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Briefly about PCO28 Tamper-Evident Plastic Cap- By continuous compression moulding and plastic cap injection molding
Dec 24, 2018

  Briefly about PCO28 Tamper-Evident Plastic Cap- 

         By continuous compression moulding and plastic cap injection molding 

With the continuous improvement of peoples living standard, a wide variety of beverage are available:In supermarket,store,mart,we can see a range of drinks, which plastic an essential role in peoples colorful life.

While we enjoy the happiness of all kinds of beverage,do we pay attention to the top of beverage? Thats  plastic bottle cap. 

Even though bottle cap is a small item,and significant for laymen,it play an important part for each beverage.  

 cap compression molding machine

As far as people in plastic cap field are concerned,each small cap paid much effort. A premium plastic bottle cap,should not only assure good sealing, but also combine light-weighting, even more excellent in appearance and hand feeling, meanwhile, have to be suitable for large batch.

Thus,a superior bottle cap, in the process of research,pilot test,volume production and commissioning,must go through plenty of change,and finally launch in the market.

We hereby introduce the structure of PCO28 Plastic cap, to build a concept for friends and peers are entering plastic cap field. 

For the foresighted entrepreneurs invested in plastic bottle cap production and staff in the field, this would enhance the comprehension to bottle caps.

The Carbonated soft drink we see in the market, like Coco Cola, Pepsi Cola, Sprite,7-Up, Fanta and some sparkling beverage, mostly use PCO28 Cap (1881 and 1810 cap). PCO28 possess the function of light weighting, excellent sealing, stability,etc.

A bottle cap, undertake the mission of sealing, the target is isolating beverage inside and outside surroundings, reducing the risk of pollution, releasing the dispersion of internal air.


As we can see, there are two sealing rings inside plastic cap,Part A is Internal plug, Part B is External plug, through the extrusion of between neck-finishes and Internal plug and External plug. General speaking, Internal plug contribute 70% to sealing effect,External Plug provides 30% of sealing function.  

 cap compression molding machine

Chinese leading premium Cap compression molding machine factory. (

As for PCO28 plastic cap, the pressure it undertakes is bigger than others. To ensure maximum sealing effect, design a Reinforcing Rib of External plug outside wall,to avoid the break under extrusion between neck-finishes and External plug after filing. There are plenty of PCO28 Plastic cap without Reinforcing Rib, a quality accident by CSD leaking occurs in domestic beverage brand before, the reason is Out plug break leading to air leakage, and heavy damage as well as loss.

Since the high pressure inside Carbonated Soft Drink,when consumers open beverage,if caps open too fast,it would cause the extremely high pressure by CO2 quick dispersion in short time.

It reported that some similar event happened before, the result of this accident is consumers would take enterprises to the court, which is the phenomenon any water beverage manufacturers wont like to see. In terms of this issue, in the thread of bottle cap,usually design two symmetric bulges, that would have resistance during cap open. After muti-tests and market verification, it proves that in the premise of meeting the industrial standard, this design reduces the cap elastic accident harm nearly to 0%.

Water cap, it means theres no air in the water,or the air pressure is quite little.Cap elastic accident wont happen even though open caps quickly.

From the view of lightweight, height of neck finishes and bottle cap are designed as short neck, caps is easy to open.Thus,cap is designed with three short screws, and open easily after twisting off 1/3 circle of bottle cap. 

Since CSD cap is under high pressure, if the design is same as water cap,which is easily to open, cap elastic accident would occur with strong air jet. In order to avoid this issue, 1881 plastic cap thread need to design as an integrated and long one, consumers have to twist off nearly two circles,then caps can open. In this process,CO2 has been dispersion. 

 cap compression molding machine

Chinese leading premium Cap compression molding machine factory. (

Simply speaking,the answer is that: when cap opens,the place of thread off is a gap, this would make CO2 easy to spill out, thats to cut down the cap elastic risk. Meanwhile,thread break would save resin and cost,besides, its more easy to clean bottle neck finishes in filling.    

With the rise of raw material,lightweight is the tendency of packaging industry, 1881 cap is not an exception, strong enterprise would consider lightweight caps to cut down production cost.

To promise the quality of essential parts like cap top thickness and Internal Plug and External plug,by reducing the thickness of other non-key parts, such as optimizing the thread off length and deepness, plastic cap wall thickness, as well as Tamper Evident Band thickness,so that decrease the cap weight.

Some friends would find PCO28 caps contain Injection molding and Continuous Compression moulding.At present,1881 and 1810 caps made by cap compression molding machine are the mainstream, of course there are numerous PCO28 caps are by cap Injection molding,and plastic cap injection molding production has been tended to shrinkage trend. For example,a worldwide famous cap manufacturers closed its 1881 plastic cap injection molding production line in May,2014, and engaged in continuous compression moulding after that.We dont discuss the comparison between facility and cap molds cost and energy consumption temporarily,actually,average cap cost of compression molding is lower than injection molding, we hereby compare PCO28 appearance at first:On the top of Injection molding cap, there is a embossing point-thats injection gate. 

Dont ignore this small point,it brings too much inconvenient factors in plastic cap production.  

 cap compression molding machine

Generally speaking, CSD caps normally need printing logo and pattern on the top. This small point would affect printing,the weak adhesive function always lead to incomplete and flaky pattern. Caps made by cap compression molding machine, cap top is smooth and suitable for various of patterns. Injection gate is easy to get jam in production, there is some unmelted matter(like iron wire and nylon string etc.) exist in injection gate and cause jam, then results in thin top and seal plug starving, thus, lead to weak seal function after filling.This issue always causes product recall in the future,which is a deadly attack to water/beverage brand, plastic caps manufacturers are unable to undertake such big loss and compensation. In continuous compression moulding, this troublesome doesnt exist. 

Another important function is anti thief, thats the irreversible proof after cap open. This function replies on Tamper Evident band to realize. There are plenty of structure in the market,in which, continuous folding structure provides Max force to Tamper Evident Band, making it locking much tighter between Tamper Evident band and bottle neck,that would solve the problem of cap body and Tamper Evident Band conjoint after cap open,which usually interrupts numerous beverage enterprises. 

 cap compression molding machine

 cap compression molding machine