In terms of storage conditions, after a lot of tests, it is almost not brittle under low humidity conditions, the properties of hollow capsules are still stable under high humidity conditions, and the various indicators of vegetable capsules under extreme storage conditions are not affected. Gelatin capsules are easy to stick under high humidity conditions, harden or brittle under low humidity conditions, and are highly dependent on the temperature, humidity, and packaging materials of the storage environment.

    Hypromellose is chemically stable and does not react chemically with air and water, and cellulose is metabolically inert, it is not absorbed in the body and is directly excreted. It is not easy to grow microorganisms, so under normal conditions, they will not decompose and deteriorate when placed for a long time.

    Gelatin is protein and has an electrostatic effect, while HPMC hollow capsule has little or no electrostatic effect. These are attributed to the different chemical compositions of the two, gelatin contains carboxyl and amino groups, while HPMC has a delayed disintegration phenomenon during placement. HPMC is part of methyl and part polyhydroxypropyl ether of cellulose, with stable chemical properties and no cross-linking, so it will not delay the disintegration of HPMC hollow capsules.

    Studies have shown that gelatin hollow capsules will become brittle when the water content is less than 10%, while HPMC hollow capsules will not become brittle even if the water content reaches 1%. Under the condition of 20～25C and RH40%～60%, the water content of the gelatin hollow capsule is about 13%～15%, and under this condition, the water content of HPMC hollow capsule is about 4%～6%. Excessive water content has a great influence on the stability of moisture-sensitive drugs.

    If gelatin hollow capsules are used for highly hygroscopic contents, water will be transferred from the gelatin hollow capsules to the content that migrates, the moisture of the hollow capsule decreases, and the hollow capsule becomes hard and brittle, resulting in delayed disintegration. However, there is no such phenomenon when HPMC hollow capsules are used for the contents with strong hygroscopicity.