Polyethylene Vs Polypropylene: Which Is Better?


Polyethylene and polypropylene are two of the most commonly used plastics in the world. Both of them being polymers, they share a lot of similarities, and it can be hard to find the differences between the two. But they do have a lot of characteristics that are unique to each other, and knowing them will make it easier for you to choose which one to use, depending on your needs.
 
Polyethylene
 
Polyethylene is known for its lightweightness, excellent durability and affordability. It is commonly used for manufacturing stock poly bags, zip lock bags and bottles. The most commonly used polyethylene plastics are High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), and Linear Low Density Polyethylene(LLDPE) 
 
HDPE is defined by a density of greater or equal to 0.941 g/cm3. HDPE has a low degree of branching and thus low intermolecular forces and tensile strength. HDPE can be produced by chromium/silica catalysts, Ziegler-Natta catalysts or metallocene catalysts. The lack of branching is ensured by an appropriate choice of catalyst (for example, chromium catalysts or Ziegler-Natta catalysts) and reaction conditions. HDPE can withstand temperatures of up to 120 °C, and is resistant to a lot of solvents. It is also opaque, which is great for storing items that are sensitive to light exposure. Examples of HDPE items include milk jugs, detergent bottles, butter tubs, garbage containers,  water pipes, pre-taped masking film
 
LDPE is defined by a density range of 0.910–0.940 g/cm3. LDPE has a high degree of short and long chain branching, which means that the chains do not pack into the crystal structure as well. It has, therefore, less strong intermolecular forces as the instantaneous-dipole induced-dipole attraction is less. This results in a lower tensile strength and increased ductility. LDPE is created by free radical polymerization. The high degree of branching with long chains gives molten LDPE unique and desirable flow properties. LDPE is used for both rigid containers and plastic film applications. such as greenhouse film, plastic builders film, plastic drop cloth, plastic furniture bag, timber wrap and etc.  
 
LLDPE is a substantially linear polymer (polyethylene), with significant numbers of short branches, commonly made by copolymerization of ethylene with longer-chain olefins. LLDPE differs structurally from conventional LDPE, because of the absence of long chain branching. The linearity of LLDPE results from the different manufacturing processes of LLDPE and LDPE. In general, LLDPE is produced at lower temperatures and pressures by copolymerization of ethylene and such higher alpha-olefins as butene, hexene, or octene. The copolymerization process produces a LLDPE polymer that has a narrower molecular weight distribution than conventional LDPE and in combination with the linear structure, significantly different rheological properties.  The LLDPE is mainly used for agricultural ground film, stretch film, 
 
Polypropylene
 
Polypropylene has a lot of similarities with polyethylene in that it can be designed to be durable and lightweight. Aside from these, polypropylene has excellent mechanical properties and high resistance to fatigue, impact, heat and freezing. It is highly resistant to corrosion and chemical leaching, making it ideal for storing solvents, bases and acids.
 
Polypropylene is the second most commonly used plastic after polyethylene. It is used in many applications similar to polyethylene such as bottles and gloves. Unlike the latter, though, it has a crystal-clear transparency. It is also pure and non-stretching, unlike polyethylene.
 
Which should you use?
 
There are a lot of similarities between polyethylene and polypropylene, but they also have characteristics that are unique to each other, which can be maximised depending on how they are made and the applications they are used for.
 
Tapes.
 
Polyethylene tapes have excellent resistance against tear and abrasion. They can adhere really well on many surfaces, and they have great low temperature bond. They are also highly conformable, which makes them usable in a wide range of sealing applications. Polypropylene tapes can have the same tensile strength and damage resistance as polyethylene tapes, the only difference being that they are more affordable than the latter. The downside, however, is that they can be noisy to use.
 
Bags
 
Both of these polymers are commonly made into stock poly bags. Polyethylene bags are semi-transparent, which is great for limiting light entry when storing items that are sensitive to light. They have low static charge, ideal for electronic components, and has higher resistance to rips and tears compared to polypropylene.
 
Polypropylene bags have crystal clear transparency, which is great if you want to store items in way that all details are shown. Polypropylene can also prevent evaporation and exposure of items to bacteria, so you can use them for storing, for example, medical equipment.
 
Gloves
 
Polyethylene gloves are cheaper than their polypropylene counterparts. They also typically come powder and latex-free, which is why they are highly used in applications that involve food. They don’t trigger allergic reactions, so they are safe to use.
 
Although more expensive than polyethylene gloves, most polypropylene gloves are durable, which means they can be reused a number of times before they’re needed to be discarded. Polypropylene gloves can have moisture-wicking properties, and they can be worn as liners for warmth.
 
 
For all your plastic product supply needs, check out the KF PLASTICS catalogue! We provide plastic drop cloth, plastic builders film, pre-taped masking film, plastic furniture bag and other packaging and storage products made of high quality polyethylene, Visit the KF PLASTICS website to learn more about our products. Don’t forget to read our other blogs for more tips on item packaging.  

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