Chemistry Reference
In-Depth Information
necessary for it to have minimal content of diethylene glycol, carboxyl groups and high
molecular mass [249]. Synthesis of PETP on the basis of ethylene glycol and dimethyl
terephthalate may be intensified by introducing oligomers of polyethylene oxide with end
epoxy group [250] at the stage of interesterification and polycondensation.
Addition of low-molecular monoepoxides at the beginning and at the end of PETP
synthesis allows to increase PETP hydrolysis resistance, thereby to improve physico-chemical
properties of the fibre, to obtain polyester fibre with high degree of polymerization, to
increase greatly thermal stability of polyester fibres.
Thermal stability of PETP may be achieved by decreasing end carboxyl groups up to
≤
15 g-ekv/10
6
at the expense of interaction of compounds 1 and 2 with end - COOH groups
of polymer:
O
C
O
C
O
C
(2)
CH CH CH N R N CH CH CH
CH CH CH N N CH CH CH
O
(1)
2
2
2
2
2
2
2
2
R
O
O
C
O
C
O
O
It is noted here that modified fibres conserve up to 81% of strength at thermal treatment
up to 290
0
C, whereas this value in unmodified fibre is 60% [251-252].
PETP with increased resistance to thermal destruction [253] is obtained in the presence of
diglycol phosphate, igranox 1222 and trimethylborate.
Effective stabilizers of PETP are derivatives of phosphoric acid [254, 255], borites,
containing naphthyl and p - hydroxyl phenyl groups [256], zink propyl diphosphat, amide of
salicylic acid, derivative of pyrimidine and 4,6 ditredbutylene phenol [255], compounds
containing phosphorus [257].
Sulphide derivatives of polychlorperidines of general formula ASR, where A-C
6
Cl
6
, R-H,
CH
2
CH
2
O, CH
2
C(Cl)HCH
3
[258] are suggested as thermostabilizing and structure-forming
additive for PETP.
Important factor is the amount of introducing stabilizer. High stabilizing efficiency is
achieved by introducing stabilizer in the quantity of 0,05% of the polymer mass [259].
Effect of thermostabilizers on the polymer properties was studied by different physico-
chemical methods. For example, in the work [260] method of DSS (differential spectroscopy)
was used to define the effect of polyester-imide on thermo-physical properties of PETP. By
this method it was found out that polyester-imide reduces PETP ability to crystallization.
Methods of thermogravimetric analysis (TGA) and infrared spectroscopy in the nitrogen
atmosphere were used in the work [261] to define thermal stability of the mixture of PETP
and polyamide with the additive - modifier - polyethylene. It has been found that introduction
of the additive decreases activation energy which positively tells on the ability of PETP to
thermal destruction.
The task of light stabilization is the increase of light stability of polymer materials in the
process of photooxidative ageing. Different light stabilizers are used to execute this task.
Phototransformation of polymers is, in general case, complex multistage process. Ultra-
violet absorbers, ultra-violet shields, suppressors of excited states, inhibitors-acceptors of
radicals and inhibitors, destroying products, in which photobranching takes place, are used to
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