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For the toughening technology of modified plastics, it is enough to read this article

Time : 2023-06-19 Hits : 3

Modified plastics  are becoming more and more prevalent in modern society, particularly in the industries of autos and household appliances. Since the application of goods frequently depends on the toughness of materials, plastic toughening technology has received study and attention from both academic and industry circles for many types of modified plastic technologies. I will address the following queries concerning plastic toughening in this article:

1. How can the durability of plastics be tested and assessed?

2. What is the plastic toughening principle?

3. What types of toughening chemicals are frequently employed?

4. How can plastics be made more durable?

5. How do I comprehend that capacity must be increased prior to toughening?

Plastic toughness as characterized by performance

 —Greater rigidity reduces the likelihood of material deformation, while greater toughness increases the likelihood of deformation

big. Impact strength, which commonly refers to the energy absorbed by the spline before it breaks, is the ability of the spline or workpiece to survive the impact. Impact strength cannot be categorized as a fundamental attribute of the material since it varies based on the spline's form, the testing procedure, and the state of the test sample. Results from various impact test methodologies cannot be compared.

Impact tests can be done in a variety of ways. There are three different types of impact tests: normal temperature impact, low temperature impact, and high temperature impact; bending impact-charpy and cantilever beam impact, tensile impact, torsional impact, and shear impact; and high-energy one-time impact and small-energy multiple impact tests, depending on the energy and number of impacts used. Different impact test techniques can be chosen for various materials or applications, yielding a variety of findings that cannot be compared.

Mechanisms and influencing factors for plastic toughening

1. The craze-shear band theory

The two major functions of rubber particles in the mixing system of rubber toughened plastics are:

On the one hand, it causes many crazes and shear bands in the matrix as the site of concentrated stress;

On the other side, crazes can be prevented from becoming destructive fractures by limiting their ability to spread.

Shear bands may be induced by the stress field toward the conclusion of the frenzy to bring it to a halt. Additionally, it stops crazes from growing when they enter the shear zone. Energy is used during the formation and growth of many crazes and shear bands when the material is stressed, which increases the material's toughness. Shear banding is associated with the formation of narrow necks, whereas craze shows macroscopically as a stress whitening event. These two phenomena have distinct behaviors in various plastic substrates.

For instance, toughened PVC has a high matrix toughness, and the yield is mostly brought on by shear bands. HIPS matrix, on the other hand, has a low matrix toughness, craze, stress whitening, and craze volume rises, and the transverse dimension essentially remains unaltered. There are thin necks but no stress whitening; a significant percentage is taken up by HIPS/PPO, silver streaks, and shear bands; thin necks and stress whitening happen together.

(2) The toughening effect of plastics is primarily influenced by three variables.

1. Matrix resin characteristics

According to studies, increasing the toughness of the matrix resin will increase the toughening effect of plastics that have been hardened. The matrix resin's toughness may be increased in the following ways:

Narrow the molecular weight distribution by increasing the matrix resin's molecular weight and increase toughness by regulating crystallinity, degree of crystallization, crystal size, and crystal shape. For instance, adding a nucleating agent to polypropylene (PP) speeds up crystallization and refines the grain structure, increasing the material's fracture toughness.

2. Toughening agent dose and characteristics

A. The impact of the toughening agent's dispersed phase's particle size—The qualities of the matrix resin and the ideal value of the particle size of the elastomer's dispersion phase are different for elastomer-toughened plastics. For instance, the ideal rubber particle size in HIPS is between 0.8 and 1.3 m, the ideal ABS particle size is around 0.3 m, and the ideal PVC-modified ABS particle size is roughly 0.1 m.

B. The impact of the quantity of toughening agent applied; the particle distance parameter is connected to the ideal amount of toughening agent added;

C. The impact of the toughening agent's glass transition temperature: the stronger the toughening effect, the lower the glass transition temperature of general elastomers;

D. How the toughening agent affects the matrix resin's interface strength—how the interface bond strength affects the toughening effect varies depending on the system;

E. The impact of the elastomer toughener's structure, which is influenced by the kind of elastomer, level of crosslinking, etc.

3. The force that binds the two phases together

The macroscopically higher overall performance of the plastic is mostly due to the gain in impact strength, but a good bonding force between the two phases can also make it possible for stress to be successfully conveyed between the phases while using more energy. This binding force is typically thought of as the interaction between two phases. Block and graft copolymerization are frequent techniques for enhancing the bonding force between two phases. The distinction is that they create chemical linkages using techniques like grafting and block copolymerization. Block copolymer SBS, polyurethane, ABS, and branch copolymer HIPS.

