Dissertation > Excellent graduate degree dissertation topics show

The Morphological Evolution of Polypropylene in the Stretching Field

Author: ZhangZhenFang
Tutor: ShenChangYu；ZhengGuoQiang
School: Zhengzhou University
Course: Materials Processing Engineering
Keywords: Extrude iPP Crystallization temperature Degree of orientation β-crystal
CLC: TQ325.14
Type: Master's thesis
Year: 2010
Downloads: 42
Quote: 0
Read: Download Dissertation

Abstract

Isotactic polypropylene (iPP) plastic with excellent performance in the production and processing has been widely used , however, there are some defects itself , such as the impact of poor performance and low heat distortion temperature , limit the use of iPP in some areas . Order to improve the performance of the use of the PP , to use various methods to produce a lot of the β crystal in order to improve the transparency of the material , the tensile strength, such as improving the toughness and ductility , it produces a high content of β crystal of the polypropylene scholars hot spots. Article will iPP and different proportions of β nucleating agent ( β - NA ) mixed sample and pure iPP feedstock , prepared a series of the sheet in a HAAKE extruder , while the screw speed is set to the minimum in order to reduce die at a shear stress. IPP film by a different tensile stress by changing the stretching rate ( SR ) , Further, in order to enable the β crystal was crystallized at a specific temperature range , we will die extruded film at directly through a constant temperature of 100 ° C and 120 ℃ the box stretching, to obtain high - temperature crystallization sheet. The use of a polarizing microscope (PLM), and wide angle X - ray diffraction (WAXD), differential scanning calorimeter (DSC) and other analytical instruments , research tensile stress , and crystallization temperature and a nucleating agent factors on the orientation of the iPP polymorph melting transition of . The paper draw the following conclusions : (1 ) various factors on the orientation of the iPP effects: stretching the higher the rate , the higher the degree of orientation of the sheet . The high temperature crystallinity degree of orientation of the sheet is slightly lower than the room temperature tensile degree of orientation of the sheet . (2) The influence of various factors on the β crystal of iPP generated : pure IPP sheet in the stretching action , there will be a small amount of the β crystal produced a lower tensile stress , and promote the growth of the β crystal , high tensile stress will inhibit the β crystal growth . The tensile stress of the overall trend of the formation of the β crystal in the plus β nucleating agent IPP samples are β -crystal content was gradually decreased with the increase of tensile rate . The high temperature thermostatic crystallization is conducive to the growth of the β crystal , so that the β-crystal content is much higher than under natural cooling at room temperature a sheet . (3 ) the impact of the iPP multiple melting behavior of the crystallization temperature : iPP sheets stretched under different conditions , in the DSC spectrum multiple endothermic peak , this regularity and crystallinity and the crystal structure of the degree of perfection .

Related Dissertations

CLC: > Industrial Technology > Chemical Industry > Synthetic resins and plastics industry > Polymer resin and plastic > Polyolefin plastic > Polypropylene
© 2012 www.DissertationTopic.Net Mobile