The selection of plastics to be utilized in the products depends upon the melting, yellowing and Strength of the plastic. To engineer this plastic in protype and production one should know the suitability of the plastic towards the environmental factors and the long lasting of the plastic towards crazing.
It may be considered that plastics that withstand without losing their ability to flow when heated are considered as thermoplastics can be melted again and again to shape multiple production parts. The other can be heated and destroyed. ABS (acrylonitrile butadiene styrene) is consistent thermoplastic with good resistant properties than PP (Poly Propylene). With the ability to withstand higher temperature ABS is good and Polypropylene can withstand high moisture effects.
The contact with machines especially in CNC materials, injection molded parts, additive manufacturing of both the polymers, 3D printing of products and thermally graded machining materials of polymers both are considered good in comparison to other plastics like PE, PET, and PVC that are soft. The structural difference of ABS and PP co-relates the Strength of these two plastics as ABS formed by combining multiple polymer units by emulsion polymerization while the later PP is prepared by addition polymerization having long chains of same units.Â
Why polymers Crack? How the crack propagates in ABS and PP?
Crack initiation and propagation in polymer starts from the surface. The surface of ABS is rough to smooth. The internal stress when a machine operation is performed comes from different angles and orientations. This creates filamentary cracks, whitening and crazing on the surface which extends inside the polymer.
When the force is applied on the ABS plastic during cutting in CNC Machining process the three chains (acrylonitrile butadiene styrene) behave differently under same force as due to molecular nature is different. The creates a buckling phenomenon that is common in ABS due to these stresses.
Besides this, the PP surface is smooth. The chances to travel the crack from the surface to inside of the polymer is less because of same type of chains in every layer of the polymer. There is no bucking in the polypropylene products. Because of this reason most household items are usually made up of polypropylene insulation of wires, automobile parts, food containers and benches.
What makes cracking delay and increase the strength of polymers?
When considering the flexural Strength of ABS polymers as it is required in most design applications. It is greater than the tensile Strength. Because it is usually required in the load bearing applications. During cyclic loading it can withstand a higher rate than any other polymer due to its multiple chains which behave differently under same loads. In sunlight, and ultraviolent light it becomes brittle when exposed continuously for long periods of time. When designing a part these factors should be considered must.
The Strength can be increased by adding additives, reinforcements, carbon black particles and blending with another polymer. It ultimately depends upon the application where ABS is utilized. The creep resistance of PP is higher as it can be stable at high temperature applications. Working with impact forces during service life can absorb more energy and impact. Loading creates the structure distorted and chemically weak. The water absorption of PP is less which makes it suitable for underwater applications.
Effect of Machining and Cutting processes on polymers?
Due to their unmatched properties, the production of bio composites in various industries is increasing day by day. The light weight, easy accessibility, and biodegradability of traditional fiber composite materials add to the expense of a wide range of uses of these materials for the development of aircraft, ships, structures, extensions, and transportation.
These cellulosic fibers in their natural state, as well as various cellulosic waste products such as hulls, wood, and pulp, have been used as reinforcing agents in various thermoset and thermoplastic resins such as PVC, PP, ABS, nylon, epoxy resins, polyester resins, and polyurethane. The properties are achieved through the toughness of the rubber, with fine particles of elastomer being dispersed throughout the rigid matrix. These bio polymers are simple and give fantastic Mechanical properties.
How do prototyping and 3D printing of polymers work?
The Prototyping of materials nowadays requires 3D printing techniques. To 3D print a material it requires polymer and there are number of polymers depending upon their cost which Mechanical engineers are using for 3D printing techniques. The printer manufacturer 3D Stratasys, the original holder of the patent for this technology, markets machines specially designed for the 3D printing of high-performance plastics such as ABS, PP and PE.
These engineering plastics have high heat resistance and impact resistance. The Prototyping and test samples can also be prepared by PP but due to semicrystalline nature of PP it is responsible for its warpage/buckling. This impacts the Mechanical behavior of this olefinic material produced in large volume globally. The reverse technique of 3D printing is CNC Machining of polymers that remove the layer by layer of the polymer to design it in many forms for aesthetic appearance and for engineering applications.
If an architect and engineer 3D print a design, it can 3D cut a design from the actual polymer. Another application of both the polymers is to coat the melt at high temperature ~300℃. This protects the metal from corrosion. To design a metal protection in automobile a thin sheet of PP on newly fabricated parts coated to avoid it from dust particles and external contact until it handed over to the consumer. ABS brake system is installed in the automobiles as the resistance without heating is for these polymers.
Conclusion
In this technical and economical international article, a survey concerning the structural durability of plastics specifically ABS and PP. The literature survey regarding the considered materials will be presented by focusing on the influence of the 3D-printing process parameters on their Mechanical, impact, Ultraviolet and fatigue properties. Finally, a comparison between the two plastic materials ABS and PP was found.