It falls under the category of physical blending for polymers that have been hardened, but the basic idea is the same. The two components should be somewhat compatible and create their own phases in the ideal blending mechanism. Between the stages is an interface layer. The two polymers' molecular chains diffuse with one another in the interface layer, and the gradient in concentration is clear. As the mixing is intensified The components' compatibility results in a strong binding force, which subsequently improves diffusion to scatter the interface and thicken the interface layer. The crucial technology for creating polymer alloys at this point is polymer compatibility technology, which also includes plastic toughening!

What do tougheners for plastic do? How do you split?

How to separate the common toughening agents for plastics

1. Rubber elastomer toughening: EPR, EPDM, butadiene, natural, isobutylene, nitrile, etc.; suitable for toughening modification of used plastic resins;

2. TPE toughening: SBS, SEBS, POE, TPO, TPV, etc.; mostly used to toughen polyolefins or non-polar resins, as well as to toughen polymers with polar functional groups like polyesters and polyamides. Whenever compatibilizer is added;

3. Core-shell copolymers and reactive terpolymers are used to toughen engineering plastics and high-temperature polymer alloys, such as ACR (acrylates), MBS (methyl acrylate-butadiene-styrene copolymer), PTW (ethylene-butyl acrylate-methyl glycidyl acrylate copolymer), and E-MA-GMA (ethylene-methyl acrylate-glycidyl me

4. Blending and toughening of high-toughness engineering plastics, such as PP/PA, PP/ABS, PA/ABS, HIPS/PPO, PPS/PA, PC/ABS, PC/PBT, etc.; polymer alloy technology is essential for this process;

5. Toughening via other techniques, such as using sarin resin (a DuPont metal ionomer) or nanoparticles (such as nano-CaCO3);

The toughening of modified polymers can be broadly categorized into the following circumstances in real industrial production:

1. To fulfill the demands of usage, the hardness of synthetic resin must be increased; examples include GPPS, homopolymer PP, etc.;

2. Significantly increase the toughness of polymers, such as nylon that is extremely strong, to satisfy the demands of extreme toughness and prolonged usage in low-temperature situations;

3. The performance of the material is decreased after resin modification, such as filling and flame retardant. Effective toughening needs to be done right now.

Free radical addition polymerization is typically used to produce general-purpose polymers. Polar groups are absent from the molecule's side chains and main chain. Engineering plastics can be toughened by adding rubber and elastomer particles for a greater toughening effect. Typically, condensation polymerization is used to create it. Polar groups are found in the side chain or terminal group of the molecular chain. It can be made tougher by using functionalized rubber or elastomer particles.

Different Toughener Types for Frequently Used Resins

What do you think, pros? Increasing capacity is the secret to toughening plastic.

In general, when exposed to external forces, plastics absorb and release energy via the processes of interface debonding, cavitation, and matrix shear yielding. Elastomers with high compatibility, with the exception of non-polar polymeric resins, can be applied directly. To achieve the goal of final toughening when utilizing particles (same compatibility principle), other polar resins must be successfully compatibilized. The graft copolymers indicated above will interact strongly with the matrix when utilized as tougheners, including:

(1) The addition reaction between the epoxy functional group and the polymer's terminal hydroxyl, carboxyl, or amine group takes place after the ring is opened.

(2) Core-shell toughening mechanism: the rubber has a toughening effect while the outside functional group is completely compatible with the components;

(3) Ionomer toughening mechanism: The physical crosslinking network is created when metal ions and carboxylate groups of polymer chains complex, toughening the material.

In reality, this compatibilization approach may be applied to all polymer blends if the toughener is thought of as a class of polymers. Reactive compatibilization is a technology we must employ when creating beneficial polymer blends for industry, as illustrated in the table below. The term "toughening agent" now refers to a different thing, such as a "interface toughening compatibilizer" The word "emulsifier" is quite descriptive!

In conclusion, plastic toughening is equally significant for crystalline and amorphous plastics, and general-purpose, engineering, and special engineering plastics are all improving their heat resistance while also becoming more expensive. The demands for heat resistance, age resistance, etc. are stronger, and it is also a major test for plastic modification and toughening technology. However, maintaining excellent compatibility with the matrix and components is the most crucial and vital factor!


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