{"id":775,"date":"2025-12-11T08:29:56","date_gmt":"2025-12-11T08:29:56","guid":{"rendered":"https:\/\/www.materialstests.com\/?p=775"},"modified":"2025-12-11T08:29:58","modified_gmt":"2025-12-11T08:29:58","slug":"understanding-astm-d4974-hot-air-shrinkage-test-for-yarn-and-cord","status":"publish","type":"post","link":"https:\/\/www.materialstests.com\/cs\/news\/understanding-astm-d4974-hot-air-shrinkage-test-for-yarn-and-cord.html","title":{"rendered":"Porozum\u011bn\u00ed norm\u011b ASTM D4974: Zkou\u0161ka smr\u0161\u0165ov\u00e1n\u00ed p\u0159\u00edze a \u0161\u0148\u016fr hork\u00fdm vzduchem"},"content":{"rendered":"

Vyztu\u017eovac\u00ed p\u0159\u00edze a nit\u011b pro pr\u016fmyslov\u00e9 hadice<\/h2>\n\n\n\n

Syntetick\u00e9 p\u0159\u00edze, jako je nylon a polyester, jsou zn\u00e1m\u00e9 sv\u00fdm relativn\u011b vysok\u00fdm smr\u0161\u0165ov\u00e1n\u00edm p\u0159i p\u016fsoben\u00ed tepla. Pro zachov\u00e1n\u00ed st\u00e1l\u00fdch fyzik\u00e1ln\u00edch a mechanick\u00fdch vlastnost\u00ed po vytla\u010dov\u00e1n\u00ed se tyto p\u0159\u00edze b\u011b\u017en\u011b podrobuj\u00ed tepeln\u00e9mu vytvrzov\u00e1n\u00ed. Tento proces zahrnuje nata\u017een\u00ed p\u0159\u00edze pod \u0159\u00edzen\u00fdm nap\u011bt\u00edm p\u0159i zv\u00fd\u0161en\u00e9 teplot\u011b, \u010d\u00edm\u017e se trvale zm\u011bn\u00ed krystalinita a vnit\u0159n\u00ed struktura vl\u00e1kna. Tento proces zaji\u0161\u0165uje, \u017ee si p\u0159\u00edze zachov\u00e1 svou rozm\u011brovou stabilitu a mechanick\u00e9 vlastnosti i p\u0159i n\u00e1sledn\u00e9m vysokoteplotn\u00edm zpracov\u00e1n\u00ed.<\/p>\n\n\n\n

Volbou p\u0159esn\u00fdch podm\u00ednek tepeln\u00e9ho vytvrzov\u00e1n\u00ed - v\u010detn\u011b teploty, nap\u011bt\u00ed a doby expozice - mohou v\u00fdrobci upravit smr\u0161t\u011bn\u00ed, pevnost a pru\u017enost p\u0159\u00edze tak, aby spl\u0148ovala konkr\u00e9tn\u00ed po\u017eadavky na vlastnosti. Spr\u00e1vn\u011b tepeln\u011b vytvrzen\u00e9 p\u0159\u00edze odol\u00e1vaj\u00ed deformac\u00edm b\u011bhem navazuj\u00edc\u00edch proces\u016f, jako je vulkanizace pry\u017ee, a poskytuj\u00ed dlouhodobou stabilitu v n\u00e1ro\u010dn\u00fdch pr\u016fmyslov\u00fdch aplikac\u00edch.<\/p>\n\n\n\n

ASTM D4974: \u00da\u010del a aplikace<\/h2>\n\n\n\n

Norma ASTM D4974 se \u0161iroce pou\u017e\u00edv\u00e1 pro tepeln\u011b odoln\u00e9 p\u0159\u00edze, v\u010detn\u011b nylonu, polyesteru a aramidov\u00fdch vl\u00e1ken. Tyto materi\u00e1ly se b\u011b\u017en\u011b pou\u017e\u00edvaj\u00ed v kordu pneumatik, v\u00fdztuh\u00e1ch p\u00e1s\u016f a dal\u0161\u00edch mechanick\u00fdch pry\u017eov\u00fdch v\u00fdrobc\u00edch (MRG), kter\u00e9 proch\u00e1zej\u00ed vulkanizac\u00ed. B\u011bhem vulkanizace je pry\u017e vystavena vysok\u00e9mu teplu, aby se dos\u00e1hlo jej\u00edch kone\u010dn\u00fdch mechanick\u00fdch a fyzik\u00e1ln\u00edch vlastnost\u00ed. Pokud m\u00e1 p\u0159\u00edze vysok\u00e9 tepeln\u00e9 smr\u0161t\u011bn\u00ed, m\u016f\u017ee b\u011bhem tohoto procesu zu\u017eovat sou\u010d\u00e1sti, jako jsou hadice nebo p\u00e1sy, a potenci\u00e1ln\u011b tak ohro\u017eovat rozm\u011bry a v\u00fdkonnost kone\u010dn\u00e9ho v\u00fdrobku.<\/p>\n\n\n\n

