According to pvc plastic mesh news, many friends plasticizing industry, often can see my colleagues around how to test the PVC pipe is good or bad quarrel on this issue, and some say that cracking is a good product, there are That is not broken is good, and some say light pressure or impact is one-sided, in fact, we all have their own understanding, but the toughness of plastics and rigidity is a relative concept.
In mechanics, there are two physical quantities of stiffness and flexibility. 'Stiffness' mainly refers to the size of the force required to deform an object. 'Flexibility' mainly refers to the deformation of an object under unit force. It can be seen that the more rigid the object, the less prone to deformation (in the performance of the elongation is small); the more flexible the greater the deformation of the object (in the larger elongation).
A more ideal assumption is that the stiffness of an object approaches infinity (or the deformation of an object is negligible to a negligible degree), which we call a rigid body, so we can not consider its own deformation in mechanical analysis. Rigidity is a property that reflects the ease of deformation of an object.
Toughness of the material is relatively soft, the physical properties of the tensile elongation at break, the impact strength larger; hardness, tensile strength and tensile modulus of elasticity is relatively small, while rigid materials, its hardness, tensile strength larger; Elongation at break and impact strength may be lower; Tensile modulus of elasticity is greater. Flexural strength Reactive material stiffness, bending strength is large, the rigidity of the material is large, otherwise the toughness in the ASTM D790 bending performance standard test According to the method, these test methods are suitable for rigid materials as well as for semi-rigid materials and have not been said to be suitable for ductile materials, so a highly ductile elastomer will not test flexural strength.
Stiffness and brittleness are generally linked together.Fragile refers to the material when the external force reaches a certain limit, the material without a premonition of sudden destruction, and no obvious plastic deformation damage the brittle material mechanical properties characterized by much greater compressive strength Tensile strength, minimum ultimate strain at break, are brittle materials, such as bricks, stone, ceramics, glass, concrete, cast iron, etc. They are considerably more detrimental to impact resistance and vibration than toughened materials.
As engineering plastics, we hope it has both good toughness and rigidity.In improving the toughness of the material, we should also try to improve the rigidity.Generally adding the elastomer can increase the toughness, adding the inorganic filler can increase the rigidity.The most effective method is to change the elasticity Body toughening and filler enhancement combined with poor impact resistance is the performance of some important industrial plastics defects such as PVC, PS, PP, especially at low temperatures because of the impact resistance is too low and its application is limited .
In thermoplastics, their impact resistance can be greatly enhanced by the addition of 'impact modifiers', and there are many types of impact modifiers commonly used, including ACR-Acrylates, MBS-Methyl Methacrylate - butadiene-styrene copolymer, CPE-chlorinated polyethylene, abs, EVA, EPT-EPDM and so on.
From the pvc plastic modification effect point of view, ACR is a better overall characteristics, MBS is an important impact modifier transparent products, but also in the global impact modifier market occupies a very important position.
Although the impact modifier can improve the impact strength of the product, it has a bad effect on other mechanical strength, such as MBS added to PVC will make him the tensile strength and bending strength decreased.ACR addition, will make HPVC - The tensile strength, hardness and vicat heat resistance of high molecular weight PVC have been reduced.With the addition of CPE, the tensile strength, flexural strength and Vicat softening point of the blends also decrease.Therefore, , You must take into account the other performance, must be considered and assessed to determine a more appropriate dosage.