Process and material considerations in the industrial application of lubricants in rigid PVC extrusion

The proper lubrication of rigid PVC compounds often plays an important role in the successful operation of a rigid PVC extrusion plant. Changes in a particular lubricant system can have a substantial effect on the fusion rates of a rigid PVC compound and on the thermodynamics of the fusion process. Recently published research on the morphology of PVC resin and rigid PVC finished products has provided new insights into the morphological changes rigid PVC undergoes during processing. Lubricants can have a substantial impact on the rates and extent of morphological changes of rigid PVC during processing. Successful industrial optimization of a lubricant system involves balancing the rheological characteristics of the compound against the shearing and heating characteristics of the extruder and die tooling. Changes in the extruder and die tooling or lubricant system will result in changes in the work and energy balance. The impact of increases in fusion promoting lubricants, as well as increases in fusion delaying lubricants, on the work and energy balance for a twin screw extruder is explained.     

Laboratory evaluation of the processing characteristics of rigid PVC compounds

A small scale screw extruder designed for laboratory extrusion studies has been developed and its performance characteristics with powder-blended rigid PVC Compounds have been investigated. The use of the extruder in determining the susceptibility of rigid PVC compounds to various die-induced viscoelastic phenomena (fracture, sharkskin, and swell) is described. An investigation of the phenomenon of “nerve” in rigid PVC extrusions has been carried out. It is concluded that nerve is associated with instabilities in the fluxing process occurring in the transition section of the extruder screw design, the operating variables of the process, and the processing characteristics of the compound.     

Manufacture of rigid PVC/wood‐flour composite foams using moisture contained in wood as foaming agent

Relatioships between the density of foamed rigid PVC/wood‐flour composites and the moisture content of the wood flour, the chemical foaming agent (CFA) content, the content of all‐acrylic foam modifier, and the extruder die temperature were determined by using a response surface model based on a four‐factor central composite design. The experimental results indicated that there is no synergistic effect between teh CFA content and the moisture content of the wood flour. Wood flour moisture could be used effectively as foaming agent in the production of rigid PVC/wood‐flour composite foams. Foam density as low as 0.4 g/cm³ was produced without the use of chemical foaming agents. However, successful foaming of rigid PVC/wood‐flour composite with moisture contained in wood flour strongly depends upon the presence of all‐acrylic foam modifier in the formulation and the extrusion die temperature. The lowest densities were achieved when the all‐acrylic foam modifier concentration was between 7 phr and 10 phr and extruder die temperature was as low as 170°C.     

Gloss control in rigid PVC—Part II. Effect of processing variables on the gloss of rigid PVC profiles

This paper describes the results of a study of the effect of extrusion conditions on the gloss of rigid PVC profiles. Extrusion variables investigated are extrusion melt temperature, extruder temperature settings, extrusion rate, and the die/sizer metal surface condition. It is hoped that this information will help PVC profile manufacturers to optimize their process for achieving desirable gloss.     

钙/锌稳定剂对硬质PVC制品耐候性能的影响

介绍了影响PVC硬制品耐候性能的因素,研究了钙/锌稳定剂对PVC硬制品耐候性能的影响。     

Effect of processing parameters on fusion and mechanical properties of a twin‐screw extruded rigid PVC pipe

The effect of varying mass temperature and screw speed on the fusion level and mechanical properties of a rigid PVC pipe produced by a twin‐screw extruder has been investigated. Differential Scanning Calorimetry (DSC) and capillary rheometry have been used to determine pipe fusion levels. While yield stress was shown to be completely insensitive to fusion level, a very distinct maximum of falling weight and notched Charpy impact strengths and elongation at break was observed at moderate fusion level. Short‐term burst strength values increased with degree of fusion while hydrostatic internal pressure tests revealed optimum resistance for pipes of varying fusion level. The effect of processing temperature on fusion in the Brabender Plasticorder was also examined.     

Vinyl stabilizer efficiency as determined by iso-thermalgravimetric analysis

Iso-thermalgravimetric analysis has been used by many authors in studying the degradation mechanism of PVC. For the PVC compounder though this same method provides a reliable means of determining the efficiency and cost effectiveness of commercial PVC stabilizers. Thermal stability of PVC resins stabilized with organotin, antimony, and ester stabilizers are presented and compared with data obtained by conventional Brabender Plasticorder and post extrusion oven aging tests. In addition a method is presented to establish the relative stability and cost effectiveness of a stabilizer at given concentrations currently familiar to the rigid PVC compounder.     