P\u0159\u00edze s n\u00edzkou smr\u0161titelnost\u00ed, pe\u010dliv\u011b tepeln\u011b nastaven\u00e9 podle spr\u00e1vn\u00fdch parametr\u016f, vykazuj\u00ed p\u0159i vystaven\u00ed teplu minim\u00e1ln\u00ed rozm\u011brov\u00e9 zm\u011bny. D\u00edky tomu jsou vhodn\u011bj\u0161\u00ed pro pr\u016fmyslov\u00e9 aplikace vy\u017eaduj\u00edc\u00ed vysokou tepelnou stabilitu, konzistentn\u00ed v\u00fdkon a spolehlivou integraci s pry\u017e\u00ed nebo jin\u00fdmi materi\u00e1ly citliv\u00fdmi na teplo.<\/p>\n\n\n\n

 <\/h2>\n\n\n\n

Tester tepeln\u00e9ho smr\u0161t\u011bn\u00ed hork\u00fdm vzduchem: Zku\u0161ebn\u00ed postup<\/h2>\n\n\n\n

Na str\u00e1nk\u00e1ch Tester tepeln\u00e9ho smr\u0161t\u011bn\u00ed hork\u00fdm vzduchem<\/strong><\/a> je z\u00e1kladn\u00edm n\u00e1strojem pro prov\u00e1d\u011bn\u00ed zkou\u0161ek podle normy ASTM D4974. Tento p\u0159\u00edstroj vystavuje vzorek p\u0159\u00edze nebo \u0161\u0148\u016fry \u0159\u00edzen\u00e9mu such\u00e9mu teplu p\u0159i zachov\u00e1n\u00ed p\u0159esn\u00e9ho nap\u011bt\u00ed. Smr\u0161t\u011bn\u00ed se m\u011b\u0159\u00ed p\u0159\u00edmo v procentech, zat\u00edmco vzorek z\u016fst\u00e1v\u00e1 pod nap\u011bt\u00edm p\u0159i stanoven\u00e9 teplot\u011b.<\/p>\n\n\n\n

Postup podle normy ASTM D4974 obvykle zah\u0159\u00edv\u00e1 p\u0159\u00edzi na teplotu 177 \u00b0C po dobu 2 minut s p\u0159edp\u00ednac\u00edm zat\u00ed\u017een\u00edm 0,05 gramu na denier (gpd). U p\u0159\u00edz\u00ed s velmi mal\u00fdm smr\u0161t\u011bn\u00edm se pro p\u0159esn\u011bj\u0161\u00ed m\u011b\u0159en\u00ed doporu\u010duje ni\u017e\u0161\u00ed p\u0159edp\u011bt\u00ed 0,01 gpd. \u00daprava p\u0159edp\u011bt\u00ed m\u016f\u017ee ovlivnit \u00fadaj o smr\u0161t\u011bn\u00ed, p\u0159i\u010dem\u017e vy\u0161\u0161\u00ed hodnoty p\u0159edp\u011bt\u00ed obecn\u011b sni\u017euj\u00ed nam\u011b\u0159en\u00e9 smr\u0161t\u011bn\u00ed.
Tato zku\u0161ebn\u00ed metoda umo\u017e\u0148uje v\u00fdrobc\u016fm potvrdit, \u017ee si p\u0159\u00edze nebo kord zachov\u00e1v\u00e1 fyzik\u00e1ln\u00ed stabilitu za vysok\u00fdch teplot, co\u017e zaji\u0161\u0165uje p\u0159edv\u00eddateln\u00fd v\u00fdkon p\u0159i vulkanizaci a dal\u0161\u00edch tepeln\u00fdch procesech.<\/p>\n\n\n\n


