Grafting of vinyl acetate onto poly(vinyl chloride) in solution

Radiation-induced grafting of vinyl acetate (VAc) onto poly(vinyl chloride) (PVC) was performed in solution with dimethylformamide (DMF). Grafting was studied as a function of dose, dose rate, and VAc/PVC ratio. The amount of grafting was measured by IR spectroscopy on the graft copolymer fraction insoluble in hot methanol. The homopolymerization of VAc was also studied in the same conditions, in order to check the influence of the solvent on radiochemical reactions leading to graft copolymers. The results show that the grafting can be easily obtained and the graft copolymer will be tested for the preparation of ultrafiltration membranes.     

Gamma radiation induced graft copolymerization of acrylamide onto poly(vinyl chloride) films

Grafting of acrylamide (AAm) onto poly(vinyl chloride) (PVC) films using gamma radiation has been carried out. The effects of different parameters on the graft yield have been investigated. These parameters include radiation dose, monomer concentration, solvent composition, types of inhibitors and acidity of the medium. In addition, the effects of the multifunctional monomers N,N′-methylene allyl amide (MAAm) and 2,4,6-triallyloxy-1,3,5 triazine (TARA) on the graft yield have been investigated. It has been found that methanol/water mixture in the ratio (1:1) is the proper diluent mixture for enhancing the graft copolymerization process. The presence of sulphuric acid in the reaction medium adversely affects the graft yield more than acetic acid. The presence of MAAm in the reaction medium markedly increases the graft yield, while TARA has practically no effect on the grafting process. Grafted films have been characterized and evidence of grafting has been obtained using thermal and spectroscopic analysis together with swelling measurements in water. © 1998 SCI.     

Poly (vinyl chloride) processing morphology

This paper describes how morphology of PVC changes in the Brabender mixing head. At the range of temperatures used for PVC processing, the Brabender torque-time curve shows minimum torque and maximum torque. The minimum torque is associated with a breakdown of 150 μm PVC grains and 10 μm agglomerates resulting in the release of the 1μm primary particles. The torque increases from minimal interaction between primary particles to the point where primary particles agglomerate at maximum torque so that fibriles can be formed when PVC samples are swollen in acetone and sheard. Further heating reduces the viscosity resulting in lower torque even though residual primary particles still exist with much particle to particle interaction. Primary particle structure disappears at about 215° C with complete melting.     

紫外光辐照对硬质聚氯乙烯结构及性能的影响

采用衰减全反射傅立叶变换红外光谱、紫外光谱、扫描电镜、凝胶渗透色谱、拉伸应力一应变、黄色指数、与水接触角及失重率等测试研究了紫外光(UV)辐照对硬质聚氯乙烯(PVC)结构及性能的影响。结果表明:随着UV辐照时间的延长,平均相对分子质量增大至最大值后,进一步延长辐照时间平均相对分子质量减小,多分散系数由1.771增加到1.919,相对分子质量分布变宽。分子链中引人了多种揣基官能团和多种共扼多烯结构。试样表面经历了粗糙、裂纹形成及其扩散等形态破坏过程,试样黄色指数由40.7%逐渐增加到90%以上,表面颜色逐渐变深,失重率逐渐增大到0.22%,与水接触角先由63.3迅速下降到55,然后下降程度趋于平缓,逐渐下降到平衡值50UV辐照的初期试样的拉伸强度由未经辐照时的55MPa增加到57MPa,进一步延长辐照时间后拉伸强度降低,而断裂伸长率由未辐照时的35.5%迅速降低到11.8%。     

给水管用PVC的改性研究

采用活性碳酸钙和甲基丙烯酸甲酯-丁二烯-苯乙烯三元接枝共聚物(MBS)对PVC进行改性,研究了二者对改性PVC抗冲击性能的影响.结果表明,活性碳酸钙和MBS的加入,改性PVC的抗冲击性能可提高17.3％,改性PVC管在低温下的抗冲击性能得到明显提高.     

