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In this paper, tiny amount of methacryloxyethyl trimethylammonium chloride (DMC) was added in poly(vinyl alcohol) (PVA) in order to widen its thermoplastic processing window. The effects of DMC content on thermal, mechanical, optical, and water resistance were investigated. The results showed that the thermal stability of PVA/DMC was improved obviously. Compared with pure PVA, with tiny amount (∼0.6 wt%) of DMC, the initial decomposition temperature and the fastest decomposition temperature of DMC/PVA increased from 246 °C and 287.6 °C–320.8 °C and 364.8 °C respectively. Moreover, this tiny amount of DMC did not affect the crystallization performance of PVA. PVA/DMC (0.6 wt%) blend have similar mechanical, optical properties and low temperature water resistance as those pure PVA have. The melting temperature of the PVA/DMC remained at 221 °C as that of pure PVA. This work might provide a new method for widening the thermoplastic processing window of PVA without sacrificing its other inherent properties. The reasons why DMC could improve the thermal stability for PVA was explored as well.

The elastic modulus and hardness of lithium niobate crystals were obtained by nanoindentation technology, and critical load and critical indentation depth range were determined by AFM by indentation morphology under different loads. According to the normal distribution characteristics of abrasive grains, the critical load model of lapping was deduced, and the critical load of lithium niobate during lapping process under different grain sizes was obtained. It was verified using a single-factor experiment in which experimental results were consistent with theoretical research.