The complete evolution history of PVC processing aids you must know!

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1. History of the PVC industry PVC is a thermoplastic polymer material that was synthesized as early as 1838. However, this material degrades under the influence of light and heat, and its processing temperature is close to its decomposition temperature; for a long time, it was considered to be a useless material. It was not until 1912 that the first patent for a rubber material based on PVC appeared, sparking scientists’ interest in researching the applications of PVC materials and thus marking the beginning of PVC’s development. Important events in the PVC industry are shown in Table 1. Table 1. Milestone Events in the PVC Industry
Time | Event
1838 | PVC polymer was first synthesized.
1872 | After years of development, an industrial synthesis method was established.
1912 | First patent for a rubber material based on PVC.
1927 | PVC became commercially viable and began to be marketed.
1931 | Plasticizers started to be produced on an industrial scale.
1933 | First patent related to the use of plasticizers to soften PVC materials.
1936 | Sales of PVC materials reached 1 million pounds.
1953 | First patent for PVC processing aids.
1957 | Acrylic-based processing aids began to be produced industrially.
1958 | PVC impact modifiers started to be manufactured on a large scale.
1961 | PVC sheets, films, and pipes began to appear.
1963 | PVC materials entered the home improvement sector.
1964 | PVC bottle products were introduced.
1970 | Rigid foamed PVC materials were developed.

2. The history of PVC processing aids
Due to the unique structure of PVC materials, it is difficult to plasticize them; moreover, they have issues such as low melt strength and poor melt ductility. These problems significantly affect the molding and processing of PVC materials, and efforts have been ongoing to find solutions to these issues. Initially, scientists tried to address these issues by reducing the molecular weight of PVC, using low-molecular-weight plasticizers, or employing copolymers of synthetic PVC with other materials. However, this often came at the expense of the material’s physical properties, making such approaches unsuitable. The first patent on a PVC processing aid in the true sense appeared in 1953; this processing aid was a copolymer of styrene and acrylonitrile. Five years later, processing aids based on methacrylates and styrene were developed. During this period, many companies conducted research on PVC processing aids, and a number of polymers were reported to be suitable as such aids. These include: · Methyl methacrylate/styrene copolymer · Acrylate/methyl methacrylate/N-vinyl lactam tercopolymer · Methyl methacrylate/methyl glycidate copolymer · Methyl methacrylate/isobutyrenic acid isobutyl ester copolymer · Methyl methacrylate/acrylonitrile/alkyl acrylate tercopolymer · Methyl methacrylate/alkyl acrylate core-shell structured copolymer · PVC/methyl methacrylate/alkyl acrylate graft copolymers · Styrene/acrylonitrile copolymer · α-**ethylene/acrylonitrile/styrene copolymer · Organic polysiloxanes · Low-molecular-weight polystyrene · Styrene/acrylonitrile/butyl acrylamide copolymer · Ethylene/vinyl acetate/chlorine dioxide tercopolymer · Polypropylene/acrylic acid graft copolymers. For various reasons, most of the above products were not put into industrial production; only a few have been manufactured and utilized on a large scale. A representative example is the acrylate processing aid with a core-shell structure. Foreign companies such as Rohm and Haas, ICI, AkzoNobel, Chugai Chemical, and LG have become manufacturers and suppliers of PVC processing aids. 3. The role of ACR-type processing aids: The effect of ACR-type processing aids on PVC can be regarded as that of a blend with PVC as the main component and the processing aid as a secondary component. A small amount of such processing aid can significantly improve the melting process of PVC, without affecting the material’s final physical properties. The formulations of PVC products include various components such as fillers, pigments, and impact modifiers. The role of PVC processing aids in these formulations can be summarized in three main aspects: facilitating the plasticization process of PVC resin ； Improving the rheological properties of PVC melt ； Improve the surface quality of PVC. ① Improving the plasticization of PVC resin: The difficulty in plasticizing PVC is due to its unique structure, and ACR processing aids can significantly enhance the plasticization rate of PVC. Generally, the effect of ACR processing aids on plasticization properties can be tested using