Why material comes before shape
The prettiest bottle is useless if it cracks under a pump, hazes over in the sun, or lets your fragrance evaporate. Before we talk shape, colour or decoration, we pin down the resin — because it decides what your bottle can safely hold, how it looks, and what it costs.
At Shijin we run four families of resin day in, day out: PET, HDPE, PP and PETG. Each has a personality. Here is how we choose.
PET — the clarity champion
PET (polyethylene terephthalate) is the go-to for anything that needs to look premium on a shelf. It offers glass-like transparency up to ~95%, high gas-barrier performance, good pressure resistance and excellent water resistance — ideal for toners, sprays, serums and lotions.
Its limits matter too: PET is not heat-resistant and should not carry strong acids, strong alkalis or aggressively corrosive contents. If your product is hot-filled or chemically harsh, PET is the wrong call.
Quick tell: a PET base has a small round injection dot in the centre. PET and PETG can be made crystal-clear and glossy; PE and PP top out at semi-transparent frosted or matte.
HDPE — the workhorse for harsh formulas
HDPE (high-density polyethylene) is built for chemistry. It resists strong acids, strong alkalis and corrosion, which makes it the default for many cleaning and industrial formulas.
The trade-offs: only average heat resistance, and a slightly porous wall structure that means it should not hold highly volatile contents for long shelf lives. HDPE also can’t be made glass-clear — expect natural, solid, pearlescent or frosted finishes.
PP — heat, impact and the closure king
PP (polypropylene) resists heat, impact and a wide pH range, which is why almost every cap, pump, sprayer and flip-top we make is PP. As a bottle body it’s tough and versatile; like HDPE it has a slightly porous wall, so it’s not first choice for volatile formulas.
PETG — the premium clear upgrade
PETG keeps PET’s high clarity but adds better chemical and acid/alkali resistance, giving a glass-like feel that suits high-end serums and essences. The catch is price: PETG costs more than PET, so we recommend it where the brand experience justifies it.
And what about recycled content?
For brands with sustainability targets, PCR (post-consumer recycled PET) is increasingly requested by European and North-American buyers. We cover PCR and our GRS certification in a dedicated article — see below.