N-substituted maleimides as thermal stabilizers for rigid polyvinylchloride

N-substituted maleimides have been investigated as thermal stabilizers for rigid polyvinylchloride (PVC) at 180°C in air by measuring the rate of dehydrochlorination and the extent of discoloration of the polymer. The results reveal the higher stabilizing efficiency of these products relative to basic lead carbonate, dibutyl tin maleate, and cadmium-barium stearate stabilizers commonly used in industry. The induction period (Ts) increases as a function of the positive resonance effect of the substituents (+R). Moreover, the investigated stabilizers impart better color stability for the degraded samples as compared with the stearate stabilizer. The stabilizer efficiencies are attributed to their radical trapping potency which intervenes with the radical degradation process of PVC, while the good color stability is due to the ability of the stabilizer to interact with the conjugated double bonds formed on the PVC chains as a result of degradation. A mechanism illustrating the stabilizer's action is proposed.     

硬质PVC发泡制品的配方设计

阐述了硬质PVC发泡制品配方中PVC树脂和热稳定剂、发泡剂、优泡剂、冲击改性剂、加工改性剂、填充剂、润滑剂及成核剂等助剂的选用原则,介绍了生产优质硬质PVC发泡制品的基础配方。     

肉豆蔻酸稀土复合热稳定剂对PVC性能的影响

合成了肉豆蔻酸镧、肉豆蔻酸铈、肉豆蔻酸钕三种稀土热稳定剂,采用刚果红法分别测试了其与硬脂酸锌、季戊四醇、硬脂酸钙之间的协同作用,复配得到了硬质PVC用新型肉豆蔻酸稀土复合热稳定剂。利用转矩流变仪、动态力学谱仪等考察其对PVC流变性能和力学性能的影响。研究结果表明：肉豆蔻酸稀土复合热稳定剂具有良好的热稳定性,静态和动态热稳定时间约为120min和60min,能较好地抑制PVC的初期着色性;复合稀土体系的加工流变性能优于铅盐体系;拉伸强度、断裂伸长率和断裂强度与铅盐体系相当,而冲击强度高于铅盐体系。     

硬质PVC用钙锌复合热稳定剂的研究

运用刚果红试纸法和热烘箱老化实验法，对硬质PVC（聚氯乙烯）用钙锌复合稳定剂的主要组分如硬脂酸钙、硬脂酸锌、多元醇、环氧大豆油、亚磷酸酯以及稳定性助剂等进行了考察，得到了各组分及各组分用量之间协同作用的关系，同时还得到了硬质PVC用钙锌复合热稳定剂的实用配方。     

Weatherable rigid PVC: The effect of light and thermal stabilizers

Rigid PVC compositions used in outdoor applications such as siding, profiles, windows, and soffit predominantly contain a tin mercaptide thermal stabilizer. It is well known that tin mercaptides impart outstanding thermal stability to vinyl compounds, however, it is also well known that they provide only marginal light stability. Mercaptides can be used in these applications primarily because they are combined with high levels of titanium dioxide. They are not well suited for dark colored PVC and compositions without titanium dioxide. These require a more weatherable thermal stabilizer, such as a tin carboxylate. In this paper, principles for formulating rigid weatherable vinyl will be discussed. The influence of thermal stabilizers and the interdependence of light stabilizers and thermal stabilizers on PVC photostability will be emphasized. Data will be presented showing how one can formulate weatherable dark brown and pastel PVC through the use of tin carboxylate thermal stabilizers, the appropriate light stabilizers, and pigments. Traditional approaches to achieving weatherability will be compared to what can be attained by capitalizing on the latest advances in stabilization technology. Finally, methods for reducing TiO₂ concentration will be shown.     

Antioxidants and UV stabilizers: A summary of their utilization in PVC

With the ever increasing demand for better performing products has come the enhanced use of stabilizers and stabilizer systems in both the production and processing of poly(vinylchloride). Antioxidants and chain terminators are commonly used in teh resin manufacturing to improve the initial color and overall quality of the polymer isolated from production. Hindered phenolics and organophosphites have been found to boost the performance of thermal stabilizers for PVC processing. Additionally, as both rigid and flexible PVC compounds have found greater and more demanding weatherable applications both indoors and outdoors, the utilization of UV stabilizers has grown proportionally. For most outdoor applications the UV stabilizer system is essential for the maintenance of color and mechanical properties of the PVC product. This paper attempts to review and discuss stabilizer usage for specific PVC formulations and applications and answer questions as to how and why they are used.     

Influence of additional thermal stabilizers on the reprocessing of postconsumer poly(vinyl chloride) bottles

The addition of heat stabilizers is essential for preventing the degradation of poly(vinyl chloride) (PVC) during its processing. The heat stabilizers consumed in the first run have to be made up before the reprocessing of recycled PVC. In this study, solvent‐cast films, which were prepared from granulated postconsumer PVC bottles mixed with plasticizers and thermal stabilizers, were used. The films were subjected to various heat treatments. No considerable structural change upon heat treatments at 140–160°C was found in IR and differential scanning calorimetry analyses. Polyene formation observed through ultraviolet analysis was not severe, indicating that the added stabilizers worked well in preventing degradation. The weight loss during the heat treatments was attributed partly to the decomposition of PVC and the evaporation of volatile components and mainly to the removal of the solvent upon heating. Although this study was conducted with water bottles that were to be recycled, it may be equally well applied to other similarly formulated PVC‐based materials, such as packaging films. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3994–3999, 2003     

