Types of Plastic Materials

The most used plastic materias in sprayers and bottles inlcude PP, LDPE, HDPE, PET. Some customer also use POM but XJT doesn’t use this material. Sometimes PS or ABS will be used to make the dust cap or overcap.

Heat Deformation. Scientific analysis is based on Heat Deflection Temperature (HDT). Below is the data of HDT at 0.46 MPa in the sort of low to high. LDPE 40°C to 50°C; HDPE 60°C to 90°C; PET 75°C to 115°C; PP 100°C ot 120°C; POM 160°C to 170°C. However, the life experience is quite different. When we put these materials into the boilling water for only a few seconds, LDPE, HDPE, PP, POM don’t deform any, but PET deform/shrink largely. In the life experience, PET bottles start to deform once the temperature is above 60°C. The low deformation temperature limits PET can not be sterilized by heat. And PET should be more careful during shipment. BTW, the difference between scientific experimental results and life experience may be because the experimental test methods don’t exclude the effect from materials’ natural rigidness.

Chemical Resistance. All materials POM, PET, PP, HDPE, LDPE have good chemcial resistance, which can meet the requirements of normal pharmaceutical liquid. POM and PET’s chemical resistance is relatively a little weak so PP, HDPE and LDPE are used more often in pharmaceutical liquid containers. Moreover, POM has itself limiation in plastic injection. Will discuss in another section.

Color. Natural colors of HDPE (semi-transparent), LDPE (close to transparent), PP (close to transparent), PET (clear or fully transparent), and POM (white) are shown in the brackets. In real application, colorant especially white colorant is added during plastic injection or blowing, so some components and bottles can be colorful. The point necessary to be noted is only PET bottle can be the clear and amber colors like glass. This is one reason some medicine producers like using PET bottle.

Toughness. Toughness and Rigidness are different. Toughness means the material will not crack after heavy bending. Toughness decreases from PP, HDPE/LDPE, PET, POM. Especially PP has a very good toughness.

Rigidness. Rigidness decreases from POM, PET, PP, HDPE, LDPE. At room temperautre, all these materials can keep the shape unchanged. POM is very rigid and it is called as “iron” in plastic materials.

Elasticity. The elasticity of all of POM, PP, HDPE, LDPE and PET is not good. These materials’ shape can recover after slight deformation. However, heavy deformation will be permanent.

Poriness. This is not important in pharmaceutical packaging. This character is mainly discussed for bottles. The wall of HDPE bottle has many tiny pores allowing single molecule to penetrate. PP and LDPE bottles are better. PET bottle’s poriness is lowest but isn’t still higher than glass bottle. POM is not used to make bottle but POM material’s poriness is also very low. Poriness leads to the fragnance reduce during long time storage. This is why perfume need use glass bottle instead of plastic bottle. Pharmaceutical bottles don’t contain fragnance or similar, so poriness is not considered normally.

Summary, to be applied in pharmaceutical liquid packaging, PP, HDPE, LDPE is best. PET is also good but need be more careful. POM is possible but has more limitation.