a torque rheometer. Under normal circumstances, in formulations with processing aids added, both the minimum torque and the plasticization torque increase to varying degrees, while the plasticization time decreases. It should be noted that the plasticization time and plasticization torque are related to the molecular weight of ACR. ACR with a low molecular weight only reduces the plasticization time, but has little effect on the melt torque. For ACR processing aids with the same composition, the lower the molecular weight, the faster the plastic is plasticized; conversely, the higher the molecular weight, the longer the plasticization time. ② The improvement in the rheology of PVC melt by ACR: Poor processing properties of PVC are not only manifested by its difficulty in being plasticized, but also by low melt strength, poor melt ductility, and melt fracture that occurs during the processing process. ACR-type processing aids can serve a dual purpose: on one hand, they improve the plasticizing properties of PVC, and on the other hand, they enhance the rheology of the melt. Among them, the rheology of the melt can be evaluated using laboratory-scale testing methods such as extruders, Haake rheometers, and twin-roll mills. There are many factors that affect the demolding expansion rate of polymer materials, including the molecular weight of the polymer, the composition of the formulation, as well as processing conditions such as temperature, pressure, shear rate, and mold length. For PVC blow molding and film blowing products, controlling the film separation expansion rate is particularly important; in addition, the extrusion and injection molding industries generally require a lower film separation expansion rate. ACR-type processing aids affect the film separation expansion rate during PVC processing; therefore, the major manufacturers and product grades are necessary. The melt strength of PVC actually reflects the elasticity and tensile viscosity of the PVC melt; generally, high requirements are placed on melt strength in the fields of PVC blow molding and film production. In these application areas, the PVC melt tends to sag due to the effect of gravity. Due to the increase in the strength of the PVC melt, the resulting mold release expansion and ductility can counteract the effect of gravity-induced sagging, thereby eliminating the problem of uneven thickness. However, it is important to address the conflict between melt strength and the rate of mold release expansion, which needs to be determined through factors such as formulation and experimentation. Melt ductility is important in various application areas such as thermoforming, extrusion foaming, and blow molding. During the molding process, polymer materials are subjected to high levels of compression and stretching; if the melt lacks ductility, melt fracture can occur. Therefore, polymer materials need to possess a certain degree of melt ductility. Under higher stretching conditions, melt fracture does not occur; generally, the higher the molecular weight of ACR, the better it is at improving the ductility of the melt. The melt viscosity of PVC is related to the molecular weight of ACR; most common ACRs increase the melt viscosity of PVC, while ACRs with low molecular weights have little effect on the melt viscosity of PVC. In the field of injection molding, adding ACR often requires an increase in the minimum film filling pressure, which is an adverse effect; however, it can improve the \"jetting\" phenomenon and enhance the appearance of the products. Low-molecular-weight ACR has little effect on the die-pushing pressure during injection molding, but it provides virtually no improvement on the \"jetting\" phenomenon. 4. New PVC processing aids: Although ACR-type processing aids have been around for decades and their products continue to be improved, research and development of new PVC processing aids never stops. For example, DuPont’s Elvaloy serves as both a processing aid and an impact modifier in rigid PVC; the available grades include Elvaloy®HP4051, Elvaloy®HP441, Elvaloy®HP661, Elvaloy®PTW, Elvaloy®4170, Elvaloy®4924, and others. In addition, Cray Valley, a subsidiary of French company Total, has also developed a non-acrylate-based PVC processing aid that can effectively improve the processing properties of PVC and enhance its thermal stability; the product grades are Cleartack® W110 and Cleartack® W140. Domestically, the molding agents Eaform®WY-66 and Eaform®WY-68 developed by Jiangsu Aitern High-Performance Materials Co., Ltd. are also new types of PVC processing aids that significantly improve the performance of PVC during molding and processing in applications such as extrusion.