玻璃瓶的使用条件因为内装物的不同而有所差异，例如，在装瓶时高温充填、高温杀菌，或骤然冷却、消费过程中使用冰箱等，通常会有急剧的温度变化。据统计，玻璃瓶承受急冷、急热的温差大约是50℃，新瓶超过50℃，而回收瓶只有35℃左右。我国规定玻璃瓶罐的耐急冷温差指标是39℃，而美国、日本等国家规定为42℃。
(1)热冲击应力
从热应力观点看，瓶壁愈薄愈好。在相同的受热（或冷）情况下，厚壁处的温差越大，热应力就越大，玻璃瓶就愈容易破裂。图4-10是玻璃瓶在急热急冷条件下的应力分布情况。当玻璃瓶受到急热作用时，外表面的压应力远大于内壁面的拉应力。而当玻璃瓶受急冷作用时，外表面的拉应力远大于内壁向的压应力。若急冷或急热作用所产生的最大应力值超过玻璃的抗拉或抗压强度，则导致玻璃瓶壁破裂，这种破裂现象称为热冲击破裂。热冲击破裂通常发生在玻璃瓶身与瓶底过渡下部的外表面。因此，要求对玻璃瓶进行耐热冲击强度测试。
图4-10玻璃瓶在急热急冷时应力分布
(2)测试方法
耐热冲击试验装置如图4-11所示，它主要由冷水槽、温水槽、试验笼、计时器等组成。试验原理是利用自动温度控制器把两个水槽的温度按预定温差调节好，把试样瓶放入热水槽中数分钟，然后连同瓶内的热水急速投入冷水槽中浸泡片刻取出，记录由于急剧温度变化而破裂的瓶数。
试样瓶是没有经过其他试验使用的玻璃瓶罐，并预先在一定的温度、湿度条件的实验室内放置30min以上。冷热槽内盛水量按试样瓶的质量计算，每千克玻璃的用水量不少于10L。槽内水温应均匀，温差不大于±1℃。
按照国家标准GB 4547“玻璃瓶罐耐热急变试验方法”进行试验。耐热冲击试验分为合格性试验、递增性试验和破坏性试验。
①合格性试验
Generally, the temperature of the cold Water Tank is adjusted to (25±1) °C, and the temperature of the hot Water Tank is the temperature of the cold Water Tank plus the specified test temperature difference. If the temperature of the cold Water Tank is not 25°C, the original test temperature difference can be reduced (or increased) by 0.5°C for every increase (or decrease) of 5°C. The specific test method is: firstly, the test bottles are separated and put into the basket upright to ensure that the sample bottles cannot collide with each other. Then immerse the basket with the sample bottle in the hot Water Tank. After the sample bottle is filled with hot water, the water level on the tank surface should be more than 5cm higher than the bottle mouth. Place the sample bottle in the hot Water Tank for no less than 5 minutes, then transfer the mesh basket together with the sample bottle filled with hot water into the cold Water Tank within (10 ± 1)s, and soak for 30s. Take out the sample bottles and check them one by one. The test results are expressed by the test temperature, the number of cracks and the percentage of cracks.
② Incremental test
Gradually increase the tested temperature difference with a constant temperature difference (such as 5°C) each time, until the rupture percentage of the sample bottle reaches the predetermined value. The test results are expressed in terms of temperature difference, number of cracks and percentage of cracks for each test.
③Destructive test
Gradually increase the test temperature difference until all sample vials are broken. The test results are expressed as the average temperature difference when all sample vials are broken.
