Studies on α to β phase transformations in mechanically deformed PVDF films

PVDF cast films were drawn at different temperatures to different draw ratios at constant draw rate to understand the mechanism of α to β phase transformation during mechanical deformation. WAXD and FTIR studies were carried out to determine the formation and content of β phase in the drawn films. Lower stretch temperatures gave higher fractions of β phase. The cast PVDF films were also drawn at suitable temperatures below the PVDF ambient melting point to the draw ratio of 6.4. The highest fraction of β phase obtained in these ultra drawn films was 0.98. SALS studies carried out for films at different stretch ratios show the change in spherulitic structure with the stretching parameters and give information for the understanding of phase transformation during stretching of PVDF films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Sequence distribution and crystal structure of poly(ethylene/trimethylene terephthalate) copolyesters

The sequence distribution and the crystal structure of copolyesters synthesized from ethylene glycol, 1,3-propanediol, and dimethyl terephthalate with different molar volume ratios were investigated in this study. The triad sequence probabilities of ethylene/trimethylene terephthalate were characterized from the aromatic quaternary carbons by ¹³C NMR. The composition of the copolyesters was determined from the aromatic quaternary carbons by ¹³C NMR, and the methylene protons by ¹H NMR. Results show that 1,3-propanediol reacted faster with terephthalic acid in copolyester polymerization than ethylene glycol. The difference in monomer reactivity is significant in the polymerization. Although the constitutional units revealed a random distribution in the molecular chain by ¹³C NMR, crystallites formed across the full range of ethylene glycol/1,3-propanediol composition by use of differential scanning calorimetry, a hot stage polarizing microscope, and a wide angle X-ray diffraction method. The WAXD deconvolution results show that the major constitutional repeating unit in the molecular chain dominates the crystal structure as a host crystal. The crystal structure was examined by a scanning electron microscope after a solvent etching. Photomicrographs show that the random distribution of the third constitutional unit in the molecular chain of copolyester significantly disturbs the host crystal formation and lamellar orientation.     

高密度聚乙烯在应力作用下结构研究

本文使用广角Ｘ射线衍射仪（ＷＡＸＤ）研究了高密度聚乙烯（ＨＤＰＥ）在应力作用下晶体结构变化。使用多峰分离程序（ＭＰＳ）对样品的Ｘ射线衍射（ＸＲＤ）谱图进行后续数字化处理,通过ＭＰＳ处理后的谱图可以将力化学加工过程出现的单斜相与原有的正交相和非晶相彼此重叠的ＸＲＤ谱图完全分离,计算了三相的相对含量以及结晶度和各相的微晶尺寸。结果表明,随力化学加工过程的进行,由正交相和非晶相构成的ＨＤＰＥ将出现第三相—单斜相,单斜相含量逐渐增加,而正交相含量逐渐减小,结晶度出现一个极小值。正交相和单斜相微晶尺寸出现规律性变化。     

Crystallization behavior of biodegradable amphiphilic poly(ethylene glycol)‐poly(L‐lactide) block copolymers

Poly(ethylene glycol)‐poly(L ‐lactide) diblock and triblock copolymers were prepared by ring‐opening polymerization of L ‐lactide with poly(ethylene glycol) methyl ether or with poly(ethylene glycol) in the presence of stannous octoate. Molecular weight, thermal properties, and crystalline structure of block copolymers were analyzed by ¹H‐NMR, FTIR, GPC, DSC, and wide‐angle X‐ray diffraction (WAXD). The composition of the block copolymer was found to be comparable to those of the reactants. Each block of the PEG–PLLA copolymer was phase separated at room temperature, as determined by DSC and WAXD. For the asymmetric block copolymers, the crystallization of one block influenced much the crystalline structure of the other block that was chemically connected to it. Time‐resolved WAXD analyses also showed the crystallization of the PLLA block became retarded due to the presence of the PEG block. According to the biodegradability test using the activated sludge, PEG–PLLA block copolymer degraded much faster than PLLA homopolymers of the same molecular weight. © 1999 John Wiley amp; Sons, Inc. J Appl Polym Sci 72: 341–348, 1999     

热定型条件对涤纶短纤维结构性能的影响

应用WAXD、密度、双折射法考察了仪化HV452涤纶短纤维生产线的热定型工艺及工艺参数变化对纤维结构的影响，并对其力学性能进行了讨论。结果表明，因拉伸应变结晶与热结晶的共同作用，在DF－3中第二辊处结晶就已基本完成，而后发生的“结构重整”过程是一个纤维丝束逐渐回缩、拉伸应力逐渐减弱的热力学平衡过程，使纤维结晶稳定，晶粒完善。此外，DF－3、HR的蒸汽压力不宜过高，应适当控制纤维在后加工过程中的热结晶。     

Miscibility of Crystalline/Amorphous/Crystalline Biopolymer Blends from PLLA/PDLLA/PHB with Additives

Miscibility of three biopolymers (PLLA, PDLLA and PHB) blends were investigated by POM, WAXD, FTIR, and DSC. DSC verified the thermal properties of biopolymer blend with PVAc as a compatibilizer, and TBC as plasticizer. Some change in glass transition temperature (T_g) of biopolymer blends from 60°C to 0.7°C. The spherulitic morphology of blend 9 changing by addition more PHB (50%), the results dendritic spherulites. The adding PHB to PLLA blends make certain shifting in the diffraction peak from 2 ? = 16.9° to 2 ? = 16.6° and the carbonyl group shifts from 1752 cm^?1 to 1732 cm^?1 in blends, demonstrating polar interactions between them.     

间苯二甲酸对嵌段共聚酯结构和性能的影响

本文通过Ｘ光衍射，ＤＳＣ，ＳＡＸＳ等方法，考察了间苯二甲酸的含量对聚对苯二甲酸乙二醇－聚己二酸乙二醇多嵌段共聚酯结构和性能的影响，发现合成时间苯二甲酸的加入，使共聚酯的Ｗａ，ｘ，Ｔｍ，Ｌｎｋｌ均下降，同时，力学性能也下降，但间苯二甲酸含量为１０％的共聚酯的力学性能最佳。     

HDPE／EVA共混体系的研究

采用ＤＳＣ，ＷＡＸＤ和力学性能测试，研究了ＨＤＰＥ／ＥＶＡ共混体系。结果表明，ＨＤＰＥ／ＥＶＡ共混体系是不相容的，但在共混组成中含有少量（＜１０％）的ＥＶＡ，力学性能下降很少，而加工性能得到改善，具有一定实用价值。     

聚醚酮酮及其低聚物晶体的晶型结构

利用ＷＡＸＤ研究ＰＥＫＫ的晶型，得到两种晶型，其点阵常数为：Ⅰ型ａ＝０．７７５ ｂ＝０．６０９，ｃ＝１．０１及Ⅱ型ａ＝０．４１８，ｂ＝１．１３，ｃ＝１．００７；表明多晶型不仅与结晶条件也与分子结构有关。     

Investigation on Brill transition of nylons 6/16, 4/16 and 2/16 by variable‐temperature WAXD and FTIR

Brill transition behaviour of nylons 6/16, 4/16 and 2/16 has been studied systematically by variable‐temperature wide‐angle X‐ray diffraction (WAXD) and real‐time FTIR. It is shown that all nylons investigated undergo Brill transitions before melting on heating. Brill temperatures detected by real‐time FTIR are consistent with the results of variable‐temperature WAXD measurements. In addition, Brill bands were identified based on real‐time IR spectra and further consideration of —NH— groups provided additional information for discussing the mechanism of the crystalline transition. Copyright © 2003 Society of Chemical Industry