, Revised in August 2002.. This is a unique single step operation for finished products. Initially developed for footwear industries and later on, advanced, for non-shoe business applications. The closed cell crosslinked molded foam produced by the Polyolefin elastomers take advantage of both out-mold-expansion or OME and XL-IM providing an innovative technology for shaping foam parts with greater finish, durability and details.

Monday, March 23, 2009

Draft: Innovations in Polyolifin Foam Technology

Understading of Polyethylene Crosslinked Foam

When producing crosslinked molded foams you will find huge benefits in using polyolefin elastomers (POE) as compared with ethylene vinyl acetate EVA copolymers. Copolymers such as low density poly(ethylene-co-octene) and (polyethylene-co-butene) are most amenable to this process whereby foaming occurs upon opening the mold. The stabilization of foam occurs due to crosslinking reaction during a cure time in the mold. Foam formulations, based on POE, provide performance improvements including; lighter product at equivalent softness, low temperature flexibility, better resilience and rebound, higher heat stability, lower abrasion, and better quality. Perhaps, the greatest advantage polyolefin foam has over EVA foam is a lower heat-shrinkage rate, about one-third to one-tenth of conventional EVA foam.

The choice of materials for polyolefin foam manufacture includes only the homo and copolymers of ethylene and propylene. This range has recently increased with the introduction of metallocene catalyst in the synthesis of polyolefins, called mPOE. These metallocene catalysts enable a high degree of control of the polymer structure resulting in enhanced properties including increased melt strength, tensile strength and elongation as well as better processing flexibility. With greater regularity of chain structure and a broad molecular weight distribution, high performance grades of mPOE are produced with increased long chain branching that can be used for molded foams as well as extrusion applications like tubing profiles and wires and cables.

In contrast to polyurethane foam, the polyolefin foams are relatively recent additions to the range of polymeric foam materials. In a short time polyolefin foams have found a use in almost every industry including packaging, sports and leisure, baby care and toys, insulation, automotive, military, aircraft, floatation, furniture, footwear and others. This ability to reach this wide range of products is the result of the scope of properties inherent in these foams. Foams can hard or soft, resilient and stable. While hard and less flexible foams can be made using polypropylene or high density polyethylene as the basic polymer, softer materials are obtained using either ethylene or propylene co-polymers such as ethylene vinyl acetate (EVA). This ability to vary foam properties by changes in the polymer is similar to that seen in polyurethane foams, although the technologies are very different. While almost all polyurethane foams result from liquid technology with in situ polymerization and blowing, polyolefin foams are all produced starting with the basic solid compounds of thermoplastic polymers [1].

The chemical blowing agents (CBA) used for polyolefin foams that are injection molded include chemicals such as Azodicarbonamide (ADC). Since the foams are closed cell, the blowing agent remains in the foam and can affect both the foam properties and post manufacturing operations.
The selection of raw materials is made primarily on the basis of ensuring that melt processing temperatures should not exceed 120 C during compounding and extrusion [2]. This is the typical processing temperature for LDPE compounds with a peroxide crosslinking agent. Normally LDPE and EVA, alone or blended with little or no addition of functional polymers, are used. With melt flow indices in the region of 2.0-5.0g/min. these polymers, particularly EVA, will crosslink reasonably efficiently with peroxides and process at acceptably low temperatures. However, because polypropylene, HDPE and LLDPE require higher processing temperatures and slow crosslinking, they are not preferred. Particularly, polypropylene undergoes chain scission and degradation rather than free radical crosslinking reaction with peroxide.

1- Lee, S.T. and Park, C.B. Polymeric Foams: understanding foaming technology, CRC Press, Boca Raton, FL 2005.
2- Klempner, Dand Frisch, K.C., Handbook of Polymeric Foams and Foam Technology, Hanser, Munich, 1991.

Friday, March 20, 2009


"He has subjected to you, as from Him, all that is in the heavens and on earth: behold, in that are Signs indeed for those who reflect. Give full measure and full weight in justice, and wrong not people in respect of their goods".

Welcome to SunQura your site for revolutionary plastic innovations. The world is changing fast these days, and the world of plastics is at the front of the pack. I will make sure to pack your daily issue with lots of features and links to the latest and best plastics info, and it will always be a quick read so you can catch up with a quick look. And if you have news, send it to me, and I will make sure it reahs to our reader. Thank you