In-depth rheological study of acrylic processing aids in rigid polyvinyl chloride applications

Acrylic processing aids are used widely in rigid polyvinyl chloride (PVC) applications. Key functions of processing aids in terms of processing and performance are discussed in the paper. Effect of molecular weight of acrylic processing aids on their functions are studied. Additionally, effect of processing conditions, such as temperature and shear on fusion characteristics of PVC formulations are investigated. Shear rate in the processing was varied by means of rotor speed in torque rheometer. Processing aids of comprehensive molecular weight range are evaluated in the study. It was observed that relatively lower molecular weight processing aids have different response to change in shear and temperature than higher molecular weight processing aids. Depending upon fusion conditions PVC formulations can yield either a single or double fusion peak. Generally, it was considered that ultra-high molecular weight processing aids yield a double fusion peak, however, it was demonstrated in the studies that it is not true. Fusion conditions, temperature, and shear are the main driving forces of fusion dynamics, resulting in either a single or double fusion peak. Relatively low molecular weight acrylic processing aids can also yield double fusion peak. Melt viscosity and shear thinning properties are also examined. Relatively lower molecular weight processing aids showed higher shear thinning behavior. Effect of temperature and shear on degree of fusion was studied. It was shown that optimum processing parameters can increase the degree of fusion by ~10%.     

耐热耐腐蚀硬质聚氯乙烯挤出板材塑料配方研究

介绍了应用新型耐热改性剂改性PVCS - 10 0 0树脂 ,研制耐热耐腐蚀硬质聚氯乙烯挤出板材配方的情况     

有机锡热稳定剂对TPU/PVC共混体系脱氯化氢的影响

主要研究了用刚果红法测有机锡热稳定剂对热塑性聚氨酯,聚氯乙烯共混物的脱氯化氢的影响。重点探索热塑性聚氨酯在不同有机锡稳定剂作用下对共混物脱氯化氢的影响,同时还比较了硫醇和非硫醇两大有机锡体系的稳定作用。此外,还探索了有机锡与金属皂稳定剂和环氧大豆油并用对共混物的作用。研究结果表明：在共混体系中,热塑性聚氨酯在聚氯乙烯脱氯化氢过程中不仅起简单的稀释作用,还能促进聚氯乙烯分解。热稳定剂有效地抑制共混物中聚氯乙烯脱氯化氢的速度,在所选的三种有机锡稳定剂当中,硫醇系要好于非硫醇系。以395A和T-137作用效果最好。DBTL和CaSt2、环氧大豆油复合,都具有协同作用。     

扭矩流变测定法研究硬质PVC/木粉熔融性能

研究了扭矩流变仪中木粉含量、木材种类(软木和硬木)及粒度对硬质PVC/木粉复合材料熔融性能(熔融时间、熔融温度、熔融扭矩和熔融能)的影响。纯硬质PVC只有1个熔融峰,而PVC母体材料中加入木粉后会产生2个熔融峰。结果表明,增加木粉含量会使基本粒子间开始熔融时间、温度和能量明显增加,从而引起熔融扭矩的增加,与木粉种类无关;用木粉填充的硬质PVC应该在比纯树脂高的温度下加工;木材种类会影响复合材料的熔融性能,但软木和硬木之间确定不出一个明显的趋势;精细粒子的熔融速度比粗粒子快,需要的能量也较少。     

An evaluation of the effects of antimony and tin stabilizer on the fusion characteristics of PVC dryblends

Although the classification of lubricants can be misleading, the classification of their actions is not only possible but very useful. By considering the basic actions which affect PVC dryblend fusion, a better understading of the characteristics and advantages of additives can be realized. The antimony and tin stabilizers used in this study have been characterized by the affects on PVC dryblend fusion. Production extrusion results confirm the laboratory classifications.     

PVC powder extrusion. Melting properties and particle morphology

The extrusion of unplasticized PVC powder has been studied. Powder blends with low amounts of lubricants have been used in order to observe differences between structurally different PVC powders. Experiments with varying screw speeds indicate that resins consisting of agglomerated, small, globular primary particles are more sensitive to shear and deformation in the extruder channel than more compact particles. Frictional heat seems to be dissipated inside loosely agglomerated resin particles, possibly because of a larger internal surface. This additional heat, which depends on the shear rate, influences the melting behavior considerably. Scanning electron microscopy shows that PVC particles seem to melt without first breaking into smaller particles. A comparison between bulk-polymerized and suspension-polymerized PVC with nearly the same particle structure reveals a close similrity in melting properties. The results obtained in this work indicate that structural differences may explain the differences in melting behavior often observed when rigid PVC blends are extruded.