{"id":1060,"date":"2026-09-14T08:56:27","date_gmt":"2026-09-14T08:56:27","guid":{"rendered":"https:\/\/isbmmolding.com\/?p=1060"},"modified":"2026-09-14T08:56:27","modified_gmt":"2026-09-14T08:56:27","slug":"what-is-hot-fill-blow-molding-and-how-does-it-work","status":"publish","type":"post","link":"https:\/\/isbmmolding.com\/ja\/what-is-hot-fill-blow-molding-and-how-does-it-work\/","title":{"rendered":"What is hot fill blow molding and how does it work?"},"content":{"rendered":"

What is hot fill blow molding and how does it work?<\/h1>\n
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Hot fill blow moulding \u2014 also called heat-set stretch blow moulding \u2014 is a variant of the standard ISBM process that produces PET bottles capable of being filled with hot product at temperatures of 85\u201395\u00a0\u00b0C without deforming. The key difference from standard ISBM is the blow mould temperature: standard (cold-fill) ISBM runs the blow mould at 8\u201312\u00a0\u00b0C to cool the bottle rapidly after blowing; hot-fill ISBM runs the blow mould at 100\u2013130\u00a0\u00b0C to induce partial crystallisation in the PET bottle wall during the blow step. This crystallisation \u2014 called heat-setting \u2014 gives the bottle dimensional stability at hot-fill temperatures.<\/p>\n

Why Standard PET Bottles Cannot Be Hot-Filled<\/h2>\n

Standard amorphous PET bottles produced by cold-fill ISBM are dimensionally unstable above approximately 60\u201365\u00a0\u00b0C \u2014 the glass transition temperature (Tg) of PET. Above Tg, the amorphous polymer chains in the bottle wall soften and can deform under the internal pressure and gravity of a hot-filled product. A standard cold-fill PET bottle filled with hot juice at 90\u00a0\u00b0C will shrink, wrinkle, and distort within seconds of filling, making it commercially unacceptable. Hot-fill packaging requires either a heat-set PET bottle, an HDPE or PP bottle (which are inherently more thermally stable than amorphous PET above Tg), or a glass bottle.<\/p>\n

How Heat-Setting Works<\/h2>\n

Heat-setting is the induction of limited, controlled crystallisation in the PET bottle wall by holding the blown bottle against a hot mould surface for a defined time. PET crystallises when held above its crystallisation onset temperature (approximately 130\u2013140\u00a0\u00b0C) for sufficient time. In the heat-set ISBM process, the blow mould is heated to 100\u2013130\u00a0\u00b0C, and the blown bottle is held against the mould wall for 2\u20136 seconds longer than in standard cold-fill production. During this hold time, the PET bottle wall develops a degree of crystallinity of 25\u201335%, measured by density or DSC analysis.<\/p>\n

The crystallised PET has a Tg approximately 10\u201315\u00a0\u00b0C higher than amorphous PET due to the constraints imposed by the crystal structure on chain mobility. More importantly, the crystallised regions do not soften as readily as amorphous regions above Tg, giving the heat-set bottle dimensional stability at fill temperatures that would distort a standard cold-fill bottle. Heat-set bottles can be filled at up to 90\u201395\u00a0\u00b0C (depending on the degree of heat-setting) without significant dimensional change, though they still experience modest shrinkage (1\u20133% of bottle volume) on cooling from fill temperature to ambient, which must be accommodated by bottle design with vacuum panels or sufficient headspace.<\/p>\n

\"Hot<\/p>\n

ISBM process parameters for hot-fill heat-set production \u2014 blow mould temperature is the critical parameter that differentiates heat-set from cold-fill ISBM production.<\/p>\n

Products Filled by the Hot-Fill Process<\/h2>\n

Hot-fill is used for beverages and food products that require heat treatment for pasteurisation or sterilisation during filling:<\/p>\n