Plastic Wash and Care Packaging Blow Molding: Not all materials are "blown once" the number of times depends on the process and demand

Plastic Wash and Care Packaging Blow Molding: Not all materials are "blown once" the number of times depends on the process and demand

Different types of plastic wash and care packaging materials require different numbers of blow molding times, which mainly depends on the type of blow molding used, rather than the material itself. For a professional plastic bottle supplier, accurately matching the process with the material is key to ensuring the quality of the packaging.

Currently, mainstream processes are "single blow molding" and "double blow molding": the former is suitable for materials such as HDPE, which can efficiently complete one-piece molding is ideal for wash and care products with high sealing requirements; the latter is the standard for PET materials, allowing for more complex bottle shape designs through two-step molding, meeting aesthetic needs. The two processes have significant differences in molding logic and application scenarios, and the plastic bottle supplier will choose the appropriate process scheme based on the product characteristics and needs of customer.

1. One-time blow molding: suitable for HDPE, PP, "one-step" molding

One-time blow molding ( known as extrusion blow molding, EBM) integrates the melting, molding, and blow molding of plastic into one process. It only blows once throughout the process, for materials that do not require stretching reinforcement, such as HDPE and PP. It is common in frosted wash and care bottles and large-capacity hair conditioner bottles.

core process is as follows:

1. Plastic pellets (such as HDPE) are heated and melted by an extruder and continuously extruded into a tubular "";

2. The parison is sent into the mold for closure before it cools, and high-pressure air is blown into it from the inside to make theison adhere to the inner wall of the mold;

3. After cooling and setting, the mold is opened to directly obtain the finished bottle body, with only one blow m action throughout the process.

The key advantage of this method is its simple process and low cost, and it can also adapt to the characteristics of poor fluidity and high crystall of HDPE - no additional stretching is required, and one blow molding can meet the strength requirements of opaque wash and care packaging materials.

2. Two-time blowolding: exclusive for PET, "first make the blank and then blow the bottle"

Two-time blow molding (also known as stretch blow molding, ISBM is the only choice for PET materials to make transparent wash and care bottles. It needs to be completed in two steps, including "one-time injection molding to make the blank and "two-time blow molding to form", essentially achieving molecular arrangement optimization through two processes to meet the requirements of high transparency and impact resistance.

Its core process as follows:

1. First processing (injection molding to make the blank): PET pellets are melted and injected into the mold to make an "tube-shaped preform (not a finished product), which is taken out after cooling;

2. Second processing (blow molding to form): the preform is reheated to stretchable state, first stretched longitudinally by a stretching rod, and then injected with high-pressure air to blow (the second time), so that the preform ad to the mold to form, and finally a transparent bottle body is obtained.

PET must use two-time blow molding because its molecular structure needs to be "longitud transversely" stretched in order to become compact. If it is blown once like HDPE, the bottle body will be turbid and prone to cracking, and it will not the quality requirements of transparent packaging materials for shampoo and essence liquid.

3. Special cases: the superposition effect of blow molding times and material, demand

In addition the mainstream processes, some special needs will make the number of blow molding times and material produce more flexible combinations:

Multi-layer co-extrusion blow molding: such as "PET EVOH" multi-layer wash and care bottles (for highconcentration essence), although based on PET, it is necessary to extrude the multi-layer plastic into a composite tube billet through a co-extruder first, then blow mold it once, which still belongs to "one-time blow molding", but it adds an initial composite process. This type of high-sealing bottle is popular with plastic empty bottles wholesale buyers, especially suitable for high-end wash and care products.

Small PP travel bottles: some thin-walled PP small bottles will adoptone-time injection blow molding" (integrating injection and blow molding in the same equipment), although the process is smooth, it still belongs to one-time blowolding, which is different from the secondary processing of PET. This kind of efficient small-capacity bottle type is often used for wholesale lotion bottles with pump travel sets, meeting the of consumers for portable use.

The core influencing factor of blow molding times is "process type", and the process type is determined jointly by material characteristics (such as PET needs stretching HDPE does not need stretching) and product needs (such as transparent vs opaque, high strength vs ordinary strength). It is not possible to simply divide by material, but to "material characteristics   packaging function requirements" to determine its blow molding times.