zilembo

Pulasitiki jekeseni akamaumba Shrinkage

Pulasitiki jekeseni akamaumba shrinkage ndi chimodzi mwazinthu zomwe kutentha kumatenthedwa. Mulingo wa jekeseni wakuthwa wa jekeseni umafunika pakudziwitsa kukula kwa magwiridwe antchito. Mtengo umawonetsera kuchuluka kwa chidule chomwe cholembedwera pambuyo pake chachotsedwa mu nkhungu kenako chimakhazikika ku 23C kwakanthawi kwamaola 48.

Shrinkage imadziwika ndi equation yotsatirayi:

S = (Lm-Lf) / Lf * 100%

Komwe S ndi kachulukidwe ka nkhungu, Lr magawo omaliza a ntchito (mu. kapena mm), ndi Lm mawonekedwe a nkhungu (mkati kapena mm). Mtundu ndi gulu lazinthu zapulasitiki ndizosintha mosiyanasiyana. Kuchepetsako kumatha kukhudzidwa ndimitundu ingapo monga kuzizira kwamphamvu kogwirira ntchito, jakisoni ndikukhala ndi zovuta. Kuphatikiza kwa zowonjezera komanso zowonjezera, monga magalasi a galasi kapena mchere wochulukirapo, zitha kuchepetsa kuchepa.

Kupindika kwa zinthu za pulasitiki mutatha kuzikonza ndizofala, koma ma polima amtundu ndi amorphous amacheperachepera. Zida zonse zamapulasitiki zimanyinyirika zikagwiritsidwa ntchito chifukwa chothinikizika kwawo komanso kupindika kwa matenthedwe akamazizira pakukonza kutentha.

Zipangizo za amorphous zimakhala zochepa. Pamene zinthu amorphous kuziziritsa pa nthawi yozizira ya ndondomeko jekeseni akamaumba, iwo retun kwa plymer okhwima. Maunyolo a polima omwe amapanga zinthu zopanda mawonekedwe alibe mawonekedwe achindunji. Zitsanzo za zida za amorphous ndi polycarbonate, ABS, ndi polystyrene.

Zipangizo zamakina zimakhala ndi malo osungunuka amtundu wa crystalline Maunyolo a polima amadzimangirira okha pakulamula kwa ma molekyulu. Madera olamulidwawa ndi makhiristo omwe amapangidwa polima atakhazikika kuchokera kumtunda kwake. Pazinthu zopangidwa ndi semicrystalline polima, mapangidwe ndi kulongedza kochulukirapo kwa maunyolo am'magawo amtunduwu. jekeseni wa jekeseni wa michere ya semicrystalline ndiwokwera kwambiri kuposa zida za amorphous. Zitsanzo za zida za crystalline ndi nayiloni, polypropylene, ndi polyethylene. Mndandanda wazinthu zingapo zamapulasitiki, amorphous ndi semicrystalline, ndi kupindika kwawo kwa nkhungu.

Shrinkage ya thermoplastics /%
zakuthupi kuchepa kwa nkhungu zakuthupi  kuchepa kwa nkhungu zakuthupi kuchepa kwa nkhungu
ABS 0.4-0.7 polycarbonate 0.5-0.7 PPO 0.5-0.7
Akiliriki 0.2-1.0 PC-ABS 0.5-0.7 polystyrene 0.4-0.8
ABS-nayiloni 1.0-1.2 Ma PC-PBT 0.8-1.0 Polysulfone 0.1-0.3
Acetal 2.0-3.5 PC-PET 0.8-1.0 PBT 1.7-2.3
Nayiloni 6 0.7-1.5 Polyethylene 1.0-3.0 PET 1.7-2.3
Nayiloni 6,6 1.0-2.5 Polypropylene 0.8-3.0 TPO 1.2-1.6
PEI 0.5-0.7        

Kusintha kwamasinthidwe kumatanthauza kuti kusinthira ma polima amorphous ndikwabwino kwambiri kuposa ma polima amtundu wa crystalline, chifukwa ma crystallites amakhala ndi kulumikizidwa kolamulidwa komanso kulumikizana bwino kwa maunyolo a polima, kusintha kwa gawo kumawonjezera kuchepa. Koma ndi mapulasitiki amorphous, ichi ndiye chokhacho chomwe chimawerengedwa mosavuta.

Kwa ma polima amorphous, mitengo ya shrinkage siyotsika kokha, koma shrinkage yokha imachedwa kuchitika. Pama polima amorphous monga PMMA, shrinkage idzakhala mu dongosolo la 1-5mm / m. Izi ndichifukwa chozizira kochokera pafupifupi 150 (kutentha kwa kusungunuka) mpaka 23C (kutentha kwapakati) ndipo kumatha kukhala kogwirizana ndi koyefishienti kakukula kwa matenthedwe.


Post nthawi: Sep-19-2020