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Old 23.05.2013, 07:58
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T72 T72 is offline
Konkari
 
Join Date: Jan 2004
Location: Tuusula
Posts: 2,885
T72 on oikealla tiellä
Yritin joskus pähkäillä miksi se kuitu kuivuttuaankin vielä "elää". Ensimmäisenä mieleentuleva asia on hartsin kutistuminen, toinen mikä netissä surffailemalla tuli esiin on että hartsilla on tietty lämpötila Tg jonka ylitettyään sen ominaisuudet muuttuu hieman pehmeämmiksi. Noi lämpötilat ei ole hirveän korkeita, vain noin 60 astetta, mikä voisi juuri mustassa autossa nousta ongelmaksi.

http://www.azom.com/article.aspx?ArticleID=986

Once cured, thermosets will not become liquid again if heated, although above a certain temperature their mechanical properties will change significantly. This temperature is known as the Glass Transition Temperature (Tg), and varies widely according to the particular resin system used, its degree of cure and whether it was mixed correctly. Above the Tg, the molecular structure of the thermoset changes from that of a rigid crystalline polymer to a more flexible, amorphous polymer. This change is reversible on cooling back below the Tg. Above the Tg properties such as resin modulus (stiffness) drop sharply, and as a result the compressive and shear strength of the composite does too. Other properties such as water resistance and colour stability also reduce markedly above the resin’s Tg.
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