马来酸酐接枝改性氯化聚氯乙烯的制备及其在PVC中的应用

采用固相法制备马来酸酐接枝氯化聚氯乙烯(CPVC-g-MAH),得到了接枝率达2.91 %的CPVC-g-MAH,并对其进行了性能测试,探讨了聚氯乙烯(PVC)/CPVC-g-MAH共混物的冲击性能和加工性能,与PVC/氯化聚氯乙烯(CPVC)共混物进行对比以观察改性效果。结果表明,CPVC-g-MAH的热性能较CPVC有较大提高;PVC/CPVC-g-MAH共混物的冲击性能比PVC/CPVC共混物有所提高,而平衡转矩有所降低,说明CPVC-g-MAH相比于CPVC对PVC共混物加工性能改善效果更加明显。     

Radiation crosslinking of poly(vinyl chloride)

The mechanism of the electron irradiation crosslinking of poly(vinyl chloride) (PVC) with polyfunctional acrylic monomers has been investigated as part of a program to develop an insulation for distributing-frame wire. These monomers were found to undergo rapid polymerization to form a rigid, three-dimensional network onto which PVC was grafted. Polyfunctionality was necessary for crosslinking to occur, since butyl methacrylate, containing only a single unsaturated bond, did not crosslink readily. On the other hand, trimethylolpropane triacrylate and trimethylolpropane trimethacrylate, each containing three unsaturated groups, gave extremely rapid crosslinking. Trimethylolpropane triacrylate showed 40 times the radiation sensitivity of tetraethylene glycol dimethacrylate, a diunsaturated compound. The rate of disappearance of unsaturation was related inversely to the rate of gel formation. This was attributed to immobilization of unreacted pendant double bonds in the rigid crosslinked network. In the triunsaturated monomers, half the vinyl groups were left unreacted when all of the PVC was insoluble.     

聚羟基烷酸酯改性聚氯乙烯的研究

通过熔融共混的方法分别制备了聚氯乙烯/邻苯二甲酸二辛酯/聚羟基烷酸酯（PVC/DOP/PHA）和PVC/PHA共混物。研究了PHA逐步代替DOP对共混物力学性能和熔体流动性能的影响规律,利用扫描电子显微镜对所制备的试样进行微观结构分析。结果表明,随着共混体系中PHA用量的增加和DOP的等量减少,与PVC/DOP共混物相比,PVC/DOP/PHA共混物的拉伸强度由21 MPa提高至42 MPa,断裂伸长率先增加而后降低,在PHA含量为10.7 %(质量分数,下同)时出现极大值(350 %);在PVC/PHA体系中,PHA含量增加,PVC/PHA共混物的力学性能及熔体流动速率都显著提高,说明PHA可以作为PVC的一种有效的绿色增塑剂和增韧剂。     

硅烷交联聚氯乙烯的研究

研究了硅烷的种类,增塑剂,交联时间等因素对PVC交联的影响,结果表明,通过调节硅烷的用量可以制备不同交联度的PVC,交联后的PVC其力学性能,尺寸稳定性,体积电阻率,热主为形温度得到提高。     

抗静电软质聚氯乙烯材料的研究

采用表面电阻测试和扫描电镜，分析研究了软质聚氯乙烯(PVC)树脂与炭黑(CB)复合体系的抗静电性与炭黑含量、分布形态、PVC树脂型号及混炼塑化工艺之间的关系。结果表明：在炭黑临界添加量18％时，较短的混炼时问内，不同型号的PVC树脂基体中均能形成导电网络，体系的导电性能迅速提高，可达到抗静电的目的。相同混合和成型条件下，与SG-3树脂相比，炭黑在相对分子质量较大的SG-2基体树脂中更易形成均匀分布形态，破坏导电网络，导致电性能随混炼时间迅速下降。力学性能测试表明：炭黑的加入使复合体系的拉伸强度和断裂伸长率降低。     

Poly(vinyl chloride) and its fire properties

This work provides an up‐to‐date review of the fire properties of poly(vinyl chloride) (PVC) materials, both rigid (unplasticized) and flexible (plasticized). The fire properties addressed include ignitability, ease of extinction (oxygen index), flame spread (small scale and intermediate scale), heat release, smoke obscuration, smoke toxicity, hydrogen chloride emission and decay, and performance in real‐scale fires. This comprehensive review includes a wide selection of references and tables illustrating the properties of PVC materials in comparison with those of other polymeric materials, including, in many instances, wood materials. The work puts these fire properties in perspective, showing that the heat release rate (the key fire property) of rigid PVC (and that of properly flame‐retarded flexible PVC) are among the lower values found for combustible materials. This work also shows that the smoke toxicity and smoke obscuration resulting from burning PVC materials in real‐scale fires is in the same range as those of other materials.     

