RUBBER KNOWLEDGE
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sporco stampo
(mould fouling)
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" LO STAMPAGGIO DELLA GOMMA:
I MATERIALI E LA TECNOLOGIA "
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Mold fouling results in material wastage, requires regular cleaning of the mold, and generally necessitates the use of mold surface treatments, all of which add to production costs. The phenomenon of mold fouling occurs when rubber products are injection-molded and a thin deposit of material remains on the mold surface with repeated injection cycles. This effect depends on various factors, including the chemical nature of the rubber compound, mold surface composition, and injection-molding conditions. Experimental investigation suggested that the design and location of the gate influenced both mould filling pattern and the position of rubber deposition within the cavity. Mold fouling has commercial implications as it impedes heat transfer, creates defects on the molding surface, results in material wastage, and adds to production costs. Spraying the mold with a release agent is a temporary solution, although elastomer compounds can be formulated with superior mold-release characteristics. Despite the extensive range of injection-molded rubber products produced commercially, a detailed understanding of this phenomenon's origins has not been well achieved. It is known from studies that the degree of mould fouling depends on many factors [1,2,3,4,5]. The origins of mould fouling are considered to involve:
(i) chemical reactions occurring between the rubber compound and the metallic surface of the mould;
(ii) low molecular components separated from the compound becoming deposited on the mould surface;
(iii) solid components present in the compound adhering to the metallic surface.
[1] "Mould fouling of elastomers during injection moulding, P. R. Hornsby, I. Singh, J. R. Daley & J. Firth (2006), Plastics, Rubber and Composites, 35:8
[2] "Mold fouling in rubber injection molding: a review" di K. Subramanian, S. Devulapalli, S. Seshadri, Polymer Engineering and Science, vol. 53, n. 8, pp. 1621-1634, 2013
[3] "Effects of mold fouling on the properties of injection molded thermoplastic elastomers" di T. A. Nguyen e A. L. Yarin, Polymer Engineering and Science, vol. 48, n. 4, p.747, 2008
[4] "Rubber Molding: A Practical Guide" di John A. Lindsay, Hanser Publications, 2005
[5] "Rubber Technology Handbook" di Werner Hofmann, Hanser Publications, 2001
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