Varianty testov\u00e1n\u00ed a \u00favahy<\/h2>\n\n\n\n

Je d\u016fle\u017eit\u00e9 si uv\u011bdomit, \u017ee ne v\u0161ichni v\u00fdrobci postupuj\u00ed p\u0159esn\u011b podle normy ASTM D4974. Rozd\u00edly v teplot\u011b, dob\u011b trv\u00e1n\u00ed nebo pou\u017eit\u00e9m nap\u011bt\u00ed mohou v\u00fdznamn\u011b ovlivnit nam\u011b\u0159en\u00e9 smr\u0161t\u011bn\u00ed. Nap\u0159\u00edklad p\u0159\u00edze testovan\u00e1 p\u0159i teplot\u011b 190 \u00b0C po dobu 10 minut p\u0159i ur\u010dit\u00e9m zat\u00ed\u017een\u00ed m\u016f\u017ee poskytnout odli\u0161n\u00e9 v\u00fdsledky ve srovn\u00e1n\u00ed s p\u0159\u00edz\u00ed testovanou podle normy ASTM D4974 p\u0159i teplot\u011b 177 \u00b0C po dobu 2 minut. Navzdory t\u011bmto rozd\u00edl\u016fm m\u016f\u017ee b\u00fdt p\u0159i zkou\u0161en\u00ed obou materi\u00e1l\u016f za stejn\u00fdch podm\u00ednek jejich tepeln\u00e9 smr\u0161t\u011bn\u00ed t\u00e9m\u011b\u0159 toto\u017en\u00e9.
Materi\u00e1ly s ni\u017e\u0161\u00edmi body t\u00e1n\u00ed nebo sn\u00ed\u017eenou tepelnou odolnost\u00ed vy\u017eaduj\u00ed upraven\u00e9 podm\u00ednky zkou\u0161en\u00ed, aby nedo\u0161lo k po\u0161kozen\u00ed vl\u00e1ken. Proto jsou parametry zkou\u0161ek smr\u0161t\u011bn\u00ed \u010dasto v\u00fdslovn\u011b uvedeny ve specifikac\u00edch materi\u00e1lu, co\u017e umo\u017e\u0148uje koncov\u00fdm u\u017eivatel\u016fm p\u0159esn\u011b porovnat v\u00fdsledky a vybrat nejvhodn\u011bj\u0161\u00ed p\u0159\u00edzi pro jejich pou\u017eit\u00ed.<\/p>\n\n\n\n

Zaji\u0161t\u011bn\u00ed kvality a spolehlivosti<\/h2>\n\n\n\n

Pro ov\u011b\u0159en\u00ed tepeln\u00e9 stability p\u0159\u00edz\u00ed a \u0161\u0148\u016fr je nezbytn\u00e9 pou\u017e\u00edvat horkovzdu\u0161n\u00fd tester tepeln\u00e9ho smr\u0161t\u011bn\u00ed. Prov\u00e1d\u011bn\u00edm zkou\u0161ek podle normy ASTM D4974 mohou v\u00fdrobci zajistit, \u017ee si materi\u00e1ly zachovaj\u00ed sv\u00e9 rozm\u011bry a mechanick\u00e9 vlastnosti p\u0159i vysokoteplotn\u00edch procesech, jako je nap\u0159\u00edklad vulkanizace pry\u017eov\u00fdch v\u00fdrobk\u016f.
Pro p\u0159esn\u00e9 m\u011b\u0159en\u00ed je z\u00e1sadn\u00ed porozum\u011bt nastaven\u00ed testov\u00e1n\u00ed, postupu a interpretaci v\u00fdsledk\u016f. Odborn\u00edci z oboru mohou pomoci p\u0159i zav\u00e1d\u011bn\u00ed testov\u00e1n\u00ed podle normy ASTM D4974 a pomoci v\u00fdrobc\u016fm a koncov\u00fdm u\u017eivatel\u016fm dos\u00e1hnout konzistentn\u00edch, vysoce kvalitn\u00edch materi\u00e1l\u016f, kter\u00e9 spolehliv\u011b funguj\u00ed v n\u00e1ro\u010dn\u00fdch pr\u016fmyslov\u00fdch aplikac\u00edch.<\/p>\n\n\n\n

\"Porozum\u011bn\u00ed<\/a><\/figure>","protected":false},"excerpt":{"rendered":"

Reinforcement Yarn and Thread for Industrial Hoses Synthetic yarns, such as nylon and polyester, are known for their relatively high shrinkage when exposed to heat. To maintain consistent physical and mechanical properties after extrusion, these yarns are commonly subjected to heat setting. This process involves stretching the yarn under controlled tension at elevated temperatures, permanently […]<\/p>","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-775","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.materialstests.com\/cs\/wp-json\/wp\/v2\/posts\/775","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.materialstests.com\/cs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.materialstests.com\/cs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.materialstests.com\/cs\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.materialstests.com\/cs\/wp-json\/wp\/v2\/comments?post=775"}],"version-history":[{"count":0,"href":"https:\/\/www.materialstests.com\/cs\/wp-json\/wp\/v2\/posts\/775\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.materialstests.com\/cs\/wp-json\/wp\/v2\/media?parent=775"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.materialstests.com\/cs\/wp-json\/wp\/v2\/categories?post=775"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.materialstests.com\/cs\/wp-json\/wp\/v2\/tags?post=775"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}