改性碳酸钙用于聚氯乙烯的研究

研究了一种改性碳酸钙的性质及其在聚氯乙烯中的应用情况。研究结果表明,这种改性碳酸钙与普通碳酸钙相比,具有吸油值低、堆积密度大、分散性好、热稳定性高等特点。填充于聚氯乙烯中,不仅能改善物料的加工性能及制品的物理力学性能,而且还具有较高的热稳定性能。     

乙烯—醋酸乙烯酯共聚物的化学接枝改性

综述了乙烯－醋酸乙烯酯共聚物的化学接枝方法,重点探讨了乙烯－醋酸乙烯酯与马来酸酐的接枝原因,并对接枝物的表征及应用加以论述。     

Radiation protection of poly(vinyl chloride) by N-methyl dithiocarbamate substitution

The effect of N-methyl dithiocarbamate substitution on the radiation stability of poly-(vinyl chloride) (PVC) films was studied. PVC containing between 2 and 11 mole-% N-methyl dithiocarbamate (PMD) was irradiated with γ-rays from a ⁶⁰Co source at 40°C and the evolved gaseous products were measured and analyzed with a mass spectrometer. The apparent G values for gas evolution for PMD decreased remarkably. For example, a G value of 0.28 was obtained for a PMD which contains 11 mole-% dithiocarbamate group compared with a G value of 10.8 for unmodified poly(vinyl chloride). Furthermore, the mass spectrum of the evolved gas from the same PMD sample (PMD-44) with 10 Mrad irradiation showed no hydrogen chloride to be present. The external protection was studied using polymer-blended films of PVC and PMD-44. The stabilization coefficients for internal protection and external protection in polymer blends were calculated. The ESR spectrum of the irradiated PMD-44 showed a strong anisotropy with high g values which differed significantly from the spectrum of the irradiated PVC. A suggested mechanism for radiation protection of PVC against γ-rays irradiation by the N-methyl dithiocarbamate group is discussed.     

聚氯乙烯泡沫人造革的发泡问题

论述了聚氯乙烯（PVC）人造革的发泡机理,分析了离型纸工艺和压延工艺中的对发泡有影响的因素,提出了生产中需要控制的要点。     

聚氯乙烯结皮发泡棒材生产技术

较详细地讨论了单螺杆挤出机生产聚氯乙烯结皮发泡棒材的有关技术问题,包括挤出机和模具的结构参数、最佳配方设计和关键工艺条件控制,认为采用长径比大于２５的普通单螺杆挤出机,在合理配方和工艺条件下,可生产高质量聚氯乙烯结皮发泡棒材,φ１０￣３８ｍｍ的棒材的生产可采用φ６５ｍｍ螺杆的挤出机。     

The Initial Thermal Stability of Poly(vinyl chloride)

The use of a fluidised bed reactor and a conductivity cell provide a technique for the study of degradation of PVC with greatly increased sensitivity. The kinetics of the reaction may be studied at 350 K and for small (1%) amounts of degradation. The effects of diffusion within the particles may be distinguished from that of diffusion in the surrounding atmosphere. The influence of temperature and particle size and sintering were examined. The catalytic effect of HCl was confirmed and an apparent activation energy of 29 kcal mol^?1 was observed.     

硅灰石填充改性硬质聚氯乙烯的研究

考察了两种硅灰石刚性粒子填充硬聚氯乙烯的力学性能。结果表明，在一定的填充量范围内，两种硅灰石都能提高PVC的冲击强度，硅灰石粒子表面包覆了聚甲基丙烯酸甲酯改性处理后，对基体树脂的力学性能改善明显，尤其是小粒径的改性硅灰石刚性粒子改进更大。另外，还结合电子显微镜观察对共混体系的增韧机理进行了讨论。     

PVC/EVA共混物的研究

本文研究了混炼温度和时间对PVC/EVA共混物抗冲性能的影响,发现加入聚乙烯,共混体系的抗冲击强度能进一步提高.用TEM观察了PVC/EVA的形态结构,采用Brabender塑化仪和毛细管流变仪研究了共混物的塑化和熔体流变行为.通过计算机对实验结果进行二元线性回归,建立了共混物的熔体粘度与剪切应力和温度相关联的数学模型.