Plastic bottles are made from a wide range of different plastic packaging materials. Each polymer is unique and has individual value propositions that may work best for your application. Some plastics have a better oxygen barrier, some work better for extreme heat and extreme cold, and some are more squeezable than others. Each bottle will be unique, as will each closure or dispensing solution, so you must be sure to request samples of the components to test with your fill.
HDPE (High Density Polyethylene)
High Density Polyethylene, frequently referred to as HDPE, is a more dense PE plastic that is frequently extrusion blow molded into bottles. HDPE is heavier and stronger than PE or LDPE; it is also less squeezable. This plastic is frequently used for milk jugs, beverages, and personal care products. HDPE is resistant to chemicals, so you will frequently see bottles for cleaning solutions, like wipes and sprays, made from this material. Natural HDPE is not fully transparent like PET, it is a little cloudy. HDPE is the #2 recycled plastic material in the United States.
PET (Polyethylene Terephthalate)
Polyethylene Terephthalate, or PET, is the most commonly used polymer for bottles. PET is the most recycled plastic resin in the United States. PET’s chemical structure allows thinner walled, rigid containers to maintain good strength, making the plastic a good solution for packaging. PET also has high clarity, allowing for easy color matches or clear formula visibility. If your formula requires UV protection, you will want to use an opaque or amber colored bottle. PET is a hygroscopic material, meaning the resin attracts and absorbs water, so it must be dried before it can be melted and molded.
Polypropylene, or PP, has a high temperature tolerance and excellent oxygen barrier properties (the oxygen barrier is why PP is typically used for airless bottles). PP resin has higher clarity than PE, but lower clarity than PET. Polypropylene bottles are recyclable in the United States, though not as much polypropylene is recycled as PE and PET. However, polypropylene production has a lower environmental impact and produces fewer emissions than both PE and PET, so it is still a sustainable choice. Polypropylene is used for products that are sensitive to oxygen, like luxury skincare or nutraceutical supplements. Other applications include long shelf life formulations, like art supplies or medical products (PP resists chemical leaching), and food or beverage as polypropylene can be frozen or microwaved.
LDPE (Low-Density Polyethylene)
Low-Density Polyethylene, or LDPE, is a less dense PE, known for it’s squeezability when it is extruded into bottles or tubes. LDPE bottles are frequently paired with dispensing closures, like snap top caps, dropper tips, and orifice reducers, allowing product to be squeezed out. Natural LDPE has similar transparency to HDPE, but it is more translucent. LDPE is very recyclable.
Less Common for Good Reason (PVC, PS)
PVC (Polyvinyl Chloride) and PS (Polystyrene) are less frequently used for bottles now due to a demonstrated higher environmental impact. PVC and PS are both very difficult to recycle, and take very long to degrade due to their excellent durability and strong polymer chains. PVC is particularly harmful to PET’s recycling stream, as the high clarity materials look very similar to vision sorting systems at recycling facilities. Since the melt temperatures for PVC are much lower than the melt temperatures for PET, the PVC will contaminate the PET being recycled and harm the processing equipment. Manufacturing PVC also releases harmful chemicals into the environment. You may still see PVC bottles used for hot fill applications, and PS used for disposable bottles.
Ultimately, the choice of plastic will depend upon many factors including appearance, functionality, manufacturing location, and environmental impact. COMPAX is dedicated to satisfying each requirement for your brand.