aging

This refers to the change that occurs over time when things change. In the process of change over time, terms such as maturation, aging, fermentation, curing, and steaming are used when the change is desirable. When the change is undesirable or the properties are deteriorating, terms such as aging, maturation, and ageing are used. These terms are used in specific ways depending on the field of expertise. For example,
(1) Aging: In the manufacturing process of viscose rayon, it refers to leaving the material until it has a viscosity suitable for spinning. In brewing alcohol, it refers to leaving the material to bring out its flavor. In the rubber industry, it refers to the process whereby the properties of vulcanized rubber improve when the material is left for a certain period of time after the mastication and kneading processes as broken molecular chains recombine. In compounded latex, it also refers to the stabilization of latex over time. In this way, aging refers to the improvement in properties over time after the molding process is almost complete, and is also known as aging. In crystal growth, it can also be used to refer to growing the crystals larger.
(2) Curing: In the fields of adhesives and paints, this refers to improving performance over time.
(3) Steaming: In the dyeing industry, this refers to steam treatment to improve dye fixation (dyeability) after the dyeing process.
(4) Aging: This refers to the deterioration of a material's properties over time, and is used in the same sense as material degradation. Aging or deterioration refers to the deterioration of a material's properties over time (color change, cracks, loss of strength, loss of performance, etc.) due to decomposition caused by the influence of the external environment (heat, light, radiation, chemicals, microorganisms, mechanical stimuli, etc.).
(5) Aging: In the process of producing viscose rayon, when viscose is left exposed to air, the degree of polymerization of cellulose decreases.
(6) Aging: This refers to the process by which living organisms grow older. In the field of biology, the process by which cells age is called cellular aging or cell division aging. In humans, aging is also referred to as becoming more mature and experienced.
Additionally, in the field of metals, the phenomenon in which the strength of a material increases over time is called aging (hardening). Generally, there is a method called heat treatment in which heat is applied and the material is left to stand in order to improve the strength and other properties of materials after forming. When performance deteriorates due to heat, this is called thermal degradation. When the performance of a material deteriorates due to repeated exposure to external stimuli (heat, force, etc.), this is called fatigue. [See alternative terms] Age hardening

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

時間の経過に従って，物事が変化していく経時変化をいう．経時変化していく過程で，変化が望ましい場合には，熟成，ねかし，ならし，養生，蒸しなどの用語が使われている．変化が望ましくないか，性質が低下していく場合には，老化，老成，加齢などの用語が使われている．これらの用語は専門分野で特有な使われ方をしている．たとえば，
(1)熟成：ビスコースレーヨンの製造工程において，紡糸に適する粘度まで放置することをいう．酒の醸造では，旨みをださせるため放置することをいう．ゴム工業では，素練り，混練の工程後，一定の時間放置すると，切断した分子鎖が再結合して加硫ゴムの性質が向上することをいう．配合ラテックスにおいてもラテックスが経時変化で安定することをいう．このように，熟成とは，成形加工の操作がほぼ完了した後，時間をかけることによって性質が向上することをいい，ねかしともよばれている．結晶成長において，結晶を大きく成長させることなどもいう．
(2)養生：接着や塗料の分野で，時間経過により性能を向上させることをいう．
(3)蒸し：染色分野で，染色工程後，染料の固着(染着性)を高めるために蒸気処理することをいう．
(4)老化：経過時間とともに材料の性質が悪くなることをいい，材料の劣化と同じ意味で使用されている．外部環境(熱，光，放射線，薬品，微生物，機械的刺激など)からの影響により分解などが起こり，時間の経過に従い材料の性質が悪くなっていく(色変化，亀裂，強度低下，性能低下など)ことを，老化または劣化という．
(5)老成：ビスコースレーヨンを製造する工程で，ビスコースを空気中に放置すると，セルロースの重合度が低下することをいう．
(6)加齢：生物が年をとっていくことであるが，生物の分野では，細胞が老化していく過程を細胞加齢，細胞分裂加齢という．また，人では加齢により老熟，老練するという．
このほかに，金属の分野では，時間経過により材料の強度が増す現象を時効(硬化)とよんでいる．一般に，成形加工後の材料の強度などの性能を向上させる目的で，熱を加えて放置する熱処理という方法がある．熱によって性能が悪くなる場合は，熱劣化という．繰り返し外部刺激(熱，力など)をうけ，材料の性能が悪くなる場合を疲労という．[別用語参照]時効硬化

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